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Amir Goldsteindae1e522011-06-27 19:40:50 -04001/*
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
29typedef struct {
30 __le32 *p;
31 __le32 key;
32 struct buffer_head *bh;
33} Indirect;
34
35static 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
72static 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 */
142static 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
179failure:
180 *err = -EIO;
181no_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 */
205static 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;
Amir Goldsteindae1e522011-06-27 19:40:50 -0400210
211 /* Try to find previous block */
212 for (p = ind->p - 1; p >= start; p--) {
213 if (*p)
214 return le32_to_cpu(*p);
215 }
216
217 /* No such thing, so let's try location of indirect block */
218 if (ind->bh)
219 return ind->bh->b_blocknr;
220
221 /*
222 * It is going to be referred to from the inode itself? OK, just put it
223 * into the same cylinder group then.
224 */
Eric Sandeenf86186b2011-06-28 10:01:31 -0400225 return ext4_inode_to_goal_block(inode);
Amir Goldsteindae1e522011-06-27 19:40:50 -0400226}
227
228/**
229 * ext4_find_goal - find a preferred place for allocation.
230 * @inode: owner
231 * @block: block we want
232 * @partial: pointer to the last triple within a chain
233 *
234 * Normally this function find the preferred place for block allocation,
235 * returns it.
236 * Because this is only used for non-extent files, we limit the block nr
237 * to 32 bits.
238 */
239static ext4_fsblk_t ext4_find_goal(struct inode *inode, ext4_lblk_t block,
240 Indirect *partial)
241{
242 ext4_fsblk_t goal;
243
244 /*
245 * XXX need to get goal block from mballoc's data structures
246 */
247
248 goal = ext4_find_near(inode, partial);
249 goal = goal & EXT4_MAX_BLOCK_FILE_PHYS;
250 return goal;
251}
252
253/**
254 * ext4_blks_to_allocate - Look up the block map and count the number
255 * of direct blocks need to be allocated for the given branch.
256 *
257 * @branch: chain of indirect blocks
258 * @k: number of blocks need for indirect blocks
259 * @blks: number of data blocks to be mapped.
260 * @blocks_to_boundary: the offset in the indirect block
261 *
262 * return the total number of blocks to be allocate, including the
263 * direct and indirect blocks.
264 */
265static int ext4_blks_to_allocate(Indirect *branch, int k, unsigned int blks,
266 int blocks_to_boundary)
267{
268 unsigned int count = 0;
269
270 /*
271 * Simple case, [t,d]Indirect block(s) has not allocated yet
272 * then it's clear blocks on that path have not allocated
273 */
274 if (k > 0) {
275 /* right now we don't handle cross boundary allocation */
276 if (blks < blocks_to_boundary + 1)
277 count += blks;
278 else
279 count += blocks_to_boundary + 1;
280 return count;
281 }
282
283 count++;
284 while (count < blks && count <= blocks_to_boundary &&
285 le32_to_cpu(*(branch[0].p + count)) == 0) {
286 count++;
287 }
288 return count;
289}
290
291/**
292 * ext4_alloc_blocks: multiple allocate blocks needed for a branch
293 * @handle: handle for this transaction
294 * @inode: inode which needs allocated blocks
295 * @iblock: the logical block to start allocated at
296 * @goal: preferred physical block of allocation
297 * @indirect_blks: the number of blocks need to allocate for indirect
298 * blocks
299 * @blks: number of desired blocks
300 * @new_blocks: on return it will store the new block numbers for
301 * the indirect blocks(if needed) and the first direct block,
302 * @err: on return it will store the error code
303 *
304 * This function will return the number of blocks allocated as
305 * requested by the passed-in parameters.
306 */
307static int ext4_alloc_blocks(handle_t *handle, struct inode *inode,
308 ext4_lblk_t iblock, ext4_fsblk_t goal,
309 int indirect_blks, int blks,
310 ext4_fsblk_t new_blocks[4], int *err)
311{
312 struct ext4_allocation_request ar;
313 int target, i;
314 unsigned long count = 0, blk_allocated = 0;
315 int index = 0;
316 ext4_fsblk_t current_block = 0;
317 int ret = 0;
318
319 /*
320 * Here we try to allocate the requested multiple blocks at once,
321 * on a best-effort basis.
322 * To build a branch, we should allocate blocks for
323 * the indirect blocks(if not allocated yet), and at least
324 * the first direct block of this branch. That's the
325 * minimum number of blocks need to allocate(required)
326 */
327 /* first we try to allocate the indirect blocks */
328 target = indirect_blks;
329 while (target > 0) {
330 count = target;
331 /* allocating blocks for indirect blocks and direct blocks */
332 current_block = ext4_new_meta_blocks(handle, inode, goal,
333 0, &count, err);
334 if (*err)
335 goto failed_out;
336
337 if (unlikely(current_block + count > EXT4_MAX_BLOCK_FILE_PHYS)) {
338 EXT4_ERROR_INODE(inode,
339 "current_block %llu + count %lu > %d!",
340 current_block, count,
341 EXT4_MAX_BLOCK_FILE_PHYS);
342 *err = -EIO;
343 goto failed_out;
344 }
345
346 target -= count;
347 /* allocate blocks for indirect blocks */
348 while (index < indirect_blks && count) {
349 new_blocks[index++] = current_block++;
350 count--;
351 }
352 if (count > 0) {
353 /*
354 * save the new block number
355 * for the first direct block
356 */
357 new_blocks[index] = current_block;
358 printk(KERN_INFO "%s returned more blocks than "
359 "requested\n", __func__);
360 WARN_ON(1);
361 break;
362 }
363 }
364
365 target = blks - count ;
366 blk_allocated = count;
367 if (!target)
368 goto allocated;
369 /* Now allocate data blocks */
370 memset(&ar, 0, sizeof(ar));
371 ar.inode = inode;
372 ar.goal = goal;
373 ar.len = target;
374 ar.logical = iblock;
375 if (S_ISREG(inode->i_mode))
376 /* enable in-core preallocation only for regular files */
377 ar.flags = EXT4_MB_HINT_DATA;
378
379 current_block = ext4_mb_new_blocks(handle, &ar, err);
380 if (unlikely(current_block + ar.len > EXT4_MAX_BLOCK_FILE_PHYS)) {
381 EXT4_ERROR_INODE(inode,
382 "current_block %llu + ar.len %d > %d!",
383 current_block, ar.len,
384 EXT4_MAX_BLOCK_FILE_PHYS);
385 *err = -EIO;
386 goto failed_out;
387 }
388
389 if (*err && (target == blks)) {
390 /*
391 * if the allocation failed and we didn't allocate
392 * any blocks before
393 */
394 goto failed_out;
395 }
396 if (!*err) {
397 if (target == blks) {
398 /*
399 * save the new block number
400 * for the first direct block
401 */
402 new_blocks[index] = current_block;
403 }
404 blk_allocated += ar.len;
405 }
406allocated:
407 /* total number of blocks allocated for direct blocks */
408 ret = blk_allocated;
409 *err = 0;
410 return ret;
411failed_out:
412 for (i = 0; i < index; i++)
413 ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1, 0);
414 return ret;
415}
416
417/**
418 * ext4_alloc_branch - allocate and set up a chain of blocks.
