]> nv-tegra.nvidia Code Review - linux-2.6.git/blob - fs/ext4/inode.c
ext4: Adjust ext4_da_writepages() to write out larger contiguous chunks
[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  * Return the number of dirty pages in the given inode starting at
1149  * page frame idx.
1150  */
1151 static pgoff_t ext4_num_dirty_pages(struct inode *inode, pgoff_t idx,
1152                                     unsigned int max_pages)
1153 {
1154         struct address_space *mapping = inode->i_mapping;
1155         pgoff_t index;
1156         struct pagevec pvec;
1157         pgoff_t num = 0;
1158         int i, nr_pages, done = 0;
1159
1160         if (max_pages == 0)
1161                 return 0;
1162         pagevec_init(&pvec, 0);
1163         while (!done) {
1164                 index = idx;
1165                 nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
1166                                               PAGECACHE_TAG_DIRTY,
1167                                               (pgoff_t)PAGEVEC_SIZE);
1168                 if (nr_pages == 0)
1169                         break;
1170                 for (i = 0; i < nr_pages; i++) {
1171                         struct page *page = pvec.pages[i];
1172                         struct buffer_head *bh, *head;
1173
1174                         lock_page(page);
1175                         if (unlikely(page->mapping != mapping) ||
1176                             !PageDirty(page) ||
1177                             PageWriteback(page) ||
1178                             page->index != idx) {
1179                                 done = 1;
1180                                 unlock_page(page);
1181                                 break;
1182                         }
1183                         head = page_buffers(page);
1184                         bh = head;
1185                         do {
1186                                 if (!buffer_delay(bh) &&
1187                                     !buffer_unwritten(bh)) {
1188                                         done = 1;
1189                                         break;
1190                                 }
1191                         } while ((bh = bh->b_this_page) != head);
1192                         unlock_page(page);
1193                         if (done)
1194                                 break;
1195                         idx++;
1196                         num++;
1197                         if (num >= max_pages)
1198                                 break;
1199                 }
1200                 pagevec_release(&pvec);
1201         }
1202         return num;
1203 }
1204
1205 /*
1206  * The ext4_get_blocks() function tries to look up the requested blocks,
1207  * and returns if the blocks are already mapped.
1208  *
1209  * Otherwise it takes the write lock of the i_data_sem and allocate blocks
1210  * and store the allocated blocks in the result buffer head and mark it
1211  * mapped.
1212  *
1213  * If file type is extents based, it will call ext4_ext_get_blocks(),
1214  * Otherwise, call with ext4_ind_get_blocks() to handle indirect mapping
1215  * based files
1216  *
1217  * On success, it returns the number of blocks being mapped or allocate.
1218  * if create==0 and the blocks are pre-allocated and uninitialized block,
1219  * the result buffer head is unmapped. If the create ==1, it will make sure
1220  * the buffer head is mapped.
1221  *
1222  * It returns 0 if plain look up failed (blocks have not been allocated), in
1223  * that casem, buffer head is unmapped
1224  *
1225  * It returns the error in case of allocation failure.
1226  */
1227 int ext4_get_blocks(handle_t *handle, struct inode *inode, sector_t block,
1228                     unsigned int max_blocks, struct buffer_head *bh,
1229                     int flags)
1230 {
1231         int retval;
1232
1233         clear_buffer_mapped(bh);
1234         clear_buffer_unwritten(bh);
1235
1236         /*
1237          * Try to see if we can get the block without requesting a new
1238          * file system block.
1239          */
1240         down_read((&EXT4_I(inode)->i_data_sem));
1241         if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) {
1242                 retval =  ext4_ext_get_blocks(handle, inode, block, max_blocks,
1243                                 bh, 0);
1244         } else {
1245                 retval = ext4_ind_get_blocks(handle, inode, block, max_blocks,
1246                                              bh, 0);
1247         }
1248         up_read((&EXT4_I(inode)->i_data_sem));
1249
1250         if (retval > 0 && buffer_mapped(bh)) {
1251                 int ret = check_block_validity(inode, "file system corruption",
1252                                                block, bh->b_blocknr, retval);
1253                 if (ret != 0)
1254                         return ret;
1255         }
1256
1257         /* If it is only a block(s) look up */
1258         if ((flags & EXT4_GET_BLOCKS_CREATE) == 0)
1259                 return retval;
1260
1261         /*
1262          * Returns if the blocks have already allocated
1263          *
1264          * Note that if blocks have been preallocated
1265          * ext4_ext_get_block() returns th create = 0
1266          * with buffer head unmapped.
1267          */
1268         if (retval > 0 && buffer_mapped(bh))
1269                 return retval;
1270
1271         /*
1272          * When we call get_blocks without the create flag, the
1273          * BH_Unwritten flag could have gotten set if the blocks
1274          * requested were part of a uninitialized extent.  We need to
1275          * clear this flag now that we are committed to convert all or
1276          * part of the uninitialized extent to be an initialized
1277          * extent.  This is because we need to avoid the combination
1278          * of BH_Unwritten and BH_Mapped flags being simultaneously
1279          * set on the buffer_head.
1280          */
1281         clear_buffer_unwritten(bh);
1282
1283         /*
1284          * New blocks allocate and/or writing to uninitialized extent
1285          * will possibly result in updating i_data, so we take
1286          * the write lock of i_data_sem, and call get_blocks()
1287          * with create == 1 flag.
1288          */
1289         down_write((&EXT4_I(inode)->i_data_sem));
1290
1291         /*
1292          * if the caller is from delayed allocation writeout path
1293          * we have already reserved fs blocks for allocation
1294          * let the underlying get_block() function know to
1295          * avoid double accounting
1296          */
1297         if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
1298                 EXT4_I(inode)->i_delalloc_reserved_flag = 1;
1299         /*
1300          * We need to check for EXT4 here because migrate
1301          * could have changed the inode type in between
1302          */
1303         if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) {
1304                 retval =  ext4_ext_get_blocks(handle, inode, block, max_blocks,
1305                                               bh, flags);
1306         } else {
1307                 retval = ext4_ind_get_blocks(handle, inode, block,
1308                                              max_blocks, bh, flags);
1309
1310                 if (retval > 0 && buffer_new(bh)) {
1311                         /*
1312                          * We allocated new blocks which will result in
1313                          * i_data's format changing.  Force the migrate
1314                          * to fail by clearing migrate flags
1315                          */
1316                         EXT4_I(inode)->i_state &= ~EXT4_STATE_EXT_MIGRATE;
1317                 }
1318         }
1319
1320         if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
1321                 EXT4_I(inode)->i_delalloc_reserved_flag = 0;
1322
1323         /*
1324          * Update reserved blocks/metadata blocks after successful
1325          * block allocation which had been deferred till now.
1326          */
1327         if ((retval > 0) && (flags & EXT4_GET_BLOCKS_UPDATE_RESERVE_SPACE))
1328                 ext4_da_update_reserve_space(inode, retval);
1329
1330         up_write((&EXT4_I(inode)->i_data_sem));
1331         if (retval > 0 && buffer_mapped(bh)) {
1332                 int ret = check_block_validity(inode, "file system "
1333                                                "corruption after allocation",
1334                                                block, bh->b_blocknr, retval);
1335                 if (ret != 0)
1336                         return ret;
1337         }
1338         return retval;
1339 }
1340
1341 /* Maximum number of blocks we map for direct IO at once. */
1342 #define DIO_MAX_BLOCKS 4096
1343
1344 int ext4_get_block(struct inode *inode, sector_t iblock,
1345                    struct buffer_head *bh_result, int create)
1346 {
1347         handle_t *handle = ext4_journal_current_handle();
1348         int ret = 0, started = 0;
1349         unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
1350         int dio_credits;
1351
1352         if (create && !handle) {
1353                 /* Direct IO write... */
1354                 if (max_blocks > DIO_MAX_BLOCKS)
1355                         max_blocks = DIO_MAX_BLOCKS;
1356                 dio_credits = ext4_chunk_trans_blocks(inode, max_blocks);
1357                 handle = ext4_journal_start(inode, dio_credits);
1358                 if (IS_ERR(handle)) {
1359                         ret = PTR_ERR(handle);
1360                         goto out;
1361                 }
1362                 started = 1;
1363         }
1364
1365         ret = ext4_get_blocks(handle, inode, iblock, max_blocks, bh_result,
1366                               create ? EXT4_GET_BLOCKS_CREATE : 0);
1367         if (ret > 0) {
1368                 bh_result->b_size = (ret << inode->i_blkbits);
1369                 ret = 0;
1370         }
1371         if (started)
1372                 ext4_journal_stop(handle);
1373 out:
1374         return ret;
1375 }
1376
1377 /*
1378  * `handle' can be NULL if create is zero
1379  */
1380 struct buffer_head *ext4_getblk(handle_t *handle, struct inode *inode,
1381                                 ext4_lblk_t block, int create, int *errp)
1382 {
1383         struct buffer_head dummy;
1384         int fatal = 0, err;
1385         int flags = 0;
1386
1387         J_ASSERT(handle != NULL || create == 0);
1388
1389         dummy.b_state = 0;
1390         dummy.b_blocknr = -1000;
1391         buffer_trace_init(&dummy.b_history);
1392         if (create)
1393                 flags |= EXT4_GET_BLOCKS_CREATE;
1394         err = ext4_get_blocks(handle, inode, block, 1, &dummy, flags);
1395         /*
1396          * ext4_get_blocks() returns number of blocks mapped. 0 in
1397          * case of a HOLE.
1398          */
1399         if (err > 0) {
1400                 if (err > 1)
1401                         WARN_ON(1);
1402                 err = 0;
1403         }
1404         *errp = err;
1405         if (!err && buffer_mapped(&dummy)) {
1406                 struct buffer_head *bh;
1407                 bh = sb_getblk(inode->i_sb, dummy.b_blocknr);
1408                 if (!bh) {
1409                         *errp = -EIO;
1410                         goto err;
1411                 }
1412                 if (buffer_new(&dummy)) {
1413                         J_ASSERT(create != 0);
1414                         J_ASSERT(handle != NULL);
1415
1416                         /*
1417                          * Now that we do not always journal data, we should
1418                          * keep in mind whether this should always journal the
1419                          * new buffer as metadata.  For now, regular file
1420                          * writes use ext4_get_block instead, so it's not a
1421                          * problem.
