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[linux-2.6.git] / fs / ext4 / inode.c
1 /*
2  *  linux/fs/ext4/inode.c
3  *
4  * Copyright (C) 1992, 1993, 1994, 1995
5  * Remy Card (card@masi.ibp.fr)
6  * Laboratoire MASI - Institut Blaise Pascal
7  * Universite Pierre et Marie Curie (Paris VI)
8  *
9  *  from
10  *
11  *  linux/fs/minix/inode.c
12  *
13  *  Copyright (C) 1991, 1992  Linus Torvalds
14  *
15  *  Goal-directed block allocation by Stephen Tweedie
16  *      (sct@redhat.com), 1993, 1998
17  *  Big-endian to little-endian byte-swapping/bitmaps by
18  *        David S. Miller (davem@caip.rutgers.edu), 1995
19  *  64-bit file support on 64-bit platforms by Jakub Jelinek
20  *      (jj@sunsite.ms.mff.cuni.cz)
21  *
22  *  Assorted race fixes, rewrite of ext4_get_block() by Al Viro, 2000
23  */
24
25 #include <linux/module.h>
26 #include <linux/fs.h>
27 #include <linux/time.h>
28 #include <linux/jbd2.h>
29 #include <linux/highuid.h>
30 #include <linux/pagemap.h>
31 #include <linux/quotaops.h>
32 #include <linux/string.h>
33 #include <linux/buffer_head.h>
34 #include <linux/writeback.h>
35 #include <linux/pagevec.h>
36 #include <linux/mpage.h>
37 #include <linux/namei.h>
38 #include <linux/uio.h>
39 #include <linux/bio.h>
40
41 #include "ext4_jbd2.h"
42 #include "xattr.h"
43 #include "acl.h"
44 #include "ext4_extents.h"
45
46 #include <trace/events/ext4.h>
47
48 #define MPAGE_DA_EXTENT_TAIL 0x01
49
50 static inline int ext4_begin_ordered_truncate(struct inode *inode,
51                                               loff_t new_size)
52 {
53         return jbd2_journal_begin_ordered_truncate(
54                                         EXT4_SB(inode->i_sb)->s_journal,
55                                         &EXT4_I(inode)->jinode,
56                                         new_size);
57 }
58
59 static void ext4_invalidatepage(struct page *page, unsigned long offset);
60
61 /*
62  * Test whether an inode is a fast symlink.
63  */
64 static int ext4_inode_is_fast_symlink(struct inode *inode)
65 {
66         int ea_blocks = EXT4_I(inode)->i_file_acl ?
67                 (inode->i_sb->s_blocksize >> 9) : 0;
68
69         return (S_ISLNK(inode->i_mode) && inode->i_blocks - ea_blocks == 0);
70 }
71
72 /*
73  * The ext4 forget function must perform a revoke if we are freeing data
74  * which has been journaled.  Metadata (eg. indirect blocks) must be
75  * revoked in all cases.
76  *
77  * "bh" may be NULL: a metadata block may have been freed from memory
78  * but there may still be a record of it in the journal, and that record
79  * still needs to be revoked.
80  *
81  * If the handle isn't valid we're not journaling, but we still need to
82  * call into ext4_journal_revoke() to put the buffer head.
83  */
84 int ext4_forget(handle_t *handle, int is_metadata, struct inode *inode,
85                 struct buffer_head *bh, ext4_fsblk_t blocknr)
86 {
87         int err;
88
89         might_sleep();
90
91         BUFFER_TRACE(bh, "enter");
92
93         jbd_debug(4, "forgetting bh %p: is_metadata = %d, mode %o, "
94                   "data mode %x\n",
95                   bh, is_metadata, inode->i_mode,
96                   test_opt(inode->i_sb, DATA_FLAGS));
97
98         /* Never use the revoke function if we are doing full data
99          * journaling: there is no need to, and a V1 superblock won't
100          * support it.  Otherwise, only skip the revoke on un-journaled
101          * data blocks. */
102
103         if (test_opt(inode->i_sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA ||
104             (!is_metadata && !ext4_should_journal_data(inode))) {
105                 if (bh) {
106                         BUFFER_TRACE(bh, "call jbd2_journal_forget");
107                         return ext4_journal_forget(handle, bh);
108                 }
109                 return 0;
110         }
111
112         /*
113          * data!=journal && (is_metadata || should_journal_data(inode))
114          */
115         BUFFER_TRACE(bh, "call ext4_journal_revoke");
116         err = ext4_journal_revoke(handle, blocknr, bh);
117         if (err)
118                 ext4_abort(inode->i_sb, __func__,
119                            "error %d when attempting revoke", err);
120         BUFFER_TRACE(bh, "exit");
121         return err;
122 }
123
124 /*
125  * Work out how many blocks we need to proceed with the next chunk of a
126  * truncate transaction.
127  */
128 static unsigned long blocks_for_truncate(struct inode *inode)
129 {
130         ext4_lblk_t needed;
131
132         needed = inode->i_blocks >> (inode->i_sb->s_blocksize_bits - 9);
133
134         /* Give ourselves just enough room to cope with inodes in which
135          * i_blocks is corrupt: we've seen disk corruptions in the past
136          * which resulted in random data in an inode which looked enough
137          * like a regular file for ext4 to try to delete it.  Things
138          * will go a bit crazy if that happens, but at least we should
139          * try not to panic the whole kernel. */
140         if (needed < 2)
141                 needed = 2;
142
143         /* But we need to bound the transaction so we don't overflow the
144          * journal. */
145         if (needed > EXT4_MAX_TRANS_DATA)
146                 needed = EXT4_MAX_TRANS_DATA;
147
148         return EXT4_DATA_TRANS_BLOCKS(inode->i_sb) + needed;
149 }
150
151 /*
152  * Truncate transactions can be complex and absolutely huge.  So we need to
153  * be able to restart the transaction at a conventient checkpoint to make
154  * sure we don't overflow the journal.
155  *
156  * start_transaction gets us a new handle for a truncate transaction,
157  * and extend_transaction tries to extend the existing one a bit.  If
158  * extend fails, we need to propagate the failure up and restart the
159  * transaction in the top-level truncate loop. --sct
160  */
161 static handle_t *start_transaction(struct inode *inode)
162 {
163         handle_t *result;
164
165         result = ext4_journal_start(inode, blocks_for_truncate(inode));
166         if (!IS_ERR(result))
167                 return result;
168
169         ext4_std_error(inode->i_sb, PTR_ERR(result));
170         return result;
171 }
172
173 /*
174  * Try to extend this transaction for the purposes of truncation.
175  *
176  * Returns 0 if we managed to create more room.  If we can't create more
177  * room, and the transaction must be restarted we return 1.
178  */
179 static int try_to_extend_transaction(handle_t *handle, struct inode *inode)
180 {
181         if (!ext4_handle_valid(handle))
182                 return 0;
183         if (ext4_handle_has_enough_credits(handle, EXT4_RESERVE_TRANS_BLOCKS+1))
184                 return 0;
185         if (!ext4_journal_extend(handle, blocks_for_truncate(inode)))
186                 return 0;
187         return 1;
188 }
189
190 /*
191  * Restart the transaction associated with *handle.  This does a commit,
192  * so before we call here everything must be consistently dirtied against
193  * this transaction.
194  */
195  int ext4_truncate_restart_trans(handle_t *handle, struct inode *inode,
196                                  int nblocks)
197 {
198         int ret;
199
200         /*
201          * Drop i_data_sem to avoid deadlock with ext4_get_blocks At this
202          * moment, get_block can be called only for blocks inside i_size since
203          * page cache has been already dropped and writes are blocked by
204          * i_mutex. So we can safely drop the i_data_sem here.
205          */
206         BUG_ON(EXT4_JOURNAL(inode) == NULL);
207         jbd_debug(2, "restarting handle %p\n", handle);
208         up_write(&EXT4_I(inode)->i_data_sem);
209         ret = ext4_journal_restart(handle, blocks_for_truncate(inode));
210         down_write(&EXT4_I(inode)->i_data_sem);
211
212         return ret;
213 }
214
215 /*
216  * Called at the last iput() if i_nlink is zero.
217  */
218 void ext4_delete_inode(struct inode *inode)
219 {
220         handle_t *handle;
221         int err;
222
223         if (ext4_should_order_data(inode))
224                 ext4_begin_ordered_truncate(inode, 0);
225         truncate_inode_pages(&inode->i_data, 0);
226
227         if (is_bad_inode(inode))
228                 goto no_delete;
229
230         handle = ext4_journal_start(inode, blocks_for_truncate(inode)+3);
231         if (IS_ERR(handle)) {
232                 ext4_std_error(inode->i_sb, PTR_ERR(handle));
233                 /*
234                  * If we're going to skip the normal cleanup, we still need to
235                  * make sure that the in-core orphan linked list is properly
236                  * cleaned up.
237                  */
238                 ext4_orphan_del(NULL, inode);
239                 goto no_delete;
240         }
241
242         if (IS_SYNC(inode))
243                 ext4_handle_sync(handle);
244         inode->i_size = 0;
245         err = ext4_mark_inode_dirty(handle, inode);
246         if (err) {
247                 ext4_warning(inode->i_sb, __func__,
248                              "couldn't mark inode dirty (err %d)", err);
249                 goto stop_handle;
250         }
251         if (inode->i_blocks)
252                 ext4_truncate(inode);
253
254         /*
255          * ext4_ext_truncate() doesn't reserve any slop when it
256          * restarts journal transactions; therefore there may not be
257          * enough credits left in the handle to remove the inode from
258          * the orphan list and set the dtime field.
259          */
260         if (!ext4_handle_has_enough_credits(handle, 3)) {
261                 err = ext4_journal_extend(handle, 3);
262                 if (err > 0)
263                         err = ext4_journal_restart(handle, 3);
264                 if (err != 0) {
265                         ext4_warning(inode->i_sb, __func__,
266                                      "couldn't extend journal (err %d)", err);
267                 stop_handle:
268                         ext4_journal_stop(handle);
269                         goto no_delete;
270                 }
271         }
272
273         /*
274          * Kill off the orphan record which ext4_truncate created.
275          * AKPM: I think this can be inside the above `if'.
276          * Note that ext4_orphan_del() has to be able to cope with the
277          * deletion of a non-existent orphan - this is because we don't
278          * know if ext4_truncate() actually created an orphan record.
279          * (Well, we could do this if we need to, but heck - it works)
280          */
281         ext4_orphan_del(handle, inode);
282         EXT4_I(inode)->i_dtime  = get_seconds();
283
284         /*
285          * One subtle ordering requirement: if anything has gone wrong
286          * (transaction abort, IO errors, whatever), then we can still
287          * do these next steps (the fs will already have been marked as
288          * having errors), but we can't free the inode if the mark_dirty
289          * fails.
290          */
291         if (ext4_mark_inode_dirty(handle, inode))
292                 /* If that failed, just do the required in-core inode clear. */
293                 clear_inode(inode);
294         else
295                 ext4_free_inode(handle, inode);
296         ext4_journal_stop(handle);
297         return;
298 no_delete:
299         clear_inode(inode);     /* We must guarantee clearing of inode... */
300 }
301
302 typedef struct {
303         __le32  *p;
304         __le32  key;
305         struct buffer_head *bh;
306 } Indirect;
307
308 static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
309 {
310         p->key = *(p->p = v);
311         p->bh = bh;
312 }
313
314 /**
315  *      ext4_block_to_path - parse the block number into array of offsets
316  *      @inode: inode in question (we are only interested in its superblock)
317  *      @i_block: block number to be parsed
318  *      @offsets: array to store the offsets in
319  *      @boundary: set this non-zero if the referred-to block is likely to be
320  *             followed (on disk) by an indirect block.
321  *
322  *      To store the locations of file's data ext4 uses a data structure common
323  *      for UNIX filesystems - tree of pointers anchored in the inode, with
324  *      data blocks at leaves and indirect blocks in intermediate nodes.
325  *      This function translates the block number into path in that tree -
326  *      return value is the path length and @offsets[n] is the offset of
327  *      pointer to (n+1)th node in the nth one. If @block is out of range
328  *      (negative or too large) warning is printed and zero returned.
329  *
330  *      Note: function doesn't find node addresses, so no IO is needed. All
331  *      we need to know is the capacity of indirect blocks (taken from the
332  *      inode->i_sb).
333  */
334
335 /*
336  * Portability note: the last comparison (check that we fit into triple
337  * indirect block) is spelled differently, because otherwise on an
338  * architecture with 32-bit longs and 8Kb pages we might get into trouble
339  * if our filesystem had 8Kb blocks. We might use long long, but that would
340  * kill us on x86. Oh, well, at least the sign propagation does not matter -
341  * i_block would have to be negative in the very beginning, so we would not
342  * get there at all.
343  */
344
345 static int ext4_block_to_path(struct inode *inode,
346                               ext4_lblk_t i_block,
347                               ext4_lblk_t offsets[4], int *boundary)
348 {
349         int ptrs = EXT4_ADDR_PER_BLOCK(inode->i_sb);
350         int ptrs_bits = EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb);
351         const long direct_blocks = EXT4_NDIR_BLOCKS,
352                 indirect_blocks = ptrs,
353                 double_blocks = (1 << (ptrs_bits * 2));
354         int n = 0;
355         int final = 0;
356
357         if (i_block < direct_blocks) {
358                 offsets[n++] = i_block;
359                 final = direct_blocks;
360         } else if ((i_block -= direct_blocks) < indirect_blocks) {
361                 offsets[n++] = EXT4_IND_BLOCK;
362                 offsets[n++] = i_block;
363                 final = ptrs;
364         } else if ((i_block -= indirect_blocks) < double_blocks) {
365                 offsets[n++] = EXT4_DIND_BLOCK;
366                 offsets[n++] = i_block >> ptrs_bits;
367                 offsets[n++] = i_block & (ptrs - 1);
368                 final = ptrs;
369         } else if (((i_block -= double_blocks) >> (ptrs_bits * 2)) < ptrs) {
370                 offsets[n++] = EXT4_TIND_BLOCK;
371                 offsets[n++] = i_block >> (ptrs_bits * 2);
372                 offsets[n++] = (i_block >> ptrs_bits) & (ptrs - 1);
373                 offsets[n++] = i_block & (ptrs - 1);
374                 final = ptrs;
375         } else {
376                 ext4_warning(inode->i_sb, "ext4_block_to_path",
377                              "block %lu > max in inode %lu",
378                              i_block + direct_blocks +
379                              indirect_blocks + double_blocks, inode->i_ino);
380         }
381         if (boundary)
382                 *boundary = final - 1 - (i_block & (ptrs - 1));
383         return n;
384 }
385
386 static int __ext4_check_blockref(const char *function, struct inode *inode,
387                                  __le32 *p, unsigned int max)
388 {
389         __le32 *bref = p;
390         unsigned int blk;
391
392         while (bref < p+max) {
393                 blk = le32_to_cpu(*bref++);
394                 if (blk &&
395                     unlikely(!ext4_data_block_valid(EXT4_SB(inode->i_sb),
396                                                     blk, 1))) {
397                         ext4_error(inode->i_sb, function,
398                                    "invalid block reference %u "
399                                    "in inode #%lu", blk, inode->i_ino);
400                         return -EIO;
401                 }
402         }
403         return 0;
404 }
405
406
407 #define ext4_check_indirect_blockref(inode, bh)                         \
408         __ext4_check_blockref(__func__, inode, (__le32 *)(bh)->b_data,  \
409                               EXT4_ADDR_PER_BLOCK((inode)->i_sb))
410
411 #define ext4_check_inode_blockref(inode)                                \
412         __ext4_check_blockref(__func__, inode, EXT4_I(inode)->i_data,   \
413                               EXT4_NDIR_BLOCKS)
414
415 /**
416  *      ext4_get_branch - read the chain of indirect blocks leading to data
417  *      @inode: inode in question
418  *      @depth: depth of the chain (1 - direct pointer, etc.)
419  *      @offsets: offsets of pointers in inode/indirect blocks
420  *      @chain: place to store the result
421  *      @err: here we store the error value
422  *
423  *      Function fills the array of triples <key, p, bh> and returns %NULL
424  *      if everything went OK or the pointer to the last filled triple
425  *      (incomplete one) otherwise. Upon the return chain[i].key contains
426  *      the number of (i+1)-th block in the chain (as it is stored in memory,
427  *      i.e. little-endian 32-bit), chain[i].p contains the address of that
428  *      number (it points into struct inode for i==0 and into the bh->b_data
429  *      for i>0) and chain[i].bh points to the buffer_head of i-th indirect
430  *      block for i>0 and NULL for i==0. In other words, it holds the block
431  *      numbers of the chain, addresses they were taken from (and where we can
432  *      verify that chain did not change) and buffer_heads hosting these
433  *      numbers.
434  *
435  *      Function stops when it stumbles upon zero pointer (absent block)
436  *              (pointer to last triple returned, *@err == 0)
437  *      or when it gets an IO error reading an indirect block
438  *              (ditto, *@err == -EIO)
439  *      or when it reads all @depth-1 indirect blocks successfully and finds
440  *      the whole chain, all way to the data (returns %NULL, *err == 0).
