xref: /linux/fs/btrfs/extent_io.c (revision ef69f8d2ff09518657c3ecaf2db8408c16549829)
1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/bitops.h>
3 #include <linux/slab.h>
4 #include <linux/bio.h>
5 #include <linux/mm.h>
6 #include <linux/pagemap.h>
7 #include <linux/page-flags.h>
8 #include <linux/spinlock.h>
9 #include <linux/blkdev.h>
10 #include <linux/swap.h>
11 #include <linux/writeback.h>
12 #include <linux/pagevec.h>
13 #include <linux/prefetch.h>
14 #include <linux/cleancache.h>
15 #include "extent_io.h"
16 #include "extent_map.h"
17 #include "ctree.h"
18 #include "btrfs_inode.h"
19 #include "volumes.h"
20 #include "check-integrity.h"
21 #include "locking.h"
22 #include "rcu-string.h"
23 #include "backref.h"
24 
25 static struct kmem_cache *extent_state_cache;
26 static struct kmem_cache *extent_buffer_cache;
27 static struct bio_set *btrfs_bioset;
28 
29 static inline bool extent_state_in_tree(const struct extent_state *state)
30 {
31 	return !RB_EMPTY_NODE(&state->rb_node);
32 }
33 
34 #ifdef CONFIG_BTRFS_DEBUG
35 static LIST_HEAD(buffers);
36 static LIST_HEAD(states);
37 
38 static DEFINE_SPINLOCK(leak_lock);
39 
40 static inline
41 void btrfs_leak_debug_add(struct list_head *new, struct list_head *head)
42 {
43 	unsigned long flags;
44 
45 	spin_lock_irqsave(&leak_lock, flags);
46 	list_add(new, head);
47 	spin_unlock_irqrestore(&leak_lock, flags);
48 }
49 
50 static inline
51 void btrfs_leak_debug_del(struct list_head *entry)
52 {
53 	unsigned long flags;
54 
55 	spin_lock_irqsave(&leak_lock, flags);
56 	list_del(entry);
57 	spin_unlock_irqrestore(&leak_lock, flags);
58 }
59 
60 static inline
61 void btrfs_leak_debug_check(void)
62 {
63 	struct extent_state *state;
64 	struct extent_buffer *eb;
65 
66 	while (!list_empty(&states)) {
67 		state = list_entry(states.next, struct extent_state, leak_list);
68 		pr_err("BTRFS: state leak: start %llu end %llu state %u in tree %d refs %d\n",
69 		       state->start, state->end, state->state,
70 		       extent_state_in_tree(state),
71 		       refcount_read(&state->refs));
72 		list_del(&state->leak_list);
73 		kmem_cache_free(extent_state_cache, state);
74 	}
75 
76 	while (!list_empty(&buffers)) {
77 		eb = list_entry(buffers.next, struct extent_buffer, leak_list);
78 		pr_err("BTRFS: buffer leak start %llu len %lu refs %d\n",
79 		       eb->start, eb->len, atomic_read(&eb->refs));
80 		list_del(&eb->leak_list);
81 		kmem_cache_free(extent_buffer_cache, eb);
82 	}
83 }
84 
85 #define btrfs_debug_check_extent_io_range(tree, start, end)		\
86 	__btrfs_debug_check_extent_io_range(__func__, (tree), (start), (end))
87 static inline void __btrfs_debug_check_extent_io_range(const char *caller,
88 		struct extent_io_tree *tree, u64 start, u64 end)
89 {
90 	if (tree->ops && tree->ops->check_extent_io_range)
91 		tree->ops->check_extent_io_range(tree->private_data, caller,
92 						 start, end);
93 }
94 #else
95 #define btrfs_leak_debug_add(new, head)	do {} while (0)
96 #define btrfs_leak_debug_del(entry)	do {} while (0)
97 #define btrfs_leak_debug_check()	do {} while (0)
98 #define btrfs_debug_check_extent_io_range(c, s, e)	do {} while (0)
99 #endif
100 
101 #define BUFFER_LRU_MAX 64
102 
103 struct tree_entry {
104 	u64 start;
105 	u64 end;
106 	struct rb_node rb_node;
107 };
108 
109 struct extent_page_data {
110 	struct bio *bio;
111 	struct extent_io_tree *tree;
112 	get_extent_t *get_extent;
113 
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 void 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;
131 	if (set && (state->state & bits) == bits)
132 		return;
133 	if (!set && (state->state & bits) == 0)
134 		return;
135 	changeset->bytes_changed += state->end - state->start + 1;
136 	ret = ulist_add(&changeset->range_changed, state->start, state->end,
137 			GFP_ATOMIC);
138 	/* ENOMEM */
139 	BUG_ON(ret < 0);
140 }
141 
142 static noinline void flush_write_bio(void *data);
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 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 
531 	if ((bits_to_clear & EXTENT_DIRTY) && (state->state & EXTENT_DIRTY)) {
532 		u64 range = state->end - state->start + 1;
533 		WARN_ON(range > tree->dirty_bytes);
534 		tree->dirty_bytes -= range;
535 	}
536 	clear_state_cb(tree, state, bits);
537 	add_extent_changeset(state, bits_to_clear, changeset, 0);
538 	state->state &= ~bits_to_clear;
539 	if (wake)
540 		wake_up(&state->wq);
541 	if (state->state == 0) {
542 		next = next_state(state);
543 		if (extent_state_in_tree(state)) {
544 			rb_erase(&state->rb_node, &tree->state);
545 			RB_CLEAR_NODE(&state->rb_node);
546 			free_extent_state(state);
547 		} else {
548 			WARN_ON(1);
549 		}
550 	} else {
551 		merge_state(tree, state);
552 		next = next_state(state);
553 	}
554 	return next;
555 }
556 
557 static struct extent_state *
558 alloc_extent_state_atomic(struct extent_state *prealloc)
559 {
560 	if (!prealloc)
561 		prealloc = alloc_extent_state(GFP_ATOMIC);
562 
563 	return prealloc;
564 }
565 
566 static void extent_io_tree_panic(struct extent_io_tree *tree, int err)
567 {
568 	btrfs_panic(tree_fs_info(tree), err,
569 		    "Locking error: Extent tree was modified by another thread while locked.");
570 }
571 
572 /*
573  * clear some bits on a range in the tree.  This may require splitting
574  * or inserting elements in the tree, so the gfp mask is used to
575  * indicate which allocations or sleeping are allowed.
576  *
577  * pass 'wake' == 1 to kick any sleepers, and 'delete' == 1 to remove
578  * the given range from the tree regardless of state (ie for truncate).
579  *
580  * the range [start, end] is inclusive.
581  *
582  * This takes the tree lock, and returns 0 on success and < 0 on error.
583  */
584 static int __clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
585 			      unsigned bits, int wake, int delete,
586 			      struct extent_state **cached_state,
587 			      gfp_t mask, struct extent_changeset *changeset)
588 {
589 	struct extent_state *state;
590 	struct extent_state *cached;
591 	struct extent_state *prealloc = NULL;
592 	struct rb_node *node;
593 	u64 last_end;
594 	int err;
595 	int clear = 0;
596 
597 	btrfs_debug_check_extent_io_range(tree, start, end);
598 
599 	if (bits & EXTENT_DELALLOC)
600 		bits |= EXTENT_NORESERVE;
601 
602 	if (delete)
603 		bits |= ~EXTENT_CTLBITS;
604 	bits |= EXTENT_FIRST_DELALLOC;
605 
606 	if (bits & (EXTENT_IOBITS | EXTENT_BOUNDARY))
607 		clear = 1;
608 again:
609 	if (!prealloc && gfpflags_allow_blocking(mask)) {
610 		/*
611 		 * Don't care for allocation failure here because we might end
612 		 * up not needing the pre-allocated extent state at all, which
613 		 * is the case if we only have in the tree extent states that
614 		 * cover our input range and don't cover too any other range.
615 		 * If we end up needing a new extent state we allocate it later.
616 		 */
617 		prealloc = alloc_extent_state(mask);
618 	}
619 
620 	spin_lock(&tree->lock);
621 	if (cached_state) {
622 		cached = *cached_state;
623 
624 		if (clear) {
625 			*cached_state = NULL;
626 			cached_state = NULL;
627 		}
628 
629 		if (cached && extent_state_in_tree(cached) &&
630 		    cached->start <= start && cached->end > start) {
631 			if (clear)
632 				refcount_dec(&cached->refs);
633 			state = cached;
634 			goto hit_next;
635 		}
636 		if (clear)
637 			free_extent_state(cached);
638 	}
639 	/*
640 	 * this search will find the extents that end after
641 	 * our range starts
642 	 */
643 	node = tree_search(tree, start);
644 	if (!node)
645 		goto out;
646 	state = rb_entry(node, struct extent_state, rb_node);
647 hit_next:
648 	if (state->start > end)
649 		goto out;
650 	WARN_ON(state->end < start);
651 	last_end = state->end;
652 
653 	/* the state doesn't have the wanted bits, go ahead */
654 	if (!(state->state & bits)) {
655 		state = next_state(state);
656 		goto next;
657 	}
658 
659 	/*
660 	 *     | ---- desired range ---- |
661 	 *  | state | or
662 	 *  | ------------- state -------------- |
663 	 *
664 	 * We need to split the extent we found, and may flip
665 	 * bits on second half.
666 	 *
667 	 * If the extent we found extends past our range, we
668 	 * just split and search again.  It'll get split again
669 	 * the next time though.
670 	 *
671 	 * If the extent we found is inside our range, we clear
672 	 * the desired bit on it.
673 	 */
674 
675 	if (state->start < start) {
676 		prealloc = alloc_extent_state_atomic(prealloc);
677 		BUG_ON(!prealloc);
678 		err = split_state(tree, state, prealloc, start);
679 		if (err)
680 			extent_io_tree_panic(tree, err);
681 
682 		prealloc = NULL;
683 		if (err)
684 			goto out;
685 		if (state->end <= end) {
686 			state = clear_state_bit(tree, state, &bits, wake,
687 						changeset);
688 			goto next;
689 		}
690 		goto search_again;
691 	}
692 	/*
693 	 * | ---- desired range ---- |
694 	 *                        | state |
695 	 * We need to split the extent, and clear the bit
696 	 * on the first half
697 	 */
698 	if (state->start <= end && state->end > end) {
699 		prealloc = alloc_extent_state_atomic(prealloc);
700 		BUG_ON(!prealloc);
701 		err = split_state(tree, state, prealloc, end + 1);
702 		if (err)
703 			extent_io_tree_panic(tree, err);
704 
705 		if (wake)
706 			wake_up(&state->wq);
707 
708 		clear_state_bit(tree, prealloc, &bits, wake, changeset);
709 
710 		prealloc = NULL;
711 		goto out;
712 	}
713 
714 	state = clear_state_bit(tree, state, &bits, wake, changeset);
715 next:
716 	if (last_end == (u64)-1)
717 		goto out;
718 	start = last_end + 1;
719 	if (start <= end && state && !need_resched())
720 		goto hit_next;
721 
722 search_again:
723 	if (start > end)
724 		goto out;
725 	spin_unlock(&tree->lock);
726 	if (gfpflags_allow_blocking(mask))
727 		cond_resched();
728 	goto again;
729 
730 out:
731 	spin_unlock(&tree->lock);
732 	if (prealloc)
733 		free_extent_state(prealloc);
734 
735 	return 0;
736 
737 }
738 
739 static void wait_on_state(struct extent_io_tree *tree,
740 			  struct extent_state *state)
741 		__releases(tree->lock)
742 		__acquires(tree->lock)
743 {
744 	DEFINE_WAIT(wait);
745 	prepare_to_wait(&state->wq, &wait, TASK_UNINTERRUPTIBLE);
746 	spin_unlock(&tree->lock);
747 	schedule();
748 	spin_lock(&tree->lock);
749 	finish_wait(&state->wq, &wait);
750 }
751 
752 /*
753  * waits for one or more bits to clear on a range in the state tree.
754  * The range [start, end] is inclusive.
755  * The tree lock is taken by this function
756  */
757 static void wait_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
758 			    unsigned long bits)
759 {
760 	struct extent_state *state;
761 	struct rb_node *node;
762 
763 	btrfs_debug_check_extent_io_range(tree, start, end);
764 
765 	spin_lock(&tree->lock);
766 again:
767 	while (1) {
768 		/*
769 		 * this search will find all the extents that end after
770 		 * our range starts
771 		 */
772 		node = tree_search(tree, start);
773 process_node:
774 		if (!node)
775 			break;
776 
777 		state = rb_entry(node, struct extent_state, rb_node);
778 
779 		if (state->start > end)
780 			goto out;
781 
782 		if (state->state & bits) {
783 			start = state->start;
784 			refcount_inc(&state->refs);
785 			wait_on_state(tree, state);
786 			free_extent_state(state);
787 			goto again;
788 		}
789 		start = state->end + 1;
790 
791 		if (start > end)
792 			break;
793 
794 		if (!cond_resched_lock(&tree->lock)) {
795 			node = rb_next(node);
796 			goto process_node;
797 		}
798 	}
799 out:
800 	spin_unlock(&tree->lock);
801 }
802 
803 static void set_state_bits(struct extent_io_tree *tree,
804 			   struct extent_state *state,
805 			   unsigned *bits, struct extent_changeset *changeset)
806 {
807 	unsigned bits_to_set = *bits & ~EXTENT_CTLBITS;
808 
809 	set_state_cb(tree, state, bits);
810 	if ((bits_to_set & EXTENT_DIRTY) && !(state->state & EXTENT_DIRTY)) {
811 		u64 range = state->end - state->start + 1;
812 		tree->dirty_bytes += range;
813 	}
814 	add_extent_changeset(state, bits_to_set, changeset, 1);
815 	state->state |= bits_to_set;
816 }
817 
818 static void cache_state_if_flags(struct extent_state *state,
819 				 struct extent_state **cached_ptr,
820 				 unsigned flags)
821 {
822 	if (cached_ptr && !(*cached_ptr)) {
823 		if (!flags || (state->state & flags)) {
824 			*cached_ptr = state;
825 			refcount_inc(&state->refs);
826 		}
827 	}
828 }
829 
830 static void cache_state(struct extent_state *state,
831 			struct extent_state **cached_ptr)
832 {
833 	return cache_state_if_flags(state, cached_ptr,
834 				    EXTENT_IOBITS | EXTENT_BOUNDARY);
835 }
836 
837 /*
838  * set some bits on a range in the tree.  This may require allocations or
839  * sleeping, so the gfp mask is used to indicate what is allowed.
840  *
841  * If any of the exclusive bits are set, this will fail with -EEXIST if some
842  * part of the range already has the desired bits set.  The start of the
843  * existing range is returned in failed_start in this case.
844  *
845  * [start, end] is inclusive This takes the tree lock.
846  */
847 
848 static int __must_check
849 __set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
850 		 unsigned bits, unsigned exclusive_bits,
851 		 u64 *failed_start, struct extent_state **cached_state,
852 		 gfp_t mask, struct extent_changeset *changeset)
853 {
854 	struct extent_state *state;
855 	struct extent_state *prealloc = NULL;
856 	struct rb_node *node;
857 	struct rb_node **p;
858 	struct rb_node *parent;
859 	int err = 0;
860 	u64 last_start;
861 	u64 last_end;
862 
863 	btrfs_debug_check_extent_io_range(tree, start, end);
864 
865 	bits |= EXTENT_FIRST_DELALLOC;
866 again:
867 	if (!prealloc && gfpflags_allow_blocking(mask)) {
868 		/*
869 		 * Don't care for allocation failure here because we might end
870 		 * up not needing the pre-allocated extent state at all, which
871 		 * is the case if we only have in the tree extent states that
872 		 * cover our input range and don't cover too any other range.
873 		 * If we end up needing a new extent state we allocate it later.
874 		 */
875 		prealloc = alloc_extent_state(mask);
876 	}
877 
878 	spin_lock(&tree->lock);
879 	if (cached_state && *cached_state) {
880 		state = *cached_state;
881 		if (state->start <= start && state->end > start &&
882 		    extent_state_in_tree(state)) {
883 			node = &state->rb_node;
884 			goto hit_next;
885 		}
886 	}
887 	/*
888 	 * this search will find all the extents that end after
889 	 * our range starts.
890 	 */
891 	node = tree_search_for_insert(tree, start, &p, &parent);
892 	if (!node) {
893 		prealloc = alloc_extent_state_atomic(prealloc);
894 		BUG_ON(!prealloc);
895 		err = insert_state(tree, prealloc, start, end,
896 				   &p, &parent, &bits, changeset);
897 		if (err)
898 			extent_io_tree_panic(tree, err);
899 
900 		cache_state(prealloc, cached_state);
901 		prealloc = NULL;
902 		goto out;
903 	}
904 	state = rb_entry(node, struct extent_state, rb_node);
905 hit_next:
906 	last_start = state->start;
907 	last_end = state->end;
908 
909 	/*
910 	 * | ---- desired range ---- |
911 	 * | state |
912 	 *
913 	 * Just lock what we found and keep going
914 	 */
915 	if (state->start == start && state->end <= end) {
916 		if (state->state & exclusive_bits) {
917 			*failed_start = state->start;
918 			err = -EEXIST;
919 			goto out;
920 		}
921 
922 		set_state_bits(tree, state, &bits, changeset);
923 		cache_state(state, cached_state);
924 		merge_state(tree, state);
925 		if (last_end == (u64)-1)
926 			goto out;
927 		start = last_end + 1;
928 		state = next_state(state);
929 		if (start < end && state && state->start == start &&
930 		    !need_resched())
931 			goto hit_next;
932 		goto search_again;
933 	}
934 
935 	/*
936 	 *     | ---- desired range ---- |
937 	 * | state |
938 	 *   or
939 	 * | ------------- state -------------- |
940 	 *
941 	 * We need to split the extent we found, and may flip bits on
942 	 * second half.
943 	 *
944 	 * If the extent we found extends past our
945 	 * range, we just split and search again.  It'll get split
946 	 * again the next time though.
947 	 *
948 	 * If the extent we found is inside our range, we set the
949 	 * desired bit on it.
950 	 */
951 	if (state->start < start) {
952 		if (state->state & exclusive_bits) {
953 			*failed_start = start;
954 			err = -EEXIST;
955 			goto out;
956 		}
957 
958 		prealloc = alloc_extent_state_atomic(prealloc);
959 		BUG_ON(!prealloc);
960 		err = split_state(tree, state, prealloc, start);
961 		if (err)
962 			extent_io_tree_panic(tree, err);
963 
964 		prealloc = NULL;
965 		if (err)
966 			goto out;
967 		if (state->end <= end) {
968 			set_state_bits(tree, state, &bits, changeset);
969 			cache_state(state, cached_state);
970 			merge_state(tree, state);
971 			if (last_end == (u64)-1)
972 				goto out;
973 			start = last_end + 1;
974 			state = next_state(state);
975 			if (start < end && state && state->start == start &&
976 			    !need_resched())
977 				goto hit_next;
978 		}
979 		goto search_again;
980 	}
981 	/*
982 	 * | ---- desired range ---- |
983 	 *     | state | or               | state |
984 	 *
985 	 * There's a hole, we need to insert something in it and
986 	 * ignore the extent we found.
987 	 */
988 	if (state->start > start) {
989 		u64 this_end;
990 		if (end < last_start)
991 			this_end = end;
992 		else
993 			this_end = last_start - 1;
994 
995 		prealloc = alloc_extent_state_atomic(prealloc);
996 		BUG_ON(!prealloc);
997 
998 		/*
999 		 * Avoid to free 'prealloc' if it can be merged with
1000 		 * the later extent.
1001 		 */
1002 		err = insert_state(tree, prealloc, start, this_end,
1003 				   NULL, NULL, &bits, changeset);
1004 		if (err)
1005 			extent_io_tree_panic(tree, err);
1006 
1007 		cache_state(prealloc, cached_state);
1008 		prealloc = NULL;
1009 		start = this_end + 1;
1010 		goto search_again;
1011 	}
1012 	/*
1013 	 * | ---- desired range ---- |
1014 	 *                        | state |
1015 	 * We need to split the extent, and set the bit
1016 	 * on the first half
1017 	 */
1018 	if (state->start <= end && state->end > end) {
1019 		if (state->state & exclusive_bits) {
1020 			*failed_start = start;
1021 			err = -EEXIST;
1022 			goto out;
1023 		}
1024 
1025 		prealloc = alloc_extent_state_atomic(prealloc);
1026 		BUG_ON(!prealloc);
1027 		err = split_state(tree, state, prealloc, end + 1);
1028 		if (err)
1029 			extent_io_tree_panic(tree, err);
1030 
1031 		set_state_bits(tree, prealloc, &bits, changeset);
1032 		cache_state(prealloc, cached_state);
1033 		merge_state(tree, prealloc);
1034 		prealloc = NULL;
1035 		goto out;
1036 	}
1037 
1038 search_again:
1039 	if (start > end)
1040 		goto out;
1041 	spin_unlock(&tree->lock);
1042 	if (gfpflags_allow_blocking(mask))
1043 		cond_resched();
1044 	goto again;
1045 
1046 out:
1047 	spin_unlock(&tree->lock);
1048 	if (prealloc)
1049 		free_extent_state(prealloc);
1050 
1051 	return err;
1052 
1053 }
1054 
1055 int set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
1056 		   unsigned bits, u64 * failed_start,
1057 		   struct extent_state **cached_state, gfp_t mask)
1058 {
1059 	return __set_extent_bit(tree, start, end, bits, 0, failed_start,
1060 				cached_state, mask, NULL);
1061 }
1062 
1063 
1064 /**
1065  * convert_extent_bit - convert all bits in a given range from one bit to
1066  * 			another
1067  * @tree:	the io tree to search
1068  * @start:	the start offset in bytes
1069  * @end:	the end offset in bytes (inclusive)
1070  * @bits:	the bits to set in this range
1071  * @clear_bits:	the bits to clear in this range
1072  * @cached_state:	state that we're going to cache
1073  *
1074  * This will go through and set bits for the given range.  If any states exist
1075  * already in this range they are set with the given bit and cleared of the
1076  * clear_bits.  This is only meant to be used by things that are mergeable, ie
1077  * converting from say DELALLOC to DIRTY.  This is not meant to be used with
1078  * boundary bits like LOCK.
1079  *
1080  * All allocations are done with GFP_NOFS.
1081  */
1082 int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
1083 		       unsigned bits, unsigned clear_bits,
1084 		       struct extent_state **cached_state)
1085 {
1086 	struct extent_state *state;
1087 	struct extent_state *prealloc = NULL;
1088 	struct rb_node *node;
1089 	struct rb_node **p;
1090 	struct rb_node *parent;
1091 	int err = 0;
1092 	u64 last_start;
1093 	u64 last_end;
1094 	bool first_iteration = true;
1095 
1096 	btrfs_debug_check_extent_io_range(tree, start, end);
1097 
1098 again:
1099 	if (!prealloc) {
1100 		/*
1101 		 * Best effort, don't worry if extent state allocation fails
1102 		 * here for the first iteration. We might have a cached state
1103 		 * that matches exactly the target range, in which case no
1104 		 * extent state allocations are needed. We'll only know this
1105 		 * after locking the tree.
1106 		 */
1107 		prealloc = alloc_extent_state(GFP_NOFS);
1108 		if (!prealloc && !first_iteration)
1109 			return -ENOMEM;
1110 	}
1111 
1112 	spin_lock(&tree->lock);
1113 	if (cached_state && *cached_state) {
1114 		state = *cached_state;
1115 		if (state->start <= start && state->end > start &&
1116 		    extent_state_in_tree(state)) {
1117 			node = &state->rb_node;
1118 			goto hit_next;
1119 		}
1120 	}
1121 
1122 	/*
1123 	 * this search will find all the extents that end after
1124 	 * our range starts.