1422                          */
1423                         lock_buffer(bh);
1424                         BUFFER_TRACE(bh, "call get_create_access");
1425                         fatal = ext4_journal_get_create_access(handle, bh);
1426                         if (!fatal && !buffer_uptodate(bh)) {
1427                                 memset(bh->b_data, 0, inode->i_sb->s_blocksize);
1428                                 set_buffer_uptodate(bh);
1429                         }
1430                         unlock_buffer(bh);
1431                         BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
1432                         err = ext4_handle_dirty_metadata(handle, inode, bh);
1433                         if (!fatal)
1434                                 fatal = err;
1435                 } else {
1436                         BUFFER_TRACE(bh, "not a new buffer");
1437                 }
1438                 if (fatal) {
1439                         *errp = fatal;
1440                         brelse(bh);
1441                         bh = NULL;
1442                 }
1443                 return bh;
1444         }
1445 err:
1446         return NULL;
1447 }
1448
1449 struct buffer_head *ext4_bread(handle_t *handle, struct inode *inode,
1450                                ext4_lblk_t block, int create, int *err)
1451 {
1452         struct buffer_head *bh;
1453
1454         bh = ext4_getblk(handle, inode, block, create, err);
1455         if (!bh)
1456                 return bh;
1457         if (buffer_uptodate(bh))
1458                 return bh;
1459         ll_rw_block(READ_META, 1, &bh);
1460         wait_on_buffer(bh);
1461         if (buffer_uptodate(bh))
1462                 return bh;
1463         put_bh(bh);
1464         *err = -EIO;
1465         return NULL;
1466 }
1467
1468 static int walk_page_buffers(handle_t *handle,
1469                              struct buffer_head *head,
1470                              unsigned from,
1471                              unsigned to,
1472                              int *partial,
1473                              int (*fn)(handle_t *handle,
1474                                        struct buffer_head *bh))
1475 {
1476         struct buffer_head *bh;
1477         unsigned block_start, block_end;
1478         unsigned blocksize = head->b_size;
1479         int err, ret = 0;
1480         struct buffer_head *next;
1481
1482         for (bh = head, block_start = 0;
1483              ret == 0 && (bh != head || !block_start);
1484              block_start = block_end, bh = next) {
1485                 next = bh->b_this_page;
1486                 block_end = block_start + blocksize;
1487                 if (block_end <= from || block_start >= to) {
1488                         if (partial && !buffer_uptodate(bh))
1489                                 *partial = 1;
1490                         continue;
1491                 }
1492                 err = (*fn)(handle, bh);
1493                 if (!ret)
1494                         ret = err;
1495         }
1496         return ret;
1497 }
1498
1499 /*
1500  * To preserve ordering, it is essential that the hole instantiation and
1501  * the data write be encapsulated in a single transaction.  We cannot
1502  * close off a transaction and start a new one between the ext4_get_block()
1503  * and the commit_write().  So doing the jbd2_journal_start at the start of
1504  * prepare_write() is the right place.
1505  *
1506  * Also, this function can nest inside ext4_writepage() ->
1507  * block_write_full_page(). In that case, we *know* that ext4_writepage()
1508  * has generated enough buffer credits to do the whole page.  So we won't
1509  * block on the journal in that case, which is good, because the caller may
1510  * be PF_MEMALLOC.
1511  *
1512  * By accident, ext4 can be reentered when a transaction is open via
1513  * quota file writes.  If we were to commit the transaction while thus
1514  * reentered, there can be a deadlock - we would be holding a quota
1515  * lock, and the commit would never complete if another thread had a
1516  * transaction open and was blocking on the quota lock - a ranking
1517  * violation.
1518  *
1519  * So what we do is to rely on the fact that jbd2_journal_stop/journal_start
1520  * will _not_ run commit under these circumstances because handle->h_ref
1521  * is elevated.  We'll still have enough credits for the tiny quotafile
1522  * write.
1523  */
1524 static int do_journal_get_write_access(handle_t *handle,
1525                                        struct buffer_head *bh)
1526 {
1527         if (!buffer_mapped(bh) || buffer_freed(bh))
1528                 return 0;
1529         return ext4_journal_get_write_access(handle, bh);
1530 }
1531
1532 static int ext4_write_begin(struct file *file, struct address_space *mapping,
1533                             loff_t pos, unsigned len, unsigned flags,
1534                             struct page **pagep, void **fsdata)
1535 {
1536         struct inode *inode = mapping->host;
1537         int ret, needed_blocks;
1538         handle_t *handle;
1539         int retries = 0;
1540         struct page *page;
1541         pgoff_t index;
1542         unsigned from, to;
1543
1544         trace_ext4_write_begin(inode, pos, len, flags);
1545         /*
1546          * Reserve one block more for addition to orphan list in case
1547          * we allocate blocks but write fails for some reason
1548          */
1549         needed_blocks = ext4_writepage_trans_blocks(inode) + 1;
1550         index = pos >> PAGE_CACHE_SHIFT;
1551         from = pos & (PAGE_CACHE_SIZE - 1);
1552         to = from + len;
1553
1554 retry:
1555         handle = ext4_journal_start(inode, needed_blocks);
1556         if (IS_ERR(handle)) {
1557                 ret = PTR_ERR(handle);
1558                 goto out;
1559         }
1560
1561         /* We cannot recurse into the filesystem as the transaction is already
1562          * started */
1563         flags |= AOP_FLAG_NOFS;
1564
1565         page = grab_cache_page_write_begin(mapping, index, flags);
1566         if (!page) {
1567                 ext4_journal_stop(handle);
1568                 ret = -ENOMEM;
1569                 goto out;
1570         }
1571         *pagep = page;
1572
1573         ret = block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
1574                                 ext4_get_block);
1575
1576         if (!ret && ext4_should_journal_data(inode)) {
1577                 ret = walk_page_buffers(handle, page_buffers(page),
1578                                 from, to, NULL, do_journal_get_write_access);
1579         }
1580
1581         if (ret) {
1582                 unlock_page(page);
1583                 page_cache_release(page);
1584                 /*
1585                  * block_write_begin may have instantiated a few blocks
1586                  * outside i_size.  Trim these off again. Don't need
1587                  * i_size_read because we hold i_mutex.
1588                  *
1589                  * Add inode to orphan list in case we crash before
1590                  * truncate finishes
1591                  */
1592                 if (pos + len > inode->i_size && ext4_can_truncate(inode))
1593                         ext4_orphan_add(handle, inode);
1594
1595                 ext4_journal_stop(handle);
1596                 if (pos + len > inode->i_size) {
1597                         ext4_truncate(inode);
1598                         /*
1599                          * If truncate failed early the inode might
1600                          * still be on the orphan list; we need to
1601                          * make sure the inode is removed from the
1602                          * orphan list in that case.
1603                          */
1604                         if (inode->i_nlink)
1605                                 ext4_orphan_del(NULL, inode);
1606                 }
1607         }
1608
1609         if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
1610                 goto retry;
1611 out:
1612         return ret;
1613 }
1614
1615 /* For write_end() in data=journal mode */
1616 static int write_end_fn(handle_t *handle, struct buffer_head *bh)
1617 {
1618         if (!buffer_mapped(bh) || buffer_freed(bh))
1619                 return 0;
1620         set_buffer_uptodate(bh);
1621         return ext4_handle_dirty_metadata(handle, NULL, bh);
1622 }
1623
1624 static int ext4_generic_write_end(struct file *file,
1625                                   struct address_space *mapping,
1626                                   loff_t pos, unsigned len, unsigned copied,
1627                                   struct page *page, void *fsdata)
1628 {
1629         int i_size_changed = 0;
1630         struct inode *inode = mapping->host;
1631         handle_t *handle = ext4_journal_current_handle();
1632
1633         copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
1634
1635         /*
1636          * No need to use i_size_read() here, the i_size
1637          * cannot change under us because we hold i_mutex.
1638          *
1639          * But it's important to update i_size while still holding page lock:
1640          * page writeout could otherwise come in and zero beyond i_size.
1641          */
1642         if (pos + copied > inode->i_size) {
1643                 i_size_write(inode, pos + copied);
1644                 i_size_changed = 1;
1645         }
1646
1647         if (pos + copied >  EXT4_I(inode)->i_disksize) {
1648                 /* We need to mark inode dirty even if
1649                  * new_i_size is less that inode->i_size
1650                  * bu greater than i_disksize.(hint delalloc)
1651                  */
1652                 ext4_update_i_disksize(inode, (pos + copied));
1653                 i_size_changed = 1;
1654         }
1655         unlock_page(page);
1656         page_cache_release(page);
1657
1658         /*
1659          * Don't mark the inode dirty under page lock. First, it unnecessarily
1660          * makes the holding time of page lock longer. Second, it forces lock
1661          * ordering of page lock and transaction start for journaling
1662          * filesystems.
1663          */
1664         if (i_size_changed)
1665                 ext4_mark_inode_dirty(handle, inode);
1666
1667         return copied;
1668 }
1669
1670 /*
1671  * We need to pick up the new inode size which generic_commit_write gave us
1672  * `file' can be NULL - eg, when called from page_symlink().
1673  *
1674  * ext4 never places buffers on inode->i_mapping->private_list.  metadata
1675  * buffers are managed internally.