419 * @handle: handle for this transaction
420 * @inode: owner
421 * @indirect_blks: number of allocated indirect blocks
422 * @blks: number of allocated direct blocks
423 * @goal: preferred place for allocation
424 * @offsets: offsets (in the blocks) to store the pointers to next.
425 * @branch: place to store the chain in.
426 *
427 * This function allocates blocks, zeroes out all but the last one,
428 * links them into chain and (if we are synchronous) writes them to disk.
429 * In other words, it prepares a branch that can be spliced onto the
430 * inode. It stores the information about that chain in the branch[], in
431 * the same format as ext4_get_branch() would do. We are calling it after
432 * we had read the existing part of chain and partial points to the last
433 * triple of that (one with zero ->key). Upon the exit we have the same
434 * picture as after the successful ext4_get_block(), except that in one
435 * place chain is disconnected - *branch->p is still zero (we did not
436 * set the last link), but branch->key contains the number that should
437 * be placed into *branch->p to fill that gap.
438 *
439 * If allocation fails we free all blocks we've allocated (and forget
440 * their buffer_heads) and return the error value the from failed
441 * ext4_alloc_block() (normally -ENOSPC). Otherwise we set the chain
442 * as described above and return 0.
443 */
444static int ext4_alloc_branch(handle_t *handle, struct inode *inode,
445 ext4_lblk_t iblock, int indirect_blks,
446 int *blks, ext4_fsblk_t goal,
447 ext4_lblk_t *offsets, Indirect *branch)
448{
449 int blocksize = inode->i_sb->s_blocksize;
450 int i, n = 0;
451 int err = 0;
452 struct buffer_head *bh;
453 int num;
454 ext4_fsblk_t new_blocks[4];
455 ext4_fsblk_t current_block;
456
457 num = ext4_alloc_blocks(handle, inode, iblock, goal, indirect_blks,
458 *blks, new_blocks, &err);
459 if (err)
460 return err;
461
462 branch[0].key = cpu_to_le32(new_blocks[0]);
463 /*
464 * metadata blocks and data blocks are allocated.
465 */
466 for (n = 1; n <= indirect_blks; n++) {
467 /*
468 * Get buffer_head for parent block, zero it out
469 * and set the pointer to new one, then send
470 * parent to disk.
471 */
472 bh = sb_getblk(inode->i_sb, new_blocks[n-1]);
473 if (unlikely(!bh)) {
474 err = -EIO;
475 goto failed;
476 }
477
478 branch[n].bh = bh;
479 lock_buffer(bh);
480 BUFFER_TRACE(bh, "call get_create_access");
481 err = ext4_journal_get_create_access(handle, bh);
482 if (err) {
483 /* Don't brelse(bh) here; it's done in
484 * ext4_journal_forget() below */
485 unlock_buffer(bh);
486 goto failed;
487 }
488
489 memset(bh->b_data, 0, blocksize);
490 branch[n].p = (__le32 *) bh->b_data + offsets[n];
491 branch[n].key = cpu_to_le32(new_blocks[n]);
492 *branch[n].p = branch[n].key;
493 if (n == indirect_blks) {
494 current_block = new_blocks[n];
495 /*
496 * End of chain, update the last new metablock of
497 * the chain to point to the new allocated
498 * data blocks numbers
499 */
500 for (i = 1; i < num; i++)
501 *(branch[n].p + i) = cpu_to_le32(++current_block);
502 }
503 BUFFER_TRACE(bh, "marking uptodate");
504 set_buffer_uptodate(bh);
505 unlock_buffer(bh);
506
507 BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
508 err = ext4_handle_dirty_metadata(handle, inode, bh);
509 if (err)
510 goto failed;
511 }
512 *blks = num;
513 return err;
514failed:
515 /* Allocation failed, free what we already allocated */
516 ext4_free_blocks(handle, inode, NULL, new_blocks[0], 1, 0);
517 for (i = 1; i <= n ; i++) {
518 /*
519 * branch[i].bh is newly allocated, so there is no
520 * need to revoke the block, which is why we don't
521 * need to set EXT4_FREE_BLOCKS_METADATA.
522 */
523 ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1,
524 EXT4_FREE_BLOCKS_FORGET);
525 }
526 for (i = n+1; i < indirect_blks; i++)
527 ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1, 0);
528
529 ext4_free_blocks(handle, inode, NULL, new_blocks[i], num, 0);
530
531 return err;
532}
533
534/**
535 * ext4_splice_branch - splice the allocated branch onto inode.