1125 	 */
1126 	node = tree_search_for_insert(tree, start, &p, &parent);
1127 	if (!node) {
1128 		prealloc = alloc_extent_state_atomic(prealloc);
1129 		if (!prealloc) {
1130 			err = -ENOMEM;
1131 			goto out;
1132 		}
1133 		err = insert_state(tree, prealloc, start, end,
1134 				   &p, &parent, &bits, NULL);
1135 		if (err)
1136 			extent_io_tree_panic(tree, err);
1137 		cache_state(prealloc, cached_state);
1138 		prealloc = NULL;
1139 		goto out;
1140 	}
1141 	state = rb_entry(node, struct extent_state, rb_node);
1142 hit_next:
1143 	last_start = state->start;
1144 	last_end = state->end;
1145 
1146 	/*
1147 	 * | ---- desired range ---- |
1148 	 * | state |
1149 	 *
1150 	 * Just lock what we found and keep going
1151 	 */
1152 	if (state->start == start && state->end <= end) {
1153 		set_state_bits(tree, state, &bits, NULL);
1154 		cache_state(state, cached_state);
1155 		state = clear_state_bit(tree, state, &clear_bits, 0, NULL);
1156 		if (last_end == (u64)-1)
1157 			goto out;
1158 		start = last_end + 1;
1159 		if (start < end && state && state->start == start &&
1160 		    !need_resched())
1161 			goto hit_next;
1162 		goto search_again;
1163 	}
1164 
1165 	/*
1166 	 *     | ---- desired range ---- |
1167 	 * | state |
1168 	 *   or
1169 	 * | ------------- state -------------- |
1170 	 *
1171 	 * We need to split the extent we found, and may flip bits on
1172 	 * second half.
1173 	 *
1174 	 * If the extent we found extends past our
1175 	 * range, we just split and search again.  It'll get split
1176 	 * again the next time though.
1177 	 *
1178 	 * If the extent we found is inside our range, we set the
1179 	 * desired bit on it.
1180 	 */
1181 	if (state->start < start) {
1182 		prealloc = alloc_extent_state_atomic(prealloc);
1183 		if (!prealloc) {
1184 			err = -ENOMEM;
1185 			goto out;
1186 		}
1187 		err = split_state(tree, state, prealloc, start);
1188 		if (err)
1189 			extent_io_tree_panic(tree, err);
1190 		prealloc = NULL;
1191 		if (err)
1192 			goto out;
1193 		if (state->end <= end) {
1194 			set_state_bits(tree, state, &bits, NULL);
1195 			cache_state(state, cached_state);
1196 			state = clear_state_bit(tree, state, &clear_bits, 0,
1197 						NULL);
1198 			if (last_end == (u64)-1)
1199 				goto out;
1200 			start = last_end + 1;
1201 			if (start < end && state && state->start == start &&
1202 			    !need_resched())
1203 				goto hit_next;
1204 		}
1205 		goto search_again;
1206 	}
1207 	/*
1208 	 * | ---- desired range ---- |
1209 	 *     | state | or               | state |
1210 	 *
1211 	 * There's a hole, we need to insert something in it and
1212 	 * ignore the extent we found.
1213 	 */
1214 	if (state->start > start) {
1215 		u64 this_end;
1216 		if (end < last_start)
1217 			this_end = end;
1218 		else
1219 			this_end = last_start - 1;
1220 
1221 		prealloc = alloc_extent_state_atomic(prealloc);
1222 		if (!prealloc) {
1223 			err = -ENOMEM;
1224 			goto out;
1225 		}
1226 
1227 		/*
1228 		 * Avoid to free 'prealloc' if it can be merged with
1229 		 * the later extent.
1230 		 */
1231 		err = insert_state(tree, prealloc, start, this_end,
1232 				   NULL, NULL, &bits, NULL);
1233 		if (err)
1234 			extent_io_tree_panic(tree, err);
1235 		cache_state(prealloc, cached_state);
1236 		prealloc = NULL;
1237 		start = this_end + 1;
1238 		goto search_again;
1239 	}
1240 	/*
1241 	 * | ---- desired range ---- |
1242 	 *                        | state |
1243 	 * We need to split the extent, and set the bit
1244 	 * on the first half
1245 	 */
1246 	if (state->start <= end && state->end > end) {
1247 		prealloc = alloc_extent_state_atomic(prealloc);
1248 		if (!prealloc) {
1249 			err = -ENOMEM;
1250 			goto out;
1251 		}
1252 
1253 		err = split_state(tree, state, prealloc, end + 1);
1254 		if (err)
1255 			extent_io_tree_panic(tree, err);
1256 
1257 		set_state_bits(tree, prealloc, &bits, NULL);
1258 		cache_state(prealloc, cached_state);
1259 		clear_state_bit(tree, prealloc, &clear_bits, 0, NULL);
1260 		prealloc = NULL;
1261 		goto out;
1262 	}
1263 
1264 search_again:
1265 	if (start > end)
1266 		goto out;
1267 	spin_unlock(&tree->lock);
1268 	cond_resched();
1269 	first_iteration = false;
1270 	goto again;
1271 
1272 out:
1273 	spin_unlock(&tree->lock);
1274 	if (prealloc)
1275 		free_extent_state(prealloc);
1276 
1277 	return err;
1278 }
1279 
1280 /* wrappers around set/clear extent bit */
1281 int set_record_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
1282 			   unsigned bits, struct extent_changeset *changeset)
1283 {
1284 	/*
1285 	 * We don't support EXTENT_LOCKED yet, as current changeset will
1286 	 * record any bits changed, so for EXTENT_LOCKED case, it will
1287 	 * either fail with -EEXIST or changeset will record the whole
1288 	 * range.
1289 	 */
1290 	BUG_ON(bits & EXTENT_LOCKED);
1291 
1292 	return __set_extent_bit(tree, start, end, bits, 0, NULL, NULL, GFP_NOFS,
1293 				changeset);
1294 }
1295 
1296 int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
1297 		     unsigned bits, int wake, int delete,
1298 		     struct extent_state **cached, gfp_t mask)
1299 {
1300 	return __clear_extent_bit(tree, start, end, bits, wake, delete,
1301 				  cached, mask, NULL);
1302 }
1303 
1304 int clear_record_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
1305 		unsigned bits, struct extent_changeset *changeset)
1306 {
1307 	/*
1308 	 * Don't support EXTENT_LOCKED case, same reason as
1309 	 * set_record_extent_bits().
1310 	 */
1311 	BUG_ON(bits & EXTENT_LOCKED);
1312 
1313 	return __clear_extent_bit(tree, start, end, bits, 0, 0, NULL, GFP_NOFS,
1314 				  changeset);
1315 }
1316 
1317 /*
1318  * either insert or lock state struct between start and end use mask to tell
1319  * us if waiting is desired.
1320  */
1321 int lock_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
1322 		     struct extent_state **cached_state)
1323 {
1324 	int err;
1325 	u64 failed_start;
1326 
1327 	while (1) {
1328 		err = __set_extent_bit(tree, start, end, EXTENT_LOCKED,
1329 				       EXTENT_LOCKED, &failed_start,
1330 				       cached_state, GFP_NOFS, NULL);
1331 		if (err == -EEXIST) {
1332 			wait_extent_bit(tree, failed_start, end, EXTENT_LOCKED);
1333 			start = failed_start;
1334 		} else
1335 			break;
1336 		WARN_ON(start > end);
1337 	}
1338 	return err;
1339 }
1340 
1341 int try_lock_extent(struct extent_io_tree *tree, u64 start, u64 end)
1342 {
1343 	int err;
1344 	u64 failed_start;
1345 
1346 	err = __set_extent_bit(tree, start, end, EXTENT_LOCKED, EXTENT_LOCKED,
1347 			       &failed_start, NULL, GFP_NOFS, NULL);
1348 	if (err == -EEXIST) {
1349 		if (failed_start > start)
1350 			clear_extent_bit(tree, start, failed_start - 1,
1351 					 EXTENT_LOCKED, 1, 0, NULL, GFP_NOFS);
1352 		return 0;
1353 	}
1354 	return 1;
1355 }
1356 
1357 void extent_range_clear_dirty_for_io(struct inode *inode, u64 start, u64 end)
1358 {
1359 	unsigned long index = start >> PAGE_SHIFT;
1360 	unsigned long end_index = end >> PAGE_SHIFT;
1361 	struct page *page;
1362 
1363 	while (index <= end_index) {
1364 		page = find_get_page(inode->i_mapping, index);
1365 		BUG_ON(!page); /* Pages should be in the extent_io_tree */
1366 		clear_page_dirty_for_io(page);
1367 		put_page(page);
1368 		index++;
1369 	}
1370 }
1371 
1372 void extent_range_redirty_for_io(struct inode *inode, u64 start, u64 end)
1373 {
1374 	unsigned long index = start >> PAGE_SHIFT;
1375 	unsigned long end_index = end >> PAGE_SHIFT;
1376 	struct page *page;
1377 
1378 	while (index <= end_index) {
1379 		page = find_get_page(inode->i_mapping, index);
1380 		BUG_ON(!page); /* Pages should be in the extent_io_tree */
1381 		__set_page_dirty_nobuffers(page);
1382 		account_page_redirty(page);
1383 		put_page(page);
1384 		index++;
1385 	}
1386 }
1387 
1388 /*
1389  * helper function to set both pages and extents in the tree writeback
1390  */
1391 static void set_range_writeback(struct extent_io_tree *tree, u64 start, u64 end)
1392 {
1393 	tree->ops->set_range_writeback(tree->private_data, start, end);
1394 }
1395 
1396 /* find the first state struct with 'bits' set after 'start', and
1397  * return it.  tree->lock must be held.  NULL will returned if
1398  * nothing was found after 'start'
1399  */
1400 static struct extent_state *
1401 find_first_extent_bit_state(struct extent_io_tree *tree,
1402 			    u64 start, unsigned bits)
1403 {
1404 	struct rb_node *node;
1405 	struct extent_state *state;
1406 
1407 	/*
1408 	 * this search will find all the extents that end after
1409 	 * our range starts.
1410 	 */
1411 	node = tree_search(tree, start);
1412 	if (!node)
1413 		goto out;
1414 
1415 	while (1) {
1416 		state = rb_entry(node, struct extent_state, rb_node);
1417 		if (state->end >= start && (state->state & bits))
1418 			return state;
1419 
1420 		node = rb_next(node);
1421 		if (!node)
1422 			break;
1423 	}
1424 out:
1425 	return NULL;
1426 }
1427 
1428 /*
1429  * find the first offset in the io tree with 'bits' set. zero is
1430  * returned if we find something, and *start_ret and *end_ret are
1431  * set to reflect the state struct that was found.
1432  *
1433  * If nothing was found, 1 is returned. If found something, return 0.
1434  */
1435 int find_first_extent_bit(struct extent_io_tree *tree, u64 start,
1436 			  u64 *start_ret, u64 *end_ret, unsigned bits,
1437 			  struct extent_state **cached_state)
1438 {
1439 	struct extent_state *state;
1440 	struct rb_node *n;
1441 	int ret = 1;
1442 
1443 	spin_lock(&tree->lock);
1444 	if (cached_state && *cached_state) {
1445 		state = *cached_state;
1446 		if (state->end == start - 1 && extent_state_in_tree(state)) {
1447 			n = rb_next(&state->rb_node);
1448 			while (n) {
1449 				state = rb_entry(n, struct extent_state,
1450 						 rb_node);
1451 				if (state->state & bits)
1452 					goto got_it;
1453 				n = rb_next(n);
1454 			}
1455 			free_extent_state(*cached_state);
1456 			*cached_state = NULL;
1457 			goto out;
1458 		}
1459 		free_extent_state(*cached_state);
1460 		*cached_state = NULL;
1461 	}
1462 
1463 	state = find_first_extent_bit_state(tree, start, bits);
1464 got_it:
1465 	if (state) {
1466 		cache_state_if_flags(state, cached_state, 0);
1467 		*start_ret = state->start;
1468 		*end_ret = state->end;
1469 		ret = 0;
1470 	}
1471 out:
1472 	spin_unlock(&tree->lock);
1473 	return ret;
1474 }
1475 
1476 /*
1477  * find a contiguous range of bytes in the file marked as delalloc, not
1478  * more than 'max_bytes'.  start and end are used to return the range,
1479  *
1480  * 1 is returned if we find something, 0 if nothing was in the tree
1481  */
1482 static noinline u64 find_delalloc_range(struct extent_io_tree *tree,
1483 					u64 *start, u64 *end, u64 max_bytes,
1484 					struct extent_state **cached_state)
1485 {
1486 	struct rb_node *node;
1487 	struct extent_state *state;
1488 	u64 cur_start = *start;
1489 	u64 found = 0;
1490 	u64 total_bytes = 0;
1491 
1492 	spin_lock(&tree->lock);
1493 
1494 	/*
1495 	 * this search will find all the extents that end after
1496 	 * our range starts.
1497 	 */
1498 	node = tree_search(tree, cur_start);
1499 	if (!node) {
1500 		if (!found)
1501 			*end = (u64)-1;
1502 		goto out;
1503 	}
1504 
1505 	while (1) {
1506 		state = rb_entry(node, struct extent_state, rb_node);
1507 		if (found && (state->start != cur_start ||
1508 			      (state->state & EXTENT_BOUNDARY))) {
1509 			goto out;
1510 		}
1511 		if (!(state->state & EXTENT_DELALLOC)) {
1512 			if (!found)
1513 				*end = state->end;
1514 			goto out;
1515 		}
1516 		if (!found) {
1517 			*start = state->start;
1518 			*cached_state = state;
1519 			refcount_inc(&state->refs);
1520 		}
1521 		found++;
1522 		*end = state->end;
1523 		cur_start = state->end + 1;
1524 		node = rb_next(node);
1525 		total_bytes += state->end - state->start + 1;
1526 		if (total_bytes >= max_bytes)
1527 			break;
1528 		if (!node)
1529 			break;
1530 	}
1531 out:
1532 	spin_unlock(&tree->lock);
1533 	return found;
1534 }
1535 
1536 static int __process_pages_contig(struct address_space *mapping,
1537 				  struct page *locked_page,
1538 				  pgoff_t start_index, pgoff_t end_index,
1539 				  unsigned long page_ops, pgoff_t *index_ret);
1540 
1541 static noinline void __unlock_for_delalloc(struct inode *inode,
1542 					   struct page *locked_page,
1543 					   u64 start, u64 end)
1544 {
1545 	unsigned long index = start >> PAGE_SHIFT;
1546 	unsigned long end_index = end >> PAGE_SHIFT;
1547 
1548 	ASSERT(locked_page);
1549 	if (index == locked_page->index && end_index == index)
1550 		return;
1551 
1552 	__process_pages_contig(inode->i_mapping, locked_page, index, end_index,
1553 			       PAGE_UNLOCK, NULL);
1554 }
1555 
1556 static noinline int lock_delalloc_pages(struct inode *inode,
1557 					struct page *locked_page,
1558 					u64 delalloc_start,
1559 					u64 delalloc_end)
1560 {
1561 	unsigned long index = delalloc_start >> PAGE_SHIFT;
1562 	unsigned long index_ret = index;
1563 	unsigned long end_index = delalloc_end >> PAGE_SHIFT;
1564 	int ret;
1565 
1566 	ASSERT(locked_page);
1567 	if (index == locked_page->index && index == end_index)
1568 		return 0;
1569 
1570 	ret = __process_pages_contig(inode->i_mapping, locked_page, index,
1571 				     end_index, PAGE_LOCK, &index_ret);
1572 	if (ret == -EAGAIN)
1573 		__unlock_for_delalloc(inode, locked_page, delalloc_start,
1574 				      (u64)index_ret << PAGE_SHIFT);
1575 	return ret;
1576 }
1577 
1578 /*
1579  * find a contiguous range of bytes in the file marked as delalloc, not
1580  * more than 'max_bytes'.  start and end are used to return the range,
1581  *
1582  * 1 is returned if we find something, 0 if nothing was in the tree
1583  */
1584 STATIC u64 find_lock_delalloc_range(struct inode *inode,
1585 				    struct extent_io_tree *tree,
1586 				    struct page *locked_page, u64 *start,
1587 				    u64 *end, u64 max_bytes)
1588 {
1589 	u64 delalloc_start;
1590 	u64 delalloc_end;
1591 	u64 found;
1592 	struct extent_state *cached_state = NULL;
1593 	int ret;
1594 	int loops = 0;
1595 
1596 again:
1597 	/* step one, find a bunch of delalloc bytes starting at start */
1598 	delalloc_start = *start;
1599 	delalloc_end = 0;
1600 	found = find_delalloc_range(tree, &delalloc_start, &delalloc_end,
1601 				    max_bytes, &cached_state);
1602 	if (!found || delalloc_end <= *start) {
1603 		*start = delalloc_start;
1604 		*end = delalloc_end;
1605 		free_extent_state(cached_state);
1606 		return 0;
1607 	}
1608 
1609 	/*
1610 	 * start comes from the offset of locked_page.  We have to lock
1611 	 * pages in order, so we can't process delalloc bytes before
1612 	 * locked_page
1613 	 */
1614 	if (delalloc_start < *start)
1615 		delalloc_start = *start;
1616 
1617 	/*
1618 	 * make sure to limit the number of pages we try to lock down
1619 	 */
1620 	if (delalloc_end + 1 - delalloc_start > max_bytes)
1621 		delalloc_end = delalloc_start + max_bytes - 1;
1622 
1623 	/* step two, lock all the pages after the page that has start */
1624 	ret = lock_delalloc_pages(inode, locked_page,
1625 				  delalloc_start, delalloc_end);
1626 	if (ret == -EAGAIN) {
1627 		/* some of the pages are gone, lets avoid looping by
1628 		 * shortening the size of the delalloc range we're searching
1629 		 */
1630 		free_extent_state(cached_state);
1631 		cached_state = NULL;
1632 		if (!loops) {
1633 			max_bytes = PAGE_SIZE;
1634 			loops = 1;
1635 			goto again;
1636 		} else {
1637 			found = 0;
1638 			goto out_failed;
1639 		}
1640 	}
1641 	BUG_ON(ret); /* Only valid values are 0 and -EAGAIN */
1642 
1643 	/* step three, lock the state bits for the whole range */
1644 	lock_extent_bits(tree, delalloc_start, delalloc_end, &cached_state);
1645 
1646 	/* then test to make sure it is all still delalloc */
1647 	ret = test_range_bit(tree, delalloc_start, delalloc_end,
1648 			     EXTENT_DELALLOC, 1, cached_state);
1649 	if (!ret) {
1650 		unlock_extent_cached(tree, delalloc_start, delalloc_end,
1651 				     &cached_state, GFP_NOFS);
1652 		__unlock_for_delalloc(inode, locked_page,
1653 			      delalloc_start, delalloc_end);
1654 		cond_resched();
1655 		goto again;
1656 	}
1657 	free_extent_state(cached_state);
1658 	*start = delalloc_start;
1659 	*end = delalloc_end;
1660 out_failed:
1661 	return found;
1662 }
1663 
1664 static int __process_pages_contig(struct address_space *mapping,
1665 				  struct page *locked_page,
1666 				  pgoff_t start_index, pgoff_t end_index,
1667 				  unsigned long page_ops, pgoff_t *index_ret)
1668 {
1669 	unsigned long nr_pages = end_index - start_index + 1;
1670 	unsigned long pages_locked = 0;
1671 	pgoff_t index = start_index;
1672 	struct page *pages[16];
1673 	unsigned ret;
1674 	int err = 0;
1675 	int i;
1676 
1677 	if (page_ops & PAGE_LOCK) {
1678 		ASSERT(page_ops == PAGE_LOCK);
1679 		ASSERT(index_ret && *index_ret == start_index);
1680 	}
1681 
1682 	if ((page_ops & PAGE_SET_ERROR) && nr_pages > 0)
1683 		mapping_set_error(mapping, -EIO);
1684 
1685 	while (nr_pages > 0) {
1686 		ret = find_get_pages_contig(mapping, index,
1687 				     min_t(unsigned long,
1688 				     nr_pages, ARRAY_SIZE(pages)), pages);
1689 		if (ret == 0) {
1690 			/*
1691 			 * Only if we're going to lock these pages,
1692 			 * can we find nothing at @index.
1693 			 */
1694 			ASSERT(page_ops & PAGE_LOCK);
1695 			err = -EAGAIN;
1696 			goto out;
1697 		}
1698 
1699 		for (i = 0; i < ret; i++) {
1700 			if (page_ops & PAGE_SET_PRIVATE2)
1701 				SetPagePrivate2(pages[i]);
1702 
1703 			if (pages[i] == locked_page) {
1704 				put_page(pages[i]);
1705 				pages_locked++;
1706 				continue;
1707 			}
1708 			if (page_ops & PAGE_CLEAR_DIRTY)
1709 				clear_page_dirty_for_io(pages[i]);
1710 			if (page_ops & PAGE_SET_WRITEBACK)
1711 				set_page_writeback(pages[i]);
1712 			if (page_ops & PAGE_SET_ERROR)
1713 				SetPageError(pages[i]);
1714 			if (page_ops & PAGE_END_WRITEBACK)
1715 				end_page_writeback(pages[i]);
1716 			if (page_ops & PAGE_UNLOCK)
1717 				unlock_page(pages[i]);
1718 			if (page_ops & PAGE_LOCK) {
1719 				lock_page(pages[i]);
1720 				if (!PageDirty(pages[i]) ||
1721 				    pages[i]->mapping != mapping) {
1722 					unlock_page(pages[i]);
1723 					put_page(pages[i]);
1724 					err = -EAGAIN;
1725 					goto out;
1726 				}
1727 			}
1728 			put_page(pages[i]);
1729 			pages_locked++;
1730 		}
1731 		nr_pages -= ret;
1732 		index += ret;
1733 		cond_resched();
1734 	}
1735 out:
1736 	if (err && index_ret)
1737 		*index_ret = start_index + pages_locked - 1;
1738 	return err;
1739 }
1740 
1741 void extent_clear_unlock_delalloc(struct inode *inode, u64 start, u64 end,
1742 				 u64 delalloc_end, struct page *locked_page,
1743 				 unsigned clear_bits,
1744 				 unsigned long page_ops)
1745 {
1746 	clear_extent_bit(&BTRFS_I(inode)->io_tree, start, end, clear_bits, 1, 0,
1747 			 NULL, GFP_NOFS);
1748 
1749 	__process_pages_contig(inode->i_mapping, locked_page,
1750 			       start >> PAGE_SHIFT, end >> PAGE_SHIFT,
1751 			       page_ops, NULL);
1752 }
1753 
1754 /*
1755  * count the number of bytes in the tree that have a given bit(s)
1756  * set.  This can be fairly slow, except for EXTENT_DIRTY which is
1757  * cached.  The total number found is returned.
1758  */
1759 u64 count_range_bits(struct extent_io_tree *tree,
1760 		     u64 *start, u64 search_end, u64 max_bytes,
1761 		     unsigned bits, int contig)
1762 {
1763 	struct rb_node *node;
1764 	struct extent_state *state;
1765 	u64 cur_start = *start;
1766 	u64 total_bytes = 0;
1767 	u64 last = 0;
1768 	int found = 0;
1769 
1770 	if (WARN_ON(search_end <= cur_start))
1771 		return 0;
1772 
1773 	spin_lock(&tree->lock);
1774 	if (cur_start == 0 && bits == EXTENT_DIRTY) {
1775 		total_bytes = tree->dirty_bytes;
1776 		goto out;
1777 	}
1778 	/*
1779 	 * this search will find all the extents that end after
1780 	 * our range starts.
