tree-wide: fix typos "offest" -> "offset"
[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 #include <linux/workqueue.h>
41
42 #include "ext4_jbd2.h"
43 #include "xattr.h"
44 #include "acl.h"
45 #include "ext4_extents.h"
46
47 #include <trace/events/ext4.h>
48
49 #define MPAGE_DA_EXTENT_TAIL 0x01
50
51 static inline int ext4_begin_ordered_truncate(struct inode *inode,
52                                               loff_t new_size)
53 {
54         return jbd2_journal_begin_ordered_truncate(
55                                         EXT4_SB(inode->i_sb)->s_journal,
56                                         &EXT4_I(inode)->jinode,
57                                         new_size);
58 }
59
60 static void ext4_invalidatepage(struct page *page, unsigned long offset);
61
62 /*
63  * Test whether an inode is a fast symlink.
64  */
65 static int ext4_inode_is_fast_symlink(struct inode *inode)
66 {
67         int ea_blocks = EXT4_I(inode)->i_file_acl ?
68                 (inode->i_sb->s_blocksize >> 9) : 0;
69
70         return (S_ISLNK(inode->i_mode) && inode->i_blocks - ea_blocks == 0);
71 }
72
73 /*
74  * The ext4 forget function must perform a revoke if we are freeing data
75  * which has been journaled.  Metadata (eg. indirect blocks) must be
76  * revoked in all cases.
77  *
78  * "bh" may be NULL: a metadata block may have been freed from memory
79  * but there may still be a record of it in the journal, and that record
80  * still needs to be revoked.
81  *
82  * If the handle isn't valid we're not journaling, but we still need to
83  * call into ext4_journal_revoke() to put the buffer head.
84  */
85 int ext4_forget(handle_t *handle, int is_metadata, struct inode *inode,
86                 struct buffer_head *bh, ext4_fsblk_t blocknr)
87 {
88         int err;
89
90         might_sleep();
91
92         BUFFER_TRACE(bh, "enter");
93
94         jbd_debug(4, "forgetting bh %p: is_metadata = %d, mode %o, "
95                   "data mode %x\n",
96                   bh, is_metadata, inode->i_mode,
97                   test_opt(inode->i_sb, DATA_FLAGS));
98
99         /* Never use the revoke function if we are doing full data
100          * journaling: there is no need to, and a V1 superblock won't
101          * support it.  Otherwise, only skip the revoke on un-journaled
102          * data blocks. */
103
104         if (test_opt(inode->i_sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA ||
105             (!is_metadata && !ext4_should_journal_data(inode))) {
106                 if (bh) {
107                         BUFFER_TRACE(bh, "call jbd2_journal_forget");
108                         return ext4_journal_forget(handle, bh);
109                 }
110                 return 0;
111         }
112
113         /*
114          * data!=journal && (is_metadata || should_journal_data(inode))
115          */
116         BUFFER_TRACE(bh, "call ext4_journal_revoke");
117         err = ext4_journal_revoke(handle, blocknr, bh);
118         if (err)
119                 ext4_abort(inode->i_sb, __func__,
120                            "error %d when attempting revoke", err);
121         BUFFER_TRACE(bh, "exit");
122         return err;
123 }
124
125 /*
126  * Work out how many blocks we need to proceed with the next chunk of a
127  * truncate transaction.
128  */
129 static unsigned long blocks_for_truncate(struct inode *inode)
130 {
131         ext4_lblk_t needed;
132
133         needed = inode->i_blocks >> (inode->i_sb->s_blocksize_bits - 9);
134
135         /* Give ourselves just enough room to cope with inodes in which
136          * i_blocks is corrupt: we've seen disk corruptions in the past
137          * which resulted in random data in an inode which looked enough
138          * like a regular file for ext4 to try to delete it.  Things
139          * will go a bit crazy if that happens, but at least we should
140          * try not to panic the whole kernel. */
141         if (needed < 2)
142                 needed = 2;
143
144         /* But we need to bound the transaction so we don't overflow the
145          * journal. */
146         if (needed > EXT4_MAX_TRANS_DATA)
147                 needed = EXT4_MAX_TRANS_DATA;
148
149         return EXT4_DATA_TRANS_BLOCKS(inode->i_sb) + needed;
150 }
151
152 /*
153  * Truncate transactions can be complex and absolutely huge.  So we need to
154  * be able to restart the transaction at a conventient checkpoint to make
155  * sure we don't overflow the journal.
156  *
157  * start_transaction gets us a new handle for a truncate transaction,
158  * and extend_transaction tries to extend the existing one a bit.  If
159  * extend fails, we need to propagate the failure up and restart the
160  * transaction in the top-level truncate loop. --sct
161  */
162 static handle_t *start_transaction(struct inode *inode)
163 {
164         handle_t *result;
165
166         result = ext4_journal_start(inode, blocks_for_truncate(inode));
167         if (!IS_ERR(result))
168                 return result;
169
170         ext4_std_error(inode->i_sb, PTR_ERR(result));
171         return result;
172 }
173
174 /*
175  * Try to extend this transaction for the purposes of truncation.
176  *
177  * Returns 0 if we managed to create more room.  If we can't create more
178  * room, and the transaction must be restarted we return 1.
179  */
180 static int try_to_extend_transaction(handle_t *handle, struct inode *inode)
181 {
182         if (!ext4_handle_valid(handle))
183                 return 0;
184         if (ext4_handle_has_enough_credits(handle, EXT4_RESERVE_TRANS_BLOCKS+1))
185                 return 0;
186         if (!ext4_journal_extend(handle, blocks_for_truncate(inode)))
187                 return 0;
188         return 1;
189 }
190
191 /*
192  * Restart the transaction associated with *handle.  This does a commit,
193  * so before we call here everything must be consistently dirtied against
194  * this transaction.
195  */
196  int ext4_truncate_restart_trans(handle_t *handle, struct inode *inode,
197                                  int nblocks)
198 {
199         int ret;
200
201         /*
202          * Drop i_data_sem to avoid deadlock with ext4_get_blocks At this
203          * moment, get_block can be called only for blocks inside i_size since
204          * page cache has been already dropped and writes are blocked by
205          * i_mutex. So we can safely drop the i_data_sem here.
206          */
207         BUG_ON(EXT4_JOURNAL(inode) == NULL);
208         jbd_debug(2, "restarting handle %p\n", handle);
209         up_write(&EXT4_I(inode)->i_data_sem);
210         ret = ext4_journal_restart(handle, blocks_for_truncate(inode));
211         down_write(&EXT4_I(inode)->i_data_sem);
212
213         return ret;
214 }
215
216 /*
217  * Called at the last iput() if i_nlink is zero.
218  */
219 void ext4_delete_inode(struct inode *inode)
220 {
221         handle_t *handle;
222         int err;
223
224         if (ext4_should_order_data(inode))
225                 ext4_begin_ordered_truncate(inode, 0);
226         truncate_inode_pages(&inode->i_data, 0);
227
228         if (is_bad_inode(inode))
229                 goto no_delete;
230
231         handle = ext4_journal_start(inode, blocks_for_truncate(inode)+3);
232         if (IS_ERR(handle)) {
233                 ext4_std_error(inode->i_sb, PTR_ERR(handle));
234                 /*
235                  * If we're going to skip the normal cleanup, we still need to
236                  * make sure that the in-core orphan linked list is properly
237                  * cleaned up.
238                  */
239                 ext4_orphan_del(NULL, inode);
240                 goto no_delete;
241         }
242
243         if (IS_SYNC(inode))
244                 ext4_handle_sync(handle);
245         inode->i_size = 0;
246         err = ext4_mark_inode_dirty(handle, inode);
247         if (err) {
248                 ext4_warning(inode->i_sb, __func__,
249                              "couldn't mark inode dirty (err %d)", err);
250                 goto stop_handle;
251         }
252         if (inode->i_blocks)
253                 ext4_truncate(inode);
254
255         /*
256          * ext4_ext_truncate() doesn't reserve any slop when it
257          * restarts journal transactions; therefore there may not be
258          * enough credits left in the handle to remove the inode from
259          * the orphan list and set the dtime field.
260          */
261         if (!ext4_handle_has_enough_credits(handle, 3)) {
262                 err = ext4_journal_extend(handle, 3);
263                 if (err > 0)
264                         err = ext4_journal_restart(handle, 3);
265                 if (err != 0) {
266                         ext4_warning(inode->i_sb, __func__,
267                                      "couldn't extend journal (err %d)", err);
268                 stop_handle:
269                         ext4_journal_stop(handle);
270                         goto no_delete;
271                 }
272         }
273
274         /*
275          * Kill off the orphan record which ext4_truncate created.
276          * AKPM: I think this can be inside the above `if'.
277          * Note that ext4_orphan_del() has to be able to cope with the
278          * deletion of a non-existent orphan - this is because we don't
279          * know if ext4_truncate() actually created an orphan record.
280          * (Well, we could do this if we need to, but heck - it works)
281          */
282         ext4_orphan_del(handle, inode);
283         EXT4_I(inode)->i_dtime  = get_seconds();
284
285         /*
286          * One subtle ordering requirement: if anything has gone wrong
287          * (transaction abort, IO errors, whatever), then we can still
288          * do these next steps (the fs will already have been marked as
289          * having errors), but we can't free the inode if the mark_dirty
290          * fails.
291          */
292         if (ext4_mark_inode_dirty(handle, inode))
293                 /* If that failed, just do the required in-core inode clear. */
294                 clear_inode(inode);
295         else
296                 ext4_free_inode(handle, inode);
297         ext4_journal_stop(handle);
298         return;
299 no_delete:
300         clear_inode(inode);     /* We must guarantee clearing of inode... */
301 }
302
303 typedef struct {
304         __le32  *p;
305         __le32  key;
306         struct buffer_head *bh;
307 } Indirect;
308
309 static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
310 {
311         p->key = *(p->p = v);
312         p->bh = bh;
313 }
314
315 /**
316  *      ext4_block_to_path - parse the block number into array of offsets
317  *      @inode: inode in question (we are only interested in its superblock)
318  *      @i_block: block number to be parsed
319  *      @offsets: array to store the offsets in
320  *      @boundary: set this non-zero if the referred-to block is likely to be
321  *             followed (on disk) by an indirect block.
322  *
323  *      To store the locations of file's data ext4 uses a data structure common
324  *      for UNIX filesystems - tree of pointers anchored in the inode, with
325  *      data blocks at leaves and indirect blocks in intermediate nodes.
326  *      This function translates the block number into path in that tree -
327  *      return value is the path length and @offsets[n] is the offset of
328  *      pointer to (n+1)th node in the nth one. If @block is out of range
329  *      (negative or too large) warning is printed and zero returned.
330  *
331  *      Note: function doesn't find node addresses, so no IO is needed. All
332  *      we need to know is the capacity of indirect blocks (taken from the
333  *      inode->i_sb).
334  */
335
336 /*
337  * Portability note: the last comparison (check that we fit into triple
338  * indirect block) is spelled differently, because otherwise on an
339  * architecture with 32-bit longs and 8Kb pages we might get into trouble
340  * if our filesystem had 8Kb blocks. We might use long long, but that would
341  * kill us on x86. Oh, well, at least the sign propagation does not matter -
342  * i_block would have to be negative in the very beginning, so we would not
343  * get there at all.
344  */
345
346 static int ext4_block_to_path(struct inode *inode,
347                               ext4_lblk_t i_block,
348                               ext4_lblk_t offsets[4], int *boundary)
349 {
350         int ptrs = EXT4_ADDR_PER_BLOCK(inode->i_sb);
351         int ptrs_bits = EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb);
352         const long direct_blocks = EXT4_NDIR_BLOCKS,
353                 indirect_blocks = ptrs,
354                 double_blocks = (1 << (ptrs_bits * 2));
355         int n = 0;
356         int final = 0;
357
358         if (i_block < direct_blocks) {
359                 offsets[n++] = i_block;
360                 final = direct_blocks;
361         } else if ((i_block -= direct_blocks) < indirect_blocks) {
362                 offsets[n++] = EXT4_IND_BLOCK;
363                 offsets[n++] = i_block;
364                 final = ptrs;
365         } else if ((i_block -= indirect_blocks) < double_blocks) {
366                 offsets[n++] = EXT4_DIND_BLOCK;
367                 offsets[n++] = i_block >> ptrs_bits;
368                 offsets[n++] = i_block & (ptrs - 1);
369                 final = ptrs;
370         } else if (((i_block -= double_blocks) >> (ptrs_bits * 2)) < ptrs) {
371                 offsets[n++] = EXT4_TIND_BLOCK;
372                 offsets[n++] = i_block >> (ptrs_bits * 2);
373                 offsets[n++] = (i_block >> ptrs_bits) & (ptrs - 1);
374                 offsets[n++] = i_block & (ptrs - 1);
375                 final = ptrs;
376         } else {
377                 ext4_warning(inode->i_sb, "ext4_block_to_path",
378                              "block %lu > max in inode %lu",
379                              i_block + direct_blocks +
380                              indirect_blocks + double_blocks, inode->i_ino);
381         }
382         if (boundary)
383                 *boundary = final - 1 - (i_block & (ptrs - 1));
384         return n;
385 }
386
387 static int __ext4_check_blockref(const char *function, struct inode *inode,
388                                  __le32 *p, unsigned int max)
389 {
390         __le32 *bref = p;
391         unsigned int blk;
392
393         while (bref < p+max) {
394                 blk = le32_to_cpu(*bref++);
395                 if (blk &&
396                     unlikely(!ext4_data_block_valid(EXT4_SB(inode->i_sb),
397                                                     blk, 1))) {
398                         ext4_error(inode->i_sb, function,
399                                    "invalid block reference %u "
400                                    "in inode #%lu", blk, inode->i_ino);
401                         return -EIO;
402                 }
403         }
404         return 0;
405 }
406
407
408 #define ext4_check_indirect_blockref(inode, bh)                         \
409         __ext4_check_blockref(__func__, inode, (__le32 *)(bh)->b_data,  \
410                               EXT4_ADDR_PER_BLOCK((inode)->i_sb))
411
412 #define ext4_check_inode_blockref(inode)                                \
413         __ext4_check_blockref(__func__, inode, EXT4_I(inode)->i_data,   \
414                               EXT4_NDIR_BLOCKS)
415
416 /**
417  *      ext4_get_branch - read the chain of indirect blocks leading to data
418  *      @inode: inode in question
419  *      @depth: depth of the chain (1 - direct pointer, etc.)
420  *      @offsets: offsets of pointers in inode/indirect blocks
421  *      @chain: place to store the result
422  *      @err: here we store the error value
423  *
424  *      Function fills the array of triples <key, p, bh> and returns %NULL
425  *      if everything went OK or the pointer to the last filled triple
426  *      (incomplete one) otherwise. Upon the return chain[i].key contains
427  *      the number of (i+1)-th block in the chain (as it is stored in memory,
428  *      i.e. little-endian 32-bit), chain[i].p contains the address of that
429  *      number (it points into struct inode for i==0 and into the bh->b_data
430  *      for i>0) and chain[i].bh points to the buffer_head of i-th indirect
431  *      block for i>0 and NULL for i==0. In other words, it holds the block
432  *      numbers of the chain, addresses they were taken from (and where we can
433  *      verify that chain did not change) and buffer_heads hosting these
434  *      numbers.