1676  */
1677 static int ext4_ordered_write_end(struct file *file,
1678                                   struct address_space *mapping,
1679                                   loff_t pos, unsigned len, unsigned copied,
1680                                   struct page *page, void *fsdata)
1681 {
1682         handle_t *handle = ext4_journal_current_handle();
1683         struct inode *inode = mapping->host;
1684         int ret = 0, ret2;
1685
1686         trace_ext4_ordered_write_end(inode, pos, len, copied);
1687         ret = ext4_jbd2_file_inode(handle, inode);
1688
1689         if (ret == 0) {
1690                 ret2 = ext4_generic_write_end(file, mapping, pos, len, copied,
1691                                                         page, fsdata);
1692                 copied = ret2;
1693                 if (pos + len > inode->i_size && ext4_can_truncate(inode))
1694                         /* if we have allocated more blocks and copied
1695                          * less. We will have blocks allocated outside
1696                          * inode->i_size. So truncate them
1697                          */
1698                         ext4_orphan_add(handle, inode);
1699                 if (ret2 < 0)
1700                         ret = ret2;
1701         }
1702         ret2 = ext4_journal_stop(handle);
1703         if (!ret)
1704                 ret = ret2;
1705
1706         if (pos + len > inode->i_size) {
1707                 ext4_truncate(inode);
1708                 /*
1709                  * If truncate failed early the inode might still be
1710                  * on the orphan list; we need to make sure the inode
1711                  * is removed from the orphan list in that case.
1712                  */
1713                 if (inode->i_nlink)
1714                         ext4_orphan_del(NULL, inode);
1715         }
1716
1717
1718         return ret ? ret : copied;
1719 }
1720
1721 static int ext4_writeback_write_end(struct file *file,
1722                                     struct address_space *mapping,
1723                                     loff_t pos, unsigned len, unsigned copied,
1724                                     struct page *page, void *fsdata)
1725 {
1726         handle_t *handle = ext4_journal_current_handle();
1727         struct inode *inode = mapping->host;
1728         int ret = 0, ret2;
1729
1730         trace_ext4_writeback_write_end(inode, pos, len, copied);
1731         ret2 = ext4_generic_write_end(file, mapping, pos, len, copied,
1732                                                         page, fsdata);
1733         copied = ret2;
1734         if (pos + len > inode->i_size && ext4_can_truncate(inode))
1735                 /* if we have allocated more blocks and copied
1736                  * less. We will have blocks allocated outside
1737                  * inode->i_size. So truncate them
1738                  */
1739                 ext4_orphan_add(handle, inode);
1740
1741         if (ret2 < 0)
1742                 ret = ret2;
1743
1744         ret2 = ext4_journal_stop(handle);
1745         if (!ret)
1746                 ret = ret2;
1747
1748         if (pos + len > inode->i_size) {
1749                 ext4_truncate(inode);
1750                 /*
1751                  * If truncate failed early the inode might still be
1752                  * on the orphan list; we need to make sure the inode
1753                  * is removed from the orphan list in that case.
1754                  */
1755                 if (inode->i_nlink)
1756                         ext4_orphan_del(NULL, inode);
1757         }
1758
1759         return ret ? ret : copied;
1760 }
1761
1762 static int ext4_journalled_write_end(struct file *file,
1763                                      struct address_space *mapping,
1764                                      loff_t pos, unsigned len, unsigned copied,
1765                                      struct page *page, void *fsdata)
1766 {
1767         handle_t *handle = ext4_journal_current_handle();
1768         struct inode *inode = mapping->host;
1769         int ret = 0, ret2;
1770         int partial = 0;
1771         unsigned from, to;
1772         loff_t new_i_size;
1773
1774         trace_ext4_journalled_write_end(inode, pos, len, copied);
1775         from = pos & (PAGE_CACHE_SIZE - 1);
1776         to = from + len;
1777
1778         if (copied < len) {
1779                 if (!PageUptodate(page))
1780                         copied = 0;
1781                 page_zero_new_buffers(page, from+copied, to);
1782         }
1783
1784         ret = walk_page_buffers(handle, page_buffers(page), from,
1785                                 to, &partial, write_end_fn);
1786         if (!partial)
1787                 SetPageUptodate(page);
1788         new_i_size = pos + copied;
1789         if (new_i_size > inode->i_size)
1790                 i_size_write(inode, pos+copied);
1791         EXT4_I(inode)->i_state |= EXT4_STATE_JDATA;
1792         if (new_i_size > EXT4_I(inode)->i_disksize) {
1793                 ext4_update_i_disksize(inode, new_i_size);
1794                 ret2 = ext4_mark_inode_dirty(handle, inode);
1795                 if (!ret)
1796                         ret = ret2;
1797         }
1798
1799         unlock_page(page);
1800         page_cache_release(page);
1801         if (pos + len > inode->i_size && ext4_can_truncate(inode))
1802                 /* if we have allocated more blocks and copied
1803                  * less. We will have blocks allocated outside
1804                  * inode->i_size. So truncate them
1805                  */
1806                 ext4_orphan_add(handle, inode);
1807
1808         ret2 = ext4_journal_stop(handle);
1809         if (!ret)
1810                 ret = ret2;
1811         if (pos + len > inode->i_size) {
1812                 ext4_truncate(inode);
1813                 /*
1814                  * If truncate failed early the inode might still be
1815                  * on the orphan list; we need to make sure the inode
1816                  * is removed from the orphan list in that case.
1817                  */
1818                 if (inode->i_nlink)
1819                         ext4_orphan_del(NULL, inode);
1820         }
1821
1822         return ret ? ret : copied;
1823 }
1824
1825 static int ext4_da_reserve_space(struct inode *inode, int nrblocks)
1826 {
1827         int retries = 0;
1828         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
1829         unsigned long md_needed, mdblocks, total = 0;
1830
1831         /*
1832          * recalculate the amount of metadata blocks to reserve
1833          * in order to allocate nrblocks
1834          * worse case is one extent per block
1835          */
1836 repeat:
1837         spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
1838         total = EXT4_I(inode)->i_reserved_data_blocks + nrblocks;
1839         mdblocks = ext4_calc_metadata_amount(inode, total);
1840         BUG_ON(mdblocks < EXT4_I(inode)->i_reserved_meta_blocks);
1841
1842         md_needed = mdblocks - EXT4_I(inode)->i_reserved_meta_blocks;
1843         total = md_needed + nrblocks;
1844
1845         /*
1846          * Make quota reservation here to prevent quota overflow
1847          * later. Real quota accounting is done at pages writeout
1848          * time.
1849          */
1850         if (vfs_dq_reserve_block(inode, total)) {
1851                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1852                 return -EDQUOT;
1853         }
1854
1855         if (ext4_claim_free_blocks(sbi, total)) {
1856                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1857                 if (ext4_should_retry_alloc(inode->i_sb, &retries)) {
1858                         yield();
1859                         goto repeat;
1860                 }
1861                 vfs_dq_release_reservation_block(inode, total);
1862                 return -ENOSPC;
1863         }
1864         EXT4_I(inode)->i_reserved_data_blocks += nrblocks;
1865         EXT4_I(inode)->i_reserved_meta_blocks = mdblocks;
1866
1867         spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1868         return 0;       /* success */
1869 }
1870
1871 static void ext4_da_release_space(struct inode *inode, int to_free)
1872 {
1873         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
1874         int total, mdb, mdb_free, release;
1875
1876         if (!to_free)
1877                 return;         /* Nothing to release, exit */
1878
1879         spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
1880
1881         if (!EXT4_I(inode)->i_reserved_data_blocks) {
1882                 /*
1883                  * if there is no reserved blocks, but we try to free some
1884                  * then the counter is messed up somewhere.
1885                  * but since this function is called from invalidate
1886                  * page, it's harmless to return without any action
1887                  */
1888                 printk(KERN_INFO "ext4 delalloc try to release %d reserved "
1889                             "blocks for inode %lu, but there is no reserved "
1890                             "data blocks\n", to_free, inode->i_ino);
1891                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1892                 return;
1893         }
1894
1895         /* recalculate the number of metablocks still need to be reserved */
1896         total = EXT4_I(inode)->i_reserved_data_blocks - to_free;
1897         mdb = ext4_calc_metadata_amount(inode, total);
1898
1899         /* figure out how many metablocks to release */
1900         BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
1901         mdb_free = EXT4_I(inode)->i_reserved_meta_blocks - mdb;
1902
1903         release = to_free + mdb_free;
1904
1905         /* update fs dirty blocks counter for truncate case */
1906         percpu_counter_sub(&sbi->s_dirtyblocks_counter, release);
1907
1908         /* update per-inode reservations */
1909         BUG_ON(to_free > EXT4_I(inode)->i_reserved_data_blocks);
1910         EXT4_I(inode)->i_reserved_data_blocks -= to_free;
1911
1912         BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
1913         EXT4_I(inode)->i_reserved_meta_blocks = mdb;
1914         spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1915
1916         vfs_dq_release_reservation_block(inode, release);
1917 }
1918
1919 static void ext4_da_page_release_reservation(struct page *page,
1920                                              unsigned long offset)
1921 {
1922         int to_release = 0;
1923         struct buffer_head *head, *bh;
1924         unsigned int curr_off = 0;
1925
1926         head = page_buffers(page);
1927         bh = head;
1928         do {
1929                 unsigned int next_off = curr_off + bh->b_size;
1930
1931                 if ((offset <= curr_off) && (buffer_delay(bh))) {
1932                         to_release++;
1933                         clear_buffer_delay(bh);
1934                 }
1935                 curr_off = next_off;
1936         } while ((bh = bh->b_this_page) != head);
1937         ext4_da_release_space(page->mapping->host, to_release);
1938 }
1939
1940 /*
1941  * Delayed allocation stuff
1942  */
1943
1944 /*
1945  * mpage_da_submit_io - walks through extent of pages and try to write
1946  * them with writepage() call back
1947  *
1948  * @mpd->inode: inode
1949  * @mpd->first_page: first page of the extent
1950  * @mpd->next_page: page after the last page of the extent
1951  *
1952  * By the time mpage_da_submit_io() is called we expect all blocks
1953  * to be allocated. this may be wrong if allocation failed.
1954  *
1955  * As pages are already locked by write_cache_pages(), we can't use it
1956  */
1957 static int mpage_da_submit_io(struct mpage_da_data *mpd)
1958 {
1959         long pages_skipped;
1960         struct pagevec pvec;
1961         unsigned long index, end;
1962         int ret = 0, err, nr_pages, i;
1963         struct inode *inode = mpd->inode;
1964         struct address_space *mapping = inode->i_mapping;
1965
1966         BUG_ON(mpd->next_page <= mpd->first_page);
1967         /*
1968          * We need to start from the first_page to the next_page - 1
1969          * to make sure we also write the mapped dirty buffer_heads.