536 * @handle: handle for this transaction
537 * @inode: owner
538 * @block: (logical) number of block we are adding
539 * @chain: chain of indirect blocks (with a missing link - see
540 * ext4_alloc_branch)
541 * @where: location of missing link
542 * @num: number of indirect blocks we are adding
543 * @blks: number of direct blocks we are adding
544 *
545 * This function fills the missing link and does all housekeeping needed in
546 * inode (->i_blocks, etc.). In case of success we end up with the full
547 * chain to new block and return 0.
548 */
549static int ext4_splice_branch(handle_t *handle, struct inode *inode,
550 ext4_lblk_t block, Indirect *where, int num,
551 int blks)
552{
553 int i;
554 int err = 0;
555 ext4_fsblk_t current_block;
556
557 /*
558 * If we're splicing into a [td]indirect block (as opposed to the
559 * inode) then we need to get write access to the [td]indirect block
560 * before the splice.
561 */
562 if (where->bh) {
563 BUFFER_TRACE(where->bh, "get_write_access");
564 err = ext4_journal_get_write_access(handle, where->bh);
565 if (err)
566 goto err_out;
567 }
568 /* That's it */
569
570 *where->p = where->key;
571
572 /*
573 * Update the host buffer_head or inode to point to more just allocated
574 * direct blocks blocks
575 */
576 if (num == 0 && blks > 1) {
577 current_block = le32_to_cpu(where->key) + 1;
578 for (i = 1; i < blks; i++)
579 *(where->p + i) = cpu_to_le32(current_block++);
580 }
581
582 /* We are done with atomic stuff, now do the rest of housekeeping */
583 /* had we spliced it onto indirect block? */
584 if (where->bh) {
585 /*
586 * If we spliced it onto an indirect block, we haven't
587 * altered the inode. Note however that if it is being spliced
588 * onto an indirect block at the very end of the file (the
589 * file is growing) then we *will* alter the inode to reflect
590 * the new i_size. But that is not done here - it is done in
591 * generic_commit_write->__mark_inode_dirty->ext4_dirty_inode.
592 */
593 jbd_debug(5, "splicing indirect only\n");
594 BUFFER_TRACE(where->bh, "call ext4_handle_dirty_metadata");
595 err = ext4_handle_dirty_metadata(handle, inode, where->bh);
596 if (err)
597 goto err_out;
598 } else {
599 /*
600 * OK, we spliced it into the inode itself on a direct block.
601 */
602 ext4_mark_inode_dirty(handle, inode);
603 jbd_debug(5, "splicing direct\n");
604 }
605 return err;
606
607err_out:
608 for (i = 1; i <= num; i++) {
609 /*
610 * branch[i].bh is newly allocated, so there is no
611 * need to revoke the block, which is why we don't
612 * need to set EXT4_FREE_BLOCKS_METADATA.
613 */
614 ext4_free_blocks(handle, inode, where[i].bh, 0, 1,
615 EXT4_FREE_BLOCKS_FORGET);
616 }
617 ext4_free_blocks(handle, inode, NULL, le32_to_cpu(where[num].key),
618 blks, 0);
619
620 return err;
621}
622
623/*
624 * The ext4_ind_map_blocks() function handles non-extents inodes
625 * (i.e., using the traditional indirect/double-indirect i_blocks
626 * scheme) for ext4_map_blocks().
627 *
628 * Allocation strategy is simple: if we have to allocate something, we will
629 * have to go the whole way to leaf. So let's do it before attaching anything
630 * to tree, set linkage between the newborn blocks, write them if sync is
631 * required, recheck the path, free and repeat if check fails, otherwise
632 * set the last missing link (that will protect us from any truncate-generated
633 * removals - all blocks on the path are immune now) and possibly force the
634 * write on the parent block.
635 * That has a nice additional property: no special recovery from the failed
636 * allocations is needed - we simply release blocks and do not touch anything
637 * reachable from inode.
638 *
639 * `handle' can be NULL if create == 0.
640 *
641 * return > 0, # of blocks mapped or allocated.
642 * return = 0, if plain lookup failed.
643 * return < 0, error case.
644 *
645 * The ext4_ind_get_blocks() function should be called with
646 * down_write(&EXT4_I(inode)->i_data_sem) if allocating filesystem
647 * blocks (i.e., flags has EXT4_GET_BLOCKS_CREATE set) or
648 * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system
649 * blocks.
650 */
651int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
652 struct ext4_map_blocks *map,
653 int flags)
654{
655 int err = -EIO;
656 ext4_lblk_t offsets[4];
657 Indirect chain[4];
658 Indirect *partial;
659 ext4_fsblk_t goal;
660 int indirect_blks;
661 int blocks_to_boundary = 0;
662 int depth;
663 int count = 0;
664 ext4_fsblk_t first_block = 0;
665
666 trace_ext4_ind_map_blocks_enter(inode, map->m_lblk, map->m_len, flags);
667 J_ASSERT(!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)));
668 J_ASSERT(handle != NULL || (flags & EXT4_GET_BLOCKS_CREATE) == 0);
669 depth = ext4_block_to_path(inode, map->m_lblk, offsets,
670 &blocks_to_boundary);
671
672 if (depth == 0)
673 goto out;
674
675 partial = ext4_get_branch(inode, depth, offsets, chain, &err);
676
677 /* Simplest case - block found, no allocation needed */
678 if (!partial) {
679 first_block = le32_to_cpu(chain[depth - 1].key);
680 count++;
681 /*map more blocks*/
682 while (count < map->m_len && count <= blocks_to_boundary) {
683 ext4_fsblk_t blk;
684
685 blk = le32_to_cpu(*(chain[depth-1].p + count));
686
687 if (blk == first_block + count)
688 count++;
689 else
690 break;
691 }
692 goto got_it;
693 }
694
695 /* Next simple case - plain lookup or failed read of indirect block */
696 if ((flags & EXT4_GET_BLOCKS_CREATE) == 0 || err == -EIO)
697 goto cleanup;
698
699 /*
700 * Okay, we need to do block allocation.
