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Linux/fs/ext4/indirect.c

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  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 "ext4_jbd2.h"
 24 #include "truncate.h"
 25 #include <linux/dax.h>
 26 #include <linux/uio.h>
 27 
 28 #include <trace/events/ext4.h>
 29 
 30 typedef struct {
 31         __le32  *p;
 32         __le32  key;
 33         struct buffer_head *bh;
 34 } Indirect;
 35 
 36 static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
 37 {
 38         p->key = *(p->p = v);
 39         p->bh = bh;
 40 }
 41 
 42 /**
 43  *      ext4_block_to_path - parse the block number into array of offsets
 44  *      @inode: inode in question (we are only interested in its superblock)
 45  *      @i_block: block number to be parsed
 46  *      @offsets: array to store the offsets in
 47  *      @boundary: set this non-zero if the referred-to block is likely to be
 48  *             followed (on disk) by an indirect block.
 49  *
 50  *      To store the locations of file's data ext4 uses a data structure common
 51  *      for UNIX filesystems - tree of pointers anchored in the inode, with
 52  *      data blocks at leaves and indirect blocks in intermediate nodes.
 53  *      This function translates the block number into path in that tree -
 54  *      return value is the path length and @offsets[n] is the offset of
 55  *      pointer to (n+1)th node in the nth one. If @block is out of range
 56  *      (negative or too large) warning is printed and zero returned.
 57  *
 58  *      Note: function doesn't find node addresses, so no IO is needed. All
 59  *      we need to know is the capacity of indirect blocks (taken from the
 60  *      inode->i_sb).
 61  */
 62 
 63 /*
 64  * Portability note: the last comparison (check that we fit into triple
 65  * indirect block) is spelled differently, because otherwise on an
 66  * architecture with 32-bit longs and 8Kb pages we might get into trouble
 67  * if our filesystem had 8Kb blocks. We might use long long, but that would
 68  * kill us on x86. Oh, well, at least the sign propagation does not matter -
 69  * i_block would have to be negative in the very beginning, so we would not
 70  * get there at all.
 71  */
 72 
 73 static int ext4_block_to_path(struct inode *inode,
 74                               ext4_lblk_t i_block,
 75                               ext4_lblk_t offsets[4], int *boundary)
 76 {
 77         int ptrs = EXT4_ADDR_PER_BLOCK(inode->i_sb);
 78         int ptrs_bits = EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb);
 79         const long direct_blocks = EXT4_NDIR_BLOCKS,
 80                 indirect_blocks = ptrs,
 81                 double_blocks = (1 << (ptrs_bits * 2));
 82         int n = 0;
 83         int final = 0;
 84 
 85         if (i_block < direct_blocks) {
 86                 offsets[n++] = i_block;
 87                 final = direct_blocks;
 88         } else if ((i_block -= direct_blocks) < indirect_blocks) {
 89                 offsets[n++] = EXT4_IND_BLOCK;
 90                 offsets[n++] = i_block;
 91                 final = ptrs;
 92         } else if ((i_block -= indirect_blocks) < double_blocks) {
 93                 offsets[n++] = EXT4_DIND_BLOCK;
 94                 offsets[n++] = i_block >> ptrs_bits;
 95                 offsets[n++] = i_block & (ptrs - 1);
 96                 final = ptrs;
 97         } else if (((i_block -= double_blocks) >> (ptrs_bits * 2)) < ptrs) {
 98                 offsets[n++] = EXT4_TIND_BLOCK;
 99                 offsets[n++] = i_block >> (ptrs_bits * 2);
100                 offsets[n++] = (i_block >> ptrs_bits) & (ptrs - 1);
101                 offsets[n++] = i_block & (ptrs - 1);
102                 final = ptrs;
103         } else {
104                 ext4_warning(inode->i_sb, "block %lu > max in inode %lu",
105                              i_block + direct_blocks +
106                              indirect_blocks + double_blocks, inode->i_ino);
107         }
108         if (boundary)
109                 *boundary = final - 1 - (i_block & (ptrs - 1));
110         return n;
111 }
112 
113 /**
114  *      ext4_get_branch - read the chain of indirect blocks leading to data
115  *      @inode: inode in question
116  *      @depth: depth of the chain (1 - direct pointer, etc.)
117  *      @offsets: offsets of pointers in inode/indirect blocks
118  *      @chain: place to store the result
119  *      @err: here we store the error value
120  *
121  *      Function fills the array of triples <key, p, bh> and returns %NULL
122  *      if everything went OK or the pointer to the last filled triple
123  *      (incomplete one) otherwise. Upon the return chain[i].key contains
124  *      the number of (i+1)-th block in the chain (as it is stored in memory,
125  *      i.e. little-endian 32-bit), chain[i].p contains the address of that
126  *      number (it points into struct inode for i==0 and into the bh->b_data
127  *      for i>0) and chain[i].bh points to the buffer_head of i-th indirect
128  *      block for i>0 and NULL for i==0. In other words, it holds the block
129  *      numbers of the chain, addresses they were taken from (and where we can
130  *      verify that chain did not change) and buffer_heads hosting these
131  *      numbers.
132  *
133  *      Function stops when it stumbles upon zero pointer (absent block)
134  *              (pointer to last triple returned, *@err == 0)
135  *      or when it gets an IO error reading an indirect block
136  *              (ditto, *@err == -EIO)
137  *      or when it reads all @depth-1 indirect blocks successfully and finds
138  *      the whole chain, all way to the data (returns %NULL, *err == 0).
139  *
140  *      Need to be called with
141  *      down_read(&EXT4_I(inode)->i_data_sem)
142  */
143 static Indirect *ext4_get_branch(struct inode *inode, int depth,
144                                  ext4_lblk_t  *offsets,
145                                  Indirect chain[4], int *err)
146 {
147         struct super_block *sb = inode->i_sb;
148         Indirect *p = chain;
149         struct buffer_head *bh;
150         int ret = -EIO;
151 
152         *err = 0;
153         /* i_data is not going away, no lock needed */
154         add_chain(chain, NULL, EXT4_I(inode)->i_data + *offsets);
155         if (!p->key)
156                 goto no_block;
157         while (--depth) {
158                 bh = sb_getblk(sb, le32_to_cpu(p->key));
159                 if (unlikely(!bh)) {
160                         ret = -ENOMEM;
161                         goto failure;
162                 }
163 
164                 if (!bh_uptodate_or_lock(bh)) {
165                         if (bh_submit_read(bh) < 0) {
166                                 put_bh(bh);
167                                 goto failure;
168                         }
169                         /* validate block references */
170                         if (ext4_check_indirect_blockref(inode, bh)) {
171                                 put_bh(bh);
172                                 goto failure;
173                         }
174                 }
175 
176                 add_chain(++p, bh, (__le32 *)bh->b_data + *++offsets);
177                 /* Reader: end */
178                 if (!p->key)
179                         goto no_block;
180         }
181         return NULL;
182 
183 failure:
184         *err = ret;
185 no_block:
186         return p;
187 }
188 
189 /**
190  *      ext4_find_near - find a place for allocation with sufficient locality
191  *      @inode: owner
192  *      @ind: descriptor of indirect block.
193  *
194  *      This function returns the preferred place for block allocation.
195  *      It is used when heuristic for sequential allocation fails.
196  *      Rules are:
197  *        + if there is a block to the left of our position - allocate near it.
198  *        + if pointer will live in indirect block - allocate near that block.
199  *        + if pointer will live in inode - allocate in the same
200  *          cylinder group.