441  *
442  *      Need to be called with
443  *      down_read(&EXT4_I(inode)->i_data_sem)
444  */
445 static Indirect *ext4_get_branch(struct inode *inode, int depth,
446                                  ext4_lblk_t  *offsets,
447                                  Indirect chain[4], int *err)
448 {
449         struct super_block *sb = inode->i_sb;
450         Indirect *p = chain;
451         struct buffer_head *bh;
452
453         *err = 0;
454         /* i_data is not going away, no lock needed */
455         add_chain(chain, NULL, EXT4_I(inode)->i_data + *offsets);
456         if (!p->key)
457                 goto no_block;
458         while (--depth) {
459                 bh = sb_getblk(sb, le32_to_cpu(p->key));
460                 if (unlikely(!bh))
461                         goto failure;
462
463                 if (!bh_uptodate_or_lock(bh)) {
464                         if (bh_submit_read(bh) < 0) {
465                                 put_bh(bh);
466                                 goto failure;
467                         }
468                         /* validate block references */
469                         if (ext4_check_indirect_blockref(inode, bh)) {
470                                 put_bh(bh);
471                                 goto failure;
472                         }
473                 }
474
475                 add_chain(++p, bh, (__le32 *)bh->b_data + *++offsets);
476                 /* Reader: end */
477                 if (!p->key)
478                         goto no_block;
479         }
480         return NULL;
481
482 failure:
483         *err = -EIO;
484 no_block:
485         return p;
486 }
487
488 /**
489  *      ext4_find_near - find a place for allocation with sufficient locality
490  *      @inode: owner
491  *      @ind: descriptor of indirect block.
492  *
493  *      This function returns the preferred place for block allocation.
494  *      It is used when heuristic for sequential allocation fails.
495  *      Rules are:
496  *        + if there is a block to the left of our position - allocate near it.
497  *        + if pointer will live in indirect block - allocate near that block.
498  *        + if pointer will live in inode - allocate in the same
499  *          cylinder group.
500  *
501  * In the latter case we colour the starting block by the callers PID to
502  * prevent it from clashing with concurrent allocations for a different inode
503  * in the same block group.   The PID is used here so that functionally related
504  * files will be close-by on-disk.
505  *
506  *      Caller must make sure that @ind is valid and will stay that way.
507  */
508 static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
509 {
510         struct ext4_inode_info *ei = EXT4_I(inode);
511         __le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
512         __le32 *p;
513         ext4_fsblk_t bg_start;
514         ext4_fsblk_t last_block;
515         ext4_grpblk_t colour;
516         ext4_group_t block_group;
517         int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
518
519         /* Try to find previous block */
520         for (p = ind->p - 1; p >= start; p--) {
521                 if (*p)
522                         return le32_to_cpu(*p);
523         }
524
525         /* No such thing, so let's try location of indirect block */
526         if (ind->bh)
527                 return ind->bh->b_blocknr;
528
529         /*
530          * It is going to be referred to from the inode itself? OK, just put it
531          * into the same cylinder group then.
532          */
533         block_group = ei->i_block_group;
534         if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
535                 block_group &= ~(flex_size-1);
536                 if (S_ISREG(inode->i_mode))
537                         block_group++;
538         }
539         bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
540         last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
541
542         /*
543          * If we are doing delayed allocation, we don't need take
544          * colour into account.
545          */
546         if (test_opt(inode->i_sb, DELALLOC))
547                 return bg_start;
548
549         if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
550                 colour = (current->pid % 16) *
551                         (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
552         else
553                 colour = (current->pid % 16) * ((last_block - bg_start) / 16);
554         return bg_start + colour;
555 }
556
557 /**
558  *      ext4_find_goal - find a preferred place for allocation.
559  *      @inode: owner
560  *      @block:  block we want
561  *      @partial: pointer to the last triple within a chain
562  *
563  *      Normally this function find the preferred place for block allocation,
564  *      returns it.
565  *      Because this is only used for non-extent files, we limit the block nr
566  *      to 32 bits.
567  */
568 static ext4_fsblk_t ext4_find_goal(struct inode *inode, ext4_lblk_t block,
569                                    Indirect *partial)
570 {
571         ext4_fsblk_t goal;
572
573         /*
574          * XXX need to get goal block from mballoc's data structures
575          */
576
577         goal = ext4_find_near(inode, partial);
578         goal = goal & EXT4_MAX_BLOCK_FILE_PHYS;
579         return goal;
580 }
581
582 /**
583  *      ext4_blks_to_allocate: Look up the block map and count the number
584  *      of direct blocks need to be allocated for the given branch.
585  *
586  *      @branch: chain of indirect blocks
587  *      @k: number of blocks need for indirect blocks
588  *      @blks: number of data blocks to be mapped.
589  *      @blocks_to_boundary:  the offset in the indirect block
590  *
591  *      return the total number of blocks to be allocate, including the
592  *      direct and indirect blocks.
593  */
594 static int ext4_blks_to_allocate(Indirect *branch, int k, unsigned int blks,
595                                  int blocks_to_boundary)
596 {
597         unsigned int count = 0;
598
599         /*
600          * Simple case, [t,d]Indirect block(s) has not allocated yet
601          * then it's clear blocks on that path have not allocated
602          */
603         if (k > 0) {
604                 /* right now we don't handle cross boundary allocation */
605                 if (blks < blocks_to_boundary + 1)
606                         count += blks;
607                 else
608                         count += blocks_to_boundary + 1;
609                 return count;
610         }
611
612         count++;
613         while (count < blks && count <= blocks_to_boundary &&
614                 le32_to_cpu(*(branch[0].p + count)) == 0) {
615                 count++;
616         }
617         return count;
618 }
619
620 /**
621  *      ext4_alloc_blocks: multiple allocate blocks needed for a branch
622  *      @indirect_blks: the number of blocks need to allocate for indirect
623  *                      blocks
624  *
625  *      @new_blocks: on return it will store the new block numbers for
626  *      the indirect blocks(if needed) and the first direct block,
627  *      @blks:  on return it will store the total number of allocated
628  *              direct blocks
629  */
630 static int ext4_alloc_blocks(handle_t *handle, struct inode *inode,
631                              ext4_lblk_t iblock, ext4_fsblk_t goal,
632                              int indirect_blks, int blks,
633                              ext4_fsblk_t new_blocks[4], int *err)
634 {
635         struct ext4_allocation_request ar;
636         int target, i;
637         unsigned long count = 0, blk_allocated = 0;
638         int index = 0;
639         ext4_fsblk_t current_block = 0;
640         int ret = 0;
641
642         /*
643          * Here we try to allocate the requested multiple blocks at once,
644          * on a best-effort basis.
645          * To build a branch, we should allocate blocks for
646          * the indirect blocks(if not allocated yet), and at least
647          * the first direct block of this branch.  That's the
648          * minimum number of blocks need to allocate(required)
649          */
650         /* first we try to allocate the indirect blocks */
651         target = indirect_blks;
652         while (target > 0) {
653                 count = target;
654                 /* allocating blocks for indirect blocks and direct blocks */
655                 current_block = ext4_new_meta_blocks(handle, inode,
656                                                         goal, &count, err);
657                 if (*err)
658                         goto failed_out;
659
660                 BUG_ON(current_block + count > EXT4_MAX_BLOCK_FILE_PHYS);
661
662                 target -= count;
663                 /* allocate blocks for indirect blocks */
664                 while (index < indirect_blks && count) {
665                         new_blocks[index++] = current_block++;
666                         count--;
667                 }
668                 if (count > 0) {
669                         /*
670                          * save the new block number
671                          * for the first direct block
672                          */
673                         new_blocks[index] = current_block;
674                         printk(KERN_INFO "%s returned more blocks than "
675                                                 "requested\n", __func__);
676                         WARN_ON(1);
677                         break;
678                 }
679         }
680
681         target = blks - count ;
682         blk_allocated = count;
683         if (!target)
684                 goto allocated;
685         /* Now allocate data blocks */
686         memset(&ar, 0, sizeof(ar));
687         ar.inode = inode;
688         ar.goal = goal;
689         ar.len = target;
690         ar.logical = iblock;
691         if (S_ISREG(inode->i_mode))
692                 /* enable in-core preallocation only for regular files */
693                 ar.flags = EXT4_MB_HINT_DATA;
694
695         current_block = ext4_mb_new_blocks(handle, &ar, err);
696         BUG_ON(current_block + ar.len > EXT4_MAX_BLOCK_FILE_PHYS);
697
698         if (*err && (target == blks)) {
699                 /*
700                  * if the allocation failed and we didn't allocate
701                  * any blocks before
702                  */
703                 goto failed_out;
704         }
705         if (!*err) {
706                 if (target == blks) {
707                         /*
708                          * save the new block number
709                          * for the first direct block
710                          */
711                         new_blocks[index] = current_block;
712                 }
713                 blk_allocated += ar.len;
714         }
715 allocated:
716         /* total number of blocks allocated for direct blocks */
717         ret = blk_allocated;
718         *err = 0;
719         return ret;
720 failed_out:
721         for (i = 0; i < index; i++)
722                 ext4_free_blocks(handle, inode, new_blocks[i], 1, 0);
723         return ret;
724 }
725
726 /**
727  *      ext4_alloc_branch - allocate and set up a chain of blocks.
728  *      @inode: owner
729  *      @indirect_blks: number of allocated indirect blocks
730  *      @blks: number of allocated direct blocks
731  *      @offsets: offsets (in the blocks) to store the pointers to next.
732  *      @branch: place to store the chain in.
733  *
734  *      This function allocates blocks, zeroes out all but the last one,
735  *      links them into chain and (if we are synchronous) writes them to disk.
736  *      In other words, it prepares a branch that can be spliced onto the
737  *      inode. It stores the information about that chain in the branch[], in
738  *      the same format as ext4_get_branch() would do. We are calling it after
739  *      we had read the existing part of chain and partial points to the last
740  *      triple of that (one with zero ->key). Upon the exit we have the same
741  *      picture as after the successful ext4_get_block(), except that in one
742  *      place chain is disconnected - *branch->p is still zero (we did not
743  *      set the last link), but branch->key contains the number that should
744  *      be placed into *branch->p to fill that gap.
745  *
746  *      If allocation fails we free all blocks we've allocated (and forget
747  *      their buffer_heads) and return the error value the from failed
748  *      ext4_alloc_block() (normally -ENOSPC). Otherwise we set the chain
749  *      as described above and return 0.
750  */
751 static int ext4_alloc_branch(handle_t *handle, struct inode *inode,
752                              ext4_lblk_t iblock, int indirect_blks,
753                              int *blks, ext4_fsblk_t goal,
754                              ext4_lblk_t *offsets, Indirect *branch)
755 {
756         int blocksize = inode->i_sb->s_blocksize;
757         int i, n = 0;
758         int err = 0;
759         struct buffer_head *bh;
760         int num;
761         ext4_fsblk_t new_blocks[4];
762         ext4_fsblk_t current_block;
763
764         num = ext4_alloc_blocks(handle, inode, iblock, goal, indirect_blks,
765                                 *blks, new_blocks, &err);
766         if (err)
767                 return err;
768
769         branch[0].key = cpu_to_le32(new_blocks[0]);
770         /*
771          * metadata blocks and data blocks are allocated.
772          */
773         for (n = 1; n <= indirect_blks;  n++) {
774                 /*
775                  * Get buffer_head for parent block, zero it out
776                  * and set the pointer to new one, then send
777                  * parent to disk.
778                  */
779                 bh = sb_getblk(inode->i_sb, new_blocks[n-1]);
780                 branch[n].bh = bh;
781                 lock_buffer(bh);
782                 BUFFER_TRACE(bh, "call get_create_access");
783                 err = ext4_journal_get_create_access(handle, bh);
784                 if (err) {
785                         /* Don't brelse(bh) here; it's done in
786                          * ext4_journal_forget() below */
787                         unlock_buffer(bh);
788                         goto failed;
789                 }
790
791                 memset(bh->b_data, 0, blocksize);
792                 branch[n].p = (__le32 *) bh->b_data + offsets[n];
793                 branch[n].key = cpu_to_le32(new_blocks[n]);
794                 *branch[n].p = branch[n].key;
795                 if (n == indirect_blks) {
796                         current_block = new_blocks[n];
797                         /*
798                          * End of chain, update the last new metablock of
799                          * the chain to point to the new allocated
800                          * data blocks numbers
801                          */
802                         for (i = 1; i < num; i++)
803                                 *(branch[n].p + i) = cpu_to_le32(++current_block);
804                 }
805                 BUFFER_TRACE(bh, "marking uptodate");
806                 set_buffer_uptodate(bh);
807                 unlock_buffer(bh);
808
809                 BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
810                 err = ext4_handle_dirty_metadata(handle, inode, bh);
811                 if (err)
812                         goto failed;
813         }
814         *blks = num;
815         return err;
816 failed:
817         /* Allocation failed, free what we already allocated */
818         for (i = 1; i <= n ; i++) {
819                 BUFFER_TRACE(branch[i].bh, "call jbd2_journal_forget");
820                 ext4_journal_forget(handle, branch[i].bh);
821         }
822         for (i = 0; i < indirect_blks; i++)
823                 ext4_free_blocks(handle, inode, new_blocks[i], 1, 0);
824
825         ext4_free_blocks(handle, inode, new_blocks[i], num, 0);
826
827         return err;
828 }
829
830 /**
831  * ext4_splice_branch - splice the allocated branch onto inode.
832  * @inode: owner
833  * @block: (logical) number of block we are adding
834  * @chain: chain of indirect blocks (with a missing link - see
835  *      ext4_alloc_branch)
836  * @where: location of missing link
837  * @num:   number of indirect blocks we are adding
838  * @blks:  number of direct blocks we are adding
839  *
840  * This function fills the missing link and does all housekeeping needed in
841  * inode (->i_blocks, etc.). In case of success we end up with the full
842  * chain to new block and return 0.
843  */
844 static int ext4_splice_branch(handle_t *handle, struct inode *inode,
845                               ext4_lblk_t block, Indirect *where, int num,
846                               int blks)
847 {
848         int i;
849         int err = 0;
850         ext4_fsblk_t current_block;
851
852         /*
853          * If we're splicing into a [td]indirect block (as opposed to the
854          * inode) then we need to get write access to the [td]indirect block
855          * before the splice.
856          */
857         if (where->bh) {
858                 BUFFER_TRACE(where->bh, "get_write_access");
859                 err = ext4_journal_get_write_access(handle, where->bh);
860                 if (err)
861                         goto err_out;
862         }
863         /* That's it */
864
865         *where->p = where->key;
866
867         /*
868          * Update the host buffer_head or inode to point to more just allocated
869          * direct blocks blocks
870          */
871         if (num == 0 && blks > 1) {
872                 current_block = le32_to_cpu(where->key) + 1;
873                 for (i = 1; i < blks; i++)
874                         *(where->p + i) = cpu_to_le32(current_block++);
875         }
876
877         /* We are done with atomic stuff, now do the rest of housekeeping */
878         /* had we spliced it onto indirect block? */
879         if (where->bh) {
880                 /*
881                  * If we spliced it onto an indirect block, we haven't
882                  * altered the inode.  Note however that if it is being spliced
883                  * onto an indirect block at the very end of the file (the
884                  * file is growing) then we *will* alter the inode to reflect
885                  * the new i_size.  But that is not done here - it is done in
886                  * generic_commit_write->__mark_inode_dirty->ext4_dirty_inode.
887                  */
888                 jbd_debug(5, "splicing indirect only\n");
889                 BUFFER_TRACE(where->bh, "call ext4_handle_dirty_metadata");
890                 err = ext4_handle_dirty_metadata(handle, inode, where->bh);
891                 if (err)
892                         goto err_out;
893         } else {
894                 /*
895                  * OK, we spliced it into the inode itself on a direct block.
896                  */
897                 ext4_mark_inode_dirty(handle, inode);
898                 jbd_debug(5, "splicing direct\n");
899         }
900         return err;
901
902 err_out:
903         for (i = 1; i <= num; i++) {
904                 BUFFER_TRACE(where[i].bh, "call jbd2_journal_forget");
905                 ext4_journal_forget(handle, where[i].bh);
906                 ext4_free_blocks(handle, inode,
907                                         le32_to_cpu(where[i-1].key), 1, 0);
908         }
909         ext4_free_blocks(handle, inode, le32_to_cpu(where[num].key), blks, 0);
910
911         return err;
912 }
913
914 /*
915  * The ext4_ind_get_blocks() function handles non-extents inodes
916  * (i.e., using the traditional indirect/double-indirect i_blocks
917  * scheme) for ext4_get_blocks().
918  *
919  * Allocation strategy is simple: if we have to allocate something, we will
920  * have to go the whole way to leaf. So let's do it before attaching anything
921  * to tree, set linkage between the newborn blocks, write them if sync is
922  * required, recheck the path, free and repeat if check fails, otherwise
923  * set the last missing link (that will protect us from any truncate-generated
924  * removals - all blocks on the path are immune now) and possibly force the
925  * write on the parent block.
926  * That has a nice additional property: no special recovery from the failed
927  * allocations is needed - we simply release blocks and do not touch anything
928  * reachable from inode.
929  *
930  * `handle' can be NULL if create == 0.
931  *
932  * return > 0, # of blocks mapped or allocated.
933  * return = 0, if plain lookup failed.
934  * return < 0, error case.
935  *
936  * The ext4_ind_get_blocks() function should be called with
937  * down_write(&EXT4_I(inode)->i_data_sem) if allocating filesystem
938  * blocks (i.e., flags has EXT4_GET_BLOCKS_CREATE set) or
939  * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system
940  * blocks.
