ext4: move ext4_ind_* functions from inode.c to indirect.c
[linux-2.6.git] / fs / ext4 / indirect.c
1 /*
2  *  linux/fs/ext4/indirect.c
3  *
4  *  from
5  *
6  *  linux/fs/ext4/inode.c
7  *
8  * Copyright (C) 1992, 1993, 1994, 1995
9  * Remy Card (card@masi.ibp.fr)
10  * Laboratoire MASI - Institut Blaise Pascal
11  * Universite Pierre et Marie Curie (Paris VI)
12  *
13  *  from
14  *
15  *  linux/fs/minix/inode.c
16  *
17  *  Copyright (C) 1991, 1992  Linus Torvalds
18  *
19  *  Goal-directed block allocation by Stephen Tweedie
20  *      (sct@redhat.com), 1993, 1998
21  */
22
23 #include <linux/module.h>
24 #include "ext4_jbd2.h"
25 #include "truncate.h"
26
27 #include <trace/events/ext4.h>
28
29 typedef struct {
30         __le32  *p;
31         __le32  key;
32         struct buffer_head *bh;
33 } Indirect;
34
35 static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
36 {
37         p->key = *(p->p = v);
38         p->bh = bh;
39 }
40
41 /**
42  *      ext4_block_to_path - parse the block number into array of offsets
43  *      @inode: inode in question (we are only interested in its superblock)
44  *      @i_block: block number to be parsed
45  *      @offsets: array to store the offsets in
46  *      @boundary: set this non-zero if the referred-to block is likely to be
47  *             followed (on disk) by an indirect block.
48  *
49  *      To store the locations of file's data ext4 uses a data structure common
50  *      for UNIX filesystems - tree of pointers anchored in the inode, with
51  *      data blocks at leaves and indirect blocks in intermediate nodes.
52  *      This function translates the block number into path in that tree -
53  *      return value is the path length and @offsets[n] is the offset of
54  *      pointer to (n+1)th node in the nth one. If @block is out of range
55  *      (negative or too large) warning is printed and zero returned.
56  *
57  *      Note: function doesn't find node addresses, so no IO is needed. All
58  *      we need to know is the capacity of indirect blocks (taken from the
59  *      inode->i_sb).
60  */
61
62 /*
63  * Portability note: the last comparison (check that we fit into triple
64  * indirect block) is spelled differently, because otherwise on an
65  * architecture with 32-bit longs and 8Kb pages we might get into trouble
66  * if our filesystem had 8Kb blocks. We might use long long, but that would
67  * kill us on x86. Oh, well, at least the sign propagation does not matter -
68  * i_block would have to be negative in the very beginning, so we would not
69  * get there at all.
70  */
71
72 static int ext4_block_to_path(struct inode *inode,
73                               ext4_lblk_t i_block,
74                               ext4_lblk_t offsets[4], int *boundary)
75 {
76         int ptrs = EXT4_ADDR_PER_BLOCK(inode->i_sb);
77         int ptrs_bits = EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb);
78         const long direct_blocks = EXT4_NDIR_BLOCKS,
79                 indirect_blocks = ptrs,
80                 double_blocks = (1 << (ptrs_bits * 2));
81         int n = 0;
82         int final = 0;
83
84         if (i_block < direct_blocks) {
85                 offsets[n++] = i_block;
86                 final = direct_blocks;
87         } else if ((i_block -= direct_blocks) < indirect_blocks) {
88                 offsets[n++] = EXT4_IND_BLOCK;
89                 offsets[n++] = i_block;
90                 final = ptrs;
91         } else if ((i_block -= indirect_blocks) < double_blocks) {
92                 offsets[n++] = EXT4_DIND_BLOCK;
93                 offsets[n++] = i_block >> ptrs_bits;
94                 offsets[n++] = i_block & (ptrs - 1);
95                 final = ptrs;
96         } else if (((i_block -= double_blocks) >> (ptrs_bits * 2)) < ptrs) {
97                 offsets[n++] = EXT4_TIND_BLOCK;
98                 offsets[n++] = i_block >> (ptrs_bits * 2);
99                 offsets[n++] = (i_block >> ptrs_bits) & (ptrs - 1);
100                 offsets[n++] = i_block & (ptrs - 1);
101                 final = ptrs;
102         } else {
103                 ext4_warning(inode->i_sb, "block %lu > max in inode %lu",
104                              i_block + direct_blocks +
105                              indirect_blocks + double_blocks, inode->i_ino);
106         }
107         if (boundary)
108                 *boundary = final - 1 - (i_block & (ptrs - 1));
109         return n;
110 }
111
112 /**
113  *      ext4_get_branch - read the chain of indirect blocks leading to data
114  *      @inode: inode in question
115  *      @depth: depth of the chain (1 - direct pointer, etc.)
116  *      @offsets: offsets of pointers in inode/indirect blocks
117  *      @chain: place to store the result
118  *      @err: here we store the error value
119  *
120  *      Function fills the array of triples <key, p, bh> and returns %NULL
121  *      if everything went OK or the pointer to the last filled triple
122  *      (incomplete one) otherwise. Upon the return chain[i].key contains
123  *      the number of (i+1)-th block in the chain (as it is stored in memory,
124  *      i.e. little-endian 32-bit), chain[i].p contains the address of that
125  *      number (it points into struct inode for i==0 and into the bh->b_data
126  *      for i>0) and chain[i].bh points to the buffer_head of i-th indirect
127  *      block for i>0 and NULL for i==0. In other words, it holds the block
128  *      numbers of the chain, addresses they were taken from (and where we can
129  *      verify that chain did not change) and buffer_heads hosting these
130  *      numbers.
131  *
132  *      Function stops when it stumbles upon zero pointer (absent block)
133  *              (pointer to last triple returned, *@err == 0)
134  *      or when it gets an IO error reading an indirect block
135  *              (ditto, *@err == -EIO)
136  *      or when it reads all @depth-1 indirect blocks successfully and finds
137  *      the whole chain, all way to the data (returns %NULL, *err == 0).
138  *
139  *      Need to be called with
140  *      down_read(&EXT4_I(inode)->i_data_sem)
141  */
142 static Indirect *ext4_get_branch(struct inode *inode, int depth,
143                                  ext4_lblk_t  *offsets,
144                                  Indirect chain[4], int *err)
145 {
146         struct super_block *sb = inode->i_sb;
147         Indirect *p = chain;
148         struct buffer_head *bh;
149
150         *err = 0;
151         /* i_data is not going away, no lock needed */
152         add_chain(chain, NULL, EXT4_I(inode)->i_data + *offsets);
153         if (!p->key)
154                 goto no_block;
155         while (--depth) {
156                 bh = sb_getblk(sb, le32_to_cpu(p->key));
157                 if (unlikely(!bh))
158                         goto failure;
159
160                 if (!bh_uptodate_or_lock(bh)) {
161                         if (bh_submit_read(bh) < 0) {
162                                 put_bh(bh);
163                                 goto failure;
164                         }
165                         /* validate block references */
166                         if (ext4_check_indirect_blockref(inode, bh)) {
167                                 put_bh(bh);
168                                 goto failure;
169                         }
170                 }
171
172                 add_chain(++p, bh, (__le32 *)bh->b_data + *++offsets);
173                 /* Reader: end */
174                 if (!p->key)
175                         goto no_block;
176         }
177         return NULL;
178
179 failure:
180         *err = -EIO;
181 no_block:
182         return p;
183 }
184
185 /**
186  *      ext4_find_near - find a place for allocation with sufficient locality
187  *      @inode: owner
188  *      @ind: descriptor of indirect block.