435  *
436  *      Function stops when it stumbles upon zero pointer (absent block)
437  *              (pointer to last triple returned, *@err == 0)
438  *      or when it gets an IO error reading an indirect block
439  *              (ditto, *@err == -EIO)
440  *      or when it reads all @depth-1 indirect blocks successfully and finds
441  *      the whole chain, all way to the data (returns %NULL, *err == 0).
442  *
443  *      Need to be called with
444  *      down_read(&EXT4_I(inode)->i_data_sem)
445  */
446 static Indirect *ext4_get_branch(struct inode *inode, int depth,
447                                  ext4_lblk_t  *offsets,
448                                  Indirect chain[4], int *err)
449 {
450         struct super_block *sb = inode->i_sb;
451         Indirect *p = chain;
452         struct buffer_head *bh;
453
454         *err = 0;
455         /* i_data is not going away, no lock needed */
456         add_chain(chain, NULL, EXT4_I(inode)->i_data + *offsets);
457         if (!p->key)
458                 goto no_block;
459         while (--depth) {
460                 bh = sb_getblk(sb, le32_to_cpu(p->key));
461                 if (unlikely(!bh))
462                         goto failure;
463
464                 if (!bh_uptodate_or_lock(bh)) {
465                         if (bh_submit_read(bh) < 0) {
466                                 put_bh(bh);
467                                 goto failure;
468                         }
469                         /* validate block references */
470                         if (ext4_check_indirect_blockref(inode, bh)) {
471                                 put_bh(bh);
472                                 goto failure;
473                         }
474                 }
475
476                 add_chain(++p, bh, (__le32 *)bh->b_data + *++offsets);
477                 /* Reader: end */
478                 if (!p->key)
479                         goto no_block;
480         }
481         return NULL;
482
483 failure:
484         *err = -EIO;
485 no_block:
486         return p;
487 }
488
489 /**
490  *      ext4_find_near - find a place for allocation with sufficient locality
491  *      @inode: owner
492  *      @ind: descriptor of indirect block.
493  *
494  *      This function returns the preferred place for block allocation.
495  *      It is used when heuristic for sequential allocation fails.
496  *      Rules are:
497  *        + if there is a block to the left of our position - allocate near it.
498  *        + if pointer will live in indirect block - allocate near that block.
499  *        + if pointer will live in inode - allocate in the same
500  *          cylinder group.
501  *
502  * In the latter case we colour the starting block by the callers PID to
503  * prevent it from clashing with concurrent allocations for a different inode
504  * in the same block group.   The PID is used here so that functionally related
505  * files will be close-by on-disk.
506  *
507  *      Caller must make sure that @ind is valid and will stay that way.
508  */
509 static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
510 {
511         struct ext4_inode_info *ei = EXT4_I(inode);
512         __le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
513         __le32 *p;
514         ext4_fsblk_t bg_start;
515         ext4_fsblk_t last_block;
516         ext4_grpblk_t colour;
517         ext4_group_t block_group;
518         int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
519
520         /* Try to find previous block */
521         for (p = ind->p - 1; p >= start; p--) {
522                 if (*p)
523                         return le32_to_cpu(*p);
524         }
525
526         /* No such thing, so let's try location of indirect block */
527         if (ind->bh)
528                 return ind->bh->b_blocknr;
529
530         /*
531          * It is going to be referred to from the inode itself? OK, just put it
532          * into the same cylinder group then.
533          */
534         block_group = ei->i_block_group;
535         if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
536                 block_group &= ~(flex_size-1);
537                 if (S_ISREG(inode->i_mode))
538                         block_group++;
539         }
540         bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
541         last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
542
543         /*
544          * If we are doing delayed allocation, we don't need take
545          * colour into account.
546          */
547         if (test_opt(inode->i_sb, DELALLOC))
548                 return bg_start;
549
550         if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
551                 colour = (current->pid % 16) *
552                         (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
553         else
554                 colour = (current->pid % 16) * ((last_block - bg_start) / 16);
555         return bg_start + colour;
556 }
557
558 /**
559  *      ext4_find_goal - find a preferred place for allocation.
560  *      @inode: owner
561  *      @block:  block we want
562  *      @partial: pointer to the last triple within a chain
563  *
564  *      Normally this function find the preferred place for block allocation,
565  *      returns it.
566  *      Because this is only used for non-extent files, we limit the block nr
567  *      to 32 bits.
568  */
569 static ext4_fsblk_t ext4_find_goal(struct inode *inode, ext4_lblk_t block,
570                                    Indirect *partial)
571 {
572         ext4_fsblk_t goal;
573
574         /*
575          * XXX need to get goal block from mballoc's data structures
576          */
577
578         goal = ext4_find_near(inode, partial);
579         goal = goal & EXT4_MAX_BLOCK_FILE_PHYS;
580         return goal;
581 }
582
583 /**
584  *      ext4_blks_to_allocate: Look up the block map and count the number
585  *      of direct blocks need to be allocated for the given branch.
586  *
587  *      @branch: chain of indirect blocks
588  *      @k: number of blocks need for indirect blocks
589  *      @blks: number of data blocks to be mapped.
590  *      @blocks_to_boundary:  the offset in the indirect block
591  *
592  *      return the total number of blocks to be allocate, including the
593  *      direct and indirect blocks.
594  */
595 static int ext4_blks_to_allocate(Indirect *branch, int k, unsigned int blks,
596                                  int blocks_to_boundary)
597 {
598         unsigned int count = 0;
599
600         /*
601          * Simple case, [t,d]Indirect block(s) has not allocated yet
602          * then it's clear blocks on that path have not allocated
603          */
604         if (k > 0) {
605                 /* right now we don't handle cross boundary allocation */
606                 if (blks < blocks_to_boundary + 1)
607                         count += blks;
608                 else
609                         count += blocks_to_boundary + 1;
610                 return count;
611         }
612
613         count++;
614         while (count < blks && count <= blocks_to_boundary &&
615                 le32_to_cpu(*(branch[0].p + count)) == 0) {
616                 count++;
617         }
618         return count;
619 }
620
621 /**
622  *      ext4_alloc_blocks: multiple allocate blocks needed for a branch
623  *      @indirect_blks: the number of blocks need to allocate for indirect
624  *                      blocks
625  *
626  *      @new_blocks: on return it will store the new block numbers for
627  *      the indirect blocks(if needed) and the first direct block,
628  *      @blks:  on return it will store the total number of allocated
629  *              direct blocks
630  */
631 static int ext4_alloc_blocks(handle_t *handle, struct inode *inode,
632                              ext4_lblk_t iblock, ext4_fsblk_t goal,
633                              int indirect_blks, int blks,
634                              ext4_fsblk_t new_blocks[4], int *err)
635 {
636         struct ext4_allocation_request ar;
637         int target, i;
638         unsigned long count = 0, blk_allocated = 0;
639         int index = 0;
640         ext4_fsblk_t current_block = 0;
641         int ret = 0;
642
643         /*
644          * Here we try to allocate the requested multiple blocks at once,
645          * on a best-effort basis.
646          * To build a branch, we should allocate blocks for
647          * the indirect blocks(if not allocated yet), and at least
648          * the first direct block of this branch.  That's the
649          * minimum number of blocks need to allocate(required)
650          */
651         /* first we try to allocate the indirect blocks */
652         target = indirect_blks;
653         while (target > 0) {
654                 count = target;
655                 /* allocating blocks for indirect blocks and direct blocks */
656                 current_block = ext4_new_meta_blocks(handle, inode,
657                                                         goal, &count, err);
658                 if (*err)
659                         goto failed_out;
660
661                 BUG_ON(current_block + count > EXT4_MAX_BLOCK_FILE_PHYS);
662
663                 target -= count;
664                 /* allocate blocks for indirect blocks */
665                 while (index < indirect_blks && count) {
666                         new_blocks[index++] = current_block++;
667                         count--;
668                 }
669                 if (count > 0) {
670                         /*
671                          * save the new block number
672                          * for the first direct block
673                          */
674                         new_blocks[index] = current_block;
675                         printk(KERN_INFO "%s returned more blocks than "
676                                                 "requested\n", __func__);
677                         WARN_ON(1);
678                         break;
679                 }
680         }
681
682         target = blks - count ;
683         blk_allocated = count;
684         if (!target)
685                 goto allocated;
686         /* Now allocate data blocks */
687         memset(&ar, 0, sizeof(ar));
688         ar.inode = inode;
689         ar.goal = goal;
690         ar.len = target;
691         ar.logical = iblock;
692         if (S_ISREG(inode->i_mode))
693                 /* enable in-core preallocation only for regular files */
694                 ar.flags = EXT4_MB_HINT_DATA;
695
696         current_block = ext4_mb_new_blocks(handle, &ar, err);
697         BUG_ON(current_block + ar.len > EXT4_MAX_BLOCK_FILE_PHYS);
698
699         if (*err && (target == blks)) {
700                 /*
701                  * if the allocation failed and we didn't allocate
702                  * any blocks before
703                  */
704                 goto failed_out;
705         }
706         if (!*err) {
707                 if (target == blks) {
708                         /*
709                          * save the new block number
710                          * for the first direct block
711                          */
712                         new_blocks[index] = current_block;
713                 }
714                 blk_allocated += ar.len;
715         }
716 allocated:
717         /* total number of blocks allocated for direct blocks */
718         ret = blk_allocated;
719         *err = 0;
720         return ret;
721 failed_out:
722         for (i = 0; i < index; i++)
723                 ext4_free_blocks(handle, inode, new_blocks[i], 1, 0);
724         return ret;
725 }
726
727 /**
728  *      ext4_alloc_branch - allocate and set up a chain of blocks.
729  *      @inode: owner
730  *      @indirect_blks: number of allocated indirect blocks
731  *      @blks: number of allocated direct blocks
732  *      @offsets: offsets (in the blocks) to store the pointers to next.
733  *      @branch: place to store the chain in.
734  *
735  *      This function allocates blocks, zeroes out all but the last one,
736  *      links them into chain and (if we are synchronous) writes them to disk.
737  *      In other words, it prepares a branch that can be spliced onto the
738  *      inode. It stores the information about that chain in the branch[], in
739  *      the same format as ext4_get_branch() would do. We are calling it after
740  *      we had read the existing part of chain and partial points to the last
741  *      triple of that (one with zero ->key). Upon the exit we have the same
742  *      picture as after the successful ext4_get_block(), except that in one
743  *      place chain is disconnected - *branch->p is still zero (we did not
744  *      set the last link), but branch->key contains the number that should
745  *      be placed into *branch->p to fill that gap.
746  *
747  *      If allocation fails we free all blocks we've allocated (and forget
748  *      their buffer_heads) and return the error value the from failed
749  *      ext4_alloc_block() (normally -ENOSPC). Otherwise we set the chain
750  *      as described above and return 0.
751  */
752 static int ext4_alloc_branch(handle_t *handle, struct inode *inode,
753                              ext4_lblk_t iblock, int indirect_blks,
754                              int *blks, ext4_fsblk_t goal,
755                              ext4_lblk_t *offsets, Indirect *branch)
756 {
757         int blocksize = inode->i_sb->s_blocksize;
758         int i, n = 0;
759         int err = 0;
760         struct buffer_head *bh;
761         int num;
762         ext4_fsblk_t new_blocks[4];
763         ext4_fsblk_t current_block;
764
765         num = ext4_alloc_blocks(handle, inode, iblock, goal, indirect_blks,
766                                 *blks, new_blocks, &err);
767         if (err)
768                 return err;
769
770         branch[0].key = cpu_to_le32(new_blocks[0]);
771         /*
772          * metadata blocks and data blocks are allocated.
773          */
774         for (n = 1; n <= indirect_blks;  n++) {
775                 /*
776                  * Get buffer_head for parent block, zero it out
777                  * and set the pointer to new one, then send
778                  * parent to disk.
779                  */
780                 bh = sb_getblk(inode->i_sb, new_blocks[n-1]);
781                 branch[n].bh = bh;
782                 lock_buffer(bh);
783                 BUFFER_TRACE(bh, "call get_create_access");
784                 err = ext4_journal_get_create_access(handle, bh);
785                 if (err) {
786                         /* Don't brelse(bh) here; it's done in
787                          * ext4_journal_forget() below */
788                         unlock_buffer(bh);
789                         goto failed;
790                 }
791
792                 memset(bh->b_data, 0, blocksize);
793                 branch[n].p = (__le32 *) bh->b_data + offsets[n];
794                 branch[n].key = cpu_to_le32(new_blocks[n]);
795                 *branch[n].p = branch[n].key;
796                 if (n == indirect_blks) {
797                         current_block = new_blocks[n];
798                         /*
799                          * End of chain, update the last new metablock of
800                          * the chain to point to the new allocated
801                          * data blocks numbers
802                          */
803                         for (i = 1; i < num; i++)
804                                 *(branch[n].p + i) = cpu_to_le32(++current_block);
805                 }
806                 BUFFER_TRACE(bh, "marking uptodate");
807                 set_buffer_uptodate(bh);
808                 unlock_buffer(bh);
809
810                 BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
811                 err = ext4_handle_dirty_metadata(handle, inode, bh);
812                 if (err)
813                         goto failed;
814         }
815         *blks = num;
816         return err;
817 failed:
818         /* Allocation failed, free what we already allocated */
819         for (i = 1; i <= n ; i++) {
820                 BUFFER_TRACE(branch[i].bh, "call jbd2_journal_forget");
821                 ext4_journal_forget(handle, branch[i].bh);
822         }
823         for (i = 0; i < indirect_blks; i++)
824                 ext4_free_blocks(handle, inode, new_blocks[i], 1, 0);
825
826         ext4_free_blocks(handle, inode, new_blocks[i], num, 0);
827
828         return err;
829 }
830
831 /**
832  * ext4_splice_branch - splice the allocated branch onto inode.
833  * @inode: owner
834  * @block: (logical) number of block we are adding
835  * @chain: chain of indirect blocks (with a missing link - see
836  *      ext4_alloc_branch)
837  * @where: location of missing link
838  * @num:   number of indirect blocks we are adding
839  * @blks:  number of direct blocks we are adding
840  *
841  * This function fills the missing link and does all housekeeping needed in
842  * inode (->i_blocks, etc.). In case of success we end up with the full
843  * chain to new block and return 0.
844  */
845 static int ext4_splice_branch(handle_t *handle, struct inode *inode,
846                               ext4_lblk_t block, Indirect *where, int num,
847                               int blks)
848 {
849         int i;
850         int err = 0;
851         ext4_fsblk_t current_block;
852
853         /*
854          * If we're splicing into a [td]indirect block (as opposed to the
855          * inode) then we need to get write access to the [td]indirect block
856          * before the splice.
