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TOMOYO Linux Cross Reference
Linux/fs/btrfs/extent_io.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 
  3 #include <linux/bitops.h>
  4 #include <linux/slab.h>
  5 #include <linux/bio.h>
  6 #include <linux/mm.h>
  7 #include <linux/pagemap.h>
  8 #include <linux/page-flags.h>
  9 #include <linux/spinlock.h>
 10 #include <linux/blkdev.h>
 11 #include <linux/swap.h>
 12 #include <linux/writeback.h>
 13 #include <linux/pagevec.h>
 14 #include <linux/prefetch.h>
 15 #include <linux/cleancache.h>
 16 #include "extent_io.h"
 17 #include "extent_map.h"
 18 #include "ctree.h"
 19 #include "btrfs_inode.h"
 20 #include "volumes.h"
 21 #include "check-integrity.h"
 22 #include "locking.h"
 23 #include "rcu-string.h"
 24 #include "backref.h"
 25 #include "disk-io.h"
 26 
 27 static struct kmem_cache *extent_state_cache;
 28 static struct kmem_cache *extent_buffer_cache;
 29 static struct bio_set *btrfs_bioset;
 30 
 31 static inline bool extent_state_in_tree(const struct extent_state *state)
 32 {
 33         return !RB_EMPTY_NODE(&state->rb_node);
 34 }
 35 
 36 #ifdef CONFIG_BTRFS_DEBUG
 37 static LIST_HEAD(buffers);
 38 static LIST_HEAD(states);
 39 
 40 static DEFINE_SPINLOCK(leak_lock);
 41 
 42 static inline
 43 void btrfs_leak_debug_add(struct list_head *new, struct list_head *head)
 44 {
 45         unsigned long flags;
 46 
 47         spin_lock_irqsave(&leak_lock, flags);
 48         list_add(new, head);
 49         spin_unlock_irqrestore(&leak_lock, flags);
 50 }
 51 
 52 static inline
 53 void btrfs_leak_debug_del(struct list_head *entry)
 54 {
 55         unsigned long flags;
 56 
 57         spin_lock_irqsave(&leak_lock, flags);
 58         list_del(entry);
 59         spin_unlock_irqrestore(&leak_lock, flags);
 60 }
 61 
 62 static inline
 63 void btrfs_leak_debug_check(void)
 64 {
 65         struct extent_state *state;
 66         struct extent_buffer *eb;
 67 
 68         while (!list_empty(&states)) {
 69                 state = list_entry(states.next, struct extent_state, leak_list);
 70                 pr_err("BTRFS: state leak: start %llu end %llu state %u in tree %d refs %d\n",
 71                        state->start, state->end, state->state,
 72                        extent_state_in_tree(state),
 73                        refcount_read(&state->refs));
 74                 list_del(&state->leak_list);
 75                 kmem_cache_free(extent_state_cache, state);
 76         }
 77 
 78         while (!list_empty(&buffers)) {
 79                 eb = list_entry(buffers.next, struct extent_buffer, leak_list);
 80                 pr_err("BTRFS: buffer leak start %llu len %lu refs %d bflags %lu\n",
 81                        eb->start, eb->len, atomic_read(&eb->refs), eb->bflags);
 82                 list_del(&eb->leak_list);
 83                 kmem_cache_free(extent_buffer_cache, eb);
 84         }
 85 }
 86 
 87 #define btrfs_debug_check_extent_io_range(tree, start, end)             \
 88         __btrfs_debug_check_extent_io_range(__func__, (tree), (start), (end))
 89 static inline void __btrfs_debug_check_extent_io_range(const char *caller,
 90                 struct extent_io_tree *tree, u64 start, u64 end)
 91 {
 92         if (tree->ops && tree->ops->check_extent_io_range)
 93                 tree->ops->check_extent_io_range(tree->private_data, caller,
 94                                                  start, end);
 95 }
 96 #else
 97 #define btrfs_leak_debug_add(new, head) do {} while (0)
 98 #define btrfs_leak_debug_del(entry)     do {} while (0)
 99 #define btrfs_leak_debug_check()        do {} while (0)
100 #define btrfs_debug_check_extent_io_range(c, s, e)      do {} while (0)
101 #endif
102 
103 #define BUFFER_LRU_MAX 64
104 
105 struct tree_entry {
106         u64 start;
107         u64 end;
108         struct rb_node rb_node;
109 };
110 
111 struct extent_page_data {
112         struct bio *bio;
113         struct extent_io_tree *tree;
114         /* tells writepage not to lock the state bits for this range
115          * it still does the unlocking
116          */
117         unsigned int extent_locked:1;
118 
119         /* tells the submit_bio code to use REQ_SYNC */
120         unsigned int sync_io:1;
121 };
122 
123 static int add_extent_changeset(struct extent_state *state, unsigned bits,
124                                  struct extent_changeset *changeset,
125                                  int set)
126 {
127         int ret;
128 
129         if (!changeset)
130                 return 0;
131         if (set && (state->state & bits) == bits)
132                 return 0;
133         if (!set && (state->state & bits) == 0)
134                 return 0;
135         changeset->bytes_changed += state->end - state->start + 1;
136         ret = ulist_add(&changeset->range_changed, state->start, state->end,
137                         GFP_ATOMIC);
138         return ret;
139 }
140 
141 static void flush_write_bio(struct extent_page_data *epd);
142 
143 static inline struct btrfs_fs_info *
144 tree_fs_info(struct extent_io_tree *tree)
145 {
146         if (tree->ops)
147                 return tree->ops->tree_fs_info(tree->private_data);
148         return NULL;
149 }
150 
151 int __init extent_io_init(void)
152 {
153         extent_state_cache = kmem_cache_create("btrfs_extent_state",
154                         sizeof(struct extent_state), 0,
155                         SLAB_MEM_SPREAD, NULL);
156         if (!extent_state_cache)
157                 return -ENOMEM;
158 
159         extent_buffer_cache = kmem_cache_create("btrfs_extent_buffer",
160                         sizeof(struct extent_buffer), 0,
161                         SLAB_MEM_SPREAD, NULL);
162         if (!extent_buffer_cache)
163                 goto free_state_cache;
164 
165         btrfs_bioset = bioset_create(BIO_POOL_SIZE,
166                                      offsetof(struct btrfs_io_bio, bio),
167                                      BIOSET_NEED_BVECS);
168         if (!btrfs_bioset)
169                 goto free_buffer_cache;
170 
171         if (bioset_integrity_create(btrfs_bioset, BIO_POOL_SIZE))
172                 goto free_bioset;
173 
174         return 0;
175 
176 free_bioset:
177         bioset_free(btrfs_bioset);
178         btrfs_bioset = NULL;
179 
180 free_buffer_cache:
181         kmem_cache_destroy(extent_buffer_cache);
182         extent_buffer_cache = NULL;
183 
184 free_state_cache:
185         kmem_cache_destroy(extent_state_cache);
186         extent_state_cache = NULL;
187         return -ENOMEM;
188 }
189 
190 void __cold extent_io_exit(void)
191 {
192         btrfs_leak_debug_check();
193 
194         /*
195          * Make sure all delayed rcu free are flushed before we
196          * destroy caches.
197          */
198         rcu_barrier();
199         kmem_cache_destroy(extent_state_cache);
200         kmem_cache_destroy(extent_buffer_cache);
201         if (btrfs_bioset)
202                 bioset_free(btrfs_bioset);
203 }
204 
205 void extent_io_tree_init(struct extent_io_tree *tree,
206                          void *private_data)
207 {
208         tree->state = RB_ROOT;
209         tree->ops = NULL;
210         tree->dirty_bytes = 0;
211         spin_lock_init(&tree->lock);
212         tree->private_data = private_data;
213 }
214 
215 static struct extent_state *alloc_extent_state(gfp_t mask)
216 {
217         struct extent_state *state;
218 
219         /*
220          * The given mask might be not appropriate for the slab allocator,
221          * drop the unsupported bits
222          */
223         mask &= ~(__GFP_DMA32|__GFP_HIGHMEM);
224         state = kmem_cache_alloc(extent_state_cache, mask);
225         if (!state)
226                 return state;
227         state->state = 0;
228         state->failrec = NULL;
229         RB_CLEAR_NODE(&state->rb_node);
230         btrfs_leak_debug_add(&state->leak_list, &states);
231         refcount_set(&state->refs, 1);
232         init_waitqueue_head(&state->wq);
233         trace_alloc_extent_state(state, mask, _RET_IP_);
234         return state;
235 }
236 
237 void free_extent_state(struct extent_state *state)
238 {
239         if (!state)
240                 return;
241         if (refcount_dec_and_test(&state->refs)) {
242                 WARN_ON(extent_state_in_tree(state));
243                 btrfs_leak_debug_del(&state->leak_list);
244                 trace_free_extent_state(state, _RET_IP_);
245                 kmem_cache_free(extent_state_cache, state);
246         }
247 }
248 
249 static struct rb_node *tree_insert(struct rb_root *root,
250                                    struct rb_node *search_start,
251                                    u64 offset,
252                                    struct rb_node *node,
253                                    struct rb_node ***p_in,
254                                    struct rb_node **parent_in)
255 {
256         struct rb_node **p;
257         struct rb_node *parent = NULL;
258         struct tree_entry *entry;
259 
260         if (p_in && parent_in) {
261                 p = *p_in;
262                 parent = *parent_in;
263                 goto do_insert;
264         }
265 
266         p = search_start ? &search_start : &root->rb_node;
267         while (*p) {
268                 parent = *p;
269                 entry = rb_entry(parent, struct tree_entry, rb_node);
270 
271                 if (offset < entry->start)
272                         p = &(*p)->rb_left;
273                 else if (offset > entry->end)
274                         p = &(*p)->rb_right;
275                 else
276                         return parent;
277         }
278 
279 do_insert:
280         rb_link_node(node, parent, p);
281         rb_insert_color(node, root);
282         return NULL;
283 }
284 
285 static struct rb_node *__etree_search(struct extent_io_tree *tree, u64 offset,
286                                       struct rb_node **prev_ret,
287                                       struct rb_node **next_ret,
288                                       struct rb_node ***p_ret,
289                                       struct rb_node **parent_ret)
290 {
291         struct rb_root *root = &tree->state;
292         struct rb_node **n = &root->rb_node;
293         struct rb_node *prev = NULL;
294         struct rb_node *orig_prev = NULL;
295         struct tree_entry *entry;
296         struct tree_entry *prev_entry = NULL;
297 
298         while (*n) {
299                 prev = *n;
300                 entry = rb_entry(prev, struct tree_entry, rb_node);
301                 prev_entry = entry;
302 
303                 if (offset < entry->start)
304                         n = &(*n)->rb_left;
305                 else if (offset > entry->end)
306                         n = &(*n)->rb_right;
307                 else
308                         return *n;
309         }
310 
311         if (p_ret)
312                 *p_ret = n;
313         if (parent_ret)
314                 *parent_ret = prev;
315 
316         if (prev_ret) {
317                 orig_prev = prev;
318                 while (prev && offset > prev_entry->end) {
319                         prev = rb_next(prev);
320                         prev_entry = rb_entry(prev, struct tree_entry, rb_node);
321                 }
322                 *prev_ret = prev;
323                 prev = orig_prev;
324         }
325 
326         if (next_ret) {
327                 prev_entry = rb_entry(prev, struct tree_entry, rb_node);
328                 while (prev && offset < prev_entry->start) {
329                         prev = rb_prev(prev);
330                         prev_entry = rb_entry(prev, struct tree_entry, rb_node);
331                 }
332                 *next_ret = prev;
333         }
334         return NULL;
335 }
336 
337 static inline struct rb_node *
338 tree_search_for_insert(struct extent_io_tree *tree,
339                        u64 offset,
340                        struct rb_node ***p_ret,
341                        struct rb_node **parent_ret)
342 {
343         struct rb_node *prev = NULL;
344         struct rb_node *ret;
345 
346         ret = __etree_search(tree, offset, &prev, NULL, p_ret, parent_ret);
347         if (!ret)
348                 return prev;
349         return ret;
350 }
351 
352 static inline struct rb_node *tree_search(struct extent_io_tree *tree,
353                                           u64 offset)
354 {
355         return tree_search_for_insert(tree, offset, NULL, NULL);
356 }
357 
358 static void merge_cb(struct extent_io_tree *tree, struct extent_state *new,
359                      struct extent_state *other)
360 {
361         if (tree->ops && tree->ops->merge_extent_hook)
362                 tree->ops->merge_extent_hook(tree->private_data, new, other);
363 }
364 
365 /*
366  * utility function to look for merge candidates inside a given range.
367  * Any extents with matching state are merged together into a single
368  * extent in the tree.  Extents with EXTENT_IO in their state field
369  * are not merged because the end_io handlers need to be able to do
370  * operations on them without sleeping (or doing allocations/splits).
371  *
372  * This should be called with the tree lock held.
373  */
374 static void merge_state(struct extent_io_tree *tree,
375                         struct extent_state *state)
376 {
377         struct extent_state *other;
378         struct rb_node *other_node;
379 
380         if (state->state & (EXTENT_IOBITS | EXTENT_BOUNDARY))
381                 return;
382 
383         other_node = rb_prev(&state->rb_node);
384         if (other_node) {
385                 other = rb_entry(other_node, struct extent_state, rb_node);
386                 if (other->end == state->start - 1 &&
387                     other->state == state->state) {
388                         merge_cb(tree, state, other);
389                         state->start = other->start;
390                         rb_erase(&other->rb_node, &tree->state);
391                         RB_CLEAR_NODE(&other->rb_node);
392                         free_extent_state(other);
393                 }
394         }
395         other_node = rb_next(&state->rb_node);
396         if (other_node) {
397                 other = rb_entry(other_node, struct extent_state, rb_node);
398                 if (other->start == state->end + 1 &&
399                     other->state == state->state) {
400                         merge_cb(tree, state, other);
401                         state->end = other->end;
402                         rb_erase(&other->rb_node, &tree->state);
403                         RB_CLEAR_NODE(&other->rb_node);
404                         free_extent_state(other);
405                 }
406         }
407 }
408 
409 static void set_state_cb(struct extent_io_tree *tree,
410                          struct extent_state *state, unsigned *bits)
411 {
412         if (tree->ops && tree->ops->set_bit_hook)
413                 tree->ops->set_bit_hook(tree->private_data, state, bits);
414 }
415 
416 static void clear_state_cb(struct extent_io_tree *tree,
417                            struct extent_state *state, unsigned *bits)
418 {
419         if (tree->ops && tree->ops->clear_bit_hook)
420                 tree->ops->clear_bit_hook(tree->private_data, state, bits);
421 }
422 
423 static void set_state_bits(struct extent_io_tree *tree,
424                            struct extent_state *state, unsigned *bits,
425                            struct extent_changeset *changeset);
426 
427 /*
428  * insert an extent_state struct into the tree.  'bits' are set on the
429  * struct before it is inserted.
430  *
431  * This may return -EEXIST if the extent is already there, in which case the
432  * state struct is freed.
433  *
434  * The tree lock is not taken internally.  This is a utility function and
435  * probably isn't what you want to call (see set/clear_extent_bit).
436  */
437 static int insert_state(struct extent_io_tree *tree,
438                         struct extent_state *state, u64 start, u64 end,
439                         struct rb_node ***p,
440                         struct rb_node **parent,
441                         unsigned *bits, struct extent_changeset *changeset)
442 {
443         struct rb_node *node;
444 
445         if (end < start)
446                 WARN(1, KERN_ERR "BTRFS: end < start %llu %llu\n",
447                        end, start);
448         state->start = start;
449         state->end = end;
450 
451         set_state_bits(tree, state, bits, changeset);
452 
453         node = tree_insert(&tree->state, NULL, end, &state->rb_node, p, parent);
454         if (node) {
455                 struct extent_state *found;
456                 found = rb_entry(node, struct extent_state, rb_node);
457                 pr_err("BTRFS: found node %llu %llu on insert of %llu %llu\n",
458                        found->start, found->end, start, end);
459                 return -EEXIST;
460         }
461         merge_state(tree, state);
462         return 0;
463 }
464 
465 static void split_cb(struct extent_io_tree *tree, struct extent_state *orig,
466                      u64 split)
467 {
468         if (tree->ops && tree->ops->split_extent_hook)
469                 tree->ops->split_extent_hook(tree->private_data, orig, split);
470 }
471 
472 /*
473  * split a given extent state struct in two, inserting the preallocated
474  * struct 'prealloc' as the newly created second half.  'split' indicates an
475  * offset inside 'orig' where it should be split.
476  *
477  * Before calling,
478  * the tree has 'orig' at [orig->start, orig->end].  After calling, there
479  * are two extent state structs in the tree:
480  * prealloc: [orig->start, split - 1]
481  * orig: [ split, orig->end ]
482  *
483  * The tree locks are not taken by this function. They need to be held
484  * by the caller.
485  */
486 static int split_state(struct extent_io_tree *tree, struct extent_state *orig,
487                        struct extent_state *prealloc, u64 split)
488 {
489         struct rb_node *node;
490 
491         split_cb(tree, orig, split);
492 
493         prealloc->start = orig->start;
494         prealloc->end = split - 1;
495         prealloc->state = orig->state;
496         orig->start = split;
497 
498         node = tree_insert(&tree->state, &orig->rb_node, prealloc->end,
499                            &prealloc->rb_node, NULL, NULL);
500         if (node) {
501                 free_extent_state(prealloc);
502                 return -EEXIST;
503         }
504         return 0;
505 }
506 
507 static struct extent_state *next_state(struct extent_state *state)
508 {
509         struct rb_node *next = rb_next(&state->rb_node);
510         if (next)
511                 return rb_entry(next, struct extent_state, rb_node);
512         else
513                 return NULL;
514 }
515 
516 /*
517  * utility function to clear some bits in an extent state struct.
518  * it will optionally wake up any one waiting on this state (wake == 1).
519  *
520  * If no bits are set on the state struct after clearing things, the
521  * struct is freed and removed from the tree
522  */
523 static struct extent_state *clear_state_bit(struct extent_io_tree *tree,
524                                             struct extent_state *state,
525                                             unsigned *bits, int wake,
526                                             struct extent_changeset *changeset)
527 {
528         struct extent_state *next;
529         unsigned bits_to_clear = *bits & ~EXTENT_CTLBITS;
530         int ret;
531 
532         if ((bits_to_clear & EXTENT_DIRTY) && (state->state & EXTENT_DIRTY)) {
533                 u64 range = state->end - state->start + 1;
534                 WARN_ON(range > tree->dirty_bytes);
535                 tree->dirty_bytes -= range;
536         }
537         clear_state_cb(tree, state, bits);
538         ret = add_extent_changeset(state, bits_to_clear, changeset, 0);
539         BUG_ON(ret < 0);
540         state->state &= ~bits_to_clear;
541         if (wake)
542                 wake_up(&state->wq);
543         if (state->state == 0) {
544                 next = next_state(state);
545                 if (extent_state_in_tree(state)) {
546                         rb_erase(&state->rb_node, &tree->state);
547                         RB_CLEAR_NODE(&state->rb_node);
548                         free_extent_state(state);
549                 } else {
550                         WARN_ON(1);
551                 }
552         } else {
553                 merge_state(tree, state);
554                 next = next_state(state);
555         }
556         return next;
557 }
558 
559 static struct extent_state *
560 alloc_extent_state_atomic(struct extent_state *prealloc)
561 {
562         if (!prealloc)
563                 prealloc = alloc_extent_state(GFP_ATOMIC);
564 
565         return prealloc;
566 }
567 
568 static void extent_io_tree_panic(struct extent_io_tree *tree, int err)
569 {
570         btrfs_panic(tree_fs_info(tree), err,
571                     "Locking error: Extent tree was modified by another thread while locked.");
572 }
573 
574 /*
575  * clear some bits on a range in the tree.  This may require splitting
576  * or inserting elements in the tree, so the gfp mask is used to
577  * indicate which allocations or sleeping are allowed.
578  *
579  * pass 'wake' == 1 to kick any sleepers, and 'delete' == 1 to remove
580  * the given range from the tree regardless of state (ie for truncate).
581  *
582  * the range [start, end] is inclusive.
583  *
584  * This takes the tree lock, and returns 0 on success and < 0 on error.
585  */
586 int __clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
587                               unsigned bits, int wake, int delete,
588                               struct extent_state **cached_state,
589                               gfp_t mask, struct extent_changeset *changeset)
590 {
591         struct extent_state *state;
592         struct extent_state *cached;
593         struct extent_state *prealloc = NULL;
594         struct rb_node *node;
595         u64 last_end;
596         int err;
597         int clear = 0;
598 
599         btrfs_debug_check_extent_io_range(tree, start, end);
600 
601         if (bits & EXTENT_DELALLOC)
602                 bits |= EXTENT_NORESERVE;
603 
604         if (delete)
605                 bits |= ~EXTENT_CTLBITS;
606         bits |= EXTENT_FIRST_DELALLOC;
607 
608         if (bits & (EXTENT_IOBITS | EXTENT_BOUNDARY))
609                 clear = 1;
610 again:
611         if (!prealloc && gfpflags_allow_blocking(mask)) {
612                 /*
613                  * Don't care for allocation failure here because we might end
614                  * up not needing the pre-allocated extent state at all, which
615                  * is the case if we only have in the tree extent states that
616                  * cover our input range and don't cover too any other range.
617                  * If we end up needing a new extent state we allocate it later.
618                  */
619                 prealloc = alloc_extent_state(mask);
620         }
621 
622         spin_lock(&tree->lock);
623         if (cached_state) {
624                 cached = *cached_state;
625 
626                 if (clear) {
627                         *cached_state = NULL;
628                         cached_state = NULL;
629                 }
630 
631                 if (cached && extent_state_in_tree(cached) &&
632                     cached->start <= start && cached->end > start) {
633                         if (clear)
634                                 refcount_dec(&cached->refs);
635                         state = cached;
636                         goto hit_next;
637                 }
638                 if (clear)
639                         free_extent_state(cached);
640         }
641         /*
642          * this search will find the extents that end after
643          * our range starts
644          */
645         node = tree_search(tree, start);
646         if (!node)
647                 goto out;
648         state = rb_entry(node, struct extent_state, rb_node);
649 hit_next:
650         if (state->start > end)
651                 goto out;
652         WARN_ON(state->end < start);
653         last_end = state->end;
654 
655         /* the state doesn't have the wanted bits, go ahead */
656         if (!(state->state & bits)) {
657                 state = next_state(state);
658                 goto next;
659         }
660 
661         /*
662          *     | ---- desired range ---- |
663          *  | state | or
664          *  | ------------- state -------------- |
665          *
666          * We need to split the extent we found, and may flip
667          * bits on second half.
668          *
669          * If the extent we found extends past our range, we
670          * just split and search again.  It'll get split again
671          * the next time though.
672          *
673          * If the extent we found is inside our range, we clear
674          * the desired bit on it.
675          */
676 
677         if (state->start < start) {
678                 prealloc = alloc_extent_state_atomic(prealloc);
679                 BUG_ON(!prealloc);
680                 err = split_state(tree, state, prealloc, start);
681                 if (err)
682                         extent_io_tree_panic(tree, err);
683 
684                 prealloc = NULL;
685                 if (err)
686                         goto out;
687                 if (state->end <= end) {
688                         state = clear_state_bit(tree, state, &bits, wake,
689                                                 changeset);
690                         goto next;
691                 }
692                 goto search_again;
693         }
694         /*
695          * | ---- desired range ---- |
696          *                        | state |
697          * We need to split the extent, and clear the bit
698          * on the first half
699          */
700         if (state->start <= end && state->end > end) {
701                 prealloc = alloc_extent_state_atomic(prealloc);
702                 BUG_ON(!prealloc);
703                 err = split_state(tree, state, prealloc, end + 1);
704                 if (err)
705                         extent_io_tree_panic(tree, err);
706 
707                 if (wake)
708                         wake_up(&state->wq);
709 
710                 clear_state_bit(tree, prealloc, &bits, wake, changeset);
711 
712                 prealloc = NULL;
713                 goto out;
714         }
715 
716         state = clear_state_bit(tree, state, &bits, wake, changeset);
717 next:
718         if (last_end == (u64)-1)
719                 goto out;
720         start = last_end + 1;
721         if (start <= end && state && !need_resched())
722                 goto hit_next;
723 
724 search_again:
725         if (start > end)
726                 goto out;
727         spin_unlock(&tree->lock);
728         if (gfpflags_allow_blocking(mask))
729                 cond_resched();
730         goto again;
731 
732 out:
733         spin_unlock(&tree->lock);
734         if (prealloc)
735                 free_extent_state(prealloc);
736 
737         return 0;
738 
739 }
740 
741 static void wait_on_state(struct extent_io_tree *tree,
742                           struct extent_state *state)
743                 __releases(tree->lock)
744                 __acquires(tree->lock)
745 {
746         DEFINE_WAIT(wait);
747         prepare_to_wait(&state->wq, &wait, TASK_UNINTERRUPTIBLE);
748         spin_unlock(&tree->lock);
749         schedule();
750         spin_lock(&tree->lock);
751         finish_wait(&state->wq, &wait);
752 }
753 
754 /*
755  * waits for one or more bits to clear on a range in the state tree.