189  *
190  *      This function returns the preferred place for block allocation.
191  *      It is used when heuristic for sequential allocation fails.
192  *      Rules are:
193  *        + if there is a block to the left of our position - allocate near it.
194  *        + if pointer will live in indirect block - allocate near that block.
195  *        + if pointer will live in inode - allocate in the same
196  *          cylinder group.
197  *
198  * In the latter case we colour the starting block by the callers PID to
199  * prevent it from clashing with concurrent allocations for a different inode
200  * in the same block group.   The PID is used here so that functionally related
201  * files will be close-by on-disk.
202  *
203  *      Caller must make sure that @ind is valid and will stay that way.
204  */
205 static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
206 {
207         struct ext4_inode_info *ei = EXT4_I(inode);
208         __le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
209         __le32 *p;
210         ext4_fsblk_t bg_start;
211         ext4_fsblk_t last_block;
212         ext4_grpblk_t colour;
213         ext4_group_t block_group;
214         int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
215
216         /* Try to find previous block */
217         for (p = ind->p - 1; p >= start; p--) {
218                 if (*p)
219                         return le32_to_cpu(*p);
220         }
221
222         /* No such thing, so let's try location of indirect block */
223         if (ind->bh)
224                 return ind->bh->b_blocknr;
225
226         /*
227          * It is going to be referred to from the inode itself? OK, just put it
228          * into the same cylinder group then.
229          */
230         block_group = ei->i_block_group;
231         if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
232                 block_group &= ~(flex_size-1);
233                 if (S_ISREG(inode->i_mode))
234                         block_group++;
235         }
236         bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
237         last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
238
239         /*
240          * If we are doing delayed allocation, we don't need take
241          * colour into account.
242          */
243         if (test_opt(inode->i_sb, DELALLOC))
244                 return bg_start;
245
246         if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
247                 colour = (current->pid % 16) *
248                         (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
249         else
250                 colour = (current->pid % 16) * ((last_block - bg_start) / 16);
251         return bg_start + colour;
252 }
253
254 /**
255  *      ext4_find_goal - find a preferred place for allocation.
256  *      @inode: owner
257  *      @block:  block we want
258  *      @partial: pointer to the last triple within a chain
259  *
260  *      Normally this function find the preferred place for block allocation,
261  *      returns it.
262  *      Because this is only used for non-extent files, we limit the block nr
263  *      to 32 bits.
264  */
265 static ext4_fsblk_t ext4_find_goal(struct inode *inode, ext4_lblk_t block,
266                                    Indirect *partial)
267 {
268         ext4_fsblk_t goal;
269
270         /*
271          * XXX need to get goal block from mballoc's data structures
272          */
273
274         goal = ext4_find_near(inode, partial);
275         goal = goal & EXT4_MAX_BLOCK_FILE_PHYS;
276         return goal;
277 }
278
279 /**
280  *      ext4_blks_to_allocate - Look up the block map and count the number
281  *      of direct blocks need to be allocated for the given branch.
282  *
283  *      @branch: chain of indirect blocks
284  *      @k: number of blocks need for indirect blocks
285  *      @blks: number of data blocks to be mapped.
286  *      @blocks_to_boundary:  the offset in the indirect block
287  *
288  *      return the total number of blocks to be allocate, including the
289  *      direct and indirect blocks.
290  */
291 static int ext4_blks_to_allocate(Indirect *branch, int k, unsigned int blks,
292                                  int blocks_to_boundary)
293 {
294         unsigned int count = 0;
295
296         /*
297          * Simple case, [t,d]Indirect block(s) has not allocated yet
298          * then it's clear blocks on that path have not allocated
299          */
300         if (k > 0) {
301                 /* right now we don't handle cross boundary allocation */
302                 if (blks < blocks_to_boundary + 1)
303                         count += blks;
304                 else
305                         count += blocks_to_boundary + 1;
306                 return count;
307         }
308
309         count++;
310         while (count < blks && count <= blocks_to_boundary &&
311                 le32_to_cpu(*(branch[0].p + count)) == 0) {
312                 count++;
313         }
314         return count;
315 }
316
317 /**
318  *      ext4_alloc_blocks: multiple allocate blocks needed for a branch
319  *      @handle: handle for this transaction
320  *      @inode: inode which needs allocated blocks
321  *      @iblock: the logical block to start allocated at
322  *      @goal: preferred physical block of allocation
323  *      @indirect_blks: the number of blocks need to allocate for indirect
324  *                      blocks
325  *      @blks: number of desired blocks
326  *      @new_blocks: on return it will store the new block numbers for
327  *      the indirect blocks(if needed) and the first direct block,
328  *      @err: on return it will store the error code
329  *
330  *      This function will return the number of blocks allocated as
331  *      requested by the passed-in parameters.
332  */
333 static int ext4_alloc_blocks(handle_t *handle, struct inode *inode,
334                              ext4_lblk_t iblock, ext4_fsblk_t goal,
335                              int indirect_blks, int blks,
336                              ext4_fsblk_t new_blocks[4], int *err)
337 {
338         struct ext4_allocation_request ar;
339         int target, i;
340         unsigned long count = 0, blk_allocated = 0;
341         int index = 0;
342         ext4_fsblk_t current_block = 0;
343         int ret = 0;
344
345         /*
346          * Here we try to allocate the requested multiple blocks at once,
347          * on a best-effort basis.