1970          * If we look at mpd->b_blocknr we would only be looking
1971          * at the currently mapped buffer_heads.
1972          */
1973         index = mpd->first_page;
1974         end = mpd->next_page - 1;
1975
1976         pagevec_init(&pvec, 0);
1977         while (index <= end) {
1978                 nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
1979                 if (nr_pages == 0)
1980                         break;
1981                 for (i = 0; i < nr_pages; i++) {
1982                         struct page *page = pvec.pages[i];
1983
1984                         index = page->index;
1985                         if (index > end)
1986                                 break;
1987                         index++;
1988
1989                         BUG_ON(!PageLocked(page));
1990                         BUG_ON(PageWriteback(page));
1991
1992                         pages_skipped = mpd->wbc->pages_skipped;
1993                         err = mapping->a_ops->writepage(page, mpd->wbc);
1994                         if (!err && (pages_skipped == mpd->wbc->pages_skipped))
1995                                 /*
1996                                  * have successfully written the page
1997                                  * without skipping the same
1998                                  */
1999                                 mpd->pages_written++;
2000                         /*
2001                          * In error case, we have to continue because
2002                          * remaining pages are still locked
2003                          * XXX: unlock and re-dirty them?
2004                          */
2005                         if (ret == 0)
2006                                 ret = err;
2007                 }
2008                 pagevec_release(&pvec);
2009         }
2010         return ret;
2011 }
2012
2013 /*
2014  * mpage_put_bnr_to_bhs - walk blocks and assign them actual numbers
2015  *
2016  * @mpd->inode - inode to walk through
2017  * @exbh->b_blocknr - first block on a disk
2018  * @exbh->b_size - amount of space in bytes
2019  * @logical - first logical block to start assignment with
2020  *
2021  * the function goes through all passed space and put actual disk
2022  * block numbers into buffer heads, dropping BH_Delay and BH_Unwritten
2023  */
2024 static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd, sector_t logical,
2025                                  struct buffer_head *exbh)
2026 {
2027         struct inode *inode = mpd->inode;
2028         struct address_space *mapping = inode->i_mapping;
2029         int blocks = exbh->b_size >> inode->i_blkbits;
2030         sector_t pblock = exbh->b_blocknr, cur_logical;
2031         struct buffer_head *head, *bh;
2032         pgoff_t index, end;
2033         struct pagevec pvec;
2034         int nr_pages, i;
2035
2036         index = logical >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
2037         end = (logical + blocks - 1) >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
2038         cur_logical = index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2039
2040         pagevec_init(&pvec, 0);
2041
2042         while (index <= end) {
2043                 /* XXX: optimize tail */
2044                 nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
2045                 if (nr_pages == 0)
2046                         break;
2047                 for (i = 0; i < nr_pages; i++) {
2048                         struct page *page = pvec.pages[i];
2049
2050                         index = page->index;
2051                         if (index > end)
2052                                 break;
2053                         index++;
2054
2055                         BUG_ON(!PageLocked(page));
2056                         BUG_ON(PageWriteback(page));
2057                         BUG_ON(!page_has_buffers(page));
2058
2059                         bh = page_buffers(page);
2060                         head = bh;
2061
2062                         /* skip blocks out of the range */
2063                         do {
2064                                 if (cur_logical >= logical)
2065                                         break;
2066                                 cur_logical++;
2067                         } while ((bh = bh->b_this_page) != head);
2068
2069                         do {
2070                                 if (cur_logical >= logical + blocks)
2071                                         break;
2072
2073                                 if (buffer_delay(bh) ||
2074                                                 buffer_unwritten(bh)) {
2075
2076                                         BUG_ON(bh->b_bdev != inode->i_sb->s_bdev);
2077
2078                                         if (buffer_delay(bh)) {
2079                                                 clear_buffer_delay(bh);
2080                                                 bh->b_blocknr = pblock;
2081                                         } else {
2082                                                 /*
2083                                                  * unwritten already should have
2084                                                  * blocknr assigned. Verify that
2085                                                  */
2086                                                 clear_buffer_unwritten(bh);
2087                                                 BUG_ON(bh->b_blocknr != pblock);
2088                                         }
2089
2090                                 } else if (buffer_mapped(bh))
2091                                         BUG_ON(bh->b_blocknr != pblock);
2092
2093                                 cur_logical++;
2094                                 pblock++;
2095                         } while ((bh = bh->b_this_page) != head);
2096                 }
2097                 pagevec_release(&pvec);
2098         }
2099 }
2100
2101
2102 /*
2103  * __unmap_underlying_blocks - just a helper function to unmap
2104  * set of blocks described by @bh
2105  */
2106 static inline void __unmap_underlying_blocks(struct inode *inode,
2107                                              struct buffer_head *bh)
2108 {
2109         struct block_device *bdev = inode->i_sb->s_bdev;
2110         int blocks, i;
2111
2112         blocks = bh->b_size >> inode->i_blkbits;
2113         for (i = 0; i < blocks; i++)
2114                 unmap_underlying_metadata(bdev, bh->b_blocknr + i);
2115 }
2116
2117 static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd,
2118                                         sector_t logical, long blk_cnt)
2119 {
2120         int nr_pages, i;
2121         pgoff_t index, end;
2122         struct pagevec pvec;
2123         struct inode *inode = mpd->inode;
2124         struct address_space *mapping = inode->i_mapping;
2125
2126         index = logical >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
2127         end   = (logical + blk_cnt - 1) >>
2128                                 (PAGE_CACHE_SHIFT - inode->i_blkbits);
2129         while (index <= end) {
2130                 nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
2131                 if (nr_pages == 0)
2132                         break;
2133                 for (i = 0; i < nr_pages; i++) {
2134                         struct page *page = pvec.pages[i];
2135                         index = page->index;
2136                         if (index > end)
2137                                 break;
2138                         index++;
2139
2140                         BUG_ON(!PageLocked(page));
2141                         BUG_ON(PageWriteback(page));
2142                         block_invalidatepage(page, 0);
2143                         ClearPageUptodate(page);
2144                         unlock_page(page);
2145                 }
2146         }
2147         return;
2148 }
2149
2150 static void ext4_print_free_blocks(struct inode *inode)
2151 {
2152         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
2153         printk(KERN_CRIT "Total free blocks count %lld\n",
2154                ext4_count_free_blocks(inode->i_sb));
2155         printk(KERN_CRIT "Free/Dirty block details\n");
2156         printk(KERN_CRIT "free_blocks=%lld\n",
2157                (long long) percpu_counter_sum(&sbi->s_freeblocks_counter));
2158         printk(KERN_CRIT "dirty_blocks=%lld\n",
2159                (long long) percpu_counter_sum(&sbi->s_dirtyblocks_counter));
2160         printk(KERN_CRIT "Block reservation details\n");
2161         printk(KERN_CRIT "i_reserved_data_blocks=%u\n",
2162                EXT4_I(inode)->i_reserved_data_blocks);
2163         printk(KERN_CRIT "i_reserved_meta_blocks=%u\n",
2164                EXT4_I(inode)->i_reserved_meta_blocks);
2165         return;
2166 }
2167
2168 /*
2169  * mpage_da_map_blocks - go through given space
2170  *
2171  * @mpd - bh describing space
2172  *
2173  * The function skips space we know is already mapped to disk blocks.
2174  *
2175  */
2176 static int mpage_da_map_blocks(struct mpage_da_data *mpd)
2177 {
2178         int err, blks, get_blocks_flags;
2179         struct buffer_head new;
2180         sector_t next = mpd->b_blocknr;
2181         unsigned max_blocks = mpd->b_size >> mpd->inode->i_blkbits;
2182         loff_t disksize = EXT4_I(mpd->inode)->i_disksize;
2183         handle_t *handle = NULL;
2184
2185         /*
2186          * We consider only non-mapped and non-allocated blocks
2187          */
2188         if ((mpd->b_state  & (1 << BH_Mapped)) &&
2189                 !(mpd->b_state & (1 << BH_Delay)) &&
2190                 !(mpd->b_state & (1 << BH_Unwritten)))
2191                 return 0;
2192
2193         /*
2194          * If we didn't accumulate anything to write simply return
2195          */
2196         if (!mpd->b_size)
2197                 return 0;
2198
2199         handle = ext4_journal_current_handle();
2200         BUG_ON(!handle);
2201
2202         /*
2203          * Call ext4_get_blocks() to allocate any delayed allocation
2204          * blocks, or to convert an uninitialized extent to be
2205          * initialized (in the case where we have written into
2206          * one or more preallocated blocks).
2207          *
2208          * We pass in the magic EXT4_GET_BLOCKS_DELALLOC_RESERVE to
2209          * indicate that we are on the delayed allocation path.  This
2210          * affects functions in many different parts of the allocation
2211          * call path.  This flag exists primarily because we don't
2212          * want to change *many* call functions, so ext4_get_blocks()
2213          * will set the magic i_delalloc_reserved_flag once the
2214          * inode's allocation semaphore is taken.
2215          *
2216          * If the blocks in questions were delalloc blocks, set
2217          * EXT4_GET_BLOCKS_DELALLOC_RESERVE so the delalloc accounting
2218          * variables are updated after the blocks have been allocated.
2219          */
2220         new.b_state = 0;
2221         get_blocks_flags = (EXT4_GET_BLOCKS_CREATE |
2222                             EXT4_GET_BLOCKS_DELALLOC_RESERVE);
2223         if (mpd->b_state & (1 << BH_Delay))
2224                 get_blocks_flags |= EXT4_GET_BLOCKS_UPDATE_RESERVE_SPACE;
2225         blks = ext4_get_blocks(handle, mpd->inode, next, max_blocks,
2226                                &new, get_blocks_flags);
2227         if (blks < 0) {
2228                 err = blks;
2229                 /*
2230                  * If get block returns with error we simply
2231                  * return. Later writepage will redirty the page and
2232                  * writepages will find the dirty page again
2233                  */
2234                 if (err == -EAGAIN)
2235                         return 0;
2236
2237                 if (err == -ENOSPC &&
2238                     ext4_count_free_blocks(mpd->inode->i_sb)) {
2239                         mpd->retval = err;
2240                         return 0;
2241                 }
2242
2243                 /*
2244                  * get block failure will cause us to loop in
2245                  * writepages, because a_ops->writepage won't be able
2246                  * to make progress. The page will be redirtied by
2247                  * writepage and writepages will again try to write
2248                  * the same.