857          */
858         if (where->bh) {
859                 BUFFER_TRACE(where->bh, "get_write_access");
860                 err = ext4_journal_get_write_access(handle, where->bh);
861                 if (err)
862                         goto err_out;
863         }
864         /* That's it */
865
866         *where->p = where->key;
867
868         /*
869          * Update the host buffer_head or inode to point to more just allocated
870          * direct blocks blocks
871          */
872         if (num == 0 && blks > 1) {
873                 current_block = le32_to_cpu(where->key) + 1;
874                 for (i = 1; i < blks; i++)
875                         *(where->p + i) = cpu_to_le32(current_block++);
876         }
877
878         /* We are done with atomic stuff, now do the rest of housekeeping */
879         /* had we spliced it onto indirect block? */
880         if (where->bh) {
881                 /*
882                  * If we spliced it onto an indirect block, we haven't
883                  * altered the inode.  Note however that if it is being spliced
884                  * onto an indirect block at the very end of the file (the
885                  * file is growing) then we *will* alter the inode to reflect
886                  * the new i_size.  But that is not done here - it is done in
887                  * generic_commit_write->__mark_inode_dirty->ext4_dirty_inode.
888                  */
889                 jbd_debug(5, "splicing indirect only\n");
890                 BUFFER_TRACE(where->bh, "call ext4_handle_dirty_metadata");
891                 err = ext4_handle_dirty_metadata(handle, inode, where->bh);
892                 if (err)
893                         goto err_out;
894         } else {
895                 /*
896                  * OK, we spliced it into the inode itself on a direct block.
897                  */
898                 ext4_mark_inode_dirty(handle, inode);
899                 jbd_debug(5, "splicing direct\n");
900         }
901         return err;
902
903 err_out:
904         for (i = 1; i <= num; i++) {
905                 BUFFER_TRACE(where[i].bh, "call jbd2_journal_forget");
906                 ext4_journal_forget(handle, where[i].bh);
907                 ext4_free_blocks(handle, inode,
908                                         le32_to_cpu(where[i-1].key), 1, 0);
909         }
910         ext4_free_blocks(handle, inode, le32_to_cpu(where[num].key), blks, 0);
911
912         return err;
913 }
914
915 /*
916  * The ext4_ind_get_blocks() function handles non-extents inodes
917  * (i.e., using the traditional indirect/double-indirect i_blocks
918  * scheme) for ext4_get_blocks().
919  *
920  * Allocation strategy is simple: if we have to allocate something, we will
921  * have to go the whole way to leaf. So let's do it before attaching anything
922  * to tree, set linkage between the newborn blocks, write them if sync is
923  * required, recheck the path, free and repeat if check fails, otherwise
924  * set the last missing link (that will protect us from any truncate-generated
925  * removals - all blocks on the path are immune now) and possibly force the
926  * write on the parent block.
927  * That has a nice additional property: no special recovery from the failed
928  * allocations is needed - we simply release blocks and do not touch anything
929  * reachable from inode.
930  *
931  * `handle' can be NULL if create == 0.
932  *
933  * return > 0, # of blocks mapped or allocated.
934  * return = 0, if plain lookup failed.
935  * return < 0, error case.
936  *
937  * The ext4_ind_get_blocks() function should be called with
938  * down_write(&EXT4_I(inode)->i_data_sem) if allocating filesystem
939  * blocks (i.e., flags has EXT4_GET_BLOCKS_CREATE set) or
940  * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system
941  * blocks.
942  */
943 static int ext4_ind_get_blocks(handle_t *handle, struct inode *inode,
944                                ext4_lblk_t iblock, unsigned int maxblocks,
945                                struct buffer_head *bh_result,
946                                int flags)
947 {
948         int err = -EIO;
949         ext4_lblk_t offsets[4];
950         Indirect chain[4];
951         Indirect *partial;
952         ext4_fsblk_t goal;
953         int indirect_blks;
954         int blocks_to_boundary = 0;
955         int depth;
956         int count = 0;
957         ext4_fsblk_t first_block = 0;
958
959         J_ASSERT(!(EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL));
960         J_ASSERT(handle != NULL || (flags & EXT4_GET_BLOCKS_CREATE) == 0);
961         depth = ext4_block_to_path(inode, iblock, offsets,
962                                    &blocks_to_boundary);
963
964         if (depth == 0)
965                 goto out;
966
967         partial = ext4_get_branch(inode, depth, offsets, chain, &err);
968
969         /* Simplest case - block found, no allocation needed */
970         if (!partial) {
971                 first_block = le32_to_cpu(chain[depth - 1].key);
972                 clear_buffer_new(bh_result);
973                 count++;
974                 /*map more blocks*/
975                 while (count < maxblocks && count <= blocks_to_boundary) {
976                         ext4_fsblk_t blk;
977
978                         blk = le32_to_cpu(*(chain[depth-1].p + count));
979
980                         if (blk == first_block + count)
981                                 count++;
982                         else
983                                 break;
984                 }
985                 goto got_it;
986         }
987
988         /* Next simple case - plain lookup or failed read of indirect block */
989         if ((flags & EXT4_GET_BLOCKS_CREATE) == 0 || err == -EIO)
990                 goto cleanup;
991
992         /*
993          * Okay, we need to do block allocation.
994         */
995         goal = ext4_find_goal(inode, iblock, partial);
996
997         /* the number of blocks need to allocate for [d,t]indirect blocks */
998         indirect_blks = (chain + depth) - partial - 1;
999
1000         /*
1001          * Next look up the indirect map to count the totoal number of
1002          * direct blocks to allocate for this branch.
1003          */
1004         count = ext4_blks_to_allocate(partial, indirect_blks,
1005                                         maxblocks, blocks_to_boundary);
1006         /*
1007          * Block out ext4_truncate while we alter the tree
1008          */
1009         err = ext4_alloc_branch(handle, inode, iblock, indirect_blks,
1010                                 &count, goal,
1011                                 offsets + (partial - chain), partial);
1012
1013         /*
1014          * The ext4_splice_branch call will free and forget any buffers
1015          * on the new chain if there is a failure, but that risks using
1016          * up transaction credits, especially for bitmaps where the
1017          * credits cannot be returned.  Can we handle this somehow?  We
1018          * may need to return -EAGAIN upwards in the worst case.  --sct
1019          */
1020         if (!err)
1021                 err = ext4_splice_branch(handle, inode, iblock,
1022                                          partial, indirect_blks, count);
1023         else
1024                 goto cleanup;
1025
1026         set_buffer_new(bh_result);
1027 got_it:
1028         map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
1029         if (count > blocks_to_boundary)
1030                 set_buffer_boundary(bh_result);
1031         err = count;
1032         /* Clean up and exit */
1033         partial = chain + depth - 1;    /* the whole chain */
1034 cleanup:
1035         while (partial > chain) {
1036                 BUFFER_TRACE(partial->bh, "call brelse");
1037                 brelse(partial->bh);
1038                 partial--;
1039         }
1040         BUFFER_TRACE(bh_result, "returned");
1041 out:
1042         return err;
1043 }
1044
1045 qsize_t ext4_get_reserved_space(struct inode *inode)
1046 {
1047         unsigned long long total;
1048
1049         spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
1050         total = EXT4_I(inode)->i_reserved_data_blocks +
1051                 EXT4_I(inode)->i_reserved_meta_blocks;
1052         spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1053
1054         return total;
1055 }
1056 /*
1057  * Calculate the number of metadata blocks need to reserve
1058  * to allocate @blocks for non extent file based file
1059  */
1060 static int ext4_indirect_calc_metadata_amount(struct inode *inode, int blocks)
1061 {
1062         int icap = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1063         int ind_blks, dind_blks, tind_blks;
1064
1065         /* number of new indirect blocks needed */
1066         ind_blks = (blocks + icap - 1) / icap;
1067
1068         dind_blks = (ind_blks + icap - 1) / icap;
1069
1070         tind_blks = 1;
1071
1072         return ind_blks + dind_blks + tind_blks;
1073 }
1074
1075 /*
1076  * Calculate the number of metadata blocks need to reserve
1077  * to allocate given number of blocks
1078  */
1079 static int ext4_calc_metadata_amount(struct inode *inode, int blocks)
1080 {
1081         if (!blocks)
1082                 return 0;
1083
1084         if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL)
1085                 return ext4_ext_calc_metadata_amount(inode, blocks);
1086
1087         return ext4_indirect_calc_metadata_amount(inode, blocks);
1088 }
1089
1090 static void ext4_da_update_reserve_space(struct inode *inode, int used)
1091 {
1092         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
1093         int total, mdb, mdb_free;
1094
1095         spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
1096         /* recalculate the number of metablocks still need to be reserved */
1097         total = EXT4_I(inode)->i_reserved_data_blocks - used;
1098         mdb = ext4_calc_metadata_amount(inode, total);
1099
1100         /* figure out how many metablocks to release */
1101         BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
1102         mdb_free = EXT4_I(inode)->i_reserved_meta_blocks - mdb;
1103
1104         if (mdb_free) {
1105                 /* Account for allocated meta_blocks */
1106                 mdb_free -= EXT4_I(inode)->i_allocated_meta_blocks;
1107
1108                 /* update fs dirty blocks counter */
1109                 percpu_counter_sub(&sbi->s_dirtyblocks_counter, mdb_free);
1110                 EXT4_I(inode)->i_allocated_meta_blocks = 0;
1111                 EXT4_I(inode)->i_reserved_meta_blocks = mdb;
1112         }
1113
1114         /* update per-inode reservations */
1115         BUG_ON(used  > EXT4_I(inode)->i_reserved_data_blocks);
1116         EXT4_I(inode)->i_reserved_data_blocks -= used;
1117         spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1118
1119         /*
1120          * free those over-booking quota for metadata blocks
1121          */
1122         if (mdb_free)
1123                 vfs_dq_release_reservation_block(inode, mdb_free);
1124
1125         /*
1126          * If we have done all the pending block allocations and if
1127          * there aren't any writers on the inode, we can discard the
1128          * inode's preallocations.
1129          */
1130         if (!total && (atomic_read(&inode->i_writecount) == 0))
1131                 ext4_discard_preallocations(inode);
1132 }
1133
1134 static int check_block_validity(struct inode *inode, const char *msg,
1135                                 sector_t logical, sector_t phys, int len)
1136 {
1137         if (!ext4_data_block_valid(EXT4_SB(inode->i_sb), phys, len)) {
1138                 ext4_error(inode->i_sb, msg,
1139                            "inode #%lu logical block %llu mapped to %llu "
1140                            "(size %d)", inode->i_ino,
1141                            (unsigned long long) logical,
1142                            (unsigned long long) phys, len);
1143                 return -EIO;
1144         }
1145         return 0;
1146 }
1147
1148 /*
1149  * Return the number of contiguous dirty pages in a given inode
1150  * starting at page frame idx.
1151  */
1152 static pgoff_t ext4_num_dirty_pages(struct inode *inode, pgoff_t idx,
1153                                     unsigned int max_pages)
1154 {
1155         struct address_space *mapping = inode->i_mapping;
1156         pgoff_t index;
1157         struct pagevec pvec;
1158         pgoff_t num = 0;
1159         int i, nr_pages, done = 0;
1160
1161         if (max_pages == 0)
1162                 return 0;
1163         pagevec_init(&pvec, 0);
1164         while (!done) {
1165                 index = idx;
1166                 nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
1167                                               PAGECACHE_TAG_DIRTY,
1168                                               (pgoff_t)PAGEVEC_SIZE);
1169                 if (nr_pages == 0)
1170                         break;
1171                 for (i = 0; i < nr_pages; i++) {
1172                         struct page *page = pvec.pages[i];
1173                         struct buffer_head *bh, *head;
1174
1175                         lock_page(page);
1176                         if (unlikely(page->mapping != mapping) ||
1177                             !PageDirty(page) ||
1178                             PageWriteback(page) ||
1179                             page->index != idx) {
1180                                 done = 1;
1181                                 unlock_page(page);
1182                                 break;
1183                         }
1184                         if (page_has_buffers(page)) {
1185                                 bh = head = page_buffers(page);
1186                                 do {
1187                                         if (!buffer_delay(bh) &&
1188                                             !buffer_unwritten(bh))
1189                                                 done = 1;
1190                                         bh = bh->b_this_page;
1191                                 } while (!done && (bh != head));
1192                         }
1193                         unlock_page(page);
1194                         if (done)
1195                                 break;
1196                         idx++;
1197                         num++;
1198                         if (num >= max_pages)
1199                                 break;
1200                 }
1201                 pagevec_release(&pvec);
1202         }
1203         return num;
1204 }
1205
1206 /*
1207  * The ext4_get_blocks() function tries to look up the requested blocks,
1208  * and returns if the blocks are already mapped.
1209  *
1210  * Otherwise it takes the write lock of the i_data_sem and allocate blocks
1211  * and store the allocated blocks in the result buffer head and mark it
1212  * mapped.
1213  *
1214  * If file type is extents based, it will call ext4_ext_get_blocks(),
1215  * Otherwise, call with ext4_ind_get_blocks() to handle indirect mapping
1216  * based files
1217  *
1218  * On success, it returns the number of blocks being mapped or allocate.
1219  * if create==0 and the blocks are pre-allocated and uninitialized block,
1220  * the result buffer head is unmapped. If the create ==1, it will make sure
1221  * the buffer head is mapped.
1222  *
1223  * It returns 0 if plain look up failed (blocks have not been allocated), in
1224  * that casem, buffer head is unmapped
1225  *
1226  * It returns the error in case of allocation failure.
1227  */
1228 int ext4_get_blocks(handle_t *handle, struct inode *inode, sector_t block,
1229                     unsigned int max_blocks, struct buffer_head *bh,
1230                     int flags)
1231 {
1232         int retval;
1233
1234         clear_buffer_mapped(bh);
1235         clear_buffer_unwritten(bh);
1236
1237         ext_debug("ext4_get_blocks(): inode %lu, flag %d, max_blocks %u,"
1238                   "logical block %lu\n", inode->i_ino, flags, max_blocks,
1239                   (unsigned long)block);
1240         /*
1241          * Try to see if we can get the block without requesting a new
1242          * file system block.
1243          */
1244         down_read((&EXT4_I(inode)->i_data_sem));
1245         if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) {
1246                 retval =  ext4_ext_get_blocks(handle, inode, block, max_blocks,
1247                                 bh, 0);
1248         } else {
1249                 retval = ext4_ind_get_blocks(handle, inode, block, max_blocks,
1250                                              bh, 0);
1251         }
1252         up_read((&EXT4_I(inode)->i_data_sem));
1253
1254         if (retval > 0 && buffer_mapped(bh)) {
1255                 int ret = check_block_validity(inode, "file system corruption",
1256                                                block, bh->b_blocknr, retval);
1257                 if (ret != 0)
1258                         return ret;
1259         }
1260
1261         /* If it is only a block(s) look up */
1262         if ((flags & EXT4_GET_BLOCKS_CREATE) == 0)
1263                 return retval;
1264
1265         /*
1266          * Returns if the blocks have already allocated
1267          *
1268          * Note that if blocks have been preallocated
1269          * ext4_ext_get_block() returns th create = 0
1270          * with buffer head unmapped.