348          * To build a branch, we should allocate blocks for
349          * the indirect blocks(if not allocated yet), and at least
350          * the first direct block of this branch.  That's the
351          * minimum number of blocks need to allocate(required)
352          */
353         /* first we try to allocate the indirect blocks */
354         target = indirect_blks;
355         while (target > 0) {
356                 count = target;
357                 /* allocating blocks for indirect blocks and direct blocks */
358                 current_block = ext4_new_meta_blocks(handle, inode, goal,
359                                                      0, &count, err);
360                 if (*err)
361                         goto failed_out;
362
363                 if (unlikely(current_block + count > EXT4_MAX_BLOCK_FILE_PHYS)) {
364                         EXT4_ERROR_INODE(inode,
365                                          "current_block %llu + count %lu > %d!",
366                                          current_block, count,
367                                          EXT4_MAX_BLOCK_FILE_PHYS);
368                         *err = -EIO;
369                         goto failed_out;
370                 }
371
372                 target -= count;
373                 /* allocate blocks for indirect blocks */
374                 while (index < indirect_blks && count) {
375                         new_blocks[index++] = current_block++;
376                         count--;
377                 }
378                 if (count > 0) {
379                         /*
380                          * save the new block number
381                          * for the first direct block
382                          */
383                         new_blocks[index] = current_block;
384                         printk(KERN_INFO "%s returned more blocks than "
385                                                 "requested\n", __func__);
386                         WARN_ON(1);
387                         break;
388                 }
389         }
390
391         target = blks - count ;
392         blk_allocated = count;
393         if (!target)
394                 goto allocated;
395         /* Now allocate data blocks */
396         memset(&ar, 0, sizeof(ar));
397         ar.inode = inode;
398         ar.goal = goal;
399         ar.len = target;
400         ar.logical = iblock;
401         if (S_ISREG(inode->i_mode))
402                 /* enable in-core preallocation only for regular files */
403                 ar.flags = EXT4_MB_HINT_DATA;
404
405         current_block = ext4_mb_new_blocks(handle, &ar, err);
406         if (unlikely(current_block + ar.len > EXT4_MAX_BLOCK_FILE_PHYS)) {
407                 EXT4_ERROR_INODE(inode,
408                                  "current_block %llu + ar.len %d > %d!",
409                                  current_block, ar.len,
410                                  EXT4_MAX_BLOCK_FILE_PHYS);
411                 *err = -EIO;
412                 goto failed_out;
413         }
414
415         if (*err && (target == blks)) {
416                 /*
417                  * if the allocation failed and we didn't allocate
418                  * any blocks before
419                  */
420                 goto failed_out;
421         }
422         if (!*err) {
423                 if (target == blks) {
424                         /*
425                          * save the new block number
426                          * for the first direct block
427                          */
428                         new_blocks[index] = current_block;
429                 }
430                 blk_allocated += ar.len;
431         }
432 allocated:
433         /* total number of blocks allocated for direct blocks */
434         ret = blk_allocated;
435         *err = 0;
436         return ret;
437 failed_out:
438         for (i = 0; i < index; i++)
439                 ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1, 0);
440         return ret;
441 }
442
443 /**
444  *      ext4_alloc_branch - allocate and set up a chain of blocks.
445  *      @handle: handle for this transaction
446  *      @inode: owner
447  *      @indirect_blks: number of allocated indirect blocks
448  *      @blks: number of allocated direct blocks
449  *      @goal: preferred place for allocation
450  *      @offsets: offsets (in the blocks) to store the pointers to next.
451  *      @branch: place to store the chain in.
452  *
453  *      This function allocates blocks, zeroes out all but the last one,
454  *      links them into chain and (if we are synchronous) writes them to disk.
455  *      In other words, it prepares a branch that can be spliced onto the
456  *      inode. It stores the information about that chain in the branch[], in
457  *      the same format as ext4_get_branch() would do. We are calling it after
458  *      we had read the existing part of chain and partial points to the last
459  *      triple of that (one with zero ->key). Upon the exit we have the same
460  *      picture as after the successful ext4_get_block(), except that in one
461  *      place chain is disconnected - *branch->p is still zero (we did not
462  *      set the last link), but branch->key contains the number that should
463  *      be placed into *branch->p to fill that gap.
464  *
465  *      If allocation fails we free all blocks we've allocated (and forget
466  *      their buffer_heads) and return the error value the from failed
467  *      ext4_alloc_block() (normally -ENOSPC). Otherwise we set the chain
468  *      as described above and return 0.
469  */
470 static int ext4_alloc_branch(handle_t *handle, struct inode *inode,
471                              ext4_lblk_t iblock, int indirect_blks,
472                              int *blks, ext4_fsblk_t goal,
473                              ext4_lblk_t *offsets, Indirect *branch)
474 {
475         int blocksize = inode->i_sb->s_blocksize;
476         int i, n = 0;
477         int err = 0;
478         struct buffer_head *bh;
479         int num;
480         ext4_fsblk_t new_blocks[4];
481         ext4_fsblk_t current_block;
482
483         num = ext4_alloc_blocks(handle, inode, iblock, goal, indirect_blks,
484                                 *blks, new_blocks, &err);
485         if (err)
486                 return err;
487
488         branch[0].key = cpu_to_le32(new_blocks[0]);
489         /*
490          * metadata blocks and data blocks are allocated.
491          */
492         for (n = 1; n <= indirect_blks;  n++) {
493                 /*
494                  * Get buffer_head for parent block, zero it out
495                  * and set the pointer to new one, then send
496                  * parent to disk.
497                  */
498                 bh = sb_getblk(inode->i_sb, new_blocks[n-1]);
499                 if (unlikely(!bh)) {
500                         err = -EIO;
501                         goto failed;
502                 }
503
504                 branch[n].bh = bh;
505                 lock_buffer(bh);
506                 BUFFER_TRACE(bh, "call get_create_access");
507                 err = ext4_journal_get_create_access(handle, bh);
508                 if (err) {
509                         /* Don't brelse(bh) here; it's done in
510                          * ext4_journal_forget() below */
511                         unlock_buffer(bh);
512                         goto failed;
513                 }
514
515                 memset(bh->b_data, 0, blocksize);
516                 branch[n].p = (__le32 *) bh->b_data + offsets[n];
517                 branch[n].key = cpu_to_le32(new_blocks[n]);
518                 *branch[n].p = branch[n].key;
519                 if (n == indirect_blks) {
520                         current_block = new_blocks[n];
521                         /*
522                          * End of chain, update the last new metablock of
523                          * the chain to point to the new allocated
524                          * data blocks numbers
525                          */
526                         for (i = 1; i < num; i++)
527                                 *(branch[n].p + i) = cpu_to_le32(++current_block);
528                 }
529                 BUFFER_TRACE(bh, "marking uptodate");
530                 set_buffer_uptodate(bh);
531                 unlock_buffer(bh);
532
533                 BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
534                 err = ext4_handle_dirty_metadata(handle, inode, bh);
535                 if (err)
536                         goto failed;
537         }
538         *blks = num;
539         return err;
540 failed:
541         /* Allocation failed, free what we already allocated */
542         ext4_free_blocks(handle, inode, NULL, new_blocks[0], 1, 0);
543         for (i = 1; i <= n ; i++) {
544                 /*
545                  * branch[i].bh is newly allocated, so there is no
546                  * need to revoke the block, which is why we don't
547                  * need to set EXT4_FREE_BLOCKS_METADATA.
548                  */
549                 ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1,
550                                  EXT4_FREE_BLOCKS_FORGET);
551         }
552         for (i = n+1; i < indirect_blks; i++)
553                 ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1, 0);
554
555         ext4_free_blocks(handle, inode, NULL, new_blocks[i], num, 0);
556
557         return err;
558 }
559
560 /**
561  * ext4_splice_branch - splice the allocated branch onto inode.
562  * @handle: handle for this transaction
563  * @inode: owner
564  * @block: (logical) number of block we are adding
565  * @chain: chain of indirect blocks (with a missing link - see
566  *      ext4_alloc_branch)
567  * @where: location of missing link
568  * @num:   number of indirect blocks we are adding
569  * @blks:  number of direct blocks we are adding
570  *
571  * This function fills the missing link and does all housekeeping needed in
572  * inode (->i_blocks, etc.). In case of success we end up with the full
573  * chain to new block and return 0.