201  *
202  * In the latter case we colour the starting block by the callers PID to
203  * prevent it from clashing with concurrent allocations for a different inode
204  * in the same block group.   The PID is used here so that functionally related
205  * files will be close-by on-disk.
206  *
207  *      Caller must make sure that @ind is valid and will stay that way.
208  */
209 static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
210 {
211         struct ext4_inode_info *ei = EXT4_I(inode);
212         __le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
213         __le32 *p;
214 
215         /* Try to find previous block */
216         for (p = ind->p - 1; p >= start; p--) {
217                 if (*p)
218                         return le32_to_cpu(*p);
219         }
220 
221         /* No such thing, so let's try location of indirect block */
222         if (ind->bh)
223                 return ind->bh->b_blocknr;
224 
225         /*
226          * It is going to be referred to from the inode itself? OK, just put it
227          * into the same cylinder group then.
228          */
229         return ext4_inode_to_goal_block(inode);
230 }
231 
232 /**
233  *      ext4_find_goal - find a preferred place for allocation.
234  *      @inode: owner
235  *      @block:  block we want
236  *      @partial: pointer to the last triple within a chain
237  *
238  *      Normally this function find the preferred place for block allocation,
239  *      returns it.
240  *      Because this is only used for non-extent files, we limit the block nr
241  *      to 32 bits.
242  */
243 static ext4_fsblk_t ext4_find_goal(struct inode *inode, ext4_lblk_t block,
244                                    Indirect *partial)
245 {
246         ext4_fsblk_t goal;
247 
248         /*
249          * XXX need to get goal block from mballoc's data structures
250          */
251 
252         goal = ext4_find_near(inode, partial);
253         goal = goal & EXT4_MAX_BLOCK_FILE_PHYS;
254         return goal;
255 }
256 
257 /**
258  *      ext4_blks_to_allocate - Look up the block map and count the number
259  *      of direct blocks need to be allocated for the given branch.
260  *
261  *      @branch: chain of indirect blocks
262  *      @k: number of blocks need for indirect blocks
263  *      @blks: number of data blocks to be mapped.
264  *      @blocks_to_boundary:  the offset in the indirect block
265  *
266  *      return the total number of blocks to be allocate, including the
267  *      direct and indirect blocks.
268  */
269 static int ext4_blks_to_allocate(Indirect *branch, int k, unsigned int blks,
270                                  int blocks_to_boundary)
271 {
272         unsigned int count = 0;
273 
274         /*
275          * Simple case, [t,d]Indirect block(s) has not allocated yet
276          * then it's clear blocks on that path have not allocated
277          */
278         if (k > 0) {
279                 /* right now we don't handle cross boundary allocation */
280                 if (blks < blocks_to_boundary + 1)
281                         count += blks;
282                 else
283                         count += blocks_to_boundary + 1;
284                 return count;
285         }
286 
287         count++;
288         while (count < blks && count <= blocks_to_boundary &&
289                 le32_to_cpu(*(branch[0].p + count)) == 0) {
290                 count++;
291         }
292         return count;
293 }
294 
295 /**
296  *      ext4_alloc_branch - allocate and set up a chain of blocks.
297  *      @handle: handle for this transaction
298  *      @inode: owner
299  *      @indirect_blks: number of allocated indirect blocks
300  *      @blks: number of allocated direct blocks
301  *      @goal: preferred place for allocation
302  *      @offsets: offsets (in the blocks) to store the pointers to next.
303  *      @branch: place to store the chain in.
304  *
305  *      This function allocates blocks, zeroes out all but the last one,
306  *      links them into chain and (if we are synchronous) writes them to disk.
307  *      In other words, it prepares a branch that can be spliced onto the
308  *      inode. It stores the information about that chain in the branch[], in
309  *      the same format as ext4_get_branch() would do. We are calling it after
310  *      we had read the existing part of chain and partial points to the last
311  *      triple of that (one with zero ->key). Upon the exit we have the same
312  *      picture as after the successful ext4_get_block(), except that in one
313  *      place chain is disconnected - *branch->p is still zero (we did not
314  *      set the last link), but branch->key contains the number that should
315  *      be placed into *branch->p to fill that gap.
316  *
317  *      If allocation fails we free all blocks we've allocated (and forget
318  *      their buffer_heads) and return the error value the from failed
319  *      ext4_alloc_block() (normally -ENOSPC). Otherwise we set the chain
320  *      as described above and return 0.
321  */
322 static int ext4_alloc_branch(handle_t *handle,
323                              struct ext4_allocation_request *ar,
324                              int indirect_blks, ext4_lblk_t *offsets,
325                              Indirect *branch)
326 {
327         struct buffer_head *            bh;
328         ext4_fsblk_t                    b, new_blocks[4];
329         __le32                          *p;
330         int                             i, j, err, len = 1;
331 
332         for (i = 0; i <= indirect_blks; i++) {
333                 if (i == indirect_blks) {
334                         new_blocks[i] = ext4_mb_new_blocks(handle, ar, &err);
335                 } else
336                         ar->goal = new_blocks[i] = ext4_new_meta_blocks(handle,
337                                         ar->inode, ar->goal,
338                                         ar->flags & EXT4_MB_DELALLOC_RESERVED,
339                                         NULL, &err);
340                 if (err) {
341                         i--;
342                         goto failed;
343                 }
344                 branch[i].key = cpu_to_le32(new_blocks[i]);
345                 if (i == 0)
346                         continue;
347 
348                 bh = branch[i].bh = sb_getblk(ar->inode->i_sb, new_blocks[i-1]);
349                 if (unlikely(!bh)) {
350                         err = -ENOMEM;
351                         goto failed;
352                 }
353                 lock_buffer(bh);
354                 BUFFER_TRACE(bh, "call get_create_access");
355                 err = ext4_journal_get_create_access(handle, bh);
356                 if (err) {
357                         unlock_buffer(bh);
358                         goto failed;
359                 }
360 
361                 memset(bh->b_data, 0, bh->b_size);
362                 p = branch[i].p = (__le32 *) bh->b_data + offsets[i];
363                 b = new_blocks[i];
364 
365                 if (i == indirect_blks)
366                         len = ar->len;
367                 for (j = 0; j < len; j++)
368                         *p++ = cpu_to_le32(b++);
369 
370                 BUFFER_TRACE(bh, "marking uptodate");
371                 set_buffer_uptodate(bh);
372                 unlock_buffer(bh);
373 
374                 BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
375                 err = ext4_handle_dirty_metadata(handle, ar->inode, bh);
376                 if (err)
377                         goto failed;
378         }
379         return 0;
380 failed:
381         for (; i >= 0; i--) {
382                 /*
383                  * We want to ext4_forget() only freshly allocated indirect
384                  * blocks.  Buffer for new_blocks[i-1] is at branch[i].bh and
385                  * buffer at branch[0].bh is indirect block / inode already
386                  * existing before ext4_alloc_branch() was called.
387                  */
388                 if (i > 0 && i != indirect_blks && branch[i].bh)
389                         ext4_forget(handle, 1, ar->inode, branch[i].bh,
390                                     branch[i].bh->b_blocknr);
391                 ext4_free_blocks(handle, ar->inode, NULL, new_blocks[i],
392                                  (i == indirect_blks) ? ar->len : 1, 0);
393         }
394         return err;
395 }
396 
397 /**
398  * ext4_splice_branch - splice the allocated branch onto inode.
