1	// SPDX-License-Identifier: GPL-2.0
2	/*
3	* Copyright (C) 2011 STRATO. All rights reserved.
4	*/
5
6	#include <linux/mm.h>
7	#include <linux/rbtree.h>
8	#include <trace/events/btrfs.h>
9	#include "ctree.h"
10	#include "disk-io.h"
11	#include "backref.h"
12	#include "ulist.h"
13	#include "transaction.h"
14	#include "delayed-ref.h"
15	#include "locking.h"
16	#include "misc.h"
17	#include "tree-mod-log.h"
18	#include "fs.h"
19	#include "accessors.h"
20	#include "extent-tree.h"
21	#include "relocation.h"
22	#include "tree-checker.h"
23
24	/* Just arbitrary numbers so we can be sure one of these happened. */
25	#define BACKREF_FOUND_SHARED 6
26	#define BACKREF_FOUND_NOT_SHARED 7
27
28	struct extent_inode_elem {
29	u64 inum;
30	u64 offset;
31	u64 num_bytes;
32	struct extent_inode_elem *next;
33	};
34
35	static int check_extent_in_eb(struct btrfs_backref_walk_ctx *ctx,
36	const struct btrfs_key *key,
37	const struct extent_buffer *eb,
38	const struct btrfs_file_extent_item *fi,
39	struct extent_inode_elem **eie)
40	{
41	const u64 data_len = btrfs_file_extent_num_bytes(eb, s: fi);
42	u64 offset = key->offset;
43	struct extent_inode_elem *e;
44	const u64 *root_ids;
45	int root_count;
46	bool cached;
47
48	if (!ctx->ignore_extent_item_pos &&
49	!btrfs_file_extent_compression(eb, s: fi) &&
50	!btrfs_file_extent_encryption(eb, s: fi) &&
51	!btrfs_file_extent_other_encoding(eb, s: fi)) {
52	u64 data_offset;
53
54	data_offset = btrfs_file_extent_offset(eb, s: fi);
55
56	if (ctx->extent_item_pos < data_offset ||
57	ctx->extent_item_pos >= data_offset + data_len)
58	return 1;
59	offset += ctx->extent_item_pos - data_offset;
60	}
61
62	if (!ctx->indirect_ref_iterator || !ctx->cache_lookup)
63	goto add_inode_elem;
64
65	cached = ctx->cache_lookup(eb->start, ctx->user_ctx, &root_ids,
66	&root_count);
67	if (!cached)
68	goto add_inode_elem;
69
70	for (int i = 0; i < root_count; i++) {
71	int ret;
72
73	ret = ctx->indirect_ref_iterator(key->objectid, offset,
74	data_len, root_ids[i],
75	ctx->user_ctx);
76	if (ret)
77	return ret;
78	}
79
80	add_inode_elem:
81	e = kmalloc(size: sizeof(*e), GFP_NOFS);
82	if (!e)
83	return -ENOMEM;
84
85	e->next = *eie;
86	e->inum = key->objectid;
87	e->offset = offset;
88	e->num_bytes = data_len;
89	*eie = e;
90
91	return 0;
92	}
93
94	static void free_inode_elem_list(struct extent_inode_elem *eie)
95	{
96	struct extent_inode_elem *eie_next;
97
98	for (; eie; eie = eie_next) {
99	eie_next = eie->next;
100	kfree(objp: eie);
101	}
102	}
103
104	static int find_extent_in_eb(struct btrfs_backref_walk_ctx *ctx,
105	const struct extent_buffer *eb,
106	struct extent_inode_elem **eie)
107	{
108	u64 disk_byte;
109	struct btrfs_key key;
110	struct btrfs_file_extent_item *fi;
111	int slot;
112	int nritems;
113	int extent_type;
114	int ret;
115
116	/*
117	* from the shared data ref, we only have the leaf but we need
118	* the key. thus, we must look into all items and see that we
119	* find one (some) with a reference to our extent item.
120	*/
121	nritems = btrfs_header_nritems(eb);
122	for (slot = 0; slot < nritems; ++slot) {
123	btrfs_item_key_to_cpu(eb, cpu_key: &key, nr: slot);
124	if (key.type != BTRFS_EXTENT_DATA_KEY)
125	continue;
126	fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
127	extent_type = btrfs_file_extent_type(eb, s: fi);
128	if (extent_type == BTRFS_FILE_EXTENT_INLINE)
129	continue;
130	/* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
131	disk_byte = btrfs_file_extent_disk_bytenr(eb, s: fi);
132	if (disk_byte != ctx->bytenr)
133	continue;
134
135	ret = check_extent_in_eb(ctx, key: &key, eb, fi, eie);
136	if (ret == BTRFS_ITERATE_EXTENT_INODES_STOP || ret < 0)
137	return ret;
138	}
139
140	return 0;
141	}
142
143	struct preftree {
144	struct rb_root_cached root;
145	unsigned int count;
146	};
147
148	#define PREFTREE_INIT { .root = RB_ROOT_CACHED, .count = 0 }
149
150	struct preftrees {
151	struct preftree direct; /* BTRFS_SHARED_[DATA|BLOCK]_REF_KEY */
152	struct preftree indirect; /* BTRFS_[TREE_BLOCK|EXTENT_DATA]_REF_KEY */
153	struct preftree indirect_missing_keys;
154	};
155
156	/*
157	* Checks for a shared extent during backref search.