574  */
575 static int ext4_splice_branch(handle_t *handle, struct inode *inode,
576                               ext4_lblk_t block, Indirect *where, int num,
577                               int blks)
578 {
579         int i;
580         int err = 0;
581         ext4_fsblk_t current_block;
582
583         /*
584          * If we're splicing into a [td]indirect block (as opposed to the
585          * inode) then we need to get write access to the [td]indirect block
586          * before the splice.
587          */
588         if (where->bh) {
589                 BUFFER_TRACE(where->bh, "get_write_access");
590                 err = ext4_journal_get_write_access(handle, where->bh);
591                 if (err)
592                         goto err_out;
593         }
594         /* That's it */
595
596         *where->p = where->key;
597
598         /*
599          * Update the host buffer_head or inode to point to more just allocated
600          * direct blocks blocks
601          */
602         if (num == 0 && blks > 1) {
603                 current_block = le32_to_cpu(where->key) + 1;
604                 for (i = 1; i < blks; i++)
605                         *(where->p + i) = cpu_to_le32(current_block++);
606         }
607
608         /* We are done with atomic stuff, now do the rest of housekeeping */
609         /* had we spliced it onto indirect block? */
610         if (where->bh) {
611                 /*
612                  * If we spliced it onto an indirect block, we haven't
613                  * altered the inode.  Note however that if it is being spliced
614                  * onto an indirect block at the very end of the file (the
615                  * file is growing) then we *will* alter the inode to reflect
616                  * the new i_size.  But that is not done here - it is done in
617                  * generic_commit_write->__mark_inode_dirty->ext4_dirty_inode.
618                  */
619                 jbd_debug(5, "splicing indirect only\n");
620                 BUFFER_TRACE(where->bh, "call ext4_handle_dirty_metadata");
621                 err = ext4_handle_dirty_metadata(handle, inode, where->bh);
622                 if (err)
623                         goto err_out;
624         } else {
625                 /*
626                  * OK, we spliced it into the inode itself on a direct block.
627                  */
628                 ext4_mark_inode_dirty(handle, inode);
629                 jbd_debug(5, "splicing direct\n");
630         }
631         return err;
632
633 err_out:
634         for (i = 1; i <= num; i++) {
635                 /*
636                  * branch[i].bh is newly allocated, so there is no
637                  * need to revoke the block, which is why we don't
638                  * need to set EXT4_FREE_BLOCKS_METADATA.
639                  */
640                 ext4_free_blocks(handle, inode, where[i].bh, 0, 1,
641                                  EXT4_FREE_BLOCKS_FORGET);
642         }
643         ext4_free_blocks(handle, inode, NULL, le32_to_cpu(where[num].key),
644                          blks, 0);
645
646         return err;
647 }
648
649 /*
650  * The ext4_ind_map_blocks() function handles non-extents inodes
651  * (i.e., using the traditional indirect/double-indirect i_blocks
652  * scheme) for ext4_map_blocks().
653  *
654  * Allocation strategy is simple: if we have to allocate something, we will
655  * have to go the whole way to leaf. So let's do it before attaching anything
656  * to tree, set linkage between the newborn blocks, write them if sync is
657  * required, recheck the path, free and repeat if check fails, otherwise
658  * set the last missing link (that will protect us from any truncate-generated
659  * removals - all blocks on the path are immune now) and possibly force the
660  * write on the parent block.
661  * That has a nice additional property: no special recovery from the failed
662  * allocations is needed - we simply release blocks and do not touch anything
663  * reachable from inode.
664  *
665  * `handle' can be NULL if create == 0.
666  *
667  * return > 0, # of blocks mapped or allocated.
668  * return = 0, if plain lookup failed.
669  * return < 0, error case.
670  *
671  * The ext4_ind_get_blocks() function should be called with
672  * down_write(&EXT4_I(inode)->i_data_sem) if allocating filesystem
673  * blocks (i.e., flags has EXT4_GET_BLOCKS_CREATE set) or
674  * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system
675  * blocks.
676  */
677 int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
678                         struct ext4_map_blocks *map,
679                         int flags)
680 {
681         int err = -EIO;
682         ext4_lblk_t offsets[4];
683         Indirect chain[4];
684         Indirect *partial;
685         ext4_fsblk_t goal;
686         int indirect_blks;
687         int blocks_to_boundary = 0;
688         int depth;
689         int count = 0;
690         ext4_fsblk_t first_block = 0;
691
692         trace_ext4_ind_map_blocks_enter(inode, map->m_lblk, map->m_len, flags);
693         J_ASSERT(!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)));
694         J_ASSERT(handle != NULL || (flags & EXT4_GET_BLOCKS_CREATE) == 0);
695         depth = ext4_block_to_path(inode, map->m_lblk, offsets,
696                                    &blocks_to_boundary);
697
698         if (depth == 0)
699                 goto out;
700
701         partial = ext4_get_branch(inode, depth, offsets, chain, &err);
702
703         /* Simplest case - block found, no allocation needed */
704         if (!partial) {
705                 first_block = le32_to_cpu(chain[depth - 1].key);
706                 count++;
707                 /*map more blocks*/
708                 while (count < map->m_len && count <= blocks_to_boundary) {
709                         ext4_fsblk_t blk;
710
711                         blk = le32_to_cpu(*(chain[depth-1].p + count));
712
713                         if (blk == first_block + count)
714                                 count++;
715                         else
716                                 break;
717                 }
718                 goto got_it;
719         }
720
721         /* Next simple case - plain lookup or failed read of indirect block */
722         if ((flags & EXT4_GET_BLOCKS_CREATE) == 0 || err == -EIO)
723                 goto cleanup;
724
725         /*
726          * Okay, we need to do block allocation.
727         */
728         goal = ext4_find_goal(inode, map->m_lblk, partial);
729
730         /* the number of blocks need to allocate for [d,t]indirect blocks */
731         indirect_blks = (chain + depth) - partial - 1;
732
733         /*
734          * Next look up the indirect map to count the totoal number of
735          * direct blocks to allocate for this branch.
736          */
737         count = ext4_blks_to_allocate(partial, indirect_blks,
738                                       map->m_len, blocks_to_boundary);
739         /*
740          * Block out ext4_truncate while we alter the tree
741          */
742         err = ext4_alloc_branch(handle, inode, map->m_lblk, indirect_blks,
743                                 &count, goal,
744                                 offsets + (partial - chain), partial);
745
746         /*
747          * The ext4_splice_branch call will free and forget any buffers
748          * on the new chain if there is a failure, but that risks using
749          * up transaction credits, especially for bitmaps where the
750          * credits cannot be returned.  Can we handle this somehow?  We
751          * may need to return -EAGAIN upwards in the worst case.  --sct
752          */
753         if (!err)
754                 err = ext4_splice_branch(handle, inode, map->m_lblk,
755                                          partial, indirect_blks, count);
756         if (err)
757                 goto cleanup;
758
759         map->m_flags |= EXT4_MAP_NEW;
760
761         ext4_update_inode_fsync_trans(handle, inode, 1);
762 got_it:
763         map->m_flags |= EXT4_MAP_MAPPED;
764         map->m_pblk = le32_to_cpu(chain[depth-1].key);
765         map->m_len = count;
766         if (count > blocks_to_boundary)
767                 map->m_flags |= EXT4_MAP_BOUNDARY;
768         err = count;
769         /* Clean up and exit */
770         partial = chain + depth - 1;    /* the whole chain */
771 cleanup:
772         while (partial > chain) {
773                 BUFFER_TRACE(partial->bh, "call brelse");
774                 brelse(partial->bh);
775                 partial--;
776         }
777 out:
778         trace_ext4_ind_map_blocks_exit(inode, map->m_lblk,
779                                 map->m_pblk, map->m_len, err);
780         return err;
781 }
782
783 /*
784  * O_DIRECT for ext3 (or indirect map) based files
785  *
786  * If the O_DIRECT write will extend the file then add this inode to the
787  * orphan list.  So recovery will truncate it back to the original size
788  * if the machine crashes during the write.