399  * @handle: handle for this transaction
400  * @inode: owner
401  * @block: (logical) number of block we are adding
402  * @chain: chain of indirect blocks (with a missing link - see
403  *      ext4_alloc_branch)
404  * @where: location of missing link
405  * @num:   number of indirect blocks we are adding
406  * @blks:  number of direct blocks we are adding
407  *
408  * This function fills the missing link and does all housekeeping needed in
409  * inode (->i_blocks, etc.). In case of success we end up with the full
410  * chain to new block and return 0.
411  */
412 static int ext4_splice_branch(handle_t *handle,
413                               struct ext4_allocation_request *ar,
414                               Indirect *where, int num)
415 {
416         int i;
417         int err = 0;
418         ext4_fsblk_t current_block;
419 
420         /*
421          * If we're splicing into a [td]indirect block (as opposed to the
422          * inode) then we need to get write access to the [td]indirect block
423          * before the splice.
424          */
425         if (where->bh) {
426                 BUFFER_TRACE(where->bh, "get_write_access");
427                 err = ext4_journal_get_write_access(handle, where->bh);
428                 if (err)
429                         goto err_out;
430         }
431         /* That's it */
432 
433         *where->p = where->key;
434 
435         /*
436          * Update the host buffer_head or inode to point to more just allocated
437          * direct blocks blocks
438          */
439         if (num == 0 && ar->len > 1) {
440                 current_block = le32_to_cpu(where->key) + 1;
441                 for (i = 1; i < ar->len; i++)
442                         *(where->p + i) = cpu_to_le32(current_block++);
443         }
444 
445         /* We are done with atomic stuff, now do the rest of housekeeping */
446         /* had we spliced it onto indirect block? */
447         if (where->bh) {
448                 /*
449                  * If we spliced it onto an indirect block, we haven't
450                  * altered the inode.  Note however that if it is being spliced
451                  * onto an indirect block at the very end of the file (the
452                  * file is growing) then we *will* alter the inode to reflect
453                  * the new i_size.  But that is not done here - it is done in
454                  * generic_commit_write->__mark_inode_dirty->ext4_dirty_inode.
455                  */
456                 jbd_debug(5, "splicing indirect only\n");
457                 BUFFER_TRACE(where->bh, "call ext4_handle_dirty_metadata");
458                 err = ext4_handle_dirty_metadata(handle, ar->inode, where->bh);
459                 if (err)
460                         goto err_out;
461         } else {
462                 /*
463                  * OK, we spliced it into the inode itself on a direct block.
464                  */
465                 ext4_mark_inode_dirty(handle, ar->inode);
466                 jbd_debug(5, "splicing direct\n");
467         }
468         return err;
469 
470 err_out:
471         for (i = 1; i <= num; i++) {
472                 /*
473                  * branch[i].bh is newly allocated, so there is no
474                  * need to revoke the block, which is why we don't
475                  * need to set EXT4_FREE_BLOCKS_METADATA.
476                  */
477                 ext4_free_blocks(handle, ar->inode, where[i].bh, 0, 1,
478                                  EXT4_FREE_BLOCKS_FORGET);
479         }
480         ext4_free_blocks(handle, ar->inode, NULL, le32_to_cpu(where[num].key),
481                          ar->len, 0);
482 
483         return err;
484 }
485 
486 /*
487  * The ext4_ind_map_blocks() function handles non-extents inodes
488  * (i.e., using the traditional indirect/double-indirect i_blocks
489  * scheme) for ext4_map_blocks().
490  *
491  * Allocation strategy is simple: if we have to allocate something, we will
492  * have to go the whole way to leaf. So let's do it before attaching anything
493  * to tree, set linkage between the newborn blocks, write them if sync is
494  * required, recheck the path, free and repeat if check fails, otherwise
495  * set the last missing link (that will protect us from any truncate-generated
496  * removals - all blocks on the path are immune now) and possibly force the
497  * write on the parent block.
498  * That has a nice additional property: no special recovery from the failed
499  * allocations is needed - we simply release blocks and do not touch anything
500  * reachable from inode.
501  *
502  * `handle' can be NULL if create == 0.
503  *
504  * return > 0, # of blocks mapped or allocated.
505  * return = 0, if plain lookup failed.
506  * return < 0, error case.
507  *
508  * The ext4_ind_get_blocks() function should be called with
509  * down_write(&EXT4_I(inode)->i_data_sem) if allocating filesystem
510  * blocks (i.e., flags has EXT4_GET_BLOCKS_CREATE set) or
511  * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system
512  * blocks.
513  */
514 int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
515                         struct ext4_map_blocks *map,
516                         int flags)
517 {
518         struct ext4_allocation_request ar;
519         int err = -EIO;
520         ext4_lblk_t offsets[4];
521         Indirect chain[4];
522         Indirect *partial;
523         int indirect_blks;
524         int blocks_to_boundary = 0;
525         int depth;
526         int count = 0;
527         ext4_fsblk_t first_block = 0;
528 
529         trace_ext4_ind_map_blocks_enter(inode, map->m_lblk, map->m_len, flags);
530         J_ASSERT(!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)));
531         J_ASSERT(handle != NULL || (flags & EXT4_GET_BLOCKS_CREATE) == 0);
532         depth = ext4_block_to_path(inode, map->m_lblk, offsets,
533                                    &blocks_to_boundary);
534 
535         if (depth == 0)
536                 goto out;
537 
538         partial = ext4_get_branch(inode, depth, offsets, chain, &err);
539 
540         /* Simplest case - block found, no allocation needed */
541         if (!partial) {
542                 first_block = le32_to_cpu(chain[depth - 1].key);
543                 count++;
544                 /*map more blocks*/
545                 while (count < map->m_len && count <= blocks_to_boundary) {
546                         ext4_fsblk_t blk;
547 
548                         blk = le32_to_cpu(*(chain[depth-1].p + count));
549 
550                         if (blk == first_block + count)
551                                 count++;
552                         else
553                                 break;
554                 }
555                 goto got_it;
556         }
557 
558         /* Next simple case - plain lookup failed */
559         if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
560                 unsigned epb = inode->i_sb->s_blocksize / sizeof(u32);
561                 int i;
562 
563                 /* Count number blocks in a subtree under 'partial' */
564                 count = 1;
565                 for (i = 0; partial + i != chain + depth - 1; i++)
566                         count *= epb;
567                 /* Fill in size of a hole we found */
568                 map->m_pblk = 0;
569                 map->m_len = min_t(unsigned int, map->m_len, count);
570                 goto cleanup;
571         }
572 
573         /* Failed read of indirect block */
574         if (err == -EIO)
575                 goto cleanup;
576 
577         /*
578          * Okay, we need to do block allocation.
579         */
580         if (ext4_has_feature_bigalloc(inode->i_sb)) {
581                 EXT4_ERROR_INODE(inode, "Can't allocate blocks for "
582                                  "non-extent mapped inodes with bigalloc");
583                 return -EFSCORRUPTED;
584         }
585 
586         /* Set up for the direct block allocation */
587         memset(&ar, 0, sizeof(ar));
588         ar.inode = inode;
589         ar.logical = map->m_lblk;
590         if (S_ISREG(inode->i_mode))
591                 ar.flags = EXT4_MB_HINT_DATA;
592         if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
593                 ar.flags |= EXT4_MB_DELALLOC_RESERVED;
594         if (flags & EXT4_GET_BLOCKS_METADATA_NOFAIL)
595                 ar.flags |= EXT4_MB_USE_RESERVED;
596 
597         ar.goal = ext4_find_goal(inode, map->m_lblk, partial);
598 
599         /* the number of blocks need to allocate for [d,t]indirect blocks */
600         indirect_blks = (chain + depth) - partial - 1;
601 
602         /*
603          * Next look up the indirect map to count the totoal number of
604          * direct blocks to allocate for this branch.