2249                  */
2250                 ext4_msg(mpd->inode->i_sb, KERN_CRIT,
2251                          "delayed block allocation failed for inode %lu at "
2252                          "logical offset %llu with max blocks %zd with "
2253                          "error %d\n", mpd->inode->i_ino,
2254                          (unsigned long long) next,
2255                          mpd->b_size >> mpd->inode->i_blkbits, err);
2256                 printk(KERN_CRIT "This should not happen!!  "
2257                        "Data will be lost\n");
2258                 if (err == -ENOSPC) {
2259                         ext4_print_free_blocks(mpd->inode);
2260                 }
2261                 /* invalidate all the pages */
2262                 ext4_da_block_invalidatepages(mpd, next,
2263                                 mpd->b_size >> mpd->inode->i_blkbits);
2264                 return err;
2265         }
2266         BUG_ON(blks == 0);
2267
2268         new.b_size = (blks << mpd->inode->i_blkbits);
2269
2270         if (buffer_new(&new))
2271                 __unmap_underlying_blocks(mpd->inode, &new);
2272
2273         /*
2274          * If blocks are delayed marked, we need to
2275          * put actual blocknr and drop delayed bit
2276          */
2277         if ((mpd->b_state & (1 << BH_Delay)) ||
2278             (mpd->b_state & (1 << BH_Unwritten)))
2279                 mpage_put_bnr_to_bhs(mpd, next, &new);
2280
2281         if (ext4_should_order_data(mpd->inode)) {
2282                 err = ext4_jbd2_file_inode(handle, mpd->inode);
2283                 if (err)
2284                         return err;
2285         }
2286
2287         /*
2288          * Update on-disk size along with block allocation.
2289          */
2290         disksize = ((loff_t) next + blks) << mpd->inode->i_blkbits;
2291         if (disksize > i_size_read(mpd->inode))
2292                 disksize = i_size_read(mpd->inode);
2293         if (disksize > EXT4_I(mpd->inode)->i_disksize) {
2294                 ext4_update_i_disksize(mpd->inode, disksize);
2295                 return ext4_mark_inode_dirty(handle, mpd->inode);
2296         }
2297
2298         return 0;
2299 }
2300
2301 #define BH_FLAGS ((1 << BH_Uptodate) | (1 << BH_Mapped) | \
2302                 (1 << BH_Delay) | (1 << BH_Unwritten))
2303
2304 /*
2305  * mpage_add_bh_to_extent - try to add one more block to extent of blocks
2306  *
2307  * @mpd->lbh - extent of blocks
2308  * @logical - logical number of the block in the file
2309  * @bh - bh of the block (used to access block's state)
2310  *
2311  * the function is used to collect contig. blocks in same state
2312  */
2313 static void mpage_add_bh_to_extent(struct mpage_da_data *mpd,
2314                                    sector_t logical, size_t b_size,
2315                                    unsigned long b_state)
2316 {
2317         sector_t next;
2318         int nrblocks = mpd->b_size >> mpd->inode->i_blkbits;
2319
2320         /* check if thereserved journal credits might overflow */
2321         if (!(EXT4_I(mpd->inode)->i_flags & EXT4_EXTENTS_FL)) {
2322                 if (nrblocks >= EXT4_MAX_TRANS_DATA) {
2323                         /*
2324                          * With non-extent format we are limited by the journal
2325                          * credit available.  Total credit needed to insert
2326                          * nrblocks contiguous blocks is dependent on the
2327                          * nrblocks.  So limit nrblocks.
2328                          */
2329                         goto flush_it;
2330                 } else if ((nrblocks + (b_size >> mpd->inode->i_blkbits)) >
2331                                 EXT4_MAX_TRANS_DATA) {
2332                         /*
2333                          * Adding the new buffer_head would make it cross the
2334                          * allowed limit for which we have journal credit
2335                          * reserved. So limit the new bh->b_size
2336                          */
2337                         b_size = (EXT4_MAX_TRANS_DATA - nrblocks) <<
2338                                                 mpd->inode->i_blkbits;
2339                         /* we will do mpage_da_submit_io in the next loop */
2340                 }
2341         }
2342         /*
2343          * First block in the extent
2344          */
2345         if (mpd->b_size == 0) {
2346                 mpd->b_blocknr = logical;
2347                 mpd->b_size = b_size;
2348                 mpd->b_state = b_state & BH_FLAGS;
2349                 return;
2350         }
2351
2352         next = mpd->b_blocknr + nrblocks;
2353         /*
2354          * Can we merge the block to our big extent?
2355          */
2356         if (logical == next && (b_state & BH_FLAGS) == mpd->b_state) {
2357                 mpd->b_size += b_size;
2358                 return;
2359         }
2360
2361 flush_it:
2362         /*
2363          * We couldn't merge the block to our extent, so we
2364          * need to flush current  extent and start new one
2365          */
2366         if (mpage_da_map_blocks(mpd) == 0)
2367                 mpage_da_submit_io(mpd);
2368         mpd->io_done = 1;
2369         return;
2370 }
2371
2372 static int ext4_bh_delay_or_unwritten(handle_t *handle, struct buffer_head *bh)
2373 {
2374         return (buffer_delay(bh) || buffer_unwritten(bh)) && buffer_dirty(bh);
2375 }
2376
2377 /*
2378  * __mpage_da_writepage - finds extent of pages and blocks
2379  *
2380  * @page: page to consider
2381  * @wbc: not used, we just follow rules
2382  * @data: context
2383  *
2384  * The function finds extents of pages and scan them for all blocks.
2385  */
2386 static int __mpage_da_writepage(struct page *page,
2387                                 struct writeback_control *wbc, void *data)
2388 {
2389         struct mpage_da_data *mpd = data;
2390         struct inode *inode = mpd->inode;
2391         struct buffer_head *bh, *head;
2392         sector_t logical;
2393
2394         if (mpd->io_done) {
2395                 /*
2396                  * Rest of the page in the page_vec
2397                  * redirty then and skip then. We will
2398                  * try to write them again after
2399                  * starting a new transaction
2400                  */
2401                 redirty_page_for_writepage(wbc, page);
2402                 unlock_page(page);
2403                 return MPAGE_DA_EXTENT_TAIL;
2404         }
2405         /*
2406          * Can we merge this page to current extent?
2407          */
2408         if (mpd->next_page != page->index) {
2409                 /*
2410                  * Nope, we can't. So, we map non-allocated blocks
2411                  * and start IO on them using writepage()
2412                  */
2413                 if (mpd->next_page != mpd->first_page) {
2414                         if (mpage_da_map_blocks(mpd) == 0)
2415                                 mpage_da_submit_io(mpd);
2416                         /*
2417                          * skip rest of the page in the page_vec
2418                          */
2419                         mpd->io_done = 1;
2420                         redirty_page_for_writepage(wbc, page);
2421                         unlock_page(page);
2422                         return MPAGE_DA_EXTENT_TAIL;
2423                 }
2424
2425                 /*
2426                  * Start next extent of pages ...
2427                  */
2428                 mpd->first_page = page->index;
2429
2430                 /*
2431                  * ... and blocks
2432                  */
2433                 mpd->b_size = 0;
2434                 mpd->b_state = 0;
2435                 mpd->b_blocknr = 0;
2436         }
2437
2438         mpd->next_page = page->index + 1;
2439         logical = (sector_t) page->index <<
2440                   (PAGE_CACHE_SHIFT - inode->i_blkbits);
2441
2442         if (!page_has_buffers(page)) {
2443                 mpage_add_bh_to_extent(mpd, logical, PAGE_CACHE_SIZE,
2444                                        (1 << BH_Dirty) | (1 << BH_Uptodate));
2445                 if (mpd->io_done)
2446                         return MPAGE_DA_EXTENT_TAIL;
2447         } else {
2448                 /*
2449                  * Page with regular buffer heads, just add all dirty ones
2450                  */
2451                 head = page_buffers(page);
2452                 bh = head;
2453                 do {
2454                         BUG_ON(buffer_locked(bh));
2455                         /*
2456                          * We need to try to allocate
2457                          * unmapped blocks in the same page.
2458                          * Otherwise we won't make progress
2459                          * with the page in ext4_writepage
2460                          */
2461                         if (ext4_bh_delay_or_unwritten(NULL, bh)) {
2462                                 mpage_add_bh_to_extent(mpd, logical,
2463                                                        bh->b_size,
2464                                                        bh->b_state);
2465                                 if (mpd->io_done)
2466                                         return MPAGE_DA_EXTENT_TAIL;
2467                         } else if (buffer_dirty(bh) && (buffer_mapped(bh))) {
2468                                 /*
2469                                  * mapped dirty buffer. We need to update
2470                                  * the b_state because we look at
2471                                  * b_state in mpage_da_map_blocks. We don't
2472                                  * update b_size because if we find an
2473                                  * unmapped buffer_head later we need to
2474                                  * use the b_state flag of that buffer_head.
2475                                  */
2476                                 if (mpd->b_size == 0)
2477                                         mpd->b_state = bh->b_state & BH_FLAGS;
2478                         }
2479                         logical++;
2480                 } while ((bh = bh->b_this_page) != head);
2481         }
2482
2483         return 0;
2484 }
2485
2486 /*
2487  * This is a special get_blocks_t callback which is used by
2488  * ext4_da_write_begin().  It will either return mapped block or
2489  * reserve space for a single block.
2490  *
2491  * For delayed buffer_head we have BH_Mapped, BH_New, BH_Delay set.
2492  * We also have b_blocknr = -1 and b_bdev initialized properly
2493  *
2494  * For unwritten buffer_head we have BH_Mapped, BH_New, BH_Unwritten set.