756  * The range [start, end] is inclusive.
757  * The tree lock is taken by this function
758  */
759 static void wait_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
760                             unsigned long bits)
761 {
762         struct extent_state *state;
763         struct rb_node *node;
764 
765         btrfs_debug_check_extent_io_range(tree, start, end);
766 
767         spin_lock(&tree->lock);
768 again:
769         while (1) {
770                 /*
771                  * this search will find all the extents that end after
772                  * our range starts
773                  */
774                 node = tree_search(tree, start);
775 process_node:
776                 if (!node)
777                         break;
778 
779                 state = rb_entry(node, struct extent_state, rb_node);
780 
781                 if (state->start > end)
782                         goto out;
783 
784                 if (state->state & bits) {
785                         start = state->start;
786                         refcount_inc(&state->refs);
787                         wait_on_state(tree, state);
788                         free_extent_state(state);
789                         goto again;
790                 }
791                 start = state->end + 1;
792 
793                 if (start > end)
794                         break;
795 
796                 if (!cond_resched_lock(&tree->lock)) {
797                         node = rb_next(node);
798                         goto process_node;
799                 }
800         }
801 out:
802         spin_unlock(&tree->lock);
803 }
804 
805 static void set_state_bits(struct extent_io_tree *tree,
806                            struct extent_state *state,
807                            unsigned *bits, struct extent_changeset *changeset)
808 {
809         unsigned bits_to_set = *bits & ~EXTENT_CTLBITS;
810         int ret;
811 
812         set_state_cb(tree, state, bits);
813         if ((bits_to_set & EXTENT_DIRTY) && !(state->state & EXTENT_DIRTY)) {
814                 u64 range = state->end - state->start + 1;
815                 tree->dirty_bytes += range;
816         }
817         ret = add_extent_changeset(state, bits_to_set, changeset, 1);
818         BUG_ON(ret < 0);
819         state->state |= bits_to_set;
820 }
821 
822 static void cache_state_if_flags(struct extent_state *state,
823                                  struct extent_state **cached_ptr,
824                                  unsigned flags)
825 {
826         if (cached_ptr && !(*cached_ptr)) {
827                 if (!flags || (state->state & flags)) {
828                         *cached_ptr = state;
829                         refcount_inc(&state->refs);
830                 }
831         }
832 }
833 
834 static void cache_state(struct extent_state *state,
835                         struct extent_state **cached_ptr)
836 {
837         return cache_state_if_flags(state, cached_ptr,
838                                     EXTENT_IOBITS | EXTENT_BOUNDARY);
839 }
840 
841 /*
842  * set some bits on a range in the tree.  This may require allocations or
843  * sleeping, so the gfp mask is used to indicate what is allowed.
844  *
845  * If any of the exclusive bits are set, this will fail with -EEXIST if some
846  * part of the range already has the desired bits set.  The start of the
847  * existing range is returned in failed_start in this case.
848  *
849  * [start, end] is inclusive This takes the tree lock.
850  */
851 
852 static int __must_check
853 __set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
854                  unsigned bits, unsigned exclusive_bits,
855                  u64 *failed_start, struct extent_state **cached_state,
856                  gfp_t mask, struct extent_changeset *changeset)
857 {
858         struct extent_state *state;
859         struct extent_state *prealloc = NULL;
860         struct rb_node *node;
861         struct rb_node **p;
862         struct rb_node *parent;
863         int err = 0;
864         u64 last_start;
865         u64 last_end;
866 
867         btrfs_debug_check_extent_io_range(tree, start, end);
868 
869         bits |= EXTENT_FIRST_DELALLOC;
870 again:
871         if (!prealloc && gfpflags_allow_blocking(mask)) {
872                 /*
873                  * Don't care for allocation failure here because we might end
874                  * up not needing the pre-allocated extent state at all, which
875                  * is the case if we only have in the tree extent states that
876                  * cover our input range and don't cover too any other range.
877                  * If we end up needing a new extent state we allocate it later.
878                  */
879                 prealloc = alloc_extent_state(mask);
880         }
881 
882         spin_lock(&tree->lock);
883         if (cached_state && *cached_state) {
884                 state = *cached_state;
885                 if (state->start <= start && state->end > start &&
886                     extent_state_in_tree(state)) {
887                         node = &state->rb_node;
888                         goto hit_next;
889                 }
890         }
891         /*
892          * this search will find all the extents that end after
893          * our range starts.
894          */
895         node = tree_search_for_insert(tree, start, &p, &parent);
896         if (!node) {
897                 prealloc = alloc_extent_state_atomic(prealloc);
898                 BUG_ON(!prealloc);
899                 err = insert_state(tree, prealloc, start, end,
900                                    &p, &parent, &bits, changeset);
901                 if (err)
902                         extent_io_tree_panic(tree, err);
903 
904                 cache_state(prealloc, cached_state);
905                 prealloc = NULL;
906                 goto out;
907         }
908         state = rb_entry(node, struct extent_state, rb_node);
909 hit_next:
910         last_start = state->start;
911         last_end = state->end;
912 
913         /*
914          * | ---- desired range ---- |
915          * | state |
916          *
917          * Just lock what we found and keep going
918          */
919         if (state->start == start && state->end <= end) {
920                 if (state->state & exclusive_bits) {
921                         *failed_start = state->start;
922                         err = -EEXIST;
923                         goto out;
924                 }
925 
926                 set_state_bits(tree, state, &bits, changeset);
927                 cache_state(state, cached_state);
928                 merge_state(tree, state);
929                 if (last_end == (u64)-1)
930                         goto out;
931                 start = last_end + 1;
932                 state = next_state(state);
933                 if (start < end && state && state->start == start &&
934                     !need_resched())
935                         goto hit_next;
936                 goto search_again;
937         }
938 
939         /*
940          *     | ---- desired range ---- |
941          * | state |
942          *   or
943          * | ------------- state -------------- |
944          *
945          * We need to split the extent we found, and may flip bits on
946          * second half.
947          *
948          * If the extent we found extends past our
949          * range, we just split and search again.  It'll get split
950          * again the next time though.
951          *
952          * If the extent we found is inside our range, we set the
953          * desired bit on it.
954          */
955         if (state->start < start) {
956                 if (state->state & exclusive_bits) {
957                         *failed_start = start;
958                         err = -EEXIST;
959                         goto out;
960                 }
961 
962                 prealloc = alloc_extent_state_atomic(prealloc);
963                 BUG_ON(!prealloc);
964                 err = split_state(tree, state, prealloc, start);
965                 if (err)
966                         extent_io_tree_panic(tree, err);
967 
968                 prealloc = NULL;
969                 if (err)
970                         goto out;
971                 if (state->end <= end) {
972                         set_state_bits(tree, state, &bits, changeset);
973                         cache_state(state, cached_state);
974                         merge_state(tree, state);
975                         if (last_end == (u64)-1)
976                                 goto out;
977                         start = last_end + 1;
978                         state = next_state(state);
979                         if (start < end && state && state->start == start &&
980                             !need_resched())
981                                 goto hit_next;
982                 }
983                 goto search_again;
984         }
985         /*
986          * | ---- desired range ---- |
987          *     | state | or               | state |
988          *
989          * There's a hole, we need to insert something in it and
990          * ignore the extent we found.
991          */
992         if (state->start > start) {
993                 u64 this_end;
994                 if (end < last_start)
995                         this_end = end;
996                 else
997                         this_end = last_start - 1;
998 
999                 prealloc = alloc_extent_state_atomic(prealloc);
1000                 BUG_ON(!prealloc);
1001 
1002                 /*
1003                  * Avoid to free 'prealloc' if it can be merged with
1004                  * the later extent.
1005                  */
1006                 err = insert_state(tree, prealloc, start, this_end,
1007                                    NULL, NULL, &bits, changeset);
1008                 if (err)
1009                         extent_io_tree_panic(tree, err);
1010 
1011                 cache_state(prealloc, cached_state);
1012                 prealloc = NULL;
1013                 start = this_end + 1;
1014                 goto search_again;
1015         }
1016         /*
1017          * | ---- desired range ---- |
1018          *                        | state |
1019          * We need to split the extent, and set the bit
1020          * on the first half
1021          */
1022         if (state->start <= end && state->end > end) {
1023                 if (state->state & exclusive_bits) {
1024                         *failed_start = start;
1025                         err = -EEXIST;
1026                         goto out;
1027                 }
1028 
1029                 prealloc = alloc_extent_state_atomic(prealloc);
1030                 BUG_ON(!prealloc);
1031                 err = split_state(tree, state, prealloc, end + 1);
1032                 if (err)
1033                         extent_io_tree_panic(tree, err);
1034 
1035                 set_state_bits(tree, prealloc, &bits, changeset);
1036                 cache_state(prealloc, cached_state);
1037                 merge_state(tree, prealloc);
1038                 prealloc = NULL;
1039                 goto out;
1040         }
1041 
1042 search_again:
1043         if (start > end)
1044                 goto out;
1045         spin_unlock(&tree->lock);
1046         if (gfpflags_allow_blocking(mask))
1047                 cond_resched();
1048         goto again;
1049 
1050 out:
1051         spin_unlock(&tree->lock);
1052         if (prealloc)
1053                 free_extent_state(prealloc);
1054 
1055         return err;
1056 
1057 }
1058 
1059 int set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
1060                    unsigned bits, u64 * failed_start,
1061                    struct extent_state **cached_state, gfp_t mask)
1062 {
1063         return __set_extent_bit(tree, start, end, bits, 0, failed_start,
1064                                 cached_state, mask, NULL);
1065 }
1066 
1067 
1068 /**
1069  * convert_extent_bit - convert all bits in a given range from one bit to
1070  *                      another
1071  * @tree:       the io tree to search
1072  * @start:      the start offset in bytes
1073  * @end:        the end offset in bytes (inclusive)
1074  * @bits:       the bits to set in this range
1075  * @clear_bits: the bits to clear in this range
1076  * @cached_state:       state that we're going to cache
1077  *
1078  * This will go through and set bits for the given range.  If any states exist
1079  * already in this range they are set with the given bit and cleared of the
1080  * clear_bits.  This is only meant to be used by things that are mergeable, ie
1081  * converting from say DELALLOC to DIRTY.  This is not meant to be used with
1082  * boundary bits like LOCK.
1083  *
1084  * All allocations are done with GFP_NOFS.
1085  */
1086 int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
1087                        unsigned bits, unsigned clear_bits,
1088                        struct extent_state **cached_state)
1089 {
1090         struct extent_state *state;
1091         struct extent_state *prealloc = NULL;
1092         struct rb_node *node;
1093         struct rb_node **p;
1094         struct rb_node *parent;
1095         int err = 0;
1096         u64 last_start;
1097         u64 last_end;
1098         bool first_iteration = true;
1099 
1100         btrfs_debug_check_extent_io_range(tree, start, end);
1101 
1102 again:
1103         if (!prealloc) {
1104                 /*
1105                  * Best effort, don't worry if extent state allocation fails
1106                  * here for the first iteration. We might have a cached state
1107                  * that matches exactly the target range, in which case no
1108                  * extent state allocations are needed. We'll only know this
1109                  * after locking the tree.
1110                  */
1111                 prealloc = alloc_extent_state(GFP_NOFS);
1112                 if (!prealloc && !first_iteration)
1113                         return -ENOMEM;
1114         }
1115 
1116         spin_lock(&tree->lock);
1117         if (cached_state && *cached_state) {
1118                 state = *cached_state;
1119                 if (state->start <= start && state->end > start &&
1120                     extent_state_in_tree(state)) {
1121                         node = &state->rb_node;
1122                         goto hit_next;
1123                 }
1124         }
1125 
1126         /*
1127          * this search will find all the extents that end after
1128          * our range starts.
1129          */
1130         node = tree_search_for_insert(tree, start, &p, &parent);
1131         if (!node) {
1132                 prealloc = alloc_extent_state_atomic(prealloc);
1133                 if (!prealloc) {
1134                         err = -ENOMEM;
1135                         goto out;
1136                 }
1137                 err = insert_state(tree, prealloc, start, end,
1138                                    &p, &parent, &bits, NULL);
1139                 if (err)
1140                         extent_io_tree_panic(tree, err);
1141                 cache_state(prealloc, cached_state);
1142                 prealloc = NULL;
1143                 goto out;
1144         }
1145         state = rb_entry(node, struct extent_state, rb_node);
1146 hit_next:
1147         last_start = state->start;
1148         last_end = state->end;
1149 
1150         /*
1151          * | ---- desired range ---- |
1152          * | state |
1153          *
1154          * Just lock what we found and keep going
1155          */
1156         if (state->start == start && state->end <= end) {
1157                 set_state_bits(tree, state, &bits, NULL);
1158                 cache_state(state, cached_state);
1159                 state = clear_state_bit(tree, state, &clear_bits, 0, NULL);
1160                 if (last_end == (u64)-1)
1161                         goto out;
1162                 start = last_end + 1;
1163                 if (start < end && state && state->start == start &&
1164                     !need_resched())
1165                         goto hit_next;
1166                 goto search_again;
1167         }
1168 
1169         /*
1170          *     | ---- desired range ---- |
1171          * | state |
1172          *   or
1173          * | ------------- state -------------- |
1174          *
1175          * We need to split the extent we found, and may flip bits on
1176          * second half.
1177          *
1178          * If the extent we found extends past our
1179          * range, we just split and search again.  It'll get split
1180          * again the next time though.
1181          *
1182          * If the extent we found is inside our range, we set the
1183          * desired bit on it.
1184          */
1185         if (state->start < start) {
1186                 prealloc = alloc_extent_state_atomic(prealloc);
1187                 if (!prealloc) {
1188                         err = -ENOMEM;
1189                         goto out;
1190                 }
1191                 err = split_state(tree, state, prealloc, start);
1192                 if (err)
1193                         extent_io_tree_panic(tree, err);
1194                 prealloc = NULL;
1195                 if (err)
1196                         goto out;
1197                 if (state->end <= end) {
1198                         set_state_bits(tree, state, &bits, NULL);
1199                         cache_state(state, cached_state);
1200                         state = clear_state_bit(tree, state, &clear_bits, 0,
1201                                                 NULL);
1202                         if (last_end == (u64)-1)
1203                                 goto out;
1204                         start = last_end + 1;
1205                         if (start < end && state && state->start == start &&
1206                             !need_resched())
1207                                 goto hit_next;
1208                 }
1209                 goto search_again;
1210         }
1211         /*
1212          * | ---- desired range ---- |
1213          *     | state | or               | state |
1214          *
1215          * There's a hole, we need to insert something in it and
1216          * ignore the extent we found.
1217          */
1218         if (state->start > start) {
1219                 u64 this_end;
1220                 if (end < last_start)
1221                         this_end = end;
1222                 else
1223                         this_end = last_start - 1;
1224 
1225                 prealloc = alloc_extent_state_atomic(prealloc);
1226                 if (!prealloc) {
1227                         err = -ENOMEM;
1228                         goto out;
1229                 }
1230 
1231                 /*
1232                  * Avoid to free 'prealloc' if it can be merged with
1233                  * the later extent.
1234                  */
1235                 err = insert_state(tree, prealloc, start, this_end,
1236                                    NULL, NULL, &bits, NULL);
1237                 if (err)
1238                         extent_io_tree_panic(tree, err);
1239                 cache_state(prealloc, cached_state);
1240                 prealloc = NULL;
1241                 start = this_end + 1;
1242                 goto search_again;
1243         }
1244         /*
1245          * | ---- desired range ---- |
1246          *                        | state |
1247          * We need to split the extent, and set the bit
1248          * on the first half
1249          */
1250         if (state->start <= end && state->end > end) {
1251                 prealloc = alloc_extent_state_atomic(prealloc);
1252                 if (!prealloc) {
1253                         err = -ENOMEM;
1254                         goto out;
1255                 }
1256 
1257                 err = split_state(tree, state, prealloc, end + 1);
1258                 if (err)
1259                         extent_io_tree_panic(tree, err);
1260 
1261                 set_state_bits(tree, prealloc, &bits, NULL);
1262                 cache_state(prealloc, cached_state);
1263                 clear_state_bit(tree, prealloc, &clear_bits, 0, NULL);
1264                 prealloc = NULL;
1265                 goto out;
1266         }
1267 
1268 search_again:
1269         if (start > end)
1270                 goto out;
1271         spin_unlock(&tree->lock);
1272         cond_resched();
1273         first_iteration = false;
1274         goto again;
1275 
1276 out:
1277         spin_unlock(&tree->lock);
1278         if (prealloc)
1279                 free_extent_state(prealloc);
1280 
1281         return err;
1282 }
1283 
1284 /* wrappers around set/clear extent bit */
1285 int set_record_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
1286                            unsigned bits, struct extent_changeset *changeset)
1287 {
1288         /*
1289          * We don't support EXTENT_LOCKED yet, as current changeset will
1290          * record any bits changed, so for EXTENT_LOCKED case, it will
1291          * either fail with -EEXIST or changeset will record the whole
1292          * range.
1293          */
1294         BUG_ON(bits & EXTENT_LOCKED);
1295 
1296         return __set_extent_bit(tree, start, end, bits, 0, NULL, NULL, GFP_NOFS,
1297                                 changeset);
1298 }
1299 
1300 int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
1301                      unsigned bits, int wake, int delete,
1302                      struct extent_state **cached)
1303 {
1304         return __clear_extent_bit(tree, start, end, bits, wake, delete,
1305                                   cached, GFP_NOFS, NULL);
1306 }
1307 
1308 int clear_record_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
1309                 unsigned bits, struct extent_changeset *changeset)
1310 {
1311         /*
1312          * Don't support EXTENT_LOCKED case, same reason as
1313          * set_record_extent_bits().
1314          */
1315         BUG_ON(bits & EXTENT_LOCKED);
1316 
1317         return __clear_extent_bit(tree, start, end, bits, 0, 0, NULL, GFP_NOFS,
1318                                   changeset);
1319 }
1320 
1321 /*
1322  * either insert or lock state struct between start and end use mask to tell
1323  * us if waiting is desired.
1324  */
1325 int lock_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
1326                      struct extent_state **cached_state)
1327 {
1328         int err;
1329         u64 failed_start;
1330 
1331         while (1) {
1332                 err = __set_extent_bit(tree, start, end, EXTENT_LOCKED,
1333                                        EXTENT_LOCKED, &failed_start,
1334                                        cached_state, GFP_NOFS, NULL);
1335                 if (err == -EEXIST) {
1336                         wait_extent_bit(tree, failed_start, end, EXTENT_LOCKED);
1337                         start = failed_start;
1338                 } else
1339                         break;
1340                 WARN_ON(start > end);
1341         }
1342         return err;
1343 }
1344 
1345 int try_lock_extent(struct extent_io_tree *tree, u64 start, u64 end)
1346 {
1347         int err;
1348         u64 failed_start;
1349 
1350         err = __set_extent_bit(tree, start, end, EXTENT_LOCKED, EXTENT_LOCKED,
1351                                &failed_start, NULL, GFP_NOFS, NULL);
1352         if (err == -EEXIST) {
1353                 if (failed_start > start)
1354                         clear_extent_bit(tree, start, failed_start - 1,
1355                                          EXTENT_LOCKED, 1, 0, NULL);
1356                 return 0;
1357         }
1358         return 1;
1359 }
1360 
1361 void extent_range_clear_dirty_for_io(struct inode *inode, u64 start, u64 end)
1362 {
1363         unsigned long index = start >> PAGE_SHIFT;
1364         unsigned long end_index = end >> PAGE_SHIFT;
1365         struct page *page;
1366 
1367         while (index <= end_index) {
1368                 page = find_get_page(inode->i_mapping, index);
1369                 BUG_ON(!page); /* Pages should be in the extent_io_tree */
1370                 clear_page_dirty_for_io(page);
1371                 put_page(page);
1372                 index++;
1373         }
1374 }
1375 
1376 void extent_range_redirty_for_io(struct inode *inode, u64 start, u64 end)
1377 {
1378         unsigned long index = start >> PAGE_SHIFT;
1379         unsigned long end_index = end >> PAGE_SHIFT;
1380         struct page *page;
1381 
1382         while (index <= end_index) {
1383                 page = find_get_page(inode->i_mapping, index);
1384                 BUG_ON(!page); /* Pages should be in the extent_io_tree */
1385                 __set_page_dirty_nobuffers(page);
1386                 account_page_redirty(page);
1387                 put_page(page);
1388                 index++;
1389         }
1390 }
1391 
1392 /*
1393  * helper function to set both pages and extents in the tree writeback
1394  */
1395 static void set_range_writeback(struct extent_io_tree *tree, u64 start, u64 end)
1396 {
1397         tree->ops->set_range_writeback(tree->private_data, start, end);
1398 }
1399 
1400 /* find the first state struct with 'bits' set after 'start', and
1401  * return it.  tree->lock must be held.  NULL will returned if
1402  * nothing was found after 'start'
1403  */
1404 static struct extent_state *
1405 find_first_extent_bit_state(struct extent_io_tree *tree,
1406                             u64 start, unsigned bits)
1407 {
1408         struct rb_node *node;
1409         struct extent_state *state;
1410 
1411         /*
1412          * this search will find all the extents that end after
1413          * our range starts.
1414          */
1415         node = tree_search(tree, start);
1416         if (!node)
1417                 goto out;
1418 
1419         while (1) {
1420                 state = rb_entry(node, struct extent_state, rb_node);
1421                 if (state->end >= start && (state->state & bits))
1422                         return state;
1423 
1424                 node = rb_next(node);
1425                 if (!node)
1426                         break;
1427         }
1428 out:
1429         return NULL;
1430 }
1431 
1432 /*
1433  * find the first offset in the io tree with 'bits' set. zero is
1434  * returned if we find something, and *start_ret and *end_ret are
1435  * set to reflect the state struct that was found.
1436  *
1437  * If nothing was found, 1 is returned. If found something, return 0.
1438  */
1439 int find_first_extent_bit(struct extent_io_tree *tree, u64 start,
1440                           u64 *start_ret, u64 *end_ret, unsigned bits,
1441                           struct extent_state **cached_state)
1442 {
1443         struct extent_state *state;
1444         struct rb_node *n;
1445         int ret = 1;
1446 
1447         spin_lock(&tree->lock);
1448         if (cached_state && *cached_state) {
1449                 state = *cached_state;
1450                 if (state->end == start - 1 && extent_state_in_tree(state)) {
1451                         n = rb_next(&state->rb_node);
1452                         while (n) {
1453                                 state = rb_entry(n, struct extent_state,
1454                                                  rb_node);
1455                                 if (state->state & bits)
1456                                         goto got_it;
1457                                 n = rb_next(n);
1458                         }
1459                         free_extent_state(*cached_state);
1460                         *cached_state = NULL;
1461                         goto out;
1462                 }
1463                 free_extent_state(*cached_state);
1464                 *cached_state = NULL;
1465         }
1466 
1467         state = find_first_extent_bit_state(tree, start, bits);
1468 got_it:
1469         if (state) {
1470                 cache_state_if_flags(state, cached_state, 0);
1471                 *start_ret = state->start;
1472                 *end_ret = state->end;
1473                 ret = 0;
1474         }
1475 out:
1476         spin_unlock(&tree->lock);
1477         return ret;
1478 }
1479 
1480 /*
1481  * find a contiguous range of bytes in the file marked as delalloc, not
1482  * more than 'max_bytes'.  start and end are used to return the range,
1483  *
1484  * 1 is returned if we find something, 0 if nothing was in the tree
1485  */
1486 static noinline u64 find_delalloc_range(struct extent_io_tree *tree,
1487                                         u64 *start, u64 *end, u64 max_bytes,
1488                                         struct extent_state **cached_state)
1489 {
1490         struct rb_node *node;
1491         struct extent_state *state;
1492         u64 cur_start = *start;
1493         u64 found = 0;
1494         u64 total_bytes = 0;
1495 
1496         spin_lock(&tree->lock);
1497 
1498         /*
1499          * this search will find all the extents that end after
1500          * our range starts.