605          */
606         ar.len = ext4_blks_to_allocate(partial, indirect_blks,
607                                        map->m_len, blocks_to_boundary);
608 
609         /*
610          * Block out ext4_truncate while we alter the tree
611          */
612         err = ext4_alloc_branch(handle, &ar, indirect_blks,
613                                 offsets + (partial - chain), partial);
614 
615         /*
616          * The ext4_splice_branch call will free and forget any buffers
617          * on the new chain if there is a failure, but that risks using
618          * up transaction credits, especially for bitmaps where the
619          * credits cannot be returned.  Can we handle this somehow?  We
620          * may need to return -EAGAIN upwards in the worst case.  --sct
621          */
622         if (!err)
623                 err = ext4_splice_branch(handle, &ar, partial, indirect_blks);
624         if (err)
625                 goto cleanup;
626 
627         map->m_flags |= EXT4_MAP_NEW;
628 
629         ext4_update_inode_fsync_trans(handle, inode, 1);
630         count = ar.len;
631 got_it:
632         map->m_flags |= EXT4_MAP_MAPPED;
633         map->m_pblk = le32_to_cpu(chain[depth-1].key);
634         map->m_len = count;
635         if (count > blocks_to_boundary)
636                 map->m_flags |= EXT4_MAP_BOUNDARY;
637         err = count;
638         /* Clean up and exit */
639         partial = chain + depth - 1;    /* the whole chain */
640 cleanup:
641         while (partial > chain) {
642                 BUFFER_TRACE(partial->bh, "call brelse");
643                 brelse(partial->bh);
644                 partial--;
645         }
646 out:
647         trace_ext4_ind_map_blocks_exit(inode, flags, map, err);
648         return err;
649 }
650 
651 /*
652  * O_DIRECT for ext3 (or indirect map) based files
653  *
654  * If the O_DIRECT write will extend the file then add this inode to the
655  * orphan list.  So recovery will truncate it back to the original size
656  * if the machine crashes during the write.
657  *
658  * If the O_DIRECT write is intantiating holes inside i_size and the machine
659  * crashes then stale disk data _may_ be exposed inside the file. But current
660  * VFS code falls back into buffered path in that case so we are safe.
661  */
662 ssize_t ext4_ind_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
663                            loff_t offset)
664 {
665         struct file *file = iocb->ki_filp;
666         struct inode *inode = file->f_mapping->host;
667         struct ext4_inode_info *ei = EXT4_I(inode);
668         handle_t *handle;
669         ssize_t ret;
670         int orphan = 0;
671         size_t count = iov_iter_count(iter);
672         int retries = 0;
673 
674         if (iov_iter_rw(iter) == WRITE) {
675                 loff_t final_size = offset + count;
676 
677                 if (final_size > inode->i_size) {
678                         /* Credits for sb + inode write */
679                         handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
680                         if (IS_ERR(handle)) {
681                                 ret = PTR_ERR(handle);
682                                 goto out;
683                         }
684                         ret = ext4_orphan_add(handle, inode);
685                         if (ret) {
686                                 ext4_journal_stop(handle);
687                                 goto out;
688                         }
689                         orphan = 1;
690                         ei->i_disksize = inode->i_size;
691                         ext4_journal_stop(handle);
692                 }
693         }
694 
695 retry:
696         if (iov_iter_rw(iter) == READ && ext4_should_dioread_nolock(inode)) {
697                 /*
698                  * Nolock dioread optimization may be dynamically disabled
699                  * via ext4_inode_block_unlocked_dio(). Check inode's state
700                  * while holding extra i_dio_count ref.
701                  */
702                 inode_dio_begin(inode);
703                 smp_mb();
704                 if (unlikely(ext4_test_inode_state(inode,
705                                                     EXT4_STATE_DIOREAD_LOCK))) {
706                         inode_dio_end(inode);
707                         goto locked;
708                 }
709                 if (IS_DAX(inode))
710                         ret = dax_do_io(iocb, inode, iter, offset,
711                                         ext4_dio_get_block, NULL, 0);
712                 else
713                         ret = __blockdev_direct_IO(iocb, inode,
714                                                    inode->i_sb->s_bdev, iter,
715                                                    offset, ext4_dio_get_block,
716                                                    NULL, NULL, 0);
717                 inode_dio_end(inode);
718         } else {
719 locked:
720                 if (IS_DAX(inode))
721                         ret = dax_do_io(iocb, inode, iter, offset,
722                                         ext4_dio_get_block, NULL, DIO_LOCKING);
723                 else
724                         ret = blockdev_direct_IO(iocb, inode, iter, offset,
725                                                  ext4_dio_get_block);
726 
727                 if (unlikely(iov_iter_rw(iter) == WRITE && ret < 0)) {
728                         loff_t isize = i_size_read(inode);
729                         loff_t end = offset + count;
730 
731                         if (end > isize)
732                                 ext4_truncate_failed_write(inode);
733                 }
734         }
735         if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
736                 goto retry;
737 
738         if (orphan) {
739                 int err;
740 
741                 /* Credits for sb + inode write */
742                 handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
743                 if (IS_ERR(handle)) {
744                         /* This is really bad luck. We've written the data
745                          * but cannot extend i_size. Bail out and pretend
746                          * the write failed... */
747                         ret = PTR_ERR(handle);
748                         if (inode->i_nlink)
749                                 ext4_orphan_del(NULL, inode);
750 
751                         goto out;
752                 }
753                 if (inode->i_nlink)
754                         ext4_orphan_del(handle, inode);
755                 if (ret > 0) {
756                         loff_t end = offset + ret;
757                         if (end > inode->i_size) {
758                                 ei->i_disksize = end;
759                                 i_size_write(inode, end);
760                                 /*
761                                  * We're going to return a positive `ret'
762                                  * here due to non-zero-length I/O, so there's
763                                  * no way of reporting error returns from
764                                  * ext4_mark_inode_dirty() to userspace.  So
765                                  * ignore it.
766                                  */
767                                 ext4_mark_inode_dirty(handle, inode);
768                         }
769                 }
770                 err = ext4_journal_stop(handle);
771                 if (ret == 0)
772                         ret = err;
773         }
774 out:
775         return ret;
776 }
777 
778 /*
779  * Calculate the number of metadata blocks need to reserve
780  * to allocate a new block at @lblocks for non extent file based file
781  */
782 int ext4_ind_calc_metadata_amount(struct inode *inode, sector_t lblock)
783 {
784         struct ext4_inode_info *ei = EXT4_I(inode);
785         sector_t dind_mask = ~((sector_t)EXT4_ADDR_PER_BLOCK(inode->i_sb) - 1);
786         int blk_bits;
787 
788         if (lblock < EXT4_NDIR_BLOCKS)
789                 return 0;
790 
791         lblock -= EXT4_NDIR_BLOCKS;
792 
793         if (ei->i_da_metadata_calc_len &&
794             (lblock & dind_mask) == ei->i_da_metadata_calc_last_lblock) {
795                 ei->i_da_metadata_calc_len++;
796                 return 0;
797         }
798         ei->i_da_metadata_calc_last_lblock = lblock & dind_mask;
799         ei->i_da_metadata_calc_len = 1;
800         blk_bits = order_base_2(lblock);
801         return (blk_bits / EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb)) + 1;
802 }
803 
804 /*
805  * Calculate number of indirect blocks touched by mapping @nrblocks logically
806  * contiguous blocks
807  */
808 int ext4_ind_trans_blocks(struct inode *inode, int nrblocks)
809 {
810         /*
811          * With N contiguous data blocks, we need at most
812          * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) + 1 indirect blocks,
813          * 2 dindirect blocks, and 1 tindirect block
814          */
815         return DIV_ROUND_UP(nrblocks, EXT4_ADDR_PER_BLOCK(inode->i_sb)) + 4;
816 }
817 
818 /*
819  * Truncate transactions can be complex and absolutely huge.  So we need to
820  * be able to restart the transaction at a conventient checkpoint to make
821  * sure we don't overflow the journal.