158	*
159	* The share_count tracks prelim_refs (direct and indirect) having a
160	* ref->count >0:
161	* - incremented when a ref->count transitions to >0
162	* - decremented when a ref->count transitions to <1
163	*/
164	struct share_check {
165	struct btrfs_backref_share_check_ctx *ctx;
166	struct btrfs_root *root;
167	u64 inum;
168	u64 data_bytenr;
169	u64 data_extent_gen;
170	/*
171	* Counts number of inodes that refer to an extent (different inodes in
172	* the same root or different roots) that we could find. The sharedness
173	* check typically stops once this counter gets greater than 1, so it
174	* may not reflect the total number of inodes.
175	*/
176	int share_count;
177	/*
178	* The number of times we found our inode refers to the data extent we
179	* are determining the sharedness. In other words, how many file extent
180	* items we could find for our inode that point to our target data
181	* extent. The value we get here after finishing the extent sharedness
182	* check may be smaller than reality, but if it ends up being greater
183	* than 1, then we know for sure the inode has multiple file extent
184	* items that point to our inode, and we can safely assume it's useful
185	* to cache the sharedness check result.
186	*/
187	int self_ref_count;
188	bool have_delayed_delete_refs;
189	};
190
191	static inline int extent_is_shared(struct share_check *sc)
192	{
193	return (sc && sc->share_count > 1) ? BACKREF_FOUND_SHARED : 0;
194	}
195
196	static struct kmem_cache *btrfs_prelim_ref_cache;
197
198	int __init btrfs_prelim_ref_init(void)
199	{
200	btrfs_prelim_ref_cache = kmem_cache_create(name: "btrfs_prelim_ref",
201	size: sizeof(struct prelim_ref),
202	align: 0,
203	SLAB_MEM_SPREAD,
204	NULL);
205	if (!btrfs_prelim_ref_cache)
206	return -ENOMEM;
207	return 0;
208	}
209
210	void __cold btrfs_prelim_ref_exit(void)
211	{
212	kmem_cache_destroy(s: btrfs_prelim_ref_cache);
213	}
214
215	static void free_pref(struct prelim_ref *ref)
216	{
217	kmem_cache_free(s: btrfs_prelim_ref_cache, objp: ref);
218	}
219
220	/*
221	* Return 0 when both refs are for the same block (and can be merged).
222	* A -1 return indicates ref1 is a 'lower' block than ref2, while 1
223	* indicates a 'higher' block.
224	*/
225	static int prelim_ref_compare(struct prelim_ref *ref1,
226	struct prelim_ref *ref2)
227	{
228	if (ref1->level < ref2->level)
229	return -1;
230	if (ref1->level > ref2->level)
231	return 1;
232	if (ref1->root_id < ref2->root_id)
233	return -1;
234	if (ref1->root_id > ref2->root_id)
235	return 1;
236	if (ref1->key_for_search.type < ref2->key_for_search.type)
237	return -1;
238	if (ref1->key_for_search.type > ref2->key_for_search.type)
239	return 1;
240	if (ref1->key_for_search.objectid < ref2->key_for_search.objectid)
241	return -1;
242	if (ref1->key_for_search.objectid > ref2->key_for_search.objectid)
243	return 1;
244	if (ref1->key_for_search.offset < ref2->key_for_search.offset)
245	return -1;
246	if (ref1->key_for_search.offset > ref2->key_for_search.offset)
247	return 1;
248	if (ref1->parent < ref2->parent)
249	return -1;
250	if (ref1->parent > ref2->parent)
251	return 1;
252
253	return 0;
254	}
255
256	static void update_share_count(struct share_check *sc, int oldcount,
257	int newcount, struct prelim_ref *newref)
258	{
259	if ((!sc) || (oldcount == 0 && newcount < 1))
260	return;
261
262	if (oldcount > 0 && newcount < 1)
263	sc->share_count--;
264	else if (oldcount < 1 && newcount > 0)
265	sc->share_count++;
266
267	if (newref->root_id == sc->root->root_key.objectid &&
268	newref->wanted_disk_byte == sc->data_bytenr &&
269	newref->key_for_search.objectid == sc->inum)
270	sc->self_ref_count += newref->count;
271	}
272
273	/*
274	* Add @newref to the @root rbtree, merging identical refs.
275	*
276	* Callers should assume that newref has been freed after calling.