1501          */
1502         node = tree_search(tree, cur_start);
1503         if (!node) {
1504                 if (!found)
1505                         *end = (u64)-1;
1506                 goto out;
1507         }
1508 
1509         while (1) {
1510                 state = rb_entry(node, struct extent_state, rb_node);
1511                 if (found && (state->start != cur_start ||
1512                               (state->state & EXTENT_BOUNDARY))) {
1513                         goto out;
1514                 }
1515                 if (!(state->state & EXTENT_DELALLOC)) {
1516                         if (!found)
1517                                 *end = state->end;
1518                         goto out;
1519                 }
1520                 if (!found) {
1521                         *start = state->start;
1522                         *cached_state = state;
1523                         refcount_inc(&state->refs);
1524                 }
1525                 found++;
1526                 *end = state->end;
1527                 cur_start = state->end + 1;
1528                 node = rb_next(node);
1529                 total_bytes += state->end - state->start + 1;
1530                 if (total_bytes >= max_bytes)
1531                         break;
1532                 if (!node)
1533                         break;
1534         }
1535 out:
1536         spin_unlock(&tree->lock);
1537         return found;
1538 }
1539 
1540 static int __process_pages_contig(struct address_space *mapping,
1541                                   struct page *locked_page,
1542                                   pgoff_t start_index, pgoff_t end_index,
1543                                   unsigned long page_ops, pgoff_t *index_ret);
1544 
1545 static noinline void __unlock_for_delalloc(struct inode *inode,
1546                                            struct page *locked_page,
1547                                            u64 start, u64 end)
1548 {
1549         unsigned long index = start >> PAGE_SHIFT;
1550         unsigned long end_index = end >> PAGE_SHIFT;
1551 
1552         ASSERT(locked_page);
1553         if (index == locked_page->index && end_index == index)
1554                 return;
1555 
1556         __process_pages_contig(inode->i_mapping, locked_page, index, end_index,
1557                                PAGE_UNLOCK, NULL);
1558 }
1559 
1560 static noinline int lock_delalloc_pages(struct inode *inode,
1561                                         struct page *locked_page,
1562                                         u64 delalloc_start,
1563                                         u64 delalloc_end)
1564 {
1565         unsigned long index = delalloc_start >> PAGE_SHIFT;
1566         unsigned long index_ret = index;
1567         unsigned long end_index = delalloc_end >> PAGE_SHIFT;
1568         int ret;
1569 
1570         ASSERT(locked_page);
1571         if (index == locked_page->index && index == end_index)
1572                 return 0;
1573 
1574         ret = __process_pages_contig(inode->i_mapping, locked_page, index,
1575                                      end_index, PAGE_LOCK, &index_ret);
1576         if (ret == -EAGAIN)
1577                 __unlock_for_delalloc(inode, locked_page, delalloc_start,
1578                                       (u64)index_ret << PAGE_SHIFT);
1579         return ret;
1580 }
1581 
1582 /*
1583  * find a contiguous range of bytes in the file marked as delalloc, not
1584  * more than 'max_bytes'.  start and end are used to return the range,
1585  *
1586  * 1 is returned if we find something, 0 if nothing was in the tree
1587  */
1588 STATIC u64 find_lock_delalloc_range(struct inode *inode,
1589                                     struct extent_io_tree *tree,
1590                                     struct page *locked_page, u64 *start,
1591                                     u64 *end, u64 max_bytes)
1592 {
1593         u64 delalloc_start;
1594         u64 delalloc_end;
1595         u64 found;
1596         struct extent_state *cached_state = NULL;
1597         int ret;
1598         int loops = 0;
1599 
1600 again:
1601         /* step one, find a bunch of delalloc bytes starting at start */
1602         delalloc_start = *start;
1603         delalloc_end = 0;
1604         found = find_delalloc_range(tree, &delalloc_start, &delalloc_end,
1605                                     max_bytes, &cached_state);
1606         if (!found || delalloc_end <= *start) {
1607                 *start = delalloc_start;
1608                 *end = delalloc_end;
1609                 free_extent_state(cached_state);
1610                 return 0;
1611         }
1612 
1613         /*
1614          * start comes from the offset of locked_page.  We have to lock
1615          * pages in order, so we can't process delalloc bytes before
1616          * locked_page
1617          */
1618         if (delalloc_start < *start)
1619                 delalloc_start = *start;
1620 
1621         /*
1622          * make sure to limit the number of pages we try to lock down
1623          */
1624         if (delalloc_end + 1 - delalloc_start > max_bytes)
1625                 delalloc_end = delalloc_start + max_bytes - 1;
1626 
1627         /* step two, lock all the pages after the page that has start */
1628         ret = lock_delalloc_pages(inode, locked_page,
1629                                   delalloc_start, delalloc_end);
1630         if (ret == -EAGAIN) {
1631                 /* some of the pages are gone, lets avoid looping by
1632                  * shortening the size of the delalloc range we're searching
1633                  */
1634                 free_extent_state(cached_state);
1635                 cached_state = NULL;
1636                 if (!loops) {
1637                         max_bytes = PAGE_SIZE;
1638                         loops = 1;
1639                         goto again;
1640                 } else {
1641                         found = 0;
1642                         goto out_failed;
1643                 }
1644         }
1645         BUG_ON(ret); /* Only valid values are 0 and -EAGAIN */
1646 
1647         /* step three, lock the state bits for the whole range */
1648         lock_extent_bits(tree, delalloc_start, delalloc_end, &cached_state);
1649 
1650         /* then test to make sure it is all still delalloc */
1651         ret = test_range_bit(tree, delalloc_start, delalloc_end,
1652                              EXTENT_DELALLOC, 1, cached_state);
1653         if (!ret) {
1654                 unlock_extent_cached(tree, delalloc_start, delalloc_end,
1655                                      &cached_state);
1656                 __unlock_for_delalloc(inode, locked_page,
1657                               delalloc_start, delalloc_end);
1658                 cond_resched();
1659                 goto again;
1660         }
1661         free_extent_state(cached_state);
1662         *start = delalloc_start;
1663         *end = delalloc_end;
1664 out_failed:
1665         return found;
1666 }
1667 
1668 static int __process_pages_contig(struct address_space *mapping,
1669                                   struct page *locked_page,
1670                                   pgoff_t start_index, pgoff_t end_index,
1671                                   unsigned long page_ops, pgoff_t *index_ret)
1672 {
1673         unsigned long nr_pages = end_index - start_index + 1;
1674         unsigned long pages_locked = 0;
1675         pgoff_t index = start_index;
1676         struct page *pages[16];
1677         unsigned ret;
1678         int err = 0;
1679         int i;
1680 
1681         if (page_ops & PAGE_LOCK) {
1682                 ASSERT(page_ops == PAGE_LOCK);
1683                 ASSERT(index_ret && *index_ret == start_index);
1684         }
1685 
1686         if ((page_ops & PAGE_SET_ERROR) && nr_pages > 0)
1687                 mapping_set_error(mapping, -EIO);
1688 
1689         while (nr_pages > 0) {
1690                 ret = find_get_pages_contig(mapping, index,
1691                                      min_t(unsigned long,
1692                                      nr_pages, ARRAY_SIZE(pages)), pages);
1693                 if (ret == 0) {
1694                         /*
1695                          * Only if we're going to lock these pages,
1696                          * can we find nothing at @index.
1697                          */
1698                         ASSERT(page_ops & PAGE_LOCK);
1699                         err = -EAGAIN;
1700                         goto out;
1701                 }
1702 
1703                 for (i = 0; i < ret; i++) {
1704                         if (page_ops & PAGE_SET_PRIVATE2)
1705                                 SetPagePrivate2(pages[i]);
1706 
1707                         if (pages[i] == locked_page) {
1708                                 put_page(pages[i]);
1709                                 pages_locked++;
1710                                 continue;
1711                         }
1712                         if (page_ops & PAGE_CLEAR_DIRTY)
1713                                 clear_page_dirty_for_io(pages[i]);
1714                         if (page_ops & PAGE_SET_WRITEBACK)
1715                                 set_page_writeback(pages[i]);
1716                         if (page_ops & PAGE_SET_ERROR)
1717                                 SetPageError(pages[i]);
1718                         if (page_ops & PAGE_END_WRITEBACK)
1719                                 end_page_writeback(pages[i]);
1720                         if (page_ops & PAGE_UNLOCK)
1721                                 unlock_page(pages[i]);
1722                         if (page_ops & PAGE_LOCK) {
1723                                 lock_page(pages[i]);
1724                                 if (!PageDirty(pages[i]) ||
1725                                     pages[i]->mapping != mapping) {
1726                                         unlock_page(pages[i]);
1727                                         put_page(pages[i]);
1728                                         err = -EAGAIN;
1729                                         goto out;
1730                                 }
1731                         }
1732                         put_page(pages[i]);
1733                         pages_locked++;
1734                 }
1735                 nr_pages -= ret;
1736                 index += ret;
1737                 cond_resched();
1738         }
1739 out:
1740         if (err && index_ret)
1741                 *index_ret = start_index + pages_locked - 1;
1742         return err;
1743 }
1744 
1745 void extent_clear_unlock_delalloc(struct inode *inode, u64 start, u64 end,
1746                                  u64 delalloc_end, struct page *locked_page,
1747                                  unsigned clear_bits,
1748                                  unsigned long page_ops)
1749 {
1750         clear_extent_bit(&BTRFS_I(inode)->io_tree, start, end, clear_bits, 1, 0,
1751                          NULL);
1752 
1753         __process_pages_contig(inode->i_mapping, locked_page,
1754                                start >> PAGE_SHIFT, end >> PAGE_SHIFT,
1755                                page_ops, NULL);
1756 }
1757 
1758 /*
1759  * count the number of bytes in the tree that have a given bit(s)
1760  * set.  This can be fairly slow, except for EXTENT_DIRTY which is
1761  * cached.  The total number found is returned.
1762  */
1763 u64 count_range_bits(struct extent_io_tree *tree,
1764                      u64 *start, u64 search_end, u64 max_bytes,
1765                      unsigned bits, int contig)
1766 {
1767         struct rb_node *node;
1768         struct extent_state *state;
1769         u64 cur_start = *start;
1770         u64 total_bytes = 0;
1771         u64 last = 0;
1772         int found = 0;
1773 
1774         if (WARN_ON(search_end <= cur_start))
1775                 return 0;
1776 
1777         spin_lock(&tree->lock);
1778         if (cur_start == 0 && bits == EXTENT_DIRTY) {
1779                 total_bytes = tree->dirty_bytes;
1780                 goto out;
1781         }
1782         /*
1783          * this search will find all the extents that end after
1784          * our range starts.
1785          */
1786         node = tree_search(tree, cur_start);
1787         if (!node)
1788                 goto out;
1789 
1790         while (1) {
1791                 state = rb_entry(node, struct extent_state, rb_node);
1792                 if (state->start > search_end)
1793                         break;
1794                 if (contig && found && state->start > last + 1)
1795                         break;
1796                 if (state->end >= cur_start && (state->state & bits) == bits) {
1797                         total_bytes += min(search_end, state->end) + 1 -
1798                                        max(cur_start, state->start);
1799                         if (total_bytes >= max_bytes)
1800                                 break;
1801                         if (!found) {
1802                                 *start = max(cur_start, state->start);
1803                                 found = 1;
1804                         }
1805                         last = state->end;
1806                 } else if (contig && found) {
1807                         break;
1808                 }
1809                 node = rb_next(node);
1810                 if (!node)
1811                         break;
1812         }
1813 out:
1814         spin_unlock(&tree->lock);
1815         return total_bytes;
1816 }
1817 
1818 /*
1819  * set the private field for a given byte offset in the tree.  If there isn't
1820  * an extent_state there already, this does nothing.
1821  */
1822 static noinline int set_state_failrec(struct extent_io_tree *tree, u64 start,
1823                 struct io_failure_record *failrec)
1824 {
1825         struct rb_node *node;
1826         struct extent_state *state;
1827         int ret = 0;
1828 
1829         spin_lock(&tree->lock);
1830         /*
1831          * this search will find all the extents that end after
1832          * our range starts.
1833          */
1834         node = tree_search(tree, start);
1835         if (!node) {
1836                 ret = -ENOENT;
1837                 goto out;
1838         }
1839         state = rb_entry(node, struct extent_state, rb_node);
1840         if (state->start != start) {
1841                 ret = -ENOENT;
1842                 goto out;
1843         }
1844         state->failrec = failrec;
1845 out:
1846         spin_unlock(&tree->lock);
1847         return ret;
1848 }
1849 
1850 static noinline int get_state_failrec(struct extent_io_tree *tree, u64 start,
1851                 struct io_failure_record **failrec)
1852 {
1853         struct rb_node *node;
1854         struct extent_state *state;
1855         int ret = 0;
1856 
1857         spin_lock(&tree->lock);
1858         /*
1859          * this search will find all the extents that end after
1860          * our range starts.
1861          */
1862         node = tree_search(tree, start);
1863         if (!node) {
1864                 ret = -ENOENT;
1865                 goto out;
1866         }
1867         state = rb_entry(node, struct extent_state, rb_node);
1868         if (state->start != start) {
1869                 ret = -ENOENT;
1870                 goto out;
1871         }
1872         *failrec = state->failrec;
1873 out:
1874         spin_unlock(&tree->lock);
1875         return ret;
1876 }
1877 
1878 /*
1879  * searches a range in the state tree for a given mask.
1880  * If 'filled' == 1, this returns 1 only if every extent in the tree
1881  * has the bits set.  Otherwise, 1 is returned if any bit in the
1882  * range is found set.
1883  */
1884 int test_range_bit(struct extent_io_tree *tree, u64 start, u64 end,
1885                    unsigned bits, int filled, struct extent_state *cached)
1886 {
1887         struct extent_state *state = NULL;
1888         struct rb_node *node;
1889         int bitset = 0;
1890 
1891         spin_lock(&tree->lock);
1892         if (cached && extent_state_in_tree(cached) && cached->start <= start &&
1893             cached->end > start)
1894                 node = &cached->rb_node;
1895         else
1896                 node = tree_search(tree, start);
1897         while (node && start <= end) {
1898                 state = rb_entry(node, struct extent_state, rb_node);
1899 
1900                 if (filled && state->start > start) {
1901                         bitset = 0;
1902                         break;
1903                 }
1904 
1905                 if (state->start > end)
1906                         break;
1907 
1908                 if (state->state & bits) {
1909                         bitset = 1;
1910                         if (!filled)
1911                                 break;
1912                 } else if (filled) {
1913                         bitset = 0;
1914                         break;
1915                 }
1916 
1917                 if (state->end == (u64)-1)
1918                         break;
1919 
1920                 start = state->end + 1;
1921                 if (start > end)
1922                         break;
1923                 node = rb_next(node);
1924                 if (!node) {
1925                         if (filled)
1926                                 bitset = 0;
1927                         break;
1928                 }
1929         }
1930         spin_unlock(&tree->lock);
1931         return bitset;
1932 }
1933 
1934 /*
1935  * helper function to set a given page up to date if all the
1936  * extents in the tree for that page are up to date
1937  */
1938 static void check_page_uptodate(struct extent_io_tree *tree, struct page *page)
1939 {
1940         u64 start = page_offset(page);
1941         u64 end = start + PAGE_SIZE - 1;
1942         if (test_range_bit(tree, start, end, EXTENT_UPTODATE, 1, NULL))
1943                 SetPageUptodate(page);
1944 }
1945 
1946 int free_io_failure(struct extent_io_tree *failure_tree,
1947                     struct extent_io_tree *io_tree,
1948                     struct io_failure_record *rec)
1949 {
1950         int ret;
1951         int err = 0;
1952 
1953         set_state_failrec(failure_tree, rec->start, NULL);
1954         ret = clear_extent_bits(failure_tree, rec->start,
1955                                 rec->start + rec->len - 1,
1956                                 EXTENT_LOCKED | EXTENT_DIRTY);
1957         if (ret)
1958                 err = ret;
1959 
1960         ret = clear_extent_bits(io_tree, rec->start,
1961                                 rec->start + rec->len - 1,
1962                                 EXTENT_DAMAGED);
1963         if (ret && !err)
1964                 err = ret;
1965 
1966         kfree(rec);
1967         return err;
1968 }
1969 
1970 /*
1971  * this bypasses the standard btrfs submit functions deliberately, as
1972  * the standard behavior is to write all copies in a raid setup. here we only
1973  * want to write the one bad copy. so we do the mapping for ourselves and issue
1974  * submit_bio directly.
1975  * to avoid any synchronization issues, wait for the data after writing, which
1976  * actually prevents the read that triggered the error from finishing.
1977  * currently, there can be no more than two copies of every data bit. thus,
1978  * exactly one rewrite is required.
1979  */
1980 int repair_io_failure(struct btrfs_fs_info *fs_info, u64 ino, u64 start,
1981                       u64 length, u64 logical, struct page *page,
1982                       unsigned int pg_offset, int mirror_num)
1983 {
1984         struct bio *bio;
1985         struct btrfs_device *dev;
1986         u64 map_length = 0;
1987         u64 sector;
1988         struct btrfs_bio *bbio = NULL;
1989         int ret;
1990 
1991         ASSERT(!(fs_info->sb->s_flags & SB_RDONLY));
1992         BUG_ON(!mirror_num);
1993 
1994         bio = btrfs_io_bio_alloc(1);
1995         bio->bi_iter.bi_size = 0;
1996         map_length = length;
1997 
1998         /*
1999          * Avoid races with device replace and make sure our bbio has devices
2000          * associated to its stripes that don't go away while we are doing the
2001          * read repair operation.
2002          */
2003         btrfs_bio_counter_inc_blocked(fs_info);
2004         if (btrfs_is_parity_mirror(fs_info, logical, length)) {
2005                 /*
2006                  * Note that we don't use BTRFS_MAP_WRITE because it's supposed
2007                  * to update all raid stripes, but here we just want to correct
2008                  * bad stripe, thus BTRFS_MAP_READ is abused to only get the bad
2009                  * stripe's dev and sector.
2010                  */
2011                 ret = btrfs_map_block(fs_info, BTRFS_MAP_READ, logical,
2012                                       &map_length, &bbio, 0);
2013                 if (ret) {
2014                         btrfs_bio_counter_dec(fs_info);
2015                         bio_put(bio);
2016                         return -EIO;
2017                 }
2018                 ASSERT(bbio->mirror_num == 1);
2019         } else {
2020                 ret = btrfs_map_block(fs_info, BTRFS_MAP_WRITE, logical,
2021                                       &map_length, &bbio, mirror_num);
2022                 if (ret) {
2023                         btrfs_bio_counter_dec(fs_info);
2024                         bio_put(bio);
2025                         return -EIO;
2026                 }
2027                 BUG_ON(mirror_num != bbio->mirror_num);
2028         }
2029 
2030         sector = bbio->stripes[bbio->mirror_num - 1].physical >> 9;
2031         bio->bi_iter.bi_sector = sector;
2032         dev = bbio->stripes[bbio->mirror_num - 1].dev;
2033         btrfs_put_bbio(bbio);
2034         if (!dev || !dev->bdev ||
2035             !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state)) {
2036                 btrfs_bio_counter_dec(fs_info);
2037                 bio_put(bio);
2038                 return -EIO;
2039         }
2040         bio_set_dev(bio, dev->bdev);
2041         bio->bi_opf = REQ_OP_WRITE | REQ_SYNC;
2042         bio_add_page(bio, page, length, pg_offset);
2043 
2044         if (btrfsic_submit_bio_wait(bio)) {
2045                 /* try to remap that extent elsewhere? */
2046                 btrfs_bio_counter_dec(fs_info);
2047                 bio_put(bio);
2048                 btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_WRITE_ERRS);
2049                 return -EIO;
2050         }
2051 
2052         btrfs_info_rl_in_rcu(fs_info,
2053                 "read error corrected: ino %llu off %llu (dev %s sector %llu)",
2054                                   ino, start,
2055                                   rcu_str_deref(dev->name), sector);
2056         btrfs_bio_counter_dec(fs_info);
2057         bio_put(bio);
2058         return 0;
2059 }
2060 
2061 int repair_eb_io_failure(struct btrfs_fs_info *fs_info,
2062                          struct extent_buffer *eb, int mirror_num)
2063 {
2064         u64 start = eb->start;
2065         unsigned long i, num_pages = num_extent_pages(eb->start, eb->len);
2066         int ret = 0;
2067 
2068         if (sb_rdonly(fs_info->sb))
2069                 return -EROFS;
2070 
2071         for (i = 0; i < num_pages; i++) {
2072                 struct page *p = eb->pages[i];
2073 
2074                 ret = repair_io_failure(fs_info, 0, start, PAGE_SIZE, start, p,
2075                                         start - page_offset(p), mirror_num);
2076                 if (ret)
2077                         break;
2078                 start += PAGE_SIZE;
2079         }
2080 
2081         return ret;
2082 }
2083 
2084 /*
2085  * each time an IO finishes, we do a fast check in the IO failure tree
2086  * to see if we need to process or clean up an io_failure_record
2087  */
2088 int clean_io_failure(struct btrfs_fs_info *fs_info,
2089                      struct extent_io_tree *failure_tree,
2090                      struct extent_io_tree *io_tree, u64 start,
2091                      struct page *page, u64 ino, unsigned int pg_offset)
2092 {
2093         u64 private;
2094         struct io_failure_record *failrec;
2095         struct extent_state *state;
2096         int num_copies;
2097         int ret;
2098 
2099         private = 0;
2100         ret = count_range_bits(failure_tree, &private, (u64)-1, 1,
2101                                EXTENT_DIRTY, 0);
2102         if (!ret)
2103                 return 0;
2104 
2105         ret = get_state_failrec(failure_tree, start, &failrec);
2106         if (ret)
2107                 return 0;
2108 
2109         BUG_ON(!failrec->this_mirror);
2110 
2111         if (failrec->in_validation) {
2112                 /* there was no real error, just free the record */
2113                 btrfs_debug(fs_info,
2114                         "clean_io_failure: freeing dummy error at %llu",
2115                         failrec->start);
2116                 goto out;
2117         }
2118         if (sb_rdonly(fs_info->sb))
2119                 goto out;
2120 
2121         spin_lock(&io_tree->lock);
2122         state = find_first_extent_bit_state(io_tree,
2123                                             failrec->start,
2124                                             EXTENT_LOCKED);
2125         spin_unlock(&io_tree->lock);
2126 
2127         if (state && state->start <= failrec->start &&
2128             state->end >= failrec->start + failrec->len - 1) {
2129                 num_copies = btrfs_num_copies(fs_info, failrec->logical,
2130                                               failrec->len);
2131                 if (num_copies > 1)  {
2132                         repair_io_failure(fs_info, ino, start, failrec->len,
2133                                           failrec->logical, page, pg_offset,
2134                                           failrec->failed_mirror);
2135                 }
2136         }
2137 
2138 out:
2139         free_io_failure(failure_tree, io_tree, failrec);
2140 
2141         return 0;
2142 }
2143 
2144 /*
2145  * Can be called when
2146  * - hold extent lock
2147  * - under ordered extent
2148  * - the inode is freeing
2149  */
2150 void btrfs_free_io_failure_record(struct btrfs_inode *inode, u64 start, u64 end)
2151 {
2152         struct extent_io_tree *failure_tree = &inode->io_failure_tree;
2153         struct io_failure_record *failrec;
2154         struct extent_state *state, *next;
2155 
2156         if (RB_EMPTY_ROOT(&failure_tree->state))
2157                 return;
2158 
2159         spin_lock(&failure_tree->lock);
2160         state = find_first_extent_bit_state(failure_tree, start, EXTENT_DIRTY);
2161         while (state) {
2162                 if (state->start > end)
2163                         break;
2164 
2165                 ASSERT(state->end <= end);
2166 
2167                 next = next_state(state);
2168 
2169                 failrec = state->failrec;
2170                 free_extent_state(state);
2171                 kfree(failrec);
2172 
2173                 state = next;
2174         }
2175         spin_unlock(&failure_tree->lock);
2176 }
2177 
2178 int btrfs_get_io_failure_record(struct inode *inode, u64 start, u64 end,
2179                 struct io_failure_record **failrec_ret)
2180 {
2181         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
2182         struct io_failure_record *failrec;
2183         struct extent_map *em;
2184         struct extent_io_tree *failure_tree = &BTRFS_I(inode)->io_failure_tree;
2185         struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;
2186         struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
2187         int ret;
2188         u64 logical;
2189 
2190         ret = get_state_failrec(failure_tree, start, &failrec);
2191         if (ret) {
2192                 failrec = kzalloc(sizeof(*failrec), GFP_NOFS);
2193                 if (!failrec)
2194                         return -ENOMEM;
2195 
2196                 failrec->start = start;
2197                 failrec->len = end - start + 1;
2198                 failrec->this_mirror = 0;
2199                 failrec->bio_flags = 0;
2200                 failrec->in_validation = 0;
2201 
2202                 read_lock(&em_tree->lock);
2203                 em = lookup_extent_mapping(em_tree, start, failrec->len);
2204                 if (!em) {
2205                         read_unlock(&em_tree->lock);
2206                         kfree(failrec);
2207                         return -EIO;
2208                 }
2209 
2210                 if (em->start > start || em->start + em->len <= start) {
2211                         free_extent_map(em);
2212                         em = NULL;
2213                 }
2214                 read_unlock(&em_tree->lock);
2215                 if (!em) {
2216                         kfree(failrec);
2217                         return -EIO;
2218                 }
2219 
2220                 logical = start - em->start;
2221                 logical = em->block_start + logical;
2222                 if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
2223                         logical = em->block_start;
2224                         failrec->bio_flags = EXTENT_BIO_COMPRESSED;
2225                         extent_set_compress_type(&failrec->bio_flags,
2226                                                  em->compress_type);
2227                 }
2228 
2229                 btrfs_debug(fs_info,
2230                         "Get IO Failure Record: (new) logical=%llu, start=%llu, len=%llu",
2231                         logical, start, failrec->len);
2232 
2233                 failrec->logical = logical;
2234                 free_extent_map(em);
2235 
2236                 /* set the bits in the private failure tree */
2237                 ret = set_extent_bits(failure_tree, start, end,
2238                                         EXTENT_LOCKED | EXTENT_DIRTY);
2239                 if (ret >= 0)
2240                         ret = set_state_failrec(failure_tree, start, failrec);
2241                 /* set the bits in the inode's tree */
2242                 if (ret >= 0)
2243                         ret = set_extent_bits(tree, start, end, EXTENT_DAMAGED);
2244                 if (ret < 0) {
2245                         kfree(failrec);
2246                         return ret;
2247                 }
2248         } else {
2249                 btrfs_debug(fs_info,
2250                         "Get IO Failure Record: (found) logical=%llu, start=%llu, len=%llu, validation=%d",
2251                         failrec->logical, failrec->start, failrec->len,
2252                         failrec->in_validation);
2253                 /*
2254                  * when data can be on disk more than twice, add to failrec here
2255                  * (e.g. with a list for failed_mirror) to make
2256                  * clean_io_failure() clean all those errors at once.