2495  * We also have b_blocknr = physicalblock mapping unwritten extent and b_bdev
2496  * initialized properly.
2497  */
2498 static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
2499                                   struct buffer_head *bh_result, int create)
2500 {
2501         int ret = 0;
2502         sector_t invalid_block = ~((sector_t) 0xffff);
2503
2504         if (invalid_block < ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es))
2505                 invalid_block = ~0;
2506
2507         BUG_ON(create == 0);
2508         BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
2509
2510         /*
2511          * first, we need to know whether the block is allocated already
2512          * preallocated blocks are unmapped but should treated
2513          * the same as allocated blocks.
2514          */
2515         ret = ext4_get_blocks(NULL, inode, iblock, 1,  bh_result, 0);
2516         if ((ret == 0) && !buffer_delay(bh_result)) {
2517                 /* the block isn't (pre)allocated yet, let's reserve space */
2518                 /*
2519                  * XXX: __block_prepare_write() unmaps passed block,
2520                  * is it OK?
2521                  */
2522                 ret = ext4_da_reserve_space(inode, 1);
2523                 if (ret)
2524                         /* not enough space to reserve */
2525                         return ret;
2526
2527                 map_bh(bh_result, inode->i_sb, invalid_block);
2528                 set_buffer_new(bh_result);
2529                 set_buffer_delay(bh_result);
2530         } else if (ret > 0) {
2531                 bh_result->b_size = (ret << inode->i_blkbits);
2532                 if (buffer_unwritten(bh_result)) {
2533                         /* A delayed write to unwritten bh should
2534                          * be marked new and mapped.  Mapped ensures
2535                          * that we don't do get_block multiple times
2536                          * when we write to the same offset and new
2537                          * ensures that we do proper zero out for
2538                          * partial write.
2539                          */
2540                         set_buffer_new(bh_result);
2541                         set_buffer_mapped(bh_result);
2542                 }
2543                 ret = 0;
2544         }
2545
2546         return ret;
2547 }
2548
2549 /*
2550  * This function is used as a standard get_block_t calback function
2551  * when there is no desire to allocate any blocks.  It is used as a
2552  * callback function for block_prepare_write(), nobh_writepage(), and
2553  * block_write_full_page().  These functions should only try to map a
2554  * single block at a time.
2555  *
2556  * Since this function doesn't do block allocations even if the caller
2557  * requests it by passing in create=1, it is critically important that
2558  * any caller checks to make sure that any buffer heads are returned
2559  * by this function are either all already mapped or marked for
2560  * delayed allocation before calling nobh_writepage() or
2561  * block_write_full_page().  Otherwise, b_blocknr could be left
2562  * unitialized, and the page write functions will be taken by
2563  * surprise.
2564  */
2565 static int noalloc_get_block_write(struct inode *inode, sector_t iblock,
2566                                    struct buffer_head *bh_result, int create)
2567 {
2568         int ret = 0;
2569         unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
2570
2571         BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
2572
2573         /*
2574          * we don't want to do block allocation in writepage
2575          * so call get_block_wrap with create = 0
2576          */
2577         ret = ext4_get_blocks(NULL, inode, iblock, max_blocks, bh_result, 0);
2578         if (ret > 0) {
2579                 bh_result->b_size = (ret << inode->i_blkbits);
2580                 ret = 0;
2581         }
2582         return ret;
2583 }
2584
2585 static int bget_one(handle_t *handle, struct buffer_head *bh)
2586 {
2587         get_bh(bh);
2588         return 0;
2589 }
2590
2591 static int bput_one(handle_t *handle, struct buffer_head *bh)
2592 {
2593         put_bh(bh);
2594         return 0;
2595 }
2596
2597 static int __ext4_journalled_writepage(struct page *page,
2598                                        struct writeback_control *wbc,
2599                                        unsigned int len)
2600 {
2601         struct address_space *mapping = page->mapping;
2602         struct inode *inode = mapping->host;
2603         struct buffer_head *page_bufs;
2604         handle_t *handle = NULL;
2605         int ret = 0;
2606         int err;
2607
2608         page_bufs = page_buffers(page);
2609         BUG_ON(!page_bufs);
2610         walk_page_buffers(handle, page_bufs, 0, len, NULL, bget_one);
2611         /* As soon as we unlock the page, it can go away, but we have
2612          * references to buffers so we are safe */
2613         unlock_page(page);
2614
2615         handle = ext4_journal_start(inode, ext4_writepage_trans_blocks(inode));
2616         if (IS_ERR(handle)) {
2617                 ret = PTR_ERR(handle);
2618                 goto out;
2619         }
2620
2621         ret = walk_page_buffers(handle, page_bufs, 0, len, NULL,
2622                                 do_journal_get_write_access);
2623
2624         err = walk_page_buffers(handle, page_bufs, 0, len, NULL,
2625                                 write_end_fn);
2626         if (ret == 0)
2627                 ret = err;
2628         err = ext4_journal_stop(handle);
2629         if (!ret)
2630                 ret = err;
2631
2632         walk_page_buffers(handle, page_bufs, 0, len, NULL, bput_one);
2633         EXT4_I(inode)->i_state |= EXT4_STATE_JDATA;
2634 out:
2635         return ret;
2636 }
2637
2638 /*
2639  * Note that we don't need to start a transaction unless we're journaling data
2640  * because we should have holes filled from ext4_page_mkwrite(). We even don't
2641  * need to file the inode to the transaction's list in ordered mode because if
2642  * we are writing back data added by write(), the inode is already there and if
2643  * we are writing back data modified via mmap(), noone guarantees in which
2644  * transaction the data will hit the disk. In case we are journaling data, we
2645  * cannot start transaction directly because transaction start ranks above page
2646  * lock so we have to do some magic.
2647  *
2648  * This function can get called via...
2649  *   - ext4_da_writepages after taking page lock (have journal handle)
2650  *   - journal_submit_inode_data_buffers (no journal handle)
2651  *   - shrink_page_list via pdflush (no journal handle)
2652  *   - grab_page_cache when doing write_begin (have journal handle)
2653  *
2654  * We don't do any block allocation in this function. If we have page with
2655  * multiple blocks we need to write those buffer_heads that are mapped. This
2656  * is important for mmaped based write. So if we do with blocksize 1K
2657  * truncate(f, 1024);
2658  * a = mmap(f, 0, 4096);
2659  * a[0] = 'a';
2660  * truncate(f, 4096);
2661  * we have in the page first buffer_head mapped via page_mkwrite call back
2662  * but other bufer_heads would be unmapped but dirty(dirty done via the
2663  * do_wp_page). So writepage should write the first block. If we modify
2664  * the mmap area beyond 1024 we will again get a page_fault and the
2665  * page_mkwrite callback will do the block allocation and mark the
2666  * buffer_heads mapped.
2667  *
2668  * We redirty the page if we have any buffer_heads that is either delay or
2669  * unwritten in the page.
2670  *
2671  * We can get recursively called as show below.
2672  *
2673  *      ext4_writepage() -> kmalloc() -> __alloc_pages() -> page_launder() ->
2674  *              ext4_writepage()
2675  *
2676  * But since we don't do any block allocation we should not deadlock.
2677  * Page also have the dirty flag cleared so we don't get recurive page_lock.
2678  */
2679 static int ext4_writepage(struct page *page,
2680                           struct writeback_control *wbc)
2681 {
2682         int ret = 0;
2683         loff_t size;
2684         unsigned int len;
2685         struct buffer_head *page_bufs;
2686         struct inode *inode = page->mapping->host;
2687
2688         trace_ext4_writepage(inode, page);
2689         size = i_size_read(inode);
2690         if (page->index == size >> PAGE_CACHE_SHIFT)
2691                 len = size & ~PAGE_CACHE_MASK;
2692         else
2693                 len = PAGE_CACHE_SIZE;
2694
2695         if (page_has_buffers(page)) {
2696                 page_bufs = page_buffers(page);
2697                 if (walk_page_buffers(NULL, page_bufs, 0, len, NULL,
2698                                         ext4_bh_delay_or_unwritten)) {
2699                         /*
2700                          * We don't want to do  block allocation
2701                          * So redirty the page and return
2702                          * We may reach here when we do a journal commit
2703                          * via journal_submit_inode_data_buffers.
2704                          * If we don't have mapping block we just ignore
2705                          * them. We can also reach here via shrink_page_list
2706                          */
2707                         redirty_page_for_writepage(wbc, page);
2708                         unlock_page(page);
2709                         return 0;
2710                 }
2711         } else {
2712                 /*
2713                  * The test for page_has_buffers() is subtle:
2714                  * We know the page is dirty but it lost buffers. That means
2715                  * that at some moment in time after write_begin()/write_end()
2716                  * has been called all buffers have been clean and thus they
2717                  * must have been written at least once. So they are all
2718                  * mapped and we can happily proceed with mapping them
2719                  * and writing the page.
2720                  *
2721                  * Try to initialize the buffer_heads and check whether
2722                  * all are mapped and non delay. We don't want to
2723                  * do block allocation here.
2724                  */
2725                 ret = block_prepare_write(page, 0, len,
2726                                           noalloc_get_block_write);
2727                 if (!ret) {
2728                         page_bufs = page_buffers(page);
2729                         /* check whether all are mapped and non delay */
2730                         if (walk_page_buffers(NULL, page_bufs, 0, len, NULL,
2731                                                 ext4_bh_delay_or_unwritten)) {
2732                                 redirty_page_for_writepage(wbc, page);
2733                                 unlock_page(page);
2734                                 return 0;
2735                         }
2736                 } else {
2737                         /*
2738                          * We can't do block allocation here
2739                          * so just redity the page and unlock
2740                          * and return
2741                          */
2742                         redirty_page_for_writepage(wbc, page);
2743                         unlock_page(page);
2744                         return 0;
2745                 }
2746                 /* now mark the buffer_heads as dirty and uptodate */
2747                 block_commit_write(page, 0, len);
2748         }
2749
2750         if (PageChecked(page) && ext4_should_journal_data(inode)) {
2751                 /*
2752                  * It's mmapped pagecache.  Add buffers and journal it.  There
2753                  * doesn't seem much point in redirtying the page here.