1781 	 */
1782 	node = tree_search(tree, cur_start);
1783 	if (!node)
1784 		goto out;
1785 
1786 	while (1) {
1787 		state = rb_entry(node, struct extent_state, rb_node);
1788 		if (state->start > search_end)
1789 			break;
1790 		if (contig && found && state->start > last + 1)
1791 			break;
1792 		if (state->end >= cur_start && (state->state & bits) == bits) {
1793 			total_bytes += min(search_end, state->end) + 1 -
1794 				       max(cur_start, state->start);
1795 			if (total_bytes >= max_bytes)
1796 				break;
1797 			if (!found) {
1798 				*start = max(cur_start, state->start);
1799 				found = 1;
1800 			}
1801 			last = state->end;
1802 		} else if (contig && found) {
1803 			break;
1804 		}
1805 		node = rb_next(node);
1806 		if (!node)
1807 			break;
1808 	}
1809 out:
1810 	spin_unlock(&tree->lock);
1811 	return total_bytes;
1812 }
1813 
1814 /*
1815  * set the private field for a given byte offset in the tree.  If there isn't
1816  * an extent_state there already, this does nothing.
1817  */
1818 static noinline int set_state_failrec(struct extent_io_tree *tree, u64 start,
1819 		struct io_failure_record *failrec)
1820 {
1821 	struct rb_node *node;
1822 	struct extent_state *state;
1823 	int ret = 0;
1824 
1825 	spin_lock(&tree->lock);
1826 	/*
1827 	 * this search will find all the extents that end after
1828 	 * our range starts.
1829 	 */
1830 	node = tree_search(tree, start);
1831 	if (!node) {
1832 		ret = -ENOENT;
1833 		goto out;
1834 	}
1835 	state = rb_entry(node, struct extent_state, rb_node);
1836 	if (state->start != start) {
1837 		ret = -ENOENT;
1838 		goto out;
1839 	}
1840 	state->failrec = failrec;
1841 out:
1842 	spin_unlock(&tree->lock);
1843 	return ret;
1844 }
1845 
1846 static noinline int get_state_failrec(struct extent_io_tree *tree, u64 start,
1847 		struct io_failure_record **failrec)
1848 {
1849 	struct rb_node *node;
1850 	struct extent_state *state;
1851 	int ret = 0;
1852 
1853 	spin_lock(&tree->lock);
1854 	/*
1855 	 * this search will find all the extents that end after
1856 	 * our range starts.
1857 	 */
1858 	node = tree_search(tree, start);
1859 	if (!node) {
1860 		ret = -ENOENT;
1861 		goto out;
1862 	}
1863 	state = rb_entry(node, struct extent_state, rb_node);
1864 	if (state->start != start) {
1865 		ret = -ENOENT;
1866 		goto out;
1867 	}
1868 	*failrec = state->failrec;
1869 out:
1870 	spin_unlock(&tree->lock);
1871 	return ret;
1872 }
1873 
1874 /*
1875  * searches a range in the state tree for a given mask.
1876  * If 'filled' == 1, this returns 1 only if every extent in the tree
1877  * has the bits set.  Otherwise, 1 is returned if any bit in the
1878  * range is found set.
1879  */
1880 int test_range_bit(struct extent_io_tree *tree, u64 start, u64 end,
1881 		   unsigned bits, int filled, struct extent_state *cached)
1882 {
1883 	struct extent_state *state = NULL;
1884 	struct rb_node *node;
1885 	int bitset = 0;
1886 
1887 	spin_lock(&tree->lock);
1888 	if (cached && extent_state_in_tree(cached) && cached->start <= start &&
1889 	    cached->end > start)
1890 		node = &cached->rb_node;
1891 	else
1892 		node = tree_search(tree, start);
1893 	while (node && start <= end) {
1894 		state = rb_entry(node, struct extent_state, rb_node);
1895 
1896 		if (filled && state->start > start) {
1897 			bitset = 0;
1898 			break;
1899 		}
1900 
1901 		if (state->start > end)
1902 			break;
1903 
1904 		if (state->state & bits) {
1905 			bitset = 1;
1906 			if (!filled)
1907 				break;
1908 		} else if (filled) {
1909 			bitset = 0;
1910 			break;
1911 		}
1912 
1913 		if (state->end == (u64)-1)
1914 			break;
1915 
1916 		start = state->end + 1;
1917 		if (start > end)
1918 			break;
1919 		node = rb_next(node);
1920 		if (!node) {
1921 			if (filled)
1922 				bitset = 0;
1923 			break;
1924 		}
1925 	}
1926 	spin_unlock(&tree->lock);
1927 	return bitset;
1928 }
1929 
1930 /*
1931  * helper function to set a given page up to date if all the
1932  * extents in the tree for that page are up to date
1933  */
1934 static void check_page_uptodate(struct extent_io_tree *tree, struct page *page)
1935 {
1936 	u64 start = page_offset(page);
1937 	u64 end = start + PAGE_SIZE - 1;
1938 	if (test_range_bit(tree, start, end, EXTENT_UPTODATE, 1, NULL))
1939 		SetPageUptodate(page);
1940 }
1941 
1942 int free_io_failure(struct extent_io_tree *failure_tree,
1943 		    struct extent_io_tree *io_tree,
1944 		    struct io_failure_record *rec)
1945 {
1946 	int ret;
1947 	int err = 0;
1948 
1949 	set_state_failrec(failure_tree, rec->start, NULL);
1950 	ret = clear_extent_bits(failure_tree, rec->start,
1951 				rec->start + rec->len - 1,
1952 				EXTENT_LOCKED | EXTENT_DIRTY);
1953 	if (ret)
1954 		err = ret;
1955 
1956 	ret = clear_extent_bits(io_tree, rec->start,
1957 				rec->start + rec->len - 1,
1958 				EXTENT_DAMAGED);
1959 	if (ret && !err)
1960 		err = ret;
1961 
1962 	kfree(rec);
1963 	return err;
1964 }
1965 
1966 /*
1967  * this bypasses the standard btrfs submit functions deliberately, as
1968  * the standard behavior is to write all copies in a raid setup. here we only
1969  * want to write the one bad copy. so we do the mapping for ourselves and issue
1970  * submit_bio directly.
1971  * to avoid any synchronization issues, wait for the data after writing, which
1972  * actually prevents the read that triggered the error from finishing.
1973  * currently, there can be no more than two copies of every data bit. thus,
1974  * exactly one rewrite is required.
1975  */
1976 int repair_io_failure(struct btrfs_fs_info *fs_info, u64 ino, u64 start,
1977 		      u64 length, u64 logical, struct page *page,
1978 		      unsigned int pg_offset, int mirror_num)
1979 {
1980 	struct bio *bio;
1981 	struct btrfs_device *dev;
1982 	u64 map_length = 0;
1983 	u64 sector;
1984 	struct btrfs_bio *bbio = NULL;
1985 	int ret;
1986 
1987 	ASSERT(!(fs_info->sb->s_flags & MS_RDONLY));
1988 	BUG_ON(!mirror_num);
1989 
1990 	bio = btrfs_io_bio_alloc(1);
1991 	bio->bi_iter.bi_size = 0;
1992 	map_length = length;
1993 
1994 	/*
1995 	 * Avoid races with device replace and make sure our bbio has devices
1996 	 * associated to its stripes that don't go away while we are doing the
1997 	 * read repair operation.
1998 	 */
1999 	btrfs_bio_counter_inc_blocked(fs_info);
2000 	if (btrfs_is_parity_mirror(fs_info, logical, length)) {
2001 		/*
2002 		 * Note that we don't use BTRFS_MAP_WRITE because it's supposed
2003 		 * to update all raid stripes, but here we just want to correct
2004 		 * bad stripe, thus BTRFS_MAP_READ is abused to only get the bad
2005 		 * stripe's dev and sector.
2006 		 */
2007 		ret = btrfs_map_block(fs_info, BTRFS_MAP_READ, logical,
2008 				      &map_length, &bbio, 0);
2009 		if (ret) {
2010 			btrfs_bio_counter_dec(fs_info);
2011 			bio_put(bio);
2012 			return -EIO;
2013 		}
2014 		ASSERT(bbio->mirror_num == 1);
2015 	} else {
2016 		ret = btrfs_map_block(fs_info, BTRFS_MAP_WRITE, logical,
2017 				      &map_length, &bbio, mirror_num);
2018 		if (ret) {
2019 			btrfs_bio_counter_dec(fs_info);
2020 			bio_put(bio);
2021 			return -EIO;
2022 		}
2023 		BUG_ON(mirror_num != bbio->mirror_num);
2024 	}
2025 
2026 	sector = bbio->stripes[bbio->mirror_num - 1].physical >> 9;
2027 	bio->bi_iter.bi_sector = sector;
2028 	dev = bbio->stripes[bbio->mirror_num - 1].dev;
2029 	btrfs_put_bbio(bbio);
2030 	if (!dev || !dev->bdev || !dev->writeable) {
2031 		btrfs_bio_counter_dec(fs_info);
2032 		bio_put(bio);
2033 		return -EIO;
2034 	}
2035 	bio_set_dev(bio, dev->bdev);
2036 	bio->bi_opf = REQ_OP_WRITE | REQ_SYNC;
2037 	bio_add_page(bio, page, length, pg_offset);
2038 
2039 	if (btrfsic_submit_bio_wait(bio)) {
2040 		/* try to remap that extent elsewhere? */
2041 		btrfs_bio_counter_dec(fs_info);
2042 		bio_put(bio);
2043 		btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_WRITE_ERRS);
2044 		return -EIO;
2045 	}
2046 
2047 	btrfs_info_rl_in_rcu(fs_info,
2048 		"read error corrected: ino %llu off %llu (dev %s sector %llu)",
2049 				  ino, start,
2050 				  rcu_str_deref(dev->name), sector);
2051 	btrfs_bio_counter_dec(fs_info);
2052 	bio_put(bio);
2053 	return 0;
2054 }
2055 
2056 int repair_eb_io_failure(struct btrfs_fs_info *fs_info,
2057 			 struct extent_buffer *eb, int mirror_num)
2058 {
2059 	u64 start = eb->start;
2060 	unsigned long i, num_pages = num_extent_pages(eb->start, eb->len);
2061 	int ret = 0;
2062 
2063 	if (sb_rdonly(fs_info->sb))
2064 		return -EROFS;
2065 
2066 	for (i = 0; i < num_pages; i++) {
2067 		struct page *p = eb->pages[i];
2068 
2069 		ret = repair_io_failure(fs_info, 0, start, PAGE_SIZE, start, p,
2070 					start - page_offset(p), mirror_num);
2071 		if (ret)
2072 			break;
2073 		start += PAGE_SIZE;
2074 	}
2075 
2076 	return ret;
2077 }
2078 
2079 /*
2080  * each time an IO finishes, we do a fast check in the IO failure tree
2081  * to see if we need to process or clean up an io_failure_record
2082  */
2083 int clean_io_failure(struct btrfs_fs_info *fs_info,
2084 		     struct extent_io_tree *failure_tree,
2085 		     struct extent_io_tree *io_tree, u64 start,
2086 		     struct page *page, u64 ino, unsigned int pg_offset)
2087 {
2088 	u64 private;
2089 	struct io_failure_record *failrec;
2090 	struct extent_state *state;
2091 	int num_copies;
2092 	int ret;
2093 
2094 	private = 0;
2095 	ret = count_range_bits(failure_tree, &private, (u64)-1, 1,
2096 			       EXTENT_DIRTY, 0);
2097 	if (!ret)
2098 		return 0;
2099 
2100 	ret = get_state_failrec(failure_tree, start, &failrec);
2101 	if (ret)
2102 		return 0;
2103 
2104 	BUG_ON(!failrec->this_mirror);
2105 
2106 	if (failrec->in_validation) {
2107 		/* there was no real error, just free the record */
2108 		btrfs_debug(fs_info,
2109 			"clean_io_failure: freeing dummy error at %llu",
2110 			failrec->start);
2111 		goto out;
2112 	}
2113 	if (sb_rdonly(fs_info->sb))
2114 		goto out;
2115 
2116 	spin_lock(&io_tree->lock);
2117 	state = find_first_extent_bit_state(io_tree,
2118 					    failrec->start,
2119 					    EXTENT_LOCKED);
2120 	spin_unlock(&io_tree->lock);
2121 
2122 	if (state && state->start <= failrec->start &&
2123 	    state->end >= failrec->start + failrec->len - 1) {
2124 		num_copies = btrfs_num_copies(fs_info, failrec->logical,
2125 					      failrec->len);
2126 		if (num_copies > 1)  {
2127 			repair_io_failure(fs_info, ino, start, failrec->len,
2128 					  failrec->logical, page, pg_offset,
2129 					  failrec->failed_mirror);
2130 		}
2131 	}
2132 
2133 out:
2134 	free_io_failure(failure_tree, io_tree, failrec);
2135 
2136 	return 0;
2137 }
2138 
2139 /*
2140  * Can be called when
2141  * - hold extent lock
2142  * - under ordered extent
2143  * - the inode is freeing
2144  */
2145 void btrfs_free_io_failure_record(struct btrfs_inode *inode, u64 start, u64 end)
2146 {
2147 	struct extent_io_tree *failure_tree = &inode->io_failure_tree;
2148 	struct io_failure_record *failrec;
2149 	struct extent_state *state, *next;
2150 
2151 	if (RB_EMPTY_ROOT(&failure_tree->state))
2152 		return;
2153 
2154 	spin_lock(&failure_tree->lock);
2155 	state = find_first_extent_bit_state(failure_tree, start, EXTENT_DIRTY);
2156 	while (state) {
2157 		if (state->start > end)
2158 			break;
2159 
2160 		ASSERT(state->end <= end);
2161 
2162 		next = next_state(state);
2163 
2164 		failrec = state->failrec;
2165 		free_extent_state(state);
2166 		kfree(failrec);
2167 
2168 		state = next;
2169 	}
2170 	spin_unlock(&failure_tree->lock);
2171 }
2172 
2173 int btrfs_get_io_failure_record(struct inode *inode, u64 start, u64 end,
2174 		struct io_failure_record **failrec_ret)
2175 {
2176 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
2177 	struct io_failure_record *failrec;
2178 	struct extent_map *em;
2179 	struct extent_io_tree *failure_tree = &BTRFS_I(inode)->io_failure_tree;
2180 	struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;
2181 	struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
2182 	int ret;
2183 	u64 logical;
2184 
2185 	ret = get_state_failrec(failure_tree, start, &failrec);
2186 	if (ret) {
2187 		failrec = kzalloc(sizeof(*failrec), GFP_NOFS);
2188 		if (!failrec)
2189 			return -ENOMEM;
2190 
2191 		failrec->start = start;
2192 		failrec->len = end - start + 1;
2193 		failrec->this_mirror = 0;
2194 		failrec->bio_flags = 0;
2195 		failrec->in_validation = 0;
2196 
2197 		read_lock(&em_tree->lock);
2198 		em = lookup_extent_mapping(em_tree, start, failrec->len);
2199 		if (!em) {
2200 			read_unlock(&em_tree->lock);
2201 			kfree(failrec);
2202 			return -EIO;
2203 		}
2204 
2205 		if (em->start > start || em->start + em->len <= start) {
2206 			free_extent_map(em);
2207 			em = NULL;
2208 		}
2209 		read_unlock(&em_tree->lock);
2210 		if (!em) {
2211 			kfree(failrec);
2212 			return -EIO;
2213 		}
2214 
2215 		logical = start - em->start;
2216 		logical = em->block_start + logical;
2217 		if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
2218 			logical = em->block_start;
2219 			failrec->bio_flags = EXTENT_BIO_COMPRESSED;
2220 			extent_set_compress_type(&failrec->bio_flags,
2221 						 em->compress_type);
2222 		}
2223 
2224 		btrfs_debug(fs_info,
2225 			"Get IO Failure Record: (new) logical=%llu, start=%llu, len=%llu",
2226 			logical, start, failrec->len);
2227 
2228 		failrec->logical = logical;
2229 		free_extent_map(em);
2230 
2231 		/* set the bits in the private failure tree */
2232 		ret = set_extent_bits(failure_tree, start, end,
2233 					EXTENT_LOCKED | EXTENT_DIRTY);
2234 		if (ret >= 0)
2235 			ret = set_state_failrec(failure_tree, start, failrec);
2236 		/* set the bits in the inode's tree */
2237 		if (ret >= 0)
2238 			ret = set_extent_bits(tree, start, end, EXTENT_DAMAGED);
2239 		if (ret < 0) {
2240 			kfree(failrec);
2241 			return ret;
2242 		}
2243 	} else {
2244 		btrfs_debug(fs_info,
2245 			"Get IO Failure Record: (found) logical=%llu, start=%llu, len=%llu, validation=%d",
2246 			failrec->logical, failrec->start, failrec->len,
2247 			failrec->in_validation);
2248 		/*
2249 		 * when data can be on disk more than twice, add to failrec here
2250 		 * (e.g. with a list for failed_mirror) to make
2251 		 * clean_io_failure() clean all those errors at once.
2252 		 */
2253 	}
2254 
2255 	*failrec_ret = failrec;
2256 
2257 	return 0;
2258 }
2259 
2260 bool btrfs_check_repairable(struct inode *inode, struct bio *failed_bio,
2261 			   struct io_failure_record *failrec, int failed_mirror)
2262 {
2263 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
2264 	int num_copies;
2265 
2266 	num_copies = btrfs_num_copies(fs_info, failrec->logical, failrec->len);
2267 	if (num_copies == 1) {
2268 		/*
2269 		 * we only have a single copy of the data, so don't bother with
2270 		 * all the retry and error correction code that follows. no
2271 		 * matter what the error is, it is very likely to persist.
2272 		 */
2273 		btrfs_debug(fs_info,
2274 			"Check Repairable: cannot repair, num_copies=%d, next_mirror %d, failed_mirror %d",
2275 			num_copies, failrec->this_mirror, failed_mirror);
2276 		return false;
2277 	}
2278 
2279 	/*
2280 	 * there are two premises:
2281 	 *	a) deliver good data to the caller
2282 	 *	b) correct the bad sectors on disk
2283 	 */
2284 	if (failed_bio->bi_vcnt > 1) {
2285 		/*
2286 		 * to fulfill b), we need to know the exact failing sectors, as
2287 		 * we don't want to rewrite any more than the failed ones. thus,
2288 		 * we need separate read requests for the failed bio
2289 		 *
2290 		 * if the following BUG_ON triggers, our validation request got
2291 		 * merged. we need separate requests for our algorithm to work.
2292 		 */
2293 		BUG_ON(failrec->in_validation);
2294 		failrec->in_validation = 1;
2295 		failrec->this_mirror = failed_mirror;
2296 	} else {
2297 		/*
2298 		 * we're ready to fulfill a) and b) alongside. get a good copy
2299 		 * of the failed sector and if we succeed, we have setup
2300 		 * everything for repair_io_failure to do the rest for us.
2301 		 */
2302 		if (failrec->in_validation) {
2303 			BUG_ON(failrec->this_mirror != failed_mirror);
2304 			failrec->in_validation = 0;
2305 			failrec->this_mirror = 0;
2306 		}
2307 		failrec->failed_mirror = failed_mirror;
2308 		failrec->this_mirror++;
2309 		if (failrec->this_mirror == failed_mirror)
2310 			failrec->this_mirror++;
2311 	}
2312 
2313 	if (failrec->this_mirror > num_copies) {
2314 		btrfs_debug(fs_info,
2315 			"Check Repairable: (fail) num_copies=%d, next_mirror %d, failed_mirror %d",
2316 			num_copies, failrec->this_mirror, failed_mirror);
2317 		return false;
2318 	}
2319 
2320 	return true;
2321 }
2322 
2323 
2324 struct bio *btrfs_create_repair_bio(struct inode *inode, struct bio *failed_bio,
2325 				    struct io_failure_record *failrec,
2326 				    struct page *page, int pg_offset, int icsum,
2327 				    bio_end_io_t *endio_func, void *data)
2328 {
2329 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
2330 	struct bio *bio;
2331 	struct btrfs_io_bio *btrfs_failed_bio;
2332 	struct btrfs_io_bio *btrfs_bio;
2333 
2334 	bio = btrfs_io_bio_alloc(1);
2335 	bio->bi_end_io = endio_func;
2336 	bio->bi_iter.bi_sector = failrec->logical >> 9;
2337 	bio_set_dev(bio, fs_info->fs_devices->latest_bdev);
2338 	bio->bi_iter.bi_size = 0;
2339 	bio->bi_private = data;
2340 
2341 	btrfs_failed_bio = btrfs_io_bio(failed_bio);
2342 	if (btrfs_failed_bio->csum) {
2343 		u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
2344 
2345 		btrfs_bio = btrfs_io_bio(bio);
2346 		btrfs_bio->csum = btrfs_bio->csum_inline;
2347 		icsum *= csum_size;
2348 		memcpy(btrfs_bio->csum, btrfs_failed_bio->csum + icsum,
2349 		       csum_size);
2350 	}
2351 
2352 	bio_add_page(bio, page, failrec->len, pg_offset);
2353 
2354 	return bio;
2355 }
2356 
2357 /*
2358  * this is a generic handler for readpage errors (default
2359  * readpage_io_failed_hook). if other copies exist, read those and write back
2360  * good data to the failed position. does not investigate in remapping the
2361  * failed extent elsewhere, hoping the device will be smart enough to do this as
2362  * needed
2363  */
2364 
2365 static int bio_readpage_error(struct bio *failed_bio, u64 phy_offset,
2366 			      struct page *page, u64 start, u64 end,
2367 			      int failed_mirror)
2368 {
2369 	struct io_failure_record *failrec;
2370 	struct inode *inode = page->mapping->host;
2371 	struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;
2372 	struct extent_io_tree *failure_tree = &BTRFS_I(inode)->io_failure_tree;
2373 	struct bio *bio;
2374 	int read_mode = 0;
2375 	blk_status_t status;
2376 	int ret;
2377 
2378 	BUG_ON(bio_op(failed_bio) == REQ_OP_WRITE);
2379 
2380 	ret = btrfs_get_io_failure_record(inode, start, end, &failrec);
2381 	if (ret)
2382 		return ret;
2383 
2384 	if (!btrfs_check_repairable(inode, failed_bio, failrec,
2385 				    failed_mirror)) {
2386 		free_io_failure(failure_tree, tree, failrec);
2387 		return -EIO;
2388 	}
2389 
2390 	if (failed_bio->bi_vcnt > 1)
2391 		read_mode |= REQ_FAILFAST_DEV;
2392 
2393 	phy_offset >>= inode->i_sb->s_blocksize_bits;
2394 	bio = btrfs_create_repair_bio(inode, failed_bio, failrec, page,
2395 				      start - page_offset(page),
2396 				      (int)phy_offset, failed_bio->bi_end_io,
2397 				      NULL);
2398 	bio_set_op_attrs(bio, REQ_OP_READ, read_mode);
2399 
2400 	btrfs_debug(btrfs_sb(inode->i_sb),
2401 		"Repair Read Error: submitting new read[%#x] to this_mirror=%d, in_validation=%d",
2402 		read_mode, failrec->this_mirror, failrec->in_validation);
2403 
2404 	status = tree->ops->submit_bio_hook(tree->private_data, bio, failrec->this_mirror,
2405 					 failrec->bio_flags, 0);
2406 	if (status) {
2407 		free_io_failure(failure_tree, tree, failrec);
2408 		bio_put(bio);
2409 		ret = blk_status_to_errno(status);
2410 	}
2411 
2412 	return ret;
2413 }
2414 
2415 /* lots and lots of room for performance fixes in the end_bio funcs */
2416 
2417 void end_extent_writepage(struct page *page, int err, u64 start, u64 end)
2418 {
2419 	int uptodate = (err == 0);
2420 	struct extent_io_tree *tree;
2421 	int ret = 0;
2422 
2423 	tree = &BTRFS_I(page->mapping->host)->io_tree;
2424 
2425 	if (tree->ops && tree->ops->writepage_end_io_hook)
2426 		tree->ops->writepage_end_io_hook(page, start, end, NULL,
2427 				uptodate);
2428 
2429 	if (!uptodate) {
2430 		ClearPageUptodate(page);
2431 		SetPageError(page);
2432 		ret = err < 0 ? err : -EIO;
2433 		mapping_set_error(page->mapping, ret);
2434 	}
2435 }
2436 
2437 /*
2438  * after a writepage IO is done, we need to:
2439  * clear the uptodate bits on error
2440  * clear the writeback bits in the extent tree for this IO
2441  * end_page_writeback if the page has no more pending IO
2442  *
2443  * Scheduling is not allowed, so the extent state tree is expected
2444  * to have one and only one object corresponding to this IO.