2257                  */
2258         }
2259 
2260         *failrec_ret = failrec;
2261 
2262         return 0;
2263 }
2264 
2265 bool btrfs_check_repairable(struct inode *inode, unsigned failed_bio_pages,
2266                            struct io_failure_record *failrec, int failed_mirror)
2267 {
2268         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
2269         int num_copies;
2270 
2271         num_copies = btrfs_num_copies(fs_info, failrec->logical, failrec->len);
2272         if (num_copies == 1) {
2273                 /*
2274                  * we only have a single copy of the data, so don't bother with
2275                  * all the retry and error correction code that follows. no
2276                  * matter what the error is, it is very likely to persist.
2277                  */
2278                 btrfs_debug(fs_info,
2279                         "Check Repairable: cannot repair, num_copies=%d, next_mirror %d, failed_mirror %d",
2280                         num_copies, failrec->this_mirror, failed_mirror);
2281                 return false;
2282         }
2283 
2284         /*
2285          * there are two premises:
2286          *      a) deliver good data to the caller
2287          *      b) correct the bad sectors on disk
2288          */
2289         if (failed_bio_pages > 1) {
2290                 /*
2291                  * to fulfill b), we need to know the exact failing sectors, as
2292                  * we don't want to rewrite any more than the failed ones. thus,
2293                  * we need separate read requests for the failed bio
2294                  *
2295                  * if the following BUG_ON triggers, our validation request got
2296                  * merged. we need separate requests for our algorithm to work.
2297                  */
2298                 BUG_ON(failrec->in_validation);
2299                 failrec->in_validation = 1;
2300                 failrec->this_mirror = failed_mirror;
2301         } else {
2302                 /*
2303                  * we're ready to fulfill a) and b) alongside. get a good copy
2304                  * of the failed sector and if we succeed, we have setup
2305                  * everything for repair_io_failure to do the rest for us.
2306                  */
2307                 if (failrec->in_validation) {
2308                         BUG_ON(failrec->this_mirror != failed_mirror);
2309                         failrec->in_validation = 0;
2310                         failrec->this_mirror = 0;
2311                 }
2312                 failrec->failed_mirror = failed_mirror;
2313                 failrec->this_mirror++;
2314                 if (failrec->this_mirror == failed_mirror)
2315                         failrec->this_mirror++;
2316         }
2317 
2318         if (failrec->this_mirror > num_copies) {
2319                 btrfs_debug(fs_info,
2320                         "Check Repairable: (fail) num_copies=%d, next_mirror %d, failed_mirror %d",
2321                         num_copies, failrec->this_mirror, failed_mirror);
2322                 return false;
2323         }
2324 
2325         return true;
2326 }
2327 
2328 
2329 struct bio *btrfs_create_repair_bio(struct inode *inode, struct bio *failed_bio,
2330                                     struct io_failure_record *failrec,
2331                                     struct page *page, int pg_offset, int icsum,
2332                                     bio_end_io_t *endio_func, void *data)
2333 {
2334         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
2335         struct bio *bio;
2336         struct btrfs_io_bio *btrfs_failed_bio;
2337         struct btrfs_io_bio *btrfs_bio;
2338 
2339         bio = btrfs_io_bio_alloc(1);
2340         bio->bi_end_io = endio_func;
2341         bio->bi_iter.bi_sector = failrec->logical >> 9;
2342         bio_set_dev(bio, fs_info->fs_devices->latest_bdev);
2343         bio->bi_iter.bi_size = 0;
2344         bio->bi_private = data;
2345 
2346         btrfs_failed_bio = btrfs_io_bio(failed_bio);
2347         if (btrfs_failed_bio->csum) {
2348                 u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
2349 
2350                 btrfs_bio = btrfs_io_bio(bio);
2351                 btrfs_bio->csum = btrfs_bio->csum_inline;
2352                 icsum *= csum_size;
2353                 memcpy(btrfs_bio->csum, btrfs_failed_bio->csum + icsum,
2354                        csum_size);
2355         }
2356 
2357         bio_add_page(bio, page, failrec->len, pg_offset);
2358 
2359         return bio;
2360 }
2361 
2362 /*
2363  * this is a generic handler for readpage errors (default
2364  * readpage_io_failed_hook). if other copies exist, read those and write back
2365  * good data to the failed position. does not investigate in remapping the
2366  * failed extent elsewhere, hoping the device will be smart enough to do this as
2367  * needed
2368  */
2369 
2370 static int bio_readpage_error(struct bio *failed_bio, u64 phy_offset,
2371                               struct page *page, u64 start, u64 end,
2372                               int failed_mirror)
2373 {
2374         struct io_failure_record *failrec;
2375         struct inode *inode = page->mapping->host;
2376         struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;
2377         struct extent_io_tree *failure_tree = &BTRFS_I(inode)->io_failure_tree;
2378         struct bio *bio;
2379         int read_mode = 0;
2380         blk_status_t status;
2381         int ret;
2382         unsigned failed_bio_pages = bio_pages_all(failed_bio);
2383 
2384         BUG_ON(bio_op(failed_bio) == REQ_OP_WRITE);
2385 
2386         ret = btrfs_get_io_failure_record(inode, start, end, &failrec);
2387         if (ret)
2388                 return ret;
2389 
2390         if (!btrfs_check_repairable(inode, failed_bio_pages, failrec,
2391                                     failed_mirror)) {
2392                 free_io_failure(failure_tree, tree, failrec);
2393                 return -EIO;
2394         }
2395 
2396         if (failed_bio_pages > 1)
2397                 read_mode |= REQ_FAILFAST_DEV;
2398 
2399         phy_offset >>= inode->i_sb->s_blocksize_bits;
2400         bio = btrfs_create_repair_bio(inode, failed_bio, failrec, page,
2401                                       start - page_offset(page),
2402                                       (int)phy_offset, failed_bio->bi_end_io,
2403                                       NULL);
2404         bio_set_op_attrs(bio, REQ_OP_READ, read_mode);
2405 
2406         btrfs_debug(btrfs_sb(inode->i_sb),
2407                 "Repair Read Error: submitting new read[%#x] to this_mirror=%d, in_validation=%d",
2408                 read_mode, failrec->this_mirror, failrec->in_validation);
2409 
2410         status = tree->ops->submit_bio_hook(tree->private_data, bio, failrec->this_mirror,
2411                                          failrec->bio_flags, 0);
2412         if (status) {
2413                 free_io_failure(failure_tree, tree, failrec);
2414                 bio_put(bio);
2415                 ret = blk_status_to_errno(status);
2416         }
2417 
2418         return ret;
2419 }
2420 
2421 /* lots and lots of room for performance fixes in the end_bio funcs */
2422 
2423 void end_extent_writepage(struct page *page, int err, u64 start, u64 end)
2424 {
2425         int uptodate = (err == 0);
2426         struct extent_io_tree *tree;
2427         int ret = 0;
2428 
2429         tree = &BTRFS_I(page->mapping->host)->io_tree;
2430 
2431         if (tree->ops && tree->ops->writepage_end_io_hook)
2432                 tree->ops->writepage_end_io_hook(page, start, end, NULL,
2433                                 uptodate);
2434 
2435         if (!uptodate) {
2436                 ClearPageUptodate(page);
2437                 SetPageError(page);
2438                 ret = err < 0 ? err : -EIO;
2439                 mapping_set_error(page->mapping, ret);
2440         }
2441 }
2442 
2443 /*
2444  * after a writepage IO is done, we need to:
2445  * clear the uptodate bits on error
2446  * clear the writeback bits in the extent tree for this IO
2447  * end_page_writeback if the page has no more pending IO
2448  *
2449  * Scheduling is not allowed, so the extent state tree is expected
2450  * to have one and only one object corresponding to this IO.
2451  */
2452 static void end_bio_extent_writepage(struct bio *bio)
2453 {
2454         int error = blk_status_to_errno(bio->bi_status);
2455         struct bio_vec *bvec;
2456         u64 start;
2457         u64 end;
2458         int i;
2459 
2460         ASSERT(!bio_flagged(bio, BIO_CLONED));
2461         bio_for_each_segment_all(bvec, bio, i) {
2462                 struct page *page = bvec->bv_page;
2463                 struct inode *inode = page->mapping->host;
2464                 struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
2465 
2466                 /* We always issue full-page reads, but if some block
2467                  * in a page fails to read, blk_update_request() will
2468                  * advance bv_offset and adjust bv_len to compensate.
2469                  * Print a warning for nonzero offsets, and an error
2470                  * if they don't add up to a full page.  */
2471                 if (bvec->bv_offset || bvec->bv_len != PAGE_SIZE) {
2472                         if (bvec->bv_offset + bvec->bv_len != PAGE_SIZE)
2473                                 btrfs_err(fs_info,
2474                                    "partial page write in btrfs with offset %u and length %u",
2475                                         bvec->bv_offset, bvec->bv_len);
2476                         else
2477                                 btrfs_info(fs_info,
2478                                    "incomplete page write in btrfs with offset %u and length %u",
2479                                         bvec->bv_offset, bvec->bv_len);
2480                 }
2481 
2482                 start = page_offset(page);
2483                 end = start + bvec->bv_offset + bvec->bv_len - 1;
2484 
2485                 end_extent_writepage(page, error, start, end);
2486                 end_page_writeback(page);
2487         }
2488 
2489         bio_put(bio);
2490 }
2491 
2492 static void
2493 endio_readpage_release_extent(struct extent_io_tree *tree, u64 start, u64 len,
2494                               int uptodate)
2495 {
2496         struct extent_state *cached = NULL;
2497         u64 end = start + len - 1;
2498 
2499         if (uptodate && tree->track_uptodate)
2500                 set_extent_uptodate(tree, start, end, &cached, GFP_ATOMIC);
2501         unlock_extent_cached_atomic(tree, start, end, &cached);
2502 }
2503 
2504 /*
2505  * after a readpage IO is done, we need to:
2506  * clear the uptodate bits on error
2507  * set the uptodate bits if things worked
2508  * set the page up to date if all extents in the tree are uptodate
2509  * clear the lock bit in the extent tree
2510  * unlock the page if there are no other extents locked for it
2511  *
2512  * Scheduling is not allowed, so the extent state tree is expected
2513  * to have one and only one object corresponding to this IO.
2514  */
2515 static void end_bio_extent_readpage(struct bio *bio)
2516 {
2517         struct bio_vec *bvec;
2518         int uptodate = !bio->bi_status;
2519         struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
2520         struct extent_io_tree *tree, *failure_tree;
2521         u64 offset = 0;
2522         u64 start;
2523         u64 end;
2524         u64 len;
2525         u64 extent_start = 0;
2526         u64 extent_len = 0;
2527         int mirror;
2528         int ret;
2529         int i;
2530 
2531         ASSERT(!bio_flagged(bio, BIO_CLONED));
2532         bio_for_each_segment_all(bvec, bio, i) {
2533                 struct page *page = bvec->bv_page;
2534                 struct inode *inode = page->mapping->host;
2535                 struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
2536 
2537                 btrfs_debug(fs_info,
2538                         "end_bio_extent_readpage: bi_sector=%llu, err=%d, mirror=%u",
2539                         (u64)bio->bi_iter.bi_sector, bio->bi_status,
2540                         io_bio->mirror_num);
2541                 tree = &BTRFS_I(inode)->io_tree;
2542                 failure_tree = &BTRFS_I(inode)->io_failure_tree;
2543 
2544                 /* We always issue full-page reads, but if some block
2545                  * in a page fails to read, blk_update_request() will
2546                  * advance bv_offset and adjust bv_len to compensate.
2547                  * Print a warning for nonzero offsets, and an error
2548                  * if they don't add up to a full page.  */
2549                 if (bvec->bv_offset || bvec->bv_len != PAGE_SIZE) {
2550                         if (bvec->bv_offset + bvec->bv_len != PAGE_SIZE)
2551                                 btrfs_err(fs_info,
2552                                         "partial page read in btrfs with offset %u and length %u",
2553                                         bvec->bv_offset, bvec->bv_len);
2554                         else
2555                                 btrfs_info(fs_info,
2556                                         "incomplete page read in btrfs with offset %u and length %u",
2557                                         bvec->bv_offset, bvec->bv_len);
2558                 }
2559 
2560                 start = page_offset(page);
2561                 end = start + bvec->bv_offset + bvec->bv_len - 1;
2562                 len = bvec->bv_len;
2563 
2564                 mirror = io_bio->mirror_num;
2565                 if (likely(uptodate && tree->ops)) {
2566                         ret = tree->ops->readpage_end_io_hook(io_bio, offset,
2567                                                               page, start, end,
2568                                                               mirror);
2569                         if (ret)
2570                                 uptodate = 0;
2571                         else
2572                                 clean_io_failure(BTRFS_I(inode)->root->fs_info,
2573                                                  failure_tree, tree, start,
2574                                                  page,
2575                                                  btrfs_ino(BTRFS_I(inode)), 0);
2576                 }
2577 
2578                 if (likely(uptodate))
2579                         goto readpage_ok;
2580 
2581                 if (tree->ops) {
2582                         ret = tree->ops->readpage_io_failed_hook(page, mirror);
2583                         if (ret == -EAGAIN) {
2584                                 /*
2585                                  * Data inode's readpage_io_failed_hook() always
2586                                  * returns -EAGAIN.
2587                                  *
2588                                  * The generic bio_readpage_error handles errors
2589                                  * the following way: If possible, new read
2590                                  * requests are created and submitted and will
2591                                  * end up in end_bio_extent_readpage as well (if
2592                                  * we're lucky, not in the !uptodate case). In
2593                                  * that case it returns 0 and we just go on with
2594                                  * the next page in our bio. If it can't handle
2595                                  * the error it will return -EIO and we remain
2596                                  * responsible for that page.
2597                                  */
2598                                 ret = bio_readpage_error(bio, offset, page,
2599                                                          start, end, mirror);
2600                                 if (ret == 0) {
2601                                         uptodate = !bio->bi_status;
2602                                         offset += len;
2603                                         continue;
2604                                 }
2605                         }
2606 
2607                         /*
2608                          * metadata's readpage_io_failed_hook() always returns
2609                          * -EIO and fixes nothing.  -EIO is also returned if
2610                          * data inode error could not be fixed.
2611                          */
2612                         ASSERT(ret == -EIO);
2613                 }
2614 readpage_ok:
2615                 if (likely(uptodate)) {
2616                         loff_t i_size = i_size_read(inode);
2617                         pgoff_t end_index = i_size >> PAGE_SHIFT;
2618                         unsigned off;
2619 
2620                         /* Zero out the end if this page straddles i_size */
2621                         off = i_size & (PAGE_SIZE-1);
2622                         if (page->index == end_index && off)
2623                                 zero_user_segment(page, off, PAGE_SIZE);
2624                         SetPageUptodate(page);
2625                 } else {
2626                         ClearPageUptodate(page);
2627                         SetPageError(page);
2628                 }
2629                 unlock_page(page);
2630                 offset += len;
2631 
2632                 if (unlikely(!uptodate)) {
2633                         if (extent_len) {
2634                                 endio_readpage_release_extent(tree,
2635                                                               extent_start,
2636                                                               extent_len, 1);
2637                                 extent_start = 0;
2638                                 extent_len = 0;
2639                         }
2640                         endio_readpage_release_extent(tree, start,
2641                                                       end - start + 1, 0);
2642                 } else if (!extent_len) {
2643                         extent_start = start;
2644                         extent_len = end + 1 - start;
2645                 } else if (extent_start + extent_len == start) {
2646                         extent_len += end + 1 - start;
2647                 } else {
2648                         endio_readpage_release_extent(tree, extent_start,
2649                                                       extent_len, uptodate);
2650                         extent_start = start;
2651                         extent_len = end + 1 - start;
2652                 }
2653         }
2654 
2655         if (extent_len)
2656                 endio_readpage_release_extent(tree, extent_start, extent_len,
2657                                               uptodate);
2658         if (io_bio->end_io)
2659                 io_bio->end_io(io_bio, blk_status_to_errno(bio->bi_status));
2660         bio_put(bio);
2661 }
2662 
2663 /*
2664  * Initialize the members up to but not including 'bio'. Use after allocating a
2665  * new bio by bio_alloc_bioset as it does not initialize the bytes outside of
2666  * 'bio' because use of __GFP_ZERO is not supported.