277	*/
278	static void prelim_ref_insert(const struct btrfs_fs_info *fs_info,
279	struct preftree *preftree,
280	struct prelim_ref *newref,
281	struct share_check *sc)
282	{
283	struct rb_root_cached *root;
284	struct rb_node **p;
285	struct rb_node *parent = NULL;
286	struct prelim_ref *ref;
287	int result;
288	bool leftmost = true;
289
290	root = &preftree->root;
291	p = &root->rb_root.rb_node;
292
293	while (*p) {
294	parent = *p;
295	ref = rb_entry(parent, struct prelim_ref, rbnode);
296	result = prelim_ref_compare(ref1: ref, ref2: newref);
297	if (result < 0) {
298	p = &(*p)->rb_left;
299	} else if (result > 0) {
300	p = &(*p)->rb_right;
301	leftmost = false;
302	} else {
303	/* Identical refs, merge them and free @newref */
304	struct extent_inode_elem *eie = ref->inode_list;
305
306	while (eie && eie->next)
307	eie = eie->next;
308
309	if (!eie)
310	ref->inode_list = newref->inode_list;
311	else
312	eie->next = newref->inode_list;
313	trace_btrfs_prelim_ref_merge(fs_info, oldref: ref, newref,
314	tree_size: preftree->count);
315	/*
316	* A delayed ref can have newref->count < 0.
317	* The ref->count is updated to follow any
318	* BTRFS_[ADD|DROP]_DELAYED_REF actions.
319	*/
320	update_share_count(sc, oldcount: ref->count,
321	newcount: ref->count + newref->count, newref);
322	ref->count += newref->count;
323	free_pref(ref: newref);
324	return;
325	}
326	}
327
328	update_share_count(sc, oldcount: 0, newcount: newref->count, newref);
329	preftree->count++;
330	trace_btrfs_prelim_ref_insert(fs_info, oldref: newref, NULL, tree_size: preftree->count);
331	rb_link_node(node: &newref->rbnode, parent, rb_link: p);
332	rb_insert_color_cached(node: &newref->rbnode, root, leftmost);
333	}
334
335	/*
336	* Release the entire tree. We don't care about internal consistency so
337	* just free everything and then reset the tree root.
338	*/
339	static void prelim_release(struct preftree *preftree)
340	{
341	struct prelim_ref *ref, *next_ref;
342
343	rbtree_postorder_for_each_entry_safe(ref, next_ref,
344	&preftree->root.rb_root, rbnode) {
345	free_inode_elem_list(eie: ref->inode_list);
346	free_pref(ref);
347	}
348
349	preftree->root = RB_ROOT_CACHED;
350	preftree->count = 0;
351	}
352
353	/*
354	* the rules for all callers of this function are:
355	* - obtaining the parent is the goal
356	* - if you add a key, you must know that it is a correct key
357	* - if you cannot add the parent or a correct key, then we will look into the
358	* block later to set a correct key
359	*
360	* delayed refs
361	* ============
362	* backref type | shared | indirect | shared | indirect
363	* information | tree | tree | data | data
364	* --------------------+--------+----------+--------+----------
365	* parent logical | y | - | - | -
366	* key to resolve | - | y | y | y
367	* tree block logical | - | - | - | -
368	* root for resolving | y | y | y | y
369	*
370	* - column 1: we've the parent -> done
371	* - column 2, 3, 4: we use the key to find the parent
372	*
373	* on disk refs (inline or keyed)
374	* ==============================
375	* backref type | shared | indirect | shared | indirect
376	* information | tree | tree | data | data
377	* --------------------+--------+----------+--------+----------
378	* parent logical | y | - | y | -
379	* key to resolve | - | - | - | y
380	* tree block logical | y | y | y | y
381	* root for resolving | - | y | y | y
382	*
383	* - column 1, 3: we've the parent -> done
384	* - column 2: we take the first key from the block to find the parent
385	* (see add_missing_keys)
386	* - column 4: we use the key to find the parent
387	*
388	* additional information that's available but not required to find the parent
389	* block might help in merging entries to gain some speed.