941  */
942 static int ext4_ind_get_blocks(handle_t *handle, struct inode *inode,
943                                ext4_lblk_t iblock, unsigned int maxblocks,
944                                struct buffer_head *bh_result,
945                                int flags)
946 {
947         int err = -EIO;
948         ext4_lblk_t offsets[4];
949         Indirect chain[4];
950         Indirect *partial;
951         ext4_fsblk_t goal;
952         int indirect_blks;
953         int blocks_to_boundary = 0;
954         int depth;
955         int count = 0;
956         ext4_fsblk_t first_block = 0;
957
958         J_ASSERT(!(EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL));
959         J_ASSERT(handle != NULL || (flags & EXT4_GET_BLOCKS_CREATE) == 0);
960         depth = ext4_block_to_path(inode, iblock, offsets,
961                                    &blocks_to_boundary);
962
963         if (depth == 0)
964                 goto out;
965
966         partial = ext4_get_branch(inode, depth, offsets, chain, &err);
967
968         /* Simplest case - block found, no allocation needed */
969         if (!partial) {
970                 first_block = le32_to_cpu(chain[depth - 1].key);
971                 clear_buffer_new(bh_result);
972                 count++;
973                 /*map more blocks*/
974                 while (count < maxblocks && count <= blocks_to_boundary) {
975                         ext4_fsblk_t blk;
976
977                         blk = le32_to_cpu(*(chain[depth-1].p + count));
978
979                         if (blk == first_block + count)
980                                 count++;
981                         else
982                                 break;
983                 }
984                 goto got_it;
985         }
986
987         /* Next simple case - plain lookup or failed read of indirect block */
988         if ((flags & EXT4_GET_BLOCKS_CREATE) == 0 || err == -EIO)
989                 goto cleanup;
990
991         /*
992          * Okay, we need to do block allocation.
993         */
994         goal = ext4_find_goal(inode, iblock, partial);
995
996         /* the number of blocks need to allocate for [d,t]indirect blocks */
997         indirect_blks = (chain + depth) - partial - 1;
998
999         /*
1000          * Next look up the indirect map to count the totoal number of
1001          * direct blocks to allocate for this branch.
1002          */
1003         count = ext4_blks_to_allocate(partial, indirect_blks,
1004                                         maxblocks, blocks_to_boundary);
1005         /*
1006          * Block out ext4_truncate while we alter the tree
1007          */
1008         err = ext4_alloc_branch(handle, inode, iblock, indirect_blks,
1009                                 &count, goal,
1010                                 offsets + (partial - chain), partial);
1011
1012         /*
1013          * The ext4_splice_branch call will free and forget any buffers
1014          * on the new chain if there is a failure, but that risks using
1015          * up transaction credits, especially for bitmaps where the
1016          * credits cannot be returned.  Can we handle this somehow?  We
1017          * may need to return -EAGAIN upwards in the worst case.  --sct
1018          */
1019         if (!err)
1020                 err = ext4_splice_branch(handle, inode, iblock,
1021                                          partial, indirect_blks, count);
1022         else
1023                 goto cleanup;
1024
1025         set_buffer_new(bh_result);
1026 got_it:
1027         map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
1028         if (count > blocks_to_boundary)
1029                 set_buffer_boundary(bh_result);
1030         err = count;
1031         /* Clean up and exit */
1032         partial = chain + depth - 1;    /* the whole chain */
1033 cleanup:
1034         while (partial > chain) {
1035                 BUFFER_TRACE(partial->bh, "call brelse");
1036                 brelse(partial->bh);
1037                 partial--;
1038         }
1039         BUFFER_TRACE(bh_result, "returned");
1040 out:
1041         return err;
1042 }
1043
1044 qsize_t ext4_get_reserved_space(struct inode *inode)
1045 {
1046         unsigned long long total;
1047
1048         spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
1049         total = EXT4_I(inode)->i_reserved_data_blocks +
1050                 EXT4_I(inode)->i_reserved_meta_blocks;
1051         spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1052
1053         return total;
1054 }
1055 /*
1056  * Calculate the number of metadata blocks need to reserve
1057  * to allocate @blocks for non extent file based file
1058  */
1059 static int ext4_indirect_calc_metadata_amount(struct inode *inode, int blocks)
1060 {
1061         int icap = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1062         int ind_blks, dind_blks, tind_blks;
1063
1064         /* number of new indirect blocks needed */
1065         ind_blks = (blocks + icap - 1) / icap;
1066
1067         dind_blks = (ind_blks + icap - 1) / icap;
1068
1069         tind_blks = 1;
1070
1071         return ind_blks + dind_blks + tind_blks;
1072 }
1073
1074 /*
1075  * Calculate the number of metadata blocks need to reserve
1076  * to allocate given number of blocks
1077  */
1078 static int ext4_calc_metadata_amount(struct inode *inode, int blocks)
1079 {
1080         if (!blocks)
1081                 return 0;
1082
1083         if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL)
1084                 return ext4_ext_calc_metadata_amount(inode, blocks);
1085
1086         return ext4_indirect_calc_metadata_amount(inode, blocks);
1087 }
1088
1089 static void ext4_da_update_reserve_space(struct inode *inode, int used)
1090 {
1091         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
1092         int total, mdb, mdb_free;
1093
1094         spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
1095         /* recalculate the number of metablocks still need to be reserved */
1096         total = EXT4_I(inode)->i_reserved_data_blocks - used;
1097         mdb = ext4_calc_metadata_amount(inode, total);
1098
1099         /* figure out how many metablocks to release */
1100         BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
1101         mdb_free = EXT4_I(inode)->i_reserved_meta_blocks - mdb;
1102
1103         if (mdb_free) {
1104                 /* Account for allocated meta_blocks */
1105                 mdb_free -= EXT4_I(inode)->i_allocated_meta_blocks;
1106
1107                 /* update fs dirty blocks counter */
1108                 percpu_counter_sub(&sbi->s_dirtyblocks_counter, mdb_free);
1109                 EXT4_I(inode)->i_allocated_meta_blocks = 0;
1110                 EXT4_I(inode)->i_reserved_meta_blocks = mdb;
1111         }
1112
1113         /* update per-inode reservations */
1114         BUG_ON(used  > EXT4_I(inode)->i_reserved_data_blocks);
1115         EXT4_I(inode)->i_reserved_data_blocks -= used;
1116         spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1117
1118         /*
1119          * free those over-booking quota for metadata blocks
1120          */
1121         if (mdb_free)
1122                 vfs_dq_release_reservation_block(inode, mdb_free);
1123
1124         /*
1125          * If we have done all the pending block allocations and if
1126          * there aren't any writers on the inode, we can discard the
1127          * inode's preallocations.
1128          */
1129         if (!total && (atomic_read(&inode->i_writecount) == 0))
1130                 ext4_discard_preallocations(inode);
1131 }
1132
1133 static int check_block_validity(struct inode *inode, const char *msg,
1134                                 sector_t logical, sector_t phys, int len)
1135 {
1136         if (!ext4_data_block_valid(EXT4_SB(inode->i_sb), phys, len)) {
1137                 ext4_error(inode->i_sb, msg,
1138                            "inode #%lu logical block %llu mapped to %llu "
1139                            "(size %d)", inode->i_ino,
1140                            (unsigned long long) logical,
1141                            (unsigned long long) phys, len);
1142                 return -EIO;
1143         }
1144         return 0;
1145 }
1146
1147 /*
1148  * The ext4_get_blocks() function tries to look up the requested blocks,
1149  * and returns if the blocks are already mapped.
1150  *
1151  * Otherwise it takes the write lock of the i_data_sem and allocate blocks
1152  * and store the allocated blocks in the result buffer head and mark it
1153  * mapped.
1154  *
1155  * If file type is extents based, it will call ext4_ext_get_blocks(),
1156  * Otherwise, call with ext4_ind_get_blocks() to handle indirect mapping
1157  * based files
1158  *
1159  * On success, it returns the number of blocks being mapped or allocate.
1160  * if create==0 and the blocks are pre-allocated and uninitialized block,
1161  * the result buffer head is unmapped. If the create ==1, it will make sure
1162  * the buffer head is mapped.
1163  *
1164  * It returns 0 if plain look up failed (blocks have not been allocated), in
1165  * that casem, buffer head is unmapped
1166  *
1167  * It returns the error in case of allocation failure.
1168  */
1169 int ext4_get_blocks(handle_t *handle, struct inode *inode, sector_t block,
1170                     unsigned int max_blocks, struct buffer_head *bh,
1171                     int flags)
1172 {
1173         int retval;
1174
1175         clear_buffer_mapped(bh);
1176         clear_buffer_unwritten(bh);
1177
1178         /*
1179          * Try to see if we can get the block without requesting a new
1180          * file system block.
1181          */
1182         down_read((&EXT4_I(inode)->i_data_sem));
1183         if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) {
1184                 retval =  ext4_ext_get_blocks(handle, inode, block, max_blocks,
1185                                 bh, 0);
1186         } else {
1187                 retval = ext4_ind_get_blocks(handle, inode, block, max_blocks,
1188                                              bh, 0);
1189         }
1190         up_read((&EXT4_I(inode)->i_data_sem));
1191
1192         if (retval > 0 && buffer_mapped(bh)) {
1193                 int ret = check_block_validity(inode, "file system corruption",
1194                                                block, bh->b_blocknr, retval);
1195                 if (ret != 0)
1196                         return ret;
1197         }
1198
1199         /* If it is only a block(s) look up */
1200         if ((flags & EXT4_GET_BLOCKS_CREATE) == 0)
1201                 return retval;
1202
1203         /*
1204          * Returns if the blocks have already allocated
1205          *
1206          * Note that if blocks have been preallocated
1207          * ext4_ext_get_block() returns th create = 0
1208          * with buffer head unmapped.
1209          */
1210         if (retval > 0 && buffer_mapped(bh))
1211                 return retval;
1212
1213         /*
1214          * When we call get_blocks without the create flag, the
1215          * BH_Unwritten flag could have gotten set if the blocks
1216          * requested were part of a uninitialized extent.  We need to
1217          * clear this flag now that we are committed to convert all or
1218          * part of the uninitialized extent to be an initialized
1219          * extent.  This is because we need to avoid the combination
1220          * of BH_Unwritten and BH_Mapped flags being simultaneously
1221          * set on the buffer_head.
1222          */
1223         clear_buffer_unwritten(bh);
1224
1225         /*
1226          * New blocks allocate and/or writing to uninitialized extent
1227          * will possibly result in updating i_data, so we take
1228          * the write lock of i_data_sem, and call get_blocks()
1229          * with create == 1 flag.
1230          */
1231         down_write((&EXT4_I(inode)->i_data_sem));
1232
1233         /*
1234          * if the caller is from delayed allocation writeout path
1235          * we have already reserved fs blocks for allocation
1236          * let the underlying get_block() function know to
1237          * avoid double accounting
1238          */
1239         if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
1240                 EXT4_I(inode)->i_delalloc_reserved_flag = 1;
1241         /*
1242          * We need to check for EXT4 here because migrate
1243          * could have changed the inode type in between
1244          */
1245         if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) {
1246                 retval =  ext4_ext_get_blocks(handle, inode, block, max_blocks,
1247                                               bh, flags);
1248         } else {
1249                 retval = ext4_ind_get_blocks(handle, inode, block,
1250                                              max_blocks, bh, flags);
1251
1252                 if (retval > 0 && buffer_new(bh)) {
1253                         /*
1254                          * We allocated new blocks which will result in
1255                          * i_data's format changing.  Force the migrate
1256                          * to fail by clearing migrate flags
1257                          */
1258                         EXT4_I(inode)->i_state &= ~EXT4_STATE_EXT_MIGRATE;
1259                 }
1260         }
1261
1262         if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
1263                 EXT4_I(inode)->i_delalloc_reserved_flag = 0;
1264
1265         /*
1266          * Update reserved blocks/metadata blocks after successful
1267          * block allocation which had been deferred till now.
1268          */
1269         if ((retval > 0) && (flags & EXT4_GET_BLOCKS_UPDATE_RESERVE_SPACE))
1270                 ext4_da_update_reserve_space(inode, retval);
1271
1272         up_write((&EXT4_I(inode)->i_data_sem));
1273         if (retval > 0 && buffer_mapped(bh)) {
1274                 int ret = check_block_validity(inode, "file system "
1275                                                "corruption after allocation",
1276                                                block, bh->b_blocknr, retval);
1277                 if (ret != 0)
1278                         return ret;
1279         }
1280         return retval;
1281 }
1282
1283 /* Maximum number of blocks we map for direct IO at once. */
1284 #define DIO_MAX_BLOCKS 4096
1285
1286 int ext4_get_block(struct inode *inode, sector_t iblock,
1287                    struct buffer_head *bh_result, int create)
1288 {
1289         handle_t *handle = ext4_journal_current_handle();
1290         int ret = 0, started = 0;
1291         unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
1292         int dio_credits;
1293
1294         if (create && !handle) {
1295                 /* Direct IO write... */
1296                 if (max_blocks > DIO_MAX_BLOCKS)
1297                         max_blocks = DIO_MAX_BLOCKS;
1298                 dio_credits = ext4_chunk_trans_blocks(inode, max_blocks);
1299                 handle = ext4_journal_start(inode, dio_credits);
1300                 if (IS_ERR(handle)) {
1301                         ret = PTR_ERR(handle);
1302                         goto out;
1303                 }
1304                 started = 1;
1305         }
1306
1307         ret = ext4_get_blocks(handle, inode, iblock, max_blocks, bh_result,
1308                               create ? EXT4_GET_BLOCKS_CREATE : 0);
1309         if (ret > 0) {
1310                 bh_result->b_size = (ret << inode->i_blkbits);
1311                 ret = 0;
1312         }
1313         if (started)
1314                 ext4_journal_stop(handle);
1315 out:
1316         return ret;
1317 }
1318
1319 /*
1320  * `handle' can be NULL if create is zero
1321  */
1322 struct buffer_head *ext4_getblk(handle_t *handle, struct inode *inode,
1323                                 ext4_lblk_t block, int create, int *errp)
1324 {
1325         struct buffer_head dummy;
1326         int fatal = 0, err;
1327         int flags = 0;
1328
1329         J_ASSERT(handle != NULL || create == 0);
1330
1331         dummy.b_state = 0;
1332         dummy.b_blocknr = -1000;
1333         buffer_trace_init(&dummy.b_history);
1334         if (create)
1335                 flags |= EXT4_GET_BLOCKS_CREATE;
1336         err = ext4_get_blocks(handle, inode, block, 1, &dummy, flags);
1337         /*
1338          * ext4_get_blocks() returns number of blocks mapped. 0 in
1339          * case of a HOLE.
1340          */
1341         if (err > 0) {
1342                 if (err > 1)
1343                         WARN_ON(1);
1344                 err = 0;
1345         }
1346         *errp = err;
1347         if (!err && buffer_mapped(&dummy)) {
1348                 struct buffer_head *bh;
1349                 bh = sb_getblk(inode->i_sb, dummy.b_blocknr);
1350                 if (!bh) {
1351                         *errp = -EIO;
1352                         goto err;
1353                 }
1354                 if (buffer_new(&dummy)) {
1355                         J_ASSERT(create != 0);
1356                         J_ASSERT(handle != NULL);
1357
1358                         /*
1359                          * Now that we do not always journal data, we should
1360                          * keep in mind whether this should always journal the
1361                          * new buffer as metadata.  For now, regular file
1362                          * writes use ext4_get_block instead, so it's not a
1363                          * problem.
1364                          */
1365                         lock_buffer(bh);
1366                         BUFFER_TRACE(bh, "call get_create_access");
1367                         fatal = ext4_journal_get_create_access(handle, bh);
1368                         if (!fatal && !buffer_uptodate(bh)) {
1369                                 memset(bh->b_data, 0, inode->i_sb->s_blocksize);
1370                                 set_buffer_uptodate(bh);
1371                         }
1372                         unlock_buffer(bh);
1373                         BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
1374                         err = ext4_handle_dirty_metadata(handle, inode, bh);
1375                         if (!fatal)
1376                                 fatal = err;
1377                 } else {
1378                         BUFFER_TRACE(bh, "not a new buffer");
1379                 }
1380                 if (fatal) {
1381                         *errp = fatal;
1382                         brelse(bh);
1383                         bh = NULL;
1384                 }
1385                 return bh;
1386         }
1387 err:
1388         return NULL;
1389 }
1390
1391 struct buffer_head *ext4_bread(handle_t *handle, struct inode *inode,
1392                                ext4_lblk_t block, int create, int *err)
1393 {
1394         struct buffer_head *bh;
1395
1396         bh = ext4_getblk(handle, inode, block, create, err);
1397         if (!bh)
1398                 return bh;
1399         if (buffer_uptodate(bh))
1400                 return bh;
1401         ll_rw_block(READ_META, 1, &bh);
1402         wait_on_buffer(bh);
1403         if (buffer_uptodate(bh))
1404                 return bh;
1405         put_bh(bh);
1406         *err = -EIO;
1407         return NULL;
1408 }
1409
1410 static int walk_page_buffers(handle_t *handle,
1411                              struct buffer_head *head,
1412                              unsigned from,
1413                              unsigned to,
1414                              int *partial,
1415                              int (*fn)(handle_t *handle,
1416                                        struct buffer_head *bh))
1417 {
1418         struct buffer_head *bh;
1419         unsigned block_start, block_end;
1420         unsigned blocksize = head->b_size;
1421         int err, ret = 0;
1422         struct buffer_head *next;
1423
1424         for (bh = head, block_start = 0;
1425              ret == 0 && (bh != head || !block_start);
1426              block_start = block_end, bh = next) {
1427                 next = bh->b_this_page;
1428                 block_end = block_start + blocksize;
1429                 if (block_end <= from || block_start >= to) {
1430                         if (partial && !buffer_uptodate(bh))
1431                                 *partial = 1;
1432                         continue;
1433                 }
1434                 err = (*fn)(handle, bh);
1435                 if (!ret)
1436                         ret = err;
1437         }
1438         return ret;
1439 }
1440
1441 /*
1442  * To preserve ordering, it is essential that the hole instantiation and
1443  * the data write be encapsulated in a single transaction.  We cannot
1444  * close off a transaction and start a new one between the ext4_get_block()
1445  * and the commit_write().  So doing the jbd2_journal_start at the start of
1446  * prepare_write() is the right place.
1447  *
1448  * Also, this function can nest inside ext4_writepage() ->
1449  * block_write_full_page(). In that case, we *know* that ext4_writepage()
1450  * has generated enough buffer credits to do the whole page.  So we won't
1451  * block on the journal in that case, which is good, because the caller may
1452  * be PF_MEMALLOC.