2667  */
2668 static inline void btrfs_io_bio_init(struct btrfs_io_bio *btrfs_bio)
2669 {
2670         memset(btrfs_bio, 0, offsetof(struct btrfs_io_bio, bio));
2671 }
2672 
2673 /*
2674  * The following helpers allocate a bio. As it's backed by a bioset, it'll
2675  * never fail.  We're returning a bio right now but you can call btrfs_io_bio
2676  * for the appropriate container_of magic
2677  */
2678 struct bio *btrfs_bio_alloc(struct block_device *bdev, u64 first_byte)
2679 {
2680         struct bio *bio;
2681 
2682         bio = bio_alloc_bioset(GFP_NOFS, BIO_MAX_PAGES, btrfs_bioset);
2683         bio_set_dev(bio, bdev);
2684         bio->bi_iter.bi_sector = first_byte >> 9;
2685         btrfs_io_bio_init(btrfs_io_bio(bio));
2686         return bio;
2687 }
2688 
2689 struct bio *btrfs_bio_clone(struct bio *bio)
2690 {
2691         struct btrfs_io_bio *btrfs_bio;
2692         struct bio *new;
2693 
2694         /* Bio allocation backed by a bioset does not fail */
2695         new = bio_clone_fast(bio, GFP_NOFS, btrfs_bioset);
2696         btrfs_bio = btrfs_io_bio(new);
2697         btrfs_io_bio_init(btrfs_bio);
2698         btrfs_bio->iter = bio->bi_iter;
2699         return new;
2700 }
2701 
2702 struct bio *btrfs_io_bio_alloc(unsigned int nr_iovecs)
2703 {
2704         struct bio *bio;
2705 
2706         /* Bio allocation backed by a bioset does not fail */
2707         bio = bio_alloc_bioset(GFP_NOFS, nr_iovecs, btrfs_bioset);
2708         btrfs_io_bio_init(btrfs_io_bio(bio));
2709         return bio;
2710 }
2711 
2712 struct bio *btrfs_bio_clone_partial(struct bio *orig, int offset, int size)
2713 {
2714         struct bio *bio;
2715         struct btrfs_io_bio *btrfs_bio;
2716 
2717         /* this will never fail when it's backed by a bioset */
2718         bio = bio_clone_fast(orig, GFP_NOFS, btrfs_bioset);
2719         ASSERT(bio);
2720 
2721         btrfs_bio = btrfs_io_bio(bio);
2722         btrfs_io_bio_init(btrfs_bio);
2723 
2724         bio_trim(bio, offset >> 9, size >> 9);
2725         btrfs_bio->iter = bio->bi_iter;
2726         return bio;
2727 }
2728 
2729 static int __must_check submit_one_bio(struct bio *bio, int mirror_num,
2730                                        unsigned long bio_flags)
2731 {
2732         blk_status_t ret = 0;
2733         struct bio_vec *bvec = bio_last_bvec_all(bio);
2734         struct page *page = bvec->bv_page;
2735         struct extent_io_tree *tree = bio->bi_private;
2736         u64 start;
2737 
2738         start = page_offset(page) + bvec->bv_offset;
2739 
2740         bio->bi_private = NULL;
2741 
2742         if (tree->ops)
2743                 ret = tree->ops->submit_bio_hook(tree->private_data, bio,
2744                                            mirror_num, bio_flags, start);
2745         else
2746                 btrfsic_submit_bio(bio);
2747 
2748         return blk_status_to_errno(ret);
2749 }
2750 
2751 /*
2752  * @opf:        bio REQ_OP_* and REQ_* flags as one value
2753  * @tree:       tree so we can call our merge_bio hook
2754  * @wbc:        optional writeback control for io accounting
2755  * @page:       page to add to the bio
2756  * @pg_offset:  offset of the new bio or to check whether we are adding
2757  *              a contiguous page to the previous one
2758  * @size:       portion of page that we want to write
2759  * @offset:     starting offset in the page
2760  * @bdev:       attach newly created bios to this bdev
2761  * @bio_ret:    must be valid pointer, newly allocated bio will be stored there
2762  * @end_io_func:     end_io callback for new bio
2763  * @mirror_num:      desired mirror to read/write
2764  * @prev_bio_flags:  flags of previous bio to see if we can merge the current one
2765  * @bio_flags:  flags of the current bio to see if we can merge them
2766  */
2767 static int submit_extent_page(unsigned int opf, struct extent_io_tree *tree,
2768                               struct writeback_control *wbc,
2769                               struct page *page, u64 offset,
2770                               size_t size, unsigned long pg_offset,
2771                               struct block_device *bdev,
2772                               struct bio **bio_ret,
2773                               bio_end_io_t end_io_func,
2774                               int mirror_num,
2775                               unsigned long prev_bio_flags,
2776                               unsigned long bio_flags,
2777                               bool force_bio_submit)
2778 {
2779         int ret = 0;
2780         struct bio *bio;
2781         size_t page_size = min_t(size_t, size, PAGE_SIZE);
2782         sector_t sector = offset >> 9;
2783 
2784         ASSERT(bio_ret);
2785 
2786         if (*bio_ret) {
2787                 bool contig;
2788                 bool can_merge = true;
2789 
2790                 bio = *bio_ret;
2791                 if (prev_bio_flags & EXTENT_BIO_COMPRESSED)
2792                         contig = bio->bi_iter.bi_sector == sector;
2793                 else
2794                         contig = bio_end_sector(bio) == sector;
2795 
2796                 if (tree->ops && tree->ops->merge_bio_hook(page, offset,
2797                                         page_size, bio, bio_flags))
2798                         can_merge = false;
2799 
2800                 if (prev_bio_flags != bio_flags || !contig || !can_merge ||
2801                     force_bio_submit ||
2802                     bio_add_page(bio, page, page_size, pg_offset) < page_size) {
2803                         ret = submit_one_bio(bio, mirror_num, prev_bio_flags);
2804                         if (ret < 0) {
2805                                 *bio_ret = NULL;
2806                                 return ret;
2807                         }
2808                         bio = NULL;
2809                 } else {
2810                         if (wbc)
2811                                 wbc_account_io(wbc, page, page_size);
2812                         return 0;
2813                 }
2814         }
2815 
2816         bio = btrfs_bio_alloc(bdev, offset);
2817         bio_add_page(bio, page, page_size, pg_offset);
2818         bio->bi_end_io = end_io_func;
2819         bio->bi_private = tree;
2820         bio->bi_write_hint = page->mapping->host->i_write_hint;
2821         bio->bi_opf = opf;
2822         if (wbc) {
2823                 wbc_init_bio(wbc, bio);
2824                 wbc_account_io(wbc, page, page_size);
2825         }
2826 
2827         *bio_ret = bio;
2828 
2829         return ret;
2830 }
2831 
2832 static void attach_extent_buffer_page(struct extent_buffer *eb,
2833                                       struct page *page)
2834 {
2835         if (!PagePrivate(page)) {
2836                 SetPagePrivate(page);
2837                 get_page(page);
2838                 set_page_private(page, (unsigned long)eb);
2839         } else {
2840                 WARN_ON(page->private != (unsigned long)eb);
2841         }
2842 }
2843 
2844 void set_page_extent_mapped(struct page *page)
2845 {
2846         if (!PagePrivate(page)) {
2847                 SetPagePrivate(page);
2848                 get_page(page);
2849                 set_page_private(page, EXTENT_PAGE_PRIVATE);
2850         }
2851 }
2852 
2853 static struct extent_map *
2854 __get_extent_map(struct inode *inode, struct page *page, size_t pg_offset,
2855                  u64 start, u64 len, get_extent_t *get_extent,
2856                  struct extent_map **em_cached)
2857 {
2858         struct extent_map *em;
2859 
2860         if (em_cached && *em_cached) {
2861                 em = *em_cached;
2862                 if (extent_map_in_tree(em) && start >= em->start &&
2863                     start < extent_map_end(em)) {
2864                         refcount_inc(&em->refs);
2865                         return em;
2866                 }
2867 
2868                 free_extent_map(em);
2869                 *em_cached = NULL;
2870         }
2871 
2872         em = get_extent(BTRFS_I(inode), page, pg_offset, start, len, 0);
2873         if (em_cached && !IS_ERR_OR_NULL(em)) {
2874                 BUG_ON(*em_cached);
2875                 refcount_inc(&em->refs);
2876                 *em_cached = em;
2877         }
2878         return em;
2879 }
2880 /*
2881  * basic readpage implementation.  Locked extent state structs are inserted
2882  * into the tree that are removed when the IO is done (by the end_io
2883  * handlers)
2884  * XXX JDM: This needs looking at to ensure proper page locking
2885  * return 0 on success, otherwise return error
2886  */
2887 static int __do_readpage(struct extent_io_tree *tree,
2888                          struct page *page,
2889                          get_extent_t *get_extent,
2890                          struct extent_map **em_cached,
2891                          struct bio **bio, int mirror_num,
2892                          unsigned long *bio_flags, unsigned int read_flags,
2893                          u64 *prev_em_start)
2894 {
2895         struct inode *inode = page->mapping->host;
2896         u64 start = page_offset(page);
2897         const u64 end = start + PAGE_SIZE - 1;
2898         u64 cur = start;
2899         u64 extent_offset;
2900         u64 last_byte = i_size_read(inode);
2901         u64 block_start;
2902         u64 cur_end;
2903         struct extent_map *em;
2904         struct block_device *bdev;
2905         int ret = 0;
2906         int nr = 0;
2907         size_t pg_offset = 0;
2908         size_t iosize;
2909         size_t disk_io_size;
2910         size_t blocksize = inode->i_sb->s_blocksize;
2911         unsigned long this_bio_flag = 0;
2912 
2913         set_page_extent_mapped(page);
2914 
2915         if (!PageUptodate(page)) {
2916                 if (cleancache_get_page(page) == 0) {
2917                         BUG_ON(blocksize != PAGE_SIZE);
2918                         unlock_extent(tree, start, end);
2919                         goto out;
2920                 }
2921         }
2922 
2923         if (page->index == last_byte >> PAGE_SHIFT) {
2924                 char *userpage;
2925                 size_t zero_offset = last_byte & (PAGE_SIZE - 1);
2926 
2927                 if (zero_offset) {
2928                         iosize = PAGE_SIZE - zero_offset;
2929                         userpage = kmap_atomic(page);
2930                         memset(userpage + zero_offset, 0, iosize);
2931                         flush_dcache_page(page);
2932                         kunmap_atomic(userpage);
2933                 }
2934         }
2935         while (cur <= end) {
2936                 bool force_bio_submit = false;
2937                 u64 offset;
2938 
2939                 if (cur >= last_byte) {
2940                         char *userpage;
2941                         struct extent_state *cached = NULL;
2942 
2943                         iosize = PAGE_SIZE - pg_offset;
2944                         userpage = kmap_atomic(page);
2945                         memset(userpage + pg_offset, 0, iosize);
2946                         flush_dcache_page(page);
2947                         kunmap_atomic(userpage);
2948                         set_extent_uptodate(tree, cur, cur + iosize - 1,
2949                                             &cached, GFP_NOFS);
2950                         unlock_extent_cached(tree, cur,
2951                                              cur + iosize - 1, &cached);
2952                         break;
2953                 }
2954                 em = __get_extent_map(inode, page, pg_offset, cur,
2955                                       end - cur + 1, get_extent, em_cached);
2956                 if (IS_ERR_OR_NULL(em)) {
2957                         SetPageError(page);
2958                         unlock_extent(tree, cur, end);
2959                         break;
2960                 }
2961                 extent_offset = cur - em->start;
2962                 BUG_ON(extent_map_end(em) <= cur);
2963                 BUG_ON(end < cur);
2964 
2965                 if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
2966                         this_bio_flag |= EXTENT_BIO_COMPRESSED;
2967                         extent_set_compress_type(&this_bio_flag,
2968                                                  em->compress_type);
2969                 }
2970 
2971                 iosize = min(extent_map_end(em) - cur, end - cur + 1);
2972                 cur_end = min(extent_map_end(em) - 1, end);
2973                 iosize = ALIGN(iosize, blocksize);
2974                 if (this_bio_flag & EXTENT_BIO_COMPRESSED) {
2975                         disk_io_size = em->block_len;
2976                         offset = em->block_start;
2977                 } else {
2978                         offset = em->block_start + extent_offset;
2979                         disk_io_size = iosize;
2980                 }
2981                 bdev = em->bdev;
2982                 block_start = em->block_start;
2983                 if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
2984                         block_start = EXTENT_MAP_HOLE;
2985 
2986                 /*
2987                  * If we have a file range that points to a compressed extent
2988                  * and it's followed by a consecutive file range that points to
2989                  * to the same compressed extent (possibly with a different
2990                  * offset and/or length, so it either points to the whole extent
2991                  * or only part of it), we must make sure we do not submit a
2992                  * single bio to populate the pages for the 2 ranges because
2993                  * this makes the compressed extent read zero out the pages
2994                  * belonging to the 2nd range. Imagine the following scenario:
2995                  *
2996                  *  File layout
2997                  *  [0 - 8K]                     [8K - 24K]
2998                  *    |                               |
2999                  *    |                               |
3000                  * points to extent X,         points to extent X,
3001                  * offset 4K, length of 8K     offset 0, length 16K
3002                  *
3003                  * [extent X, compressed length = 4K uncompressed length = 16K]
3004                  *
3005                  * If the bio to read the compressed extent covers both ranges,
3006                  * it will decompress extent X into the pages belonging to the
3007                  * first range and then it will stop, zeroing out the remaining
3008                  * pages that belong to the other range that points to extent X.
3009                  * So here we make sure we submit 2 bios, one for the first
3010                  * range and another one for the third range. Both will target
3011                  * the same physical extent from disk, but we can't currently
3012                  * make the compressed bio endio callback populate the pages
3013                  * for both ranges because each compressed bio is tightly
3014                  * coupled with a single extent map, and each range can have
3015                  * an extent map with a different offset value relative to the
3016                  * uncompressed data of our extent and different lengths. This
3017                  * is a corner case so we prioritize correctness over
3018                  * non-optimal behavior (submitting 2 bios for the same extent).
3019                  */
3020                 if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags) &&
3021                     prev_em_start && *prev_em_start != (u64)-1 &&
3022                     *prev_em_start != em->orig_start)
3023                         force_bio_submit = true;
3024 
3025                 if (prev_em_start)
3026                         *prev_em_start = em->orig_start;
3027 
3028                 free_extent_map(em);
3029                 em = NULL;
3030 
3031                 /* we've found a hole, just zero and go on */
3032                 if (block_start == EXTENT_MAP_HOLE) {
3033                         char *userpage;
3034                         struct extent_state *cached = NULL;
3035 
3036                         userpage = kmap_atomic(page);
3037                         memset(userpage + pg_offset, 0, iosize);
3038                         flush_dcache_page(page);
3039                         kunmap_atomic(userpage);
3040 
3041                         set_extent_uptodate(tree, cur, cur + iosize - 1,
3042                                             &cached, GFP_NOFS);
3043                         unlock_extent_cached(tree, cur,
3044                                              cur + iosize - 1, &cached);
3045                         cur = cur + iosize;
3046                         pg_offset += iosize;
3047                         continue;
3048                 }
3049                 /* the get_extent function already copied into the page */
3050                 if (test_range_bit(tree, cur, cur_end,
3051                                    EXTENT_UPTODATE, 1, NULL)) {
3052                         check_page_uptodate(tree, page);
3053                         unlock_extent(tree, cur, cur + iosize - 1);
3054                         cur = cur + iosize;
3055                         pg_offset += iosize;
3056                         continue;
3057                 }
3058                 /* we have an inline extent but it didn't get marked up
3059                  * to date.  Error out
3060                  */
3061                 if (block_start == EXTENT_MAP_INLINE) {
3062                         SetPageError(page);
3063                         unlock_extent(tree, cur, cur + iosize - 1);
3064                         cur = cur + iosize;
3065                         pg_offset += iosize;
3066                         continue;
3067                 }
3068 
3069                 ret = submit_extent_page(REQ_OP_READ | read_flags, tree, NULL,
3070                                          page, offset, disk_io_size,
3071                                          pg_offset, bdev, bio,
3072                                          end_bio_extent_readpage, mirror_num,
3073                                          *bio_flags,
3074                                          this_bio_flag,
3075                                          force_bio_submit);
3076                 if (!ret) {
3077                         nr++;
3078                         *bio_flags = this_bio_flag;
3079                 } else {
3080                         SetPageError(page);
3081                         unlock_extent(tree, cur, cur + iosize - 1);
3082                         goto out;
3083                 }
3084                 cur = cur + iosize;
3085                 pg_offset += iosize;
3086         }
3087 out:
3088         if (!nr) {
3089                 if (!PageError(page))
3090                         SetPageUptodate(page);
3091                 unlock_page(page);
3092         }
3093         return ret;
3094 }
3095 
3096 static inline void __do_contiguous_readpages(struct extent_io_tree *tree,
3097                                              struct page *pages[], int nr_pages,
3098                                              u64 start, u64 end,
3099                                              struct extent_map **em_cached,
3100                                              struct bio **bio,
3101                                              unsigned long *bio_flags,
3102                                              u64 *prev_em_start)
3103 {
3104         struct inode *inode;
3105         struct btrfs_ordered_extent *ordered;
3106         int index;
3107 
3108         inode = pages[0]->mapping->host;
3109         while (1) {
3110                 lock_extent(tree, start, end);
3111                 ordered = btrfs_lookup_ordered_range(BTRFS_I(inode), start,
3112                                                      end - start + 1);
3113                 if (!ordered)
3114                         break;
3115                 unlock_extent(tree, start, end);
3116                 btrfs_start_ordered_extent(inode, ordered, 1);
3117                 btrfs_put_ordered_extent(ordered);
3118         }
3119 
3120         for (index = 0; index < nr_pages; index++) {
3121                 __do_readpage(tree, pages[index], btrfs_get_extent, em_cached,
3122                                 bio, 0, bio_flags, 0, prev_em_start);
3123                 put_page(pages[index]);
3124         }
3125 }
3126 
3127 static void __extent_readpages(struct extent_io_tree *tree,
3128                                struct page *pages[],
3129                                int nr_pages,
3130                                struct extent_map **em_cached,
3131                                struct bio **bio, unsigned long *bio_flags,
3132                                u64 *prev_em_start)
3133 {
3134         u64 start = 0;
3135         u64 end = 0;
3136         u64 page_start;
3137         int index;
3138         int first_index = 0;
3139 
3140         for (index = 0; index < nr_pages; index++) {
3141                 page_start = page_offset(pages[index]);
3142                 if (!end) {
3143                         start = page_start;
3144                         end = start + PAGE_SIZE - 1;
3145                         first_index = index;
3146                 } else if (end + 1 == page_start) {
3147                         end += PAGE_SIZE;
3148                 } else {
3149                         __do_contiguous_readpages(tree, &pages[first_index],
3150                                                   index - first_index, start,
3151                                                   end, em_cached,
3152                                                   bio, bio_flags,
3153                                                   prev_em_start);
3154                         start = page_start;
3155                         end = start + PAGE_SIZE - 1;
3156                         first_index = index;
3157                 }
3158         }
3159 
3160         if (end)
3161                 __do_contiguous_readpages(tree, &pages[first_index],
3162                                           index - first_index, start,
3163                                           end, em_cached, bio,
3164                                           bio_flags, prev_em_start);
3165 }
3166 
3167 static int __extent_read_full_page(struct extent_io_tree *tree,
3168                                    struct page *page,
3169                                    get_extent_t *get_extent,
3170                                    struct bio **bio, int mirror_num,
3171                                    unsigned long *bio_flags,
3172                                    unsigned int read_flags)
3173 {
3174         struct inode *inode = page->mapping->host;
3175         struct btrfs_ordered_extent *ordered;
3176         u64 start = page_offset(page);
3177         u64 end = start + PAGE_SIZE - 1;
3178         int ret;
3179 
3180         while (1) {
3181                 lock_extent(tree, start, end);
3182                 ordered = btrfs_lookup_ordered_range(BTRFS_I(inode), start,
3183                                                 PAGE_SIZE);
3184                 if (!ordered)
3185                         break;
3186                 unlock_extent(tree, start, end);
3187                 btrfs_start_ordered_extent(inode, ordered, 1);
3188                 btrfs_put_ordered_extent(ordered);
3189         }
3190 
3191         ret = __do_readpage(tree, page, get_extent, NULL, bio, mirror_num,
3192                             bio_flags, read_flags, NULL);
3193         return ret;
3194 }
3195 
3196 int extent_read_full_page(struct extent_io_tree *tree, struct page *page,
3197                             get_extent_t *get_extent, int mirror_num)
3198 {
3199         struct bio *bio = NULL;
3200         unsigned long bio_flags = 0;
3201         int ret;
3202 
3203         ret = __extent_read_full_page(tree, page, get_extent, &bio, mirror_num,
3204                                       &bio_flags, 0);
3205         if (bio)
3206                 ret = submit_one_bio(bio, mirror_num, bio_flags);
3207         return ret;
3208 }
3209 
3210 static void update_nr_written(struct writeback_control *wbc,
3211                               unsigned long nr_written)
3212 {
3213         wbc->nr_to_write -= nr_written;
3214 }
3215 
3216 /*
3217  * helper for __extent_writepage, doing all of the delayed allocation setup.
3218  *
3219  * This returns 1 if our fill_delalloc function did all the work required
3220  * to write the page (copy into inline extent).  In this case the IO has
3221  * been started and the page is already unlocked.
3222  *
3223  * This returns 0 if all went well (page still locked)
3224  * This returns < 0 if there were errors (page still locked)
3225  */
3226 static noinline_for_stack int writepage_delalloc(struct inode *inode,
3227                               struct page *page, struct writeback_control *wbc,
3228                               struct extent_page_data *epd,
3229                               u64 delalloc_start,
3230                               unsigned long *nr_written)
3231 {
3232         struct extent_io_tree *tree = epd->tree;
3233         u64 page_end = delalloc_start + PAGE_SIZE - 1;
3234         u64 nr_delalloc;
3235         u64 delalloc_to_write = 0;
3236         u64 delalloc_end = 0;
3237         int ret;
3238         int page_started = 0;
3239 
3240         if (epd->extent_locked || !tree->ops || !tree->ops->fill_delalloc)
3241                 return 0;
3242 
3243         while (delalloc_end < page_end) {
3244                 nr_delalloc = find_lock_delalloc_range(inode, tree,
3245                                                page,
3246                                                &delalloc_start,
3247                                                &delalloc_end,
3248                                                BTRFS_MAX_EXTENT_SIZE);
3249                 if (nr_delalloc == 0) {
3250                         delalloc_start = delalloc_end + 1;
3251                         continue;
3252                 }
3253                 ret = tree->ops->fill_delalloc(inode, page,
3254                                                delalloc_start,
3255                                                delalloc_end,
3256                                                &page_started,
3257                                                nr_written, wbc);
3258                 /* File system has been set read-only */
3259                 if (ret) {
3260                         SetPageError(page);
3261                         /* fill_delalloc should be return < 0 for error
3262                          * but just in case, we use > 0 here meaning the
3263                          * IO is started, so we don't want to return > 0
3264                          * unless things are going well.
3265                          */
3266                         ret = ret < 0 ? ret : -EIO;
3267                         goto done;
3268                 }
3269                 /*
3270                  * delalloc_end is already one less than the total length, so
3271                  * we don't subtract one from PAGE_SIZE
3272                  */
3273                 delalloc_to_write += (delalloc_end - delalloc_start +
3274                                       PAGE_SIZE) >> PAGE_SHIFT;
3275                 delalloc_start = delalloc_end + 1;
3276         }
3277         if (wbc->nr_to_write < delalloc_to_write) {
3278                 int thresh = 8192;
3279 
3280                 if (delalloc_to_write < thresh * 2)
3281                         thresh = delalloc_to_write;
3282                 wbc->nr_to_write = min_t(u64, delalloc_to_write,
3283                                          thresh);
3284         }
3285 
3286         /* did the fill delalloc function already unlock and start
3287          * the IO?
3288          */
3289         if (page_started) {
3290                 /*
3291                  * we've unlocked the page, so we can't update
3292                  * the mapping's writeback index, just update
3293                  * nr_to_write.
3294                  */
3295                 wbc->nr_to_write -= *nr_written;
3296                 return 1;
3297         }
3298 
3299         ret = 0;
3300 
3301 done:
3302         return ret;
3303 }
3304 
3305 /*
3306  * helper for __extent_writepage.  This calls the writepage start hooks,
3307  * and does the loop to map the page into extents and bios.
3308  *
3309  * We return 1 if the IO is started and the page is unlocked,
3310  * 0 if all went well (page still locked)
3311  * < 0 if there were errors (page still locked)
3312  */
3313 static noinline_for_stack int __extent_writepage_io(struct inode *inode,
3314                                  struct page *page,
3315                                  struct writeback_control *wbc,
3316                                  struct extent_page_data *epd,
3317                                  loff_t i_size,
3318                                  unsigned long nr_written,
3319                                  unsigned int write_flags, int *nr_ret)
3320 {
3321         struct extent_io_tree *tree = epd->tree;
3322         u64 start = page_offset(page);
3323         u64 page_end = start + PAGE_SIZE - 1;
3324         u64 end;
3325         u64 cur = start;
3326         u64 extent_offset;
3327         u64 block_start;
3328         u64 iosize;
3329         struct extent_map *em;
3330         struct block_device *bdev;
3331         size_t pg_offset = 0;
3332         size_t blocksize;
3333         int ret = 0;
3334         int nr = 0;
3335         bool compressed;
3336 
3337         if (tree->ops && tree->ops->writepage_start_hook) {
3338                 ret = tree->ops->writepage_start_hook(page, start,
3339                                                       page_end);
3340                 if (ret) {
3341                         /* Fixup worker will requeue */
3342                         if (ret == -EBUSY)
3343                                 wbc->pages_skipped++;
3344                         else
3345                                 redirty_page_for_writepage(wbc, page);
3346 
3347                         update_nr_written(wbc, nr_written);
3348                         unlock_page(page);
3349                         return 1;
3350                 }
3351         }
3352 
3353         /*
3354          * we don't want to touch the inode after unlocking the page,
3355          * so we update the mapping writeback index now
3356          */
3357         update_nr_written(wbc, nr_written + 1);
3358 
3359         end = page_end;
3360         if (i_size <= start) {
3361                 if (tree->ops && tree->ops->writepage_end_io_hook)
3362                         tree->ops->writepage_end_io_hook(page, start,
3363                                                          page_end, NULL, 1);
3364                 goto done;
3365         }
3366 
3367         blocksize = inode->i_sb->s_blocksize;
3368 
3369         while (cur <= end) {
3370                 u64 em_end;
3371                 u64 offset;
3372 
3373                 if (cur >= i_size) {
3374                         if (tree->ops && tree->ops->writepage_end_io_hook)
3375                                 tree->ops->writepage_end_io_hook(page, cur,
3376                                                          page_end, NULL, 1);
3377                         break;
3378                 }
3379                 em = btrfs_get_extent(BTRFS_I(inode), page, pg_offset, cur,
3380                                      end - cur + 1, 1);
3381                 if (IS_ERR_OR_NULL(em)) {
3382                         SetPageError(page);
3383                         ret = PTR_ERR_OR_ZERO(em);
3384                         break;
3385                 }
3386 
3387                 extent_offset = cur - em->start;
3388                 em_end = extent_map_end(em);
3389                 BUG_ON(em_end <= cur);
3390                 BUG_ON(end < cur);
3391                 iosize = min(em_end - cur, end - cur + 1);
3392                 iosize = ALIGN(iosize, blocksize);
3393                 offset = em->block_start + extent_offset;
3394                 bdev = em->bdev;
3395                 block_start = em->block_start;
3396                 compressed = test_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
3397                 free_extent_map(em);
3398                 em = NULL;
3399 
3400                 /*
3401                  * compressed and inline extents are written through other
3402                  * paths in the FS
3403                  */
3404                 if (compressed || block_start == EXTENT_MAP_HOLE ||
3405                     block_start == EXTENT_MAP_INLINE) {
3406                         /*
3407                          * end_io notification does not happen here for
3408                          * compressed extents
3409                          */
3410                         if (!compressed && tree->ops &&
3411                             tree->ops->writepage_end_io_hook)
3412                                 tree->ops->writepage_end_io_hook(page, cur,
3413                                                          cur + iosize - 1,
3414                                                          NULL, 1);
3415                         else if (compressed) {
3416                                 /* we don't want to end_page_writeback on
3417                                  * a compressed extent.  this happens
3418                                  * elsewhere
3419                                  */
3420                                 nr++;
3421                         }
3422 
3423                         cur += iosize;
3424                         pg_offset += iosize;
3425                         continue;
3426                 }
3427 
3428                 set_range_writeback(tree, cur, cur + iosize - 1);
3429                 if (!PageWriteback(page)) {
3430                         btrfs_err(BTRFS_I(inode)->root->fs_info,
3431                                    "page %lu not writeback, cur %llu end %llu",
3432                                page->index, cur, end);
3433                 }
3434 
3435                 ret = submit_extent_page(REQ_OP_WRITE | write_flags, tree, wbc,
3436                                          page, offset, iosize, pg_offset,
3437                                          bdev, &epd->bio,
3438                                          end_bio_extent_writepage,
3439                                          0, 0, 0, false);
3440                 if (ret) {
3441                         SetPageError(page);
3442                         if (PageWriteback(page))
3443                                 end_page_writeback(page);
3444                 }
3445 
3446                 cur = cur + iosize;
3447                 pg_offset += iosize;
3448                 nr++;
3449         }
3450 done:
3451         *nr_ret = nr;
3452         return ret;
3453 }
3454 
3455 /*
3456  * the writepage semantics are similar to regular writepage.  extent
3457  * records are inserted to lock ranges in the tree, and as dirty areas
3458  * are found, they are marked writeback.  Then the lock bits are removed
3459  * and the end_io handler clears the writeback ranges
3460  */
3461 static int __extent_writepage(struct page *page, struct writeback_control *wbc,
3462                               struct extent_page_data *epd)
3463 {
3464         struct inode *inode = page->mapping->host;
3465         u64 start = page_offset(page);
3466         u64 page_end = start + PAGE_SIZE - 1;
3467         int ret;
3468         int nr = 0;
3469         size_t pg_offset = 0;
3470         loff_t i_size = i_size_read(inode);
3471         unsigned long end_index = i_size >> PAGE_SHIFT;
3472         unsigned int write_flags = 0;
3473         unsigned long nr_written = 0;
3474 
3475         write_flags = wbc_to_write_flags(wbc);
3476 
3477         trace___extent_writepage(page, inode, wbc);
3478 
3479         WARN_ON(!PageLocked(page));
3480 
3481         ClearPageError(page);
3482 
3483         pg_offset = i_size & (PAGE_SIZE - 1);
3484         if (page->index > end_index ||
3485            (page->index == end_index && !pg_offset)) {
3486                 page->mapping->a_ops->invalidatepage(page, 0, PAGE_SIZE);
3487                 unlock_page(page);
3488                 return 0;
3489         }
3490 
3491         if (page->index == end_index) {
3492                 char *userpage;
3493 
3494                 userpage = kmap_atomic(page);
3495                 memset(userpage + pg_offset, 0,
3496                        PAGE_SIZE - pg_offset);
3497                 kunmap_atomic(userpage);
3498                 flush_dcache_page(page);
3499         }
3500 
3501         pg_offset = 0;
3502 
3503         set_page_extent_mapped(page);
3504 
3505         ret = writepage_delalloc(inode, page, wbc, epd, start, &nr_written);
3506         if (ret == 1)
3507                 goto done_unlocked;
3508         if (ret)
3509                 goto done;
3510 
3511         ret = __extent_writepage_io(inode, page, wbc, epd,
3512                                     i_size, nr_written, write_flags, &nr);
3513         if (ret == 1)
3514                 goto done_unlocked;
3515 
3516 done:
3517         if (nr == 0) {
3518                 /* make sure the mapping tag for page dirty gets cleared */
3519                 set_page_writeback(page);
3520                 end_page_writeback(page);
3521         }
3522         if (PageError(page)) {
3523                 ret = ret < 0 ? ret : -EIO;
3524                 end_extent_writepage(page, ret, start, page_end);
3525         }
3526         unlock_page(page);
3527         return ret;
3528 
3529 done_unlocked:
3530         return 0;
3531 }
3532 
3533 void wait_on_extent_buffer_writeback(struct extent_buffer *eb)
3534 {
3535         wait_on_bit_io(&eb->bflags, EXTENT_BUFFER_WRITEBACK,
3536                        TASK_UNINTERRUPTIBLE);
3537 }
3538 
3539 static noinline_for_stack int
3540 lock_extent_buffer_for_io(struct extent_buffer *eb,
3541                           struct btrfs_fs_info *fs_info,
3542                           struct extent_page_data *epd)
3543 {
3544         unsigned long i, num_pages;
3545         int flush = 0;
3546         int ret = 0;
3547 
3548         if (!btrfs_try_tree_write_lock(eb)) {
3549                 flush = 1;
3550                 flush_write_bio(epd);
3551                 btrfs_tree_lock(eb);
3552         }
3553 
3554         if (test_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags)) {
3555                 btrfs_tree_unlock(eb);
3556                 if (!epd->sync_io)
3557                         return 0;
3558                 if (!flush) {
3559                         flush_write_bio(epd);
3560                         flush = 1;
3561                 }
3562                 while (1) {
3563                         wait_on_extent_buffer_writeback(eb);
3564                         btrfs_tree_lock(eb);
3565                         if (!test_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags))
3566                                 break;
3567                         btrfs_tree_unlock(eb);
3568                 }
3569         }
3570 
3571         /*
3572          * We need to do this to prevent races in people who check if the eb is
3573          * under IO since we can end up having no IO bits set for a short period
3574          * of time.