2445  */
2446 static void end_bio_extent_writepage(struct bio *bio)
2447 {
2448 	int error = blk_status_to_errno(bio->bi_status);
2449 	struct bio_vec *bvec;
2450 	u64 start;
2451 	u64 end;
2452 	int i;
2453 
2454 	ASSERT(!bio_flagged(bio, BIO_CLONED));
2455 	bio_for_each_segment_all(bvec, bio, i) {
2456 		struct page *page = bvec->bv_page;
2457 		struct inode *inode = page->mapping->host;
2458 		struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
2459 
2460 		/* We always issue full-page reads, but if some block
2461 		 * in a page fails to read, blk_update_request() will
2462 		 * advance bv_offset and adjust bv_len to compensate.
2463 		 * Print a warning for nonzero offsets, and an error
2464 		 * if they don't add up to a full page.  */
2465 		if (bvec->bv_offset || bvec->bv_len != PAGE_SIZE) {
2466 			if (bvec->bv_offset + bvec->bv_len != PAGE_SIZE)
2467 				btrfs_err(fs_info,
2468 				   "partial page write in btrfs with offset %u and length %u",
2469 					bvec->bv_offset, bvec->bv_len);
2470 			else
2471 				btrfs_info(fs_info,
2472 				   "incomplete page write in btrfs with offset %u and length %u",
2473 					bvec->bv_offset, bvec->bv_len);
2474 		}
2475 
2476 		start = page_offset(page);
2477 		end = start + bvec->bv_offset + bvec->bv_len - 1;
2478 
2479 		end_extent_writepage(page, error, start, end);
2480 		end_page_writeback(page);
2481 	}
2482 
2483 	bio_put(bio);
2484 }
2485 
2486 static void
2487 endio_readpage_release_extent(struct extent_io_tree *tree, u64 start, u64 len,
2488 			      int uptodate)
2489 {
2490 	struct extent_state *cached = NULL;
2491 	u64 end = start + len - 1;
2492 
2493 	if (uptodate && tree->track_uptodate)
2494 		set_extent_uptodate(tree, start, end, &cached, GFP_ATOMIC);
2495 	unlock_extent_cached(tree, start, end, &cached, GFP_ATOMIC);
2496 }
2497 
2498 /*
2499  * after a readpage IO is done, we need to:
2500  * clear the uptodate bits on error
2501  * set the uptodate bits if things worked
2502  * set the page up to date if all extents in the tree are uptodate
2503  * clear the lock bit in the extent tree
2504  * unlock the page if there are no other extents locked for it
2505  *
2506  * Scheduling is not allowed, so the extent state tree is expected
2507  * to have one and only one object corresponding to this IO.
2508  */
2509 static void end_bio_extent_readpage(struct bio *bio)
2510 {
2511 	struct bio_vec *bvec;
2512 	int uptodate = !bio->bi_status;
2513 	struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);
2514 	struct extent_io_tree *tree, *failure_tree;
2515 	u64 offset = 0;
2516 	u64 start;
2517 	u64 end;
2518 	u64 len;
2519 	u64 extent_start = 0;
2520 	u64 extent_len = 0;
2521 	int mirror;
2522 	int ret;
2523 	int i;
2524 
2525 	ASSERT(!bio_flagged(bio, BIO_CLONED));
2526 	bio_for_each_segment_all(bvec, bio, i) {
2527 		struct page *page = bvec->bv_page;
2528 		struct inode *inode = page->mapping->host;
2529 		struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
2530 
2531 		btrfs_debug(fs_info,
2532 			"end_bio_extent_readpage: bi_sector=%llu, err=%d, mirror=%u",
2533 			(u64)bio->bi_iter.bi_sector, bio->bi_status,
2534 			io_bio->mirror_num);
2535 		tree = &BTRFS_I(inode)->io_tree;
2536 		failure_tree = &BTRFS_I(inode)->io_failure_tree;
2537 
2538 		/* We always issue full-page reads, but if some block
2539 		 * in a page fails to read, blk_update_request() will
2540 		 * advance bv_offset and adjust bv_len to compensate.
2541 		 * Print a warning for nonzero offsets, and an error
2542 		 * if they don't add up to a full page.  */
2543 		if (bvec->bv_offset || bvec->bv_len != PAGE_SIZE) {
2544 			if (bvec->bv_offset + bvec->bv_len != PAGE_SIZE)
2545 				btrfs_err(fs_info,
2546 					"partial page read in btrfs with offset %u and length %u",
2547 					bvec->bv_offset, bvec->bv_len);
2548 			else
2549 				btrfs_info(fs_info,
2550 					"incomplete page read in btrfs with offset %u and length %u",
2551 					bvec->bv_offset, bvec->bv_len);
2552 		}
2553 
2554 		start = page_offset(page);
2555 		end = start + bvec->bv_offset + bvec->bv_len - 1;
2556 		len = bvec->bv_len;
2557 
2558 		mirror = io_bio->mirror_num;
2559 		if (likely(uptodate && tree->ops)) {
2560 			ret = tree->ops->readpage_end_io_hook(io_bio, offset,
2561 							      page, start, end,
2562 							      mirror);
2563 			if (ret)
2564 				uptodate = 0;
2565 			else
2566 				clean_io_failure(BTRFS_I(inode)->root->fs_info,
2567 						 failure_tree, tree, start,
2568 						 page,
2569 						 btrfs_ino(BTRFS_I(inode)), 0);
2570 		}
2571 
2572 		if (likely(uptodate))
2573 			goto readpage_ok;
2574 
2575 		if (tree->ops) {
2576 			ret = tree->ops->readpage_io_failed_hook(page, mirror);
2577 			if (ret == -EAGAIN) {
2578 				/*
2579 				 * Data inode's readpage_io_failed_hook() always
2580 				 * returns -EAGAIN.
2581 				 *
2582 				 * The generic bio_readpage_error handles errors
2583 				 * the following way: If possible, new read
2584 				 * requests are created and submitted and will
2585 				 * end up in end_bio_extent_readpage as well (if
2586 				 * we're lucky, not in the !uptodate case). In
2587 				 * that case it returns 0 and we just go on with
2588 				 * the next page in our bio. If it can't handle
2589 				 * the error it will return -EIO and we remain
2590 				 * responsible for that page.
2591 				 */
2592 				ret = bio_readpage_error(bio, offset, page,
2593 							 start, end, mirror);
2594 				if (ret == 0) {
2595 					uptodate = !bio->bi_status;
2596 					offset += len;
2597 					continue;
2598 				}
2599 			}
2600 
2601 			/*
2602 			 * metadata's readpage_io_failed_hook() always returns
2603 			 * -EIO and fixes nothing.  -EIO is also returned if
2604 			 * data inode error could not be fixed.
2605 			 */
2606 			ASSERT(ret == -EIO);
2607 		}
2608 readpage_ok:
2609 		if (likely(uptodate)) {
2610 			loff_t i_size = i_size_read(inode);
2611 			pgoff_t end_index = i_size >> PAGE_SHIFT;
2612 			unsigned off;
2613 
2614 			/* Zero out the end if this page straddles i_size */
2615 			off = i_size & (PAGE_SIZE-1);
2616 			if (page->index == end_index && off)
2617 				zero_user_segment(page, off, PAGE_SIZE);
2618 			SetPageUptodate(page);
2619 		} else {
2620 			ClearPageUptodate(page);
2621 			SetPageError(page);
2622 		}
2623 		unlock_page(page);
2624 		offset += len;
2625 
2626 		if (unlikely(!uptodate)) {
2627 			if (extent_len) {
2628 				endio_readpage_release_extent(tree,
2629 							      extent_start,
2630 							      extent_len, 1);
2631 				extent_start = 0;
2632 				extent_len = 0;
2633 			}
2634 			endio_readpage_release_extent(tree, start,
2635 						      end - start + 1, 0);
2636 		} else if (!extent_len) {
2637 			extent_start = start;
2638 			extent_len = end + 1 - start;
2639 		} else if (extent_start + extent_len == start) {
2640 			extent_len += end + 1 - start;
2641 		} else {
2642 			endio_readpage_release_extent(tree, extent_start,
2643 						      extent_len, uptodate);
2644 			extent_start = start;
2645 			extent_len = end + 1 - start;
2646 		}
2647 	}
2648 
2649 	if (extent_len)
2650 		endio_readpage_release_extent(tree, extent_start, extent_len,
2651 					      uptodate);
2652 	if (io_bio->end_io)
2653 		io_bio->end_io(io_bio, blk_status_to_errno(bio->bi_status));
2654 	bio_put(bio);
2655 }
2656 
2657 /*
2658  * Initialize the members up to but not including 'bio'. Use after allocating a
2659  * new bio by bio_alloc_bioset as it does not initialize the bytes outside of
2660  * 'bio' because use of __GFP_ZERO is not supported.
2661  */
2662 static inline void btrfs_io_bio_init(struct btrfs_io_bio *btrfs_bio)
2663 {
2664 	memset(btrfs_bio, 0, offsetof(struct btrfs_io_bio, bio));
2665 }
2666 
2667 /*
2668  * The following helpers allocate a bio. As it's backed by a bioset, it'll
2669  * never fail.  We're returning a bio right now but you can call btrfs_io_bio
2670  * for the appropriate container_of magic
2671  */
2672 struct bio *btrfs_bio_alloc(struct block_device *bdev, u64 first_byte)
2673 {
2674 	struct bio *bio;
2675 
2676 	bio = bio_alloc_bioset(GFP_NOFS, BIO_MAX_PAGES, btrfs_bioset);
2677 	bio_set_dev(bio, bdev);
2678 	bio->bi_iter.bi_sector = first_byte >> 9;
2679 	btrfs_io_bio_init(btrfs_io_bio(bio));
2680 	return bio;
2681 }
2682 
2683 struct bio *btrfs_bio_clone(struct bio *bio)
2684 {
2685 	struct btrfs_io_bio *btrfs_bio;
2686 	struct bio *new;
2687 
2688 	/* Bio allocation backed by a bioset does not fail */
2689 	new = bio_clone_fast(bio, GFP_NOFS, btrfs_bioset);
2690 	btrfs_bio = btrfs_io_bio(new);
2691 	btrfs_io_bio_init(btrfs_bio);
2692 	btrfs_bio->iter = bio->bi_iter;
2693 	return new;
2694 }
2695 
2696 struct bio *btrfs_io_bio_alloc(unsigned int nr_iovecs)
2697 {
2698 	struct bio *bio;
2699 
2700 	/* Bio allocation backed by a bioset does not fail */
2701 	bio = bio_alloc_bioset(GFP_NOFS, nr_iovecs, btrfs_bioset);
2702 	btrfs_io_bio_init(btrfs_io_bio(bio));
2703 	return bio;
2704 }
2705 
2706 struct bio *btrfs_bio_clone_partial(struct bio *orig, int offset, int size)
2707 {
2708 	struct bio *bio;
2709 	struct btrfs_io_bio *btrfs_bio;
2710 
2711 	/* this will never fail when it's backed by a bioset */
2712 	bio = bio_clone_fast(orig, GFP_NOFS, btrfs_bioset);
2713 	ASSERT(bio);
2714 
2715 	btrfs_bio = btrfs_io_bio(bio);
2716 	btrfs_io_bio_init(btrfs_bio);
2717 
2718 	bio_trim(bio, offset >> 9, size >> 9);
2719 	btrfs_bio->iter = bio->bi_iter;
2720 	return bio;
2721 }
2722 
2723 static int __must_check submit_one_bio(struct bio *bio, int mirror_num,
2724 				       unsigned long bio_flags)
2725 {
2726 	blk_status_t ret = 0;
2727 	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
2728 	struct page *page = bvec->bv_page;
2729 	struct extent_io_tree *tree = bio->bi_private;
2730 	u64 start;
2731 
2732 	start = page_offset(page) + bvec->bv_offset;
2733 
2734 	bio->bi_private = NULL;
2735 	bio_get(bio);
2736 
2737 	if (tree->ops)
2738 		ret = tree->ops->submit_bio_hook(tree->private_data, bio,
2739 					   mirror_num, bio_flags, start);
2740 	else
2741 		btrfsic_submit_bio(bio);
2742 
2743 	bio_put(bio);
2744 	return blk_status_to_errno(ret);
2745 }
2746 
2747 static int merge_bio(struct extent_io_tree *tree, struct page *page,
2748 		     unsigned long offset, size_t size, struct bio *bio,
2749 		     unsigned long bio_flags)
2750 {
2751 	int ret = 0;
2752 	if (tree->ops)
2753 		ret = tree->ops->merge_bio_hook(page, offset, size, bio,
2754 						bio_flags);
2755 	return ret;
2756 
2757 }
2758 
2759 /*
2760  * @opf:	bio REQ_OP_* and REQ_* flags as one value
2761  */
2762 static int submit_extent_page(unsigned int opf, struct extent_io_tree *tree,
2763 			      struct writeback_control *wbc,
2764 			      struct page *page, u64 offset,
2765 			      size_t size, unsigned long pg_offset,
2766 			      struct block_device *bdev,
2767 			      struct bio **bio_ret,
2768 			      bio_end_io_t end_io_func,
2769 			      int mirror_num,
2770 			      unsigned long prev_bio_flags,
2771 			      unsigned long bio_flags,
2772 			      bool force_bio_submit)
2773 {
2774 	int ret = 0;
2775 	struct bio *bio;
2776 	int contig = 0;
2777 	int old_compressed = prev_bio_flags & EXTENT_BIO_COMPRESSED;
2778 	size_t page_size = min_t(size_t, size, PAGE_SIZE);
2779 	sector_t sector = offset >> 9;
2780 
2781 	if (bio_ret && *bio_ret) {
2782 		bio = *bio_ret;
2783 		if (old_compressed)
2784 			contig = bio->bi_iter.bi_sector == sector;
2785 		else
2786 			contig = bio_end_sector(bio) == sector;
2787 
2788 		if (prev_bio_flags != bio_flags || !contig ||
2789 		    force_bio_submit ||
2790 		    merge_bio(tree, page, pg_offset, page_size, bio, bio_flags) ||
2791 		    bio_add_page(bio, page, page_size, pg_offset) < page_size) {
2792 			ret = submit_one_bio(bio, mirror_num, prev_bio_flags);
2793 			if (ret < 0) {
2794 				*bio_ret = NULL;
2795 				return ret;
2796 			}
2797 			bio = NULL;
2798 		} else {
2799 			if (wbc)
2800 				wbc_account_io(wbc, page, page_size);
2801 			return 0;
2802 		}
2803 	}
2804 
2805 	bio = btrfs_bio_alloc(bdev, offset);
2806 	bio_add_page(bio, page, page_size, pg_offset);
2807 	bio->bi_end_io = end_io_func;
2808 	bio->bi_private = tree;
2809 	bio->bi_write_hint = page->mapping->host->i_write_hint;
2810 	bio->bi_opf = opf;
2811 	if (wbc) {
2812 		wbc_init_bio(wbc, bio);
2813 		wbc_account_io(wbc, page, page_size);
2814 	}
2815 
2816 	if (bio_ret)
2817 		*bio_ret = bio;
2818 	else
2819 		ret = submit_one_bio(bio, mirror_num, bio_flags);
2820 
2821 	return ret;
2822 }
2823 
2824 static void attach_extent_buffer_page(struct extent_buffer *eb,
2825 				      struct page *page)
2826 {
2827 	if (!PagePrivate(page)) {
2828 		SetPagePrivate(page);
2829 		get_page(page);
2830 		set_page_private(page, (unsigned long)eb);
2831 	} else {
2832 		WARN_ON(page->private != (unsigned long)eb);
2833 	}
2834 }
2835 
2836 void set_page_extent_mapped(struct page *page)
2837 {
2838 	if (!PagePrivate(page)) {
2839 		SetPagePrivate(page);
2840 		get_page(page);
2841 		set_page_private(page, EXTENT_PAGE_PRIVATE);
2842 	}
2843 }
2844 
2845 static struct extent_map *
2846 __get_extent_map(struct inode *inode, struct page *page, size_t pg_offset,
2847 		 u64 start, u64 len, get_extent_t *get_extent,
2848 		 struct extent_map **em_cached)
2849 {
2850 	struct extent_map *em;
2851 
2852 	if (em_cached && *em_cached) {
2853 		em = *em_cached;
2854 		if (extent_map_in_tree(em) && start >= em->start &&
2855 		    start < extent_map_end(em)) {
2856 			refcount_inc(&em->refs);
2857 			return em;
2858 		}
2859 
2860 		free_extent_map(em);
2861 		*em_cached = NULL;
2862 	}
2863 
2864 	em = get_extent(BTRFS_I(inode), page, pg_offset, start, len, 0);
2865 	if (em_cached && !IS_ERR_OR_NULL(em)) {
2866 		BUG_ON(*em_cached);
2867 		refcount_inc(&em->refs);
2868 		*em_cached = em;
2869 	}
2870 	return em;
2871 }
2872 /*
2873  * basic readpage implementation.  Locked extent state structs are inserted
2874  * into the tree that are removed when the IO is done (by the end_io
2875  * handlers)
2876  * XXX JDM: This needs looking at to ensure proper page locking
2877  * return 0 on success, otherwise return error
2878  */
2879 static int __do_readpage(struct extent_io_tree *tree,
2880 			 struct page *page,
2881 			 get_extent_t *get_extent,
2882 			 struct extent_map **em_cached,
2883 			 struct bio **bio, int mirror_num,
2884 			 unsigned long *bio_flags, unsigned int read_flags,
2885 			 u64 *prev_em_start)
2886 {
2887 	struct inode *inode = page->mapping->host;
2888 	u64 start = page_offset(page);
2889 	u64 page_end = start + PAGE_SIZE - 1;
2890 	u64 end;
2891 	u64 cur = start;
2892 	u64 extent_offset;
2893 	u64 last_byte = i_size_read(inode);
2894 	u64 block_start;
2895 	u64 cur_end;
2896 	struct extent_map *em;
2897 	struct block_device *bdev;
2898 	int ret = 0;
2899 	int nr = 0;
2900 	size_t pg_offset = 0;
2901 	size_t iosize;
2902 	size_t disk_io_size;
2903 	size_t blocksize = inode->i_sb->s_blocksize;
2904 	unsigned long this_bio_flag = 0;
2905 
2906 	set_page_extent_mapped(page);
2907 
2908 	end = page_end;
2909 	if (!PageUptodate(page)) {
2910 		if (cleancache_get_page(page) == 0) {
2911 			BUG_ON(blocksize != PAGE_SIZE);
2912 			unlock_extent(tree, start, end);
2913 			goto out;
2914 		}
2915 	}
2916 
2917 	if (page->index == last_byte >> PAGE_SHIFT) {
2918 		char *userpage;
2919 		size_t zero_offset = last_byte & (PAGE_SIZE - 1);
2920 
2921 		if (zero_offset) {
2922 			iosize = PAGE_SIZE - zero_offset;
2923 			userpage = kmap_atomic(page);
2924 			memset(userpage + zero_offset, 0, iosize);
2925 			flush_dcache_page(page);
2926 			kunmap_atomic(userpage);
2927 		}
2928 	}
2929 	while (cur <= end) {
2930 		bool force_bio_submit = false;
2931 		u64 offset;
2932 
2933 		if (cur >= last_byte) {
2934 			char *userpage;
2935 			struct extent_state *cached = NULL;
2936 
2937 			iosize = PAGE_SIZE - pg_offset;
2938 			userpage = kmap_atomic(page);
2939 			memset(userpage + pg_offset, 0, iosize);
2940 			flush_dcache_page(page);
2941 			kunmap_atomic(userpage);
2942 			set_extent_uptodate(tree, cur, cur + iosize - 1,
2943 					    &cached, GFP_NOFS);
2944 			unlock_extent_cached(tree, cur,
2945 					     cur + iosize - 1,
2946 					     &cached, GFP_NOFS);
2947 			break;
2948 		}
2949 		em = __get_extent_map(inode, page, pg_offset, cur,
2950 				      end - cur + 1, get_extent, em_cached);
2951 		if (IS_ERR_OR_NULL(em)) {
2952 			SetPageError(page);
2953 			unlock_extent(tree, cur, end);
2954 			break;
2955 		}
2956 		extent_offset = cur - em->start;
2957 		BUG_ON(extent_map_end(em) <= cur);
2958 		BUG_ON(end < cur);
2959 
2960 		if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
2961 			this_bio_flag |= EXTENT_BIO_COMPRESSED;
2962 			extent_set_compress_type(&this_bio_flag,
2963 						 em->compress_type);
2964 		}
2965 
2966 		iosize = min(extent_map_end(em) - cur, end - cur + 1);
2967 		cur_end = min(extent_map_end(em) - 1, end);
2968 		iosize = ALIGN(iosize, blocksize);
2969 		if (this_bio_flag & EXTENT_BIO_COMPRESSED) {
2970 			disk_io_size = em->block_len;
2971 			offset = em->block_start;
2972 		} else {
2973 			offset = em->block_start + extent_offset;
2974 			disk_io_size = iosize;
2975 		}
2976 		bdev = em->bdev;
2977 		block_start = em->block_start;
2978 		if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
2979 			block_start = EXTENT_MAP_HOLE;
2980 
2981 		/*
2982 		 * If we have a file range that points to a compressed extent
2983 		 * and it's followed by a consecutive file range that points to
2984 		 * to the same compressed extent (possibly with a different
2985 		 * offset and/or length, so it either points to the whole extent
2986 		 * or only part of it), we must make sure we do not submit a
2987 		 * single bio to populate the pages for the 2 ranges because
2988 		 * this makes the compressed extent read zero out the pages
2989 		 * belonging to the 2nd range. Imagine the following scenario:
2990 		 *
2991 		 *  File layout
2992 		 *  [0 - 8K]                     [8K - 24K]
2993 		 *    |                               |
2994 		 *    |                               |
2995 		 * points to extent X,         points to extent X,
2996 		 * offset 4K, length of 8K     offset 0, length 16K
2997 		 *
2998 		 * [extent X, compressed length = 4K uncompressed length = 16K]
2999 		 *
3000 		 * If the bio to read the compressed extent covers both ranges,
3001 		 * it will decompress extent X into the pages belonging to the
3002 		 * first range and then it will stop, zeroing out the remaining
3003 		 * pages that belong to the other range that points to extent X.