701 */
702 goal = ext4_find_goal(inode, map->m_lblk, partial);
703
704 /* the number of blocks need to allocate for [d,t]indirect blocks */
705 indirect_blks = (chain + depth) - partial - 1;
706
707 /*
708 * Next look up the indirect map to count the totoal number of
709 * direct blocks to allocate for this branch.
710 */
711 count = ext4_blks_to_allocate(partial, indirect_blks,
712 map->m_len, blocks_to_boundary);
713 /*
714 * Block out ext4_truncate while we alter the tree
715 */
716 err = ext4_alloc_branch(handle, inode, map->m_lblk, indirect_blks,
717 &count, goal,
718 offsets + (partial - chain), partial);
719
720 /*
721 * The ext4_splice_branch call will free and forget any buffers
722 * on the new chain if there is a failure, but that risks using
723 * up transaction credits, especially for bitmaps where the
724 * credits cannot be returned. Can we handle this somehow? We
725 * may need to return -EAGAIN upwards in the worst case. --sct
726 */
727 if (!err)
728 err = ext4_splice_branch(handle, inode, map->m_lblk,
729 partial, indirect_blks, count);
730 if (err)
731 goto cleanup;
732
733 map->m_flags |= EXT4_MAP_NEW;
734
735 ext4_update_inode_fsync_trans(handle, inode, 1);
736got_it:
737 map->m_flags |= EXT4_MAP_MAPPED;
738 map->m_pblk = le32_to_cpu(chain[depth-1].key);
739 map->m_len = count;
740 if (count > blocks_to_boundary)
741 map->m_flags |= EXT4_MAP_BOUNDARY;
742 err = count;
743 /* Clean up and exit */
744 partial = chain + depth - 1; /* the whole chain */
745cleanup:
746 while (partial > chain) {
747 BUFFER_TRACE(partial->bh, "call brelse");
748 brelse(partial->bh);
749 partial--;
750 }
751out:
752 trace_ext4_ind_map_blocks_exit(inode, map->m_lblk,
753 map->m_pblk, map->m_len, err);
754 return err;
755}
756
757/*
758 * O_DIRECT for ext3 (or indirect map) based files
759 *
760 * If the O_DIRECT write will extend the file then add this inode to the
761 * orphan list. So recovery will truncate it back to the original size
762 * if the machine crashes during the write.
763 *
764 * If the O_DIRECT write is intantiating holes inside i_size and the machine
765 * crashes then stale disk data _may_ be exposed inside the file. But current
766 * VFS code falls back into buffered path in that case so we are safe.
767 */
768ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb,
769 const struct iovec *iov, loff_t offset,
770 unsigned long nr_segs)
771{
772 struct file *file = iocb->ki_filp;
773 struct inode *inode = file->f_mapping->host;
774 struct ext4_inode_info *ei = EXT4_I(inode);
775 handle_t *handle;
776 ssize_t ret;
777 int orphan = 0;
778 size_t count = iov_length(iov, nr_segs);
779 int retries = 0;
780
781 if (rw == WRITE) {
782 loff_t final_size = offset + count;
783
784 if (final_size > inode->i_size) {
785 /* Credits for sb + inode write */
786 handle = ext4_journal_start(inode, 2);
787 if (IS_ERR(handle)) {
788 ret = PTR_ERR(handle);
789 goto out;
790 }
791 ret = ext4_orphan_add(handle, inode);
792 if (ret) {
793 ext4_journal_stop(handle);
794 goto out;
795 }
796 orphan = 1;
797 ei->i_disksize = inode->i_size;
798 ext4_journal_stop(handle);
799 }
800 }
801
802retry:
803 if (rw == READ && ext4_should_dioread_nolock(inode))
804 ret = __blockdev_direct_IO(rw, iocb, inode,
805 inode->i_sb->s_bdev, iov,
806 offset, nr_segs,
807 ext4_get_block, NULL, NULL, 0);
808 else {
Linus Torvalds60ad4462011-08-01 13:56:03 -1000809 ret = blockdev_direct_IO(rw, iocb, inode, iov,
810 offset, nr_segs, ext4_get_block);
Amir Goldsteindae1e522011-06-27 19:40:50 -0400811
812 if (unlikely((rw & WRITE) && ret < 0)) {
813 loff_t isize = i_size_read(inode);
814 loff_t end = offset + iov_length(iov, nr_segs);
815
816 if (end > isize)
817 ext4_truncate_failed_write(inode);
818 }
819 }
820 if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
821 goto retry;
822
823 if (orphan) {
824 int err;
825
826 /* Credits for sb + inode write */
827 handle = ext4_journal_start(inode, 2);
828 if (IS_ERR(handle)) {
829 /* This is really bad luck. We've written the data
830 * but cannot extend i_size. Bail out and pretend
831 * the write failed... */
832 ret = PTR_ERR(handle);
833 if (inode->i_nlink)
834 ext4_orphan_del(NULL, inode);
835
836 goto out;
837 }
838 if (inode->i_nlink)
839 ext4_orphan_del(handle, inode);
840 if (ret > 0) {
841 loff_t end = offset + ret;
842 if (end > inode->i_size) {
843 ei->i_disksize = end;
844 i_size_write(inode, end);
845 /*
846 * We're going to return a positive `ret'
847 * here due to non-zero-length I/O, so there's
848 * no way of reporting error returns from
849 * ext4_mark_inode_dirty() to userspace. So
850 * ignore it.