1453  *
1454  * By accident, ext4 can be reentered when a transaction is open via
1455  * quota file writes.  If we were to commit the transaction while thus
1456  * reentered, there can be a deadlock - we would be holding a quota
1457  * lock, and the commit would never complete if another thread had a
1458  * transaction open and was blocking on the quota lock - a ranking
1459  * violation.
1460  *
1461  * So what we do is to rely on the fact that jbd2_journal_stop/journal_start
1462  * will _not_ run commit under these circumstances because handle->h_ref
1463  * is elevated.  We'll still have enough credits for the tiny quotafile
1464  * write.
1465  */
1466 static int do_journal_get_write_access(handle_t *handle,
1467                                        struct buffer_head *bh)
1468 {
1469         if (!buffer_mapped(bh) || buffer_freed(bh))
1470                 return 0;
1471         return ext4_journal_get_write_access(handle, bh);
1472 }
1473
1474 static int ext4_write_begin(struct file *file, struct address_space *mapping,
1475                             loff_t pos, unsigned len, unsigned flags,
1476                             struct page **pagep, void **fsdata)
1477 {
1478         struct inode *inode = mapping->host;
1479         int ret, needed_blocks;
1480         handle_t *handle;
1481         int retries = 0;
1482         struct page *page;
1483         pgoff_t index;
1484         unsigned from, to;
1485
1486         trace_ext4_write_begin(inode, pos, len, flags);
1487         /*
1488          * Reserve one block more for addition to orphan list in case
1489          * we allocate blocks but write fails for some reason
1490          */
1491         needed_blocks = ext4_writepage_trans_blocks(inode) + 1;
1492         index = pos >> PAGE_CACHE_SHIFT;
1493         from = pos & (PAGE_CACHE_SIZE - 1);
1494         to = from + len;
1495
1496 retry:
1497         handle = ext4_journal_start(inode, needed_blocks);
1498         if (IS_ERR(handle)) {
1499                 ret = PTR_ERR(handle);
1500                 goto out;
1501         }
1502
1503         /* We cannot recurse into the filesystem as the transaction is already
1504          * started */
1505         flags |= AOP_FLAG_NOFS;
1506
1507         page = grab_cache_page_write_begin(mapping, index, flags);
1508         if (!page) {
1509                 ext4_journal_stop(handle);
1510                 ret = -ENOMEM;
1511                 goto out;
1512         }
1513         *pagep = page;
1514
1515         ret = block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
1516                                 ext4_get_block);
1517
1518         if (!ret && ext4_should_journal_data(inode)) {
1519                 ret = walk_page_buffers(handle, page_buffers(page),
1520                                 from, to, NULL, do_journal_get_write_access);
1521         }
1522
1523         if (ret) {
1524                 unlock_page(page);
1525                 page_cache_release(page);
1526                 /*
1527                  * block_write_begin may have instantiated a few blocks
1528                  * outside i_size.  Trim these off again. Don't need
1529                  * i_size_read because we hold i_mutex.
1530                  *
1531                  * Add inode to orphan list in case we crash before
1532                  * truncate finishes
1533                  */
1534                 if (pos + len > inode->i_size && ext4_can_truncate(inode))
1535                         ext4_orphan_add(handle, inode);
1536
1537                 ext4_journal_stop(handle);
1538                 if (pos + len > inode->i_size) {
1539                         ext4_truncate(inode);
1540                         /*
1541                          * If truncate failed early the inode might
1542                          * still be on the orphan list; we need to
1543                          * make sure the inode is removed from the
1544                          * orphan list in that case.
1545                          */
1546                         if (inode->i_nlink)
1547                                 ext4_orphan_del(NULL, inode);
1548                 }
1549         }
1550
1551         if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
1552                 goto retry;
1553 out:
1554         return ret;
1555 }
1556
1557 /* For write_end() in data=journal mode */
1558 static int write_end_fn(handle_t *handle, struct buffer_head *bh)
1559 {
1560         if (!buffer_mapped(bh) || buffer_freed(bh))
1561                 return 0;
1562         set_buffer_uptodate(bh);
1563         return ext4_handle_dirty_metadata(handle, NULL, bh);
1564 }
1565
1566 static int ext4_generic_write_end(struct file *file,
1567                                   struct address_space *mapping,
1568                                   loff_t pos, unsigned len, unsigned copied,
1569                                   struct page *page, void *fsdata)
1570 {
1571         int i_size_changed = 0;
1572         struct inode *inode = mapping->host;
1573         handle_t *handle = ext4_journal_current_handle();
1574
1575         copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
1576
1577         /*
1578          * No need to use i_size_read() here, the i_size
1579          * cannot change under us because we hold i_mutex.
1580          *
1581          * But it's important to update i_size while still holding page lock:
1582          * page writeout could otherwise come in and zero beyond i_size.
1583          */
1584         if (pos + copied > inode->i_size) {
1585                 i_size_write(inode, pos + copied);
1586                 i_size_changed = 1;
1587         }
1588
1589         if (pos + copied >  EXT4_I(inode)->i_disksize) {
1590                 /* We need to mark inode dirty even if
1591                  * new_i_size is less that inode->i_size
1592                  * bu greater than i_disksize.(hint delalloc)
1593                  */
1594                 ext4_update_i_disksize(inode, (pos + copied));
1595                 i_size_changed = 1;
1596         }
1597         unlock_page(page);
1598         page_cache_release(page);
1599
1600         /*
1601          * Don't mark the inode dirty under page lock. First, it unnecessarily
1602          * makes the holding time of page lock longer. Second, it forces lock
1603          * ordering of page lock and transaction start for journaling
1604          * filesystems.
1605          */
1606         if (i_size_changed)
1607                 ext4_mark_inode_dirty(handle, inode);
1608
1609         return copied;
1610 }
1611
1612 /*
1613  * We need to pick up the new inode size which generic_commit_write gave us
1614  * `file' can be NULL - eg, when called from page_symlink().
1615  *
1616  * ext4 never places buffers on inode->i_mapping->private_list.  metadata
1617  * buffers are managed internally.
1618  */
1619 static int ext4_ordered_write_end(struct file *file,
1620                                   struct address_space *mapping,
1621                                   loff_t pos, unsigned len, unsigned copied,
1622                                   struct page *page, void *fsdata)
1623 {
1624         handle_t *handle = ext4_journal_current_handle();
1625         struct inode *inode = mapping->host;
1626         int ret = 0, ret2;
1627
1628         trace_ext4_ordered_write_end(inode, pos, len, copied);
1629         ret = ext4_jbd2_file_inode(handle, inode);
1630
1631         if (ret == 0) {
1632                 ret2 = ext4_generic_write_end(file, mapping, pos, len, copied,
1633                                                         page, fsdata);
1634                 copied = ret2;
1635                 if (pos + len > inode->i_size && ext4_can_truncate(inode))
1636                         /* if we have allocated more blocks and copied
1637                          * less. We will have blocks allocated outside
1638                          * inode->i_size. So truncate them
1639                          */
1640                         ext4_orphan_add(handle, inode);
1641                 if (ret2 < 0)
1642                         ret = ret2;
1643         }
1644         ret2 = ext4_journal_stop(handle);
1645         if (!ret)
1646                 ret = ret2;
1647
1648         if (pos + len > inode->i_size) {
1649                 ext4_truncate(inode);
1650                 /*
1651                  * If truncate failed early the inode might still be
1652                  * on the orphan list; we need to make sure the inode
1653                  * is removed from the orphan list in that case.
1654                  */
1655                 if (inode->i_nlink)
1656                         ext4_orphan_del(NULL, inode);
1657         }
1658
1659
1660         return ret ? ret : copied;
1661 }
1662
1663 static int ext4_writeback_write_end(struct file *file,
1664                                     struct address_space *mapping,
1665                                     loff_t pos, unsigned len, unsigned copied,
1666                                     struct page *page, void *fsdata)
1667 {
1668         handle_t *handle = ext4_journal_current_handle();
1669         struct inode *inode = mapping->host;
1670         int ret = 0, ret2;
1671
1672         trace_ext4_writeback_write_end(inode, pos, len, copied);
1673         ret2 = ext4_generic_write_end(file, mapping, pos, len, copied,
1674                                                         page, fsdata);
1675         copied = ret2;
1676         if (pos + len > inode->i_size && ext4_can_truncate(inode))
1677                 /* if we have allocated more blocks and copied
1678                  * less. We will have blocks allocated outside
1679                  * inode->i_size. So truncate them
1680                  */
1681                 ext4_orphan_add(handle, inode);
1682
1683         if (ret2 < 0)
1684                 ret = ret2;
1685
1686         ret2 = ext4_journal_stop(handle);
1687         if (!ret)
1688                 ret = ret2;
1689
1690         if (pos + len > inode->i_size) {
1691                 ext4_truncate(inode);
1692                 /*
1693                  * If truncate failed early the inode might still be
1694                  * on the orphan list; we need to make sure the inode
1695                  * is removed from the orphan list in that case.
1696                  */
1697                 if (inode->i_nlink)
1698                         ext4_orphan_del(NULL, inode);
1699         }
1700
1701         return ret ? ret : copied;
1702 }
1703
1704 static int ext4_journalled_write_end(struct file *file,
1705                                      struct address_space *mapping,
1706                                      loff_t pos, unsigned len, unsigned copied,
1707                                      struct page *page, void *fsdata)
1708 {
1709         handle_t *handle = ext4_journal_current_handle();
1710         struct inode *inode = mapping->host;
1711         int ret = 0, ret2;
1712         int partial = 0;
1713         unsigned from, to;
1714         loff_t new_i_size;
1715
1716         trace_ext4_journalled_write_end(inode, pos, len, copied);
1717         from = pos & (PAGE_CACHE_SIZE - 1);
1718         to = from + len;
1719
1720         if (copied < len) {
1721                 if (!PageUptodate(page))
1722                         copied = 0;
1723                 page_zero_new_buffers(page, from+copied, to);
1724         }
1725
1726         ret = walk_page_buffers(handle, page_buffers(page), from,
1727                                 to, &partial, write_end_fn);
1728         if (!partial)
1729                 SetPageUptodate(page);
1730         new_i_size = pos + copied;
1731         if (new_i_size > inode->i_size)
1732                 i_size_write(inode, pos+copied);
1733         EXT4_I(inode)->i_state |= EXT4_STATE_JDATA;
1734         if (new_i_size > EXT4_I(inode)->i_disksize) {
1735                 ext4_update_i_disksize(inode, new_i_size);
1736                 ret2 = ext4_mark_inode_dirty(handle, inode);
1737                 if (!ret)
1738                         ret = ret2;
1739         }
1740
1741         unlock_page(page);
1742         page_cache_release(page);
1743         if (pos + len > inode->i_size && ext4_can_truncate(inode))
1744                 /* if we have allocated more blocks and copied
1745                  * less. We will have blocks allocated outside
1746                  * inode->i_size. So truncate them
1747                  */
1748                 ext4_orphan_add(handle, inode);
1749
1750         ret2 = ext4_journal_stop(handle);
1751         if (!ret)
1752                 ret = ret2;
1753         if (pos + len > inode->i_size) {
1754                 ext4_truncate(inode);
1755                 /*
1756                  * If truncate failed early the inode might still be
1757                  * on the orphan list; we need to make sure the inode
1758                  * is removed from the orphan list in that case.
1759                  */
1760                 if (inode->i_nlink)
1761                         ext4_orphan_del(NULL, inode);
1762         }
1763
1764         return ret ? ret : copied;
1765 }
1766
1767 static int ext4_da_reserve_space(struct inode *inode, int nrblocks)
1768 {
1769         int retries = 0;
1770         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
1771         unsigned long md_needed, mdblocks, total = 0;
1772
1773         /*
1774          * recalculate the amount of metadata blocks to reserve
1775          * in order to allocate nrblocks
1776          * worse case is one extent per block
1777          */
1778 repeat:
1779         spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
1780         total = EXT4_I(inode)->i_reserved_data_blocks + nrblocks;
1781         mdblocks = ext4_calc_metadata_amount(inode, total);
1782         BUG_ON(mdblocks < EXT4_I(inode)->i_reserved_meta_blocks);
1783
1784         md_needed = mdblocks - EXT4_I(inode)->i_reserved_meta_blocks;
1785         total = md_needed + nrblocks;
1786
1787         /*
1788          * Make quota reservation here to prevent quota overflow
1789          * later. Real quota accounting is done at pages writeout
1790          * time.
1791          */
1792         if (vfs_dq_reserve_block(inode, total)) {
1793                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1794                 return -EDQUOT;
1795         }
1796
1797         if (ext4_claim_free_blocks(sbi, total)) {
1798                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1799                 if (ext4_should_retry_alloc(inode->i_sb, &retries)) {
1800                         yield();
1801                         goto repeat;
1802                 }
1803                 vfs_dq_release_reservation_block(inode, total);
1804                 return -ENOSPC;
1805         }
1806         EXT4_I(inode)->i_reserved_data_blocks += nrblocks;
1807         EXT4_I(inode)->i_reserved_meta_blocks = mdblocks;
1808
1809         spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1810         return 0;       /* success */
1811 }
1812
1813 static void ext4_da_release_space(struct inode *inode, int to_free)
1814 {
1815         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
1816         int total, mdb, mdb_free, release;
1817
1818         if (!to_free)
1819                 return;         /* Nothing to release, exit */
1820
1821         spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
1822
1823         if (!EXT4_I(inode)->i_reserved_data_blocks) {
1824                 /*
1825                  * if there is no reserved blocks, but we try to free some
1826                  * then the counter is messed up somewhere.
1827                  * but since this function is called from invalidate
1828                  * page, it's harmless to return without any action
1829                  */
1830                 printk(KERN_INFO "ext4 delalloc try to release %d reserved "
1831                             "blocks for inode %lu, but there is no reserved "
1832                             "data blocks\n", to_free, inode->i_ino);
1833                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1834                 return;
1835         }
1836
1837         /* recalculate the number of metablocks still need to be reserved */
1838         total = EXT4_I(inode)->i_reserved_data_blocks - to_free;
1839         mdb = ext4_calc_metadata_amount(inode, total);
1840
1841         /* figure out how many metablocks to release */
1842         BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
1843         mdb_free = EXT4_I(inode)->i_reserved_meta_blocks - mdb;
1844
1845         release = to_free + mdb_free;
1846
1847         /* update fs dirty blocks counter for truncate case */
1848         percpu_counter_sub(&sbi->s_dirtyblocks_counter, release);
1849
1850         /* update per-inode reservations */
1851         BUG_ON(to_free > EXT4_I(inode)->i_reserved_data_blocks);
1852         EXT4_I(inode)->i_reserved_data_blocks -= to_free;
1853
1854         BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
1855         EXT4_I(inode)->i_reserved_meta_blocks = mdb;
1856         spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1857
1858         vfs_dq_release_reservation_block(inode, release);
1859 }
1860
1861 static void ext4_da_page_release_reservation(struct page *page,
1862                                              unsigned long offset)
1863 {
1864         int to_release = 0;
1865         struct buffer_head *head, *bh;
1866         unsigned int curr_off = 0;
1867
1868         head = page_buffers(page);
1869         bh = head;
1870         do {
1871                 unsigned int next_off = curr_off + bh->b_size;
1872
1873                 if ((offset <= curr_off) && (buffer_delay(bh))) {
1874                         to_release++;
1875                         clear_buffer_delay(bh);
1876                 }
1877                 curr_off = next_off;
1878         } while ((bh = bh->b_this_page) != head);
1879         ext4_da_release_space(page->mapping->host, to_release);
1880 }
1881
1882 /*
1883  * Delayed allocation stuff
1884  */
1885
1886 /*
1887  * mpage_da_submit_io - walks through extent of pages and try to write
1888  * them with writepage() call back
1889  *
1890  * @mpd->inode: inode
1891  * @mpd->first_page: first page of the extent
1892  * @mpd->next_page: page after the last page of the extent
1893  *
1894  * By the time mpage_da_submit_io() is called we expect all blocks
1895  * to be allocated. this may be wrong if allocation failed.
1896  *
1897  * As pages are already locked by write_cache_pages(), we can't use it
1898  */
1899 static int mpage_da_submit_io(struct mpage_da_data *mpd)
1900 {
1901         long pages_skipped;
1902         struct pagevec pvec;
1903         unsigned long index, end;
1904         int ret = 0, err, nr_pages, i;
1905         struct inode *inode = mpd->inode;
1906         struct address_space *mapping = inode->i_mapping;
1907
1908         BUG_ON(mpd->next_page <= mpd->first_page);
1909         /*
1910          * We need to start from the first_page to the next_page - 1
1911          * to make sure we also write the mapped dirty buffer_heads.
1912          * If we look at mpd->b_blocknr we would only be looking
1913          * at the currently mapped buffer_heads.
1914          */
1915         index = mpd->first_page;
1916         end = mpd->next_page - 1;
1917
1918         pagevec_init(&pvec, 0);
1919         while (index <= end) {
1920                 nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
1921                 if (nr_pages == 0)
1922                         break;
1923                 for (i = 0; i < nr_pages; i++) {
1924                         struct page *page = pvec.pages[i];
1925
1926                         index = page->index;
1927                         if (index > end)
1928                                 break;
1929                         index++;
1930
1931                         BUG_ON(!PageLocked(page));
1932                         BUG_ON(PageWriteback(page));
1933
1934                         pages_skipped = mpd->wbc->pages_skipped;
1935                         err = mapping->a_ops->writepage(page, mpd->wbc);
1936                         if (!err && (pages_skipped == mpd->wbc->pages_skipped))
1937                                 /*
1938                                  * have successfully written the page
1939                                  * without skipping the same
1940                                  */
1941                                 mpd->pages_written++;
1942                         /*
1943                          * In error case, we have to continue because
1944                          * remaining pages are still locked
1945                          * XXX: unlock and re-dirty them?