3004 		 * So here we make sure we submit 2 bios, one for the first
3005 		 * range and another one for the third range. Both will target
3006 		 * the same physical extent from disk, but we can't currently
3007 		 * make the compressed bio endio callback populate the pages
3008 		 * for both ranges because each compressed bio is tightly
3009 		 * coupled with a single extent map, and each range can have
3010 		 * an extent map with a different offset value relative to the
3011 		 * uncompressed data of our extent and different lengths. This
3012 		 * is a corner case so we prioritize correctness over
3013 		 * non-optimal behavior (submitting 2 bios for the same extent).
3014 		 */
3015 		if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags) &&
3016 		    prev_em_start && *prev_em_start != (u64)-1 &&
3017 		    *prev_em_start != em->orig_start)
3018 			force_bio_submit = true;
3019 
3020 		if (prev_em_start)
3021 			*prev_em_start = em->orig_start;
3022 
3023 		free_extent_map(em);
3024 		em = NULL;
3025 
3026 		/* we've found a hole, just zero and go on */
3027 		if (block_start == EXTENT_MAP_HOLE) {
3028 			char *userpage;
3029 			struct extent_state *cached = NULL;
3030 
3031 			userpage = kmap_atomic(page);
3032 			memset(userpage + pg_offset, 0, iosize);
3033 			flush_dcache_page(page);
3034 			kunmap_atomic(userpage);
3035 
3036 			set_extent_uptodate(tree, cur, cur + iosize - 1,
3037 					    &cached, GFP_NOFS);
3038 			unlock_extent_cached(tree, cur,
3039 					     cur + iosize - 1,
3040 					     &cached, GFP_NOFS);
3041 			cur = cur + iosize;
3042 			pg_offset += iosize;
3043 			continue;
3044 		}
3045 		/* the get_extent function already copied into the page */
3046 		if (test_range_bit(tree, cur, cur_end,
3047 				   EXTENT_UPTODATE, 1, NULL)) {
3048 			check_page_uptodate(tree, page);
3049 			unlock_extent(tree, cur, cur + iosize - 1);
3050 			cur = cur + iosize;
3051 			pg_offset += iosize;
3052 			continue;
3053 		}
3054 		/* we have an inline extent but it didn't get marked up
3055 		 * to date.  Error out
3056 		 */
3057 		if (block_start == EXTENT_MAP_INLINE) {
3058 			SetPageError(page);
3059 			unlock_extent(tree, cur, cur + iosize - 1);
3060 			cur = cur + iosize;
3061 			pg_offset += iosize;
3062 			continue;
3063 		}
3064 
3065 		ret = submit_extent_page(REQ_OP_READ | read_flags, tree, NULL,
3066 					 page, offset, disk_io_size,
3067 					 pg_offset, bdev, bio,
3068 					 end_bio_extent_readpage, mirror_num,
3069 					 *bio_flags,
3070 					 this_bio_flag,
3071 					 force_bio_submit);
3072 		if (!ret) {
3073 			nr++;
3074 			*bio_flags = this_bio_flag;
3075 		} else {
3076 			SetPageError(page);
3077 			unlock_extent(tree, cur, cur + iosize - 1);
3078 			goto out;
3079 		}
3080 		cur = cur + iosize;
3081 		pg_offset += iosize;
3082 	}
3083 out:
3084 	if (!nr) {
3085 		if (!PageError(page))
3086 			SetPageUptodate(page);
3087 		unlock_page(page);
3088 	}
3089 	return ret;
3090 }
3091 
3092 static inline void __do_contiguous_readpages(struct extent_io_tree *tree,
3093 					     struct page *pages[], int nr_pages,
3094 					     u64 start, u64 end,
3095 					     get_extent_t *get_extent,
3096 					     struct extent_map **em_cached,
3097 					     struct bio **bio, int mirror_num,
3098 					     unsigned long *bio_flags,
3099 					     u64 *prev_em_start)
3100 {
3101 	struct inode *inode;
3102 	struct btrfs_ordered_extent *ordered;
3103 	int index;
3104 
3105 	inode = pages[0]->mapping->host;
3106 	while (1) {
3107 		lock_extent(tree, start, end);
3108 		ordered = btrfs_lookup_ordered_range(BTRFS_I(inode), start,
3109 						     end - start + 1);
3110 		if (!ordered)
3111 			break;
3112 		unlock_extent(tree, start, end);
3113 		btrfs_start_ordered_extent(inode, ordered, 1);
3114 		btrfs_put_ordered_extent(ordered);
3115 	}
3116 
3117 	for (index = 0; index < nr_pages; index++) {
3118 		__do_readpage(tree, pages[index], get_extent, em_cached, bio,
3119 			      mirror_num, bio_flags, 0, prev_em_start);
3120 		put_page(pages[index]);
3121 	}
3122 }
3123 
3124 static void __extent_readpages(struct extent_io_tree *tree,
3125 			       struct page *pages[],
3126 			       int nr_pages, get_extent_t *get_extent,
3127 			       struct extent_map **em_cached,
3128 			       struct bio **bio, int mirror_num,
3129 			       unsigned long *bio_flags,
3130 			       u64 *prev_em_start)
3131 {
3132 	u64 start = 0;
3133 	u64 end = 0;
3134 	u64 page_start;
3135 	int index;
3136 	int first_index = 0;
3137 
3138 	for (index = 0; index < nr_pages; index++) {
3139 		page_start = page_offset(pages[index]);
3140 		if (!end) {
3141 			start = page_start;
3142 			end = start + PAGE_SIZE - 1;
3143 			first_index = index;
3144 		} else if (end + 1 == page_start) {
3145 			end += PAGE_SIZE;
3146 		} else {
3147 			__do_contiguous_readpages(tree, &pages[first_index],
3148 						  index - first_index, start,
3149 						  end, get_extent, em_cached,
3150 						  bio, mirror_num, bio_flags,
3151 						  prev_em_start);
3152 			start = page_start;
3153 			end = start + PAGE_SIZE - 1;
3154 			first_index = index;
3155 		}
3156 	}
3157 
3158 	if (end)
3159 		__do_contiguous_readpages(tree, &pages[first_index],
3160 					  index - first_index, start,
3161 					  end, get_extent, em_cached, bio,
3162 					  mirror_num, bio_flags,
3163 					  prev_em_start);
3164 }
3165 
3166 static int __extent_read_full_page(struct extent_io_tree *tree,
3167 				   struct page *page,
3168 				   get_extent_t *get_extent,
3169 				   struct bio **bio, int mirror_num,
3170 				   unsigned long *bio_flags,
3171 				   unsigned int read_flags)
3172 {
3173 	struct inode *inode = page->mapping->host;
3174 	struct btrfs_ordered_extent *ordered;
3175 	u64 start = page_offset(page);
3176 	u64 end = start + PAGE_SIZE - 1;
3177 	int ret;
3178 
3179 	while (1) {
3180 		lock_extent(tree, start, end);
3181 		ordered = btrfs_lookup_ordered_range(BTRFS_I(inode), start,
3182 						PAGE_SIZE);
3183 		if (!ordered)
3184 			break;
3185 		unlock_extent(tree, start, end);
3186 		btrfs_start_ordered_extent(inode, ordered, 1);
3187 		btrfs_put_ordered_extent(ordered);
3188 	}
3189 
3190 	ret = __do_readpage(tree, page, get_extent, NULL, bio, mirror_num,
3191 			    bio_flags, read_flags, NULL);
3192 	return ret;
3193 }
3194 
3195 int extent_read_full_page(struct extent_io_tree *tree, struct page *page,
3196 			    get_extent_t *get_extent, int mirror_num)
3197 {
3198 	struct bio *bio = NULL;
3199 	unsigned long bio_flags = 0;
3200 	int ret;
3201 
3202 	ret = __extent_read_full_page(tree, page, get_extent, &bio, mirror_num,
3203 				      &bio_flags, 0);
3204 	if (bio)
3205 		ret = submit_one_bio(bio, mirror_num, bio_flags);
3206 	return ret;
3207 }
3208 
3209 static void update_nr_written(struct writeback_control *wbc,
3210 			      unsigned long nr_written)
3211 {
3212 	wbc->nr_to_write -= nr_written;
3213 }
3214 
3215 /*
3216  * helper for __extent_writepage, doing all of the delayed allocation setup.
3217  *
3218  * This returns 1 if our fill_delalloc function did all the work required
3219  * to write the page (copy into inline extent).  In this case the IO has
3220  * been started and the page is already unlocked.
3221  *
3222  * This returns 0 if all went well (page still locked)
3223  * This returns < 0 if there were errors (page still locked)
3224  */
3225 static noinline_for_stack int writepage_delalloc(struct inode *inode,
3226 			      struct page *page, struct writeback_control *wbc,
3227 			      struct extent_page_data *epd,
3228 			      u64 delalloc_start,
3229 			      unsigned long *nr_written)
3230 {
3231 	struct extent_io_tree *tree = epd->tree;
3232 	u64 page_end = delalloc_start + PAGE_SIZE - 1;
3233 	u64 nr_delalloc;
3234 	u64 delalloc_to_write = 0;
3235 	u64 delalloc_end = 0;
3236 	int ret;
3237 	int page_started = 0;
3238 
3239 	if (epd->extent_locked || !tree->ops || !tree->ops->fill_delalloc)
3240 		return 0;
3241 
3242 	while (delalloc_end < page_end) {
3243 		nr_delalloc = find_lock_delalloc_range(inode, tree,
3244 					       page,
3245 					       &delalloc_start,
3246 					       &delalloc_end,
3247 					       BTRFS_MAX_EXTENT_SIZE);
3248 		if (nr_delalloc == 0) {
3249 			delalloc_start = delalloc_end + 1;
3250 			continue;
3251 		}
3252 		ret = tree->ops->fill_delalloc(inode, page,
3253 					       delalloc_start,
3254 					       delalloc_end,
3255 					       &page_started,
3256 					       nr_written);
3257 		/* File system has been set read-only */
3258 		if (ret) {
3259 			SetPageError(page);
3260 			/* fill_delalloc should be return < 0 for error
3261 			 * but just in case, we use > 0 here meaning the
3262 			 * IO is started, so we don't want to return > 0
3263 			 * unless things are going well.
3264 			 */
3265 			ret = ret < 0 ? ret : -EIO;
3266 			goto done;
3267 		}
3268 		/*
3269 		 * delalloc_end is already one less than the total length, so
3270 		 * we don't subtract one from PAGE_SIZE
3271 		 */
3272 		delalloc_to_write += (delalloc_end - delalloc_start +
3273 				      PAGE_SIZE) >> PAGE_SHIFT;
3274 		delalloc_start = delalloc_end + 1;
3275 	}
3276 	if (wbc->nr_to_write < delalloc_to_write) {
3277 		int thresh = 8192;
3278 
3279 		if (delalloc_to_write < thresh * 2)
3280 			thresh = delalloc_to_write;
3281 		wbc->nr_to_write = min_t(u64, delalloc_to_write,
3282 					 thresh);
3283 	}
3284 
3285 	/* did the fill delalloc function already unlock and start
3286 	 * the IO?
3287 	 */
3288 	if (page_started) {
3289 		/*
3290 		 * we've unlocked the page, so we can't update
3291 		 * the mapping's writeback index, just update
3292 		 * nr_to_write.
3293 		 */
3294 		wbc->nr_to_write -= *nr_written;
3295 		return 1;
3296 	}
3297 
3298 	ret = 0;
3299 
3300 done:
3301 	return ret;
3302 }
3303 
3304 /*
3305  * helper for __extent_writepage.  This calls the writepage start hooks,
3306  * and does the loop to map the page into extents and bios.
3307  *
3308  * We return 1 if the IO is started and the page is unlocked,
3309  * 0 if all went well (page still locked)
3310  * < 0 if there were errors (page still locked)
3311  */
3312 static noinline_for_stack int __extent_writepage_io(struct inode *inode,
3313 				 struct page *page,
3314 				 struct writeback_control *wbc,
3315 				 struct extent_page_data *epd,
3316 				 loff_t i_size,
3317 				 unsigned long nr_written,
3318 				 unsigned int write_flags, int *nr_ret)
3319 {
3320 	struct extent_io_tree *tree = epd->tree;
3321 	u64 start = page_offset(page);
3322 	u64 page_end = start + PAGE_SIZE - 1;
3323 	u64 end;
3324 	u64 cur = start;
3325 	u64 extent_offset;
3326 	u64 block_start;
3327 	u64 iosize;
3328 	struct extent_map *em;
3329 	struct block_device *bdev;
3330 	size_t pg_offset = 0;
3331 	size_t blocksize;
3332 	int ret = 0;
3333 	int nr = 0;
3334 	bool compressed;
3335 
3336 	if (tree->ops && tree->ops->writepage_start_hook) {
3337 		ret = tree->ops->writepage_start_hook(page, start,
3338 						      page_end);
3339 		if (ret) {
3340 			/* Fixup worker will requeue */
3341 			if (ret == -EBUSY)
3342 				wbc->pages_skipped++;
3343 			else
3344 				redirty_page_for_writepage(wbc, page);
3345 
3346 			update_nr_written(wbc, nr_written);
3347 			unlock_page(page);
3348 			return 1;
3349 		}
3350 	}
3351 
3352 	/*
3353 	 * we don't want to touch the inode after unlocking the page,
3354 	 * so we update the mapping writeback index now
3355 	 */
3356 	update_nr_written(wbc, nr_written + 1);
3357 
3358 	end = page_end;
3359 	if (i_size <= start) {
3360 		if (tree->ops && tree->ops->writepage_end_io_hook)
3361 			tree->ops->writepage_end_io_hook(page, start,
3362 							 page_end, NULL, 1);
3363 		goto done;
3364 	}
3365 
3366 	blocksize = inode->i_sb->s_blocksize;
3367 
3368 	while (cur <= end) {
3369 		u64 em_end;
3370 		u64 offset;
3371 
3372 		if (cur >= i_size) {
3373 			if (tree->ops && tree->ops->writepage_end_io_hook)
3374 				tree->ops->writepage_end_io_hook(page, cur,
3375 							 page_end, NULL, 1);
3376 			break;
3377 		}
3378 		em = epd->get_extent(BTRFS_I(inode), page, pg_offset, cur,
3379 				     end - cur + 1, 1);
3380 		if (IS_ERR_OR_NULL(em)) {
3381 			SetPageError(page);
3382 			ret = PTR_ERR_OR_ZERO(em);
3383 			break;
3384 		}
3385 
3386 		extent_offset = cur - em->start;
3387 		em_end = extent_map_end(em);
3388 		BUG_ON(em_end <= cur);
3389 		BUG_ON(end < cur);
3390 		iosize = min(em_end - cur, end - cur + 1);
3391 		iosize = ALIGN(iosize, blocksize);
3392 		offset = em->block_start + extent_offset;
3393 		bdev = em->bdev;
3394 		block_start = em->block_start;
3395 		compressed = test_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
3396 		free_extent_map(em);
3397 		em = NULL;
3398 
3399 		/*
3400 		 * compressed and inline extents are written through other
3401 		 * paths in the FS
3402 		 */
3403 		if (compressed || block_start == EXTENT_MAP_HOLE ||
3404 		    block_start == EXTENT_MAP_INLINE) {
3405 			/*
3406 			 * end_io notification does not happen here for
3407 			 * compressed extents
3408 			 */
3409 			if (!compressed && tree->ops &&
3410 			    tree->ops->writepage_end_io_hook)
3411 				tree->ops->writepage_end_io_hook(page, cur,
3412 							 cur + iosize - 1,
3413 							 NULL, 1);
3414 			else if (compressed) {
3415 				/* we don't want to end_page_writeback on
3416 				 * a compressed extent.  this happens
3417 				 * elsewhere
3418 				 */
3419 				nr++;
3420 			}
3421 
3422 			cur += iosize;
3423 			pg_offset += iosize;
3424 			continue;
3425 		}
3426 
3427 		set_range_writeback(tree, cur, cur + iosize - 1);
3428 		if (!PageWriteback(page)) {
3429 			btrfs_err(BTRFS_I(inode)->root->fs_info,
3430 				   "page %lu not writeback, cur %llu end %llu",
3431 			       page->index, cur, end);
3432 		}
3433 
3434 		ret = submit_extent_page(REQ_OP_WRITE | write_flags, tree, wbc,
3435 					 page, offset, iosize, pg_offset,
3436 					 bdev, &epd->bio,
3437 					 end_bio_extent_writepage,
3438 					 0, 0, 0, false);
3439 		if (ret) {
3440 			SetPageError(page);
3441 			if (PageWriteback(page))
3442 				end_page_writeback(page);
3443 		}
3444 
3445 		cur = cur + iosize;
3446 		pg_offset += iosize;
3447 		nr++;
3448 	}
3449 done:
3450 	*nr_ret = nr;
3451 	return ret;
3452 }
3453 
3454 /*
3455  * the writepage semantics are similar to regular writepage.  extent
3456  * records are inserted to lock ranges in the tree, and as dirty areas
3457  * are found, they are marked writeback.  Then the lock bits are removed
3458  * and the end_io handler clears the writeback ranges
3459  */
3460 static int __extent_writepage(struct page *page, struct writeback_control *wbc,
3461 			      void *data)
3462 {
3463 	struct inode *inode = page->mapping->host;
3464 	struct extent_page_data *epd = data;
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  * @writepage: function called for each page
3899  * @data: data passed to writepage function
3900  *
3901  * If a page is already under I/O, write_cache_pages() skips it, even
3902  * if it's dirty.  This is desirable behaviour for memory-cleaning writeback,
3903  * but it is INCORRECT for data-integrity system calls such as fsync().  fsync()
3904  * and msync() need to guarantee that all the data which was dirty at the time
3905  * the call was made get new I/O started against them.  If wbc->sync_mode is
3906  * WB_SYNC_ALL then we were called for data integrity and we must wait for
3907  * existing IO to complete.
3908  */
3909 static int extent_write_cache_pages(struct address_space *mapping,
3910 			     struct writeback_control *wbc,
3911 			     writepage_t writepage, void *data,
3912 			     void (*flush_fn)(void *))
3913 {
3914 	struct inode *inode = mapping->host;
3915 	int ret = 0;
3916 	int done = 0;
3917 	int nr_to_write_done = 0;
3918 	struct pagevec pvec;
3919 	int nr_pages;
3920 	pgoff_t index;
3921 	pgoff_t end;		/* Inclusive */
3922 	pgoff_t done_index;
3923 	int range_whole = 0;
3924 	int scanned = 0;
3925 	int tag;
3926 
3927 	/*
3928 	 * We have to hold onto the inode so that ordered extents can do their
3929 	 * work when the IO finishes.  The alternative to this is failing to add
3930 	 * an ordered extent if the igrab() fails there and that is a huge pain
3931 	 * to deal with, so instead just hold onto the inode throughout the
3932 	 * writepages operation.  If it fails here we are freeing up the inode
3933 	 * anyway and we'd rather not waste our time writing out stuff that is
3934 	 * going to be truncated anyway.
3935 	 */
3936 	if (!igrab(inode))
3937 		return 0;
3938 
3939 	pagevec_init(&pvec);
3940 	if (wbc->range_cyclic) {
3941 		index = mapping->writeback_index; /* Start from prev offset */
3942 		end = -1;
3943 	} else {
3944 		index = wbc->range_start >> PAGE_SHIFT;
3945 		end = wbc->range_end >> PAGE_SHIFT;
3946 		if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
3947 			range_whole = 1;
3948 		scanned = 1;
3949 	}
3950 	if (wbc->sync_mode == WB_SYNC_ALL)
3951 		tag = PAGECACHE_TAG_TOWRITE;
3952 	else
3953 		tag = PAGECACHE_TAG_DIRTY;
3954 retry:
3955 	if (wbc->sync_mode == WB_SYNC_ALL)
3956 		tag_pages_for_writeback(mapping, index, end);
3957 	done_index = index;
3958 	while (!done && !nr_to_write_done && (index <= end) &&
3959 			(nr_pages = pagevec_lookup_range_tag(&pvec, mapping,
3960 						&index, end, tag))) {
3961 		unsigned i;
3962 
3963 		scanned = 1;
3964 		for (i = 0; i < nr_pages; i++) {
3965 			struct page *page = pvec.pages[i];
3966 
3967 			done_index = page->index;
3968 			/*
3969 			 * At this point we hold neither mapping->tree_lock nor
3970 			 * lock on the page itself: the page may be truncated or
3971 			 * invalidated (changing page->mapping to NULL), or even
3972 			 * swizzled back from swapper_space to tmpfs file
3973 			 * mapping
3974 			 */
3975 			if (!trylock_page(page)) {
3976 				flush_fn(data);
3977 				lock_page(page);
3978 			}
3979 
3980 			if (unlikely(page->mapping != mapping)) {
3981 				unlock_page(page);
3982 				continue;
3983 			}
3984 
3985 			if (wbc->sync_mode != WB_SYNC_NONE) {
3986 				if (PageWriteback(page))
3987 					flush_fn(data);
3988 				wait_on_page_writeback(page);
3989 			}
3990 
3991 			if (PageWriteback(page) ||
3992 			    !clear_page_dirty_for_io(page)) {
3993 				unlock_page(page);
3994 				continue;
3995 			}
3996 
3997 			ret = (*writepage)(page, wbc, data);
3998 
3999 			if (unlikely(ret == AOP_WRITEPAGE_ACTIVATE)) {
4000 				unlock_page(page);
4001 				ret = 0;
4002 			}
4003 			if (ret < 0) {
4004 				/*
4005 				 * done_index is set past this page,
4006 				 * so media errors will not choke
4007 				 * background writeout for the entire
4008 				 * file. This has consequences for
4009 				 * range_cyclic semantics (ie. it may
4010 				 * not be suitable for data integrity
4011 				 * writeout).
4012 				 */
4013 				done_index = page->index + 1;
4014 				done = 1;
4015 				break;
4016 			}
4017 
4018 			/*
4019 			 * the filesystem may choose to bump up nr_to_write.