789  *
790  * If the O_DIRECT write is intantiating holes inside i_size and the machine
791  * crashes then stale disk data _may_ be exposed inside the file. But current
792  * VFS code falls back into buffered path in that case so we are safe.
793  */
794 ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb,
795                            const struct iovec *iov, loff_t offset,
796                            unsigned long nr_segs)
797 {
798         struct file *file = iocb->ki_filp;
799         struct inode *inode = file->f_mapping->host;
800         struct ext4_inode_info *ei = EXT4_I(inode);
801         handle_t *handle;
802         ssize_t ret;
803         int orphan = 0;
804         size_t count = iov_length(iov, nr_segs);
805         int retries = 0;
806
807         if (rw == WRITE) {
808                 loff_t final_size = offset + count;
809
810                 if (final_size > inode->i_size) {
811                         /* Credits for sb + inode write */
812                         handle = ext4_journal_start(inode, 2);
813                         if (IS_ERR(handle)) {
814                                 ret = PTR_ERR(handle);
815                                 goto out;
816                         }
817                         ret = ext4_orphan_add(handle, inode);
818                         if (ret) {
819                                 ext4_journal_stop(handle);
820                                 goto out;
821                         }
822                         orphan = 1;
823                         ei->i_disksize = inode->i_size;
824                         ext4_journal_stop(handle);
825                 }
826         }
827
828 retry:
829         if (rw == READ && ext4_should_dioread_nolock(inode))
830                 ret = __blockdev_direct_IO(rw, iocb, inode,
831                                  inode->i_sb->s_bdev, iov,
832                                  offset, nr_segs,
833                                  ext4_get_block, NULL, NULL, 0);
834         else {
835                 ret = blockdev_direct_IO(rw, iocb, inode,
836                                  inode->i_sb->s_bdev, iov,
837                                  offset, nr_segs,
838                                  ext4_get_block, NULL);
839
840                 if (unlikely((rw & WRITE) && ret < 0)) {
841                         loff_t isize = i_size_read(inode);
842                         loff_t end = offset + iov_length(iov, nr_segs);
843
844                         if (end > isize)
845                                 ext4_truncate_failed_write(inode);
846                 }
847         }
848         if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
849                 goto retry;
850
851         if (orphan) {
852                 int err;
853
854                 /* Credits for sb + inode write */
855                 handle = ext4_journal_start(inode, 2);
856                 if (IS_ERR(handle)) {
857                         /* This is really bad luck. We've written the data
858                          * but cannot extend i_size. Bail out and pretend
859                          * the write failed... */
860                         ret = PTR_ERR(handle);
861                         if (inode->i_nlink)
862                                 ext4_orphan_del(NULL, inode);
863
864                         goto out;
865                 }
866                 if (inode->i_nlink)
867                         ext4_orphan_del(handle, inode);
868                 if (ret > 0) {
869                         loff_t end = offset + ret;
870                         if (end > inode->i_size) {
871                                 ei->i_disksize = end;
872                                 i_size_write(inode, end);
873                                 /*
874                                  * We're going to return a positive `ret'
875                                  * here due to non-zero-length I/O, so there's
876                                  * no way of reporting error returns from
877                                  * ext4_mark_inode_dirty() to userspace.  So
878                                  * ignore it.
879                                  */
880                                 ext4_mark_inode_dirty(handle, inode);
881                         }
882                 }
883                 err = ext4_journal_stop(handle);
884                 if (ret == 0)
885                         ret = err;
886         }
887 out:
888         return ret;
889 }
890
891 /*
892  * Calculate the number of metadata blocks need to reserve
893  * to allocate a new block at @lblocks for non extent file based file
894  */
895 int ext4_ind_calc_metadata_amount(struct inode *inode, sector_t lblock)
896 {
897         struct ext4_inode_info *ei = EXT4_I(inode);
898         sector_t dind_mask = ~((sector_t)EXT4_ADDR_PER_BLOCK(inode->i_sb) - 1);
899         int blk_bits;
900
901         if (lblock < EXT4_NDIR_BLOCKS)
902                 return 0;
903
904         lblock -= EXT4_NDIR_BLOCKS;
905
906         if (ei->i_da_metadata_calc_len &&
907             (lblock & dind_mask) == ei->i_da_metadata_calc_last_lblock) {
908                 ei->i_da_metadata_calc_len++;
909                 return 0;
910         }
911         ei->i_da_metadata_calc_last_lblock = lblock & dind_mask;
912         ei->i_da_metadata_calc_len = 1;
913         blk_bits = order_base_2(lblock);
914         return (blk_bits / EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb)) + 1;
915 }
916
917 int ext4_ind_trans_blocks(struct inode *inode, int nrblocks, int chunk)
918 {
919         int indirects;
920
921         /* if nrblocks are contiguous */
922         if (chunk) {
923                 /*
924                  * With N contiguous data blocks, we need at most
925                  * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) + 1 indirect blocks,
926                  * 2 dindirect blocks, and 1 tindirect block
927                  */
928                 return DIV_ROUND_UP(nrblocks,
929                                     EXT4_ADDR_PER_BLOCK(inode->i_sb)) + 4;
930         }
931         /*
932          * if nrblocks are not contiguous, worse case, each block touch
933          * a indirect block, and each indirect block touch a double indirect
934          * block, plus a triple indirect block
935          */
936         indirects = nrblocks * 2 + 1;
937         return indirects;
938 }
939
940 /*
941  * Truncate transactions can be complex and absolutely huge.  So we need to
942  * be able to restart the transaction at a conventient checkpoint to make
943  * sure we don't overflow the journal.
944  *
945  * start_transaction gets us a new handle for a truncate transaction,
946  * and extend_transaction tries to extend the existing one a bit.  If
947  * extend fails, we need to propagate the failure up and restart the
948  * transaction in the top-level truncate loop. --sct
949  */
950 static handle_t *start_transaction(struct inode *inode)
951 {
952         handle_t *result;
953
954         result = ext4_journal_start(inode, ext4_blocks_for_truncate(inode));
955         if (!IS_ERR(result))
956                 return result;
957
958         ext4_std_error(inode->i_sb, PTR_ERR(result));
959         return result;
960 }
961
962 /*
963  * Try to extend this transaction for the purposes of truncation.