390	*/
391	static int add_prelim_ref(const struct btrfs_fs_info *fs_info,
392	struct preftree *preftree, u64 root_id,
393	const struct btrfs_key *key, int level, u64 parent,
394	u64 wanted_disk_byte, int count,
395	struct share_check *sc, gfp_t gfp_mask)
396	{
397	struct prelim_ref *ref;
398
399	if (root_id == BTRFS_DATA_RELOC_TREE_OBJECTID)
400	return 0;
401
402	ref = kmem_cache_alloc(cachep: btrfs_prelim_ref_cache, flags: gfp_mask);
403	if (!ref)
404	return -ENOMEM;
405
406	ref->root_id = root_id;
407	if (key)
408	ref->key_for_search = *key;
409	else
410	memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
411
412	ref->inode_list = NULL;
413	ref->level = level;
414	ref->count = count;
415	ref->parent = parent;
416	ref->wanted_disk_byte = wanted_disk_byte;
417	prelim_ref_insert(fs_info, preftree, newref: ref, sc);
418	return extent_is_shared(sc);
419	}
420
421	/* direct refs use root == 0, key == NULL */
422	static int add_direct_ref(const struct btrfs_fs_info *fs_info,
423	struct preftrees *preftrees, int level, u64 parent,
424	u64 wanted_disk_byte, int count,
425	struct share_check *sc, gfp_t gfp_mask)
426	{
427	return add_prelim_ref(fs_info, preftree: &preftrees->direct, root_id: 0, NULL, level,
428	parent, wanted_disk_byte, count, sc, gfp_mask);
429	}
430
431	/* indirect refs use parent == 0 */
432	static int add_indirect_ref(const struct btrfs_fs_info *fs_info,
433	struct preftrees *preftrees, u64 root_id,
434	const struct btrfs_key *key, int level,
435	u64 wanted_disk_byte, int count,
436	struct share_check *sc, gfp_t gfp_mask)
437	{
438	struct preftree *tree = &preftrees->indirect;
439
440	if (!key)
441	tree = &preftrees->indirect_missing_keys;
442	return add_prelim_ref(fs_info, preftree: tree, root_id, key, level, parent: 0,
443	wanted_disk_byte, count, sc, gfp_mask);
444	}
445
446	static int is_shared_data_backref(struct preftrees *preftrees, u64 bytenr)
447	{
448	struct rb_node **p = &preftrees->direct.root.rb_root.rb_node;
449	struct rb_node *parent = NULL;
450	struct prelim_ref *ref = NULL;
451	struct prelim_ref target = {};
452	int result;
453
454	target.parent = bytenr;
455
456	while (*p) {
457	parent = *p;
458	ref = rb_entry(parent, struct prelim_ref, rbnode);
459	result = prelim_ref_compare(ref1: ref, ref2: &target);
460
461	if (result < 0)
462	p = &(*p)->rb_left;
463	else if (result > 0)
464	p = &(*p)->rb_right;
465	else
466	return 1;
467	}
468	return 0;
469	}
470
471	static int add_all_parents(struct btrfs_backref_walk_ctx *ctx,
472	struct btrfs_root *root, struct btrfs_path *path,
473	struct ulist *parents,
474	struct preftrees *preftrees, struct prelim_ref *ref,
475	int level)
476	{
477	int ret = 0;
478	int slot;
479	struct extent_buffer *eb;
480	struct btrfs_key key;
481	struct btrfs_key *key_for_search = &ref->key_for_search;
482	struct btrfs_file_extent_item *fi;
483	struct extent_inode_elem *eie = NULL, *old = NULL;
484	u64 disk_byte;
485	u64 wanted_disk_byte = ref->wanted_disk_byte;
486	u64 count = 0;
487	u64 data_offset;
488	u8 type;
489
490	if (level != 0) {
491	eb = path->nodes[level];
492	ret = ulist_add(ulist: parents, val: eb->start, aux: 0, GFP_NOFS);
493	if (ret < 0)
494	return ret;
495	return 0;
496	}
497
498	/*
499	* 1. We normally enter this function with the path already pointing to
500	* the first item to check. But sometimes, we may enter it with
501	* slot == nritems.
502	* 2. We are searching for normal backref but bytenr of this leaf
503	* matches shared data backref
504	* 3. The leaf owner is not equal to the root we are searching
505	*
506	* For these cases, go to the next leaf before we continue.
507	*/
508	eb = path->nodes[0];
509	if (path->slots[0] >= btrfs_header_nritems(eb) ||
510	is_shared_data_backref(preftrees, bytenr: eb->start) ||
511	ref->root_id != btrfs_header_owner(eb)) {
512	if (ctx->time_seq == BTRFS_SEQ_LAST)
513	ret = btrfs_next_leaf(root, path);
514	else
515	ret = btrfs_next_old_leaf(root, path, time_seq: ctx->time_seq);
516	}
517
518	while (!ret && count < ref->count) {
519	eb = path->nodes[0];
520	slot = path->slots[0];
521
522	btrfs_item_key_to_cpu(eb, cpu_key: &key, nr: slot);
523
524	if (key.objectid != key_for_search->objectid ||
525	key.type != BTRFS_EXTENT_DATA_KEY)
526	break;
527
528	/*
529	* We are searching for normal backref but bytenr of this leaf
530	* matches shared data backref, OR