851 */
852 ext4_mark_inode_dirty(handle, inode);
853 }
854 }
855 err = ext4_journal_stop(handle);
856 if (ret == 0)
857 ret = err;
858 }
859out:
860 return ret;
861}
862
863/*
864 * Calculate the number of metadata blocks need to reserve
865 * to allocate a new block at @lblocks for non extent file based file
866 */
867int ext4_ind_calc_metadata_amount(struct inode *inode, sector_t lblock)
868{
869 struct ext4_inode_info *ei = EXT4_I(inode);
870 sector_t dind_mask = ~((sector_t)EXT4_ADDR_PER_BLOCK(inode->i_sb) - 1);
871 int blk_bits;
872
873 if (lblock < EXT4_NDIR_BLOCKS)
874 return 0;
875
876 lblock -= EXT4_NDIR_BLOCKS;
877
878 if (ei->i_da_metadata_calc_len &&
879 (lblock & dind_mask) == ei->i_da_metadata_calc_last_lblock) {
880 ei->i_da_metadata_calc_len++;
881 return 0;
882 }
883 ei->i_da_metadata_calc_last_lblock = lblock & dind_mask;
884 ei->i_da_metadata_calc_len = 1;
885 blk_bits = order_base_2(lblock);
886 return (blk_bits / EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb)) + 1;
887}
888
889int ext4_ind_trans_blocks(struct inode *inode, int nrblocks, int chunk)
890{
891 int indirects;
892
893 /* if nrblocks are contiguous */
894 if (chunk) {
895 /*
896 * With N contiguous data blocks, we need at most
897 * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) + 1 indirect blocks,
898 * 2 dindirect blocks, and 1 tindirect block
899 */
900 return DIV_ROUND_UP(nrblocks,
901 EXT4_ADDR_PER_BLOCK(inode->i_sb)) + 4;
902 }
903 /*
904 * if nrblocks are not contiguous, worse case, each block touch
905 * a indirect block, and each indirect block touch a double indirect
906 * block, plus a triple indirect block
907 */
908 indirects = nrblocks * 2 + 1;
909 return indirects;
910}
911
912/*
913 * Truncate transactions can be complex and absolutely huge. So we need to
914 * be able to restart the transaction at a conventient checkpoint to make
915 * sure we don't overflow the journal.
916 *
917 * start_transaction gets us a new handle for a truncate transaction,
918 * and extend_transaction tries to extend the existing one a bit. If
919 * extend fails, we need to propagate the failure up and restart the
920 * transaction in the top-level truncate loop. --sct
921 */
922static handle_t *start_transaction(struct inode *inode)
923{
924 handle_t *result;
925
926 result = ext4_journal_start(inode, ext4_blocks_for_truncate(inode));
927 if (!IS_ERR(result))
928 return result;
929
930 ext4_std_error(inode->i_sb, PTR_ERR(result));
931 return result;
932}
933
934/*
935 * Try to extend this transaction for the purposes of truncation.
936 *
937 * Returns 0 if we managed to create more room. If we can't create more
938 * room, and the transaction must be restarted we return 1.
939 */
940static int try_to_extend_transaction(handle_t *handle, struct inode *inode)
941{
942 if (!ext4_handle_valid(handle))
943 return 0;
944 if (ext4_handle_has_enough_credits(handle, EXT4_RESERVE_TRANS_BLOCKS+1))
945 return 0;
946 if (!ext4_journal_extend(handle, ext4_blocks_for_truncate(inode)))
947 return 0;
948 return 1;
949}
950
951/*
952 * Probably it should be a library function... search for first non-zero word
953 * or memcmp with zero_page, whatever is better for particular architecture.
954 * Linus?
955 */
956static inline int all_zeroes(__le32 *p, __le32 *q)
957{
958 while (p < q)
959 if (*p++)
960 return 0;
961 return 1;
962}
963
964/**
965 * ext4_find_shared - find the indirect blocks for partial truncation.
966 * @inode: inode in question
967 * @depth: depth of the affected branch
968 * @offsets: offsets of pointers in that branch (see ext4_block_to_path)
969 * @chain: place to store the pointers to partial indirect blocks
970 * @top: place to the (detached) top of branch
971 *
972 * This is a helper function used by ext4_truncate().
973 *
974 * When we do truncate() we may have to clean the ends of several
975 * indirect blocks but leave the blocks themselves alive. Block is
976 * partially truncated if some data below the new i_size is referred
977 * from it (and it is on the path to the first completely truncated
978 * data block, indeed). We have to free the top of that path along
979 * with everything to the right of the path. Since no allocation
980 * past the truncation point is possible until ext4_truncate()
981 * finishes, we may safely do the latter, but top of branch may
982 * require special attention - pageout below the truncation point
983 * might try to populate it.
984 *
985 * We atomically detach the top of branch from the tree, store the
986 * block number of its root in *@top, pointers to buffer_heads of
987 * partially truncated blocks - in @chain[].bh and pointers to
988 * their last elements that should not be removed - in
989 * @chain[].p. Return value is the pointer to last filled element
990 * of @chain.
991 *
992 * The work left to caller to do the actual freeing of subtrees:
993 * a) free the subtree starting from *@top
994 * b) free the subtrees whose roots are stored in
995 * (@chain[i].p+1 .. end of @chain[i].bh->b_data)
996 * c) free the subtrees growing from the inode past the @chain[0].
997 * (no partially truncated stuff there). */
998
999static Indirect *ext4_find_shared(struct inode *inode, int depth,
1000 ext4_lblk_t offsets[4], Indirect chain[4],
1001 __le32 *top)
1002{
1003 Indirect *partial, *p;
1004 int k, err;
1005
1006 *top = 0;
1007 /* Make k index the deepest non-null offset + 1 */
1008 for (k = depth; k > 1 && !offsets[k-1]; k--)
1009 ;
1010 partial = ext4_get_branch(inode, k, offsets, chain, &err);
1011 /* Writer: pointers */
1012 if (!partial)
1013 partial = chain + k-1;
1014 /*
1015 * If the branch acquired continuation since we've looked at it -
1016 * fine, it should all survive and (new) top doesn't belong to us.