4020 			 * We have to make sure to honor the new nr_to_write
4021 			 * at any time
4022 			 */
4023 			nr_to_write_done = wbc->nr_to_write <= 0;
4024 		}
4025 		pagevec_release(&pvec);
4026 		cond_resched();
4027 	}
4028 	if (!scanned && !done) {
4029 		/*
4030 		 * We hit the last page and there is more work to be done: wrap
4031 		 * back to the start of the file
4032 		 */
4033 		scanned = 1;
4034 		index = 0;
4035 		goto retry;
4036 	}
4037 
4038 	if (wbc->range_cyclic || (wbc->nr_to_write > 0 && range_whole))
4039 		mapping->writeback_index = done_index;
4040 
4041 	btrfs_add_delayed_iput(inode);
4042 	return ret;
4043 }
4044 
4045 static void flush_epd_write_bio(struct extent_page_data *epd)
4046 {
4047 	if (epd->bio) {
4048 		int ret;
4049 
4050 		ret = submit_one_bio(epd->bio, 0, 0);
4051 		BUG_ON(ret < 0); /* -ENOMEM */
4052 		epd->bio = NULL;
4053 	}
4054 }
4055 
4056 static noinline void flush_write_bio(void *data)
4057 {
4058 	struct extent_page_data *epd = data;
4059 	flush_epd_write_bio(epd);
4060 }
4061 
4062 int extent_write_full_page(struct extent_io_tree *tree, struct page *page,
4063 			  get_extent_t *get_extent,
4064 			  struct writeback_control *wbc)
4065 {
4066 	int ret;
4067 	struct extent_page_data epd = {
4068 		.bio = NULL,
4069 		.tree = tree,
4070 		.get_extent = get_extent,
4071 		.extent_locked = 0,
4072 		.sync_io = wbc->sync_mode == WB_SYNC_ALL,
4073 	};
4074 
4075 	ret = __extent_writepage(page, wbc, &epd);
4076 
4077 	flush_epd_write_bio(&epd);
4078 	return ret;
4079 }
4080 
4081 int extent_write_locked_range(struct extent_io_tree *tree, struct inode *inode,
4082 			      u64 start, u64 end, get_extent_t *get_extent,
4083 			      int mode)
4084 {
4085 	int ret = 0;
4086 	struct address_space *mapping = inode->i_mapping;
4087 	struct page *page;
4088 	unsigned long nr_pages = (end - start + PAGE_SIZE) >>
4089 		PAGE_SHIFT;
4090 
4091 	struct extent_page_data epd = {
4092 		.bio = NULL,
4093 		.tree = tree,
4094 		.get_extent = get_extent,
4095 		.extent_locked = 1,
4096 		.sync_io = mode == WB_SYNC_ALL,
4097 	};
4098 	struct writeback_control wbc_writepages = {
4099 		.sync_mode	= mode,
4100 		.nr_to_write	= nr_pages * 2,
4101 		.range_start	= start,
4102 		.range_end	= end + 1,
4103 	};
4104 
4105 	while (start <= end) {
4106 		page = find_get_page(mapping, start >> PAGE_SHIFT);
4107 		if (clear_page_dirty_for_io(page))
4108 			ret = __extent_writepage(page, &wbc_writepages, &epd);
4109 		else {
4110 			if (tree->ops && tree->ops->writepage_end_io_hook)
4111 				tree->ops->writepage_end_io_hook(page, start,
4112 						 start + PAGE_SIZE - 1,
4113 						 NULL, 1);
4114 			unlock_page(page);
4115 		}
4116 		put_page(page);
4117 		start += PAGE_SIZE;
4118 	}
4119 
4120 	flush_epd_write_bio(&epd);
4121 	return ret;
4122 }
4123 
4124 int extent_writepages(struct extent_io_tree *tree,
4125 		      struct address_space *mapping,
4126 		      get_extent_t *get_extent,
4127 		      struct writeback_control *wbc)
4128 {
4129 	int ret = 0;
4130 	struct extent_page_data epd = {
4131 		.bio = NULL,
4132 		.tree = tree,
4133 		.get_extent = get_extent,
4134 		.extent_locked = 0,
4135 		.sync_io = wbc->sync_mode == WB_SYNC_ALL,
4136 	};
4137 
4138 	ret = extent_write_cache_pages(mapping, wbc, __extent_writepage, &epd,
4139 				       flush_write_bio);
4140 	flush_epd_write_bio(&epd);
4141 	return ret;
4142 }
4143 
4144 int extent_readpages(struct extent_io_tree *tree,
4145 		     struct address_space *mapping,
4146 		     struct list_head *pages, unsigned nr_pages,
4147 		     get_extent_t get_extent)
4148 {
4149 	struct bio *bio = NULL;
4150 	unsigned page_idx;
4151 	unsigned long bio_flags = 0;
4152 	struct page *pagepool[16];
4153 	struct page *page;
4154 	struct extent_map *em_cached = NULL;
4155 	int nr = 0;
4156 	u64 prev_em_start = (u64)-1;
4157 
4158 	for (page_idx = 0; page_idx < nr_pages; page_idx++) {
4159 		page = list_entry(pages->prev, struct page, lru);
4160 
4161 		prefetchw(&page->flags);
4162 		list_del(&page->lru);
4163 		if (add_to_page_cache_lru(page, mapping,
4164 					page->index,
4165 					readahead_gfp_mask(mapping))) {
4166 			put_page(page);
4167 			continue;
4168 		}
4169 
4170 		pagepool[nr++] = page;
4171 		if (nr < ARRAY_SIZE(pagepool))
4172 			continue;
4173 		__extent_readpages(tree, pagepool, nr, get_extent, &em_cached,
4174 				   &bio, 0, &bio_flags, &prev_em_start);
4175 		nr = 0;
4176 	}
4177 	if (nr)
4178 		__extent_readpages(tree, pagepool, nr, get_extent, &em_cached,
4179 				   &bio, 0, &bio_flags, &prev_em_start);
4180 
4181 	if (em_cached)
4182 		free_extent_map(em_cached);
4183 
4184 	BUG_ON(!list_empty(pages));
4185 	if (bio)
4186 		return submit_one_bio(bio, 0, bio_flags);
4187 	return 0;
4188 }
4189 
4190 /*
4191  * basic invalidatepage code, this waits on any locked or writeback
4192  * ranges corresponding to the page, and then deletes any extent state
4193  * records from the tree
4194  */
4195 int extent_invalidatepage(struct extent_io_tree *tree,
4196 			  struct page *page, unsigned long offset)
4197 {
4198 	struct extent_state *cached_state = NULL;
4199 	u64 start = page_offset(page);
4200 	u64 end = start + PAGE_SIZE - 1;
4201 	size_t blocksize = page->mapping->host->i_sb->s_blocksize;
4202 
4203 	start += ALIGN(offset, blocksize);
4204 	if (start > end)
4205 		return 0;
4206 
4207 	lock_extent_bits(tree, start, end, &cached_state);
4208 	wait_on_page_writeback(page);
4209 	clear_extent_bit(tree, start, end,
4210 			 EXTENT_LOCKED | EXTENT_DIRTY | EXTENT_DELALLOC |
4211 			 EXTENT_DO_ACCOUNTING,
4212 			 1, 1, &cached_state, GFP_NOFS);
4213 	return 0;
4214 }
4215 
4216 /*
4217  * a helper for releasepage, this tests for areas of the page that
4218  * are locked or under IO and drops the related state bits if it is safe
4219  * to drop the page.
4220  */
4221 static int try_release_extent_state(struct extent_map_tree *map,
4222 				    struct extent_io_tree *tree,
4223 				    struct page *page, gfp_t mask)
4224 {
4225 	u64 start = page_offset(page);
4226 	u64 end = start + PAGE_SIZE - 1;
4227 	int ret = 1;
4228 
4229 	if (test_range_bit(tree, start, end,
4230 			   EXTENT_IOBITS, 0, NULL))
4231 		ret = 0;
4232 	else {
4233 		/*
4234 		 * at this point we can safely clear everything except the
4235 		 * locked bit and the nodatasum bit
4236 		 */
4237 		ret = clear_extent_bit(tree, start, end,
4238 				 ~(EXTENT_LOCKED | EXTENT_NODATASUM),
4239 				 0, 0, NULL, mask);
4240 
4241 		/* if clear_extent_bit failed for enomem reasons,
4242 		 * we can't allow the release to continue.
4243 		 */
4244 		if (ret < 0)
4245 			ret = 0;
4246 		else
4247 			ret = 1;
4248 	}
4249 	return ret;
4250 }
4251 
4252 /*
4253  * a helper for releasepage.  As long as there are no locked extents
4254  * in the range corresponding to the page, both state records and extent
4255  * map records are removed
4256  */
4257 int try_release_extent_mapping(struct extent_map_tree *map,
4258 			       struct extent_io_tree *tree, struct page *page,
4259 			       gfp_t mask)
4260 {
4261 	struct extent_map *em;
4262 	u64 start = page_offset(page);
4263 	u64 end = start + PAGE_SIZE - 1;
4264 
4265 	if (gfpflags_allow_blocking(mask) &&
4266 	    page->mapping->host->i_size > SZ_16M) {
4267 		u64 len;
4268 		while (start <= end) {
4269 			len = end - start + 1;
4270 			write_lock(&map->lock);
4271 			em = lookup_extent_mapping(map, start, len);
4272 			if (!em) {
4273 				write_unlock(&map->lock);
4274 				break;
4275 			}
4276 			if (test_bit(EXTENT_FLAG_PINNED, &em->flags) ||
4277 			    em->start != start) {
4278 				write_unlock(&map->lock);
4279 				free_extent_map(em);
4280 				break;
4281 			}
4282 			if (!test_range_bit(tree, em->start,
4283 					    extent_map_end(em) - 1,
4284 					    EXTENT_LOCKED | EXTENT_WRITEBACK,
4285 					    0, NULL)) {
4286 				remove_extent_mapping(map, em);
4287 				/* once for the rb tree */
4288 				free_extent_map(em);
4289 			}
4290 			start = extent_map_end(em);
4291 			write_unlock(&map->lock);
4292 
4293 			/* once for us */
4294 			free_extent_map(em);
4295 		}
4296 	}
4297 	return try_release_extent_state(map, tree, page, mask);
4298 }
4299 
4300 /*
4301  * helper function for fiemap, which doesn't want to see any holes.
4302  * This maps until we find something past 'last'
4303  */
4304 static struct extent_map *get_extent_skip_holes(struct inode *inode,
4305 						u64 offset,
4306 						u64 last,
4307 						get_extent_t *get_extent)
4308 {
4309 	u64 sectorsize = btrfs_inode_sectorsize(inode);
4310 	struct extent_map *em;
4311 	u64 len;
4312 
4313 	if (offset >= last)
4314 		return NULL;
4315 
4316 	while (1) {
4317 		len = last - offset;
4318 		if (len == 0)
4319 			break;
4320 		len = ALIGN(len, sectorsize);
4321 		em = get_extent(BTRFS_I(inode), NULL, 0, offset, len, 0);
4322 		if (IS_ERR_OR_NULL(em))
4323 			return em;
4324 
4325 		/* if this isn't a hole return it */
4326 		if (!test_bit(EXTENT_FLAG_VACANCY, &em->flags) &&
4327 		    em->block_start != EXTENT_MAP_HOLE) {
4328 			return em;
4329 		}
4330 
4331 		/* this is a hole, advance to the next extent */
4332 		offset = extent_map_end(em);
4333 		free_extent_map(em);
4334 		if (offset >= last)
4335 			break;
4336 	}
4337 	return NULL;
4338 }
4339 
4340 /*
4341  * To cache previous fiemap extent
4342  *
4343  * Will be used for merging fiemap extent
4344  */
4345 struct fiemap_cache {
4346 	u64 offset;
4347 	u64 phys;
4348 	u64 len;
4349 	u32 flags;
4350 	bool cached;
4351 };
4352 
4353 /*
4354  * Helper to submit fiemap extent.
4355  *
4356  * Will try to merge current fiemap extent specified by @offset, @phys,
4357  * @len and @flags with cached one.
4358  * And only when we fails to merge, cached one will be submitted as
4359  * fiemap extent.
4360  *
4361  * Return value is the same as fiemap_fill_next_extent().
4362  */
4363 static int emit_fiemap_extent(struct fiemap_extent_info *fieinfo,
4364 				struct fiemap_cache *cache,
4365 				u64 offset, u64 phys, u64 len, u32 flags)
4366 {
4367 	int ret = 0;
4368 
4369 	if (!cache->cached)
4370 		goto assign;
4371 
4372 	/*
4373 	 * Sanity check, extent_fiemap() should have ensured that new
4374 	 * fiemap extent won't overlap with cahced one.
4375 	 * Not recoverable.
4376 	 *
4377 	 * NOTE: Physical address can overlap, due to compression
4378 	 */
4379 	if (cache->offset + cache->len > offset) {
4380 		WARN_ON(1);
4381 		return -EINVAL;
4382 	}
4383 
4384 	/*
4385 	 * Only merges fiemap extents if
4386 	 * 1) Their logical addresses are continuous
4387 	 *
4388 	 * 2) Their physical addresses are continuous
4389 	 *    So truly compressed (physical size smaller than logical size)
4390 	 *    extents won't get merged with each other
4391 	 *
4392 	 * 3) Share same flags except FIEMAP_EXTENT_LAST
4393 	 *    So regular extent won't get merged with prealloc extent
4394 	 */
4395 	if (cache->offset + cache->len  == offset &&
4396 	    cache->phys + cache->len == phys  &&
4397 	    (cache->flags & ~FIEMAP_EXTENT_LAST) ==
4398 			(flags & ~FIEMAP_EXTENT_LAST)) {
4399 		cache->len += len;
4400 		cache->flags |= flags;
4401 		goto try_submit_last;
4402 	}
4403 
4404 	/* Not mergeable, need to submit cached one */
4405 	ret = fiemap_fill_next_extent(fieinfo, cache->offset, cache->phys,
4406 				      cache->len, cache->flags);
4407 	cache->cached = false;
4408 	if (ret)
4409 		return ret;
4410 assign:
4411 	cache->cached = true;
4412 	cache->offset = offset;
4413 	cache->phys = phys;
4414 	cache->len = len;
4415 	cache->flags = flags;
4416 try_submit_last:
4417 	if (cache->flags & FIEMAP_EXTENT_LAST) {
4418 		ret = fiemap_fill_next_extent(fieinfo, cache->offset,
4419 				cache->phys, cache->len, cache->flags);
4420 		cache->cached = false;
4421 	}
4422 	return ret;
4423 }
4424 
4425 /*
4426  * Emit last fiemap cache
4427  *
4428  * The last fiemap cache may still be cached in the following case:
4429  * 0		      4k		    8k
4430  * |<- Fiemap range ->|
4431  * |<------------  First extent ----------->|
4432  *
4433  * In this case, the first extent range will be cached but not emitted.
4434  * So we must emit it before ending extent_fiemap().
4435  */
4436 static int emit_last_fiemap_cache(struct btrfs_fs_info *fs_info,
4437 				  struct fiemap_extent_info *fieinfo,
4438 				  struct fiemap_cache *cache)
4439 {
4440 	int ret;
4441 
4442 	if (!cache->cached)
4443 		return 0;
4444 
4445 	ret = fiemap_fill_next_extent(fieinfo, cache->offset, cache->phys,
4446 				      cache->len, cache->flags);
4447 	cache->cached = false;
4448 	if (ret > 0)
4449 		ret = 0;
4450 	return ret;
4451 }
4452 
4453 int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
4454 		__u64 start, __u64 len, get_extent_t *get_extent)
4455 {
4456 	int ret = 0;
4457 	u64 off = start;
4458 	u64 max = start + len;
4459 	u32 flags = 0;
4460 	u32 found_type;
4461 	u64 last;
4462 	u64 last_for_get_extent = 0;
4463 	u64 disko = 0;
4464 	u64 isize = i_size_read(inode);
4465 	struct btrfs_key found_key;
4466 	struct extent_map *em = NULL;
4467 	struct extent_state *cached_state = NULL;
4468 	struct btrfs_path *path;
4469 	struct btrfs_root *root = BTRFS_I(inode)->root;
4470 	struct fiemap_cache cache = { 0 };
4471 	int end = 0;
4472 	u64 em_start = 0;
4473 	u64 em_len = 0;
4474 	u64 em_end = 0;
4475 
4476 	if (len == 0)
4477 		return -EINVAL;
4478 
4479 	path = btrfs_alloc_path();
4480 	if (!path)
4481 		return -ENOMEM;
4482 	path->leave_spinning = 1;
4483 
4484 	start = round_down(start, btrfs_inode_sectorsize(inode));
4485 	len = round_up(max, btrfs_inode_sectorsize(inode)) - start;
4486 
4487 	/*
4488 	 * lookup the last file extent.  We're not using i_size here
4489 	 * because there might be preallocation past i_size
4490 	 */
4491 	ret = btrfs_lookup_file_extent(NULL, root, path,
4492 			btrfs_ino(BTRFS_I(inode)), -1, 0);
4493 	if (ret < 0) {
4494 		btrfs_free_path(path);
4495 		return ret;
4496 	} else {
4497 		WARN_ON(!ret);
4498 		if (ret == 1)
4499 			ret = 0;
4500 	}
4501 
4502 	path->slots[0]--;
4503 	btrfs_item_key_to_cpu(path->nodes[0], &found_key, path->slots[0]);
4504 	found_type = found_key.type;
4505 
4506 	/* No extents, but there might be delalloc bits */
4507 	if (found_key.objectid != btrfs_ino(BTRFS_I(inode)) ||
4508 	    found_type != BTRFS_EXTENT_DATA_KEY) {
4509 		/* have to trust i_size as the end */
4510 		last = (u64)-1;
4511 		last_for_get_extent = isize;
4512 	} else {
4513 		/*
4514 		 * remember the start of the last extent.  There are a
4515 		 * bunch of different factors that go into the length of the
4516 		 * extent, so its much less complex to remember where it started
4517 		 */
4518 		last = found_key.offset;
4519 		last_for_get_extent = last + 1;
4520 	}
4521 	btrfs_release_path(path);
4522 
4523 	/*
4524 	 * we might have some extents allocated but more delalloc past those
4525 	 * extents.  so, we trust isize unless the start of the last extent is
4526 	 * beyond isize
4527 	 */
4528 	if (last < isize) {
4529 		last = (u64)-1;
4530 		last_for_get_extent = isize;
4531 	}
4532 
4533 	lock_extent_bits(&BTRFS_I(inode)->io_tree, start, start + len - 1,
4534 			 &cached_state);
4535 
4536 	em = get_extent_skip_holes(inode, start, last_for_get_extent,
4537 				   get_extent);
4538 	if (!em)
4539 		goto out;
4540 	if (IS_ERR(em)) {
4541 		ret = PTR_ERR(em);
4542 		goto out;
4543 	}
4544 
4545 	while (!end) {
4546 		u64 offset_in_extent = 0;
4547 
4548 		/* break if the extent we found is outside the range */
4549 		if (em->start >= max || extent_map_end(em) < off)
4550 			break;
4551 
4552 		/*
4553 		 * get_extent may return an extent that starts before our
4554 		 * requested range.  We have to make sure the ranges
4555 		 * we return to fiemap always move forward and don't
4556 		 * overlap, so adjust the offsets here
4557 		 */
4558 		em_start = max(em->start, off);
4559 
4560 		/*
4561 		 * record the offset from the start of the extent
4562 		 * for adjusting the disk offset below.  Only do this if the
4563 		 * extent isn't compressed since our in ram offset may be past
4564 		 * what we have actually allocated on disk.
4565 		 */
4566 		if (!test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
4567 			offset_in_extent = em_start - em->start;
4568 		em_end = extent_map_end(em);
4569 		em_len = em_end - em_start;
4570 		disko = 0;
4571 		flags = 0;
4572 
4573 		/*
4574 		 * bump off for our next call to get_extent
4575 		 */
4576 		off = extent_map_end(em);
4577 		if (off >= max)
4578 			end = 1;
4579 
4580 		if (em->block_start == EXTENT_MAP_LAST_BYTE) {
4581 			end = 1;
4582 			flags |= FIEMAP_EXTENT_LAST;
4583 		} else if (em->block_start == EXTENT_MAP_INLINE) {
4584 			flags |= (FIEMAP_EXTENT_DATA_INLINE |
4585 				  FIEMAP_EXTENT_NOT_ALIGNED);
4586 		} else if (em->block_start == EXTENT_MAP_DELALLOC) {
4587 			flags |= (FIEMAP_EXTENT_DELALLOC |
4588 				  FIEMAP_EXTENT_UNKNOWN);
4589 		} else if (fieinfo->fi_extents_max) {
4590 			u64 bytenr = em->block_start -
4591 				(em->start - em->orig_start);
4592 
4593 			disko = em->block_start + offset_in_extent;
4594 
4595 			/*
4596 			 * As btrfs supports shared space, this information
4597 			 * can be exported to userspace tools via
4598 			 * flag FIEMAP_EXTENT_SHARED.  If fi_extents_max == 0
4599 			 * then we're just getting a count and we can skip the
4600 			 * lookup stuff.
4601 			 */
4602 			ret = btrfs_check_shared(root,
4603 						 btrfs_ino(BTRFS_I(inode)),
4604 						 bytenr);
4605 			if (ret < 0)
4606 				goto out_free;
4607 			if (ret)
4608 				flags |= FIEMAP_EXTENT_SHARED;
4609 			ret = 0;
4610 		}
4611 		if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
4612 			flags |= FIEMAP_EXTENT_ENCODED;
4613 		if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
4614 			flags |= FIEMAP_EXTENT_UNWRITTEN;
4615 
4616 		free_extent_map(em);
4617 		em = NULL;
4618 		if ((em_start >= last) || em_len == (u64)-1 ||
4619 		   (last == (u64)-1 && isize <= em_end)) {
4620 			flags |= FIEMAP_EXTENT_LAST;
4621 			end = 1;
4622 		}
4623 
4624 		/* now scan forward to see if this is really the last extent. */
4625 		em = get_extent_skip_holes(inode, off, last_for_get_extent,
4626 					   get_extent);
4627 		if (IS_ERR(em)) {
4628 			ret = PTR_ERR(em);
4629 			goto out;
4630 		}
4631 		if (!em) {
4632 			flags |= FIEMAP_EXTENT_LAST;
4633 			end = 1;
4634 		}
4635 		ret = emit_fiemap_extent(fieinfo, &cache, em_start, disko,
4636 					   em_len, flags);
4637 		if (ret) {
4638 			if (ret == 1)
4639 				ret = 0;
4640 			goto out_free;
4641 		}
4642 	}
4643 out_free:
4644 	if (!ret)
4645 		ret = emit_last_fiemap_cache(root->fs_info, fieinfo, &cache);
4646 	free_extent_map(em);
4647 out:
4648 	btrfs_free_path(path);
4649 	unlock_extent_cached(&BTRFS_I(inode)->io_tree, start, start + len - 1,
4650 			     &cached_state, GFP_NOFS);
4651 	return ret;
4652 }
4653 
4654 static void __free_extent_buffer(struct extent_buffer *eb)
4655 {
4656 	btrfs_leak_debug_del(&eb->leak_list);
4657 	kmem_cache_free(extent_buffer_cache, eb);
4658 }
4659 
4660 int extent_buffer_under_io(struct extent_buffer *eb)
4661 {
4662 	return (atomic_read(&eb->io_pages) ||
4663 		test_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags) ||
4664 		test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
4665 }
4666 
4667 /*
4668  * Helper for releasing extent buffer page.
4669  */
4670 static void btrfs_release_extent_buffer_page(struct extent_buffer *eb)
4671 {
4672 	unsigned long index;
4673 	struct page *page;
4674 	int mapped = !test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags);
4675 
4676 	BUG_ON(extent_buffer_under_io(eb));
4677 
4678 	index = num_extent_pages(eb->start, eb->len);
4679 	if (index == 0)
4680 		return;
4681 
4682 	do {
4683 		index--;
4684 		page = eb->pages[index];
4685 		if (!page)
4686 			continue;
4687 		if (mapped)
4688 			spin_lock(&page->mapping->private_lock);
4689 		/*
4690 		 * We do this since we'll remove the pages after we've
4691 		 * removed the eb from the radix tree, so we could race
4692 		 * and have this page now attached to the new eb.  So
4693 		 * only clear page_private if it's still connected to
4694 		 * this eb.
4695 		 */
4696 		if (PagePrivate(page) &&
4697 		    page->private == (unsigned long)eb) {
4698 			BUG_ON(test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
4699 			BUG_ON(PageDirty(page));
4700 			BUG_ON(PageWriteback(page));
4701 			/*
4702 			 * We need to make sure we haven't be attached
4703 			 * to a new eb.
4704 			 */
4705 			ClearPagePrivate(page);
4706 			set_page_private(page, 0);
4707 			/* One for the page private */
4708 			put_page(page);
4709 		}
4710 
4711 		if (mapped)
4712 			spin_unlock(&page->mapping->private_lock);
4713 
4714 		/* One for when we allocated the page */
4715 		put_page(page);
4716 	} while (index != 0);
4717 }
4718 
4719 /*
4720  * Helper for releasing the extent buffer.