822  *
823  * Try to extend this transaction for the purposes of truncation.  If
824  * extend fails, we need to propagate the failure up and restart the
825  * transaction in the top-level truncate loop. --sct
826  *
827  * Returns 0 if we managed to create more room.  If we can't create more
828  * room, and the transaction must be restarted we return 1.
829  */
830 static int try_to_extend_transaction(handle_t *handle, struct inode *inode)
831 {
832         if (!ext4_handle_valid(handle))
833                 return 0;
834         if (ext4_handle_has_enough_credits(handle, EXT4_RESERVE_TRANS_BLOCKS+1))
835                 return 0;
836         if (!ext4_journal_extend(handle, ext4_blocks_for_truncate(inode)))
837                 return 0;
838         return 1;
839 }
840 
841 /*
842  * Probably it should be a library function... search for first non-zero word
843  * or memcmp with zero_page, whatever is better for particular architecture.
844  * Linus?
845  */
846 static inline int all_zeroes(__le32 *p, __le32 *q)
847 {
848         while (p < q)
849                 if (*p++)
850                         return 0;
851         return 1;
852 }
853 
854 /**
855  *      ext4_find_shared - find the indirect blocks for partial truncation.
856  *      @inode:   inode in question
857  *      @depth:   depth of the affected branch
858  *      @offsets: offsets of pointers in that branch (see ext4_block_to_path)
859  *      @chain:   place to store the pointers to partial indirect blocks
860  *      @top:     place to the (detached) top of branch
861  *
862  *      This is a helper function used by ext4_truncate().
863  *
864  *      When we do truncate() we may have to clean the ends of several
865  *      indirect blocks but leave the blocks themselves alive. Block is
866  *      partially truncated if some data below the new i_size is referred
867  *      from it (and it is on the path to the first completely truncated
868  *      data block, indeed).  We have to free the top of that path along
869  *      with everything to the right of the path. Since no allocation
870  *      past the truncation point is possible until ext4_truncate()
871  *      finishes, we may safely do the latter, but top of branch may
872  *      require special attention - pageout below the truncation point
873  *      might try to populate it.
874  *
875  *      We atomically detach the top of branch from the tree, store the
876  *      block number of its root in *@top, pointers to buffer_heads of
877  *      partially truncated blocks - in @chain[].bh and pointers to
878  *      their last elements that should not be removed - in
879  *      @chain[].p. Return value is the pointer to last filled element
880  *      of @chain.
881  *
882  *      The work left to caller to do the actual freeing of subtrees:
883  *              a) free the subtree starting from *@top
884  *              b) free the subtrees whose roots are stored in
885  *                      (@chain[i].p+1 .. end of @chain[i].bh->b_data)
886  *              c) free the subtrees growing from the inode past the @chain[0].
887  *                      (no partially truncated stuff there).  */
888 
889 static Indirect *ext4_find_shared(struct inode *inode, int depth,
890                                   ext4_lblk_t offsets[4], Indirect chain[4],
891                                   __le32 *top)
892 {
893         Indirect *partial, *p;
894         int k, err;
895 
896         *top = 0;
897         /* Make k index the deepest non-null offset + 1 */
898         for (k = depth; k > 1 && !offsets[k-1]; k--)
899                 ;
900         partial = ext4_get_branch(inode, k, offsets, chain, &err);
901         /* Writer: pointers */
902         if (!partial)
903                 partial = chain + k-1;
904         /*
905          * If the branch acquired continuation since we've looked at it -
906          * fine, it should all survive and (new) top doesn't belong to us.
907          */
908         if (!partial->key && *partial->p)
909                 /* Writer: end */
910                 goto no_top;
911         for (p = partial; (p > chain) && all_zeroes((__le32 *) p->bh->b_data, p->p); p--)
912                 ;
913         /*
914          * OK, we've found the last block that must survive. The rest of our
915          * branch should be detached before unlocking. However, if that rest
916          * of branch is all ours and does not grow immediately from the inode
917          * it's easier to cheat and just decrement partial->p.
918          */
919         if (p == chain + k - 1 && p > chain) {
920                 p->p--;
921         } else {
922                 *top = *p->p;
923                 /* Nope, don't do this in ext4.  Must leave the tree intact */
924 #if 0
925                 *p->p = 0;
926 #endif
927         }
928         /* Writer: end */
929 
930         while (partial > p) {
931                 brelse(partial->bh);
932                 partial--;
933         }
934 no_top:
935         return partial;
936 }
937 
938 /*
939  * Zero a number of block pointers in either an inode or an indirect block.
940  * If we restart the transaction we must again get write access to the
941  * indirect block for further modification.
942  *
943  * We release `count' blocks on disk, but (last - first) may be greater
944  * than `count' because there can be holes in there.
945  *
946  * Return 0 on success, 1 on invalid block range
947  * and < 0 on fatal error.
948  */
949 static int ext4_clear_blocks(handle_t *handle, struct inode *inode,
950                              struct buffer_head *bh,
951                              ext4_fsblk_t block_to_free,
952                              unsigned long count, __le32 *first,
953                              __le32 *last)
954 {
955         __le32 *p;
956         int     flags = EXT4_FREE_BLOCKS_VALIDATED;
957         int     err;
958 
959         if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
960                 flags |= EXT4_FREE_BLOCKS_FORGET | EXT4_FREE_BLOCKS_METADATA;
961         else if (ext4_should_journal_data(inode))
962                 flags |= EXT4_FREE_BLOCKS_FORGET;
963 
964         if (!ext4_data_block_valid(EXT4_SB(inode->i_sb), block_to_free,
965                                    count)) {
966                 EXT4_ERROR_INODE(inode, "attempt to clear invalid "
967                                  "blocks %llu len %lu",
968                                  (unsigned long long) block_to_free, count);
969                 return 1;
970         }
971 
972         if (try_to_extend_transaction(handle, inode)) {
973                 if (bh) {
974                         BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
975                         err = ext4_handle_dirty_metadata(handle, inode, bh);
976                         if (unlikely(err))
977                                 goto out_err;
978                 }
979                 err = ext4_mark_inode_dirty(handle, inode);
980                 if (unlikely(err))
981                         goto out_err;
982                 err = ext4_truncate_restart_trans(handle, inode,
983                                         ext4_blocks_for_truncate(inode));
984                 if (unlikely(err))
985                         goto out_err;
986                 if (bh) {
987                         BUFFER_TRACE(bh, "retaking write access");
988                         err = ext4_journal_get_write_access(handle, bh);
989                         if (unlikely(err))
990                                 goto out_err;
991                 }
992         }
993 
994         for (p = first; p < last; p++)
995                 *p = 0;
996 
997         ext4_free_blocks(handle, inode, NULL, block_to_free, count, flags);
998         return 0;
999 out_err:
1000         ext4_std_error(inode->i_sb, err);
1001         return err;
1002 }
1003 
1004 /**
1005  * ext4_free_data - free a list of data blocks
1006  * @handle:     handle for this transaction
1007  * @inode:      inode we are dealing with
1008  * @this_bh:    indirect buffer_head which contains *@first and *@last
1009  * @first:      array of block numbers
1010  * @last:       points immediately past the end of array
1011  *
1012  * We are freeing all blocks referred from that array (numbers are stored as
1013  * little-endian 32-bit) and updating @inode->i_blocks appropriately.