1271          */
1272         if (retval > 0 && buffer_mapped(bh))
1273                 return retval;
1274
1275         /*
1276          * When we call get_blocks without the create flag, the
1277          * BH_Unwritten flag could have gotten set if the blocks
1278          * requested were part of a uninitialized extent.  We need to
1279          * clear this flag now that we are committed to convert all or
1280          * part of the uninitialized extent to be an initialized
1281          * extent.  This is because we need to avoid the combination
1282          * of BH_Unwritten and BH_Mapped flags being simultaneously
1283          * set on the buffer_head.
1284          */
1285         clear_buffer_unwritten(bh);
1286
1287         /*
1288          * New blocks allocate and/or writing to uninitialized extent
1289          * will possibly result in updating i_data, so we take
1290          * the write lock of i_data_sem, and call get_blocks()
1291          * with create == 1 flag.
1292          */
1293         down_write((&EXT4_I(inode)->i_data_sem));
1294
1295         /*
1296          * if the caller is from delayed allocation writeout path
1297          * we have already reserved fs blocks for allocation
1298          * let the underlying get_block() function know to
1299          * avoid double accounting
1300          */
1301         if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
1302                 EXT4_I(inode)->i_delalloc_reserved_flag = 1;
1303         /*
1304          * We need to check for EXT4 here because migrate
1305          * could have changed the inode type in between
1306          */
1307         if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) {
1308                 retval =  ext4_ext_get_blocks(handle, inode, block, max_blocks,
1309                                               bh, flags);
1310         } else {
1311                 retval = ext4_ind_get_blocks(handle, inode, block,
1312                                              max_blocks, bh, flags);
1313
1314                 if (retval > 0 && buffer_new(bh)) {
1315                         /*
1316                          * We allocated new blocks which will result in
1317                          * i_data's format changing.  Force the migrate
1318                          * to fail by clearing migrate flags
1319                          */
1320                         EXT4_I(inode)->i_state &= ~EXT4_STATE_EXT_MIGRATE;
1321                 }
1322         }
1323
1324         if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
1325                 EXT4_I(inode)->i_delalloc_reserved_flag = 0;
1326
1327         /*
1328          * Update reserved blocks/metadata blocks after successful
1329          * block allocation which had been deferred till now.
1330          */
1331         if ((retval > 0) && (flags & EXT4_GET_BLOCKS_UPDATE_RESERVE_SPACE))
1332                 ext4_da_update_reserve_space(inode, retval);
1333
1334         up_write((&EXT4_I(inode)->i_data_sem));
1335         if (retval > 0 && buffer_mapped(bh)) {
1336                 int ret = check_block_validity(inode, "file system "
1337                                                "corruption after allocation",
1338                                                block, bh->b_blocknr, retval);
1339                 if (ret != 0)
1340                         return ret;
1341         }
1342         return retval;
1343 }
1344
1345 /* Maximum number of blocks we map for direct IO at once. */
1346 #define DIO_MAX_BLOCKS 4096
1347
1348 int ext4_get_block(struct inode *inode, sector_t iblock,
1349                    struct buffer_head *bh_result, int create)
1350 {
1351         handle_t *handle = ext4_journal_current_handle();
1352         int ret = 0, started = 0;
1353         unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
1354         int dio_credits;
1355
1356         if (create && !handle) {
1357                 /* Direct IO write... */
1358                 if (max_blocks > DIO_MAX_BLOCKS)
1359                         max_blocks = DIO_MAX_BLOCKS;
1360                 dio_credits = ext4_chunk_trans_blocks(inode, max_blocks);
1361                 handle = ext4_journal_start(inode, dio_credits);
1362                 if (IS_ERR(handle)) {
1363                         ret = PTR_ERR(handle);
1364                         goto out;
1365                 }
1366                 started = 1;
1367         }
1368
1369         ret = ext4_get_blocks(handle, inode, iblock, max_blocks, bh_result,
1370                               create ? EXT4_GET_BLOCKS_CREATE : 0);
1371         if (ret > 0) {
1372                 bh_result->b_size = (ret << inode->i_blkbits);
1373                 ret = 0;
1374         }
1375         if (started)
1376                 ext4_journal_stop(handle);
1377 out:
1378         return ret;
1379 }
1380
1381 /*
1382  * `handle' can be NULL if create is zero
1383  */
1384 struct buffer_head *ext4_getblk(handle_t *handle, struct inode *inode,
1385                                 ext4_lblk_t block, int create, int *errp)
1386 {
1387         struct buffer_head dummy;
1388         int fatal = 0, err;
1389         int flags = 0;
1390
1391         J_ASSERT(handle != NULL || create == 0);
1392
1393         dummy.b_state = 0;
1394         dummy.b_blocknr = -1000;
1395         buffer_trace_init(&dummy.b_history);
1396         if (create)
1397                 flags |= EXT4_GET_BLOCKS_CREATE;
1398         err = ext4_get_blocks(handle, inode, block, 1, &dummy, flags);
1399         /*
1400          * ext4_get_blocks() returns number of blocks mapped. 0 in
1401          * case of a HOLE.
1402          */
1403         if (err > 0) {
1404                 if (err > 1)
1405                         WARN_ON(1);
1406                 err = 0;
1407         }
1408         *errp = err;
1409         if (!err && buffer_mapped(&dummy)) {
1410                 struct buffer_head *bh;
1411                 bh = sb_getblk(inode->i_sb, dummy.b_blocknr);
1412                 if (!bh) {
1413                         *errp = -EIO;
1414                         goto err;
1415                 }
1416                 if (buffer_new(&dummy)) {
1417                         J_ASSERT(create != 0);
1418                         J_ASSERT(handle != NULL);
1419
1420                         /*
1421                          * Now that we do not always journal data, we should
1422                          * keep in mind whether this should always journal the
1423                          * new buffer as metadata.  For now, regular file
1424                          * writes use ext4_get_block instead, so it's not a
1425                          * problem.
1426                          */
1427                         lock_buffer(bh);
1428                         BUFFER_TRACE(bh, "call get_create_access");
1429                         fatal = ext4_journal_get_create_access(handle, bh);
1430                         if (!fatal && !buffer_uptodate(bh)) {
1431                                 memset(bh->b_data, 0, inode->i_sb->s_blocksize);
1432                                 set_buffer_uptodate(bh);
1433                         }
1434                         unlock_buffer(bh);
1435                         BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
1436                         err = ext4_handle_dirty_metadata(handle, inode, bh);
1437                         if (!fatal)
1438                                 fatal = err;
1439                 } else {
1440                         BUFFER_TRACE(bh, "not a new buffer");
1441                 }
1442                 if (fatal) {
1443                         *errp = fatal;
1444                         brelse(bh);
1445                         bh = NULL;
1446                 }
1447                 return bh;
1448         }
1449 err:
1450         return NULL;
1451 }
1452
1453 struct buffer_head *ext4_bread(handle_t *handle, struct inode *inode,
1454                                ext4_lblk_t block, int create, int *err)
1455 {
1456         struct buffer_head *bh;
1457
1458         bh = ext4_getblk(handle, inode, block, create, err);
1459         if (!bh)
1460                 return bh;
1461         if (buffer_uptodate(bh))
1462                 return bh;
1463         ll_rw_block(READ_META, 1, &bh);
1464         wait_on_buffer(bh);
1465         if (buffer_uptodate(bh))
1466                 return bh;
1467         put_bh(bh);
1468         *err = -EIO;
1469         return NULL;
1470 }
1471
1472 static int walk_page_buffers(handle_t *handle,
1473                              struct buffer_head *head,
1474                              unsigned from,
1475                              unsigned to,
1476                              int *partial,
1477                              int (*fn)(handle_t *handle,
1478                                        struct buffer_head *bh))
1479 {
1480         struct buffer_head *bh;
1481         unsigned block_start, block_end;
1482         unsigned blocksize = head->b_size;
1483         int err, ret = 0;
1484         struct buffer_head *next;
1485
1486         for (bh = head, block_start = 0;
1487              ret == 0 && (bh != head || !block_start);
1488              block_start = block_end, bh = next) {
1489                 next = bh->b_this_page;
1490                 block_end = block_start + blocksize;
1491                 if (block_end <= from || block_start >= to) {
1492                         if (partial && !buffer_uptodate(bh))
1493                                 *partial = 1;
1494                         continue;
1495                 }
1496                 err = (*fn)(handle, bh);
1497                 if (!ret)
1498                         ret = err;
1499         }
1500         return ret;
1501 }
1502
1503 /*
1504  * To preserve ordering, it is essential that the hole instantiation and
1505  * the data write be encapsulated in a single transaction.  We cannot
1506  * close off a transaction and start a new one between the ext4_get_block()
1507  * and the commit_write().  So doing the jbd2_journal_start at the start of
1508  * prepare_write() is the right place.
1509  *
1510  * Also, this function can nest inside ext4_writepage() ->
1511  * block_write_full_page(). In that case, we *know* that ext4_writepage()
1512  * has generated enough buffer credits to do the whole page.  So we won't
1513  * block on the journal in that case, which is good, because the caller may
1514  * be PF_MEMALLOC.
1515  *
1516  * By accident, ext4 can be reentered when a transaction is open via
1517  * quota file writes.  If we were to commit the transaction while thus
1518  * reentered, there can be a deadlock - we would be holding a quota
1519  * lock, and the commit would never complete if another thread had a
1520  * transaction open and was blocking on the quota lock - a ranking
1521  * violation.
1522  *
1523  * So what we do is to rely on the fact that jbd2_journal_stop/journal_start
1524  * will _not_ run commit under these circumstances because handle->h_ref
1525  * is elevated.  We'll still have enough credits for the tiny quotafile
1526  * write.
1527  */
1528 static int do_journal_get_write_access(handle_t *handle,
1529                                        struct buffer_head *bh)
1530 {
1531         if (!buffer_mapped(bh) || buffer_freed(bh))
1532                 return 0;
1533         return ext4_journal_get_write_access(handle, bh);
1534 }
1535
1536 static int ext4_write_begin(struct file *file, struct address_space *mapping,
1537                             loff_t pos, unsigned len, unsigned flags,
1538                             struct page **pagep, void **fsdata)
1539 {
1540         struct inode *inode = mapping->host;
1541         int ret, needed_blocks;
1542         handle_t *handle;
1543         int retries = 0;
1544         struct page *page;
1545         pgoff_t index;
1546         unsigned from, to;
1547
1548         trace_ext4_write_begin(inode, pos, len, flags);
1549         /*
1550          * Reserve one block more for addition to orphan list in case
1551          * we allocate blocks but write fails for some reason
1552          */
1553         needed_blocks = ext4_writepage_trans_blocks(inode) + 1;
1554         index = pos >> PAGE_CACHE_SHIFT;
1555         from = pos & (PAGE_CACHE_SIZE - 1);
1556         to = from + len;
1557
1558 retry:
1559         handle = ext4_journal_start(inode, needed_blocks);
1560         if (IS_ERR(handle)) {
1561                 ret = PTR_ERR(handle);
1562                 goto out;
1563         }
1564
1565         /* We cannot recurse into the filesystem as the transaction is already
1566          * started */
1567         flags |= AOP_FLAG_NOFS;
1568
1569         page = grab_cache_page_write_begin(mapping, index, flags);
1570         if (!page) {
1571                 ext4_journal_stop(handle);
1572                 ret = -ENOMEM;
1573                 goto out;
1574         }
1575         *pagep = page;
1576
1577         ret = block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
1578                                 ext4_get_block);
1579
1580         if (!ret && ext4_should_journal_data(inode)) {
1581                 ret = walk_page_buffers(handle, page_buffers(page),
1582                                 from, to, NULL, do_journal_get_write_access);
1583         }
1584
1585         if (ret) {
1586                 unlock_page(page);
1587                 page_cache_release(page);
1588                 /*
1589                  * block_write_begin may have instantiated a few blocks
1590                  * outside i_size.  Trim these off again. Don't need
1591                  * i_size_read because we hold i_mutex.
1592                  *
1593                  * Add inode to orphan list in case we crash before
1594                  * truncate finishes
1595                  */
1596                 if (pos + len > inode->i_size && ext4_can_truncate(inode))
1597                         ext4_orphan_add(handle, inode);
1598
1599                 ext4_journal_stop(handle);
1600                 if (pos + len > inode->i_size) {
1601                         ext4_truncate(inode);
1602                         /*
1603                          * If truncate failed early the inode might
1604                          * still be on the orphan list; we need to
1605                          * make sure the inode is removed from the
1606                          * orphan list in that case.
1607                          */
1608                         if (inode->i_nlink)
1609                                 ext4_orphan_del(NULL, inode);
1610                 }
1611         }
1612
1613         if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
1614                 goto retry;
1615 out:
1616         return ret;
1617 }
1618
1619 /* For write_end() in data=journal mode */
1620 static int write_end_fn(handle_t *handle, struct buffer_head *bh)
1621 {
1622         if (!buffer_mapped(bh) || buffer_freed(bh))
1623                 return 0;
1624         set_buffer_uptodate(bh);
1625         return ext4_handle_dirty_metadata(handle, NULL, bh);
1626 }
1627
1628 static int ext4_generic_write_end(struct file *file,
1629                                   struct address_space *mapping,
1630                                   loff_t pos, unsigned len, unsigned copied,
1631                                   struct page *page, void *fsdata)
1632 {
1633         int i_size_changed = 0;
1634         struct inode *inode = mapping->host;
1635         handle_t *handle = ext4_journal_current_handle();
1636
1637         copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
1638
1639         /*
1640          * No need to use i_size_read() here, the i_size
1641          * cannot change under us because we hold i_mutex.
1642          *
1643          * But it's important to update i_size while still holding page lock:
1644          * page writeout could otherwise come in and zero beyond i_size.
1645          */
1646         if (pos + copied > inode->i_size) {
1647                 i_size_write(inode, pos + copied);
1648                 i_size_changed = 1;
1649         }
1650
1651         if (pos + copied >  EXT4_I(inode)->i_disksize) {
1652                 /* We need to mark inode dirty even if
1653                  * new_i_size is less that inode->i_size
1654                  * bu greater than i_disksize.(hint delalloc)
1655                  */
1656                 ext4_update_i_disksize(inode, (pos + copied));
1657                 i_size_changed = 1;
1658         }
1659         unlock_page(page);
1660         page_cache_release(page);
1661
1662         /*
1663          * Don't mark the inode dirty under page lock. First, it unnecessarily
1664          * makes the holding time of page lock longer. Second, it forces lock
1665          * ordering of page lock and transaction start for journaling
1666          * filesystems.
1667          */
1668         if (i_size_changed)
1669                 ext4_mark_inode_dirty(handle, inode);
1670
1671         return copied;
1672 }
1673
1674 /*
1675  * We need to pick up the new inode size which generic_commit_write gave us
1676  * `file' can be NULL - eg, when called from page_symlink().
1677  *
1678  * ext4 never places buffers on inode->i_mapping->private_list.  metadata
1679  * buffers are managed internally.