531	* the leaf owner is not equal to the root we are searching for
532	*/
533	if (slot == 0 &&
534	(is_shared_data_backref(preftrees, bytenr: eb->start) ||
535	ref->root_id != btrfs_header_owner(eb))) {
536	if (ctx->time_seq == BTRFS_SEQ_LAST)
537	ret = btrfs_next_leaf(root, path);
538	else
539	ret = btrfs_next_old_leaf(root, path, time_seq: ctx->time_seq);
540	continue;
541	}
542	fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
543	type = btrfs_file_extent_type(eb, s: fi);
544	if (type == BTRFS_FILE_EXTENT_INLINE)
545	goto next;
546	disk_byte = btrfs_file_extent_disk_bytenr(eb, s: fi);
547	data_offset = btrfs_file_extent_offset(eb, s: fi);
548
549	if (disk_byte == wanted_disk_byte) {
550	eie = NULL;
551	old = NULL;
552	if (ref->key_for_search.offset == key.offset - data_offset)
553	count++;
554	else
555	goto next;
556	if (!ctx->skip_inode_ref_list) {
557	ret = check_extent_in_eb(ctx, key: &key, eb, fi, eie: &eie);
558	if (ret == BTRFS_ITERATE_EXTENT_INODES_STOP ||
559	ret < 0)
560	break;
561	}
562	if (ret > 0)
563	goto next;
564	ret = ulist_add_merge_ptr(ulist: parents, val: eb->start,
565	aux: eie, old_aux: (void **)&old, GFP_NOFS);
566	if (ret < 0)
567	break;
568	if (!ret && !ctx->skip_inode_ref_list) {
569	while (old->next)
570	old = old->next;
571	old->next = eie;
572	}
573	eie = NULL;
574	}
575	next:
576	if (ctx->time_seq == BTRFS_SEQ_LAST)
577	ret = btrfs_next_item(root, p: path);
578	else
579	ret = btrfs_next_old_item(root, path, time_seq: ctx->time_seq);
580	}
581
582	if (ret == BTRFS_ITERATE_EXTENT_INODES_STOP || ret < 0)
583	free_inode_elem_list(eie);
584	else if (ret > 0)
585	ret = 0;
586
587	return ret;
588	}
589
590	/*
591	* resolve an indirect backref in the form (root_id, key, level)
592	* to a logical address
593	*/
594	static int resolve_indirect_ref(struct btrfs_backref_walk_ctx *ctx,
595	struct btrfs_path *path,
596	struct preftrees *preftrees,
597	struct prelim_ref *ref, struct ulist *parents)
598	{
599	struct btrfs_root *root;
600	struct extent_buffer *eb;
601	int ret = 0;
602	int root_level;
603	int level = ref->level;
604	struct btrfs_key search_key = ref->key_for_search;
605
606	/*
607	* If we're search_commit_root we could possibly be holding locks on
608	* other tree nodes. This happens when qgroups does backref walks when
609	* adding new delayed refs. To deal with this we need to look in cache
610	* for the root, and if we don't find it then we need to search the
611	* tree_root's commit root, thus the btrfs_get_fs_root_commit_root usage
612	* here.
613	*/
614	if (path->search_commit_root)
615	root = btrfs_get_fs_root_commit_root(fs_info: ctx->fs_info, path, objectid: ref->root_id);
616	else
617	root = btrfs_get_fs_root(fs_info: ctx->fs_info, objectid: ref->root_id, check_ref: false);
618	if (IS_ERR(ptr: root)) {
619	ret = PTR_ERR(ptr: root);
620	goto out_free;
621	}
622
623	if (!path->search_commit_root &&
624	test_bit(BTRFS_ROOT_DELETING, &root->state)) {
625	ret = -ENOENT;
626	goto out;
627	}
628
629	if (btrfs_is_testing(fs_info: ctx->fs_info)) {
630	ret = -ENOENT;
631	goto out;
632	}
633
634	if (path->search_commit_root)
635	root_level = btrfs_header_level(eb: root->commit_root);
636	else if (ctx->time_seq == BTRFS_SEQ_LAST)
637	root_level = btrfs_header_level(eb: root->node);
638	else
639	root_level = btrfs_old_root_level(root, time_seq: ctx->time_seq);
640
641	if (root_level + 1 == level)
642	goto out;
643
644	/*
645	* We can often find data backrefs with an offset that is too large
646	* (>= LLONG_MAX, maximum allowed file offset) due to underflows when
647	* subtracting a file's offset with the data offset of its
648	* corresponding extent data item. This can happen for example in the
649	* clone ioctl.
650	*
651	* So if we detect such case we set the search key's offset to zero to
652	* make sure we will find the matching file extent item at
653	* add_all_parents(), otherwise we will miss it because the offset
654	* taken form the backref is much larger then the offset of the file
655	* extent item. This can make us scan a very large number of file
656	* extent items, but at least it will not make us miss any.
657	*
658	* This is an ugly workaround for a behaviour that should have never
659	* existed, but it does and a fix for the clone ioctl would touch a lot
660	* of places, cause backwards incompatibility and would not fix the
661	* problem for extents cloned with older kernels.