964  *
965  * Returns 0 if we managed to create more room.  If we can't create more
966  * room, and the transaction must be restarted we return 1.
967  */
968 static int try_to_extend_transaction(handle_t *handle, struct inode *inode)
969 {
970         if (!ext4_handle_valid(handle))
971                 return 0;
972         if (ext4_handle_has_enough_credits(handle, EXT4_RESERVE_TRANS_BLOCKS+1))
973                 return 0;
974         if (!ext4_journal_extend(handle, ext4_blocks_for_truncate(inode)))
975                 return 0;
976         return 1;
977 }
978
979 /*
980  * Probably it should be a library function... search for first non-zero word
981  * or memcmp with zero_page, whatever is better for particular architecture.
982  * Linus?
983  */
984 static inline int all_zeroes(__le32 *p, __le32 *q)
985 {
986         while (p < q)
987                 if (*p++)
988                         return 0;
989         return 1;
990 }
991
992 /**
993  *      ext4_find_shared - find the indirect blocks for partial truncation.
994  *      @inode:   inode in question
995  *      @depth:   depth of the affected branch
996  *      @offsets: offsets of pointers in that branch (see ext4_block_to_path)
997  *      @chain:   place to store the pointers to partial indirect blocks
998  *      @top:     place to the (detached) top of branch
999  *
1000  *      This is a helper function used by ext4_truncate().
1001  *
1002  *      When we do truncate() we may have to clean the ends of several
1003  *      indirect blocks but leave the blocks themselves alive. Block is
1004  *      partially truncated if some data below the new i_size is referred
1005  *      from it (and it is on the path to the first completely truncated
1006  *      data block, indeed).  We have to free the top of that path along
1007  *      with everything to the right of the path. Since no allocation
1008  *      past the truncation point is possible until ext4_truncate()
1009  *      finishes, we may safely do the latter, but top of branch may
1010  *      require special attention - pageout below the truncation point
1011  *      might try to populate it.
1012  *
1013  *      We atomically detach the top of branch from the tree, store the
1014  *      block number of its root in *@top, pointers to buffer_heads of
1015  *      partially truncated blocks - in @chain[].bh and pointers to
1016  *      their last elements that should not be removed - in
1017  *      @chain[].p. Return value is the pointer to last filled element
1018  *      of @chain.
1019  *
1020  *      The work left to caller to do the actual freeing of subtrees:
1021  *              a) free the subtree starting from *@top
1022  *              b) free the subtrees whose roots are stored in
1023  *                      (@chain[i].p+1 .. end of @chain[i].bh->b_data)
1024  *              c) free the subtrees growing from the inode past the @chain[0].
1025  *                      (no partially truncated stuff there).  */
1026
1027 static Indirect *ext4_find_shared(struct inode *inode, int depth,
1028                                   ext4_lblk_t offsets[4], Indirect chain[4],
1029                                   __le32 *top)
1030 {
1031         Indirect *partial, *p;
1032         int k, err;
1033
1034         *top = 0;
1035         /* Make k index the deepest non-null offset + 1 */
1036         for (k = depth; k > 1 && !offsets[k-1]; k--)
1037                 ;
1038         partial = ext4_get_branch(inode, k, offsets, chain, &err);
1039         /* Writer: pointers */
1040         if (!partial)
1041                 partial = chain + k-1;
1042         /*
1043          * If the branch acquired continuation since we've looked at it -
1044          * fine, it should all survive and (new) top doesn't belong to us.
1045          */
1046         if (!partial->key && *partial->p)
1047                 /* Writer: end */
1048                 goto no_top;
1049         for (p = partial; (p > chain) && all_zeroes((__le32 *) p->bh->b_data, p->p); p--)
1050                 ;
1051         /*
1052          * OK, we've found the last block that must survive. The rest of our
1053          * branch should be detached before unlocking. However, if that rest
1054          * of branch is all ours and does not grow immediately from the inode
1055          * it's easier to cheat and just decrement partial->p.
1056          */
1057         if (p == chain + k - 1 && p > chain) {
1058                 p->p--;
1059         } else {
1060                 *top = *p->p;
1061                 /* Nope, don't do this in ext4.  Must leave the tree intact */
1062 #if 0
1063                 *p->p = 0;
1064 #endif
1065         }
1066         /* Writer: end */
1067
1068         while (partial > p) {
1069                 brelse(partial->bh);
1070                 partial--;
1071         }
1072 no_top:
1073         return partial;
1074 }
1075
1076 /*
1077  * Zero a number of block pointers in either an inode or an indirect block.
1078  * If we restart the transaction we must again get write access to the
1079  * indirect block for further modification.
1080  *
1081  * We release `count' blocks on disk, but (last - first) may be greater
1082  * than `count' because there can be holes in there.
1083  *
1084  * Return 0 on success, 1 on invalid block range
1085  * and < 0 on fatal error.
1086  */
1087 static int ext4_clear_blocks(handle_t *handle, struct inode *inode,
1088                              struct buffer_head *bh,
1089                              ext4_fsblk_t block_to_free,
1090                              unsigned long count, __le32 *first,
1091                              __le32 *last)
1092 {
1093         __le32 *p;
1094         int     flags = EXT4_FREE_BLOCKS_FORGET | EXT4_FREE_BLOCKS_VALIDATED;
1095         int     err;
1096
1097         if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
1098                 flags |= EXT4_FREE_BLOCKS_METADATA;
1099
1100         if (!ext4_data_block_valid(EXT4_SB(inode->i_sb), block_to_free,
1101                                    count)) {
1102                 EXT4_ERROR_INODE(inode, "attempt to clear invalid "
1103                                  "blocks %llu len %lu",
1104                                  (unsigned long long) block_to_free, count);
1105                 return 1;
1106         }
1107
1108         if (try_to_extend_transaction(handle, inode)) {
1109                 if (bh) {
1110                         BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
1111                         err = ext4_handle_dirty_metadata(handle, inode, bh);
1112                         if (unlikely(err))
1113                                 goto out_err;
1114                 }
1115                 err = ext4_mark_inode_dirty(handle, inode);
1116                 if (unlikely(err))
1117                         goto out_err;
1118                 err = ext4_truncate_restart_trans(handle, inode,
1119                                         ext4_blocks_for_truncate(inode));
1120                 if (unlikely(err))
1121                         goto out_err;
1122                 if (bh) {
1123                         BUFFER_TRACE(bh, "retaking write access");
1124                         err = ext4_journal_get_write_access(handle, bh);
1125                         if (unlikely(err))
1126                                 goto out_err;
1127                 }
1128         }
1129
1130         for (p = first; p < last; p++)
1131                 *p = 0;
1132
1133         ext4_free_blocks(handle, inode, NULL, block_to_free, count, flags);
1134         return 0;
1135 out_err:
1136         ext4_std_error(inode->i_sb, err);
1137         return err;
1138 }
1139
1140 /**
1141  * ext4_free_data - free a list of data blocks
1142  * @handle:     handle for this transaction
1143  * @inode:      inode we are dealing with
1144  * @this_bh:    indirect buffer_head which contains *@first and *@last
1145  * @first:      array of block numbers
1146  * @last:       points immediately past the end of array
1147  *
1148  * We are freeing all blocks referred from that array (numbers are stored as
1149  * little-endian 32-bit) and updating @inode->i_blocks appropriately.