1680  */
1681 static int ext4_ordered_write_end(struct file *file,
1682                                   struct address_space *mapping,
1683                                   loff_t pos, unsigned len, unsigned copied,
1684                                   struct page *page, void *fsdata)
1685 {
1686         handle_t *handle = ext4_journal_current_handle();
1687         struct inode *inode = mapping->host;
1688         int ret = 0, ret2;
1689
1690         trace_ext4_ordered_write_end(inode, pos, len, copied);
1691         ret = ext4_jbd2_file_inode(handle, inode);
1692
1693         if (ret == 0) {
1694                 ret2 = ext4_generic_write_end(file, mapping, pos, len, copied,
1695                                                         page, fsdata);
1696                 copied = ret2;
1697                 if (pos + len > inode->i_size && ext4_can_truncate(inode))
1698                         /* if we have allocated more blocks and copied
1699                          * less. We will have blocks allocated outside
1700                          * inode->i_size. So truncate them
1701                          */
1702                         ext4_orphan_add(handle, inode);
1703                 if (ret2 < 0)
1704                         ret = ret2;
1705         }
1706         ret2 = ext4_journal_stop(handle);
1707         if (!ret)
1708                 ret = ret2;
1709
1710         if (pos + len > inode->i_size) {
1711                 ext4_truncate(inode);
1712                 /*
1713                  * If truncate failed early the inode might still be
1714                  * on the orphan list; we need to make sure the inode
1715                  * is removed from the orphan list in that case.
1716                  */
1717                 if (inode->i_nlink)
1718                         ext4_orphan_del(NULL, inode);
1719         }
1720
1721
1722         return ret ? ret : copied;
1723 }
1724
1725 static int ext4_writeback_write_end(struct file *file,
1726                                     struct address_space *mapping,
1727                                     loff_t pos, unsigned len, unsigned copied,
1728                                     struct page *page, void *fsdata)
1729 {
1730         handle_t *handle = ext4_journal_current_handle();
1731         struct inode *inode = mapping->host;
1732         int ret = 0, ret2;
1733
1734         trace_ext4_writeback_write_end(inode, pos, len, copied);
1735         ret2 = ext4_generic_write_end(file, mapping, pos, len, copied,
1736                                                         page, fsdata);
1737         copied = ret2;
1738         if (pos + len > inode->i_size && ext4_can_truncate(inode))
1739                 /* if we have allocated more blocks and copied
1740                  * less. We will have blocks allocated outside
1741                  * inode->i_size. So truncate them
1742                  */
1743                 ext4_orphan_add(handle, inode);
1744
1745         if (ret2 < 0)
1746                 ret = ret2;
1747
1748         ret2 = ext4_journal_stop(handle);
1749         if (!ret)
1750                 ret = ret2;
1751
1752         if (pos + len > inode->i_size) {
1753                 ext4_truncate(inode);
1754                 /*
1755                  * If truncate failed early the inode might still be
1756                  * on the orphan list; we need to make sure the inode
1757                  * is removed from the orphan list in that case.
1758                  */
1759                 if (inode->i_nlink)
1760                         ext4_orphan_del(NULL, inode);
1761         }
1762
1763         return ret ? ret : copied;
1764 }
1765
1766 static int ext4_journalled_write_end(struct file *file,
1767                                      struct address_space *mapping,
1768                                      loff_t pos, unsigned len, unsigned copied,
1769                                      struct page *page, void *fsdata)
1770 {
1771         handle_t *handle = ext4_journal_current_handle();
1772         struct inode *inode = mapping->host;
1773         int ret = 0, ret2;
1774         int partial = 0;
1775         unsigned from, to;
1776         loff_t new_i_size;
1777
1778         trace_ext4_journalled_write_end(inode, pos, len, copied);
1779         from = pos & (PAGE_CACHE_SIZE - 1);
1780         to = from + len;
1781
1782         if (copied < len) {
1783                 if (!PageUptodate(page))
1784                         copied = 0;
1785                 page_zero_new_buffers(page, from+copied, to);
1786         }
1787
1788         ret = walk_page_buffers(handle, page_buffers(page), from,
1789                                 to, &partial, write_end_fn);
1790         if (!partial)
1791                 SetPageUptodate(page);
1792         new_i_size = pos + copied;
1793         if (new_i_size > inode->i_size)
1794                 i_size_write(inode, pos+copied);
1795         EXT4_I(inode)->i_state |= EXT4_STATE_JDATA;
1796         if (new_i_size > EXT4_I(inode)->i_disksize) {
1797                 ext4_update_i_disksize(inode, new_i_size);
1798                 ret2 = ext4_mark_inode_dirty(handle, inode);
1799                 if (!ret)
1800                         ret = ret2;
1801         }
1802
1803         unlock_page(page);
1804         page_cache_release(page);
1805         if (pos + len > inode->i_size && ext4_can_truncate(inode))
1806                 /* if we have allocated more blocks and copied
1807                  * less. We will have blocks allocated outside
1808                  * inode->i_size. So truncate them
1809                  */
1810                 ext4_orphan_add(handle, inode);
1811
1812         ret2 = ext4_journal_stop(handle);
1813         if (!ret)
1814                 ret = ret2;
1815         if (pos + len > inode->i_size) {
1816                 ext4_truncate(inode);
1817                 /*
1818                  * If truncate failed early the inode might still be
1819                  * on the orphan list; we need to make sure the inode
1820                  * is removed from the orphan list in that case.
1821                  */
1822                 if (inode->i_nlink)
1823                         ext4_orphan_del(NULL, inode);
1824         }
1825
1826         return ret ? ret : copied;
1827 }
1828
1829 static int ext4_da_reserve_space(struct inode *inode, int nrblocks)
1830 {
1831         int retries = 0;
1832         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
1833         unsigned long md_needed, mdblocks, total = 0;
1834
1835         /*
1836          * recalculate the amount of metadata blocks to reserve
1837          * in order to allocate nrblocks
1838          * worse case is one extent per block
1839          */
1840 repeat:
1841         spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
1842         total = EXT4_I(inode)->i_reserved_data_blocks + nrblocks;
1843         mdblocks = ext4_calc_metadata_amount(inode, total);
1844         BUG_ON(mdblocks < EXT4_I(inode)->i_reserved_meta_blocks);
1845
1846         md_needed = mdblocks - EXT4_I(inode)->i_reserved_meta_blocks;
1847         total = md_needed + nrblocks;
1848
1849         /*
1850          * Make quota reservation here to prevent quota overflow
1851          * later. Real quota accounting is done at pages writeout
1852          * time.
1853          */
1854         if (vfs_dq_reserve_block(inode, total)) {
1855                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1856                 return -EDQUOT;
1857         }
1858
1859         if (ext4_claim_free_blocks(sbi, total)) {
1860                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1861                 vfs_dq_release_reservation_block(inode, total);
1862                 if (ext4_should_retry_alloc(inode->i_sb, &retries)) {
1863                         yield();
1864                         goto repeat;
1865                 }
1866                 return -ENOSPC;
1867         }
1868         EXT4_I(inode)->i_reserved_data_blocks += nrblocks;
1869         EXT4_I(inode)->i_reserved_meta_blocks = mdblocks;
1870
1871         spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1872         return 0;       /* success */
1873 }
1874
1875 static void ext4_da_release_space(struct inode *inode, int to_free)
1876 {
1877         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
1878         int total, mdb, mdb_free, release;
1879
1880         if (!to_free)
1881                 return;         /* Nothing to release, exit */
1882
1883         spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
1884
1885         if (!EXT4_I(inode)->i_reserved_data_blocks) {
1886                 /*
1887                  * if there is no reserved blocks, but we try to free some
1888                  * then the counter is messed up somewhere.
1889                  * but since this function is called from invalidate
1890                  * page, it's harmless to return without any action
1891                  */
1892                 printk(KERN_INFO "ext4 delalloc try to release %d reserved "
1893                             "blocks for inode %lu, but there is no reserved "
1894                             "data blocks\n", to_free, inode->i_ino);
1895                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1896                 return;
1897         }
1898
1899         /* recalculate the number of metablocks still need to be reserved */
1900         total = EXT4_I(inode)->i_reserved_data_blocks - to_free;
1901         mdb = ext4_calc_metadata_amount(inode, total);
1902
1903         /* figure out how many metablocks to release */
1904         BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
1905         mdb_free = EXT4_I(inode)->i_reserved_meta_blocks - mdb;
1906
1907         release = to_free + mdb_free;
1908
1909         /* update fs dirty blocks counter for truncate case */
1910         percpu_counter_sub(&sbi->s_dirtyblocks_counter, release);
1911
1912         /* update per-inode reservations */
1913         BUG_ON(to_free > EXT4_I(inode)->i_reserved_data_blocks);
1914         EXT4_I(inode)->i_reserved_data_blocks -= to_free;
1915
1916         BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
1917         EXT4_I(inode)->i_reserved_meta_blocks = mdb;
1918         spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
1919
1920         vfs_dq_release_reservation_block(inode, release);
1921 }
1922
1923 static void ext4_da_page_release_reservation(struct page *page,
1924                                              unsigned long offset)
1925 {
1926         int to_release = 0;
1927         struct buffer_head *head, *bh;
1928         unsigned int curr_off = 0;
1929
1930         head = page_buffers(page);
1931         bh = head;
1932         do {
1933                 unsigned int next_off = curr_off + bh->b_size;
1934
1935                 if ((offset <= curr_off) && (buffer_delay(bh))) {
1936                         to_release++;
1937                         clear_buffer_delay(bh);
1938                 }
1939                 curr_off = next_off;
1940         } while ((bh = bh->b_this_page) != head);
1941         ext4_da_release_space(page->mapping->host, to_release);
1942 }
1943
1944 /*
1945  * Delayed allocation stuff
1946  */
1947
1948 /*
1949  * mpage_da_submit_io - walks through extent of pages and try to write
1950  * them with writepage() call back
1951  *
1952  * @mpd->inode: inode
1953  * @mpd->first_page: first page of the extent
1954  * @mpd->next_page: page after the last page of the extent
1955  *
1956  * By the time mpage_da_submit_io() is called we expect all blocks
1957  * to be allocated. this may be wrong if allocation failed.
1958  *
1959  * As pages are already locked by write_cache_pages(), we can't use it
1960  */
1961 static int mpage_da_submit_io(struct mpage_da_data *mpd)
1962 {
1963         long pages_skipped;
1964         struct pagevec pvec;
1965         unsigned long index, end;
1966         int ret = 0, err, nr_pages, i;
1967         struct inode *inode = mpd->inode;
1968         struct address_space *mapping = inode->i_mapping;
1969
1970         BUG_ON(mpd->next_page <= mpd->first_page);
1971         /*
1972          * We need to start from the first_page to the next_page - 1
1973          * to make sure we also write the mapped dirty buffer_heads.
1974          * If we look at mpd->b_blocknr we would only be looking
1975          * at the currently mapped buffer_heads.
1976          */
1977         index = mpd->first_page;
1978         end = mpd->next_page - 1;
1979
1980         pagevec_init(&pvec, 0);
1981         while (index <= end) {
1982                 nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
1983                 if (nr_pages == 0)
1984                         break;
1985                 for (i = 0; i < nr_pages; i++) {
1986                         struct page *page = pvec.pages[i];
1987
1988                         index = page->index;
1989                         if (index > end)
1990                                 break;
1991                         index++;
1992
1993                         BUG_ON(!PageLocked(page));
1994                         BUG_ON(PageWriteback(page));
1995
1996                         pages_skipped = mpd->wbc->pages_skipped;
1997                         err = mapping->a_ops->writepage(page, mpd->wbc);
1998                         if (!err && (pages_skipped == mpd->wbc->pages_skipped))
1999                                 /*
2000                                  * have successfully written the page
2001                                  * without skipping the same
2002                                  */
2003                                 mpd->pages_written++;
2004                         /*
2005                          * In error case, we have to continue because
2006                          * remaining pages are still locked
2007                          * XXX: unlock and re-dirty them?
2008                          */
2009                         if (ret == 0)
2010                                 ret = err;
2011                 }
2012                 pagevec_release(&pvec);
2013         }
2014         return ret;
2015 }
2016
2017 /*
2018  * mpage_put_bnr_to_bhs - walk blocks and assign them actual numbers
2019  *
2020  * @mpd->inode - inode to walk through
2021  * @exbh->b_blocknr - first block on a disk
2022  * @exbh->b_size - amount of space in bytes
2023  * @logical - first logical block to start assignment with
2024  *
2025  * the function goes through all passed space and put actual disk
2026  * block numbers into buffer heads, dropping BH_Delay and BH_Unwritten
2027  */
2028 static void mpage_put_bnr_to_bhs(struct mpage_da_data *mpd, sector_t logical,
2029                                  struct buffer_head *exbh)
2030 {
2031         struct inode *inode = mpd->inode;
2032         struct address_space *mapping = inode->i_mapping;
2033         int blocks = exbh->b_size >> inode->i_blkbits;
2034         sector_t pblock = exbh->b_blocknr, cur_logical;
2035         struct buffer_head *head, *bh;
2036         pgoff_t index, end;
2037         struct pagevec pvec;
2038         int nr_pages, i;
2039
2040         index = logical >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
2041         end = (logical + blocks - 1) >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
2042         cur_logical = index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2043
2044         pagevec_init(&pvec, 0);
2045
2046         while (index <= end) {
2047                 /* XXX: optimize tail */
2048                 nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
2049                 if (nr_pages == 0)
2050                         break;
2051                 for (i = 0; i < nr_pages; i++) {
2052                         struct page *page = pvec.pages[i];
2053
2054                         index = page->index;
2055                         if (index > end)
2056                                 break;
2057                         index++;
2058
2059                         BUG_ON(!PageLocked(page));
2060                         BUG_ON(PageWriteback(page));
2061                         BUG_ON(!page_has_buffers(page));
2062
2063                         bh = page_buffers(page);
2064                         head = bh;
2065
2066                         /* skip blocks out of the range */
2067                         do {
2068                                 if (cur_logical >= logical)
2069                                         break;
2070                                 cur_logical++;
2071                         } while ((bh = bh->b_this_page) != head);
2072
2073                         do {
2074                                 if (cur_logical >= logical + blocks)
2075                                         break;
2076
2077                                 if (buffer_delay(bh) ||
2078                                                 buffer_unwritten(bh)) {
2079
2080                                         BUG_ON(bh->b_bdev != inode->i_sb->s_bdev);
2081
2082                                         if (buffer_delay(bh)) {
2083                                                 clear_buffer_delay(bh);
2084                                                 bh->b_blocknr = pblock;
2085                                         } else {
2086                                                 /*
2087                                                  * unwritten already should have
2088                                                  * blocknr assigned. Verify that
2089                                                  */
2090                                                 clear_buffer_unwritten(bh);
2091                                                 BUG_ON(bh->b_blocknr != pblock);
2092                                         }
2093
2094                                 } else if (buffer_mapped(bh))
2095                                         BUG_ON(bh->b_blocknr != pblock);
2096
2097                                 cur_logical++;
2098                                 pblock++;
2099                         } while ((bh = bh->b_this_page) != head);
2100                 }
2101                 pagevec_release(&pvec);
2102         }
2103 }
2104
2105
2106 /*
2107  * __unmap_underlying_blocks - just a helper function to unmap
2108  * set of blocks described by @bh
2109  */
2110 static inline void __unmap_underlying_blocks(struct inode *inode,
2111                                              struct buffer_head *bh)
2112 {
2113         struct block_device *bdev = inode->i_sb->s_bdev;
2114         int blocks, i;
2115
2116         blocks = bh->b_size >> inode->i_blkbits;
2117         for (i = 0; i < blocks; i++)
2118                 unmap_underlying_metadata(bdev, bh->b_blocknr + i);
2119 }
2120
2121 static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd,
2122                                         sector_t logical, long blk_cnt)
2123 {
2124         int nr_pages, i;
2125         pgoff_t index, end;
2126         struct pagevec pvec;
2127         struct inode *inode = mpd->inode;
2128         struct address_space *mapping = inode->i_mapping;
2129
2130         index = logical >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
2131         end   = (logical + blk_cnt - 1) >>
2132                                 (PAGE_CACHE_SHIFT - inode->i_blkbits);
2133         while (index <= end) {
2134                 nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
2135                 if (nr_pages == 0)
2136                         break;
2137                 for (i = 0; i < nr_pages; i++) {
2138                         struct page *page = pvec.pages[i];
2139                         index = page->index;
2140                         if (index > end)
2141                                 break;
2142                         index++;
2143
2144                         BUG_ON(!PageLocked(page));
2145                         BUG_ON(PageWriteback(page));
2146                         block_invalidatepage(page, 0);
2147                         ClearPageUptodate(page);
2148                         unlock_page(page);
2149                 }
2150         }
2151         return;
2152 }
2153
2154 static void ext4_print_free_blocks(struct inode *inode)
2155 {
2156         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
2157         printk(KERN_CRIT "Total free blocks count %lld\n",
2158                ext4_count_free_blocks(inode->i_sb));
2159         printk(KERN_CRIT "Free/Dirty block details\n");
2160         printk(KERN_CRIT "free_blocks=%lld\n",
2161                (long long) percpu_counter_sum(&sbi->s_freeblocks_counter));
2162         printk(KERN_CRIT "dirty_blocks=%lld\n",
2163                (long long) percpu_counter_sum(&sbi->s_dirtyblocks_counter));
2164         printk(KERN_CRIT "Block reservation details\n");
2165         printk(KERN_CRIT "i_reserved_data_blocks=%u\n",
2166                EXT4_I(inode)->i_reserved_data_blocks);
2167         printk(KERN_CRIT "i_reserved_meta_blocks=%u\n",
2168                EXT4_I(inode)->i_reserved_meta_blocks);
2169         return;
2170 }
2171
2172 /*
2173  * mpage_da_map_blocks - go through given space
2174  *
2175  * @mpd - bh describing space
2176  *
2177  * The function skips space we know is already mapped to disk blocks.