3575          */
3576         spin_lock(&eb->refs_lock);
3577         if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &eb->bflags)) {
3578                 set_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags);
3579                 spin_unlock(&eb->refs_lock);
3580                 btrfs_set_header_flag(eb, BTRFS_HEADER_FLAG_WRITTEN);
3581                 percpu_counter_add_batch(&fs_info->dirty_metadata_bytes,
3582                                          -eb->len,
3583                                          fs_info->dirty_metadata_batch);
3584                 ret = 1;
3585         } else {
3586                 spin_unlock(&eb->refs_lock);
3587         }
3588 
3589         btrfs_tree_unlock(eb);
3590 
3591         if (!ret)
3592                 return ret;
3593 
3594         num_pages = num_extent_pages(eb->start, eb->len);
3595         for (i = 0; i < num_pages; i++) {
3596                 struct page *p = eb->pages[i];
3597 
3598                 if (!trylock_page(p)) {
3599                         if (!flush) {
3600                                 flush_write_bio(epd);
3601                                 flush = 1;
3602                         }
3603                         lock_page(p);
3604                 }
3605         }
3606 
3607         return ret;
3608 }
3609 
3610 static void end_extent_buffer_writeback(struct extent_buffer *eb)
3611 {
3612         clear_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags);
3613         smp_mb__after_atomic();
3614         wake_up_bit(&eb->bflags, EXTENT_BUFFER_WRITEBACK);
3615 }
3616 
3617 static void set_btree_ioerr(struct page *page)
3618 {
3619         struct extent_buffer *eb = (struct extent_buffer *)page->private;
3620 
3621         SetPageError(page);
3622         if (test_and_set_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags))
3623                 return;
3624 
3625         /*
3626          * If writeback for a btree extent that doesn't belong to a log tree
3627          * failed, increment the counter transaction->eb_write_errors.
3628          * We do this because while the transaction is running and before it's
3629          * committing (when we call filemap_fdata[write|wait]_range against
3630          * the btree inode), we might have
3631          * btree_inode->i_mapping->a_ops->writepages() called by the VM - if it
3632          * returns an error or an error happens during writeback, when we're
3633          * committing the transaction we wouldn't know about it, since the pages
3634          * can be no longer dirty nor marked anymore for writeback (if a
3635          * subsequent modification to the extent buffer didn't happen before the
3636          * transaction commit), which makes filemap_fdata[write|wait]_range not
3637          * able to find the pages tagged with SetPageError at transaction
3638          * commit time. So if this happens we must abort the transaction,
3639          * otherwise we commit a super block with btree roots that point to
3640          * btree nodes/leafs whose content on disk is invalid - either garbage
3641          * or the content of some node/leaf from a past generation that got
3642          * cowed or deleted and is no longer valid.
3643          *
3644          * Note: setting AS_EIO/AS_ENOSPC in the btree inode's i_mapping would
3645          * not be enough - we need to distinguish between log tree extents vs
3646          * non-log tree extents, and the next filemap_fdatawait_range() call
3647          * will catch and clear such errors in the mapping - and that call might
3648          * be from a log sync and not from a transaction commit. Also, checking
3649          * for the eb flag EXTENT_BUFFER_WRITE_ERR at transaction commit time is
3650          * not done and would not be reliable - the eb might have been released
3651          * from memory and reading it back again means that flag would not be
3652          * set (since it's a runtime flag, not persisted on disk).
3653          *
3654          * Using the flags below in the btree inode also makes us achieve the
3655          * goal of AS_EIO/AS_ENOSPC when writepages() returns success, started
3656          * writeback for all dirty pages and before filemap_fdatawait_range()
3657          * is called, the writeback for all dirty pages had already finished
3658          * with errors - because we were not using AS_EIO/AS_ENOSPC,
3659          * filemap_fdatawait_range() would return success, as it could not know
3660          * that writeback errors happened (the pages were no longer tagged for
3661          * writeback).
3662          */
3663         switch (eb->log_index) {
3664         case -1:
3665                 set_bit(BTRFS_FS_BTREE_ERR, &eb->fs_info->flags);
3666                 break;
3667         case 0:
3668                 set_bit(BTRFS_FS_LOG1_ERR, &eb->fs_info->flags);
3669                 break;
3670         case 1:
3671                 set_bit(BTRFS_FS_LOG2_ERR, &eb->fs_info->flags);
3672                 break;
3673         default:
3674                 BUG(); /* unexpected, logic error */
3675         }
3676 }
3677 
3678 static void end_bio_extent_buffer_writepage(struct bio *bio)
3679 {
3680         struct bio_vec *bvec;
3681         struct extent_buffer *eb;
3682         int i, done;
3683 
3684         ASSERT(!bio_flagged(bio, BIO_CLONED));
3685         bio_for_each_segment_all(bvec, bio, i) {
3686                 struct page *page = bvec->bv_page;
3687 
3688                 eb = (struct extent_buffer *)page->private;
3689                 BUG_ON(!eb);
3690                 done = atomic_dec_and_test(&eb->io_pages);
3691 
3692                 if (bio->bi_status ||
3693                     test_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags)) {
3694                         ClearPageUptodate(page);
3695                         set_btree_ioerr(page);
3696                 }
3697 
3698                 end_page_writeback(page);
3699 
3700                 if (!done)
3701                         continue;
3702 
3703                 end_extent_buffer_writeback(eb);
3704         }
3705 
3706         bio_put(bio);
3707 }
3708 
3709 static noinline_for_stack int write_one_eb(struct extent_buffer *eb,
3710                         struct btrfs_fs_info *fs_info,
3711                         struct writeback_control *wbc,
3712                         struct extent_page_data *epd)
3713 {
3714         struct block_device *bdev = fs_info->fs_devices->latest_bdev;
3715         struct extent_io_tree *tree = &BTRFS_I(fs_info->btree_inode)->io_tree;
3716         u64 offset = eb->start;
3717         u32 nritems;
3718         unsigned long i, num_pages;
3719         unsigned long start, end;
3720         unsigned int write_flags = wbc_to_write_flags(wbc) | REQ_META;
3721         int ret = 0;
3722 
3723         clear_bit(EXTENT_BUFFER_WRITE_ERR, &eb->bflags);
3724         num_pages = num_extent_pages(eb->start, eb->len);
3725         atomic_set(&eb->io_pages, num_pages);
3726 
3727         /* set btree blocks beyond nritems with 0 to avoid stale content. */
3728         nritems = btrfs_header_nritems(eb);
3729         if (btrfs_header_level(eb) > 0) {
3730                 end = btrfs_node_key_ptr_offset(nritems);
3731 
3732                 memzero_extent_buffer(eb, end, eb->len - end);
3733         } else {
3734                 /*
3735                  * leaf:
3736                  * header 0 1 2 .. N ... data_N .. data_2 data_1 data_0
3737                  */
3738                 start = btrfs_item_nr_offset(nritems);
3739                 end = BTRFS_LEAF_DATA_OFFSET + leaf_data_end(fs_info, eb);
3740                 memzero_extent_buffer(eb, start, end - start);
3741         }
3742 
3743         for (i = 0; i < num_pages; i++) {
3744                 struct page *p = eb->pages[i];
3745 
3746                 clear_page_dirty_for_io(p);
3747                 set_page_writeback(p);
3748                 ret = submit_extent_page(REQ_OP_WRITE | write_flags, tree, wbc,
3749                                          p, offset, PAGE_SIZE, 0, bdev,
3750                                          &epd->bio,
3751                                          end_bio_extent_buffer_writepage,
3752                                          0, 0, 0, false);
3753                 if (ret) {
3754                         set_btree_ioerr(p);
3755                         if (PageWriteback(p))
3756                                 end_page_writeback(p);
3757                         if (atomic_sub_and_test(num_pages - i, &eb->io_pages))
3758                                 end_extent_buffer_writeback(eb);
3759                         ret = -EIO;
3760                         break;
3761                 }
3762                 offset += PAGE_SIZE;
3763                 update_nr_written(wbc, 1);
3764                 unlock_page(p);
3765         }
3766 
3767         if (unlikely(ret)) {
3768                 for (; i < num_pages; i++) {
3769                         struct page *p = eb->pages[i];
3770                         clear_page_dirty_for_io(p);
3771                         unlock_page(p);
3772                 }
3773         }
3774 
3775         return ret;
3776 }
3777 
3778 int btree_write_cache_pages(struct address_space *mapping,
3779                                    struct writeback_control *wbc)
3780 {
3781         struct extent_io_tree *tree = &BTRFS_I(mapping->host)->io_tree;
3782         struct btrfs_fs_info *fs_info = BTRFS_I(mapping->host)->root->fs_info;
3783         struct extent_buffer *eb, *prev_eb = NULL;
3784         struct extent_page_data epd = {
3785                 .bio = NULL,
3786                 .tree = tree,
3787                 .extent_locked = 0,
3788                 .sync_io = wbc->sync_mode == WB_SYNC_ALL,
3789         };
3790         int ret = 0;
3791         int done = 0;
3792         int nr_to_write_done = 0;
3793         struct pagevec pvec;
3794         int nr_pages;
3795         pgoff_t index;
3796         pgoff_t end;            /* Inclusive */
3797         int scanned = 0;
3798         int tag;
3799 
3800         pagevec_init(&pvec);
3801         if (wbc->range_cyclic) {
3802                 index = mapping->writeback_index; /* Start from prev offset */
3803                 end = -1;
3804         } else {
3805                 index = wbc->range_start >> PAGE_SHIFT;
3806                 end = wbc->range_end >> PAGE_SHIFT;
3807                 scanned = 1;
3808         }
3809         if (wbc->sync_mode == WB_SYNC_ALL)
3810                 tag = PAGECACHE_TAG_TOWRITE;
3811         else
3812                 tag = PAGECACHE_TAG_DIRTY;
3813 retry:
3814         if (wbc->sync_mode == WB_SYNC_ALL)
3815                 tag_pages_for_writeback(mapping, index, end);
3816         while (!done && !nr_to_write_done && (index <= end) &&
3817                (nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index, end,
3818                         tag))) {
3819                 unsigned i;
3820 
3821                 scanned = 1;
3822                 for (i = 0; i < nr_pages; i++) {
3823                         struct page *page = pvec.pages[i];
3824 
3825                         if (!PagePrivate(page))
3826                                 continue;
3827 
3828                         spin_lock(&mapping->private_lock);
3829                         if (!PagePrivate(page)) {
3830                                 spin_unlock(&mapping->private_lock);
3831                                 continue;
3832                         }
3833 
3834                         eb = (struct extent_buffer *)page->private;
3835 
3836                         /*
3837                          * Shouldn't happen and normally this would be a BUG_ON
3838                          * but no sense in crashing the users box for something
3839                          * we can survive anyway.
3840                          */
3841                         if (WARN_ON(!eb)) {
3842                                 spin_unlock(&mapping->private_lock);
3843                                 continue;
3844                         }
3845 
3846                         if (eb == prev_eb) {
3847                                 spin_unlock(&mapping->private_lock);
3848                                 continue;
3849                         }
3850 
3851                         ret = atomic_inc_not_zero(&eb->refs);
3852                         spin_unlock(&mapping->private_lock);
3853                         if (!ret)
3854                                 continue;
3855 
3856                         prev_eb = eb;
3857                         ret = lock_extent_buffer_for_io(eb, fs_info, &epd);
3858                         if (!ret) {
3859                                 free_extent_buffer(eb);
3860                                 continue;
3861                         }
3862 
3863                         ret = write_one_eb(eb, fs_info, wbc, &epd);
3864                         if (ret) {
3865                                 done = 1;
3866                                 free_extent_buffer(eb);
3867                                 break;
3868                         }
3869                         free_extent_buffer(eb);
3870 
3871                         /*
3872                          * the filesystem may choose to bump up nr_to_write.
3873                          * We have to make sure to honor the new nr_to_write
3874                          * at any time
3875                          */
3876                         nr_to_write_done = wbc->nr_to_write <= 0;
3877                 }
3878                 pagevec_release(&pvec);
3879                 cond_resched();
3880         }
3881         if (!scanned && !done) {
3882                 /*
3883                  * We hit the last page and there is more work to be done: wrap
3884                  * back to the start of the file
3885                  */
3886                 scanned = 1;
3887                 index = 0;
3888                 goto retry;
3889         }
3890         flush_write_bio(&epd);
3891         return ret;
3892 }
3893 
3894 /**
3895  * write_cache_pages - walk the list of dirty pages of the given address space and write all of them.
3896  * @mapping: address space structure to write
3897  * @wbc: subtract the number of written pages from *@wbc->nr_to_write
3898  * @data: data passed to __extent_writepage function
3899  *
3900  * If a page is already under I/O, write_cache_pages() skips it, even
3901  * if it's dirty.  This is desirable behaviour for memory-cleaning writeback,
3902  * but it is INCORRECT for data-integrity system calls such as fsync().  fsync()
3903  * and msync() need to guarantee that all the data which was dirty at the time
3904  * the call was made get new I/O started against them.  If wbc->sync_mode is
3905  * WB_SYNC_ALL then we were called for data integrity and we must wait for
3906  * existing IO to complete.
3907  */
3908 static int extent_write_cache_pages(struct address_space *mapping,
3909                              struct writeback_control *wbc,
3910                              struct extent_page_data *epd)
3911 {
3912         struct inode *inode = mapping->host;
3913         int ret = 0;
3914         int done = 0;
3915         int nr_to_write_done = 0;
3916         struct pagevec pvec;
3917         int nr_pages;
3918         pgoff_t index;
3919         pgoff_t end;            /* Inclusive */
3920         pgoff_t done_index;
3921         int range_whole = 0;
3922         int scanned = 0;
3923         int tag;
3924 
3925         /*
3926          * We have to hold onto the inode so that ordered extents can do their
3927          * work when the IO finishes.  The alternative to this is failing to add
3928          * an ordered extent if the igrab() fails there and that is a huge pain
3929          * to deal with, so instead just hold onto the inode throughout the
3930          * writepages operation.  If it fails here we are freeing up the inode
3931          * anyway and we'd rather not waste our time writing out stuff that is
3932          * going to be truncated anyway.
3933          */
3934         if (!igrab(inode))
3935                 return 0;
3936 
3937         pagevec_init(&pvec);
3938         if (wbc->range_cyclic) {
3939                 index = mapping->writeback_index; /* Start from prev offset */
3940                 end = -1;
3941         } else {
3942                 index = wbc->range_start >> PAGE_SHIFT;
3943                 end = wbc->range_end >> PAGE_SHIFT;
3944                 if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
3945                         range_whole = 1;
3946                 scanned = 1;
3947         }
3948         if (wbc->sync_mode == WB_SYNC_ALL)
3949                 tag = PAGECACHE_TAG_TOWRITE;
3950         else
3951                 tag = PAGECACHE_TAG_DIRTY;
3952 retry:
3953         if (wbc->sync_mode == WB_SYNC_ALL)
3954                 tag_pages_for_writeback(mapping, index, end);
3955         done_index = index;
3956         while (!done && !nr_to_write_done && (index <= end) &&
3957                         (nr_pages = pagevec_lookup_range_tag(&pvec, mapping,
3958                                                 &index, end, tag))) {
3959                 unsigned i;
3960 
3961                 scanned = 1;
3962                 for (i = 0; i < nr_pages; i++) {
3963                         struct page *page = pvec.pages[i];
3964 
3965                         done_index = page->index;
3966                         /*
3967                          * At this point we hold neither the i_pages lock nor
3968                          * the page lock: the page may be truncated or
3969                          * invalidated (changing page->mapping to NULL),
3970                          * or even swizzled back from swapper_space to
3971                          * tmpfs file mapping
3972                          */
3973                         if (!trylock_page(page)) {
3974                                 flush_write_bio(epd);
3975                                 lock_page(page);
3976                         }
3977 
3978                         if (unlikely(page->mapping != mapping)) {
3979                                 unlock_page(page);
3980                                 continue;
3981                         }
3982 
3983                         if (wbc->sync_mode != WB_SYNC_NONE) {
3984                                 if (PageWriteback(page))
3985                                         flush_write_bio(epd);
3986                                 wait_on_page_writeback(page);
3987                         }
3988 
3989                         if (PageWriteback(page) ||
3990                             !clear_page_dirty_for_io(page)) {
3991                                 unlock_page(page);
3992                                 continue;
3993                         }
3994 
3995                         ret = __extent_writepage(page, wbc, epd);
3996 
3997                         if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE)) {
3998                                 unlock_page(page);
3999                                 ret = 0;
4000                         }
4001                         if (ret < 0) {
4002                                 /*
4003                                  * done_index is set past this page,
4004                                  * so media errors will not choke
4005                                  * background writeout for the entire
4006                                  * file. This has consequences for
4007                                  * range_cyclic semantics (ie. it may
4008                                  * not be suitable for data integrity
4009                                  * writeout).
4010                                  */
4011                                 done_index = page->index + 1;
4012                                 done = 1;
4013                                 break;
4014                         }
4015 
4016                         /*
4017                          * the filesystem may choose to bump up nr_to_write.
4018                          * We have to make sure to honor the new nr_to_write
4019                          * at any time
4020                          */
4021                         nr_to_write_done = wbc->nr_to_write <= 0;
4022                 }
4023                 pagevec_release(&pvec);
4024                 cond_resched();
4025         }
4026         if (!scanned && !done) {
4027                 /*
4028                  * We hit the last page and there is more work to be done: wrap
4029                  * back to the start of the file
4030                  */
4031                 scanned = 1;
4032                 index = 0;
4033                 goto retry;
4034         }
4035 
4036         if (wbc->range_cyclic || (wbc->nr_to_write > 0 && range_whole))
4037                 mapping->writeback_index = done_index;
4038 
4039         btrfs_add_delayed_iput(inode);
4040         return ret;
4041 }
4042 
4043 static void flush_write_bio(struct extent_page_data *epd)
4044 {
4045         if (epd->bio) {
4046                 int ret;
4047 
4048                 ret = submit_one_bio(epd->bio, 0, 0);
4049                 BUG_ON(ret < 0); /* -ENOMEM */
4050                 epd->bio = NULL;
4051         }
4052 }
4053 
4054 int extent_write_full_page(struct page *page, struct writeback_control *wbc)
4055 {
4056         int ret;
4057         struct extent_page_data epd = {
4058                 .bio = NULL,
4059                 .tree = &BTRFS_I(page->mapping->host)->io_tree,
4060                 .extent_locked = 0,
4061                 .sync_io = wbc->sync_mode == WB_SYNC_ALL,
4062         };
4063 
4064         ret = __extent_writepage(page, wbc, &epd);
4065 
4066         flush_write_bio(&epd);
4067         return ret;
4068 }
4069 
4070 int extent_write_locked_range(struct inode *inode, u64 start, u64 end,
4071                               int mode)
4072 {
4073         int ret = 0;
4074         struct address_space *mapping = inode->i_mapping;
4075         struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;
4076         struct page *page;
4077         unsigned long nr_pages = (end - start + PAGE_SIZE) >>
4078                 PAGE_SHIFT;
4079 
4080         struct extent_page_data epd = {
4081                 .bio = NULL,
4082                 .tree = tree,
4083                 .extent_locked = 1,
4084                 .sync_io = mode == WB_SYNC_ALL,
4085         };
4086         struct writeback_control wbc_writepages = {
4087                 .sync_mode      = mode,
4088                 .nr_to_write    = nr_pages * 2,
4089                 .range_start    = start,
4090                 .range_end      = end + 1,
4091         };
4092 
4093         while (start <= end) {
4094                 page = find_get_page(mapping, start >> PAGE_SHIFT);
4095                 if (clear_page_dirty_for_io(page))
4096                         ret = __extent_writepage(page, &wbc_writepages, &epd);
4097                 else {
4098                         if (tree->ops && tree->ops->writepage_end_io_hook)
4099                                 tree->ops->writepage_end_io_hook(page, start,
4100                                                  start + PAGE_SIZE - 1,
4101                                                  NULL, 1);
4102                         unlock_page(page);
4103                 }
4104                 put_page(page);
4105                 start += PAGE_SIZE;
4106         }
4107 
4108         flush_write_bio(&epd);
4109         return ret;
4110 }
4111 
4112 int extent_writepages(struct extent_io_tree *tree,
4113                       struct address_space *mapping,
4114                       struct writeback_control *wbc)
4115 {
4116         int ret = 0;
4117         struct extent_page_data epd = {
4118                 .bio = NULL,
4119                 .tree = tree,
4120                 .extent_locked = 0,
4121                 .sync_io = wbc->sync_mode == WB_SYNC_ALL,
4122         };
4123 
4124         ret = extent_write_cache_pages(mapping, wbc, &epd);
4125         flush_write_bio(&epd);
4126         return ret;
4127 }
4128 
4129 int extent_readpages(struct extent_io_tree *tree,
4130                      struct address_space *mapping,
4131                      struct list_head *pages, unsigned nr_pages)
4132 {
4133         struct bio *bio = NULL;
4134         unsigned page_idx;
4135         unsigned long bio_flags = 0;
4136         struct page *pagepool[16];
4137         struct page *page;
4138         struct extent_map *em_cached = NULL;
4139         int nr = 0;
4140         u64 prev_em_start = (u64)-1;
4141 
4142         for (page_idx = 0; page_idx < nr_pages; page_idx++) {
4143                 page = list_entry(pages->prev, struct page, lru);
4144 
4145                 prefetchw(&page->flags);
4146                 list_del(&page->lru);
4147                 if (add_to_page_cache_lru(page, mapping,
4148                                         page->index,
4149                                         readahead_gfp_mask(mapping))) {
4150                         put_page(page);
4151                         continue;
4152                 }
4153 
4154                 pagepool[nr++] = page;
4155                 if (nr < ARRAY_SIZE(pagepool))
4156                         continue;
4157                 __extent_readpages(tree, pagepool, nr, &em_cached, &bio,
4158                                 &bio_flags, &prev_em_start);
4159                 nr = 0;
4160         }
4161         if (nr)
4162                 __extent_readpages(tree, pagepool, nr, &em_cached, &bio,
4163                                 &bio_flags, &prev_em_start);
4164 
4165         if (em_cached)
4166                 free_extent_map(em_cached);
4167 
4168         BUG_ON(!list_empty(pages));
4169         if (bio)
4170                 return submit_one_bio(bio, 0, bio_flags);
4171         return 0;
4172 }
4173 
4174 /*
4175  * basic invalidatepage code, this waits on any locked or writeback
4176  * ranges corresponding to the page, and then deletes any extent state
4177  * records from the tree
4178  */
4179 int extent_invalidatepage(struct extent_io_tree *tree,
4180                           struct page *page, unsigned long offset)
4181 {
4182         struct extent_state *cached_state = NULL;
4183         u64 start = page_offset(page);
4184         u64 end = start + PAGE_SIZE - 1;
4185         size_t blocksize = page->mapping->host->i_sb->s_blocksize;
4186 
4187         start += ALIGN(offset, blocksize);
4188         if (start > end)
4189                 return 0;
4190 
4191         lock_extent_bits(tree, start, end, &cached_state);
4192         wait_on_page_writeback(page);
4193         clear_extent_bit(tree, start, end,
4194                          EXTENT_LOCKED | EXTENT_DIRTY | EXTENT_DELALLOC |
4195                          EXTENT_DO_ACCOUNTING,
4196                          1, 1, &cached_state);
4197         return 0;
4198 }
4199 
4200 /*
4201  * a helper for releasepage, this tests for areas of the page that
4202  * are locked or under IO and drops the related state bits if it is safe
4203  * to drop the page.