1150  *
1151  * We accumulate contiguous runs of blocks to free.  Conveniently, if these
1152  * blocks are contiguous then releasing them at one time will only affect one
1153  * or two bitmap blocks (+ group descriptor(s) and superblock) and we won't
1154  * actually use a lot of journal space.
1155  *
1156  * @this_bh will be %NULL if @first and @last point into the inode's direct
1157  * block pointers.
1158  */
1159 static void ext4_free_data(handle_t *handle, struct inode *inode,
1160                            struct buffer_head *this_bh,
1161                            __le32 *first, __le32 *last)
1162 {
1163         ext4_fsblk_t block_to_free = 0;    /* Starting block # of a run */
1164         unsigned long count = 0;            /* Number of blocks in the run */
1165         __le32 *block_to_free_p = NULL;     /* Pointer into inode/ind
1166                                                corresponding to
1167                                                block_to_free */
1168         ext4_fsblk_t nr;                    /* Current block # */
1169         __le32 *p;                          /* Pointer into inode/ind
1170                                                for current block */
1171         int err = 0;
1172
1173         if (this_bh) {                          /* For indirect block */
1174                 BUFFER_TRACE(this_bh, "get_write_access");
1175                 err = ext4_journal_get_write_access(handle, this_bh);
1176                 /* Important: if we can't update the indirect pointers
1177                  * to the blocks, we can't free them. */
1178                 if (err)
1179                         return;
1180         }
1181
1182         for (p = first; p < last; p++) {
1183                 nr = le32_to_cpu(*p);
1184                 if (nr) {
1185                         /* accumulate blocks to free if they're contiguous */
1186                         if (count == 0) {
1187                                 block_to_free = nr;
1188                                 block_to_free_p = p;
1189                                 count = 1;
1190                         } else if (nr == block_to_free + count) {
1191                                 count++;
1192                         } else {
1193                                 err = ext4_clear_blocks(handle, inode, this_bh,
1194                                                         block_to_free, count,
1195                                                         block_to_free_p, p);
1196                                 if (err)
1197                                         break;
1198                                 block_to_free = nr;
1199                                 block_to_free_p = p;
1200                                 count = 1;
1201                         }
1202                 }
1203         }
1204
1205         if (!err && count > 0)
1206                 err = ext4_clear_blocks(handle, inode, this_bh, block_to_free,
1207                                         count, block_to_free_p, p);
1208         if (err < 0)
1209                 /* fatal error */
1210                 return;
1211
1212         if (this_bh) {
1213                 BUFFER_TRACE(this_bh, "call ext4_handle_dirty_metadata");
1214
1215                 /*
1216                  * The buffer head should have an attached journal head at this
1217                  * point. However, if the data is corrupted and an indirect
1218                  * block pointed to itself, it would have been detached when
1219                  * the block was cleared. Check for this instead of OOPSing.
1220                  */
1221                 if ((EXT4_JOURNAL(inode) == NULL) || bh2jh(this_bh))
1222                         ext4_handle_dirty_metadata(handle, inode, this_bh);
1223                 else
1224                         EXT4_ERROR_INODE(inode,
1225                                          "circular indirect block detected at "
1226                                          "block %llu",
1227                                 (unsigned long long) this_bh->b_blocknr);
1228         }
1229 }
1230
1231 /**
1232  *      ext4_free_branches - free an array of branches
1233  *      @handle: JBD handle for this transaction
1234  *      @inode: inode we are dealing with
1235  *      @parent_bh: the buffer_head which contains *@first and *@last
1236  *      @first: array of block numbers
1237  *      @last:  pointer immediately past the end of array
1238  *      @depth: depth of the branches to free
1239  *
1240  *      We are freeing all blocks referred from these branches (numbers are
1241  *      stored as little-endian 32-bit) and updating @inode->i_blocks
1242  *      appropriately.
1243  */
1244 static void ext4_free_branches(handle_t *handle, struct inode *inode,
1245                                struct buffer_head *parent_bh,
1246                                __le32 *first, __le32 *last, int depth)
1247 {
1248         ext4_fsblk_t nr;
1249         __le32 *p;
1250
1251         if (ext4_handle_is_aborted(handle))
1252                 return;
1253
1254         if (depth--) {
1255                 struct buffer_head *bh;
1256                 int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1257                 p = last;
1258                 while (--p >= first) {
1259                         nr = le32_to_cpu(*p);
1260                         if (!nr)
1261                                 continue;               /* A hole */
1262
1263                         if (!ext4_data_block_valid(EXT4_SB(inode->i_sb),
1264                                                    nr, 1)) {
1265                                 EXT4_ERROR_INODE(inode,
1266                                                  "invalid indirect mapped "
1267                                                  "block %lu (level %d)",
1268                                                  (unsigned long) nr, depth);
1269                                 break;
1270                         }
1271
1272                         /* Go read the buffer for the next level down */
1273                         bh = sb_bread(inode->i_sb, nr);
1274
1275                         /*
1276                          * A read failure? Report error and clear slot
1277                          * (should be rare).
1278                          */
1279                         if (!bh) {
1280                                 EXT4_ERROR_INODE_BLOCK(inode, nr,
1281                                                        "Read failure");
1282                                 continue;
1283                         }
1284
1285                         /* This zaps the entire block.  Bottom up. */
1286                         BUFFER_TRACE(bh, "free child branches");
1287                         ext4_free_branches(handle, inode, bh,
1288                                         (__le32 *) bh->b_data,
1289                                         (__le32 *) bh->b_data + addr_per_block,
1290                                         depth);
1291                         brelse(bh);
1292
1293                         /*
1294                          * Everything below this this pointer has been
1295                          * released.  Now let this top-of-subtree go.
1296                          *
1297                          * We want the freeing of this indirect block to be
1298                          * atomic in the journal with the updating of the
1299                          * bitmap block which owns it.  So make some room in
1300                          * the journal.
1301                          *
1302                          * We zero the parent pointer *after* freeing its
1303                          * pointee in the bitmaps, so if extend_transaction()
1304                          * for some reason fails to put the bitmap changes and
1305                          * the release into the same transaction, recovery
1306                          * will merely complain about releasing a free block,
1307                          * rather than leaking blocks.
1308                          */
1309                         if (ext4_handle_is_aborted(handle))
1310                                 return;
1311                         if (try_to_extend_transaction(handle, inode)) {
1312                                 ext4_mark_inode_dirty(handle, inode);
1313                                 ext4_truncate_restart_trans(handle, inode,
1314                                             ext4_blocks_for_truncate(inode));
1315                         }
1316
1317                         /*
1318                          * The forget flag here is critical because if
1319                          * we are journaling (and not doing data
1320                          * journaling), we have to make sure a revoke
1321                          * record is written to prevent the journal
1322                          * replay from overwriting the (former)
1323                          * indirect block if it gets reallocated as a
1324                          * data block.  This must happen in the same
1325                          * transaction where the data blocks are
1326                          * actually freed.