1014  *
1015  * We accumulate contiguous runs of blocks to free.  Conveniently, if these
1016  * blocks are contiguous then releasing them at one time will only affect one
1017  * or two bitmap blocks (+ group descriptor(s) and superblock) and we won't
1018  * actually use a lot of journal space.
1019  *
1020  * @this_bh will be %NULL if @first and @last point into the inode's direct
1021  * block pointers.
1022  */
1023 static void ext4_free_data(handle_t *handle, struct inode *inode,
1024                            struct buffer_head *this_bh,
1025                            __le32 *first, __le32 *last)
1026 {
1027         ext4_fsblk_t block_to_free = 0;    /* Starting block # of a run */
1028         unsigned long count = 0;            /* Number of blocks in the run */
1029         __le32 *block_to_free_p = NULL;     /* Pointer into inode/ind
1030                                                corresponding to
1031                                                block_to_free */
1032         ext4_fsblk_t nr;                    /* Current block # */
1033         __le32 *p;                          /* Pointer into inode/ind
1034                                                for current block */
1035         int err = 0;
1036 
1037         if (this_bh) {                          /* For indirect block */
1038                 BUFFER_TRACE(this_bh, "get_write_access");
1039                 err = ext4_journal_get_write_access(handle, this_bh);
1040                 /* Important: if we can't update the indirect pointers
1041                  * to the blocks, we can't free them. */
1042                 if (err)
1043                         return;
1044         }
1045 
1046         for (p = first; p < last; p++) {
1047                 nr = le32_to_cpu(*p);
1048                 if (nr) {
1049                         /* accumulate blocks to free if they're contiguous */
1050                         if (count == 0) {
1051                                 block_to_free = nr;
1052                                 block_to_free_p = p;
1053                                 count = 1;
1054                         } else if (nr == block_to_free + count) {
1055                                 count++;
1056                         } else {
1057                                 err = ext4_clear_blocks(handle, inode, this_bh,
1058                                                         block_to_free, count,
1059                                                         block_to_free_p, p);
1060                                 if (err)
1061                                         break;
1062                                 block_to_free = nr;
1063                                 block_to_free_p = p;
1064                                 count = 1;
1065                         }
1066                 }
1067         }
1068 
1069         if (!err && count > 0)
1070                 err = ext4_clear_blocks(handle, inode, this_bh, block_to_free,
1071                                         count, block_to_free_p, p);
1072         if (err < 0)
1073                 /* fatal error */
1074                 return;
1075 
1076         if (this_bh) {
1077                 BUFFER_TRACE(this_bh, "call ext4_handle_dirty_metadata");
1078 
1079                 /*
1080                  * The buffer head should have an attached journal head at this
1081                  * point. However, if the data is corrupted and an indirect
1082                  * block pointed to itself, it would have been detached when
1083                  * the block was cleared. Check for this instead of OOPSing.
1084                  */
1085                 if ((EXT4_JOURNAL(inode) == NULL) || bh2jh(this_bh))
1086                         ext4_handle_dirty_metadata(handle, inode, this_bh);
1087                 else
1088                         EXT4_ERROR_INODE(inode,
1089                                          "circular indirect block detected at "
1090                                          "block %llu",
1091                                 (unsigned long long) this_bh->b_blocknr);
1092         }
1093 }
1094 
1095 /**
1096  *      ext4_free_branches - free an array of branches
1097  *      @handle: JBD handle for this transaction
1098  *      @inode: inode we are dealing with
1099  *      @parent_bh: the buffer_head which contains *@first and *@last
1100  *      @first: array of block numbers
1101  *      @last:  pointer immediately past the end of array
1102  *      @depth: depth of the branches to free
1103  *
1104  *      We are freeing all blocks referred from these branches (numbers are
1105  *      stored as little-endian 32-bit) and updating @inode->i_blocks
1106  *      appropriately.
1107  */
1108 static void ext4_free_branches(handle_t *handle, struct inode *inode,
1109                                struct buffer_head *parent_bh,
1110                                __le32 *first, __le32 *last, int depth)
1111 {
1112         ext4_fsblk_t nr;
1113         __le32 *p;
1114 
1115         if (ext4_handle_is_aborted(handle))
1116                 return;
1117 
1118         if (depth--) {
1119                 struct buffer_head *bh;
1120                 int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1121                 p = last;
1122                 while (--p >= first) {
1123                         nr = le32_to_cpu(*p);
1124                         if (!nr)
1125                                 continue;               /* A hole */
1126 
1127                         if (!ext4_data_block_valid(EXT4_SB(inode->i_sb),
1128                                                    nr, 1)) {
1129                                 EXT4_ERROR_INODE(inode,
1130                                                  "invalid indirect mapped "
1131                                                  "block %lu (level %d)",
1132                                                  (unsigned long) nr, depth);
1133                                 break;
1134                         }
1135 
1136                         /* Go read the buffer for the next level down */
1137                         bh = sb_bread(inode->i_sb, nr);
1138 
1139                         /*
1140                          * A read failure? Report error and clear slot
1141                          * (should be rare).
1142                          */
1143                         if (!bh) {
1144                                 EXT4_ERROR_INODE_BLOCK(inode, nr,
1145                                                        "Read failure");
1146                                 continue;
1147                         }
1148 
1149                         /* This zaps the entire block.  Bottom up. */
1150                         BUFFER_TRACE(bh, "free child branches");
1151                         ext4_free_branches(handle, inode, bh,
1152                                         (__le32 *) bh->b_data,
1153                                         (__le32 *) bh->b_data + addr_per_block,
1154                                         depth);
1155                         brelse(bh);
1156 
1157                         /*
1158                          * Everything below this this pointer has been
1159                          * released.  Now let this top-of-subtree go.
1160                          *
1161                          * We want the freeing of this indirect block to be
1162                          * atomic in the journal with the updating of the
1163                          * bitmap block which owns it.  So make some room in
1164                          * the journal.
1165                          *
1166                          * We zero the parent pointer *after* freeing its
1167                          * pointee in the bitmaps, so if extend_transaction()
1168                          * for some reason fails to put the bitmap changes and
1169                          * the release into the same transaction, recovery
1170                          * will merely complain about releasing a free block,
1171                          * rather than leaking blocks.
1172                          */
1173                         if (ext4_handle_is_aborted(handle))
1174                                 return;
1175                         if (try_to_extend_transaction(handle, inode)) {
1176                                 ext4_mark_inode_dirty(handle, inode);
1177                                 ext4_truncate_restart_trans(handle, inode,
1178                                             ext4_blocks_for_truncate(inode));
1179                         }
1180 
1181                         /*
1182                          * The forget flag here is critical because if
1183                          * we are journaling (and not doing data
1184                          * journaling), we have to make sure a revoke
1185                          * record is written to prevent the journal
1186                          * replay from overwriting the (former)
1187                          * indirect block if it gets reallocated as a
1188                          * data block.  This must happen in the same
1189                          * transaction where the data blocks are
1190                          * actually freed.