662	*/
663	if (search_key.type == BTRFS_EXTENT_DATA_KEY &&
664	search_key.offset >= LLONG_MAX)
665	search_key.offset = 0;
666	path->lowest_level = level;
667	if (ctx->time_seq == BTRFS_SEQ_LAST)
668	ret = btrfs_search_slot(NULL, root, key: &search_key, p: path, ins_len: 0, cow: 0);
669	else
670	ret = btrfs_search_old_slot(root, key: &search_key, p: path, time_seq: ctx->time_seq);
671
672	btrfs_debug(ctx->fs_info,
673	"search slot in root %llu (level %d, ref count %d) returned %d for key (%llu %u %llu)",
674	ref->root_id, level, ref->count, ret,
675	ref->key_for_search.objectid, ref->key_for_search.type,
676	ref->key_for_search.offset);
677	if (ret < 0)
678	goto out;
679
680	eb = path->nodes[level];
681	while (!eb) {
682	if (WARN_ON(!level)) {
683	ret = 1;
684	goto out;
685	}
686	level--;
687	eb = path->nodes[level];
688	}
689
690	ret = add_all_parents(ctx, root, path, parents, preftrees, ref, level);
691	out:
692	btrfs_put_root(root);
693	out_free:
694	path->lowest_level = 0;
695	btrfs_release_path(p: path);
696	return ret;
697	}
698
699	static struct extent_inode_elem *
700	unode_aux_to_inode_list(struct ulist_node *node)
701	{
702	if (!node)
703	return NULL;
704	return (struct extent_inode_elem *)(uintptr_t)node->aux;
705	}
706
707	static void free_leaf_list(struct ulist *ulist)
708	{
709	struct ulist_node *node;
710	struct ulist_iterator uiter;
711
712	ULIST_ITER_INIT(&uiter);
713	while ((node = ulist_next(ulist, uiter: &uiter)))
714	free_inode_elem_list(eie: unode_aux_to_inode_list(node));
715
716	ulist_free(ulist);
717	}
718
719	/*
720	* We maintain three separate rbtrees: one for direct refs, one for
721	* indirect refs which have a key, and one for indirect refs which do not
722	* have a key. Each tree does merge on insertion.
723	*
724	* Once all of the references are located, we iterate over the tree of
725	* indirect refs with missing keys. An appropriate key is located and
726	* the ref is moved onto the tree for indirect refs. After all missing
727	* keys are thus located, we iterate over the indirect ref tree, resolve
728	* each reference, and then insert the resolved reference onto the
729	* direct tree (merging there too).
730	*
731	* New backrefs (i.e., for parent nodes) are added to the appropriate
732	* rbtree as they are encountered. The new backrefs are subsequently
733	* resolved as above.
734	*/
735	static int resolve_indirect_refs(struct btrfs_backref_walk_ctx *ctx,
736	struct btrfs_path *path,
737	struct preftrees *preftrees,
738	struct share_check *sc)
739	{
740	int err;
741	int ret = 0;
742	struct ulist *parents;
743	struct ulist_node *node;
744	struct ulist_iterator uiter;
745	struct rb_node *rnode;
746
747	parents = ulist_alloc(GFP_NOFS);
748	if (!parents)
749	return -ENOMEM;
750
751	/*
752	* We could trade memory usage for performance here by iterating
753	* the tree, allocating new refs for each insertion, and then
754	* freeing the entire indirect tree when we're done. In some test
755	* cases, the tree can grow quite large (~200k objects).
756	*/
757	while ((rnode = rb_first_cached(&preftrees->indirect.root))) {
758	struct prelim_ref *ref;
759
760	ref = rb_entry(rnode, struct prelim_ref, rbnode);
761	if (WARN(ref->parent,
762	"BUG: direct ref found in indirect tree")) {
763	ret = -EINVAL;
764	goto out;
765	}
766
767	rb_erase_cached(node: &ref->rbnode, root: &preftrees->indirect.root);
768	preftrees->indirect.count--;
769
770	if (ref->count == 0) {
771	free_pref(ref);
772	continue;
773	}
774
775	if (sc && ref->root_id != sc->root->root_key.objectid) {
776	free_pref(ref);
777	ret = BACKREF_FOUND_SHARED;
778	goto out;
779	}
780	err = resolve_indirect_ref(ctx, path, preftrees, ref, parents);
781	/*
782	* we can only tolerate ENOENT,otherwise,we should catch error
783	* and return directly.
784	*/
785	if (err == -ENOENT) {
786	prelim_ref_insert(fs_info: ctx->fs_info, preftree: &preftrees->direct, newref: ref,
787	NULL);
788	continue;
789	} else if (err) {
790	free_pref(ref);
791	ret = err;
792	goto out;
793	}
794
795	/* we put the first parent into the ref at hand */
796	ULIST_ITER_INIT(&uiter);
797	node = ulist_next(ulist: parents, uiter: &uiter);
798	ref->parent = node ? node->val : 0;
799	ref->inode_list = unode_aux_to_inode_list(node);
800
801	/* Add a prelim_ref(s) for any other parent(s). */
802	while ((node = ulist_next(ulist: parents, uiter: &uiter))) {
803	struct prelim_ref *new_ref;
804
805	new_ref = kmem_cache_alloc(cachep: btrfs_prelim_ref_cache,
806	GFP_NOFS);
807	if (!new_ref) {
808	free_pref(ref);
809	ret = -ENOMEM;
810	goto out;
811	}
812	memcpy(new_ref, ref, sizeof(*ref));
813	new_ref->parent = node->val;
814	new_ref->inode_list = unode_aux_to_inode_list(node);
815	prelim_ref_insert(fs_info: ctx->fs_info, preftree: &preftrees->direct,
816	newref: new_ref, NULL);
817	}
818
819	/*
820	* Now it's a direct ref, put it in the direct tree. We must
821	* do this last because the ref could be merged/freed here.