4204  */
4205 static int try_release_extent_state(struct extent_map_tree *map,
4206                                     struct extent_io_tree *tree,
4207                                     struct page *page, gfp_t mask)
4208 {
4209         u64 start = page_offset(page);
4210         u64 end = start + PAGE_SIZE - 1;
4211         int ret = 1;
4212 
4213         if (test_range_bit(tree, start, end,
4214                            EXTENT_IOBITS, 0, NULL))
4215                 ret = 0;
4216         else {
4217                 /*
4218                  * at this point we can safely clear everything except the
4219                  * locked bit and the nodatasum bit
4220                  */
4221                 ret = __clear_extent_bit(tree, start, end,
4222                                  ~(EXTENT_LOCKED | EXTENT_NODATASUM),
4223                                  0, 0, NULL, mask, NULL);
4224 
4225                 /* if clear_extent_bit failed for enomem reasons,
4226                  * we can't allow the release to continue.
4227                  */
4228                 if (ret < 0)
4229                         ret = 0;
4230                 else
4231                         ret = 1;
4232         }
4233         return ret;
4234 }
4235 
4236 /*
4237  * a helper for releasepage.  As long as there are no locked extents
4238  * in the range corresponding to the page, both state records and extent
4239  * map records are removed
4240  */
4241 int try_release_extent_mapping(struct extent_map_tree *map,
4242                                struct extent_io_tree *tree, struct page *page,
4243                                gfp_t mask)
4244 {
4245         struct extent_map *em;
4246         u64 start = page_offset(page);
4247         u64 end = start + PAGE_SIZE - 1;
4248         struct btrfs_inode *btrfs_inode = BTRFS_I(page->mapping->host);
4249 
4250         if (gfpflags_allow_blocking(mask) &&
4251             page->mapping->host->i_size > SZ_16M) {
4252                 u64 len;
4253                 while (start <= end) {
4254                         len = end - start + 1;
4255                         write_lock(&map->lock);
4256                         em = lookup_extent_mapping(map, start, len);
4257                         if (!em) {
4258                                 write_unlock(&map->lock);
4259                                 break;
4260                         }
4261                         if (test_bit(EXTENT_FLAG_PINNED, &em->flags) ||
4262                             em->start != start) {
4263                                 write_unlock(&map->lock);
4264                                 free_extent_map(em);
4265                                 break;
4266                         }
4267                         if (!test_range_bit(tree, em->start,
4268                                             extent_map_end(em) - 1,
4269                                             EXTENT_LOCKED | EXTENT_WRITEBACK,
4270                                             0, NULL)) {
4271                                 set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
4272                                         &btrfs_inode->runtime_flags);
4273                                 remove_extent_mapping(map, em);
4274                                 /* once for the rb tree */
4275                                 free_extent_map(em);
4276                         }
4277                         start = extent_map_end(em);
4278                         write_unlock(&map->lock);
4279 
4280                         /* once for us */
4281                         free_extent_map(em);
4282                 }
4283         }
4284         return try_release_extent_state(map, tree, page, mask);
4285 }
4286 
4287 /*
4288  * helper function for fiemap, which doesn't want to see any holes.
4289  * This maps until we find something past 'last'
4290  */
4291 static struct extent_map *get_extent_skip_holes(struct inode *inode,
4292                                                 u64 offset, u64 last)
4293 {
4294         u64 sectorsize = btrfs_inode_sectorsize(inode);
4295         struct extent_map *em;
4296         u64 len;
4297 
4298         if (offset >= last)
4299                 return NULL;
4300 
4301         while (1) {
4302                 len = last - offset;
4303                 if (len == 0)
4304                         break;
4305                 len = ALIGN(len, sectorsize);
4306                 em = btrfs_get_extent_fiemap(BTRFS_I(inode), NULL, 0, offset,
4307                                 len, 0);
4308                 if (IS_ERR_OR_NULL(em))
4309                         return em;
4310 
4311                 /* if this isn't a hole return it */
4312                 if (em->block_start != EXTENT_MAP_HOLE)
4313                         return em;
4314 
4315                 /* this is a hole, advance to the next extent */
4316                 offset = extent_map_end(em);
4317                 free_extent_map(em);
4318                 if (offset >= last)
4319                         break;
4320         }
4321         return NULL;
4322 }
4323 
4324 /*
4325  * To cache previous fiemap extent
4326  *
4327  * Will be used for merging fiemap extent
4328  */
4329 struct fiemap_cache {
4330         u64 offset;
4331         u64 phys;
4332         u64 len;
4333         u32 flags;
4334         bool cached;
4335 };
4336 
4337 /*
4338  * Helper to submit fiemap extent.
4339  *
4340  * Will try to merge current fiemap extent specified by @offset, @phys,
4341  * @len and @flags with cached one.
4342  * And only when we fails to merge, cached one will be submitted as
4343  * fiemap extent.
4344  *
4345  * Return value is the same as fiemap_fill_next_extent().
4346  */
4347 static int emit_fiemap_extent(struct fiemap_extent_info *fieinfo,
4348                                 struct fiemap_cache *cache,
4349                                 u64 offset, u64 phys, u64 len, u32 flags)
4350 {
4351         int ret = 0;
4352 
4353         if (!cache->cached)
4354                 goto assign;
4355 
4356         /*
4357          * Sanity check, extent_fiemap() should have ensured that new
4358          * fiemap extent won't overlap with cahced one.
4359          * Not recoverable.
4360          *
4361          * NOTE: Physical address can overlap, due to compression
4362          */
4363         if (cache->offset + cache->len > offset) {
4364                 WARN_ON(1);
4365                 return -EINVAL;
4366         }
4367 
4368         /*
4369          * Only merges fiemap extents if
4370          * 1) Their logical addresses are continuous
4371          *
4372          * 2) Their physical addresses are continuous
4373          *    So truly compressed (physical size smaller than logical size)
4374          *    extents won't get merged with each other
4375          *
4376          * 3) Share same flags except FIEMAP_EXTENT_LAST
4377          *    So regular extent won't get merged with prealloc extent
4378          */
4379         if (cache->offset + cache->len  == offset &&
4380             cache->phys + cache->len == phys  &&
4381             (cache->flags & ~FIEMAP_EXTENT_LAST) ==
4382                         (flags & ~FIEMAP_EXTENT_LAST)) {
4383                 cache->len += len;
4384                 cache->flags |= flags;
4385                 goto try_submit_last;
4386         }
4387 
4388         /* Not mergeable, need to submit cached one */
4389         ret = fiemap_fill_next_extent(fieinfo, cache->offset, cache->phys,
4390                                       cache->len, cache->flags);
4391         cache->cached = false;
4392         if (ret)
4393                 return ret;
4394 assign:
4395         cache->cached = true;
4396         cache->offset = offset;
4397         cache->phys = phys;
4398         cache->len = len;
4399         cache->flags = flags;
4400 try_submit_last:
4401         if (cache->flags & FIEMAP_EXTENT_LAST) {
4402                 ret = fiemap_fill_next_extent(fieinfo, cache->offset,
4403                                 cache->phys, cache->len, cache->flags);
4404                 cache->cached = false;
4405         }
4406         return ret;
4407 }
4408 
4409 /*
4410  * Emit last fiemap cache
4411  *
4412  * The last fiemap cache may still be cached in the following case:
4413  * 0                  4k                    8k
4414  * |<- Fiemap range ->|
4415  * |<------------  First extent ----------->|
4416  *
4417  * In this case, the first extent range will be cached but not emitted.
4418  * So we must emit it before ending extent_fiemap().
4419  */
4420 static int emit_last_fiemap_cache(struct btrfs_fs_info *fs_info,
4421                                   struct fiemap_extent_info *fieinfo,
4422                                   struct fiemap_cache *cache)
4423 {
4424         int ret;
4425 
4426         if (!cache->cached)
4427                 return 0;
4428 
4429         ret = fiemap_fill_next_extent(fieinfo, cache->offset, cache->phys,
4430                                       cache->len, cache->flags);
4431         cache->cached = false;
4432         if (ret > 0)
4433                 ret = 0;
4434         return ret;
4435 }
4436 
4437 int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
4438                 __u64 start, __u64 len)
4439 {
4440         int ret = 0;
4441         u64 off = start;
4442         u64 max = start + len;
4443         u32 flags = 0;
4444         u32 found_type;
4445         u64 last;
4446         u64 last_for_get_extent = 0;
4447         u64 disko = 0;
4448         u64 isize = i_size_read(inode);
4449         struct btrfs_key found_key;
4450         struct extent_map *em = NULL;
4451         struct extent_state *cached_state = NULL;
4452         struct btrfs_path *path;
4453         struct btrfs_root *root = BTRFS_I(inode)->root;
4454         struct fiemap_cache cache = { 0 };
4455         int end = 0;
4456         u64 em_start = 0;
4457         u64 em_len = 0;
4458         u64 em_end = 0;
4459 
4460         if (len == 0)
4461                 return -EINVAL;
4462 
4463         path = btrfs_alloc_path();
4464         if (!path)
4465                 return -ENOMEM;
4466         path->leave_spinning = 1;
4467 
4468         start = round_down(start, btrfs_inode_sectorsize(inode));
4469         len = round_up(max, btrfs_inode_sectorsize(inode)) - start;
4470 
4471         /*
4472          * lookup the last file extent.  We're not using i_size here
4473          * because there might be preallocation past i_size
4474          */
4475         ret = btrfs_lookup_file_extent(NULL, root, path,
4476                         btrfs_ino(BTRFS_I(inode)), -1, 0);
4477         if (ret < 0) {
4478                 btrfs_free_path(path);
4479                 return ret;
4480         } else {
4481                 WARN_ON(!ret);
4482                 if (ret == 1)
4483                         ret = 0;
4484         }
4485 
4486         path->slots[0]--;
4487         btrfs_item_key_to_cpu(path->nodes[0], &found_key, path->slots[0]);
4488         found_type = found_key.type;
4489 
4490         /* No extents, but there might be delalloc bits */
4491         if (found_key.objectid != btrfs_ino(BTRFS_I(inode)) ||
4492             found_type != BTRFS_EXTENT_DATA_KEY) {
4493                 /* have to trust i_size as the end */
4494                 last = (u64)-1;
4495                 last_for_get_extent = isize;
4496         } else {
4497                 /*
4498                  * remember the start of the last extent.  There are a
4499                  * bunch of different factors that go into the length of the
4500                  * extent, so its much less complex to remember where it started
4501                  */
4502                 last = found_key.offset;
4503                 last_for_get_extent = last + 1;
4504         }
4505         btrfs_release_path(path);
4506 
4507         /*
4508          * we might have some extents allocated but more delalloc past those
4509          * extents.  so, we trust isize unless the start of the last extent is
4510          * beyond isize
4511          */
4512         if (last < isize) {
4513                 last = (u64)-1;
4514                 last_for_get_extent = isize;
4515         }
4516 
4517         lock_extent_bits(&BTRFS_I(inode)->io_tree, start, start + len - 1,
4518                          &cached_state);
4519 
4520         em = get_extent_skip_holes(inode, start, last_for_get_extent);
4521         if (!em)
4522                 goto out;
4523         if (IS_ERR(em)) {
4524                 ret = PTR_ERR(em);
4525                 goto out;
4526         }
4527 
4528         while (!end) {
4529                 u64 offset_in_extent = 0;
4530 
4531                 /* break if the extent we found is outside the range */
4532                 if (em->start >= max || extent_map_end(em) < off)
4533                         break;
4534 
4535                 /*
4536                  * get_extent may return an extent that starts before our
4537                  * requested range.  We have to make sure the ranges
4538                  * we return to fiemap always move forward and don't
4539                  * overlap, so adjust the offsets here
4540                  */
4541                 em_start = max(em->start, off);
4542 
4543                 /*
4544                  * record the offset from the start of the extent
4545                  * for adjusting the disk offset below.  Only do this if the
4546                  * extent isn't compressed since our in ram offset may be past
4547                  * what we have actually allocated on disk.
4548                  */
4549                 if (!test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
4550                         offset_in_extent = em_start - em->start;
4551                 em_end = extent_map_end(em);
4552                 em_len = em_end - em_start;
4553                 disko = 0;
4554                 flags = 0;
4555 
4556                 /*
4557                  * bump off for our next call to get_extent
4558                  */
4559                 off = extent_map_end(em);
4560                 if (off >= max)
4561                         end = 1;
4562 
4563                 if (em->block_start == EXTENT_MAP_LAST_BYTE) {
4564                         end = 1;
4565                         flags |= FIEMAP_EXTENT_LAST;
4566                 } else if (em->block_start == EXTENT_MAP_INLINE) {
4567                         flags |= (FIEMAP_EXTENT_DATA_INLINE |
4568                                   FIEMAP_EXTENT_NOT_ALIGNED);
4569                 } else if (em->block_start == EXTENT_MAP_DELALLOC) {
4570                         flags |= (FIEMAP_EXTENT_DELALLOC |
4571                                   FIEMAP_EXTENT_UNKNOWN);
4572                 } else if (fieinfo->fi_extents_max) {
4573                         u64 bytenr = em->block_start -
4574                                 (em->start - em->orig_start);
4575 
4576                         disko = em->block_start + offset_in_extent;
4577 
4578                         /*
4579                          * As btrfs supports shared space, this information
4580                          * can be exported to userspace tools via
4581                          * flag FIEMAP_EXTENT_SHARED.  If fi_extents_max == 0
4582                          * then we're just getting a count and we can skip the
4583                          * lookup stuff.
4584                          */
4585                         ret = btrfs_check_shared(root,
4586                                                  btrfs_ino(BTRFS_I(inode)),
4587                                                  bytenr);
4588                         if (ret < 0)
4589                                 goto out_free;
4590                         if (ret)
4591                                 flags |= FIEMAP_EXTENT_SHARED;
4592                         ret = 0;
4593                 }
4594                 if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
4595                         flags |= FIEMAP_EXTENT_ENCODED;
4596                 if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
4597                         flags |= FIEMAP_EXTENT_UNWRITTEN;
4598 
4599                 free_extent_map(em);
4600                 em = NULL;
4601                 if ((em_start >= last) || em_len == (u64)-1 ||
4602                    (last == (u64)-1 && isize <= em_end)) {
4603                         flags |= FIEMAP_EXTENT_LAST;
4604                         end = 1;
4605                 }
4606 
4607                 /* now scan forward to see if this is really the last extent. */
4608                 em = get_extent_skip_holes(inode, off, last_for_get_extent);
4609                 if (IS_ERR(em)) {
4610                         ret = PTR_ERR(em);
4611                         goto out;
4612                 }
4613                 if (!em) {
4614                         flags |= FIEMAP_EXTENT_LAST;
4615                         end = 1;
4616                 }
4617                 ret = emit_fiemap_extent(fieinfo, &cache, em_start, disko,
4618                                            em_len, flags);
4619                 if (ret) {
4620                         if (ret == 1)
4621                                 ret = 0;
4622                         goto out_free;
4623                 }
4624         }
4625 out_free:
4626         if (!ret)
4627                 ret = emit_last_fiemap_cache(root->fs_info, fieinfo, &cache);
4628         free_extent_map(em);
4629 out:
4630         btrfs_free_path(path);
4631         unlock_extent_cached(&BTRFS_I(inode)->io_tree, start, start + len - 1,
4632                              &cached_state);
4633         return ret;
4634 }
4635 
4636 static void __free_extent_buffer(struct extent_buffer *eb)
4637 {
4638         btrfs_leak_debug_del(&eb->leak_list);
4639         kmem_cache_free(extent_buffer_cache, eb);
4640 }
4641 
4642 int extent_buffer_under_io(struct extent_buffer *eb)
4643 {
4644         return (atomic_read(&eb->io_pages) ||
4645                 test_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags) ||
4646                 test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
4647 }
4648 
4649 /*
4650  * Helper for releasing extent buffer page.
4651  */
4652 static void btrfs_release_extent_buffer_page(struct extent_buffer *eb)
4653 {
4654         unsigned long index;
4655         struct page *page;
4656         int mapped = !test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags);
4657 
4658         BUG_ON(extent_buffer_under_io(eb));
4659 
4660         index = num_extent_pages(eb->start, eb->len);
4661         if (index == 0)
4662                 return;
4663 
4664         do {
4665                 index--;
4666                 page = eb->pages[index];
4667                 if (!page)
4668                         continue;
4669                 if (mapped)
4670                         spin_lock(&page->mapping->private_lock);
4671                 /*
4672                  * We do this since we'll remove the pages after we've
4673                  * removed the eb from the radix tree, so we could race
4674                  * and have this page now attached to the new eb.  So
4675                  * only clear page_private if it's still connected to
4676                  * this eb.
4677                  */
4678                 if (PagePrivate(page) &&
4679                     page->private == (unsigned long)eb) {
4680                         BUG_ON(test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
4681                         BUG_ON(PageDirty(page));
4682                         BUG_ON(PageWriteback(page));
4683                         /*
4684                          * We need to make sure we haven't be attached
4685                          * to a new eb.
4686                          */
4687                         ClearPagePrivate(page);
4688                         set_page_private(page, 0);
4689                         /* One for the page private */
4690                         put_page(page);
4691                 }
4692 
4693                 if (mapped)
4694                         spin_unlock(&page->mapping->private_lock);
4695 
4696                 /* One for when we allocated the page */
4697                 put_page(page);
4698         } while (index != 0);
4699 }
4700 
4701 /*
4702  * Helper for releasing the extent buffer.
4703  */
4704 static inline void btrfs_release_extent_buffer(struct extent_buffer *eb)
4705 {
4706         btrfs_release_extent_buffer_page(eb);
4707         __free_extent_buffer(eb);
4708 }
4709 
4710 static struct extent_buffer *
4711 __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
4712                       unsigned long len)
4713 {
4714         struct extent_buffer *eb = NULL;
4715 
4716         eb = kmem_cache_zalloc(extent_buffer_cache, GFP_NOFS|__GFP_NOFAIL);
4717         eb->start = start;
4718         eb->len = len;
4719         eb->fs_info = fs_info;
4720         eb->bflags = 0;
4721         rwlock_init(&eb->lock);
4722         atomic_set(&eb->write_locks, 0);
4723         atomic_set(&eb->read_locks, 0);
4724         atomic_set(&eb->blocking_readers, 0);
4725         atomic_set(&eb->blocking_writers, 0);
4726         atomic_set(&eb->spinning_readers, 0);
4727         atomic_set(&eb->spinning_writers, 0);
4728         eb->lock_nested = 0;
4729         init_waitqueue_head(&eb->write_lock_wq);
4730         init_waitqueue_head(&eb->read_lock_wq);
4731 
4732         btrfs_leak_debug_add(&eb->leak_list, &buffers);
4733 
4734         spin_lock_init(&eb->refs_lock);
4735         atomic_set(&eb->refs, 1);
4736         atomic_set(&eb->io_pages, 0);
4737 
4738         /*
4739          * Sanity checks, currently the maximum is 64k covered by 16x 4k pages
4740          */
4741         BUILD_BUG_ON(BTRFS_MAX_METADATA_BLOCKSIZE
4742                 > MAX_INLINE_EXTENT_BUFFER_SIZE);
4743         BUG_ON(len > MAX_INLINE_EXTENT_BUFFER_SIZE);
4744 
4745         return eb;
4746 }
4747 
4748 struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src)
4749 {
4750         unsigned long i;
4751         struct page *p;
4752         struct extent_buffer *new;
4753         unsigned long num_pages = num_extent_pages(src->start, src->len);
4754 
4755         new = __alloc_extent_buffer(src->fs_info, src->start, src->len);
4756         if (new == NULL)
4757                 return NULL;
4758 
4759         for (i = 0; i < num_pages; i++) {
4760                 p = alloc_page(GFP_NOFS);
4761                 if (!p) {
4762                         btrfs_release_extent_buffer(new);
4763                         return NULL;
4764                 }
4765                 attach_extent_buffer_page(new, p);
4766                 WARN_ON(PageDirty(p));
4767                 SetPageUptodate(p);
4768                 new->pages[i] = p;
4769                 copy_page(page_address(p), page_address(src->pages[i]));
4770         }
4771 
4772         set_bit(EXTENT_BUFFER_UPTODATE, &new->bflags);
4773         set_bit(EXTENT_BUFFER_DUMMY, &new->bflags);
4774 
4775         return new;
4776 }
4777 
4778 struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
4779                                                   u64 start, unsigned long len)
4780 {
4781         struct extent_buffer *eb;
4782         unsigned long num_pages;
4783         unsigned long i;
4784 
4785         num_pages = num_extent_pages(start, len);
4786 
4787         eb = __alloc_extent_buffer(fs_info, start, len);
4788         if (!eb)
4789                 return NULL;
4790 
4791         for (i = 0; i < num_pages; i++) {
4792                 eb->pages[i] = alloc_page(GFP_NOFS);
4793                 if (!eb->pages[i])
4794                         goto err;
4795         }
4796         set_extent_buffer_uptodate(eb);
4797         btrfs_set_header_nritems(eb, 0);
4798         set_bit(EXTENT_BUFFER_DUMMY, &eb->bflags);
4799 
4800         return eb;
4801 err:
4802         for (; i > 0; i--)
4803                 __free_page(eb->pages[i - 1]);
4804         __free_extent_buffer(eb);
4805         return NULL;
4806 }
4807 
4808 struct extent_buffer *alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
4809                                                 u64 start)
4810 {
4811         return __alloc_dummy_extent_buffer(fs_info, start, fs_info->nodesize);
4812 }
4813 
4814 static void check_buffer_tree_ref(struct extent_buffer *eb)
4815 {
4816         int refs;
4817         /* the ref bit is tricky.  We have to make sure it is set
4818          * if we have the buffer dirty.   Otherwise the
4819          * code to free a buffer can end up dropping a dirty
4820          * page
4821          *
4822          * Once the ref bit is set, it won't go away while the
4823          * buffer is dirty or in writeback, and it also won't
4824          * go away while we have the reference count on the
4825          * eb bumped.