1017 */
1018 if (!partial->key && *partial->p)
1019 /* Writer: end */
1020 goto no_top;
1021 for (p = partial; (p > chain) && all_zeroes((__le32 *) p->bh->b_data, p->p); p--)
1022 ;
1023 /*
1024 * OK, we've found the last block that must survive. The rest of our
1025 * branch should be detached before unlocking. However, if that rest
1026 * of branch is all ours and does not grow immediately from the inode
1027 * it's easier to cheat and just decrement partial->p.
1028 */
1029 if (p == chain + k - 1 && p > chain) {
1030 p->p--;
1031 } else {
1032 *top = *p->p;
1033 /* Nope, don't do this in ext4. Must leave the tree intact */
1034#if 0
1035 *p->p = 0;
1036#endif
1037 }
1038 /* Writer: end */
1039
1040 while (partial > p) {
1041 brelse(partial->bh);
1042 partial--;
1043 }
1044no_top:
1045 return partial;
1046}
1047
1048/*
1049 * Zero a number of block pointers in either an inode or an indirect block.
1050 * If we restart the transaction we must again get write access to the
1051 * indirect block for further modification.
1052 *
1053 * We release `count' blocks on disk, but (last - first) may be greater
1054 * than `count' because there can be holes in there.
1055 *
1056 * Return 0 on success, 1 on invalid block range
1057 * and < 0 on fatal error.
1058 */
1059static int ext4_clear_blocks(handle_t *handle, struct inode *inode,
1060 struct buffer_head *bh,
1061 ext4_fsblk_t block_to_free,
1062 unsigned long count, __le32 *first,
1063 __le32 *last)
1064{
1065 __le32 *p;
1066 int flags = EXT4_FREE_BLOCKS_FORGET | EXT4_FREE_BLOCKS_VALIDATED;
1067 int err;
1068
1069 if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
1070 flags |= EXT4_FREE_BLOCKS_METADATA;
1071
1072 if (!ext4_data_block_valid(EXT4_SB(inode->i_sb), block_to_free,
1073 count)) {
1074 EXT4_ERROR_INODE(inode, "attempt to clear invalid "
1075 "blocks %llu len %lu",
1076 (unsigned long long) block_to_free, count);
1077 return 1;
1078 }
1079
1080 if (try_to_extend_transaction(handle, inode)) {
1081 if (bh) {
1082 BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
1083 err = ext4_handle_dirty_metadata(handle, inode, bh);
1084 if (unlikely(err))
1085 goto out_err;
1086 }
1087 err = ext4_mark_inode_dirty(handle, inode);
1088 if (unlikely(err))
1089 goto out_err;
1090 err = ext4_truncate_restart_trans(handle, inode,
1091 ext4_blocks_for_truncate(inode));
1092 if (unlikely(err))
1093 goto out_err;
1094 if (bh) {
1095 BUFFER_TRACE(bh, "retaking write access");
1096 err = ext4_journal_get_write_access(handle, bh);
1097 if (unlikely(err))
1098 goto out_err;
1099 }
1100 }
1101
1102 for (p = first; p < last; p++)
1103 *p = 0;
1104
1105 ext4_free_blocks(handle, inode, NULL, block_to_free, count, flags);
1106 return 0;
1107out_err:
1108 ext4_std_error(inode->i_sb, err);
1109 return err;
1110}
1111
1112/**
1113 * ext4_free_data - free a list of data blocks
1114 * @handle: handle for this transaction
1115 * @inode: inode we are dealing with
1116 * @this_bh: indirect buffer_head which contains *@first and *@last
1117 * @first: array of block numbers
1118 * @last: points immediately past the end of array
1119 *
1120 * We are freeing all blocks referred from that array (numbers are stored as
1121 * little-endian 32-bit) and updating @inode->i_blocks appropriately.
1122 *
1123 * We accumulate contiguous runs of blocks to free. Conveniently, if these
1124 * blocks are contiguous then releasing them at one time will only affect one
1125 * or two bitmap blocks (+ group descriptor(s) and superblock) and we won't
1126 * actually use a lot of journal space.
1127 *
1128 * @this_bh will be %NULL if @first and @last point into the inode's direct
1129 * block pointers.
1130 */
1131static void ext4_free_data(handle_t *handle, struct inode *inode,
1132 struct buffer_head *this_bh,
1133 __le32 *first, __le32 *last)
1134{
1135 ext4_fsblk_t block_to_free = 0; /* Starting block # of a run */
1136 unsigned long count = 0; /* Number of blocks in the run */
1137 __le32 *block_to_free_p = NULL; /* Pointer into inode/ind
1138 corresponding to
1139 block_to_free */
1140 ext4_fsblk_t nr; /* Current block # */
1141 __le32 *p; /* Pointer into inode/ind
1142 for current block */
1143 int err = 0;
1144
1145 if (this_bh) { /* For indirect block */
1146 BUFFER_TRACE(this_bh, "get_write_access");
1147 err = ext4_journal_get_write_access(handle, this_bh);
1148 /* Important: if we can't update the indirect pointers
1149 * to the blocks, we can't free them. */
1150 if (err)
1151 return;
1152 }
1153
1154 for (p = first; p < last; p++) {
1155 nr = le32_to_cpu(*p);
1156 if (nr) {
1157 /* accumulate blocks to free if they're contiguous */
1158 if (count == 0) {
1159 block_to_free = nr;
1160 block_to_free_p = p;
1161 count = 1;
1162 } else if (nr == block_to_free + count) {
1163 count++;
1164 } else {
1165 err = ext4_clear_blocks(handle, inode, this_bh,
1166 block_to_free, count,
1167 block_to_free_p, p);
1168 if (err)
1169 break;
1170 block_to_free = nr;
1171 block_to_free_p = p;
1172 count = 1;
1173 }
1174 }
1175 }
1176
1177 if (!err && count > 0)
1178 err = ext4_clear_blocks(handle, inode, this_bh, block_to_free,
1179 count, block_to_free_p, p);
1180 if (err < 0)
1181 /* fatal error */
1182 return;
1183
1184 if (this_bh) {
1185 BUFFER_TRACE(this_bh, "call ext4_handle_dirty_metadata");
1186
1187 /*
1188 * The buffer head should have an attached journal head at this
1189 * point. However, if the data is corrupted and an indirect
1190 * block pointed to itself, it would have been detached when
1191 * the block was cleared. Check for this instead of OOPSing.