822	*/
823	prelim_ref_insert(fs_info: ctx->fs_info, preftree: &preftrees->direct, newref: ref, NULL);
824
825	ulist_reinit(ulist: parents);
826	cond_resched();
827	}
828	out:
829	/*
830	* We may have inode lists attached to refs in the parents ulist, so we
831	* must free them before freeing the ulist and its refs.
832	*/
833	free_leaf_list(ulist: parents);
834	return ret;
835	}
836
837	/*
838	* read tree blocks and add keys where required.
839	*/
840	static int add_missing_keys(struct btrfs_fs_info *fs_info,
841	struct preftrees *preftrees, bool lock)
842	{
843	struct prelim_ref *ref;
844	struct extent_buffer *eb;
845	struct preftree *tree = &preftrees->indirect_missing_keys;
846	struct rb_node *node;
847
848	while ((node = rb_first_cached(&tree->root))) {
849	struct btrfs_tree_parent_check check = { 0 };
850
851	ref = rb_entry(node, struct prelim_ref, rbnode);
852	rb_erase_cached(node, root: &tree->root);
853
854	BUG_ON(ref->parent); /* should not be a direct ref */
855	BUG_ON(ref->key_for_search.type);
856	BUG_ON(!ref->wanted_disk_byte);
857
858	check.level = ref->level - 1;
859	check.owner_root = ref->root_id;
860
861	eb = read_tree_block(fs_info, bytenr: ref->wanted_disk_byte, check: &check);
862	if (IS_ERR(ptr: eb)) {
863	free_pref(ref);
864	return PTR_ERR(ptr: eb);
865	}
866	if (!extent_buffer_uptodate(eb)) {
867	free_pref(ref);
868	free_extent_buffer(eb);
869	return -EIO;
870	}
871
872	if (lock)
873	btrfs_tree_read_lock(eb);
874	if (btrfs_header_level(eb) == 0)
875	btrfs_item_key_to_cpu(eb, cpu_key: &ref->key_for_search, nr: 0);
876	else
877	btrfs_node_key_to_cpu(eb, cpu_key: &ref->key_for_search, nr: 0);
878	if (lock)
879	btrfs_tree_read_unlock(eb);
880	free_extent_buffer(eb);
881	prelim_ref_insert(fs_info, preftree: &preftrees->indirect, newref: ref, NULL);
882	cond_resched();
883	}
884	return 0;
885	}
886
887	/*
888	* add all currently queued delayed refs from this head whose seq nr is
889	* smaller or equal that seq to the list
890	*/
891	static int add_delayed_refs(const struct btrfs_fs_info *fs_info,
892	struct btrfs_delayed_ref_head *head, u64 seq,
893	struct preftrees *preftrees, struct share_check *sc)
894	{
895	struct btrfs_delayed_ref_node *node;
896	struct btrfs_key key;
897	struct rb_node *n;
898	int count;
899	int ret = 0;
900
901	spin_lock(lock: &head->lock);
902	for (n = rb_first_cached(&head->ref_tree); n; n = rb_next(n)) {
903	node = rb_entry(n, struct btrfs_delayed_ref_node,
904	ref_node);
905	if (node->seq > seq)
906	continue;
907
908	switch (node->action) {
909	case BTRFS_ADD_DELAYED_EXTENT:
910	case BTRFS_UPDATE_DELAYED_HEAD:
911	WARN_ON(1);
912	continue;
913	case BTRFS_ADD_DELAYED_REF:
914	count = node->ref_mod;
915	break;
916	case BTRFS_DROP_DELAYED_REF:
917	count = node->ref_mod * -1;
918	break;
919	default:
920	BUG();
921	}
922	switch (node->type) {
923	case BTRFS_TREE_BLOCK_REF_KEY: {
924	/* NORMAL INDIRECT METADATA backref */
925	struct btrfs_delayed_tree_ref *ref;
926	struct btrfs_key *key_ptr = NULL;
927
928	if (head->extent_op && head->extent_op->update_key) {
929	btrfs_disk_key_to_cpu(cpu_key: &key, disk_key: &head->extent_op->key);
930	key_ptr = &key;
931	}
932
933	ref = btrfs_delayed_node_to_tree_ref(node);
934	ret = add_indirect_ref(fs_info, preftrees, root_id: ref->root,
935	key: key_ptr, level: ref->level + 1,
936	wanted_disk_byte: node->bytenr, count, sc,
937	GFP_ATOMIC);
938	break;
939	}
940	case BTRFS_SHARED_BLOCK_REF_KEY: {
941	/* SHARED DIRECT METADATA backref */
942	struct btrfs_delayed_tree_ref *ref;
943
944	ref = btrfs_delayed_node_to_tree_ref(node);
945
946	ret = add_direct_ref(fs_info, preftrees, level: ref->level + 1,
947	parent: ref->parent, wanted_disk_byte: node->bytenr, count,
948	sc, GFP_ATOMIC);
949	break;
950	}
951	case BTRFS_EXTENT_DATA_REF_KEY: {
952	/* NORMAL INDIRECT DATA backref */
953	struct btrfs_delayed_data_ref *ref;
954	ref = btrfs_delayed_node_to_data_ref(node);
955
956	key.objectid = ref->objectid;
957	key.type = BTRFS_EXTENT_DATA_KEY;
958	key.offset = ref->offset;
959
960	/*
961	* If we have a share check context and a reference for
962	* another inode, we can't exit immediately. This is
963	* because even if this is a BTRFS_ADD_DELAYED_REF
964	* reference we may find next a BTRFS_DROP_DELAYED_REF
965	* which cancels out this ADD reference.