1946                          */
1947                         if (ret == 0)
1948                                 ret = err;
1949                 }
1950                 pagevec_release(&pvec);
1951         }
1952         return ret;
1953 }
1954
1955 /*
1956  * mpage_put_bnr_to_bhs - walk blocks and assign them actual numbers
1957  *
1958  * @mpd->inode - inode to walk through
1959  * @exbh->b_blocknr - first block on a disk
1960  * @exbh->b_size - amount of space in bytes
1961  * @logical - first logical block to start assignment with
1962  *
1963  * the function goes through all passed space and put actual disk
1964  * block numbers into buffer heads, dropping BH_Delay and BH_Unwritten
1965  */
1966 static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd, sector_t logical,
1967                                  struct buffer_head *exbh)
1968 {
1969         struct inode *inode = mpd->inode;
1970         struct address_space *mapping = inode->i_mapping;
1971         int blocks = exbh->b_size >> inode->i_blkbits;
1972         sector_t pblock = exbh->b_blocknr, cur_logical;
1973         struct buffer_head *head, *bh;
1974         pgoff_t index, end;
1975         struct pagevec pvec;
1976         int nr_pages, i;
1977
1978         index = logical >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
1979         end = (logical + blocks - 1) >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
1980         cur_logical = index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
1981
1982         pagevec_init(&pvec, 0);
1983
1984         while (index <= end) {
1985                 /* XXX: optimize tail */
1986                 nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
1987                 if (nr_pages == 0)
1988                         break;
1989                 for (i = 0; i < nr_pages; i++) {
1990                         struct page *page = pvec.pages[i];
1991
1992                         index = page->index;
1993                         if (index > end)
1994                                 break;
1995                         index++;
1996
1997                         BUG_ON(!PageLocked(page));
1998                         BUG_ON(PageWriteback(page));
1999                         BUG_ON(!page_has_buffers(page));
2000
2001                         bh = page_buffers(page);
2002                         head = bh;
2003
2004                         /* skip blocks out of the range */
2005                         do {
2006                                 if (cur_logical >= logical)
2007                                         break;
2008                                 cur_logical++;
2009                         } while ((bh = bh->b_this_page) != head);
2010
2011                         do {
2012                                 if (cur_logical >= logical + blocks)
2013                                         break;
2014
2015                                 if (buffer_delay(bh) ||
2016                                                 buffer_unwritten(bh)) {
2017
2018                                         BUG_ON(bh->b_bdev != inode->i_sb->s_bdev);
2019
2020                                         if (buffer_delay(bh)) {
2021                                                 clear_buffer_delay(bh);
2022                                                 bh->b_blocknr = pblock;
2023                                         } else {
2024                                                 /*
2025                                                  * unwritten already should have
2026                                                  * blocknr assigned. Verify that
2027                                                  */
2028                                                 clear_buffer_unwritten(bh);
2029                                                 BUG_ON(bh->b_blocknr != pblock);
2030                                         }
2031
2032                                 } else if (buffer_mapped(bh))
2033                                         BUG_ON(bh->b_blocknr != pblock);
2034
2035                                 cur_logical++;
2036                                 pblock++;
2037                         } while ((bh = bh->b_this_page) != head);
2038                 }
2039                 pagevec_release(&pvec);
2040         }
2041 }
2042
2043
2044 /*
2045  * __unmap_underlying_blocks - just a helper function to unmap
2046  * set of blocks described by @bh
2047  */
2048 static inline void __unmap_underlying_blocks(struct inode *inode,
2049                                              struct buffer_head *bh)
2050 {
2051         struct block_device *bdev = inode->i_sb->s_bdev;
2052         int blocks, i;
2053
2054         blocks = bh->b_size >> inode->i_blkbits;
2055         for (i = 0; i < blocks; i++)
2056                 unmap_underlying_metadata(bdev, bh->b_blocknr + i);
2057 }
2058
2059 static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd,
2060                                         sector_t logical, long blk_cnt)
2061 {
2062         int nr_pages, i;
2063         pgoff_t index, end;
2064         struct pagevec pvec;
2065         struct inode *inode = mpd->inode;
2066         struct address_space *mapping = inode->i_mapping;
2067
2068         index = logical >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
2069         end   = (logical + blk_cnt - 1) >>
2070                                 (PAGE_CACHE_SHIFT - inode->i_blkbits);
2071         while (index <= end) {
2072                 nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
2073                 if (nr_pages == 0)
2074                         break;
2075                 for (i = 0; i < nr_pages; i++) {
2076                         struct page *page = pvec.pages[i];
2077                         index = page->index;
2078                         if (index > end)
2079                                 break;
2080                         index++;
2081
2082                         BUG_ON(!PageLocked(page));
2083                         BUG_ON(PageWriteback(page));
2084                         block_invalidatepage(page, 0);
2085                         ClearPageUptodate(page);
2086                         unlock_page(page);
2087                 }
2088         }
2089         return;
2090 }
2091
2092 static void ext4_print_free_blocks(struct inode *inode)
2093 {
2094         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
2095         printk(KERN_CRIT "Total free blocks count %lld\n",
2096                ext4_count_free_blocks(inode->i_sb));
2097         printk(KERN_CRIT "Free/Dirty block details\n");
2098         printk(KERN_CRIT "free_blocks=%lld\n",
2099                (long long) percpu_counter_sum(&sbi->s_freeblocks_counter));
2100         printk(KERN_CRIT "dirty_blocks=%lld\n",
2101                (long long) percpu_counter_sum(&sbi->s_dirtyblocks_counter));
2102         printk(KERN_CRIT "Block reservation details\n");
2103         printk(KERN_CRIT "i_reserved_data_blocks=%u\n",
2104                EXT4_I(inode)->i_reserved_data_blocks);
2105         printk(KERN_CRIT "i_reserved_meta_blocks=%u\n",
2106                EXT4_I(inode)->i_reserved_meta_blocks);
2107         return;
2108 }
2109
2110 /*
2111  * mpage_da_map_blocks - go through given space
2112  *
2113  * @mpd - bh describing space
2114  *
2115  * The function skips space we know is already mapped to disk blocks.
2116  *
2117  */
2118 static int mpage_da_map_blocks(struct mpage_da_data *mpd)
2119 {
2120         int err, blks, get_blocks_flags;
2121         struct buffer_head new;
2122         sector_t next = mpd->b_blocknr;
2123         unsigned max_blocks = mpd->b_size >> mpd->inode->i_blkbits;
2124         loff_t disksize = EXT4_I(mpd->inode)->i_disksize;
2125         handle_t *handle = NULL;
2126
2127         /*
2128          * We consider only non-mapped and non-allocated blocks
2129          */
2130         if ((mpd->b_state  & (1 << BH_Mapped)) &&
2131                 !(mpd->b_state & (1 << BH_Delay)) &&
2132                 !(mpd->b_state & (1 << BH_Unwritten)))
2133                 return 0;
2134
2135         /*
2136          * If we didn't accumulate anything to write simply return
2137          */
2138         if (!mpd->b_size)
2139                 return 0;
2140
2141         handle = ext4_journal_current_handle();
2142         BUG_ON(!handle);
2143
2144         /*
2145          * Call ext4_get_blocks() to allocate any delayed allocation
2146          * blocks, or to convert an uninitialized extent to be
2147          * initialized (in the case where we have written into
2148          * one or more preallocated blocks).
2149          *
2150          * We pass in the magic EXT4_GET_BLOCKS_DELALLOC_RESERVE to
2151          * indicate that we are on the delayed allocation path.  This
2152          * affects functions in many different parts of the allocation
2153          * call path.  This flag exists primarily because we don't
2154          * want to change *many* call functions, so ext4_get_blocks()
2155          * will set the magic i_delalloc_reserved_flag once the
2156          * inode's allocation semaphore is taken.
2157          *
2158          * If the blocks in questions were delalloc blocks, set
2159          * EXT4_GET_BLOCKS_DELALLOC_RESERVE so the delalloc accounting
2160          * variables are updated after the blocks have been allocated.
2161          */
2162         new.b_state = 0;
2163         get_blocks_flags = (EXT4_GET_BLOCKS_CREATE |
2164                             EXT4_GET_BLOCKS_DELALLOC_RESERVE);
2165         if (mpd->b_state & (1 << BH_Delay))
2166                 get_blocks_flags |= EXT4_GET_BLOCKS_UPDATE_RESERVE_SPACE;
2167         blks = ext4_get_blocks(handle, mpd->inode, next, max_blocks,
2168                                &new, get_blocks_flags);
2169         if (blks < 0) {
2170                 err = blks;
2171                 /*
2172                  * If get block returns with error we simply
2173                  * return. Later writepage will redirty the page and
2174                  * writepages will find the dirty page again
2175                  */
2176                 if (err == -EAGAIN)
2177                         return 0;
2178
2179                 if (err == -ENOSPC &&
2180                     ext4_count_free_blocks(mpd->inode->i_sb)) {
2181                         mpd->retval = err;
2182                         return 0;
2183                 }
2184
2185                 /*
2186                  * get block failure will cause us to loop in
2187                  * writepages, because a_ops->writepage won't be able
2188                  * to make progress. The page will be redirtied by
2189                  * writepage and writepages will again try to write
2190                  * the same.
2191                  */
2192                 ext4_msg(mpd->inode->i_sb, KERN_CRIT,
2193                          "delayed block allocation failed for inode %lu at "
2194                          "logical offset %llu with max blocks %zd with "
2195                          "error %d\n", mpd->inode->i_ino,
2196                          (unsigned long long) next,
2197                          mpd->b_size >> mpd->inode->i_blkbits, err);
2198                 printk(KERN_CRIT "This should not happen!!  "
2199                        "Data will be lost\n");
2200                 if (err == -ENOSPC) {
2201                         ext4_print_free_blocks(mpd->inode);
2202                 }
2203                 /* invalidate all the pages */
2204                 ext4_da_block_invalidatepages(mpd, next,
2205                                 mpd->b_size >> mpd->inode->i_blkbits);
2206                 return err;
2207         }
2208         BUG_ON(blks == 0);
2209
2210         new.b_size = (blks << mpd->inode->i_blkbits);
2211
2212         if (buffer_new(&new))
2213                 __unmap_underlying_blocks(mpd->inode, &new);
2214
2215         /*
2216          * If blocks are delayed marked, we need to
2217          * put actual blocknr and drop delayed bit
2218          */
2219         if ((mpd->b_state & (1 << BH_Delay)) ||
2220             (mpd->b_state & (1 << BH_Unwritten)))
2221                 mpage_put_bnr_to_bhs(mpd, next, &new);
2222
2223         if (ext4_should_order_data(mpd->inode)) {
2224                 err = ext4_jbd2_file_inode(handle, mpd->inode);
2225                 if (err)
2226                         return err;
2227         }
2228
2229         /*
2230          * Update on-disk size along with block allocation.
2231          */
2232         disksize = ((loff_t) next + blks) << mpd->inode->i_blkbits;
2233         if (disksize > i_size_read(mpd->inode))
2234                 disksize = i_size_read(mpd->inode);
2235         if (disksize > EXT4_I(mpd->inode)->i_disksize) {
2236                 ext4_update_i_disksize(mpd->inode, disksize);
2237                 return ext4_mark_inode_dirty(handle, mpd->inode);
2238         }
2239
2240         return 0;
2241 }
2242
2243 #define BH_FLAGS ((1 << BH_Uptodate) | (1 << BH_Mapped) | \
2244                 (1 << BH_Delay) | (1 << BH_Unwritten))
2245
2246 /*
2247  * mpage_add_bh_to_extent - try to add one more block to extent of blocks
2248  *
2249  * @mpd->lbh - extent of blocks
2250  * @logical - logical number of the block in the file
2251  * @bh - bh of the block (used to access block's state)
2252  *
2253  * the function is used to collect contig. blocks in same state
2254  */
2255 static void mpage_add_bh_to_extent(struct mpage_da_data *mpd,
2256                                    sector_t logical, size_t b_size,
2257                                    unsigned long b_state)
2258 {
2259         sector_t next;
2260         int nrblocks = mpd->b_size >> mpd->inode->i_blkbits;
2261
2262         /* check if thereserved journal credits might overflow */
2263         if (!(EXT4_I(mpd->inode)->i_flags & EXT4_EXTENTS_FL)) {
2264                 if (nrblocks >= EXT4_MAX_TRANS_DATA) {
2265                         /*
2266                          * With non-extent format we are limited by the journal
2267                          * credit available.  Total credit needed to insert
2268                          * nrblocks contiguous blocks is dependent on the
2269                          * nrblocks.  So limit nrblocks.
2270                          */
2271                         goto flush_it;
2272                 } else if ((nrblocks + (b_size >> mpd->inode->i_blkbits)) >
2273                                 EXT4_MAX_TRANS_DATA) {
2274                         /*
2275                          * Adding the new buffer_head would make it cross the
2276                          * allowed limit for which we have journal credit
2277                          * reserved. So limit the new bh->b_size
2278                          */
2279                         b_size = (EXT4_MAX_TRANS_DATA - nrblocks) <<
2280                                                 mpd->inode->i_blkbits;
2281                         /* we will do mpage_da_submit_io in the next loop */
2282                 }
2283         }
2284         /*
2285          * First block in the extent
2286          */
2287         if (mpd->b_size == 0) {
2288                 mpd->b_blocknr = logical;
2289                 mpd->b_size = b_size;
2290                 mpd->b_state = b_state & BH_FLAGS;
2291                 return;
2292         }
2293
2294         next = mpd->b_blocknr + nrblocks;
2295         /*
2296          * Can we merge the block to our big extent?
2297          */
2298         if (logical == next && (b_state & BH_FLAGS) == mpd->b_state) {
2299                 mpd->b_size += b_size;
2300                 return;
2301         }
2302
2303 flush_it:
2304         /*
2305          * We couldn't merge the block to our extent, so we
2306          * need to flush current  extent and start new one
2307          */
2308         if (mpage_da_map_blocks(mpd) == 0)
2309                 mpage_da_submit_io(mpd);
2310         mpd->io_done = 1;
2311         return;
2312 }
2313
2314 static int ext4_bh_delay_or_unwritten(handle_t *handle, struct buffer_head *bh)
2315 {
2316         return (buffer_delay(bh) || buffer_unwritten(bh)) && buffer_dirty(bh);
2317 }
2318
2319 /*
2320  * __mpage_da_writepage - finds extent of pages and blocks
2321  *
2322  * @page: page to consider
2323  * @wbc: not used, we just follow rules
2324  * @data: context
2325  *
2326  * The function finds extents of pages and scan them for all blocks.
2327  */
2328 static int __mpage_da_writepage(struct page *page,
2329                                 struct writeback_control *wbc, void *data)
2330 {
2331         struct mpage_da_data *mpd = data;
2332         struct inode *inode = mpd->inode;
2333         struct buffer_head *bh, *head;
2334         sector_t logical;
2335
2336         if (mpd->io_done) {
2337                 /*
2338                  * Rest of the page in the page_vec
2339                  * redirty then and skip then. We will
2340                  * try to write them again after
2341                  * starting a new transaction
2342                  */
2343                 redirty_page_for_writepage(wbc, page);
2344                 unlock_page(page);
2345                 return MPAGE_DA_EXTENT_TAIL;
2346         }
2347         /*
2348          * Can we merge this page to current extent?
2349          */
2350         if (mpd->next_page != page->index) {
2351                 /*
2352                  * Nope, we can't. So, we map non-allocated blocks
2353                  * and start IO on them using writepage()
2354                  */
2355                 if (mpd->next_page != mpd->first_page) {
2356                         if (mpage_da_map_blocks(mpd) == 0)
2357                                 mpage_da_submit_io(mpd);
2358                         /*
2359                          * skip rest of the page in the page_vec
2360                          */
2361                         mpd->io_done = 1;
2362                         redirty_page_for_writepage(wbc, page);
2363                         unlock_page(page);
2364                         return MPAGE_DA_EXTENT_TAIL;
2365                 }
2366
2367                 /*
2368                  * Start next extent of pages ...
2369                  */
2370                 mpd->first_page = page->index;
2371
2372                 /*
2373                  * ... and blocks
2374                  */
2375                 mpd->b_size = 0;
2376                 mpd->b_state = 0;
2377                 mpd->b_blocknr = 0;
2378         }
2379
2380         mpd->next_page = page->index + 1;
2381         logical = (sector_t) page->index <<
2382                   (PAGE_CACHE_SHIFT - inode->i_blkbits);
2383
2384         if (!page_has_buffers(page)) {
2385                 mpage_add_bh_to_extent(mpd, logical, PAGE_CACHE_SIZE,
2386                                        (1 << BH_Dirty) | (1 << BH_Uptodate));
2387                 if (mpd->io_done)
2388                         return MPAGE_DA_EXTENT_TAIL;
2389         } else {
2390                 /*
2391                  * Page with regular buffer heads, just add all dirty ones
2392                  */
2393                 head = page_buffers(page);
2394                 bh = head;
2395                 do {
2396                         BUG_ON(buffer_locked(bh));
2397                         /*
2398                          * We need to try to allocate
2399                          * unmapped blocks in the same page.
2400                          * Otherwise we won't make progress
2401                          * with the page in ext4_writepage
2402                          */
2403                         if (ext4_bh_delay_or_unwritten(NULL, bh)) {
2404                                 mpage_add_bh_to_extent(mpd, logical,
2405                                                        bh->b_size,
2406                                                        bh->b_state);
2407                                 if (mpd->io_done)
2408                                         return MPAGE_DA_EXTENT_TAIL;
2409                         } else if (buffer_dirty(bh) && (buffer_mapped(bh))) {
2410                                 /*
2411                                  * mapped dirty buffer. We need to update
2412                                  * the b_state because we look at
2413                                  * b_state in mpage_da_map_blocks. We don't
2414                                  * update b_size because if we find an
2415                                  * unmapped buffer_head later we need to
2416                                  * use the b_state flag of that buffer_head.