2178  *
2179  */
2180 static int mpage_da_map_blocks(struct mpage_da_data *mpd)
2181 {
2182         int err, blks, get_blocks_flags;
2183         struct buffer_head new;
2184         sector_t next = mpd->b_blocknr;
2185         unsigned max_blocks = mpd->b_size >> mpd->inode->i_blkbits;
2186         loff_t disksize = EXT4_I(mpd->inode)->i_disksize;
2187         handle_t *handle = NULL;
2188
2189         /*
2190          * We consider only non-mapped and non-allocated blocks
2191          */
2192         if ((mpd->b_state  & (1 << BH_Mapped)) &&
2193                 !(mpd->b_state & (1 << BH_Delay)) &&
2194                 !(mpd->b_state & (1 << BH_Unwritten)))
2195                 return 0;
2196
2197         /*
2198          * If we didn't accumulate anything to write simply return
2199          */
2200         if (!mpd->b_size)
2201                 return 0;
2202
2203         handle = ext4_journal_current_handle();
2204         BUG_ON(!handle);
2205
2206         /*
2207          * Call ext4_get_blocks() to allocate any delayed allocation
2208          * blocks, or to convert an uninitialized extent to be
2209          * initialized (in the case where we have written into
2210          * one or more preallocated blocks).
2211          *
2212          * We pass in the magic EXT4_GET_BLOCKS_DELALLOC_RESERVE to
2213          * indicate that we are on the delayed allocation path.  This
2214          * affects functions in many different parts of the allocation
2215          * call path.  This flag exists primarily because we don't
2216          * want to change *many* call functions, so ext4_get_blocks()
2217          * will set the magic i_delalloc_reserved_flag once the
2218          * inode's allocation semaphore is taken.
2219          *
2220          * If the blocks in questions were delalloc blocks, set
2221          * EXT4_GET_BLOCKS_DELALLOC_RESERVE so the delalloc accounting
2222          * variables are updated after the blocks have been allocated.
2223          */
2224         new.b_state = 0;
2225         get_blocks_flags = (EXT4_GET_BLOCKS_CREATE |
2226                             EXT4_GET_BLOCKS_DELALLOC_RESERVE);
2227         if (mpd->b_state & (1 << BH_Delay))
2228                 get_blocks_flags |= EXT4_GET_BLOCKS_UPDATE_RESERVE_SPACE;
2229         blks = ext4_get_blocks(handle, mpd->inode, next, max_blocks,
2230                                &new, get_blocks_flags);
2231         if (blks < 0) {
2232                 err = blks;
2233                 /*
2234                  * If get block returns with error we simply
2235                  * return. Later writepage will redirty the page and
2236                  * writepages will find the dirty page again
2237                  */
2238                 if (err == -EAGAIN)
2239                         return 0;
2240
2241                 if (err == -ENOSPC &&
2242                     ext4_count_free_blocks(mpd->inode->i_sb)) {
2243                         mpd->retval = err;
2244                         return 0;
2245                 }
2246
2247                 /*
2248                  * get block failure will cause us to loop in
2249                  * writepages, because a_ops->writepage won't be able
2250                  * to make progress. The page will be redirtied by
2251                  * writepage and writepages will again try to write
2252                  * the same.
2253                  */
2254                 ext4_msg(mpd->inode->i_sb, KERN_CRIT,
2255                          "delayed block allocation failed for inode %lu at "
2256                          "logical offset %llu with max blocks %zd with "
2257                          "error %d\n", mpd->inode->i_ino,
2258                          (unsigned long long) next,
2259                          mpd->b_size >> mpd->inode->i_blkbits, err);
2260                 printk(KERN_CRIT "This should not happen!!  "
2261                        "Data will be lost\n");
2262                 if (err == -ENOSPC) {
2263                         ext4_print_free_blocks(mpd->inode);
2264                 }
2265                 /* invalidate all the pages */
2266                 ext4_da_block_invalidatepages(mpd, next,
2267                                 mpd->b_size >> mpd->inode->i_blkbits);
2268                 return err;
2269         }
2270         BUG_ON(blks == 0);
2271
2272         new.b_size = (blks << mpd->inode->i_blkbits);
2273
2274         if (buffer_new(&new))
2275                 __unmap_underlying_blocks(mpd->inode, &new);
2276
2277         /*
2278          * If blocks are delayed marked, we need to
2279          * put actual blocknr and drop delayed bit
2280          */
2281         if ((mpd->b_state & (1 << BH_Delay)) ||
2282             (mpd->b_state & (1 << BH_Unwritten)))
2283                 mpage_put_bnr_to_bhs(mpd, next, &new);
2284
2285         if (ext4_should_order_data(mpd->inode)) {
2286                 err = ext4_jbd2_file_inode(handle, mpd->inode);
2287                 if (err)
2288                         return err;
2289         }
2290
2291         /*
2292          * Update on-disk size along with block allocation.
2293          */
2294         disksize = ((loff_t) next + blks) << mpd->inode->i_blkbits;
2295         if (disksize > i_size_read(mpd->inode))
2296                 disksize = i_size_read(mpd->inode);
2297         if (disksize > EXT4_I(mpd->inode)->i_disksize) {
2298                 ext4_update_i_disksize(mpd->inode, disksize);
2299                 return ext4_mark_inode_dirty(handle, mpd->inode);
2300         }
2301
2302         return 0;
2303 }
2304
2305 #define BH_FLAGS ((1 << BH_Uptodate) | (1 << BH_Mapped) | \
2306                 (1 << BH_Delay) | (1 << BH_Unwritten))
2307
2308 /*
2309  * mpage_add_bh_to_extent - try to add one more block to extent of blocks
2310  *
2311  * @mpd->lbh - extent of blocks
2312  * @logical - logical number of the block in the file
2313  * @bh - bh of the block (used to access block's state)
2314  *
2315  * the function is used to collect contig. blocks in same state
2316  */
2317 static void mpage_add_bh_to_extent(struct mpage_da_data *mpd,
2318                                    sector_t logical, size_t b_size,
2319                                    unsigned long b_state)
2320 {
2321         sector_t next;
2322         int nrblocks = mpd->b_size >> mpd->inode->i_blkbits;
2323
2324         /* check if thereserved journal credits might overflow */
2325         if (!(EXT4_I(mpd->inode)->i_flags & EXT4_EXTENTS_FL)) {
2326                 if (nrblocks >= EXT4_MAX_TRANS_DATA) {
2327                         /*
2328                          * With non-extent format we are limited by the journal
2329                          * credit available.  Total credit needed to insert
2330                          * nrblocks contiguous blocks is dependent on the
2331                          * nrblocks.  So limit nrblocks.
2332                          */
2333                         goto flush_it;
2334                 } else if ((nrblocks + (b_size >> mpd->inode->i_blkbits)) >
2335                                 EXT4_MAX_TRANS_DATA) {
2336                         /*
2337                          * Adding the new buffer_head would make it cross the
2338                          * allowed limit for which we have journal credit
2339                          * reserved. So limit the new bh->b_size
2340                          */
2341                         b_size = (EXT4_MAX_TRANS_DATA - nrblocks) <<
2342                                                 mpd->inode->i_blkbits;
2343                         /* we will do mpage_da_submit_io in the next loop */
2344                 }
2345         }
2346         /*
2347          * First block in the extent
2348          */
2349         if (mpd->b_size == 0) {
2350                 mpd->b_blocknr = logical;
2351                 mpd->b_size = b_size;
2352                 mpd->b_state = b_state & BH_FLAGS;
2353                 return;
2354         }
2355
2356         next = mpd->b_blocknr + nrblocks;
2357         /*
2358          * Can we merge the block to our big extent?
2359          */
2360         if (logical == next && (b_state & BH_FLAGS) == mpd->b_state) {
2361                 mpd->b_size += b_size;
2362                 return;
2363         }
2364
2365 flush_it:
2366         /*
2367          * We couldn't merge the block to our extent, so we
2368          * need to flush current  extent and start new one
2369          */
2370         if (mpage_da_map_blocks(mpd) == 0)
2371                 mpage_da_submit_io(mpd);
2372         mpd->io_done = 1;
2373         return;
2374 }
2375
2376 static int ext4_bh_delay_or_unwritten(handle_t *handle, struct buffer_head *bh)
2377 {
2378         return (buffer_delay(bh) || buffer_unwritten(bh)) && buffer_dirty(bh);
2379 }
2380
2381 /*
2382  * __mpage_da_writepage - finds extent of pages and blocks
2383  *
2384  * @page: page to consider
2385  * @wbc: not used, we just follow rules
2386  * @data: context
2387  *
2388  * The function finds extents of pages and scan them for all blocks.
2389  */
2390 static int __mpage_da_writepage(struct page *page,
2391                                 struct writeback_control *wbc, void *data)
2392 {
2393         struct mpage_da_data *mpd = data;
2394         struct inode *inode = mpd->inode;
2395         struct buffer_head *bh, *head;
2396         sector_t logical;
2397
2398         if (mpd->io_done) {
2399                 /*
2400                  * Rest of the page in the page_vec
2401                  * redirty then and skip then. We will
2402                  * try to write them again after
2403                  * starting a new transaction
2404                  */
2405                 redirty_page_for_writepage(wbc, page);
2406                 unlock_page(page);
2407                 return MPAGE_DA_EXTENT_TAIL;
2408         }
2409         /*
2410          * Can we merge this page to current extent?
2411          */
2412         if (mpd->next_page != page->index) {
2413                 /*
2414                  * Nope, we can't. So, we map non-allocated blocks
2415                  * and start IO on them using writepage()
2416                  */
2417                 if (mpd->next_page != mpd->first_page) {
2418                         if (mpage_da_map_blocks(mpd) == 0)
2419                                 mpage_da_submit_io(mpd);
2420                         /*
2421                          * skip rest of the page in the page_vec
2422                          */
2423                         mpd->io_done = 1;
2424                         redirty_page_for_writepage(wbc, page);
2425                         unlock_page(page);
2426                         return MPAGE_DA_EXTENT_TAIL;
2427                 }
2428
2429                 /*
2430                  * Start next extent of pages ...
2431                  */
2432                 mpd->first_page = page->index;
2433
2434                 /*
2435                  * ... and blocks
2436                  */
2437                 mpd->b_size = 0;
2438                 mpd->b_state = 0;
2439                 mpd->b_blocknr = 0;
2440         }
2441
2442         mpd->next_page = page->index + 1;
2443         logical = (sector_t) page->index <<
2444                   (PAGE_CACHE_SHIFT - inode->i_blkbits);
2445
2446         if (!page_has_buffers(page)) {
2447                 mpage_add_bh_to_extent(mpd, logical, PAGE_CACHE_SIZE,
2448                                        (1 << BH_Dirty) | (1 << BH_Uptodate));
2449                 if (mpd->io_done)
2450                         return MPAGE_DA_EXTENT_TAIL;
2451         } else {
2452                 /*
2453                  * Page with regular buffer heads, just add all dirty ones
2454                  */
2455                 head = page_buffers(page);
2456                 bh = head;
2457                 do {
2458                         BUG_ON(buffer_locked(bh));
2459                         /*
2460                          * We need to try to allocate
2461                          * unmapped blocks in the same page.
2462                          * Otherwise we won't make progress
2463                          * with the page in ext4_writepage
2464                          */
2465                         if (ext4_bh_delay_or_unwritten(NULL, bh)) {
2466                                 mpage_add_bh_to_extent(mpd, logical,
2467                                                        bh->b_size,
2468                                                        bh->b_state);
2469                                 if (mpd->io_done)
2470                                         return MPAGE_DA_EXTENT_TAIL;
2471                         } else if (buffer_dirty(bh) && (buffer_mapped(bh))) {
2472                                 /*
2473                                  * mapped dirty buffer. We need to update
2474                                  * the b_state because we look at
2475                                  * b_state in mpage_da_map_blocks. We don't
2476                                  * update b_size because if we find an
2477                                  * unmapped buffer_head later we need to
2478                                  * use the b_state flag of that buffer_head.
2479                                  */
2480                                 if (mpd->b_size == 0)
2481                                         mpd->b_state = bh->b_state & BH_FLAGS;
2482                         }
2483                         logical++;
2484                 } while ((bh = bh->b_this_page) != head);
2485         }
2486
2487         return 0;
2488 }
2489
2490 /*
2491  * This is a special get_blocks_t callback which is used by
2492  * ext4_da_write_begin().  It will either return mapped block or
2493  * reserve space for a single block.