1191                          */
1192                         ext4_free_blocks(handle, inode, NULL, nr, 1,
1193                                          EXT4_FREE_BLOCKS_METADATA|
1194                                          EXT4_FREE_BLOCKS_FORGET);
1195 
1196                         if (parent_bh) {
1197                                 /*
1198                                  * The block which we have just freed is
1199                                  * pointed to by an indirect block: journal it
1200                                  */
1201                                 BUFFER_TRACE(parent_bh, "get_write_access");
1202                                 if (!ext4_journal_get_write_access(handle,
1203                                                                    parent_bh)){
1204                                         *p = 0;
1205                                         BUFFER_TRACE(parent_bh,
1206                                         "call ext4_handle_dirty_metadata");
1207                                         ext4_handle_dirty_metadata(handle,
1208                                                                    inode,
1209                                                                    parent_bh);
1210                                 }
1211                         }
1212                 }
1213         } else {
1214                 /* We have reached the bottom of the tree. */
1215                 BUFFER_TRACE(parent_bh, "free data blocks");
1216                 ext4_free_data(handle, inode, parent_bh, first, last);
1217         }
1218 }
1219 
1220 void ext4_ind_truncate(handle_t *handle, struct inode *inode)
1221 {
1222         struct ext4_inode_info *ei = EXT4_I(inode);
1223         __le32 *i_data = ei->i_data;
1224         int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1225         ext4_lblk_t offsets[4];
1226         Indirect chain[4];
1227         Indirect *partial;
1228         __le32 nr = 0;
1229         int n = 0;
1230         ext4_lblk_t last_block, max_block;
1231         unsigned blocksize = inode->i_sb->s_blocksize;
1232 
1233         last_block = (inode->i_size + blocksize-1)
1234                                         >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
1235         max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
1236                                         >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
1237 
1238         if (last_block != max_block) {
1239                 n = ext4_block_to_path(inode, last_block, offsets, NULL);
1240                 if (n == 0)
1241                         return;
1242         }
1243 
1244         ext4_es_remove_extent(inode, last_block, EXT_MAX_BLOCKS - last_block);
1245 
1246         /*
1247          * The orphan list entry will now protect us from any crash which
1248          * occurs before the truncate completes, so it is now safe to propagate
1249          * the new, shorter inode size (held for now in i_size) into the
1250          * on-disk inode. We do this via i_disksize, which is the value which
1251          * ext4 *really* writes onto the disk inode.
1252          */
1253         ei->i_disksize = inode->i_size;
1254 
1255         if (last_block == max_block) {
1256                 /*
1257                  * It is unnecessary to free any data blocks if last_block is
1258                  * equal to the indirect block limit.
1259                  */
1260                 return;
1261         } else if (n == 1) {            /* direct blocks */
1262                 ext4_free_data(handle, inode, NULL, i_data+offsets[0],
1263                                i_data + EXT4_NDIR_BLOCKS);
1264                 goto do_indirects;
1265         }
1266 
1267         partial = ext4_find_shared(inode, n, offsets, chain, &nr);
1268         /* Kill the top of shared branch (not detached) */
1269         if (nr) {
1270                 if (partial == chain) {
1271                         /* Shared branch grows from the inode */
1272                         ext4_free_branches(handle, inode, NULL,
1273                                            &nr, &nr+1, (chain+n-1) - partial);
1274                         *partial->p = 0;
1275                         /*
1276                          * We mark the inode dirty prior to restart,
1277                          * and prior to stop.  No need for it here.
1278                          */
1279                 } else {
1280                         /* Shared branch grows from an indirect block */
1281                         BUFFER_TRACE(partial->bh, "get_write_access");
1282                         ext4_free_branches(handle, inode, partial->bh,
1283                                         partial->p,
1284                                         partial->p+1, (chain+n-1) - partial);
1285                 }
1286         }
1287         /* Clear the ends of indirect blocks on the shared branch */
1288         while (partial > chain) {
1289                 ext4_free_branches(handle, inode, partial->bh, partial->p + 1,
1290                                    (__le32*)partial->bh->b_data+addr_per_block,
1291                                    (chain+n-1) - partial);
1292                 BUFFER_TRACE(partial->bh, "call brelse");
1293                 brelse(partial->bh);
1294                 partial--;
1295         }
1296 do_indirects:
1297         /* Kill the remaining (whole) subtrees */
1298         switch (offsets[0]) {
1299         default:
1300                 nr = i_data[EXT4_IND_BLOCK];
1301                 if (nr) {
1302                         ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
1303                         i_data[EXT4_IND_BLOCK] = 0;
1304                 }
1305         case EXT4_IND_BLOCK:
1306                 nr = i_data[EXT4_DIND_BLOCK];
1307                 if (nr) {
1308                         ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 2);
1309                         i_data[EXT4_DIND_BLOCK] = 0;
1310                 }
1311         case EXT4_DIND_BLOCK:
1312                 nr = i_data[EXT4_TIND_BLOCK];
1313                 if (nr) {
1314                         ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
1315                         i_data[EXT4_TIND_BLOCK] = 0;
1316                 }
1317         case EXT4_TIND_BLOCK:
1318                 ;
1319         }
1320 }
1321 
1322 /**
1323  *      ext4_ind_remove_space - remove space from the range
1324  *      @handle: JBD handle for this transaction
1325  *      @inode: inode we are dealing with
1326  *      @start: First block to remove
1327  *      @end:   One block after the last block to remove (exclusive)
1328  *
1329  *      Free the blocks in the defined range (end is exclusive endpoint of
1330  *      range). This is used by ext4_punch_hole().
1331  */
1332 int ext4_ind_remove_space(handle_t *handle, struct inode *inode,
1333                           ext4_lblk_t start, ext4_lblk_t end)
1334 {
1335         struct ext4_inode_info *ei = EXT4_I(inode);
1336         __le32 *i_data = ei->i_data;
1337         int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1338         ext4_lblk_t offsets[4], offsets2[4];
1339         Indirect chain[4], chain2[4];
1340         Indirect *partial, *partial2;
1341         ext4_lblk_t max_block;
1342         __le32 nr = 0, nr2 = 0;
1343         int n = 0, n2 = 0;
1344         unsigned blocksize = inode->i_sb->s_blocksize;
1345 
1346         max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
1347                                         >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
1348         if (end >= max_block)
1349                 end = max_block;
1350         if ((start >= end) || (start > max_block))
1351                 return 0;
1352 
1353         n = ext4_block_to_path(inode, start, offsets, NULL);
1354         n2 = ext4_block_to_path(inode, end, offsets2, NULL);
1355 
1356         BUG_ON(n > n2);
1357 
1358         if ((n == 1) && (n == n2)) {
1359                 /* We're punching only within direct block range */
1360                 ext4_free_data(handle, inode, NULL, i_data + offsets[0],
1361                                i_data + offsets2[0]);
1362                 return 0;
1363         } else if (n2 > n) {
1364                 /*
1365                  * Start and end are on a different levels so we're going to
1366                  * free partial block at start, and partial block at end of
1367                  * the range. If there are some levels in between then
1368                  * do_indirects label will take care of that.
1369                  */
1370 
1371                 if (n == 1) {
1372                         /*
1373                          * Start is at the direct block level, free
1374                          * everything to the end of the level.