4826          *
4827          * We can't just set the ref bit without bumping the
4828          * ref on the eb because free_extent_buffer might
4829          * see the ref bit and try to clear it.  If this happens
4830          * free_extent_buffer might end up dropping our original
4831          * ref by mistake and freeing the page before we are able
4832          * to add one more ref.
4833          *
4834          * So bump the ref count first, then set the bit.  If someone
4835          * beat us to it, drop the ref we added.
4836          */
4837         refs = atomic_read(&eb->refs);
4838         if (refs >= 2 && test_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
4839                 return;
4840 
4841         spin_lock(&eb->refs_lock);
4842         if (!test_and_set_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
4843                 atomic_inc(&eb->refs);
4844         spin_unlock(&eb->refs_lock);
4845 }
4846 
4847 static void mark_extent_buffer_accessed(struct extent_buffer *eb,
4848                 struct page *accessed)
4849 {
4850         unsigned long num_pages, i;
4851 
4852         check_buffer_tree_ref(eb);
4853 
4854         num_pages = num_extent_pages(eb->start, eb->len);
4855         for (i = 0; i < num_pages; i++) {
4856                 struct page *p = eb->pages[i];
4857 
4858                 if (p != accessed)
4859                         mark_page_accessed(p);
4860         }
4861 }
4862 
4863 struct extent_buffer *find_extent_buffer(struct btrfs_fs_info *fs_info,
4864                                          u64 start)
4865 {
4866         struct extent_buffer *eb;
4867 
4868         rcu_read_lock();
4869         eb = radix_tree_lookup(&fs_info->buffer_radix,
4870                                start >> PAGE_SHIFT);
4871         if (eb && atomic_inc_not_zero(&eb->refs)) {
4872                 rcu_read_unlock();
4873                 /*
4874                  * Lock our eb's refs_lock to avoid races with
4875                  * free_extent_buffer. When we get our eb it might be flagged
4876                  * with EXTENT_BUFFER_STALE and another task running
4877                  * free_extent_buffer might have seen that flag set,
4878                  * eb->refs == 2, that the buffer isn't under IO (dirty and
4879                  * writeback flags not set) and it's still in the tree (flag
4880                  * EXTENT_BUFFER_TREE_REF set), therefore being in the process
4881                  * of decrementing the extent buffer's reference count twice.
4882                  * So here we could race and increment the eb's reference count,
4883                  * clear its stale flag, mark it as dirty and drop our reference
4884                  * before the other task finishes executing free_extent_buffer,
4885                  * which would later result in an attempt to free an extent
4886                  * buffer that is dirty.
4887                  */
4888                 if (test_bit(EXTENT_BUFFER_STALE, &eb->bflags)) {
4889                         spin_lock(&eb->refs_lock);
4890                         spin_unlock(&eb->refs_lock);
4891                 }
4892                 mark_extent_buffer_accessed(eb, NULL);
4893                 return eb;
4894         }
4895         rcu_read_unlock();
4896 
4897         return NULL;
4898 }
4899 
4900 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
4901 struct extent_buffer *alloc_test_extent_buffer(struct btrfs_fs_info *fs_info,
4902                                         u64 start)
4903 {
4904         struct extent_buffer *eb, *exists = NULL;
4905         int ret;
4906 
4907         eb = find_extent_buffer(fs_info, start);
4908         if (eb)
4909                 return eb;
4910         eb = alloc_dummy_extent_buffer(fs_info, start);
4911         if (!eb)
4912                 return NULL;
4913         eb->fs_info = fs_info;
4914 again:
4915         ret = radix_tree_preload(GFP_NOFS);
4916         if (ret)
4917                 goto free_eb;
4918         spin_lock(&fs_info->buffer_lock);
4919         ret = radix_tree_insert(&fs_info->buffer_radix,
4920                                 start >> PAGE_SHIFT, eb);
4921         spin_unlock(&fs_info->buffer_lock);
4922         radix_tree_preload_end();
4923         if (ret == -EEXIST) {
4924                 exists = find_extent_buffer(fs_info, start);
4925                 if (exists)
4926                         goto free_eb;
4927                 else
4928                         goto again;
4929         }
4930         check_buffer_tree_ref(eb);
4931         set_bit(EXTENT_BUFFER_IN_TREE, &eb->bflags);
4932 
4933         /*
4934          * We will free dummy extent buffer's if they come into
4935          * free_extent_buffer with a ref count of 2, but if we are using this we
4936          * want the buffers to stay in memory until we're done with them, so
4937          * bump the ref count again.
4938          */
4939         atomic_inc(&eb->refs);
4940         return eb;
4941 free_eb:
4942         btrfs_release_extent_buffer(eb);
4943         return exists;
4944 }
4945 #endif
4946 
4947 struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
4948                                           u64 start)
4949 {
4950         unsigned long len = fs_info->nodesize;
4951         unsigned long num_pages = num_extent_pages(start, len);
4952         unsigned long i;
4953         unsigned long index = start >> PAGE_SHIFT;
4954         struct extent_buffer *eb;
4955         struct extent_buffer *exists = NULL;
4956         struct page *p;
4957         struct address_space *mapping = fs_info->btree_inode->i_mapping;
4958         int uptodate = 1;
4959         int ret;
4960 
4961         if (!IS_ALIGNED(start, fs_info->sectorsize)) {
4962                 btrfs_err(fs_info, "bad tree block start %llu", start);
4963                 return ERR_PTR(-EINVAL);
4964         }
4965 
4966         eb = find_extent_buffer(fs_info, start);
4967         if (eb)
4968                 return eb;
4969 
4970         eb = __alloc_extent_buffer(fs_info, start, len);
4971         if (!eb)
4972                 return ERR_PTR(-ENOMEM);
4973 
4974         for (i = 0; i < num_pages; i++, index++) {
4975                 p = find_or_create_page(mapping, index, GFP_NOFS|__GFP_NOFAIL);
4976                 if (!p) {
4977                         exists = ERR_PTR(-ENOMEM);
4978                         goto free_eb;
4979                 }
4980 
4981                 spin_lock(&mapping->private_lock);
4982                 if (PagePrivate(p)) {
4983                         /*
4984                          * We could have already allocated an eb for this page
4985                          * and attached one so lets see if we can get a ref on
4986                          * the existing eb, and if we can we know it's good and
4987                          * we can just return that one, else we know we can just
4988                          * overwrite page->private.
4989                          */
4990                         exists = (struct extent_buffer *)p->private;
4991                         if (atomic_inc_not_zero(&exists->refs)) {
4992                                 spin_unlock(&mapping->private_lock);
4993                                 unlock_page(p);
4994                                 put_page(p);
4995                                 mark_extent_buffer_accessed(exists, p);
4996                                 goto free_eb;
4997                         }
4998                         exists = NULL;
4999 
5000                         /*
5001                          * Do this so attach doesn't complain and we need to
5002                          * drop the ref the old guy had.
5003                          */
5004                         ClearPagePrivate(p);
5005                         WARN_ON(PageDirty(p));
5006                         put_page(p);
5007                 }
5008                 attach_extent_buffer_page(eb, p);
5009                 spin_unlock(&mapping->private_lock);
5010                 WARN_ON(PageDirty(p));
5011                 eb->pages[i] = p;
5012                 if (!PageUptodate(p))
5013                         uptodate = 0;
5014 
5015                 /*
5016                  * see below about how we avoid a nasty race with release page
5017                  * and why we unlock later
5018                  */
5019         }
5020         if (uptodate)
5021                 set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
5022 again:
5023         ret = radix_tree_preload(GFP_NOFS);
5024         if (ret) {
5025                 exists = ERR_PTR(ret);
5026                 goto free_eb;
5027         }
5028 
5029         spin_lock(&fs_info->buffer_lock);
5030         ret = radix_tree_insert(&fs_info->buffer_radix,
5031                                 start >> PAGE_SHIFT, eb);
5032         spin_unlock(&fs_info->buffer_lock);
5033         radix_tree_preload_end();
5034         if (ret == -EEXIST) {
5035                 exists = find_extent_buffer(fs_info, start);
5036                 if (exists)
5037                         goto free_eb;
5038                 else
5039                         goto again;
5040         }
5041         /* add one reference for the tree */
5042         check_buffer_tree_ref(eb);
5043         set_bit(EXTENT_BUFFER_IN_TREE, &eb->bflags);
5044 
5045         /*
5046          * there is a race where release page may have
5047          * tried to find this extent buffer in the radix
5048          * but failed.  It will tell the VM it is safe to
5049          * reclaim the, and it will clear the page private bit.
5050          * We must make sure to set the page private bit properly
5051          * after the extent buffer is in the radix tree so
5052          * it doesn't get lost
5053          */
5054         SetPageChecked(eb->pages[0]);
5055         for (i = 1; i < num_pages; i++) {
5056                 p = eb->pages[i];
5057                 ClearPageChecked(p);
5058                 unlock_page(p);
5059         }
5060         unlock_page(eb->pages[0]);
5061         return eb;
5062 
5063 free_eb:
5064         WARN_ON(!atomic_dec_and_test(&eb->refs));
5065         for (i = 0; i < num_pages; i++) {
5066                 if (eb->pages[i])
5067                         unlock_page(eb->pages[i]);
5068         }
5069 
5070         btrfs_release_extent_buffer(eb);
5071         return exists;
5072 }
5073 
5074 static inline void btrfs_release_extent_buffer_rcu(struct rcu_head *head)
5075 {
5076         struct extent_buffer *eb =
5077                         container_of(head, struct extent_buffer, rcu_head);
5078 
5079         __free_extent_buffer(eb);
5080 }
5081 
5082 /* Expects to have eb->eb_lock already held */
5083 static int release_extent_buffer(struct extent_buffer *eb)
5084 {
5085         WARN_ON(atomic_read(&eb->refs) == 0);
5086         if (atomic_dec_and_test(&eb->refs)) {
5087                 if (test_and_clear_bit(EXTENT_BUFFER_IN_TREE, &eb->bflags)) {
5088                         struct btrfs_fs_info *fs_info = eb->fs_info;
5089 
5090                         spin_unlock(&eb->refs_lock);
5091 
5092                         spin_lock(&fs_info->buffer_lock);
5093                         radix_tree_delete(&fs_info->buffer_radix,
5094                                           eb->start >> PAGE_SHIFT);
5095                         spin_unlock(&fs_info->buffer_lock);
5096                 } else {
5097                         spin_unlock(&eb->refs_lock);
5098                 }
5099 
5100                 /* Should be safe to release our pages at this point */
5101                 btrfs_release_extent_buffer_page(eb);
5102 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
5103                 if (unlikely(test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags))) {
5104                         __free_extent_buffer(eb);
5105                         return 1;
5106                 }
5107 #endif
5108                 call_rcu(&eb->rcu_head, btrfs_release_extent_buffer_rcu);
5109                 return 1;
5110         }
5111         spin_unlock(&eb->refs_lock);
5112 
5113         return 0;
5114 }
5115 
5116 void free_extent_buffer(struct extent_buffer *eb)
5117 {
5118         int refs;
5119         int old;
5120         if (!eb)
5121                 return;
5122 
5123         while (1) {
5124                 refs = atomic_read(&eb->refs);
5125                 if (refs <= 3)
5126                         break;
5127                 old = atomic_cmpxchg(&eb->refs, refs, refs - 1);
5128                 if (old == refs)
5129                         return;
5130         }
5131 
5132         spin_lock(&eb->refs_lock);
5133         if (atomic_read(&eb->refs) == 2 &&
5134             test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags))
5135                 atomic_dec(&eb->refs);
5136 
5137         if (atomic_read(&eb->refs) == 2 &&
5138             test_bit(EXTENT_BUFFER_STALE, &eb->bflags) &&
5139             !extent_buffer_under_io(eb) &&
5140             test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
5141                 atomic_dec(&eb->refs);
5142 
5143         /*
5144          * I know this is terrible, but it's temporary until we stop tracking
5145          * the uptodate bits and such for the extent buffers.
5146          */
5147         release_extent_buffer(eb);
5148 }
5149 
5150 void free_extent_buffer_stale(struct extent_buffer *eb)
5151 {
5152         if (!eb)
5153                 return;
5154 
5155         spin_lock(&eb->refs_lock);
5156         set_bit(EXTENT_BUFFER_STALE, &eb->bflags);
5157 
5158         if (atomic_read(&eb->refs) == 2 && !extent_buffer_under_io(eb) &&
5159             test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
5160                 atomic_dec(&eb->refs);
5161         release_extent_buffer(eb);
5162 }
5163 
5164 void clear_extent_buffer_dirty(struct extent_buffer *eb)
5165 {
5166         unsigned long i;
5167         unsigned long num_pages;
5168         struct page *page;
5169 
5170         num_pages = num_extent_pages(eb->start, eb->len);
5171 
5172         for (i = 0; i < num_pages; i++) {
5173                 page = eb->pages[i];
5174                 if (!PageDirty(page))
5175                         continue;
5176 
5177                 lock_page(page);
5178                 WARN_ON(!PagePrivate(page));
5179 
5180                 clear_page_dirty_for_io(page);
5181                 xa_lock_irq(&page->mapping->i_pages);
5182                 if (!PageDirty(page)) {
5183                         radix_tree_tag_clear(&page->mapping->i_pages,
5184                                                 page_index(page),
5185                                                 PAGECACHE_TAG_DIRTY);
5186                 }
5187                 xa_unlock_irq(&page->mapping->i_pages);
5188                 ClearPageError(page);
5189                 unlock_page(page);
5190         }
5191         WARN_ON(atomic_read(&eb->refs) == 0);
5192 }
5193 
5194 int set_extent_buffer_dirty(struct extent_buffer *eb)
5195 {
5196         unsigned long i;
5197         unsigned long num_pages;
5198         int was_dirty = 0;
5199 
5200         check_buffer_tree_ref(eb);
5201 
5202         was_dirty = test_and_set_bit(EXTENT_BUFFER_DIRTY, &eb->bflags);
5203 
5204         num_pages = num_extent_pages(eb->start, eb->len);
5205         WARN_ON(atomic_read(&eb->refs) == 0);
5206         WARN_ON(!test_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags));
5207 
5208         for (i = 0; i < num_pages; i++)
5209                 set_page_dirty(eb->pages[i]);
5210         return was_dirty;
5211 }
5212 
5213 void clear_extent_buffer_uptodate(struct extent_buffer *eb)
5214 {
5215         unsigned long i;
5216         struct page *page;
5217         unsigned long num_pages;
5218 
5219         clear_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
5220         num_pages = num_extent_pages(eb->start, eb->len);
5221         for (i = 0; i < num_pages; i++) {
5222                 page = eb->pages[i];
5223                 if (page)
5224                         ClearPageUptodate(page);
5225         }
5226 }
5227 
5228 void set_extent_buffer_uptodate(struct extent_buffer *eb)
5229 {
5230         unsigned long i;
5231         struct page *page;
5232         unsigned long num_pages;
5233 
5234         set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
5235         num_pages = num_extent_pages(eb->start, eb->len);
5236         for (i = 0; i < num_pages; i++) {
5237                 page = eb->pages[i];
5238                 SetPageUptodate(page);
5239         }
5240 }
5241 
5242 int read_extent_buffer_pages(struct extent_io_tree *tree,
5243                              struct extent_buffer *eb, int wait, int mirror_num)
5244 {
5245         unsigned long i;
5246         struct page *page;
5247         int err;
5248         int ret = 0;
5249         int locked_pages = 0;
5250         int all_uptodate = 1;
5251         unsigned long num_pages;
5252         unsigned long num_reads = 0;
5253         struct bio *bio = NULL;
5254         unsigned long bio_flags = 0;
5255 
5256         if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
5257                 return 0;
5258 
5259         num_pages = num_extent_pages(eb->start, eb->len);
5260         for (i = 0; i < num_pages; i++) {
5261                 page = eb->pages[i];
5262                 if (wait == WAIT_NONE) {
5263                         if (!trylock_page(page))
5264                                 goto unlock_exit;
5265                 } else {
5266                         lock_page(page);
5267                 }
5268                 locked_pages++;
5269         }
5270         /*
5271          * We need to firstly lock all pages to make sure that
5272          * the uptodate bit of our pages won't be affected by
5273          * clear_extent_buffer_uptodate().
5274          */
5275         for (i = 0; i < num_pages; i++) {
5276                 page = eb->pages[i];
5277                 if (!PageUptodate(page)) {
5278                         num_reads++;
5279                         all_uptodate = 0;
5280                 }
5281         }
5282 
5283         if (all_uptodate) {
5284                 set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
5285                 goto unlock_exit;
5286         }
5287 
5288         clear_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags);
5289         eb->read_mirror = 0;
5290         atomic_set(&eb->io_pages, num_reads);
5291         for (i = 0; i < num_pages; i++) {
5292                 page = eb->pages[i];
5293 
5294                 if (!PageUptodate(page)) {
5295                         if (ret) {
5296                                 atomic_dec(&eb->io_pages);
5297                                 unlock_page(page);
5298                                 continue;
5299                         }
5300 
5301                         ClearPageError(page);
5302                         err = __extent_read_full_page(tree, page,
5303                                                       btree_get_extent, &bio,
5304                                                       mirror_num, &bio_flags,
5305                                                       REQ_META);
5306                         if (err) {
5307                                 ret = err;
5308                                 /*
5309                                  * We use &bio in above __extent_read_full_page,
5310                                  * so we ensure that if it returns error, the
5311                                  * current page fails to add itself to bio and
5312                                  * it's been unlocked.
5313                                  *
5314                                  * We must dec io_pages by ourselves.
5315                                  */
5316                                 atomic_dec(&eb->io_pages);
5317                         }
5318                 } else {
5319                         unlock_page(page);
5320                 }
5321         }
5322 
5323         if (bio) {
5324                 err = submit_one_bio(bio, mirror_num, bio_flags);
5325                 if (err)
5326                         return err;
5327         }
5328 
5329         if (ret || wait != WAIT_COMPLETE)
5330                 return ret;
5331 
5332         for (i = 0; i < num_pages; i++) {
5333                 page = eb->pages[i];
5334                 wait_on_page_locked(page);
5335                 if (!PageUptodate(page))
5336                         ret = -EIO;
5337         }
5338 
5339         return ret;
5340 
5341 unlock_exit:
5342         while (locked_pages > 0) {
5343                 locked_pages--;
5344                 page = eb->pages[locked_pages];
5345                 unlock_page(page);
5346         }
5347         return ret;
5348 }
5349 
5350 void read_extent_buffer(const struct extent_buffer *eb, void *dstv,
5351                         unsigned long start, unsigned long len)
5352 {
5353         size_t cur;
5354         size_t offset;
5355         struct page *page;
5356         char *kaddr;
5357         char *dst = (char *)dstv;
5358         size_t start_offset = eb->start & ((u64)PAGE_SIZE - 1);
5359         unsigned long i = (start_offset + start) >> PAGE_SHIFT;
5360 
5361         if (start + len > eb->len) {
5362                 WARN(1, KERN_ERR "btrfs bad mapping eb start %llu len %lu, wanted %lu %lu\n",
5363                      eb->start, eb->len, start, len);
5364                 memset(dst, 0, len);
5365                 return;
5366         }
5367 
5368         offset = (start_offset + start) & (PAGE_SIZE - 1);
5369 
5370         while (len > 0) {
5371                 page = eb->pages[i];
5372 
5373                 cur = min(len, (PAGE_SIZE - offset));
5374                 kaddr = page_address(page);
5375                 memcpy(dst, kaddr + offset, cur);
5376 
5377                 dst += cur;
5378                 len -= cur;
5379                 offset = 0;
5380                 i++;
5381         }
5382 }
5383 
5384 int read_extent_buffer_to_user(const struct extent_buffer *eb,
5385                                void __user *dstv,
5386                                unsigned long start, unsigned long len)
5387 {
5388         size_t cur;
5389         size_t offset;
5390         struct page *page;
5391         char *kaddr;
5392         char __user *dst = (char __user *)dstv;
5393         size_t start_offset = eb->start & ((u64)PAGE_SIZE - 1);
5394         unsigned long i = (start_offset + start) >> PAGE_SHIFT;
5395         int ret = 0;
5396 
5397         WARN_ON(start > eb->len);
5398         WARN_ON(start + len > eb->start + eb->len);
5399 
5400         offset = (start_offset + start) & (PAGE_SIZE - 1);
5401 
5402         while (len > 0) {
5403                 page = eb->pages[i];
5404 
5405                 cur = min(len, (PAGE_SIZE - offset));
5406                 kaddr = page_address(page);
5407                 if (copy_to_user(dst, kaddr + offset, cur)) {
5408                         ret = -EFAULT;
5409                         break;
5410                 }
5411 
5412                 dst += cur;
5413                 len -= cur;
5414                 offset = 0;
5415                 i++;
5416         }
5417 
5418         return ret;
5419 }
5420 
5421 /*
5422  * return 0 if the item is found within a page.
5423  * return 1 if the item spans two pages.
5424  * return -EINVAL otherwise.
5425  */
5426 int map_private_extent_buffer(const struct extent_buffer *eb,
5427                               unsigned long start, unsigned long min_len,
5428                               char **map, unsigned long *map_start,
5429                               unsigned long *map_len)
5430 {
5431         size_t offset = start & (PAGE_SIZE - 1);
5432         char *kaddr;
5433         struct page *p;
5434         size_t start_offset = eb->start & ((u64)PAGE_SIZE - 1);
5435         unsigned long i = (start_offset + start) >> PAGE_SHIFT;
5436         unsigned long end_i = (start_offset + start + min_len - 1) >>
5437                 PAGE_SHIFT;
5438 
5439         if (start + min_len > eb->len) {
5440                 WARN(1, KERN_ERR "btrfs bad mapping eb start %llu len %lu, wanted %lu %lu\n",
5441                        eb->start, eb->len, start, min_len);
5442                 return -EINVAL;
5443         }
5444 
5445         if (i != end_i)
5446                 return 1;
5447 
5448         if (i == 0) {
5449                 offset = start_offset;
5450                 *map_start = 0;
5451         } else {
5452                 offset = 0;
5453                 *map_start = ((u64)i << PAGE_SHIFT) - start_offset;
5454         }
5455 
5456         p = eb->pages[i];
5457         kaddr = page_address(p);
5458         *map = kaddr + offset;
5459         *map_len = PAGE_SIZE - offset;
5460         return 0;
5461 }
5462 
5463 int memcmp_extent_buffer(const struct extent_buffer *eb, const void *ptrv,
5464                          unsigned long start, unsigned long len)
5465 {
5466         size_t cur;
5467         size_t offset;
5468         struct page *page;
5469         char *kaddr;
5470         char *ptr = (char *)ptrv;
5471         size_t start_offset = eb->start & ((u64)PAGE_SIZE - 1);
5472         unsigned long i = (start_offset + start) >> PAGE_SHIFT;
5473         int ret = 0;
5474 
5475         WARN_ON(start > eb->len);
5476         WARN_ON(start + len > eb->start + eb->len);
5477 
5478         offset = (start_offset + start) & (PAGE_SIZE - 1);
5479 
5480         while (len > 0) {
5481                 page = eb->pages[i];
5482 
5483                 cur = min(len, (PAGE_SIZE - offset));
5484 
5485                 kaddr = page_address(page);
5486                 ret = memcmp(ptr, kaddr + offset, cur);
5487                 if (ret)
5488                         break;
5489 
5490                 ptr += cur;
5491                 len -= cur;
5492                 offset = 0;
5493                 i++;
5494         }
5495         return ret;
5496 }
5497 
5498 void write_extent_buffer_chunk_tree_uuid(struct extent_buffer *eb,
5499                 const void *srcv)
5500 {
5501         char *kaddr;
5502 
5503         WARN_ON(!PageUptodate(eb->pages[0]));
5504         kaddr = page_address(eb->pages[0]);
5505         memcpy(kaddr + offsetof(struct btrfs_header, chunk_tree_uuid), srcv,
5506                         BTRFS_FSID_SIZE);
5507 }
5508 
5509 void write_extent_buffer_fsid(struct extent_buffer *eb, const void *srcv)
5510 {
5511         char *kaddr;
5512 
5513         WARN_ON(!PageUptodate(eb->pages[0]));
5514         kaddr = page_address(eb->pages[0]);
5515         memcpy(kaddr + offsetof(struct btrfs_header, fsid), srcv,
5516                         BTRFS_FSID_SIZE);
5517 }
5518 
5519 void write_extent_buffer(struct extent_buffer *eb, const void *srcv,
5520                          unsigned long start, unsigned long len)
5521 {
5522         size_t cur;
5523         size_t offset;
5524         struct page *page;