2494  *
2495  * For delayed buffer_head we have BH_Mapped, BH_New, BH_Delay set.
2496  * We also have b_blocknr = -1 and b_bdev initialized properly
2497  *
2498  * For unwritten buffer_head we have BH_Mapped, BH_New, BH_Unwritten set.
2499  * We also have b_blocknr = physicalblock mapping unwritten extent and b_bdev
2500  * initialized properly.
2501  */
2502 static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
2503                                   struct buffer_head *bh_result, int create)
2504 {
2505         int ret = 0;
2506         sector_t invalid_block = ~((sector_t) 0xffff);
2507
2508         if (invalid_block < ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es))
2509                 invalid_block = ~0;
2510
2511         BUG_ON(create == 0);
2512         BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
2513
2514         /*
2515          * first, we need to know whether the block is allocated already
2516          * preallocated blocks are unmapped but should treated
2517          * the same as allocated blocks.
2518          */
2519         ret = ext4_get_blocks(NULL, inode, iblock, 1,  bh_result, 0);
2520         if ((ret == 0) && !buffer_delay(bh_result)) {
2521                 /* the block isn't (pre)allocated yet, let's reserve space */
2522                 /*
2523                  * XXX: __block_prepare_write() unmaps passed block,
2524                  * is it OK?
2525                  */
2526                 ret = ext4_da_reserve_space(inode, 1);
2527                 if (ret)
2528                         /* not enough space to reserve */
2529                         return ret;
2530
2531                 map_bh(bh_result, inode->i_sb, invalid_block);
2532                 set_buffer_new(bh_result);
2533                 set_buffer_delay(bh_result);
2534         } else if (ret > 0) {
2535                 bh_result->b_size = (ret << inode->i_blkbits);
2536                 if (buffer_unwritten(bh_result)) {
2537                         /* A delayed write to unwritten bh should
2538                          * be marked new and mapped.  Mapped ensures
2539                          * that we don't do get_block multiple times
2540                          * when we write to the same offset and new
2541                          * ensures that we do proper zero out for
2542                          * partial write.
2543                          */
2544                         set_buffer_new(bh_result);
2545                         set_buffer_mapped(bh_result);
2546                 }
2547                 ret = 0;
2548         }
2549
2550         return ret;
2551 }
2552
2553 /*
2554  * This function is used as a standard get_block_t calback function
2555  * when there is no desire to allocate any blocks.  It is used as a
2556  * callback function for block_prepare_write(), nobh_writepage(), and
2557  * block_write_full_page().  These functions should only try to map a
2558  * single block at a time.
2559  *
2560  * Since this function doesn't do block allocations even if the caller
2561  * requests it by passing in create=1, it is critically important that
2562  * any caller checks to make sure that any buffer heads are returned
2563  * by this function are either all already mapped or marked for
2564  * delayed allocation before calling nobh_writepage() or
2565  * block_write_full_page().  Otherwise, b_blocknr could be left
2566  * unitialized, and the page write functions will be taken by
2567  * surprise.
2568  */
2569 static int noalloc_get_block_write(struct inode *inode, sector_t iblock,
2570                                    struct buffer_head *bh_result, int create)
2571 {
2572         int ret = 0;
2573         unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
2574
2575         BUG_ON(bh_result->b_size != inode->i_sb->s_blocksize);
2576
2577         /*
2578          * we don't want to do block allocation in writepage
2579          * so call get_block_wrap with create = 0
2580          */
2581         ret = ext4_get_blocks(NULL, inode, iblock, max_blocks, bh_result, 0);
2582         if (ret > 0) {
2583                 bh_result->b_size = (ret << inode->i_blkbits);
2584                 ret = 0;
2585         }
2586         return ret;
2587 }
2588
2589 static int bget_one(handle_t *handle, struct buffer_head *bh)
2590 {
2591         get_bh(bh);
2592         return 0;
2593 }
2594
2595 static int bput_one(handle_t *handle, struct buffer_head *bh)
2596 {
2597         put_bh(bh);
2598         return 0;
2599 }
2600
2601 static int __ext4_journalled_writepage(struct page *page,
2602                                        struct writeback_control *wbc,
2603                                        unsigned int len)
2604 {
2605         struct address_space *mapping = page->mapping;
2606         struct inode *inode = mapping->host;
2607         struct buffer_head *page_bufs;
2608         handle_t *handle = NULL;
2609         int ret = 0;
2610         int err;
2611
2612         page_bufs = page_buffers(page);
2613         BUG_ON(!page_bufs);
2614         walk_page_buffers(handle, page_bufs, 0, len, NULL, bget_one);
2615         /* As soon as we unlock the page, it can go away, but we have
2616          * references to buffers so we are safe */
2617         unlock_page(page);
2618
2619         handle = ext4_journal_start(inode, ext4_writepage_trans_blocks(inode));
2620         if (IS_ERR(handle)) {
2621                 ret = PTR_ERR(handle);
2622                 goto out;
2623         }
2624
2625         ret = walk_page_buffers(handle, page_bufs, 0, len, NULL,
2626                                 do_journal_get_write_access);
2627
2628         err = walk_page_buffers(handle, page_bufs, 0, len, NULL,
2629                                 write_end_fn);
2630         if (ret == 0)
2631                 ret = err;
2632         err = ext4_journal_stop(handle);
2633         if (!ret)
2634                 ret = err;
2635
2636         walk_page_buffers(handle, page_bufs, 0, len, NULL, bput_one);
2637         EXT4_I(inode)->i_state |= EXT4_STATE_JDATA;
2638 out:
2639         return ret;
2640 }
2641
2642 /*
2643  * Note that we don't need to start a transaction unless we're journaling data
2644  * because we should have holes filled from ext4_page_mkwrite(). We even don't
2645  * need to file the inode to the transaction's list in ordered mode because if
2646  * we are writing back data added by write(), the inode is already there and if
2647  * we are writing back data modified via mmap(), noone guarantees in which
2648  * transaction the data will hit the disk. In case we are journaling data, we
2649  * cannot start transaction directly because transaction start ranks above page
2650  * lock so we have to do some magic.
2651  *
2652  * This function can get called via...
2653  *   - ext4_da_writepages after taking page lock (have journal handle)
2654  *   - journal_submit_inode_data_buffers (no journal handle)
2655  *   - shrink_page_list via pdflush (no journal handle)
2656  *   - grab_page_cache when doing write_begin (have journal handle)
2657  *
2658  * We don't do any block allocation in this function. If we have page with
2659  * multiple blocks we need to write those buffer_heads that are mapped. This
2660  * is important for mmaped based write. So if we do with blocksize 1K
2661  * truncate(f, 1024);
2662  * a = mmap(f, 0, 4096);
2663  * a[0] = 'a';
2664  * truncate(f, 4096);
2665  * we have in the page first buffer_head mapped via page_mkwrite call back
2666  * but other bufer_heads would be unmapped but dirty(dirty done via the
2667  * do_wp_page). So writepage should write the first block. If we modify
2668  * the mmap area beyond 1024 we will again get a page_fault and the
2669  * page_mkwrite callback will do the block allocation and mark the
2670  * buffer_heads mapped.
2671  *
2672  * We redirty the page if we have any buffer_heads that is either delay or
2673  * unwritten in the page.
2674  *
2675  * We can get recursively called as show below.
2676  *
2677  *      ext4_writepage() -> kmalloc() -> __alloc_pages() -> page_launder() ->
2678  *              ext4_writepage()
2679  *
2680  * But since we don't do any block allocation we should not deadlock.
2681  * Page also have the dirty flag cleared so we don't get recurive page_lock.
2682  */
2683 static int ext4_writepage(struct page *page,
2684                           struct writeback_control *wbc)
2685 {
2686         int ret = 0;
2687         loff_t size;
2688         unsigned int len;
2689         struct buffer_head *page_bufs;
2690         struct inode *inode = page->mapping->host;
2691
2692         trace_ext4_writepage(inode, page);
2693         size = i_size_read(inode);
2694         if (page->index == size >> PAGE_CACHE_SHIFT)
2695                 len = size & ~PAGE_CACHE_MASK;
2696         else
2697                 len = PAGE_CACHE_SIZE;
2698
2699         if (page_has_buffers(page)) {
2700                 page_bufs = page_buffers(page);
2701                 if (walk_page_buffers(NULL, page_bufs, 0, len, NULL,
2702                                         ext4_bh_delay_or_unwritten)) {
2703                         /*
2704                          * We don't want to do  block allocation
2705                          * So redirty the page and return
2706                          * We may reach here when we do a journal commit
2707                          * via journal_submit_inode_data_buffers.
2708                          * If we don't have mapping block we just ignore
2709                          * them. We can also reach here via shrink_page_list
2710                          */
2711                         redirty_page_for_writepage(wbc, page);
2712                         unlock_page(page);
2713                         return 0;
2714                 }
2715         } else {
2716                 /*
2717                  * The test for page_has_buffers() is subtle:
2718                  * We know the page is dirty but it lost buffers. That means
2719                  * that at some moment in time after write_begin()/write_end()
2720                  * has been called all buffers have been clean and thus they
2721                  * must have been written at least once. So they are all
2722                  * mapped and we can happily proceed with mapping them
2723                  * and writing the page.
2724                  *
2725                  * Try to initialize the buffer_heads and check whether
2726                  * all are mapped and non delay. We don't want to
2727                  * do block allocation here.
2728                  */
2729                 ret = block_prepare_write(page, 0, len,
2730                                           noalloc_get_block_write);
2731                 if (!ret) {
2732                         page_bufs = page_buffers(page);
2733                         /* check whether all are mapped and non delay */
2734                         if (walk_page_buffers(NULL, page_bufs, 0, len, NULL,
2735                                                 ext4_bh_delay_or_unwritten)) {
2736                                 redirty_page_for_writepage(wbc, page);
2737                                 unlock_page(page);
2738                                 return 0;
2739                         }
2740                 } else {
2741                         /*
2742                          * We can't do block allocation here
2743                          * so just redity the page and unlock
2744                          * and return
2745                          */
2746                         redirty_page_for_writepage(wbc, page);
2747                         unlock_page(page);
2748                         return 0;
2749                 }
2750                 /* now mark the buffer_heads as dirty and uptodate */
2751                 block_commit_write(page, 0, len);
2752         }
2753
2754         if (PageChecked(page) && ext4_should_journal_data(inode)) {
2755                 /*
2756                  * It's mmapped pagecache.  Add buffers and journal it.  There
2757                  * doesn't seem much point in redirtying the page here.
2758                  */
2759                 ClearPageChecked(page);
2760                 return __ext4_journalled_writepage(page, wbc, len);
2761         }
2762
2763         if (test_opt(inode->i_sb, NOBH) && ext4_should_writeback_data(inode))
2764                 ret = nobh_writepage(page, noalloc_get_block_write, wbc);
2765         else
2766                 ret = block_write_full_page(page, noalloc_get_block_write,
2767                                             wbc);
2768
2769         return ret;
2770 }
2771
2772 /*
2773  * This is called via ext4_da_writepages() to
2774  * calulate the total number of credits to reserve to fit
2775  * a single extent allocation into a single transaction,
2776  * ext4_da_writpeages() will loop calling this before
2777  * the block allocation.
2778  */
2779
2780 static int ext4_da_writepages_trans_blocks(struct inode *inode)
2781 {
2782         int max_blocks = EXT4_I(inode)->i_reserved_data_blocks;
2783
2784         /*
2785          * With non-extent format the journal credit needed to
2786          * insert nrblocks contiguous block is dependent on
2787          * number of contiguous block. So we will limit
2788          * number of contiguous block to a sane value
2789          */
2790         if (!(inode->i_flags & EXT4_EXTENTS_FL) &&
2791             (max_blocks > EXT4_MAX_TRANS_DATA))
2792                 max_blocks = EXT4_MAX_TRANS_DATA;
2793
2794         return ext4_chunk_trans_blocks(inode, max_blocks);
2795 }
2796
2797 static int ext4_da_writepages(struct address_space *mapping,
2798                               struct writeback_control *wbc)
2799 {
2800         pgoff_t index;
2801         int range_whole = 0;
2802         handle_t *handle = NULL;
2803         struct mpage_da_data mpd;
2804         struct inode *inode = mapping->host;
2805         int no_nrwrite_index_update;
2806         int pages_written = 0;
2807         long pages_skipped;
2808         unsigned int max_pages;
2809         int range_cyclic, cycled = 1, io_done = 0;
2810         int needed_blocks, ret = 0;
2811         long desired_nr_to_write, nr_to_writebump = 0;
2812         loff_t range_start = wbc->range_start;
2813         struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);
2814
2815         trace_ext4_da_writepages(inode, wbc);
2816
2817         /*
2818          * No pages to write? This is mainly a kludge to avoid starting
2819          * a transaction for special inodes like journal inode on last iput()
2820          * because that could violate lock ordering on umount
2821          */
2822         if (!mapping->nrpages || !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
2823                 return 0;
2824
2825         /*
2826          * If the filesystem has aborted, it is read-only, so return
2827          * right away instead of dumping stack traces later on that
2828          * will obscure the real source of the problem.  We test
2829          * EXT4_MF_FS_ABORTED instead of sb->s_flag's MS_RDONLY because
2830          * the latter could be true if the filesystem is mounted
2831          * read-only, and in that case, ext4_da_writepages should
2832          * *never* be called, so if that ever happens, we would want
2833          * the stack trace.
2834          */
2835         if (unlikely(sbi->s_mount_flags & EXT4_MF_FS_ABORTED))
2836                 return -EROFS;
2837
2838         if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
2839                 range_whole = 1;
2840
2841         range_cyclic = wbc->range_cyclic;
2842         if (wbc->range_cyclic) {
2843                 index = mapping->writeback_index;
2844                 if (index)
2845                         cycled = 0;
2846                 wbc->range_start = index << PAGE_CACHE_SHIFT;
2847                 wbc->range_end  = LLONG_MAX;
2848                 wbc->range_cyclic = 0;
2849         } else
2850                 index = wbc->range_start >> PAGE_CACHE_SHIFT;
2851
2852         /*
2853          * This works around two forms of stupidity.  The first is in
2854          * the writeback code, which caps the maximum number of pages
2855          * written to be 1024 pages.  This is wrong on multiple
2856          * levels; different architectues have a different page size,
2857          * which changes the maximum amount of data which gets
2858          * written.  Secondly, 4 megabytes is way too small.  XFS
2859          * forces this value to be 16 megabytes by multiplying
2860          * nr_to_write parameter by four, and then relies on its
2861          * allocator to allocate larger extents to make them
2862          * contiguous.  Unfortunately this brings us to the second
2863          * stupidity, which is that ext4's mballoc code only allocates
2864          * at most 2048 blocks.  So we force contiguous writes up to
2865          * the number of dirty blocks in the inode, or
2866          * sbi->max_writeback_mb_bump whichever is smaller.