1192 */
1193 if ((EXT4_JOURNAL(inode) == NULL) || bh2jh(this_bh))
1194 ext4_handle_dirty_metadata(handle, inode, this_bh);
1195 else
1196 EXT4_ERROR_INODE(inode,
1197 "circular indirect block detected at "
1198 "block %llu",
1199 (unsigned long long) this_bh->b_blocknr);
1200 }
1201}
1202
1203/**
1204 * ext4_free_branches - free an array of branches
1205 * @handle: JBD handle for this transaction
1206 * @inode: inode we are dealing with
1207 * @parent_bh: the buffer_head which contains *@first and *@last
1208 * @first: array of block numbers
1209 * @last: pointer immediately past the end of array
1210 * @depth: depth of the branches to free
1211 *
1212 * We are freeing all blocks referred from these branches (numbers are
1213 * stored as little-endian 32-bit) and updating @inode->i_blocks
1214 * appropriately.
1215 */
1216static void ext4_free_branches(handle_t *handle, struct inode *inode,
1217 struct buffer_head *parent_bh,
1218 __le32 *first, __le32 *last, int depth)
1219{
1220 ext4_fsblk_t nr;
1221 __le32 *p;
1222
1223 if (ext4_handle_is_aborted(handle))
1224 return;
1225
1226 if (depth--) {
1227 struct buffer_head *bh;
1228 int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1229 p = last;
1230 while (--p >= first) {
1231 nr = le32_to_cpu(*p);
1232 if (!nr)
1233 continue; /* A hole */
1234
1235 if (!ext4_data_block_valid(EXT4_SB(inode->i_sb),
1236 nr, 1)) {
1237 EXT4_ERROR_INODE(inode,
1238 "invalid indirect mapped "
1239 "block %lu (level %d)",
1240 (unsigned long) nr, depth);
1241 break;
1242 }
1243
1244 /* Go read the buffer for the next level down */
1245 bh = sb_bread(inode->i_sb, nr);
1246
1247 /*
1248 * A read failure? Report error and clear slot
1249 * (should be rare).
1250 */
1251 if (!bh) {
1252 EXT4_ERROR_INODE_BLOCK(inode, nr,
1253 "Read failure");
1254 continue;
1255 }
1256
1257 /* This zaps the entire block. Bottom up. */
1258 BUFFER_TRACE(bh, "free child branches");
1259 ext4_free_branches(handle, inode, bh,
1260 (__le32 *) bh->b_data,
1261 (__le32 *) bh->b_data + addr_per_block,
1262 depth);
1263 brelse(bh);
1264
1265 /*
1266 * Everything below this this pointer has been
1267 * released. Now let this top-of-subtree go.
1268 *
1269 * We want the freeing of this indirect block to be
1270 * atomic in the journal with the updating of the
1271 * bitmap block which owns it. So make some room in
1272 * the journal.
1273 *
1274 * We zero the parent pointer *after* freeing its
1275 * pointee in the bitmaps, so if extend_transaction()
1276 * for some reason fails to put the bitmap changes and
1277 * the release into the same transaction, recovery
1278 * will merely complain about releasing a free block,
1279 * rather than leaking blocks.
1280 */
1281 if (ext4_handle_is_aborted(handle))
1282 return;
1283 if (try_to_extend_transaction(handle, inode)) {
1284 ext4_mark_inode_dirty(handle, inode);
1285 ext4_truncate_restart_trans(handle, inode,
1286 ext4_blocks_for_truncate(inode));
1287 }
1288
1289 /*
1290 * The forget flag here is critical because if
1291 * we are journaling (and not doing data
1292 * journaling), we have to make sure a revoke
1293 * record is written to prevent the journal
1294 * replay from overwriting the (former)
1295 * indirect block if it gets reallocated as a
1296 * data block. This must happen in the same
1297 * transaction where the data blocks are
1298 * actually freed.