2754                  */
2755                 ClearPageChecked(page);
2756                 return __ext4_journalled_writepage(page, wbc, len);
2757         }
2758
2759         if (test_opt(inode->i_sb, NOBH) && ext4_should_writeback_data(inode))
2760                 ret = nobh_writepage(page, noalloc_get_block_write, wbc);
2761         else
2762                 ret = block_write_full_page(page, noalloc_get_block_write,
2763                                             wbc);
2764
2765         return ret;
2766 }
2767
2768 /*
2769  * This is called via ext4_da_writepages() to
2770  * calulate the total number of credits to reserve to fit
2771  * a single extent allocation into a single transaction,
2772  * ext4_da_writpeages() will loop calling this before
2773  * the block allocation.
2774  */
2775
2776 static int ext4_da_writepages_trans_blocks(struct inode *inode)
2777 {
2778         int max_blocks = EXT4_I(inode)->i_reserved_data_blocks;
2779
2780         /*
2781          * With non-extent format the journal credit needed to
2782          * insert nrblocks contiguous block is dependent on
2783          * number of contiguous block. So we will limit
2784          * number of contiguous block to a sane value
2785          */
2786         if (!(inode->i_flags & EXT4_EXTENTS_FL) &&
2787             (max_blocks > EXT4_MAX_TRANS_DATA))
2788                 max_blocks = EXT4_MAX_TRANS_DATA;
2789
2790         return ext4_chunk_trans_blocks(inode, max_blocks);
2791 }
2792
2793 static int ext4_da_writepages(struct address_space *mapping,
2794                               struct writeback_control *wbc)
2795 {
2796         pgoff_t index;
2797         int range_whole = 0;
2798         handle_t *handle = NULL;
2799         struct mpage_da_data mpd;
2800         struct inode *inode = mapping->host;
2801         int no_nrwrite_index_update;
2802         int pages_written = 0;
2803         long pages_skipped;
2804         unsigned int max_pages;
2805         int range_cyclic, cycled = 1, io_done = 0;
2806         int needed_blocks, ret = 0;
2807         long desired_nr_to_write, nr_to_writebump = 0;
2808         loff_t range_start = wbc->range_start;
2809         struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);
2810
2811         trace_ext4_da_writepages(inode, wbc);
2812
2813         /*
2814          * No pages to write? This is mainly a kludge to avoid starting
2815          * a transaction for special inodes like journal inode on last iput()
2816          * because that could violate lock ordering on umount
2817          */
2818         if (!mapping->nrpages || !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
2819                 return 0;
2820
2821         /*
2822          * If the filesystem has aborted, it is read-only, so return
2823          * right away instead of dumping stack traces later on that
2824          * will obscure the real source of the problem.  We test
2825          * EXT4_MF_FS_ABORTED instead of sb->s_flag's MS_RDONLY because
2826          * the latter could be true if the filesystem is mounted
2827          * read-only, and in that case, ext4_da_writepages should
2828          * *never* be called, so if that ever happens, we would want
2829          * the stack trace.
2830          */
2831         if (unlikely(sbi->s_mount_flags & EXT4_MF_FS_ABORTED))
2832                 return -EROFS;
2833
2834         if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
2835                 range_whole = 1;
2836
2837         range_cyclic = wbc->range_cyclic;
2838         if (wbc->range_cyclic) {
2839                 index = mapping->writeback_index;
2840                 if (index)
2841                         cycled = 0;
2842                 wbc->range_start = index << PAGE_CACHE_SHIFT;
2843                 wbc->range_end  = LLONG_MAX;
2844                 wbc->range_cyclic = 0;
2845         } else
2846                 index = wbc->range_start >> PAGE_CACHE_SHIFT;
2847
2848         /*
2849          * This works around two forms of stupidity.  The first is in
2850          * the writeback code, which caps the maximum number of pages
2851          * written to be 1024 pages.  This is wrong on multiple
2852          * levels; different architectues have a different page size,
2853          * which changes the maximum amount of data which gets
2854          * written.  Secondly, 4 megabytes is way too small.  XFS
2855          * forces this value to be 16 megabytes by multiplying
2856          * nr_to_write parameter by four, and then relies on its
2857          * allocator to allocate larger extents to make them
2858          * contiguous.  Unfortunately this brings us to the second
2859          * stupidity, which is that ext4's mballoc code only allocates
2860          * at most 2048 blocks.  So we force contiguous writes up to
2861          * the number of dirty blocks in the inode, or
2862          * sbi->max_writeback_mb_bump whichever is smaller.
2863          */
2864         max_pages = sbi->s_max_writeback_mb_bump << (20 - PAGE_CACHE_SHIFT);
2865         if (!range_cyclic && range_whole)
2866                 desired_nr_to_write = wbc->nr_to_write * 8;
2867         else
2868                 desired_nr_to_write = ext4_num_dirty_pages(inode, index,
2869                                                            max_pages);
2870         if (desired_nr_to_write > max_pages)
2871                 desired_nr_to_write = max_pages;
2872
2873         if (wbc->nr_to_write < desired_nr_to_write) {
2874                 nr_to_writebump = desired_nr_to_write - wbc->nr_to_write;
2875                 wbc->nr_to_write = desired_nr_to_write;
2876         }
2877
2878         mpd.wbc = wbc;
2879         mpd.inode = mapping->host;
2880
2881         /*
2882          * we don't want write_cache_pages to update
2883          * nr_to_write and writeback_index
2884          */
2885         no_nrwrite_index_update = wbc->no_nrwrite_index_update;
2886         wbc->no_nrwrite_index_update = 1;
2887         pages_skipped = wbc->pages_skipped;
2888
2889 retry:
2890         while (!ret && wbc->nr_to_write > 0) {
2891
2892                 /*
2893                  * we  insert one extent at a time. So we need
2894                  * credit needed for single extent allocation.
2895                  * journalled mode is currently not supported
2896                  * by delalloc
2897                  */
2898                 BUG_ON(ext4_should_journal_data(inode));
2899                 needed_blocks = ext4_da_writepages_trans_blocks(inode);
2900
2901                 /* start a new transaction*/
2902                 handle = ext4_journal_start(inode, needed_blocks);
2903                 if (IS_ERR(handle)) {
2904                         ret = PTR_ERR(handle);
2905                         ext4_msg(inode->i_sb, KERN_CRIT, "%s: jbd2_start: "
2906                                "%ld pages, ino %lu; err %d\n", __func__,
2907                                 wbc->nr_to_write, inode->i_ino, ret);
2908                         goto out_writepages;
2909                 }
2910
2911                 /*
2912                  * Now call __mpage_da_writepage to find the next
2913                  * contiguous region of logical blocks that need
2914                  * blocks to be allocated by ext4.  We don't actually
2915                  * submit the blocks for I/O here, even though
2916                  * write_cache_pages thinks it will, and will set the
2917                  * pages as clean for write before calling
2918                  * __mpage_da_writepage().
2919                  */
2920                 mpd.b_size = 0;
2921                 mpd.b_state = 0;
2922                 mpd.b_blocknr = 0;
2923                 mpd.first_page = 0;
2924                 mpd.next_page = 0;
2925                 mpd.io_done = 0;
2926                 mpd.pages_written = 0;
2927                 mpd.retval = 0;
2928                 ret = write_cache_pages(mapping, wbc, __mpage_da_writepage,
2929                                         &mpd);
2930                 /*
2931                  * If we have a contigous extent of pages and we
2932                  * haven't done the I/O yet, map the blocks and submit
2933                  * them for I/O.
2934                  */
2935                 if (!mpd.io_done && mpd.next_page != mpd.first_page) {
2936                         if (mpage_da_map_blocks(&mpd) == 0)
2937                                 mpage_da_submit_io(&mpd);
2938                         mpd.io_done = 1;
2939                         ret = MPAGE_DA_EXTENT_TAIL;
2940                 }
2941                 trace_ext4_da_write_pages(inode, &mpd);
2942                 wbc->nr_to_write -= mpd.pages_written;
2943
2944                 ext4_journal_stop(handle);
2945
2946                 if ((mpd.retval == -ENOSPC) && sbi->s_journal) {
2947                         /* commit the transaction which would
2948                          * free blocks released in the transaction
2949                          * and try again
2950                          */
2951                         jbd2_journal_force_commit_nested(sbi->s_journal);
2952                         wbc->pages_skipped = pages_skipped;
2953                         ret = 0;
2954                 } else if (ret == MPAGE_DA_EXTENT_TAIL) {
2955                         /*
2956                          * got one extent now try with
2957                          * rest of the pages
2958                          */
2959                         pages_written += mpd.pages_written;
2960                         wbc->pages_skipped = pages_skipped;
2961                         ret = 0;
2962                         io_done = 1;
2963                 } else if (wbc->nr_to_write)
2964                         /*
2965                          * There is no more writeout needed
2966                          * or we requested for a noblocking writeout
2967                          * and we found the device congested
2968                          */
2969                         break;
2970         }
2971         if (!io_done && !cycled) {
2972                 cycled = 1;
2973                 index = 0;
2974                 wbc->range_start = index << PAGE_CACHE_SHIFT;
2975                 wbc->range_end  = mapping->writeback_index - 1;
2976                 goto retry;
2977         }
2978         if (pages_skipped != wbc->pages_skipped)
2979                 ext4_msg(inode->i_sb, KERN_CRIT,
2980                          "This should not happen leaving %s "
2981                          "with nr_to_write = %ld ret = %d\n",
2982                          __func__, wbc->nr_to_write, ret);
2983
2984         /* Update index */
2985         index += pages_written;
2986         wbc->range_cyclic = range_cyclic;
2987         if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
2988                 /*
2989                  * set the writeback_index so that range_cyclic
2990                  * mode will write it back later
2991                  */
2992                 mapping->writeback_index = index;
2993
2994 out_writepages:
2995         if (!no_nrwrite_index_update)
2996                 wbc->no_nrwrite_index_update = 0;
2997         if (wbc->nr_to_write > nr_to_writebump)
2998                 wbc->nr_to_write -= nr_to_writebump;
2999         wbc->range_start = range_start;
3000         trace_ext4_da_writepages_result(inode, wbc, ret, pages_written);
3001         return ret;
3002 }
3003
3004 #define FALL_BACK_TO_NONDELALLOC 1
3005 static int ext4_nonda_switch(struct super_block *sb)
3006 {
3007         s64 free_blocks, dirty_blocks;
3008         struct ext4_sb_info *sbi = EXT4_SB(sb);
3009
3010         /*
3011          * switch to non delalloc mode if we are running low
3012          * on free block. The free block accounting via percpu
3013          * counters can get slightly wrong with percpu_counter_batch getting
3014          * accumulated on each CPU without updating global counters
3015          * Delalloc need an accurate free block accounting. So switch
3016          * to non delalloc when we are near to error range.