2867          */
2868         max_pages = sbi->s_max_writeback_mb_bump << (20 - PAGE_CACHE_SHIFT);
2869         if (!range_cyclic && range_whole)
2870                 desired_nr_to_write = wbc->nr_to_write * 8;
2871         else
2872                 desired_nr_to_write = ext4_num_dirty_pages(inode, index,
2873                                                            max_pages);
2874         if (desired_nr_to_write > max_pages)
2875                 desired_nr_to_write = max_pages;
2876
2877         if (wbc->nr_to_write < desired_nr_to_write) {
2878                 nr_to_writebump = desired_nr_to_write - wbc->nr_to_write;
2879                 wbc->nr_to_write = desired_nr_to_write;
2880         }
2881
2882         mpd.wbc = wbc;
2883         mpd.inode = mapping->host;
2884
2885         /*
2886          * we don't want write_cache_pages to update
2887          * nr_to_write and writeback_index
2888          */
2889         no_nrwrite_index_update = wbc->no_nrwrite_index_update;
2890         wbc->no_nrwrite_index_update = 1;
2891         pages_skipped = wbc->pages_skipped;
2892
2893 retry:
2894         while (!ret && wbc->nr_to_write > 0) {
2895
2896                 /*
2897                  * we  insert one extent at a time. So we need
2898                  * credit needed for single extent allocation.
2899                  * journalled mode is currently not supported
2900                  * by delalloc
2901                  */
2902                 BUG_ON(ext4_should_journal_data(inode));
2903                 needed_blocks = ext4_da_writepages_trans_blocks(inode);
2904
2905                 /* start a new transaction*/
2906                 handle = ext4_journal_start(inode, needed_blocks);
2907                 if (IS_ERR(handle)) {
2908                         ret = PTR_ERR(handle);
2909                         ext4_msg(inode->i_sb, KERN_CRIT, "%s: jbd2_start: "
2910                                "%ld pages, ino %lu; err %d\n", __func__,
2911                                 wbc->nr_to_write, inode->i_ino, ret);
2912                         goto out_writepages;
2913                 }
2914
2915                 /*
2916                  * Now call __mpage_da_writepage to find the next
2917                  * contiguous region of logical blocks that need
2918                  * blocks to be allocated by ext4.  We don't actually
2919                  * submit the blocks for I/O here, even though
2920                  * write_cache_pages thinks it will, and will set the
2921                  * pages as clean for write before calling
2922                  * __mpage_da_writepage().
2923                  */
2924                 mpd.b_size = 0;
2925                 mpd.b_state = 0;
2926                 mpd.b_blocknr = 0;
2927                 mpd.first_page = 0;
2928                 mpd.next_page = 0;
2929                 mpd.io_done = 0;
2930                 mpd.pages_written = 0;
2931                 mpd.retval = 0;
2932                 ret = write_cache_pages(mapping, wbc, __mpage_da_writepage,
2933                                         &mpd);
2934                 /*
2935                  * If we have a contigous extent of pages and we
2936                  * haven't done the I/O yet, map the blocks and submit
2937                  * them for I/O.
2938                  */
2939                 if (!mpd.io_done && mpd.next_page != mpd.first_page) {
2940                         if (mpage_da_map_blocks(&mpd) == 0)
2941                                 mpage_da_submit_io(&mpd);
2942                         mpd.io_done = 1;
2943                         ret = MPAGE_DA_EXTENT_TAIL;
2944                 }
2945                 trace_ext4_da_write_pages(inode, &mpd);
2946                 wbc->nr_to_write -= mpd.pages_written;
2947
2948                 ext4_journal_stop(handle);
2949
2950                 if ((mpd.retval == -ENOSPC) && sbi->s_journal) {
2951                         /* commit the transaction which would
2952                          * free blocks released in the transaction
2953                          * and try again
2954                          */
2955                         jbd2_journal_force_commit_nested(sbi->s_journal);
2956                         wbc->pages_skipped = pages_skipped;
2957                         ret = 0;
2958                 } else if (ret == MPAGE_DA_EXTENT_TAIL) {
2959                         /*
2960                          * got one extent now try with
2961                          * rest of the pages
2962                          */
2963                         pages_written += mpd.pages_written;
2964                         wbc->pages_skipped = pages_skipped;
2965                         ret = 0;
2966                         io_done = 1;
2967                 } else if (wbc->nr_to_write)
2968                         /*
2969                          * There is no more writeout needed
2970                          * or we requested for a noblocking writeout
2971                          * and we found the device congested
2972                          */
2973                         break;
2974         }
2975         if (!io_done && !cycled) {
2976                 cycled = 1;
2977                 index = 0;
2978                 wbc->range_start = index << PAGE_CACHE_SHIFT;
2979                 wbc->range_end  = mapping->writeback_index - 1;
2980                 goto retry;
2981         }
2982         if (pages_skipped != wbc->pages_skipped)
2983                 ext4_msg(inode->i_sb, KERN_CRIT,
2984                          "This should not happen leaving %s "
2985                          "with nr_to_write = %ld ret = %d\n",
2986                          __func__, wbc->nr_to_write, ret);
2987
2988         /* Update index */
2989         index += pages_written;
2990         wbc->range_cyclic = range_cyclic;
2991         if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
2992                 /*
2993                  * set the writeback_index so that range_cyclic
2994                  * mode will write it back later
2995                  */
2996                 mapping->writeback_index = index;
2997
2998 out_writepages:
2999         if (!no_nrwrite_index_update)
3000                 wbc->no_nrwrite_index_update = 0;
3001         if (wbc->nr_to_write > nr_to_writebump)
3002                 wbc->nr_to_write -= nr_to_writebump;
3003         wbc->range_start = range_start;
3004         trace_ext4_da_writepages_result(inode, wbc, ret, pages_written);
3005         return ret;
3006 }
3007
3008 #define FALL_BACK_TO_NONDELALLOC 1
3009 static int ext4_nonda_switch(struct super_block *sb)
3010 {
3011         s64 free_blocks, dirty_blocks;
3012         struct ext4_sb_info *sbi = EXT4_SB(sb);
3013
3014         /*
3015          * switch to non delalloc mode if we are running low
3016          * on free block. The free block accounting via percpu
3017          * counters can get slightly wrong with percpu_counter_batch getting
3018          * accumulated on each CPU without updating global counters
3019          * Delalloc need an accurate free block accounting. So switch
3020          * to non delalloc when we are near to error range.
3021          */
3022         free_blocks  = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
3023         dirty_blocks = percpu_counter_read_positive(&sbi->s_dirtyblocks_counter);
3024         if (2 * free_blocks < 3 * dirty_blocks ||
3025                 free_blocks < (dirty_blocks + EXT4_FREEBLOCKS_WATERMARK)) {
3026                 /*
3027                  * free block count is less that 150% of dirty blocks
3028                  * or free blocks is less that watermark
3029                  */
3030                 return 1;
3031         }
3032         return 0;
3033 }
3034
3035 static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
3036                                loff_t pos, unsigned len, unsigned flags,
3037                                struct page **pagep, void **fsdata)
3038 {
3039         int ret, retries = 0;
3040         struct page *page;
3041         pgoff_t index;
3042         unsigned from, to;
3043         struct inode *inode = mapping->host;
3044         handle_t *handle;
3045
3046         index = pos >> PAGE_CACHE_SHIFT;
3047         from = pos & (PAGE_CACHE_SIZE - 1);
3048         to = from + len;
3049
3050         if (ext4_nonda_switch(inode->i_sb)) {
3051                 *fsdata = (void *)FALL_BACK_TO_NONDELALLOC;
3052                 return ext4_write_begin(file, mapping, pos,
3053                                         len, flags, pagep, fsdata);
3054         }
3055         *fsdata = (void *)0;
3056         trace_ext4_da_write_begin(inode, pos, len, flags);
3057 retry:
3058         /*
3059          * With delayed allocation, we don't log the i_disksize update
3060          * if there is delayed block allocation. But we still need
3061          * to journalling the i_disksize update if writes to the end
3062          * of file which has an already mapped buffer.
3063          */
3064         handle = ext4_journal_start(inode, 1);
3065         if (IS_ERR(handle)) {
3066                 ret = PTR_ERR(handle);
3067                 goto out;
3068         }
3069         /* We cannot recurse into the filesystem as the transaction is already
3070          * started */
3071         flags |= AOP_FLAG_NOFS;
3072
3073         page = grab_cache_page_write_begin(mapping, index, flags);
3074         if (!page) {
3075                 ext4_journal_stop(handle);
3076                 ret = -ENOMEM;
3077                 goto out;
3078         }
3079         *pagep = page;
3080
3081         ret = block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
3082                                 ext4_da_get_block_prep);
3083         if (ret < 0) {
3084                 unlock_page(page);
3085                 ext4_journal_stop(handle);
3086                 page_cache_release(page);
3087                 /*
3088                  * block_write_begin may have instantiated a few blocks
3089                  * outside i_size.  Trim these off again. Don't need
3090                  * i_size_read because we hold i_mutex.
3091                  */
3092                 if (pos + len > inode->i_size)
3093                         ext4_truncate(inode);
3094         }
3095
3096         if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
3097                 goto retry;
3098 out:
3099         return ret;
3100 }
3101
3102 /*
3103  * Check if we should update i_disksize
3104  * when write to the end of file but not require block allocation
3105  */
3106 static int ext4_da_should_update_i_disksize(struct page *page,
3107                                             unsigned long offset)
3108 {
3109         struct buffer_head *bh;
3110         struct inode *inode = page->mapping->host;
3111         unsigned int idx;
3112         int i;
3113
3114         bh = page_buffers(page);
3115         idx = offset >> inode->i_blkbits;
3116
3117         for (i = 0; i < idx; i++)
3118                 bh = bh->b_this_page;
3119
3120         if (!buffer_mapped(bh) || (buffer_delay(bh)) || buffer_unwritten(bh))
3121                 return 0;
3122         return 1;
3123 }
3124
3125 static int ext4_da_write_end(struct file *file,
3126                              struct address_space *mapping,
3127                              loff_t pos, unsigned len, unsigned copied,
3128                              struct page *page, void *fsdata)
3129 {
3130         struct inode *inode = mapping->host;
3131         int ret = 0, ret2;
3132         handle_t *handle = ext4_journal_current_handle();
3133         loff_t new_i_size;
3134         unsigned long start, end;
3135         int write_mode = (int)(unsigned long)fsdata;
3136
3137         if (write_mode == FALL_BACK_TO_NONDELALLOC) {
3138                 if (ext4_should_order_data(inode)) {
3139                         return ext4_ordered_write_end(file, mapping, pos,
3140                                         len, copied, page, fsdata);
3141                 } else if (ext4_should_writeback_data(inode)) {
3142                         return ext4_writeback_write_end(file, mapping, pos,
3143                                         len, copied, page, fsdata);
3144                 } else {
3145                         BUG();
3146                 }
3147         }
3148
3149         trace_ext4_da_write_end(inode, pos, len, copied);
3150         start = pos & (PAGE_CACHE_SIZE - 1);
3151         end = start + copied - 1;
3152
3153         /*
3154          * generic_write_end() will run mark_inode_dirty() if i_size
3155          * changes.  So let's piggyback the i_disksize mark_inode_dirty
3156          * into that.
3157          */
3158
3159         new_i_size = pos + copied;
3160         if (new_i_size > EXT4_I(inode)->i_disksize) {
3161                 if (ext4_da_should_update_i_disksize(page, end)) {
3162                         down_write(&EXT4_I(inode)->i_data_sem);
3163                         if (new_i_size > EXT4_I(inode)->i_disksize) {
3164                                 /*
3165                                  * Updating i_disksize when extending file
3166                                  * without needing block allocation
3167                                  */
3168                                 if (ext4_should_order_data(inode))
3169                                         ret = ext4_jbd2_file_inode(handle,
3170                                                                    inode);
3171
3172                                 EXT4_I(inode)->i_disksize = new_i_size;
3173                         }
3174                         up_write(&EXT4_I(inode)->i_data_sem);
3175                         /* We need to mark inode dirty even if
3176                          * new_i_size is less that inode->i_size
3177                          * bu greater than i_disksize.(hint delalloc)
3178                          */
3179                         ext4_mark_inode_dirty(handle, inode);
3180                 }
3181         }
3182         ret2 = generic_write_end(file, mapping, pos, len, copied,
3183                                                         page, fsdata);
3184         copied = ret2;
3185         if (ret2 < 0)
3186                 ret = ret2;
3187         ret2 = ext4_journal_stop(handle);
3188         if (!ret)
3189                 ret = ret2;
3190
3191         return ret ? ret : copied;
3192 }
3193
3194 static void ext4_da_invalidatepage(struct page *page, unsigned long offset)
3195 {
3196         /*
3197          * Drop reserved blocks
3198          */
3199         BUG_ON(!PageLocked(page));
3200         if (!page_has_buffers(page))
3201                 goto out;
3202
3203         ext4_da_page_release_reservation(page, offset);
3204
3205 out:
3206         ext4_invalidatepage(page, offset);
3207
3208         return;
3209 }
3210
3211 /*
3212  * Force all delayed allocation blocks to be allocated for a given inode.
3213  */
3214 int ext4_alloc_da_blocks(struct inode *inode)
3215 {
3216         trace_ext4_alloc_da_blocks(inode);
3217
3218         if (!EXT4_I(inode)->i_reserved_data_blocks &&
3219             !EXT4_I(inode)->i_reserved_meta_blocks)
3220                 return 0;
3221
3222         /*
3223          * We do something simple for now.  The filemap_flush() will
3224          * also start triggering a write of the data blocks, which is
3225          * not strictly speaking necessary (and for users of
3226          * laptop_mode, not even desirable).  However, to do otherwise
3227          * would require replicating code paths in:
3228          *
3229          * ext4_da_writepages() ->
3230          *    write_cache_pages() ---> (via passed in callback function)
3231          *        __mpage_da_writepage() -->
3232          *           mpage_add_bh_to_extent()
3233          *           mpage_da_map_blocks()
3234          *
3235          * The problem is that write_cache_pages(), located in
3236          * mm/page-writeback.c, marks pages clean in preparation for
3237          * doing I/O, which is not desirable if we're not planning on
3238          * doing I/O at all.
3239          *
3240          * We could call write_cache_pages(), and then redirty all of
3241          * the pages by calling redirty_page_for_writeback() but that
3242          * would be ugly in the extreme.  So instead we would need to
3243          * replicate parts of the code in the above functions,
3244          * simplifying them becuase we wouldn't actually intend to
3245          * write out the pages, but rather only collect contiguous
3246          * logical block extents, call the multi-block allocator, and
3247          * then update the buffer heads with the block allocations.
3248          *
3249          * For now, though, we'll cheat by calling filemap_flush(),
3250          * which will map the blocks, and start the I/O, but not
3251          * actually wait for the I/O to complete.
3252          */
3253         return filemap_flush(inode->i_mapping);
3254 }
3255
3256 /*
3257  * bmap() is special.  It gets used by applications such as lilo and by
3258  * the swapper to find the on-disk block of a specific piece of data.
3259  *
3260  * Naturally, this is dangerous if the block concerned is still in the
3261  * journal.  If somebody makes a swapfile on an ext4 data-journaling