1299 */
1300 ext4_free_blocks(handle, inode, NULL, nr, 1,
1301 EXT4_FREE_BLOCKS_METADATA|
1302 EXT4_FREE_BLOCKS_FORGET);
1303
1304 if (parent_bh) {
1305 /*
1306 * The block which we have just freed is
1307 * pointed to by an indirect block: journal it
1308 */
1309 BUFFER_TRACE(parent_bh, "get_write_access");
1310 if (!ext4_journal_get_write_access(handle,
1311 parent_bh)){
1312 *p = 0;
1313 BUFFER_TRACE(parent_bh,
1314 "call ext4_handle_dirty_metadata");
1315 ext4_handle_dirty_metadata(handle,
1316 inode,
1317 parent_bh);
1318 }
1319 }
1320 }
1321 } else {
1322 /* We have reached the bottom of the tree. */
1323 BUFFER_TRACE(parent_bh, "free data blocks");
1324 ext4_free_data(handle, inode, parent_bh, first, last);
1325 }
1326}
1327
1328void ext4_ind_truncate(struct inode *inode)
1329{
1330 handle_t *handle;
1331 struct ext4_inode_info *ei = EXT4_I(inode);
1332 __le32 *i_data = ei->i_data;
1333 int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1334 struct address_space *mapping = inode->i_mapping;
1335 ext4_lblk_t offsets[4];
1336 Indirect chain[4];
1337 Indirect *partial;
1338 __le32 nr = 0;
1339 int n = 0;
1340 ext4_lblk_t last_block, max_block;
1341 unsigned blocksize = inode->i_sb->s_blocksize;
1342
1343 handle = start_transaction(inode);
1344 if (IS_ERR(handle))
1345 return; /* AKPM: return what? */
1346
1347 last_block = (inode->i_size + blocksize-1)
1348 >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
1349 max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
1350 >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
1351
1352 if (inode->i_size & (blocksize - 1))
1353 if (ext4_block_truncate_page(handle, mapping, inode->i_size))
1354 goto out_stop;
1355
1356 if (last_block != max_block) {
1357 n = ext4_block_to_path(inode, last_block, offsets, NULL);
1358 if (n == 0)
1359 goto out_stop; /* error */
1360 }
1361
1362 /*
1363 * OK. This truncate is going to happen. We add the inode to the
1364 * orphan list, so that if this truncate spans multiple transactions,
1365 * and we crash, we will resume the truncate when the filesystem
1366 * recovers. It also marks the inode dirty, to catch the new size.
1367 *
1368 * Implication: the file must always be in a sane, consistent
1369 * truncatable state while each transaction commits.
1370 */
1371 if (ext4_orphan_add(handle, inode))
1372 goto out_stop;
1373
1374 /*
1375 * From here we block out all ext4_get_block() callers who want to
1376 * modify the block allocation tree.
1377 */
1378 down_write(&ei->i_data_sem);
1379
1380 ext4_discard_preallocations(inode);
1381
1382 /*
1383 * The orphan list entry will now protect us from any crash which
1384 * occurs before the truncate completes, so it is now safe to propagate
1385 * the new, shorter inode size (held for now in i_size) into the
1386 * on-disk inode. We do this via i_disksize, which is the value which
1387 * ext4 *really* writes onto the disk inode.
1388 */
1389 ei->i_disksize = inode->i_size;
1390
1391 if (last_block == max_block) {
1392 /*
1393 * It is unnecessary to free any data blocks if last_block is
1394 * equal to the indirect block limit.
1395 */
1396 goto out_unlock;
1397 } else if (n == 1) { /* direct blocks */
1398 ext4_free_data(handle, inode, NULL, i_data+offsets[0],
1399 i_data + EXT4_NDIR_BLOCKS);
1400 goto do_indirects;
1401 }
1402
1403 partial = ext4_find_shared(inode, n, offsets, chain, &nr);
1404 /* Kill the top of shared branch (not detached) */
1405 if (nr) {
1406 if (partial == chain) {
1407 /* Shared branch grows from the inode */
1408 ext4_free_branches(handle, inode, NULL,
1409 &nr, &nr+1, (chain+n-1) - partial);
1410 *partial->p = 0;
1411 /*
1412 * We mark the inode dirty prior to restart,
1413 * and prior to stop. No need for it here.
1414 */
1415 } else {
1416 /* Shared branch grows from an indirect block */
1417 BUFFER_TRACE(partial->bh, "get_write_access");
1418 ext4_free_branches(handle, inode, partial->bh,
1419 partial->p,
1420 partial->p+1, (chain+n-1) - partial);
1421 }
1422 }
1423 /* Clear the ends of indirect blocks on the shared branch */
1424 while (partial > chain) {
1425 ext4_free_branches(handle, inode, partial->bh, partial->p + 1,
1426 (__le32*)partial->bh->b_data+addr_per_block,
1427 (chain+n-1) - partial);
1428 BUFFER_TRACE(partial->bh, "call brelse");
1429 brelse(partial->bh);
1430 partial--;
1431 }
1432do_indirects:
1433 /* Kill the remaining (whole) subtrees */
1434 switch (offsets[0]) {
1435 default:
1436 nr = i_data[EXT4_IND_BLOCK];
1437 if (nr) {
1438 ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
1439 i_data[EXT4_IND_BLOCK] = 0;
1440 }
1441 case EXT4_IND_BLOCK:
1442 nr = i_data[EXT4_DIND_BLOCK];
1443 if (nr) {
1444 ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 2);
1445 i_data[EXT4_DIND_BLOCK] = 0;
1446 }
1447 case EXT4_DIND_BLOCK:
1448 nr = i_data[EXT4_TIND_BLOCK];
1449 if (nr) {
1450 ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
1451 i_data[EXT4_TIND_BLOCK] = 0;
1452 }
1453 case EXT4_TIND_BLOCK:
1454 ;
1455 }
1456
1457out_unlock:
1458 up_write(&ei->i_data_sem);
1459 inode->i_mtime = inode->i_ctime = ext4_current_time(inode);
1460 ext4_mark_inode_dirty(handle, inode);
1461
1462 /*
1463 * In a multi-transaction truncate, we only make the final transaction
1464 * synchronous
1465 */
1466 if (IS_SYNC(inode))
1467 ext4_handle_sync(handle);
1468out_stop:
1469 /*
1470 * If this was a simple ftruncate(), and the file will remain alive
1471 * then we need to clear up the orphan record which we created above.
1472 * However, if this was a real unlink then we were called by
1473 * ext4_delete_inode(), and we allow that function to clean up the
1474 * orphan info for us.
1475 */
1476 if (inode->i_nlink)
1477 ext4_orphan_del(handle, inode);
1478
1479 ext4_journal_stop(handle);
1480 trace_ext4_truncate_exit(inode);
1481}
1482