3017          */
3018         free_blocks  = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
3019         dirty_blocks = percpu_counter_read_positive(&sbi->s_dirtyblocks_counter);
3020         if (2 * free_blocks < 3 * dirty_blocks ||
3021                 free_blocks < (dirty_blocks + EXT4_FREEBLOCKS_WATERMARK)) {
3022                 /*
3023                  * free block count is less that 150% of dirty blocks
3024                  * or free blocks is less that watermark
3025                  */
3026                 return 1;
3027         }
3028         return 0;
3029 }
3030
3031 static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
3032                                loff_t pos, unsigned len, unsigned flags,
3033                                struct page **pagep, void **fsdata)
3034 {
3035         int ret, retries = 0;
3036         struct page *page;
3037         pgoff_t index;
3038         unsigned from, to;
3039         struct inode *inode = mapping->host;
3040         handle_t *handle;
3041
3042         index = pos >> PAGE_CACHE_SHIFT;
3043         from = pos & (PAGE_CACHE_SIZE - 1);
3044         to = from + len;
3045
3046         if (ext4_nonda_switch(inode->i_sb)) {
3047                 *fsdata = (void *)FALL_BACK_TO_NONDELALLOC;
3048                 return ext4_write_begin(file, mapping, pos,
3049                                         len, flags, pagep, fsdata);
3050         }
3051         *fsdata = (void *)0;
3052         trace_ext4_da_write_begin(inode, pos, len, flags);
3053 retry:
3054         /*
3055          * With delayed allocation, we don't log the i_disksize update
3056          * if there is delayed block allocation. But we still need
3057          * to journalling the i_disksize update if writes to the end
3058          * of file which has an already mapped buffer.
3059          */
3060         handle = ext4_journal_start(inode, 1);
3061         if (IS_ERR(handle)) {
3062                 ret = PTR_ERR(handle);
3063                 goto out;
3064         }
3065         /* We cannot recurse into the filesystem as the transaction is already
3066          * started */
3067         flags |= AOP_FLAG_NOFS;
3068
3069         page = grab_cache_page_write_begin(mapping, index, flags);
3070         if (!page) {
3071                 ext4_journal_stop(handle);
3072                 ret = -ENOMEM;
3073                 goto out;
3074         }
3075         *pagep = page;
3076
3077         ret = block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
3078                                 ext4_da_get_block_prep);
3079         if (ret < 0) {
3080                 unlock_page(page);
3081                 ext4_journal_stop(handle);
3082                 page_cache_release(page);
3083                 /*
3084                  * block_write_begin may have instantiated a few blocks
3085                  * outside i_size.  Trim these off again. Don't need
3086                  * i_size_read because we hold i_mutex.
3087                  */
3088                 if (pos + len > inode->i_size)
3089                         ext4_truncate(inode);
3090         }
3091
3092         if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
3093                 goto retry;
3094 out:
3095         return ret;
3096 }
3097
3098 /*
3099  * Check if we should update i_disksize
3100  * when write to the end of file but not require block allocation
3101  */
3102 static int ext4_da_should_update_i_disksize(struct page *page,
3103                                             unsigned long offset)
3104 {
3105         struct buffer_head *bh;
3106         struct inode *inode = page->mapping->host;
3107         unsigned int idx;
3108         int i;
3109
3110         bh = page_buffers(page);
3111         idx = offset >> inode->i_blkbits;
3112
3113         for (i = 0; i < idx; i++)
3114                 bh = bh->b_this_page;
3115
3116         if (!buffer_mapped(bh) || (buffer_delay(bh)) || buffer_unwritten(bh))
3117                 return 0;
3118         return 1;
3119 }
3120
3121 static int ext4_da_write_end(struct file *file,
3122                              struct address_space *mapping,
3123                              loff_t pos, unsigned len, unsigned copied,
3124                              struct page *page, void *fsdata)
3125 {
3126         struct inode *inode = mapping->host;
3127         int ret = 0, ret2;
3128         handle_t *handle = ext4_journal_current_handle();
3129         loff_t new_i_size;
3130         unsigned long start, end;
3131         int write_mode = (int)(unsigned long)fsdata;
3132
3133         if (write_mode == FALL_BACK_TO_NONDELALLOC) {
3134                 if (ext4_should_order_data(inode)) {
3135                         return ext4_ordered_write_end(file, mapping, pos,
3136                                         len, copied, page, fsdata);
3137                 } else if (ext4_should_writeback_data(inode)) {
3138                         return ext4_writeback_write_end(file, mapping, pos,
3139                                         len, copied, page, fsdata);
3140                 } else {
3141                         BUG();
3142                 }
3143         }
3144
3145         trace_ext4_da_write_end(inode, pos, len, copied);
3146         start = pos & (PAGE_CACHE_SIZE - 1);
3147         end = start + copied - 1;
3148
3149         /*
3150          * generic_write_end() will run mark_inode_dirty() if i_size
3151          * changes.  So let's piggyback the i_disksize mark_inode_dirty
3152          * into that.
3153          */
3154
3155         new_i_size = pos + copied;
3156         if (new_i_size > EXT4_I(inode)->i_disksize) {
3157                 if (ext4_da_should_update_i_disksize(page, end)) {
3158                         down_write(&EXT4_I(inode)->i_data_sem);
3159                         if (new_i_size > EXT4_I(inode)->i_disksize) {
3160                                 /*
3161                                  * Updating i_disksize when extending file
3162                                  * without needing block allocation
3163                                  */
3164                                 if (ext4_should_order_data(inode))
3165                                         ret = ext4_jbd2_file_inode(handle,
3166                                                                    inode);
3167
3168                                 EXT4_I(inode)->i_disksize = new_i_size;
3169                         }
3170                         up_write(&EXT4_I(inode)->i_data_sem);
3171                         /* We need to mark inode dirty even if
3172                          * new_i_size is less that inode->i_size
3173                          * bu greater than i_disksize.(hint delalloc)
3174                          */
3175                         ext4_mark_inode_dirty(handle, inode);
3176                 }
3177         }
3178         ret2 = generic_write_end(file, mapping, pos, len, copied,
3179                                                         page, fsdata);
3180         copied = ret2;
3181         if (ret2 < 0)
3182                 ret = ret2;
3183         ret2 = ext4_journal_stop(handle);
3184         if (!ret)
3185                 ret = ret2;
3186
3187         return ret ? ret : copied;
3188 }
3189
3190 static void ext4_da_invalidatepage(struct page *page, unsigned long offset)
3191 {
3192         /*
3193          * Drop reserved blocks
3194          */
3195         BUG_ON(!PageLocked(page));
3196         if (!page_has_buffers(page))
3197                 goto out;
3198
3199         ext4_da_page_release_reservation(page, offset);
3200
3201 out:
3202         ext4_invalidatepage(page, offset);
3203
3204         return;
3205 }
3206
3207 /*
3208  * Force all delayed allocation blocks to be allocated for a given inode.
3209  */
3210 int ext4_alloc_da_blocks(struct inode *inode)
3211 {
3212         trace_ext4_alloc_da_blocks(inode);
3213
3214         if (!EXT4_I(inode)->i_reserved_data_blocks &&
3215             !EXT4_I(inode)->i_reserved_meta_blocks)
3216                 return 0;
3217
3218         /*
3219          * We do something simple for now.  The filemap_flush() will
3220          * also start triggering a write of the data blocks, which is
3221          * not strictly speaking necessary (and for users of
3222          * laptop_mode, not even desirable).  However, to do otherwise
3223          * would require replicating code paths in:
3224          *
3225          * ext4_da_writepages() ->
3226          *    write_cache_pages() ---> (via passed in callback function)
3227          *        __mpage_da_writepage() -->
3228          *           mpage_add_bh_to_extent()
3229          *           mpage_da_map_blocks()
3230          *
3231          * The problem is that write_cache_pages(), located in
3232          * mm/page-writeback.c, marks pages clean in preparation for
3233          * doing I/O, which is not desirable if we're not planning on
3234          * doing I/O at all.
3235          *
3236          * We could call write_cache_pages(), and then redirty all of
3237          * the pages by calling redirty_page_for_writeback() but that
3238          * would be ugly in the extreme.  So instead we would need to
3239          * replicate parts of the code in the above functions,
3240          * simplifying them becuase we wouldn't actually intend to
3241          * write out the pages, but rather only collect contiguous
3242          * logical block extents, call the multi-block allocator, and
3243          * then update the buffer heads with the block allocations.
3244          *
3245          * For now, though, we'll cheat by calling filemap_flush(),
3246          * which will map the blocks, and start the I/O, but not
3247          * actually wait for the I/O to complete.
3248          */
3249         return filemap_flush(inode->i_mapping);
3250 }
3251
3252 /*
3253  * bmap() is special.  It gets used by applications such as lilo and by
3254  * the swapper to find the on-disk block of a specific piece of data.
3255  *
3256  * Naturally, this is dangerous if the block concerned is still in the
3257  * journal.  If somebody makes a swapfile on an ext4 data-journaling
3258  * filesystem and enables swap, then they may get a nasty shock when the
3259  * data getting swapped to that swapfile suddenly gets overwritten by
3260  * the original zero's written out previously to the journal and
3261  * awaiting writeback in the kernel's buffer cache.
3262  *
3263  * So, if we see any bmap calls her