2417                                  */
2418                                 if (mpd->b_size == 0)
2419                                         mpd->b_state = bh->b_state & BH_FLAGS;
2420                         }
2421                         logical++;
2422                 } while ((bh = bh->b_this_page) != head);
2423         }
2424
2425         return 0;
2426 }
2427
2428 /*
2429  * This is a special get_blocks_t callback which is used by
2430  * ext4_da_write_begin().  It will either return mapped block or
2431  * reserve space for a single block.
2432  *
2433  * For delayed buffer_head we have BH_Mapped, BH_New, BH_Delay set.
2434  * We also have b_blocknr = -1 and b_bdev initialized properly
2435  *
2436  * For unwritten buffer_head we have BH_Mapped, BH_New, BH_Unwritten set.
2437  * We also have b_blocknr = physicalblock mapping unwritten extent and b_bdev
2438  * initialized properly.
2439  */
2440 static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
2441                                   struct buffer_head *bh_result, int create)
2442 {
2443         int ret = 0;
2444         sector_t invalid_block = ~((sector_t) 0xffff);
2445
2446         if (invalid_block < ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es))
2447                 invalid_block = ~0;
2448
2449         BUG_ON(create == 0);
2450         BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
2451
2452         /*
2453          * first, we need to know whether the block is allocated already
2454          * preallocated blocks are unmapped but should treated
2455          * the same as allocated blocks.
2456          */
2457         ret = ext4_get_blocks(NULL, inode, iblock, 1,  bh_result, 0);
2458         if ((ret == 0) && !buffer_delay(bh_result)) {
2459                 /* the block isn't (pre)allocated yet, let's reserve space */
2460                 /*
2461                  * XXX: __block_prepare_write() unmaps passed block,
2462                  * is it OK?
2463                  */
2464                 ret = ext4_da_reserve_space(inode, 1);
2465                 if (ret)
2466                         /* not enough space to reserve */
2467                         return ret;
2468
2469                 map_bh(bh_result, inode->i_sb, invalid_block);
2470                 set_buffer_new(bh_result);
2471                 set_buffer_delay(bh_result);
2472         } else if (ret > 0) {
2473                 bh_result->b_size = (ret << inode->i_blkbits);
2474                 if (buffer_unwritten(bh_result)) {
2475                         /* A delayed write to unwritten bh should
2476                          * be marked new and mapped.  Mapped ensures
2477                          * that we don't do get_block multiple times
2478                          * when we write to the same offset and new
2479                          * ensures that we do proper zero out for
2480                          * partial write.
2481                          */
2482                         set_buffer_new(bh_result);
2483                         set_buffer_mapped(bh_result);
2484                 }
2485                 ret = 0;
2486         }
2487
2488         return ret;
2489 }
2490
2491 /*
2492  * This function is used as a standard get_block_t calback function
2493  * when there is no desire to allocate any blocks.  It is used as a
2494  * callback function for block_prepare_write(), nobh_writepage(), and
2495  * block_write_full_page().  These functions should only try to map a
2496  * single block at a time.
2497  *
2498  * Since this function doesn't do block allocations even if the caller
2499  * requests it by passing in create=1, it is critically important that
2500  * any caller checks to make sure that any buffer heads are returned
2501  * by this function are either all already mapped or marked for
2502  * delayed allocation before calling nobh_writepage() or
2503  * block_write_full_page().  Otherwise, b_blocknr could be left
2504  * unitialized, and the page write functions will be taken by
2505  * surprise.
2506  */
2507 static int noalloc_get_block_write(struct inode *inode, sector_t iblock,
2508                                    struct buffer_head *bh_result, int create)
2509 {
2510         int ret = 0;
2511         unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
2512
2513         BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
2514
2515         /*
2516          * we don't want to do block allocation in writepage
2517          * so call get_block_wrap with create = 0
2518          */
2519         ret = ext4_get_blocks(NULL, inode, iblock, max_blocks, bh_result, 0);
2520         if (ret > 0) {
2521                 bh_result->b_size = (ret << inode->i_blkbits);
2522                 ret = 0;
2523         }
2524         return ret;
2525 }
2526
2527 static int bget_one(handle_t *handle, struct buffer_head *bh)
2528 {
2529         get_bh(bh);
2530         return 0;
2531 }
2532
2533 static int bput_one(handle_t *handle, struct buffer_head *bh)
2534 {
2535         put_bh(bh);
2536         return 0;
2537 }
2538
2539 static int __ext4_journalled_writepage(struct page *page,
2540                                        struct writeback_control *wbc,
2541                                        unsigned int len)
2542 {
2543         struct address_space *mapping = page->mapping;
2544         struct inode *inode = mapping->host;
2545         struct buffer_head *page_bufs;
2546         handle_t *handle = NULL;
2547         int ret = 0;
2548         int err;
2549
2550         page_bufs = page_buffers(page);
2551         BUG_ON(!page_bufs);
2552         walk_page_buffers(handle, page_bufs, 0, len, NULL, bget_one);
2553         /* As soon as we unlock the page, it can go away, but we have
2554          * references to buffers so we are safe */
2555         unlock_page(page);
2556
2557         handle = ext4_journal_start(inode, ext4_writepage_trans_blocks(inode));
2558         if (IS_ERR(handle)) {
2559                 ret = PTR_ERR(handle);
2560                 goto out;
2561         }
2562
2563         ret = walk_page_buffers(handle, page_bufs, 0, len, NULL,
2564                                 do_journal_get_write_access);
2565
2566         err = walk_page_buffers(handle, page_bufs, 0, len, NULL,
2567                                 write_end_fn);
2568         if (ret == 0)
2569                 ret = err;
2570         err = ext4_journal_stop(handle);
2571         if (!ret)
2572                 ret = err;
2573
2574         walk_page_buffers(handle, page_bufs, 0, len, NULL, bput_one);
2575         EXT4_I(inode)->i_state |= EXT4_STATE_JDATA;
2576 out:
2577         return ret;
2578 }
2579
2580 /*
2581  * Note that we don't need to start a transaction unless we're journaling data
2582  * because we should have holes filled from ext4_page_mkwrite(). We even don't
2583  * need to file the inode to the transaction's list in ordered mode because if
2584  * we are writing back data added by write(), the inode is already there and if
2585  * we are writing back data modified via mmap(), noone guarantees in which
2586  * transaction the data will hit the disk. In case we are journaling data, we
2587  * cannot start transaction directly because transaction start ranks above page
2588  * lock so we have to do some magic.
2589  *
2590  * This function can get called via...
2591  *   - ext4_da_writepages after taking page lock (have journal handle)
2592  *   - journal_submit_inode_data_buffers (no journal handle)
2593  *   - shrink_page_list via pdflush (no journal handle)
2594  *   - grab_page_cache when doing write_begin (have journal handle)
2595  *
2596  * We don't do any block allocation in this function. If we have page with
2597  * multiple blocks we need to write those buffer_heads that are mapped. This
2598  * is important for mmaped based write. So if we do with blocksize 1K
2599  * truncate(f, 1024);
2600  * a = mmap(f, 0, 4096);
2601  * a[0] = 'a';
2602  * truncate(f, 4096);
2603  * we have in the page first buffer_head mapped via page_mkwrite call back
2604  * but other bufer_heads would be unmapped but dirty(dirty done via the
2605  * do_wp_page). So writepage should write the first block. If we modify
2606  * the mmap area beyond 1024 we will again get a page_fault and the
2607  * page_mkwrite callback will do the block allocation and mark the
2608  * buffer_heads mapped.
2609  *
2610  * We redirty the page if we have any buffer_heads that is either delay or
2611  * unwritten in the page.
2612  *
2613  * We can get recursively called as show below.
2614  *
2615  *      ext4_writepage() -> kmalloc() -> __alloc_pages() -> page_launder() ->
2616  *              ext4_writepage()
2617  *
2618  * But since we don't do any block allocation we should not deadlock.
2619  * Page also have the dirty flag cleared so we don't get recurive page_lock.
2620  */
2621 static int ext4_writepage(struct page *page,
2622                           struct writeback_control *wbc)
2623 {
2624         int ret = 0;
2625         loff_t size;
2626         unsigned int len;
2627         struct buffer_head *page_bufs;
2628         struct inode *inode = page->mapping->host;
2629
2630         trace_ext4_writepage(inode, page);
2631         size = i_size_read(inode);
2632         if (page->index == size >> PAGE_CACHE_SHIFT)
2633                 len = size & ~PAGE_CACHE_MASK;
2634         else
2635                 len = PAGE_CACHE_SIZE;
2636
2637         if (page_has_buffers(page)) {
2638                 page_bufs = page_buffers(page);
2639                 if (walk_page_buffers(NULL, page_bufs, 0, len, NULL,
2640                                         ext4_bh_delay_or_unwritten)) {
2641                         /*
2642                          * We don't want to do  block allocation
2643                          * So redirty the page and return
2644                          * We may reach here when we do a journal commit
2645                          * via journal_submit_inode_data_buffers.
2646                          * If we don't have mapping block we just ignore
2647                          * them. We can also reach here via shrink_page_list
2648                          */
2649                         redirty_page_for_writepage(wbc, page);
2650                         unlock_page(page);
2651                         return 0;
2652                 }
2653         } else {
2654                 /*
2655                  * The test for page_has_buffers() is subtle:
2656                  * We know the page is dirty but it lost buffers. That means
2657                  * that at some moment in time after write_begin()/write_end()
2658                  * has been called all buffers have been clean and thus they
2659                  * must have been written at least once. So they are all
2660                  * mapped and we can happily proceed with mapping them
2661                  * and writing the page.
2662                  *
2663                  * Try to initialize the buffer_heads and check whether
2664                  * all are mapped and non delay. We don't want to
2665                  * do block allocation here.
2666                  */
2667                 ret = block_prepare_write(page, 0, len,
2668                                           noalloc_get_block_write);
2669                 if (!ret) {
2670                         page_bufs = page_buffers(page);
2671                         /* check whether all are mapped and non delay */
2672                         if (walk_page_buffers(NULL, page_bufs, 0, len, NULL,
2673                                                 ext4_bh_delay_or_unwritten)) {
2674                                 redirty_page_for_writepage(wbc, page);
2675                                 unlock_page(page);
2676                                 return 0;
2677                         }
2678                 } else {
2679                         /*
2680                          * We can't do block allocation here
2681                          * so just redity the page and unlock
2682                          * and return
2683                          */
2684                         redirty_page_for_writepage(wbc, page);
2685                         unlock_page(page);
2686                         return 0;
2687                 }
2688                 /* now mark the buffer_heads as dirty and uptodate */
2689                 block_commit_write(page, 0, len);
2690         }
2691
2692         if (PageChecked(page) && ext4_should_journal_data(inode)) {
2693                 /*
2694                  * It's mmapped pagecache.  Add buffers and journal it.  There
2695                  * doesn't seem much point in redirtying the page here.
2696                  */
2697                 ClearPageChecked(page);
2698                 return __ext4_journalled_writepage(page, wbc, len);
2699         }
2700
2701         if (test_opt(inode->i_sb, NOBH) && ext4_should_writeback_data(inode))
2702                 ret = nobh_writepage(page, noalloc_get_block_write, wbc);
2703         else
2704                 ret = block_write_full_page(page, noalloc_get_block_write,
2705                                             wbc);
2706
2707         return ret;
2708 }
2709
2710 /*
2711  * This is called via ext4_da_writepages() to
2712  * calulate the total number of credits to reserve to fit
2713  * a single extent allocation into a single transaction,
2714  * ext4_da_writpeages() will loop calling this before
2715  * the block allocation.
2716  */
2717
2718 static int ext4_da_writepages_trans_blocks(struct inode *inode)
2719 {
2720         int max_blocks = EXT4_I(inode)->i_reserved_data_blocks;
2721
2722         /*
2723          * With non-extent format the journal credit needed to
2724          * insert nrblocks contiguous block is dependent on
2725          * number of contiguous block. So we will limit
2726          * number of contiguous block to a sane value
2727          */
2728         if (!(inode->i_flags & EXT4_EXTENTS_FL) &&
2729             (max_blocks > EXT4_MAX_TRANS_DATA))
2730                 max_blocks = EXT4_MAX_TRANS_DATA;
2731
2732         return ext4_chunk_trans_blocks(inode, max_blocks);
2733 }
2734
2735 static int ext4_da_writepages(struct address_space *mapping,
2736                               struct writeback_control *wbc)
2737 {
2738         pgoff_t index;
2739         int range_whole = 0;
2740         handle_t *handle = NULL;
2741         struct mpage_da_data mpd;
2742         struct inode *inode = mapping->host;
2743         int no_nrwrite_index_update;
2744         int pages_written = 0;
2745         long pages_skipped;
2746         int range_cyclic, cycled = 1, io_done = 0;
2747         int needed_blocks, ret = 0, nr_to_writebump = 0;
2748         loff_t range_start = wbc->range_start;
2749         struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);
2750
2751         trace_ext4_da_writepages(inode, wbc);
2752
2753         /*
2754          * No pages to write? This is mainly a kludge to avoid starting
2755          * a transaction for special inodes like journal inode on last iput()
2756          * because that could violate lock ordering on umount
2757          */
2758         if (!mapping->nrpages || !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
2759                 return 0;
2760
2761         /*
2762          * If the filesystem has aborted, it is read-only, so return
2763          * right away instead of dumping stack traces later on that
2764          * will obscure the real source of the problem.  We test
2765          * EXT4_MF_FS_ABORTED instead of sb->s_flag's MS_RDONLY because
2766          * the latter could be true if the filesystem is mounted
2767          * read-only, and in that case, ext4_da_writepages should
2768          * *never* be called, so if that ever happens, we would want
2769          * the stack trace.
2770          */
2771         if (unlikely(sbi->s_mount_flags & EXT4_MF_FS_ABORTED))
2772                 return -EROFS;
2773
2774         /*
2775          * Make sure nr_to_write is >= sbi->s_mb_stream_request
2776          * This make sure small files blocks are allocated in
2777          * single attempt. This ensure that small files
2778          * get less fragmented.
2779          */
2780         if (wbc->nr_to_write < sbi->s_mb_stream_request) {
2781                 nr_to_writebump = sbi->s_mb_stream_request - wbc->nr_to_write;
2782                 wbc->nr_to_write = sbi->s_mb_stream_request;
2783         }
2784         if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
2785                 range_whole = 1;
2786
2787         range_cyclic = wbc->range_cyclic;
2788         if (wbc->range_cyclic) {
2789                 index = mapping->writeback_index;
2790                 if (index)
2791                         cycled = 0;
2792                 wbc->range_start = index << PAGE_CACHE_SHIFT;
2793                 wbc->range_end  = LLONG_MAX;
2794                 wbc->range_cyclic = 0;
2795         } else
2796                 index = wbc->range_start >> PAGE_CACHE_SHIFT;
2797
2798         mpd.wbc = wbc;
2799         mpd.inode = mapping->host;
2800
2801         /*
2802          * we don't want write_cache_pages to update
2803          * nr_to_write and writeback_index
2804          */
2805         no_nrwrite_index_update = wbc->no_nrwrite_index_update;
2806         wbc->no_nrwrite_index_update = 1;
2807         pages_skipped = wbc->pages_skipped;
2808
2809 retry:
2810         while (!ret && wbc->nr_to_write > 0) {
2811
2812                 /*
2813                  * we  insert one extent at a time. So we need
2814                  * credit needed for single extent allocation.
2815                  * journalled mode is currently not supported
2816                  * by delalloc
2817                  */
2818                 BUG_ON(ext4_should_journal_data(inode));
2819                 needed_blocks = ext4_da_writepages_trans_blocks(inode);
2820
2821                 /* start a new transaction*/
2822                 handle = ext4_journal_start(inode, needed_blocks);
2823                 if (IS_ERR(handle)) {
2824                         ret = PTR_ERR(handle);
2825                         ext4_msg(inode->i_sb, KERN_CRIT, "%s: jbd2_start: "
2826                                "%ld pages, ino %lu; err %d\n", __func__,
2827                                 wbc->nr_to_write, inode->i_ino, ret);
2828                         goto out_writepages;
2829                 }
2830
2831                 /*
2832                  * Now call __mpage_da_writepage to find the next
2833                  * contiguous region of logical blocks that need
2834                  * blocks to be allocated by ext4.  We don't actually
2835                  * submit the blocks for I/O here, even though
2836                  * write_cache_pages thinks it will, and will set the
2837                  * pages as clean for write before calling
2838                  * __mpage_da_writepage().
2839                  */
2840                 mpd.b_size = 0;
2841                 mpd.b_state = 0;
2842                 mpd.b_blocknr = 0;
2843                 mpd.first_page = 0;
2844                 mpd.next_page = 0;
2845                 mpd.io_done = 0;
2846                 mpd.pages_written = 0;
2847                 mpd.retval = 0;
2848                 ret = write_cache_pages(mapping, wbc, __mpage_da_writepage,
2849                                         &mpd);
2850                 /*
2851                  * If we have a contigous extent of pages and we
2852                  * haven't done the I/O yet, map the blocks and submit
2853                  * them for I/O.