4721  */
4722 static inline void btrfs_release_extent_buffer(struct extent_buffer *eb)
4723 {
4724 	btrfs_release_extent_buffer_page(eb);
4725 	__free_extent_buffer(eb);
4726 }
4727 
4728 static struct extent_buffer *
4729 __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
4730 		      unsigned long len)
4731 {
4732 	struct extent_buffer *eb = NULL;
4733 
4734 	eb = kmem_cache_zalloc(extent_buffer_cache, GFP_NOFS|__GFP_NOFAIL);
4735 	eb->start = start;
4736 	eb->len = len;
4737 	eb->fs_info = fs_info;
4738 	eb->bflags = 0;
4739 	rwlock_init(&eb->lock);
4740 	atomic_set(&eb->write_locks, 0);
4741 	atomic_set(&eb->read_locks, 0);
4742 	atomic_set(&eb->blocking_readers, 0);
4743 	atomic_set(&eb->blocking_writers, 0);
4744 	atomic_set(&eb->spinning_readers, 0);
4745 	atomic_set(&eb->spinning_writers, 0);
4746 	eb->lock_nested = 0;
4747 	init_waitqueue_head(&eb->write_lock_wq);
4748 	init_waitqueue_head(&eb->read_lock_wq);
4749 
4750 	btrfs_leak_debug_add(&eb->leak_list, &buffers);
4751 
4752 	spin_lock_init(&eb->refs_lock);
4753 	atomic_set(&eb->refs, 1);
4754 	atomic_set(&eb->io_pages, 0);
4755 
4756 	/*
4757 	 * Sanity checks, currently the maximum is 64k covered by 16x 4k pages
4758 	 */
4759 	BUILD_BUG_ON(BTRFS_MAX_METADATA_BLOCKSIZE
4760 		> MAX_INLINE_EXTENT_BUFFER_SIZE);
4761 	BUG_ON(len > MAX_INLINE_EXTENT_BUFFER_SIZE);
4762 
4763 	return eb;
4764 }
4765 
4766 struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src)
4767 {
4768 	unsigned long i;
4769 	struct page *p;
4770 	struct extent_buffer *new;
4771 	unsigned long num_pages = num_extent_pages(src->start, src->len);
4772 
4773 	new = __alloc_extent_buffer(src->fs_info, src->start, src->len);
4774 	if (new == NULL)
4775 		return NULL;
4776 
4777 	for (i = 0; i < num_pages; i++) {
4778 		p = alloc_page(GFP_NOFS);
4779 		if (!p) {
4780 			btrfs_release_extent_buffer(new);
4781 			return NULL;
4782 		}
4783 		attach_extent_buffer_page(new, p);
4784 		WARN_ON(PageDirty(p));
4785 		SetPageUptodate(p);
4786 		new->pages[i] = p;
4787 		copy_page(page_address(p), page_address(src->pages[i]));
4788 	}
4789 
4790 	set_bit(EXTENT_BUFFER_UPTODATE, &new->bflags);
4791 	set_bit(EXTENT_BUFFER_DUMMY, &new->bflags);
4792 
4793 	return new;
4794 }
4795 
4796 struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
4797 						  u64 start, unsigned long len)
4798 {
4799 	struct extent_buffer *eb;
4800 	unsigned long num_pages;
4801 	unsigned long i;
4802 
4803 	num_pages = num_extent_pages(start, len);
4804 
4805 	eb = __alloc_extent_buffer(fs_info, start, len);
4806 	if (!eb)
4807 		return NULL;
4808 
4809 	for (i = 0; i < num_pages; i++) {
4810 		eb->pages[i] = alloc_page(GFP_NOFS);
4811 		if (!eb->pages[i])
4812 			goto err;
4813 	}
4814 	set_extent_buffer_uptodate(eb);
4815 	btrfs_set_header_nritems(eb, 0);
4816 	set_bit(EXTENT_BUFFER_DUMMY, &eb->bflags);
4817 
4818 	return eb;
4819 err:
4820 	for (; i > 0; i--)
4821 		__free_page(eb->pages[i - 1]);
4822 	__free_extent_buffer(eb);
4823 	return NULL;
4824 }
4825 
4826 struct extent_buffer *alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
4827 						u64 start)
4828 {
4829 	return __alloc_dummy_extent_buffer(fs_info, start, fs_info->nodesize);
4830 }
4831 
4832 static void check_buffer_tree_ref(struct extent_buffer *eb)
4833 {
4834 	int refs;
4835 	/* the ref bit is tricky.  We have to make sure it is set
4836 	 * if we have the buffer dirty.   Otherwise the
4837 	 * code to free a buffer can end up dropping a dirty
4838 	 * page
4839 	 *
4840 	 * Once the ref bit is set, it won't go away while the
4841 	 * buffer is dirty or in writeback, and it also won't
4842 	 * go away while we have the reference count on the
4843 	 * eb bumped.
4844 	 *
4845 	 * We can't just set the ref bit without bumping the
4846 	 * ref on the eb because free_extent_buffer might
4847 	 * see the ref bit and try to clear it.  If this happens
4848 	 * free_extent_buffer might end up dropping our original
4849 	 * ref by mistake and freeing the page before we are able
4850 	 * to add one more ref.
4851 	 *
4852 	 * So bump the ref count first, then set the bit.  If someone
4853 	 * beat us to it, drop the ref we added.
4854 	 */
4855 	refs = atomic_read(&eb->refs);
4856 	if (refs >= 2 && test_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
4857 		return;
4858 
4859 	spin_lock(&eb->refs_lock);
4860 	if (!test_and_set_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
4861 		atomic_inc(&eb->refs);
4862 	spin_unlock(&eb->refs_lock);
4863 }
4864 
4865 static void mark_extent_buffer_accessed(struct extent_buffer *eb,
4866 		struct page *accessed)
4867 {
4868 	unsigned long num_pages, i;
4869 
4870 	check_buffer_tree_ref(eb);
4871 
4872 	num_pages = num_extent_pages(eb->start, eb->len);
4873 	for (i = 0; i < num_pages; i++) {
4874 		struct page *p = eb->pages[i];
4875 
4876 		if (p != accessed)
4877 			mark_page_accessed(p);
4878 	}
4879 }
4880 
4881 struct extent_buffer *find_extent_buffer(struct btrfs_fs_info *fs_info,
4882 					 u64 start)
4883 {
4884 	struct extent_buffer *eb;
4885 
4886 	rcu_read_lock();
4887 	eb = radix_tree_lookup(&fs_info->buffer_radix,
4888 			       start >> PAGE_SHIFT);
4889 	if (eb && atomic_inc_not_zero(&eb->refs)) {
4890 		rcu_read_unlock();
4891 		/*
4892 		 * Lock our eb's refs_lock to avoid races with
4893 		 * free_extent_buffer. When we get our eb it might be flagged
4894 		 * with EXTENT_BUFFER_STALE and another task running
4895 		 * free_extent_buffer might have seen that flag set,
4896 		 * eb->refs == 2, that the buffer isn't under IO (dirty and
4897 		 * writeback flags not set) and it's still in the tree (flag
4898 		 * EXTENT_BUFFER_TREE_REF set), therefore being in the process
4899 		 * of decrementing the extent buffer's reference count twice.
4900 		 * So here we could race and increment the eb's reference count,
4901 		 * clear its stale flag, mark it as dirty and drop our reference
4902 		 * before the other task finishes executing free_extent_buffer,
4903 		 * which would later result in an attempt to free an extent
4904 		 * buffer that is dirty.
4905 		 */
4906 		if (test_bit(EXTENT_BUFFER_STALE, &eb->bflags)) {
4907 			spin_lock(&eb->refs_lock);
4908 			spin_unlock(&eb->refs_lock);
4909 		}
4910 		mark_extent_buffer_accessed(eb, NULL);
4911 		return eb;
4912 	}
4913 	rcu_read_unlock();
4914 
4915 	return NULL;
4916 }
4917 
4918 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
4919 struct extent_buffer *alloc_test_extent_buffer(struct btrfs_fs_info *fs_info,
4920 					u64 start)
4921 {
4922 	struct extent_buffer *eb, *exists = NULL;
4923 	int ret;
4924 
4925 	eb = find_extent_buffer(fs_info, start);
4926 	if (eb)
4927 		return eb;
4928 	eb = alloc_dummy_extent_buffer(fs_info, start);
4929 	if (!eb)
4930 		return NULL;
4931 	eb->fs_info = fs_info;
4932 again:
4933 	ret = radix_tree_preload(GFP_NOFS);
4934 	if (ret)
4935 		goto free_eb;
4936 	spin_lock(&fs_info->buffer_lock);
4937 	ret = radix_tree_insert(&fs_info->buffer_radix,
4938 				start >> PAGE_SHIFT, eb);
4939 	spin_unlock(&fs_info->buffer_lock);
4940 	radix_tree_preload_end();
4941 	if (ret == -EEXIST) {
4942 		exists = find_extent_buffer(fs_info, start);
4943 		if (exists)
4944 			goto free_eb;
4945 		else
4946 			goto again;
4947 	}
4948 	check_buffer_tree_ref(eb);
4949 	set_bit(EXTENT_BUFFER_IN_TREE, &eb->bflags);
4950 
4951 	/*
4952 	 * We will free dummy extent buffer's if they come into
4953 	 * free_extent_buffer with a ref count of 2, but if we are using this we
4954 	 * want the buffers to stay in memory until we're done with them, so
4955 	 * bump the ref count again.
4956 	 */
4957 	atomic_inc(&eb->refs);
4958 	return eb;
4959 free_eb:
4960 	btrfs_release_extent_buffer(eb);
4961 	return exists;
4962 }
4963 #endif
4964 
4965 struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
4966 					  u64 start)
4967 {
4968 	unsigned long len = fs_info->nodesize;
4969 	unsigned long num_pages = num_extent_pages(start, len);
4970 	unsigned long i;
4971 	unsigned long index = start >> PAGE_SHIFT;
4972 	struct extent_buffer *eb;
4973 	struct extent_buffer *exists = NULL;
4974 	struct page *p;
4975 	struct address_space *mapping = fs_info->btree_inode->i_mapping;
4976 	int uptodate = 1;
4977 	int ret;
4978 
4979 	if (!IS_ALIGNED(start, fs_info->sectorsize)) {
4980 		btrfs_err(fs_info, "bad tree block start %llu", start);
4981 		return ERR_PTR(-EINVAL);
4982 	}
4983 
4984 	eb = find_extent_buffer(fs_info, start);
4985 	if (eb)
4986 		return eb;
4987 
4988 	eb = __alloc_extent_buffer(fs_info, start, len);
4989 	if (!eb)
4990 		return ERR_PTR(-ENOMEM);
4991 
4992 	for (i = 0; i < num_pages; i++, index++) {
4993 		p = find_or_create_page(mapping, index, GFP_NOFS|__GFP_NOFAIL);
4994 		if (!p) {
4995 			exists = ERR_PTR(-ENOMEM);
4996 			goto free_eb;
4997 		}
4998 
4999 		spin_lock(&mapping->private_lock);
5000 		if (PagePrivate(p)) {
5001 			/*
5002 			 * We could have already allocated an eb for this page
5003 			 * and attached one so lets see if we can get a ref on
5004 			 * the existing eb, and if we can we know it's good and
5005 			 * we can just return that one, else we know we can just
5006 			 * overwrite page->private.
5007 			 */
5008 			exists = (struct extent_buffer *)p->private;
5009 			if (atomic_inc_not_zero(&exists->refs)) {
5010 				spin_unlock(&mapping->private_lock);
5011 				unlock_page(p);
5012 				put_page(p);
5013 				mark_extent_buffer_accessed(exists, p);
5014 				goto free_eb;
5015 			}
5016 			exists = NULL;
5017 
5018 			/*
5019 			 * Do this so attach doesn't complain and we need to
5020 			 * drop the ref the old guy had.
5021 			 */
5022 			ClearPagePrivate(p);
5023 			WARN_ON(PageDirty(p));
5024 			put_page(p);
5025 		}
5026 		attach_extent_buffer_page(eb, p);
5027 		spin_unlock(&mapping->private_lock);
5028 		WARN_ON(PageDirty(p));
5029 		eb->pages[i] = p;
5030 		if (!PageUptodate(p))
5031 			uptodate = 0;
5032 
5033 		/*
5034 		 * see below about how we avoid a nasty race with release page
5035 		 * and why we unlock later
5036 		 */
5037 	}
5038 	if (uptodate)
5039 		set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
5040 again:
5041 	ret = radix_tree_preload(GFP_NOFS);
5042 	if (ret) {
5043 		exists = ERR_PTR(ret);
5044 		goto free_eb;
5045 	}
5046 
5047 	spin_lock(&fs_info->buffer_lock);
5048 	ret = radix_tree_insert(&fs_info->buffer_radix,
5049 				start >> PAGE_SHIFT, eb);
5050 	spin_unlock(&fs_info->buffer_lock);
5051 	radix_tree_preload_end();
5052 	if (ret == -EEXIST) {
5053 		exists = find_extent_buffer(fs_info, start);
5054 		if (exists)
5055 			goto free_eb;
5056 		else
5057 			goto again;
5058 	}
5059 	/* add one reference for the tree */
5060 	check_buffer_tree_ref(eb);
5061 	set_bit(EXTENT_BUFFER_IN_TREE, &eb->bflags);
5062 
5063 	/*
5064 	 * there is a race where release page may have
5065 	 * tried to find this extent buffer in the radix
5066 	 * but failed.  It will tell the VM it is safe to
5067 	 * reclaim the, and it will clear the page private bit.
5068 	 * We must make sure to set the page private bit properly
5069 	 * after the extent buffer is in the radix tree so
5070 	 * it doesn't get lost
5071 	 */
5072 	SetPageChecked(eb->pages[0]);
5073 	for (i = 1; i < num_pages; i++) {
5074 		p = eb->pages[i];
5075 		ClearPageChecked(p);
5076 		unlock_page(p);
5077 	}
5078 	unlock_page(eb->pages[0]);
5079 	return eb;
5080 
5081 free_eb:
5082 	WARN_ON(!atomic_dec_and_test(&eb->refs));
5083 	for (i = 0; i < num_pages; i++) {
5084 		if (eb->pages[i])
5085 			unlock_page(eb->pages[i]);
5086 	}
5087 
5088 	btrfs_release_extent_buffer(eb);
5089 	return exists;
5090 }
5091 
5092 static inline void btrfs_release_extent_buffer_rcu(struct rcu_head *head)
5093 {
5094 	struct extent_buffer *eb =
5095 			container_of(head, struct extent_buffer, rcu_head);
5096 
5097 	__free_extent_buffer(eb);
5098 }
5099 
5100 /* Expects to have eb->eb_lock already held */
5101 static int release_extent_buffer(struct extent_buffer *eb)
5102 {
5103 	WARN_ON(atomic_read(&eb->refs) == 0);
5104 	if (atomic_dec_and_test(&eb->refs)) {
5105 		if (test_and_clear_bit(EXTENT_BUFFER_IN_TREE, &eb->bflags)) {
5106 			struct btrfs_fs_info *fs_info = eb->fs_info;
5107 
5108 			spin_unlock(&eb->refs_lock);
5109 
5110 			spin_lock(&fs_info->buffer_lock);
5111 			radix_tree_delete(&fs_info->buffer_radix,
5112 					  eb->start >> PAGE_SHIFT);
5113 			spin_unlock(&fs_info->buffer_lock);
5114 		} else {
5115 			spin_unlock(&eb->refs_lock);
5116 		}
5117 
5118 		/* Should be safe to release our pages at this point */
5119 		btrfs_release_extent_buffer_page(eb);
5120 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
5121 		if (unlikely(test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags))) {
5122 			__free_extent_buffer(eb);
5123 			return 1;
5124 		}
5125 #endif
5126 		call_rcu(&eb->rcu_head, btrfs_release_extent_buffer_rcu);
5127 		return 1;
5128 	}
5129 	spin_unlock(&eb->refs_lock);
5130 
5131 	return 0;
5132 }
5133 
5134 void free_extent_buffer(struct extent_buffer *eb)
5135 {
5136 	int refs;
5137 	int old;
5138 	if (!eb)
5139 		return;
5140 
5141 	while (1) {
5142 		refs = atomic_read(&eb->refs);
5143 		if (refs <= 3)
5144 			break;
5145 		old = atomic_cmpxchg(&eb->refs, refs, refs - 1);
5146 		if (old == refs)
5147 			return;
5148 	}
5149 
5150 	spin_lock(&eb->refs_lock);
5151 	if (atomic_read(&eb->refs) == 2 &&
5152 	    test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags))
5153 		atomic_dec(&eb->refs);
5154 
5155 	if (atomic_read(&eb->refs) == 2 &&
5156 	    test_bit(EXTENT_BUFFER_STALE, &eb->bflags) &&
5157 	    !extent_buffer_under_io(eb) &&
5158 	    test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
5159 		atomic_dec(&eb->refs);
5160 
5161 	/*
5162 	 * I know this is terrible, but it's temporary until we stop tracking
5163 	 * the uptodate bits and such for the extent buffers.
5164 	 */
5165 	release_extent_buffer(eb);
5166 }
5167 
5168 void free_extent_buffer_stale(struct extent_buffer *eb)
5169 {
5170 	if (!eb)
5171 		return;
5172 
5173 	spin_lock(&eb->refs_lock);
5174 	set_bit(EXTENT_BUFFER_STALE, &eb->bflags);
5175 
5176 	if (atomic_read(&eb->refs) == 2 && !extent_buffer_under_io(eb) &&
5177 	    test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags))
5178 		atomic_dec(&eb->refs);
5179 	release_extent_buffer(eb);
5180 }
5181 
5182 void clear_extent_buffer_dirty(struct extent_buffer *eb)
5183 {
5184 	unsigned long i;
5185 	unsigned long num_pages;
5186 	struct page *page;
5187 
5188 	num_pages = num_extent_pages(eb->start, eb->len);
5189 
5190 	for (i = 0; i < num_pages; i++) {
5191 		page = eb->pages[i];
5192 		if (!PageDirty(page))
5193 			continue;
5194 
5195 		lock_page(page);
5196 		WARN_ON(!PagePrivate(page));
5197 
5198 		clear_page_dirty_for_io(page);
5199 		spin_lock_irq(&page->mapping->tree_lock);
5200 		if (!PageDirty(page)) {
5201 			radix_tree_tag_clear(&page->mapping->page_tree,
5202 						page_index(page),
5203 						PAGECACHE_TAG_DIRTY);
5204 		}
5205 		spin_unlock_irq(&page->mapping->tree_lock);
5206 		ClearPageError(page);
5207 		unlock_page(page);
5208 	}
5209 	WARN_ON(atomic_read(&eb->refs) == 0);
5210 }
5211 
5212 int set_extent_buffer_dirty(struct extent_buffer *eb)
5213 {
5214 	unsigned long i;
5215 	unsigned long num_pages;
5216 	int was_dirty = 0;
5217 
5218 	check_buffer_tree_ref(eb);
5219 
5220 	was_dirty = test_and_set_bit(EXTENT_BUFFER_DIRTY, &eb->bflags);
5221 
5222 	num_pages = num_extent_pages(eb->start, eb->len);
5223 	WARN_ON(atomic_read(&eb->refs) == 0);
5224 	WARN_ON(!test_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags));
5225 
5226 	for (i = 0; i < num_pages; i++)
5227 		set_page_dirty(eb->pages[i]);
5228 	return was_dirty;
5229 }
5230 
5231 void clear_extent_buffer_uptodate(struct extent_buffer *eb)
5232 {
5233 	unsigned long i;
5234 	struct page *page;
5235 	unsigned long num_pages;
5236 
5237 	clear_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
5238 	num_pages = num_extent_pages(eb->start, eb->len);
5239 	for (i = 0; i < num_pages; i++) {
5240 		page = eb->pages[i];
5241 		if (page)
5242 			ClearPageUptodate(page);
5243 	}
5244 }
5245 
5246 void set_extent_buffer_uptodate(struct extent_buffer *eb)
5247 {
5248 	unsigned long i;
5249 	struct page *page;
5250 	unsigned long num_pages;
5251 
5252 	set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
5253 	num_pages = num_extent_pages(eb->start, eb->len);
5254 	for (i = 0; i < num_pages; i++) {
5255 		page = eb->pages[i];
5256 		SetPageUptodate(page);
5257 	}
5258 }
5259 
5260 int extent_buffer_uptodate(struct extent_buffer *eb)
5261 {
5262 	return test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
5263 }
5264 
5265 int read_extent_buffer_pages(struct extent_io_tree *tree,
5266 			     struct extent_buffer *eb, int wait,
5267 			     get_extent_t *get_extent, int mirror_num)
5268 {
5269 	unsigned long i;
5270 	struct page *page;
5271 	int err;
5272 	int ret = 0;
5273 	int locked_pages = 0;
5274 	int all_uptodate = 1;
5275 	unsigned long num_pages;
5276 	unsigned long num_reads = 0;
5277 	struct bio *bio = NULL;
5278 	unsigned long bio_flags = 0;
5279 
5280 	if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
5281 		return 0;
5282 
5283 	num_pages = num_extent_pages(eb->start, eb->len);
5284 	for (i = 0; i < num_pages; i++) {
5285 		page = eb->pages[i];
5286 		if (wait == WAIT_NONE) {
5287 			if (!trylock_page(page))
5288 				goto unlock_exit;
5289 		} else {
5290 			lock_page(page);
5291 		}
5292 		locked_pages++;
5293 	}
5294 	/*
5295 	 * We need to firstly lock all pages to make sure that
5296 	 * the uptodate bit of our pages won't be affected by
5297 	 * clear_extent_buffer_uptodate().
5298 	 */
5299 	for (i = 0; i < num_pages; i++) {
5300 		page = eb->pages[i];
5301 		if (!PageUptodate(page)) {
5302 			num_reads++;
5303 			all_uptodate = 0;
5304 		}
5305 	}
5306 
5307 	if (all_uptodate) {
5308 		set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
5309 		goto unlock_exit;
5310 	}
5311 
5312 	clear_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags);
5313 	eb->read_mirror = 0;
5314 	atomic_set(&eb->io_pages, num_reads);
5315 	for (i = 0; i < num_pages; i++) {
5316 		page = eb->pages[i];
5317 
5318 		if (!PageUptodate(page)) {
5319 			if (ret) {
5320 				atomic_dec(&eb->io_pages);
5321 				unlock_page(page);
5322 				continue;
5323 			}
5324 
5325 			ClearPageError(page);
5326 			err = __extent_read_full_page(tree, page,
5327 						      get_extent, &bio,
5328 						      mirror_num, &bio_flags,
5329 						      REQ_META);
5330 			if (err) {
5331 				ret = err;
5332 				/*
5333 				 * We use &bio in above __extent_read_full_page,
5334 				 * so we ensure that if it returns error, the
5335 				 * current page fails to add itself to bio and
5336 				 * it's been unlocked.
5337 				 *
5338 				 * We must dec io_pages by ourselves.