1327                          */
1328                         ext4_free_blocks(handle, inode, NULL, nr, 1,
1329                                          EXT4_FREE_BLOCKS_METADATA|
1330                                          EXT4_FREE_BLOCKS_FORGET);
1331
1332                         if (parent_bh) {
1333                                 /*
1334                                  * The block which we have just freed is
1335                                  * pointed to by an indirect block: journal it
1336                                  */
1337                                 BUFFER_TRACE(parent_bh, "get_write_access");
1338                                 if (!ext4_journal_get_write_access(handle,
1339                                                                    parent_bh)){
1340                                         *p = 0;
1341                                         BUFFER_TRACE(parent_bh,
1342                                         "call ext4_handle_dirty_metadata");
1343                                         ext4_handle_dirty_metadata(handle,
1344                                                                    inode,
1345                                                                    parent_bh);
1346                                 }
1347                         }
1348                 }
1349         } else {
1350                 /* We have reached the bottom of the tree. */
1351                 BUFFER_TRACE(parent_bh, "free data blocks");
1352                 ext4_free_data(handle, inode, parent_bh, first, last);
1353         }
1354 }
1355
1356 void ext4_ind_truncate(struct inode *inode)
1357 {
1358         handle_t *handle;
1359         struct ext4_inode_info *ei = EXT4_I(inode);
1360         __le32 *i_data = ei->i_data;
1361         int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1362         struct address_space *mapping = inode->i_mapping;
1363         ext4_lblk_t offsets[4];
1364         Indirect chain[4];
1365         Indirect *partial;
1366         __le32 nr = 0;
1367         int n = 0;
1368         ext4_lblk_t last_block, max_block;
1369         unsigned blocksize = inode->i_sb->s_blocksize;
1370
1371         handle = start_transaction(inode);
1372         if (IS_ERR(handle))
1373                 return;         /* AKPM: return what? */
1374
1375         last_block = (inode->i_size + blocksize-1)
1376                                         >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
1377         max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
1378                                         >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
1379
1380         if (inode->i_size & (blocksize - 1))
1381                 if (ext4_block_truncate_page(handle, mapping, inode->i_size))
1382                         goto out_stop;
1383
1384         if (last_block != max_block) {
1385                 n = ext4_block_to_path(inode, last_block, offsets, NULL);
1386                 if (n == 0)
1387                         goto out_stop;  /* error */
1388         }
1389
1390         /*
1391          * OK.  This truncate is going to happen.  We add the inode to the
1392          * orphan list, so that if this truncate spans multiple transactions,
1393          * and we crash, we will resume the truncate when the filesystem
1394          * recovers.  It also marks the inode dirty, to catch the new size.
1395          *
1396          * Implication: the file must always be in a sane, consistent
1397          * truncatable state while each transaction commits.
1398          */
1399         if (ext4_orphan_add(handle, inode))
1400                 goto out_stop;
1401
1402         /*
1403          * From here we block out all ext4_get_block() callers who want to
1404          * modify the block allocation tree.
1405          */
1406         down_write(&ei->i_data_sem);
1407
1408         ext4_discard_preallocations(inode);
1409
1410         /*
1411          * The orphan list entry will now protect us from any crash which
1412          * occurs before the truncate completes, so it is now safe to propagate
1413          * the new, shorter inode size (held for now in i_size) into the
1414          * on-disk inode. We do this via i_disksize, which is the value which
1415          * ext4 *really* writes onto the disk inode.
1416          */
1417         ei->i_disksize = inode->i_size;
1418
1419         if (last_block == max_block) {
1420                 /*
1421                  * It is unnecessary to free any data blocks if last_block is
1422                  * equal to the indirect block limit.
1423                  */
1424                 goto out_unlock;
1425         } else if (n == 1) {            /* direct blocks */
1426                 ext4_free_data(handle, inode, NULL, i_data+offsets[0],
1427                                i_data + EXT4_NDIR_BLOCKS);
1428                 goto do_indirects;
1429         }
1430
1431         partial = ext4_find_shared(inode, n, offsets, chain, &nr);
1432         /* Kill the top of shared branch (not detached) */
1433         if (nr) {
1434                 if (partial == chain) {
1435                         /* Shared branch grows from the inode */
1436                         ext4_free_branches(handle, inode, NULL,
1437                                            &nr, &nr+1, (chain+n-1) - partial);
1438                         *partial->p = 0;
1439                         /*
1440                          * We mark the inode dirty prior to restart,
1441                          * and prior to stop.  No need for it here.
1442                          */
1443                 } else {
1444                         /* Shared branch grows from an indirect block */
1445                         BUFFER_TRACE(partial->bh, "get_write_access");
1446                         ext4_free_branches(handle, inode, partial->bh,
1447                                         partial->p,
1448                                         partial->p+1, (chain+n-1) - partial);
1449                 }
1450         }
1451         /* Clear the ends of indirect blocks on the shared branch */
1452         while (partial > chain) {
1453                 ext4_free_branches(handle, inode, partial->bh, partial->p + 1,
1454                                    (__le32*)partial->bh->b_data+addr_per_block,
1455                                    (chain+n-1) - partial);
1456                 BUFFER_TRACE(partial->bh, "call brelse");
1457                 brelse(partial->bh);
1458                 partial--;
1459         }
1460 do_indirects:
1461         /* Kill the remaining (whole) subtrees */
1462         switch (offsets[0]) {
1463         default:
1464                 nr = i_data[EXT4_IND_BLOCK];
1465                 if (nr) {
1466                         ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
1467                         i_data[EXT4_IND_BLOCK] = 0;
1468                 }
1469         case EXT4_IND_BLOCK:
1470                 nr = i_data[EXT4_DIND_BLOCK];
1471                 if (nr) {
1472                         ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 2);
1473                         i_data[EXT4_DIND_BLOCK] = 0;
1474                 }
1475         case EXT4_DIND_BLOCK:
1476                 nr = i_data[EXT4_TIND_BLOCK];
1477                 if (nr) {
1478                         ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
1479                         i_data[EXT4_TIND_BLOCK] = 0;
1480                 }
1481         case EXT4_TIND_BLOCK:
1482                 ;
1483         }
1484
1485 out_unlock:
1486         up_write(&ei->i_data_sem);
1487         inode->i_mtime = inode->i_ctime = ext4_current_time(inode);
1488         ext4_mark_inode_dirty(handle, inode);
1489
1490         /*
1491          * In a multi-transaction truncate, we only make the final transaction
1492          * synchronous
1493          */
1494         if (IS_SYNC(inode))
1495                 ext4_handle_sync(handle);
1496 out_stop:
1497         /*
1498          * If this was a simple ftruncate(), and the file will remain alive
1499          * then we need to clear up the orphan record which we created above.
1500          * However, if this was a real unlink then we were called by
1501          * ext4_delete_inode(), and we allow that function to clean up the
1502          * orphan info for us.
1503          */
1504         if (inode->i_nlink)
1505                 ext4_orphan_del(handle, inode);
1506
1507         ext4_journal_stop(handle);
1508         trace_ext4_truncate_exit(inode);
1509 }
1510