2854                  */
2855                 if (!mpd.io_done && mpd.next_page != mpd.first_page) {
2856                         if (mpage_da_map_blocks(&mpd) == 0)
2857                                 mpage_da_submit_io(&mpd);
2858                         mpd.io_done = 1;
2859                         ret = MPAGE_DA_EXTENT_TAIL;
2860                 }
2861                 trace_ext4_da_write_pages(inode, &mpd);
2862                 wbc->nr_to_write -= mpd.pages_written;
2863
2864                 ext4_journal_stop(handle);
2865
2866                 if ((mpd.retval == -ENOSPC) && sbi->s_journal) {
2867                         /* commit the transaction which would
2868                          * free blocks released in the transaction
2869                          * and try again
2870                          */
2871                         jbd2_journal_force_commit_nested(sbi->s_journal);
2872                         wbc->pages_skipped = pages_skipped;
2873                         ret = 0;
2874                 } else if (ret == MPAGE_DA_EXTENT_TAIL) {
2875                         /*
2876                          * got one extent now try with
2877                          * rest of the pages
2878                          */
2879                         pages_written += mpd.pages_written;
2880                         wbc->pages_skipped = pages_skipped;
2881                         ret = 0;
2882                         io_done = 1;
2883                 } else if (wbc->nr_to_write)
2884                         /*
2885                          * There is no more writeout needed
2886                          * or we requested for a noblocking writeout
2887                          * and we found the device congested
2888                          */
2889                         break;
2890         }
2891         if (!io_done && !cycled) {
2892                 cycled = 1;
2893                 index = 0;
2894                 wbc->range_start = index << PAGE_CACHE_SHIFT;
2895                 wbc->range_end  = mapping->writeback_index - 1;
2896                 goto retry;
2897         }
2898         if (pages_skipped != wbc->pages_skipped)
2899                 ext4_msg(inode->i_sb, KERN_CRIT,
2900                          "This should not happen leaving %s "
2901                          "with nr_to_write = %ld ret = %d\n",
2902                          __func__, wbc->nr_to_write, ret);
2903
2904         /* Update index */
2905         index += pages_written;
2906         wbc->range_cyclic = range_cyclic;
2907         if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
2908                 /*
2909                  * set the writeback_index so that range_cyclic
2910                  * mode will write it back later
2911                  */
2912                 mapping->writeback_index = index;
2913
2914 out_writepages:
2915         if (!no_nrwrite_index_update)
2916                 wbc->no_nrwrite_index_update = 0;
2917         wbc->nr_to_write -= nr_to_writebump;
2918         wbc->range_start = range_start;
2919         trace_ext4_da_writepages_result(inode, wbc, ret, pages_written);
2920         return ret;
2921 }
2922
2923 #define FALL_BACK_TO_NONDELALLOC 1
2924 static int ext4_nonda_switch(struct super_block *sb)
2925 {
2926         s64 free_blocks, dirty_blocks;
2927         struct ext4_sb_info *sbi = EXT4_SB(sb);
2928
2929         /*
2930          * switch to non delalloc mode if we are running low
2931          * on free block. The free block accounting via percpu
2932          * counters can get slightly wrong with percpu_counter_batch getting
2933          * accumulated on each CPU without updating global counters
2934          * Delalloc need an accurate free block accounting. So switch
2935          * to non delalloc when we are near to error range.
2936          */
2937         free_blocks  = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
2938         dirty_blocks = percpu_counter_read_positive(&sbi->s_dirtyblocks_counter);
2939         if (2 * free_blocks < 3 * dirty_blocks ||
2940                 free_blocks < (dirty_blocks + EXT4_FREEBLOCKS_WATERMARK)) {
2941                 /*
2942                  * free block count is less that 150% of dirty blocks
2943                  * or free blocks is less that watermark
2944                  */
2945                 return 1;
2946         }
2947         return 0;
2948 }
2949
2950 static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
2951                                loff_t pos, unsigned len, unsigned flags,
2952                                struct page **pagep, void **fsdata)
2953 {
2954         int ret, retries = 0;
2955         struct page *page;
2956         pgoff_t index;
2957         unsigned from, to;
2958         struct inode *inode = mapping->host;
2959         handle_t *handle;
2960
2961         index = pos >> PAGE_CACHE_SHIFT;
2962         from = pos & (PAGE_CACHE_SIZE - 1);
2963         to = from + len;
2964
2965         if (ext4_nonda_switch(inode->i_sb)) {
2966                 *fsdata = (void *)FALL_BACK_TO_NONDELALLOC;
2967                 return ext4_write_begin(file, mapping, pos,
2968                                         len, flags, pagep, fsdata);
2969         }
2970         *fsdata = (void *)0;
2971         trace_ext4_da_write_begin(inode, pos, len, flags);
2972 retry:
2973         /*
2974          * With delayed allocation, we don't log the i_disksize update
2975          * if there is delayed block allocation. But we still need
2976          * to journalling the i_disksize update if writes to the end
2977          * of file which has an already mapped buffer.
2978          */
2979         handle = ext4_journal_start(inode, 1);
2980         if (IS_ERR(handle)) {
2981                 ret = PTR_ERR(handle);
2982                 goto out;
2983         }
2984         /* We cannot recurse into the filesystem as the transaction is already
2985          * started */
2986         flags |= AOP_FLAG_NOFS;
2987
2988         page = grab_cache_page_write_begin(mapping, index, flags);
2989         if (!page) {
2990                 ext4_journal_stop(handle);
2991                 ret = -ENOMEM;
2992                 goto out;
2993         }
2994         *pagep = page;
2995
2996         ret = block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
2997                                 ext4_da_get_block_prep);
2998         if (ret < 0) {
2999                 unlock_page(page);
3000                 ext4_journal_stop(handle);
3001                 page_cache_release(page);
3002                 /*
3003                  * block_write_begin may have instantiated a few blocks
3004                  * outside i_size.  Trim these off again. Don't need
3005                  * i_size_read because we hold i_mutex.
3006                  */
3007                 if (pos + len > inode->i_size)
3008                         ext4_truncate(inode);
3009         }
3010
3011         if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
3012                 goto retry;
3013 out:
3014         return ret;
3015 }
3016
3017 /*
3018  * Check if we should update i_disksize
3019  * when write to the end of file but not require block allocation
3020  */
3021 static int ext4_da_should_update_i_disksize(struct page *page,
3022                                             unsigned long offset)
3023 {
3024         struct buffer_head *bh;
3025         struct inode *inode = page->mapping->host;
3026         unsigned int idx;
3027         int i;
3028
3029         bh = page_buffers(page);
3030         idx = offset >> inode->i_blkbits;
3031
3032         for (i = 0; i < idx; i++)
3033                 bh = bh->b_this_page;
3034
3035         if (!buffer_mapped(bh) || (buffer_delay(bh)) || buffer_unwritten(bh))
3036                 return 0;
3037         return 1;
3038 }
3039
3040 static int ext4_da_write_end(struct file *file,
3041                              struct address_space *mapping,
3042                              loff_t pos, unsigned len, unsigned copied,
3043                              struct page *page, void *fsdata)
3044 {
3045         struct inode *inode = mapping->host;
3046         int ret = 0, ret2;
3047         handle_t *handle = ext4_journal_current_handle();
3048         loff_t new_i_size;
3049         unsigned long start, end;
3050         int write_mode = (int)(unsigned long)fsdata;
3051
3052         if (write_mode == FALL_BACK_TO_NONDELALLOC) {
3053                 if (ext4_should_order_data(inode)) {
3054                         return ext4_ordered_write_end(file, mapping, pos,
3055                                         len, copied, page, fsdata);
3056                 } else if (ext4_should_writeback_data(inode)) {
3057                         return ext4_writeback_write_end(file, mapping, pos,
3058                                         len, copied, page, fsdata);
3059                 } else {
3060                         BUG();
3061                 }
3062         }
3063
3064         trace_ext4_da_write_end(inode, pos, len, copied);
3065         start = pos & (PAGE_CACHE_SIZE - 1);
3066         end = start + copied - 1;
3067
3068         /*
3069          * generic_write_end() will run mark_inode_dirty() if i_size
3070          * changes.  So let's piggyback the i_disksize mark_inode_dirty
3071          * into that.
3072          */
3073
3074         new_i_size = pos + copied;
3075         if (new_i_size > EXT4_I(inode)->i_disksize) {
3076                 if (ext4_da_should_update_i_disksize(page, end)) {
3077                         down_write(&EXT4_I(inode)->i_data_sem);
3078                         if (new_i_size > EXT4_I(inode)->i_disksize) {
3079                                 /*
3080                                  * Updating i_disksize when extending file
3081                                  * without needing block allocation
3082                                  */
3083                                 if (ext4_should_order_data(inode))
3084                                         ret = ext4_jbd2_file_inode(handle,
3085                                                                    inode);
3086
3087                                 EXT4_I(inode)->i_disksize = new_i_size;
3088                         }
3089                         up_write(&EXT4_I(inode)->i_data_sem);
3090                         /* We need to mark inode dirty even if
3091                          * new_i_size is less that inode->i_size
3092                          * bu greater than i_disksize.(hint delalloc)
3093                          */
3094                         ext4_mark_inode_dirty(handle, inode);
3095                 }
3096         }
3097         ret2 = generic_write_end(file, mapping, pos, len, copied,
3098                                                         page, fsdata);
3099         copied = ret2;
3100         if (ret2 < 0)
3101                 ret = ret2;
3102         ret2 = ext4_journal_stop(handle);
3103         if (!ret)
3104                 ret = ret2;
3105
3106         return ret ? ret : copied;
3107 }
3108
3109 static void ext4_da_invalidatepage(struct page *page, unsigned long offset)
3110 {
3111         /*
3112          * Drop reserved blocks
3113          */
3114         BUG_ON(!PageLocked(page));
3115         if (!page_has_buffers(page))
3116                 goto out;
3117
3118         ext4_da_page_release_reservation(page, offset);
3119
3120 out:
3121         ext4_invalidatepage(page, offset);
3122
3123         return;
3124 }
3125
3126 /*
3127  * Force all delayed allocation blocks to be allocated for a given inode.
3128  */
3129 int ext4_alloc_da_blocks(struct inode *inode)
3130 {
3131         trace_ext4_alloc_da_blocks(inode);
3132
3133         if (!EXT4_I(inode)->i_reserved_data_blocks &&
3134             !EXT4_I(inode)->i_reserved_meta_blocks)
3135                 return 0;
3136
3137         /*
3138          * We do something simple for now.  The filemap_flush() will
3139          * also start triggering a write of the data blocks, which is
3140          * not strictly speaking necessary (and for users of
3141          * laptop_mode, not even desirable).  However, to do otherwise
3142          * would require replicating code paths in:
3143          *
3144          * ext4_da_writepages() ->
3145          *    write_cache_pages() ---> (via passed in callback function)
3146          *        __mpage_da_writepage() -->
3147          *           mpage_add_bh_to_extent()
3148          *           mpage_da_map_blocks()
3149          *
3150          * The problem is that write_cache_pages(), located in
3151          * mm/page-writeback.c, marks pages clean in preparation for
3152          * doing I/O, which is not desirable if we're not planning on
3153          * doing I/O at all.
3154          *
3155          * We could call write_cache_pages(), and then redirty all of
3156          * the pages by calling redirty_page_for_writeback() but that
3157          * would be ugly in the extreme.  So instead we would need to
3158          * replicate parts of the code in the above functions,
3159          * simplifying them becuase we wouldn't actually intend to
3160          * write out the pages, but rather only collect contiguous
3161          * logical block extents, call the multi-block allocator, and
3162          * then update the buffer heads with the block allocations.
3163          *
3164          * For now, though, we'll cheat by calling filemap_flush(),
3165          * which will map the blocks, and start the I/O, but not
3166          * actually wait for the I/O to complete.
3167          */
3168         return filemap_flush(inode->i_mapping);
3169 }
3170
3171 /*
3172  * bmap() is special.  It gets used by applications such as lilo and by
3173  * the swapper to find the on-disk block of a specific piece of data.
3174  *
3175  * Naturally, this is dangerous if the block concerned is still in the
3176  * journal.  If somebody makes a swapfile on an ext4 data-journaling
3177  * filesystem and enables swap, then they may get a nasty shock when the
3178  * data getting swapped to that swapfile suddenly gets overwritten by
3179  * the original zero's written out previously to the journal and
3180  * awaiting writeback in the kernel's buffer cache.
3181  *
3182  * So, if we see any bmap calls here on a modified, data-journaled file,
3183  * take extra steps to flush any blocks which might be in the cache.
3184  */
3185 static sector_t ext4_bmap(struct address_space *mapping, sector_t block)
3186 {
3187         struct inode *inode = mapping->host;
3188         journal_t *journal;
3189         int err;
3190
3191         if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY) &&
3192                         test_opt(inode->i_sb, DELALLOC)) {
3193                 /*
3194                  * With delalloc we want to sync the file
3195                  * so that we can make sure we allocate
3196                  * blocks for file
3197                  */
3198                 filemap_write_and_wait(mapping);
3199         }
3200
3201         if (EXT4_JOURNAL(inode) && EXT4_I(inode)->i_state & EXT4_STATE_JDATA) {
3202                 /*
3203                  * This is a REALLY heavyweight approach, but the use of
3204                  * bmap on dirty files is expected to be extremely rare:
3205                  * only if we run lilo or swapon on a freshly made file
3206                  * do we expect this to happen.
3207                  *
3208                  * (bmap requires CAP_SYS_RAWIO so this does not
3209                  * represent an unprivileged user DOS attack --- we'd be
3210                  * in trouble if mortal users could trigger this path at
3211                  * will.)
3212                  *
3213                  * NB. EXT4_STATE_JDATA is not set on files other than
3214                  * regular files.  If somebody wants to bmap a directory
3215                  * or symlink and gets confused because the buffer
3216                  * hasn't yet been flushed to disk, they deserve
3217                  * everything they get.
3218                  */
3219
3220                 EXT4_I(inode)->i_state &= ~EXT4_STATE_JDATA;
3221                 journal = EXT4_JOURNAL(inode);
3222                 jbd2_journal_lock_updates(journal);
3223                 err = jbd2_journal_flush(journal);
3224                 jbd2_journal_unlock_updates(journal);
3225
3226                 if (err)
3227                         return 0;
3228         }
3229
3230         return generic_block_bmap(mapping, block, ext4_get_block);
3231 }
3232
3233 static int ext4_readpage(struct file *file, struct page *page)
3234 {
3235         return mpage_readpage(page, ext4_get_block);
3236 }
3237
3238 static int
3239 ext4_readpages(struct file *file, struct address_space *mapping,
3240                 struct list_head *pages, unsigned nr_pages)
3241 {
3242         return mpage_readpages(mapping, pages, nr_pages, ext4_get_block);
3243 }
3244
3245 static void ext4_invalidatepage(struct page *page, unsigned long offset)
3246 {
3247         journal_t *journal = EXT4_JOURNAL(page->mapping->host);
3248
3249         /*
3250          * If it's a full truncate we just forget about the pending dirtying
3251          */
3252         if (offset == 0)
3253                 ClearPageChecked(page);
3254
3255         if (journal)
3256                 jbd2_journal_invalidatepage(journal, page, offset);
3257         else
3258                 block_invalidatepage(page, offset);
3259 }
3260
3261 static int ext4_releasepage(struct page *page, gfp_t wait)
3262 {
3263         journal_t *journal = EXT4_JOURNAL(page->mapping->host);
3264
3265         WARN_ON(PageChecked(page));
3266         if (!page_has_buffers(page))
3267                 return 0;
3268         if (journal)
3269                 return jbd2_journal_try_to_free_buffers(journal, page, wait);
3270         else
3271                 return try_to_free_buffers(page);
3272 }
3273
3274 /*
3275  * If the O_DIRECT write will extend the file then add this inode to the
3276  * orphan list.  So recovery will truncate it back to the original size
3277  * if the machine crashes during the write.
3278  *
3279  * If the O_DIRECT write is intantiating holes inside i_size and the machine
3280  * crashes then stale disk data _may_ be exposed inside the file. But current
3281  * VFS code falls back into buffered path in that case so we are safe.
3282  */
3283 static ssize_t ext4_direct_IO(int rw, struct kiocb *iocb,
3284                               const struct iovec *iov, loff_t offset,
3285                               unsigned long nr_segs)
3286 {
3287         struct file *file = iocb->ki_filp;
3288         struct inode *inode = file->f_mapping->host;
3289         struct ext4_inode_info *ei = EXT4_I(inode);
3290         handle_t *handle;
3291         ssize_t ret;
3292         int orphan = 0;
3293         size_t count = iov_length(iov, nr_segs);
3294
3295         if (rw == WRITE) {
3296                 loff_t final_size = offset + count;
3297
3298                 if (final_size > inode->i_size) {
3299                         /* Credits for sb + inode write */
3300                         handle = ext4_journal_start(inode, 2);
3301                         if (IS_ERR(handle)) {
3302                                 ret = PTR_ERR(handle);
3303                                 goto out;
3304                         }
3305                         ret = ext4_orphan_add(handle, inode);
3306                         if (ret) {
3307                                 ext4_journal_stop(handle);
3308                                 goto out;
3309                         }
3310                         orphan = 1;
3311                         ei->i_disksize = inode->i_size;
3312                         ext4_journal_stop(handle);
3313                 }
3314         }
3315
3316         ret = blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
3317                                  offset, nr_segs,
3318                                  ext4_get_block, NULL);
3319
3320         if (orphan) {
3321                 int err;
3322
3323                 /* Credits for sb + inode write */
3324                 handle = ext4_journal_start(inode, 2);
3325                 if (IS_ERR(handle)) {
3326                         /* This is really bad luck. We've written the data
3327                          * but cannot extend i_size. Bail out and pretend
3328                          * the write failed... */
3329                         ret = PTR_ERR(handle);
3330                         goto out;
3331                 }
3332                 if (inode->i_nlink)
3333                         ext4_orphan_del(handle, inode);
3334                 if (ret > 0) {
3335                         loff_t end = offset + ret;
3336                         if (end > inode->i_size) {
3337                                 ei->i_disksize = end;
3338                                 i_size_write(inode, end);
3339                                 /*
3340                                  * We're going to return a positive `ret'
3341                                  * here due to non-zero-length I/O, so there's
3342                                  * no way of reporting error returns from
3343                                  * ext4_mark_inode_dirty() to userspace.  So
3344                                  * ignore it.