5339 				 */
5340 				atomic_dec(&eb->io_pages);
5341 			}
5342 		} else {
5343 			unlock_page(page);
5344 		}
5345 	}
5346 
5347 	if (bio) {
5348 		err = submit_one_bio(bio, mirror_num, bio_flags);
5349 		if (err)
5350 			return err;
5351 	}
5352 
5353 	if (ret || wait != WAIT_COMPLETE)
5354 		return ret;
5355 
5356 	for (i = 0; i < num_pages; i++) {
5357 		page = eb->pages[i];
5358 		wait_on_page_locked(page);
5359 		if (!PageUptodate(page))
5360 			ret = -EIO;
5361 	}
5362 
5363 	return ret;
5364 
5365 unlock_exit:
5366 	while (locked_pages > 0) {
5367 		locked_pages--;
5368 		page = eb->pages[locked_pages];
5369 		unlock_page(page);
5370 	}
5371 	return ret;
5372 }
5373 
5374 void read_extent_buffer(const struct extent_buffer *eb, void *dstv,
5375 			unsigned long start, unsigned long len)
5376 {
5377 	size_t cur;
5378 	size_t offset;
5379 	struct page *page;
5380 	char *kaddr;
5381 	char *dst = (char *)dstv;
5382 	size_t start_offset = eb->start & ((u64)PAGE_SIZE - 1);
5383 	unsigned long i = (start_offset + start) >> PAGE_SHIFT;
5384 
5385 	if (start + len > eb->len) {
5386 		WARN(1, KERN_ERR "btrfs bad mapping eb start %llu len %lu, wanted %lu %lu\n",
5387 		     eb->start, eb->len, start, len);
5388 		memset(dst, 0, len);
5389 		return;
5390 	}
5391 
5392 	offset = (start_offset + start) & (PAGE_SIZE - 1);
5393 
5394 	while (len > 0) {
5395 		page = eb->pages[i];
5396 
5397 		cur = min(len, (PAGE_SIZE - offset));
5398 		kaddr = page_address(page);
5399 		memcpy(dst, kaddr + offset, cur);
5400 
5401 		dst += cur;
5402 		len -= cur;
5403 		offset = 0;
5404 		i++;
5405 	}
5406 }
5407 
5408 int read_extent_buffer_to_user(const struct extent_buffer *eb,
5409 			       void __user *dstv,
5410 			       unsigned long start, unsigned long len)
5411 {
5412 	size_t cur;
5413 	size_t offset;
5414 	struct page *page;
5415 	char *kaddr;
5416 	char __user *dst = (char __user *)dstv;
5417 	size_t start_offset = eb->start & ((u64)PAGE_SIZE - 1);
5418 	unsigned long i = (start_offset + start) >> PAGE_SHIFT;
5419 	int ret = 0;
5420 
5421 	WARN_ON(start > eb->len);
5422 	WARN_ON(start + len > eb->start + eb->len);
5423 
5424 	offset = (start_offset + start) & (PAGE_SIZE - 1);
5425 
5426 	while (len > 0) {
5427 		page = eb->pages[i];
5428 
5429 		cur = min(len, (PAGE_SIZE - offset));
5430 		kaddr = page_address(page);
5431 		if (copy_to_user(dst, kaddr + offset, cur)) {
5432 			ret = -EFAULT;
5433 			break;
5434 		}
5435 
5436 		dst += cur;
5437 		len -= cur;
5438 		offset = 0;
5439 		i++;
5440 	}
5441 
5442 	return ret;
5443 }
5444 
5445 /*
5446  * return 0 if the item is found within a page.
5447  * return 1 if the item spans two pages.
5448  * return -EINVAL otherwise.
5449  */
5450 int map_private_extent_buffer(const struct extent_buffer *eb,
5451 			      unsigned long start, unsigned long min_len,
5452 			      char **map, unsigned long *map_start,
5453 			      unsigned long *map_len)
5454 {
5455 	size_t offset = start & (PAGE_SIZE - 1);
5456 	char *kaddr;
5457 	struct page *p;
5458 	size_t start_offset = eb->start & ((u64)PAGE_SIZE - 1);
5459 	unsigned long i = (start_offset + start) >> PAGE_SHIFT;
5460 	unsigned long end_i = (start_offset + start + min_len - 1) >>
5461 		PAGE_SHIFT;
5462 
5463 	if (start + min_len > eb->len) {
5464 		WARN(1, KERN_ERR "btrfs bad mapping eb start %llu len %lu, wanted %lu %lu\n",
5465 		       eb->start, eb->len, start, min_len);
5466 		return -EINVAL;
5467 	}
5468 
5469 	if (i != end_i)
5470 		return 1;
5471 
5472 	if (i == 0) {
5473 		offset = start_offset;
5474 		*map_start = 0;
5475 	} else {
5476 		offset = 0;
5477 		*map_start = ((u64)i << PAGE_SHIFT) - start_offset;
5478 	}
5479 
5480 	p = eb->pages[i];
5481 	kaddr = page_address(p);
5482 	*map = kaddr + offset;
5483 	*map_len = PAGE_SIZE - offset;
5484 	return 0;
5485 }
5486 
5487 int memcmp_extent_buffer(const struct extent_buffer *eb, const void *ptrv,
5488 			 unsigned long start, unsigned long len)
5489 {
5490 	size_t cur;
5491 	size_t offset;
5492 	struct page *page;
5493 	char *kaddr;
5494 	char *ptr = (char *)ptrv;
5495 	size_t start_offset = eb->start & ((u64)PAGE_SIZE - 1);
5496 	unsigned long i = (start_offset + start) >> PAGE_SHIFT;
5497 	int ret = 0;
5498 
5499 	WARN_ON(start > eb->len);
5500 	WARN_ON(start + len > eb->start + eb->len);
5501 
5502 	offset = (start_offset + start) & (PAGE_SIZE - 1);
5503 
5504 	while (len > 0) {
5505 		page = eb->pages[i];
5506 
5507 		cur = min(len, (PAGE_SIZE - offset));
5508 
5509 		kaddr = page_address(page);
5510 		ret = memcmp(ptr, kaddr + offset, cur);
5511 		if (ret)
5512 			break;
5513 
5514 		ptr += cur;
5515 		len -= cur;
5516 		offset = 0;
5517 		i++;
5518 	}
5519 	return ret;
5520 }
5521 
5522 void write_extent_buffer_chunk_tree_uuid(struct extent_buffer *eb,
5523 		const void *srcv)
5524 {
5525 	char *kaddr;
5526 
5527 	WARN_ON(!PageUptodate(eb->pages[0]));
5528 	kaddr = page_address(eb->pages[0]);
5529 	memcpy(kaddr + offsetof(struct btrfs_header, chunk_tree_uuid), srcv,
5530 			BTRFS_FSID_SIZE);
5531 }
5532 
5533 void write_extent_buffer_fsid(struct extent_buffer *eb, const void *srcv)
5534 {
5535 	char *kaddr;
5536 
5537 	WARN_ON(!PageUptodate(eb->pages[0]));
5538 	kaddr = page_address(eb->pages[0]);
5539 	memcpy(kaddr + offsetof(struct btrfs_header, fsid), srcv,
5540 			BTRFS_FSID_SIZE);
5541 }
5542 
5543 void write_extent_buffer(struct extent_buffer *eb, const void *srcv,
5544 			 unsigned long start, unsigned long len)
5545 {
5546 	size_t cur;
5547 	size_t offset;
5548 	struct page *page;
5549 	char *kaddr;
5550 	char *src = (char *)srcv;
5551 	size_t start_offset = eb->start & ((u64)PAGE_SIZE - 1);
5552 	unsigned long i = (start_offset + start) >> PAGE_SHIFT;
5553 
5554 	WARN_ON(start > eb->len);
5555 	WARN_ON(start + len > eb->start + eb->len);
5556 
5557 	offset = (start_offset + start) & (PAGE_SIZE - 1);
5558 
5559 	while (len > 0) {
5560 		page = eb->pages[i];
5561 		WARN_ON(!PageUptodate(page));
5562 
5563 		cur = min(len, PAGE_SIZE - offset);
5564 		kaddr = page_address(page);
5565 		memcpy(kaddr + offset, src, cur);
5566 
5567 		src += cur;
5568 		len -= cur;
5569 		offset = 0;
5570 		i++;
5571 	}
5572 }
5573 
5574 void memzero_extent_buffer(struct extent_buffer *eb, unsigned long start,
5575 		unsigned long len)
5576 {
5577 	size_t cur;
5578 	size_t offset;
5579 	struct page *page;
5580 	char *kaddr;
5581 	size_t start_offset = eb->start & ((u64)PAGE_SIZE - 1);
5582 	unsigned long i = (start_offset + start) >> PAGE_SHIFT;
5583 
5584 	WARN_ON(start > eb->len);
5585 	WARN_ON(start + len > eb->start + eb->len);
5586 
5587 	offset = (start_offset + start) & (PAGE_SIZE - 1);
5588 
5589 	while (len > 0) {
5590 		page = eb->pages[i];
5591 		WARN_ON(!PageUptodate(page));
5592 
5593 		cur = min(len, PAGE_SIZE - offset);
5594 		kaddr = page_address(page);
5595 		memset(kaddr + offset, 0, cur);
5596 
5597 		len -= cur;
5598 		offset = 0;
5599 		i++;
5600 	}
5601 }
5602 
5603 void copy_extent_buffer_full(struct extent_buffer *dst,
5604 			     struct extent_buffer *src)
5605 {
5606 	int i;
5607 	unsigned num_pages;
5608 
5609 	ASSERT(dst->len == src->len);
5610 
5611 	num_pages = num_extent_pages(dst->start, dst->len);
5612 	for (i = 0; i < num_pages; i++)
5613 		copy_page(page_address(dst->pages[i]),
5614 				page_address(src->pages[i]));
5615 }
5616 
5617 void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src,
5618 			unsigned long dst_offset, unsigned long src_offset,
5619 			unsigned long len)
5620 {
5621 	u64 dst_len = dst->len;
5622 	size_t cur;
5623 	size_t offset;
5624 	struct page *page;
5625 	char *kaddr;
5626 	size_t start_offset = dst->start & ((u64)PAGE_SIZE - 1);
5627 	unsigned long i = (start_offset + dst_offset) >> PAGE_SHIFT;
5628 
5629 	WARN_ON(src->len != dst_len);
5630 
5631 	offset = (start_offset + dst_offset) &
5632 		(PAGE_SIZE - 1);
5633 
5634 	while (len > 0) {
5635 		page = dst->pages[i];
5636 		WARN_ON(!PageUptodate(page));
5637 
5638 		cur = min(len, (unsigned long)(PAGE_SIZE - offset));
5639 
5640 		kaddr = page_address(page);
5641 		read_extent_buffer(src, kaddr + offset, src_offset, cur);
5642 
5643 		src_offset += cur;
5644 		len -= cur;
5645 		offset = 0;
5646 		i++;
5647 	}
5648 }
5649 
5650 void le_bitmap_set(u8 *map, unsigned int start, int len)
5651 {
5652 	u8 *p = map + BIT_BYTE(start);
5653 	const unsigned int size = start + len;
5654 	int bits_to_set = BITS_PER_BYTE - (start % BITS_PER_BYTE);
5655 	u8 mask_to_set = BITMAP_FIRST_BYTE_MASK(start);
5656 
5657 	while (len - bits_to_set >= 0) {
5658 		*p |= mask_to_set;
5659 		len -= bits_to_set;
5660 		bits_to_set = BITS_PER_BYTE;
5661 		mask_to_set = ~0;
5662 		p++;
5663 	}
5664 	if (len) {
5665 		mask_to_set &= BITMAP_LAST_BYTE_MASK(size);
5666 		*p |= mask_to_set;
5667 	}
5668 }
5669 
5670 void le_bitmap_clear(u8 *map, unsigned int start, int len)
5671 {
5672 	u8 *p = map + BIT_BYTE(start);
5673 	const unsigned int size = start + len;
5674 	int bits_to_clear = BITS_PER_BYTE - (start % BITS_PER_BYTE);
5675 	u8 mask_to_clear = BITMAP_FIRST_BYTE_MASK(start);
5676 
5677 	while (len - bits_to_clear >= 0) {
5678 		*p &= ~mask_to_clear;
5679 		len -= bits_to_clear;
5680 		bits_to_clear = BITS_PER_BYTE;
5681 		mask_to_clear = ~0;
5682 		p++;
5683 	}
5684 	if (len) {
5685 		mask_to_clear &= BITMAP_LAST_BYTE_MASK(size);
5686 		*p &= ~mask_to_clear;
5687 	}
5688 }
5689 
5690 /*
5691  * eb_bitmap_offset() - calculate the page and offset of the byte containing the
5692  * given bit number
5693  * @eb: the extent buffer
5694  * @start: offset of the bitmap item in the extent buffer
5695  * @nr: bit number
5696  * @page_index: return index of the page in the extent buffer that contains the
5697  * given bit number
5698  * @page_offset: return offset into the page given by page_index
5699  *
5700  * This helper hides the ugliness of finding the byte in an extent buffer which
5701  * contains a given bit.
5702  */
5703 static inline void eb_bitmap_offset(struct extent_buffer *eb,
5704 				    unsigned long start, unsigned long nr,
5705 				    unsigned long *page_index,
5706 				    size_t *page_offset)
5707 {
5708 	size_t start_offset = eb->start & ((u64)PAGE_SIZE - 1);
5709 	size_t byte_offset = BIT_BYTE(nr);
5710 	size_t offset;
5711 
5712 	/*
5713 	 * The byte we want is the offset of the extent buffer + the offset of
5714 	 * the bitmap item in the extent buffer + the offset of the byte in the
5715 	 * bitmap item.
5716 	 */
5717 	offset = start_offset + start + byte_offset;
5718 
5719 	*page_index = offset >> PAGE_SHIFT;
5720 	*page_offset = offset & (PAGE_SIZE - 1);
5721 }
5722 
5723 /**
5724  * extent_buffer_test_bit - determine whether a bit in a bitmap item is set
5725  * @eb: the extent buffer
5726  * @start: offset of the bitmap item in the extent buffer
5727  * @nr: bit number to test
5728  */
5729 int extent_buffer_test_bit(struct extent_buffer *eb, unsigned long start,
5730 			   unsigned long nr)
5731 {
5732 	u8 *kaddr;
5733 	struct page *page;
5734 	unsigned long i;
5735 	size_t offset;
5736 
5737 	eb_bitmap_offset(eb, start, nr, &i, &offset);
5738 	page = eb->pages[i];
5739 	WARN_ON(!PageUptodate(page));
5740 	kaddr = page_address(page);
5741 	return 1U & (kaddr[offset] >> (nr & (BITS_PER_BYTE - 1)));
5742 }
5743 
5744 /**
5745  * extent_buffer_bitmap_set - set an area of a bitmap
5746  * @eb: the extent buffer
5747  * @start: offset of the bitmap item in the extent buffer
5748  * @pos: bit number of the first bit
5749  * @len: number of bits to set
5750  */
5751 void extent_buffer_bitmap_set(struct extent_buffer *eb, unsigned long start,
5752 			      unsigned long pos, unsigned long len)
5753 {
5754 	u8 *kaddr;
5755 	struct page *page;
5756 	unsigned long i;
5757 	size_t offset;
5758 	const unsigned int size = pos + len;
5759 	int bits_to_set = BITS_PER_BYTE - (pos % BITS_PER_BYTE);
5760 	u8 mask_to_set = BITMAP_FIRST_BYTE_MASK(pos);
5761 
5762 	eb_bitmap_offset(eb, start, pos, &i, &offset);
5763 	page = eb->pages[i];
5764 	WARN_ON(!PageUptodate(page));
5765 	kaddr = page_address(page);
5766 
5767 	while (len >= bits_to_set) {
5768 		kaddr[offset] |= mask_to_set;
5769 		len -= bits_to_set;
5770 		bits_to_set = BITS_PER_BYTE;
5771 		mask_to_set = ~0;
5772 		if (++offset >= PAGE_SIZE && len > 0) {
5773 			offset = 0;
5774 			page = eb->pages[++i];
5775 			WARN_ON(!PageUptodate(page));
5776 			kaddr = page_address(page);
5777 		}
5778 	}
5779 	if (len) {
5780 		mask_to_set &= BITMAP_LAST_BYTE_MASK(size);
5781 		kaddr[offset] |= mask_to_set;
5782 	}
5783 }
5784 
5785 
5786 /**
5787  * extent_buffer_bitmap_clear - clear an area of a bitmap
5788  * @eb: the extent buffer
5789  * @start: offset of the bitmap item in the extent buffer
5790  * @pos: bit number of the first bit
5791  * @len: number of bits to clear
5792  */
5793 void extent_buffer_bitmap_clear(struct extent_buffer *eb, unsigned long start,
5794 				unsigned long pos, unsigned long len)
5795 {
5796 	u8 *kaddr;
5797 	struct page *page;
5798 	unsigned long i;
5799 	size_t offset;
5800 	const unsigned int size = pos + len;
5801 	int bits_to_clear = BITS_PER_BYTE - (pos % BITS_PER_BYTE);
5802 	u8 mask_to_clear = BITMAP_FIRST_BYTE_MASK(pos);
5803 
5804 	eb_bitmap_offset(eb, start, pos, &i, &offset);
5805 	page = eb->pages[i];
5806 	WARN_ON(!PageUptodate(page));
5807 	kaddr = page_address(page);
5808 
5809 	while (len >= bits_to_clear) {
5810 		kaddr[offset] &= ~mask_to_clear;
5811 		len -= bits_to_clear;
5812 		bits_to_clear = BITS_PER_BYTE;
5813 		mask_to_clear = ~0;
5814 		if (++offset >= PAGE_SIZE && len > 0) {
5815 			offset = 0;
5816 			page = eb->pages[++i];
5817 			WARN_ON(!PageUptodate(page));
5818 			kaddr = page_address(page);
5819 		}
5820 	}
5821 	if (len) {
5822 		mask_to_clear &= BITMAP_LAST_BYTE_MASK(size);
5823 		kaddr[offset] &= ~mask_to_clear;
5824 	}
5825 }
5826 
5827 static inline bool areas_overlap(unsigned long src, unsigned long dst, unsigned long len)
5828 {
5829 	unsigned long distance = (src > dst) ? src - dst : dst - src;
5830 	return distance < len;
5831 }
5832 
5833 static void copy_pages(struct page *dst_page, struct page *src_page,
5834 		       unsigned long dst_off, unsigned long src_off,
5835 		       unsigned long len)
5836 {
5837 	char *dst_kaddr = page_address(dst_page);
5838 	char *src_kaddr;
5839 	int must_memmove = 0;
5840 
5841 	if (dst_page != src_page) {
5842 		src_kaddr = page_address(src_page);
5843 	} else {
5844 		src_kaddr = dst_kaddr;
5845 		if (areas_overlap(src_off, dst_off, len))
5846 			must_memmove = 1;
5847 	}
5848 
5849 	if (must_memmove)
5850 		memmove(dst_kaddr + dst_off, src_kaddr + src_off, len);
5851 	else
5852 		memcpy(dst_kaddr + dst_off, src_kaddr + src_off, len);
5853 }
5854 
5855 void memcpy_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
5856 			   unsigned long src_offset, unsigned long len)
5857 {
5858 	struct btrfs_fs_info *fs_info = dst->fs_info;
5859 	size_t cur;
5860 	size_t dst_off_in_page;
5861 	size_t src_off_in_page;
5862 	size_t start_offset = dst->start & ((u64)PAGE_SIZE - 1);
5863 	unsigned long dst_i;
5864 	unsigned long src_i;
5865 
5866 	if (src_offset + len > dst->len) {
5867 		btrfs_err(fs_info,
5868 			"memmove bogus src_offset %lu move len %lu dst len %lu",
5869 			 src_offset, len, dst->len);
5870 		BUG_ON(1);
5871 	}
5872 	if (dst_offset + len > dst->len) {
5873 		btrfs_err(fs_info,
5874 			"memmove bogus dst_offset %lu move len %lu dst len %lu",
5875 			 dst_offset, len, dst->len);
5876 		BUG_ON(1);
5877 	}
5878 
5879 	while (len > 0) {
5880 		dst_off_in_page = (start_offset + dst_offset) &
5881 			(PAGE_SIZE - 1);
5882 		src_off_in_page = (start_offset + src_offset) &
5883 			(PAGE_SIZE - 1);
5884 
5885 		dst_i = (start_offset + dst_offset) >> PAGE_SHIFT;
5886 		src_i = (start_offset + src_offset) >> PAGE_SHIFT;
5887 
5888 		cur = min(len, (unsigned long)(PAGE_SIZE -
5889 					       src_off_in_page));
5890 		cur = min_t(unsigned long, cur,
5891 			(unsigned long)(PAGE_SIZE - dst_off_in_page));
5892 
5893 		copy_pages(dst->pages[dst_i], dst->pages[src_i],
5894 			   dst_off_in_page, src_off_in_page, cur);
5895 
5896 		src_offset += cur;
5897 		dst_offset += cur;
5898 		len -= cur;
5899 	}
5900 }
5901 
5902 void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
5903 			   unsigned long src_offset, unsigned long len)
5904 {
5905 	struct btrfs_fs_info *fs_info = dst->fs_info;
5906 	size_t cur;
5907 	size_t dst_off_in_page;
5908 	size_t src_off_in_page;
5909 	unsigned long dst_end = dst_offset + len - 1;
5910 	unsigned long src_end = src_offset + len - 1;
5911 	size_t start_offset = dst->start & ((u64)PAGE_SIZE - 1);
5912 	unsigned long dst_i;
5913 	unsigned long src_i;
5914 
5915 	if (src_offset + len > dst->len) {
5916 		btrfs_err(fs_info,
5917 			  "memmove bogus src_offset %lu move len %lu len %lu",
5918 			  src_offset, len, dst->len);
5919 		BUG_ON(1);
5920 	}
5921 	if (dst_offset + len > dst->len) {
5922 		btrfs_err(fs_info,
5923 			  "memmove bogus dst_offset %lu move len %lu len %lu",
5924 			  dst_offset, len, dst->len);
5925 		BUG_ON(1);
5926 	}
5927 	if (dst_offset < src_offset) {
5928 		memcpy_extent_buffer(dst, dst_offset, src_offset, len);
5929 		return;
5930 	}
5931 	while (len > 0) {
5932 		dst_i = (start_offset + dst_end) >> PAGE_SHIFT;
5933 		src_i = (start_offset + src_end) >> PAGE_SHIFT;
5934 
5935 		dst_off_in_page = (start_offset + dst_end) &
5936 			(PAGE_SIZE - 1);
5937 		src_off_in_page = (start_offset + src_end) &
5938 			(PAGE_SIZE - 1);
5939 
5940 		cur = min_t(unsigned long, len, src_off_in_page + 1);
5941 		cur = min(cur, dst_off_in_page + 1);
5942 		copy_pages(dst->pages[dst_i], dst->pages[src_i],
5943 			   dst_off_in_page - cur + 1,
5944 			   src_off_in_page - cur + 1, cur);
5945 
5946 		dst_end -= cur;
5947 		src_end -= cur;
5948 		len -= cur;
5949 	}
5950 }
5951 
5952 int try_release_extent_buffer(struct page *page)
5953 {
5954 	struct extent_buffer *eb;
5955 
5956 	/*
5957 	 * We need to make sure nobody is attaching this page to an eb right
5958 	 * now.
5959 	 */
5960 	spin_lock(&page->mapping->private_lock);
5961 	if (!PagePrivate(page)) {
5962 		spin_unlock(&page->mapping->private_lock);
5963 		return 1;
5964 	}
5965 
5966 	eb = (struct extent_buffer *)page->private;
5967 	BUG_ON(!eb);
5968 
5969 	/*
5970 	 * This is a little awful but should be ok, we need to make sure that
5971 	 * the eb doesn't disappear out from under us while we're looking at
5972 	 * this page.
5973 	 */
5974 	spin_lock(&eb->refs_lock);
5975 	if (atomic_read(&eb->refs) != 1 || extent_buffer_under_io(eb)) {
5976 		spin_unlock(&eb->refs_lock);
5977 		spin_unlock(&page->mapping->private_lock);
5978 		return 0;
5979 	}
5980 	spin_unlock(&page->mapping->private_lock);
5981 
5982 	/*
5983 	 * If tree ref isn't set then we know the ref on this eb is a real ref,
5984 	 * so just return, this page will likely be freed soon anyway.
5985 	 */
5986 	if (!test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags)) {
5987 		spin_unlock(&eb->refs_lock);
5988 		return 0;
5989 	}
5990 
5991 	return release_extent_buffer(eb);
5992 }
5993