1375                          */
1376                         ext4_free_data(handle, inode, NULL, i_data + offsets[0],
1377                                        i_data + EXT4_NDIR_BLOCKS);
1378                         goto end_range;
1379                 }
1380 
1381 
1382                 partial = ext4_find_shared(inode, n, offsets, chain, &nr);
1383                 if (nr) {
1384                         if (partial == chain) {
1385                                 /* Shared branch grows from the inode */
1386                                 ext4_free_branches(handle, inode, NULL,
1387                                            &nr, &nr+1, (chain+n-1) - partial);
1388                                 *partial->p = 0;
1389                         } else {
1390                                 /* Shared branch grows from an indirect block */
1391                                 BUFFER_TRACE(partial->bh, "get_write_access");
1392                                 ext4_free_branches(handle, inode, partial->bh,
1393                                         partial->p,
1394                                         partial->p+1, (chain+n-1) - partial);
1395                         }
1396                 }
1397 
1398                 /*
1399                  * Clear the ends of indirect blocks on the shared branch
1400                  * at the start of the range
1401                  */
1402                 while (partial > chain) {
1403                         ext4_free_branches(handle, inode, partial->bh,
1404                                 partial->p + 1,
1405                                 (__le32 *)partial->bh->b_data+addr_per_block,
1406                                 (chain+n-1) - partial);
1407                         BUFFER_TRACE(partial->bh, "call brelse");
1408                         brelse(partial->bh);
1409                         partial--;
1410                 }
1411 
1412 end_range:
1413                 partial2 = ext4_find_shared(inode, n2, offsets2, chain2, &nr2);
1414                 if (nr2) {
1415                         if (partial2 == chain2) {
1416                                 /*
1417                                  * Remember, end is exclusive so here we're at
1418                                  * the start of the next level we're not going
1419                                  * to free. Everything was covered by the start
1420                                  * of the range.
1421                                  */
1422                                 goto do_indirects;
1423                         }
1424                 } else {
1425                         /*
1426                          * ext4_find_shared returns Indirect structure which
1427                          * points to the last element which should not be
1428                          * removed by truncate. But this is end of the range
1429                          * in punch_hole so we need to point to the next element
1430                          */
1431                         partial2->p++;
1432                 }
1433 
1434                 /*
1435                  * Clear the ends of indirect blocks on the shared branch
1436                  * at the end of the range
1437                  */
1438                 while (partial2 > chain2) {
1439                         ext4_free_branches(handle, inode, partial2->bh,
1440                                            (__le32 *)partial2->bh->b_data,
1441                                            partial2->p,
1442                                            (chain2+n2-1) - partial2);
1443                         BUFFER_TRACE(partial2->bh, "call brelse");
1444                         brelse(partial2->bh);
1445                         partial2--;
1446                 }
1447                 goto do_indirects;
1448         }
1449 
1450         /* Punch happened within the same level (n == n2) */
1451         partial = ext4_find_shared(inode, n, offsets, chain, &nr);
1452         partial2 = ext4_find_shared(inode, n2, offsets2, chain2, &nr2);
1453 
1454         /* Free top, but only if partial2 isn't its subtree. */
1455         if (nr) {
1456                 int level = min(partial - chain, partial2 - chain2);
1457                 int i;
1458                 int subtree = 1;
1459 
1460                 for (i = 0; i <= level; i++) {
1461                         if (offsets[i] != offsets2[i]) {
1462                                 subtree = 0;
1463                                 break;
1464                         }
1465                 }
1466 
1467                 if (!subtree) {
1468                         if (partial == chain) {
1469                                 /* Shared branch grows from the inode */
1470                                 ext4_free_branches(handle, inode, NULL,
1471                                                    &nr, &nr+1,
1472                                                    (chain+n-1) - partial);
1473                                 *partial->p = 0;
1474                         } else {
1475                                 /* Shared branch grows from an indirect block */
1476                                 BUFFER_TRACE(partial->bh, "get_write_access");
1477                                 ext4_free_branches(handle, inode, partial->bh,
1478                                                    partial->p,
1479                                                    partial->p+1,
1480                                                    (chain+n-1) - partial);
1481                         }
1482                 }
1483         }
1484 
1485         if (!nr2) {
1486                 /*
1487                  * ext4_find_shared returns Indirect structure which
1488                  * points to the last element which should not be
1489                  * removed by truncate. But this is end of the range
1490                  * in punch_hole so we need to point to the next element
1491                  */
1492                 partial2->p++;
1493         }
1494 
1495         while (partial > chain || partial2 > chain2) {
1496                 int depth = (chain+n-1) - partial;
1497                 int depth2 = (chain2+n2-1) - partial2;
1498 
1499                 if (partial > chain && partial2 > chain2 &&
1500                     partial->bh->b_blocknr == partial2->bh->b_blocknr) {
1501                         /*
1502                          * We've converged on the same block. Clear the range,
1503                          * then we're done.
1504                          */
1505                         ext4_free_branches(handle, inode, partial->bh,
1506                                            partial->p + 1,
1507                                            partial2->p,
1508                                            (chain+n-1) - partial);
1509                         BUFFER_TRACE(partial->bh, "call brelse");
1510                         brelse(partial->bh);
1511                         BUFFER_TRACE(partial2->bh, "call brelse");
1512                         brelse(partial2->bh);
1513                         return 0;
1514                 }
1515 
1516                 /*
1517                  * The start and end partial branches may not be at the same
1518                  * level even though the punch happened within one level. So, we
1519                  * give them a chance to arrive at the same level, then walk
1520                  * them in step with each other until we converge on the same
1521                  * block.
1522                  */
1523                 if (partial > chain && depth <= depth2) {
1524                         ext4_free_branches(handle, inode, partial->bh,
1525                                            partial->p + 1,
1526                                            (__le32 *)partial->bh->b_data+addr_per_block,
1527                                            (chain+n-1) - partial);
1528                         BUFFER_TRACE(partial->bh, "call brelse");
1529                         brelse(partial->bh);
1530                         partial--;
1531                 }
1532                 if (partial2 > chain2 && depth2 <= depth) {
1533                         ext4_free_branches(handle, inode, partial2->bh,
1534                                            (__le32 *)partial2->bh->b_data,
1535                                            partial2->p,
1536                                            (chain2+n2-1) - partial2);
1537                         BUFFER_TRACE(partial2->bh, "call brelse");
1538                         brelse(partial2->bh);
1539                         partial2--;
1540                 }
1541         }
1542         return 0;
1543 
1544 do_indirects:
1545         /* Kill the remaining (whole) subtrees */
1546         switch (offsets[0]) {
1547         default:
1548                 if (++n >= n2)
1549                         return 0;
1550                 nr = i_data[EXT4_IND_BLOCK];
1551                 if (nr) {
1552                         ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
1553                         i_data[EXT4_IND_BLOCK] = 0;
1554                 }
1555         case EXT4_IND_BLOCK:
1556                 if (++n >= n2)
1557                         return 0;
1558                 nr = i_data[EXT4_DIND_BLOCK];
1559                 if (nr) {
1560                         ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 2);
1561                         i_data[EXT4_DIND_BLOCK] = 0;
1562                 }
1563         case EXT4_DIND_BLOCK:
1564                 if (++n >= n2)
1565                         return 0;
1566                 nr = i_data[EXT4_TIND_BLOCK];
1567                 if (nr) {
1568                         ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
1569                         i_data[EXT4_TIND_BLOCK] = 0;
1570                 }
1571         case EXT4_TIND_BLOCK:
1572                 ;
1573         }
1574         return 0;
1575 }
1576 

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