3345                                  */
3346                                 ext4_mark_inode_dirty(handle, inode);
3347                         }
3348                 }
3349                 err = ext4_journal_stop(handle);
3350                 if (ret == 0)
3351                         ret = err;
3352         }
3353 out:
3354         return ret;
3355 }
3356
3357 /*
3358  * Pages can be marked dirty completely asynchronously from ext4's journalling
3359  * activity.  By filemap_sync_pte(), try_to_unmap_one(), etc.  We cannot do
3360  * much here because ->set_page_dirty is called under VFS locks.  The page is
3361  * not necessarily locked.
3362  *
3363  * We cannot just dirty the page and leave attached buffers clean, because the
3364  * buffers' dirty state is "definitive".  We cannot just set the buffers dirty
3365  * or jbddirty because all the journalling code will explode.
3366  *
3367  * So what we do is to mark the page "pending dirty" and next time writepage
3368  * is called, propagate that into the buffers appropriately.
3369  */
3370 static int ext4_journalled_set_page_dirty(struct page *page)
3371 {
3372         SetPageChecked(page);
3373         return __set_page_dirty_nobuffers(page);
3374 }
3375
3376 static const struct address_space_operations ext4_ordered_aops = {
3377         .readpage               = ext4_readpage,
3378         .readpages              = ext4_readpages,
3379         .writepage              = ext4_writepage,
3380         .sync_page              = block_sync_page,
3381         .write_begin            = ext4_write_begin,
3382         .write_end              = ext4_ordered_write_end,
3383         .bmap                   = ext4_bmap,
3384         .invalidatepage         = ext4_invalidatepage,
3385         .releasepage            = ext4_releasepage,
3386         .direct_IO              = ext4_direct_IO,
3387         .migratepage            = buffer_migrate_page,
3388         .is_partially_uptodate  = block_is_partially_uptodate,
3389         .error_remove_page      = generic_error_remove_page,
3390 };
3391
3392 static const struct address_space_operations ext4_writeback_aops = {
3393         .readpage               = ext4_readpage,
3394         .readpages              = ext4_readpages,
3395         .writepage              = ext4_writepage,
3396         .sync_page              = block_sync_page,
3397         .write_begin            = ext4_write_begin,
3398         .write_end              = ext4_writeback_write_end,
3399         .bmap                   = ext4_bmap,
3400         .invalidatepage         = ext4_invalidatepage,
3401         .releasepage            = ext4_releasepage,
3402         .direct_IO              = ext4_direct_IO,
3403         .migratepage            = buffer_migrate_page,
3404         .is_partially_uptodate  = block_is_partially_uptodate,
3405         .error_remove_page      = generic_error_remove_page,
3406 };
3407
3408 static const struct address_space_operations ext4_journalled_aops = {
3409         .readpage               = ext4_readpage,
3410         .readpages              = ext4_readpages,
3411         .writepage              = ext4_writepage,
3412         .sync_page              = block_sync_page,
3413         .write_begin            = ext4_write_begin,
3414         .write_end              = ext4_journalled_write_end,
3415         .set_page_dirty         = ext4_journalled_set_page_dirty,
3416         .bmap                   = ext4_bmap,
3417         .invalidatepage         = ext4_invalidatepage,
3418         .releasepage            = ext4_releasepage,
3419         .is_partially_uptodate  = block_is_partially_uptodate,
3420         .error_remove_page      = generic_error_remove_page,
3421 };
3422
3423 static const struct address_space_operations ext4_da_aops = {
3424         .readpage               = ext4_readpage,
3425         .readpages              = ext4_readpages,
3426         .writepage              = ext4_writepage,
3427         .writepages             = ext4_da_writepages,
3428         .sync_page              = block_sync_page,
3429         .write_begin            = ext4_da_write_begin,
3430         .write_end              = ext4_da_write_end,
3431         .bmap                   = ext4_bmap,
3432         .invalidatepage         = ext4_da_invalidatepage,
3433         .releasepage            = ext4_releasepage,
3434         .direct_IO              = ext4_direct_IO,
3435         .migratepage            = buffer_migrate_page,
3436         .is_partially_uptodate  = block_is_partially_uptodate,
3437         .error_remove_page      = generic_error_remove_page,
3438 };
3439
3440 void ext4_set_aops(struct inode *inode)
3441 {
3442         if (ext4_should_order_data(inode) &&
3443                 test_opt(inode->i_sb, DELALLOC))
3444                 inode->i_mapping->a_ops = &ext4_da_aops;
3445         else if (ext4_should_order_data(inode))
3446                 inode->i_mapping->a_ops = &ext4_ordered_aops;
3447         else if (ext4_should_writeback_data(inode) &&
3448                  test_opt(inode->i_sb, DELALLOC))
3449                 inode->i_mapping->a_ops = &ext4_da_aops;
3450         else if (ext4_should_writeback_data(inode))
3451                 inode->i_mapping->a_ops = &ext4_writeback_aops;
3452         else
3453                 inode->i_mapping->a_ops = &ext4_journalled_aops;
3454 }
3455
3456 /*
3457  * ext4_block_truncate_page() zeroes out a mapping from file offset `from'
3458  * up to the end of the block which corresponds to `from'.
3459  * This required during truncate. We need to physically zero the tail end
3460  * of that block so it doesn't yield old data if the file is later grown.
3461  */
3462 int ext4_block_truncate_page(handle_t *handle,
3463                 struct address_space *mapping, loff_t from)
3464 {
3465         ext4_fsblk_t index = from >> PAGE_CACHE_SHIFT;
3466         unsigned offset = from & (PAGE_CACHE_SIZE-1);
3467         unsigned blocksize, length, pos;
3468         ext4_lblk_t iblock;
3469         struct inode *inode = mapping->host;
3470         struct buffer_head *bh;
3471         struct page *page;
3472         int err = 0;
3473
3474         page = find_or_create_page(mapping, from >> PAGE_CACHE_SHIFT,
3475                                    mapping_gfp_mask(mapping) & ~__GFP_FS);
3476         if (!page)
3477                 return -EINVAL;
3478
3479         blocksize = inode->i_sb->s_blocksize;
3480         length = blocksize - (offset & (blocksize - 1));
3481         iblock = index << (PAGE_CACHE_SHIFT - inode->i_sb->s_blocksize_bits);
3482
3483         /*
3484          * For "nobh" option,  we can only work if we don't need to
3485          * read-in the page - otherwise we create buffers to do the IO.
3486          */
3487         if (!page_has_buffers(page) && test_opt(inode->i_sb, NOBH) &&
3488              ext4_should_writeback_data(inode) && PageUptodate(page)) {
3489                 zero_user(page, offset, length);
3490                 set_page_dirty(page);
3491                 goto unlock;
3492         }
3493
3494         if (!page_has_buffers(page))
3495                 create_empty_buffers(page, blocksize, 0);
3496
3497         /* Find the buffer that contains "offset" */
3498         bh = page_buffers(page);
3499         pos = blocksize;
3500         while (offset >= pos) {
3501                 bh = bh->b_this_page;
3502                 iblock++;
3503                 pos += blocksize;
3504         }
3505
3506         err = 0;
3507         if (buffer_freed(bh)) {
3508                 BUFFER_TRACE(bh, "freed: skip");
3509                 goto unlock;
3510         }
3511
3512         if (!buffer_mapped(bh)) {
3513                 BUFFER_TRACE(bh, "unmapped");
3514                 ext4_get_block(inode, iblock, bh, 0);
3515                 /* unmapped? It's a hole - nothing to do */
3516                 if (!buffer_mapped(bh)) {
3517                         BUFFER_TRACE(bh, "still unmapped");
3518                         goto unlock;
3519                 }
3520         }
3521
3522         /* Ok, it's mapped. Make sure it's up-to-date */
3523         if (PageUptodate(page))
3524                 set_buffer_uptodate(bh);
3525
3526         if (!buffer_uptodate(bh)) {
3527                 err = -EIO;
3528                 ll_rw_block(READ, 1, &bh);
3529                 wait_on_buffer(bh);
3530                 /* Uhhuh. Read error. Complain and punt. */
3531                 if (!buffer_uptodate(bh))
3532                         goto unlock;
3533         }
3534
3535         if (ext4_should_journal_data(inode)) {
3536                 BUFFER_TRACE(bh, "get write access");
3537                 err = ext4_journal_get_write_access(handle, bh);
3538                 if (err)
3539                         goto unlock;
3540         }
3541
3542         zero_user(page, offset, length);
3543
3544         BUFFER_TRACE(bh, "zeroed end of block");
3545
3546         err = 0;
3547         if (ext4_should_journal_data(inode)) {
3548                 err = ext4_handle_dirty_metadata(handle, inode, bh);
3549         } else {
3550                 if (ext4_should_order_data(inode))
3551                         err = ext4_jbd2_file_inode(handle, inode);
3552                 mark_buffer_dirty(bh);
3553         }
3554
3555 unlock:
3556         unlock_page(page);
3557         page_cache_release(page);
3558         return err;
3559 }
3560
3561 /*
3562  * Probably it should be a library function... search for first non-zero word
3563  * or memcmp with zero_page, whatever is better for particular architecture.
3564  * Linus?
3565  */
3566 static inline int all_zeroes(__le32 *p, __le32 *q)
3567 {
3568         while (p < q)
3569                 if (*p++)
3570                         return 0;
3571         return 1;
3572 }
3573
3574 /**
3575  *      ext4_find_shared - find the indirect blocks for partial truncation.
3576  *      @inode:   inode in question
3577  *      @depth:   depth of the affected branch
3578  *      @offsets: offsets of pointers in that branch (see ext4_block_to_path)
3579  *      @chain:   place to store the pointers to partial indirect blocks
3580  *      @top:     place to the (detached) top of branch
3581  *
3582  *      This is a helper function used by ext4_truncate().
3583  *
3584  *      When we do truncate() we may have to clean the ends of several
3585  *      indirect blocks but leave the blocks themselves alive. Block is
3586  *      partially truncated if some data below the new i_size is refered
3587  *      from it (and it is on the path to the first completely truncated
3588  *      data block, indeed).  We have to free the top of that path along
3589  *      with everything to the right of the path. Since no allocation
3590  *      past the truncation point is possible until ext4_truncate()
3591  *      finishes, we may safely do the latter, but top of branch may
3592  *      require special attention - pageout below the truncation point
3593  *      might try to populate it.
3594  *
3595  *      We atomically detach the top of branch from the tree, store the
3596  *      block number of its root in *@top, pointers to buffer_heads of
3597  *      partially truncated blocks - in @chain[].bh and pointers to
3598  *      their last elements that should not be removed - in
3599  *      @chain[].p. Return value is the pointer to last filled element
3600  *      of @chain.
3601  *
3602  *      The work left to caller to do the actual freeing of subtrees:
3603  *              a) free the subtree starting from *@top
3604  *              b) free the subtrees whose roots are stored in
3605  *                      (@chain[i].p+1 .. end of @chain[i].bh->b_data)
3606  *              c) free the subtrees growing from the inode past the @chain[0].
3607  *                      (no partially truncated stuff there).  */
3608
3609 static Indirect *ext4_find_shared(struct inode *inode, int depth,
3610                                   ext4_lblk_t offsets[4], Indirect chain[4],
3611                                   __le32 *top)
3612 {
3613         Indirect *partial, *p;
3614         int k, err;
3615
3616         *top = 0;
3617         /* Make k index the deepest non-null offest + 1 */
3618         for (k = depth; k > 1 && !offsets[k-1]; k--)
3619                 ;
3620         partial = ext4_get_branch(inode, k, offsets, chain, &err);
3621         /* Writer: pointers */
3622         if (!partial)
3623                 partial = chain + k-1;
3624         /*
3625          * If the branch acquired continuation since we've looked at it -
3626          * fine, it should all survive and (new) top doesn't belong to us.
3627          */
3628         if (!partial->key && *partial->p)
3629                 /* Writer: end */
3630                 goto no_top;
3631         for (p = partial; (p > chain) && all_zeroes((__le32 *) p->bh->b_data, p->p); p--)
3632                 ;
3633         /*
3634          * OK, we've found the last block that must survive. The rest of our
3635          * branch should be detached before unlocking. However, if that rest
3636          * of branch is all ours and does not grow immediately from the inode
3637          * it's easier to cheat and just decrement partial->p.
3638          */
3639         if (p == chain + k - 1 && p > chain) {
3640                 p->p--;
3641         } else {
3642                 *top = *p->p;
3643                 /* Nope, don't do this in ext4.  Must leave the tree intact */
3644 #if 0
3645                 *p->p = 0;
3646 #endif
3647         }
3648         /* Writer: end */
3649
3650         while (partial > p) {
3651                 brelse(partial->bh);
3652                 partial--;
3653         }
3654 no_top:
3655         return partial;
3656 }
3657
3658 /*
3659  * Zero a number of block pointers in either an inode or an indirect block.
3660  * If we restart the transaction we must again get write access to the
3661  * indirect block for further modification.
3662  *
3663  * We release `count' blocks on disk, but (last - first) may be greater
3664  * than `count' because there can be holes in there.
3665  */
3666 static void ext4_clear_blocks(handle_t *handle, struct inode *inode,
3667                               struct buffer_head *bh,
3668                               ext4_fsblk_t block_to_free,
3669                               unsigned long count, __le32 *first,
3670                               __le32 *last)
3671 {
3672         __le32 *p;
3673         if (try_to_extend_transaction(handle, inode)) {
3674                 if (bh) {
3675                         BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
3676                         ext4_handle_dirty_metadata(handle, inode, bh);
3677                 }
3678                 ext4_mark_inode_dirty(handle, inode);
3679                 ext4_truncate_restart_trans(handle, inode,
3680                                             blocks_for_truncate(inode));
3681                 if (bh) {
3682                         BUFFER_TRACE(bh, "retaking write access");
3683                         ext4_journal_get_write_access(handle, bh);
3684                 }
3685         }
3686
3687         /*
3688          * Any buffers which are on the journal will be in memory. We
3689          * find them on the hash table so jbd2_journal_revoke() will
3690          * run jbd2_journal_forget() on them.  We've already detached
3691          * each block from the file, so bforget() in
3692          * jbd2_journal_forget() should be safe.
3693          *
3694          * AKPM: turn on bforget in jbd2_journal_forget()!!!
3695          */
3696         for (p = first; p < last; p++) {
3697                 u32 nr = le32_to_cpu(*p);
3698                 if (nr) {
3699                         struct buffer_head *tbh;
3700
3701                         *p = 0;
3702                         tbh = sb_find_get_block(inode->i_sb, nr);
3703                         ext4_forget(handle, 0, inode, tbh, nr);
3704                 }
3705         }
3706
3707         ext4_free_blocks(handle, inode, block_to_free, count, 0);
3708 }
3709
3710 /**
3711  * ext4_free_data - free a list of data blocks
3712  * @handle:     handle for this transaction
3713  * @inode:      inode we are dealing with
3714  * @this_bh:    indirect buffer_head which contains *@first and *@last
3715  * @first:      array of block numbers
3716  * @last:       points immediately past the end of array
3717  *
3718  * We are freeing all blocks refered from that array (numbers are stored as
3719  * little-endian 32-bit) and updating @inode->i_blocks appropriately.
3720  *
3721  * We accumulate contiguous runs of blocks to free.  Conveniently, if these
3722  * blocks are contiguous then releasing them at one time will only affect one
3723  * or two bitmap blocks (+ group descriptor(s) and superblock) and we won't
3724  * actually use a lot of journal space.
3725  *
3726  * @this_bh will be %NULL if @first and @last point into the inode's direct
3727  * block pointers.
3728  */
3729 static void ext4_free_data(handle_t *handle, struct inode *inode,
3730                            struct buffer_head *this_bh,
3731                            __le32 *first, __le32 *last)
3732 {
3733         ext4_fsblk_t block_to_free = 0;    /* Starting block # of a run */
3734         unsigned long count = 0;            /* Number of blocks in the run */
3735         __le32 *block_to_free_p = NULL;     /* Pointer into inode/ind
3736                                                corresponding to
3737                                                block_to_free */
3738         ext4_fsblk_t nr;                    /* Current block # */
3739         __le32 *p;                          /* Pointer into inode/ind
3740                                                for current block */
3741         int err;
3742
3743         if (this_bh) {                          /* For indirect block */
3744                 BUFFER_TRACE(this_bh, "get_write_access");
3745                 err = ext4_journal_get_write_access(handle, this_bh);
3746                 /* Important: if we can't update the indirect pointers
3747                  * to the blocks, we can't free them. */
3748                 if (err)
3749                         return;
3750         }
3751
3752         for (p = first; p < last; p++) {
3753                 nr = le32_to_cpu(*p);
3754                 if (nr) {
3755                         /* accumulate blocks to free if they're contiguous */
3756                         if (count == 0) {
3757                                 block_to_free = nr;
3758                                 block_to_free_p = p;
3759                                 count = 1;
3760                         } else if (nr == block_to_free + count) {
3761                                 count++;
3762                         } else {
3763                                 ext4_clear_blocks(handle, inode, this_bh,
3764                                                   block_to_free,
3765                                                   count, block_to_free_p, p);
3766                                 block_to_free = nr;
3767                                 block_to_free_p = p;
3768                                 count = 1;
3769                         }
3770                 }
3771         }
3772
3773         if (count > 0)
3774                 ext4_clear_blocks(handle, inode, this_bh, block_to_free,
3775                                   count, block_to_free_p, p);
3776
3777         if (this_bh) {
3778                 BUFFER_TRACE(this_bh, "call ext4_handle_dirty_metadata");
3779
3780                 /*
3781                  * The buffer head should have an attached journal head at this
3782                  * point. However, if the data is corrupted and an indirect
3783                  * block pointed to itself, it would have been detached when
3784    &