966	*
967	* If this is a DROP reference and there was no previous
968	* ADD reference, then we need to signal that when we
969	* process references from the extent tree (through
970	* add_inline_refs() and add_keyed_refs()), we should
971	* not exit early if we find a reference for another
972	* inode, because one of the delayed DROP references
973	* may cancel that reference in the extent tree.
974	*/
975	if (sc && count < 0)
976	sc->have_delayed_delete_refs = true;
977
978	ret = add_indirect_ref(fs_info, preftrees, root_id: ref->root,
979	key: &key, level: 0, wanted_disk_byte: node->bytenr, count, sc,
980	GFP_ATOMIC);
981	break;
982	}
983	case BTRFS_SHARED_DATA_REF_KEY: {
984	/* SHARED DIRECT FULL backref */
985	struct btrfs_delayed_data_ref *ref;
986
987	ref = btrfs_delayed_node_to_data_ref(node);
988
989	ret = add_direct_ref(fs_info, preftrees, level: 0, parent: ref->parent,
990	wanted_disk_byte: node->bytenr, count, sc,
991	GFP_ATOMIC);
992	break;
993	}
994	default:
995	WARN_ON(1);
996	}
997	/*
998	* We must ignore BACKREF_FOUND_SHARED until all delayed
999	* refs have been checked.
1000	*/
1001	if (ret && (ret != BACKREF_FOUND_SHARED))
1002	break;
1003	}
1004	if (!ret)
1005	ret = extent_is_shared(sc);
1006
1007	spin_unlock(lock: &head->lock);
1008	return ret;
1009	}
1010
1011	/*
1012	* add all inline backrefs for bytenr to the list
1013	*
1014	* Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
1015	*/
1016	static int add_inline_refs(struct btrfs_backref_walk_ctx *ctx,
1017	struct btrfs_path *path,
1018	int *info_level, struct preftrees *preftrees,
1019	struct share_check *sc)
1020	{
1021	int ret = 0;
1022	int slot;
1023	struct extent_buffer *leaf;
1024	struct btrfs_key key;
1025	struct btrfs_key found_key;
1026	unsigned long ptr;
1027	unsigned long end;
1028	struct btrfs_extent_item *ei;
1029	u64 flags;
1030	u64 item_size;
1031
1032	/*
1033	* enumerate all inline refs
1034	*/
1035	leaf = path->nodes[0];
1036	slot = path->slots[0];
1037
1038	item_size = btrfs_item_size(eb: leaf, slot);
1039	BUG_ON(item_size < sizeof(*ei));
1040
1041	ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
1042
1043	if (ctx->check_extent_item) {
1044	ret = ctx->check_extent_item(ctx->bytenr, ei, leaf, ctx->user_ctx);
1045	if (ret)
1046	return ret;
1047	}
1048
1049	flags = btrfs_extent_flags(eb: leaf, s: ei);
1050	btrfs_item_key_to_cpu(eb: leaf, cpu_key: &found_key, nr: slot);
1051
1052	ptr = (unsigned long)(ei + 1);
1053	end = (unsigned long)ei + item_size;
1054
1055	if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
1056	flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1057	struct btrfs_tree_block_info *info;
1058
1059	info = (struct btrfs_tree_block_info *)ptr;
1060	*info_level = btrfs_tree_block_level(eb: leaf, s: info);
1061	ptr += sizeof(struct btrfs_tree_block_info);
1062	BUG_ON(ptr > end);
1063	} else if (found_key.type == BTRFS_METADATA_ITEM_KEY) {
1064	*info_level = found_key.offset;
1065	} else {
1066	BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
1067	}
1068
1069	while (ptr < end) {
1070	struct btrfs_extent_inline_ref *iref;
1071	u64 offset;
1072	int type;
1073
1074	iref = (struct btrfs_extent_inline_ref *)ptr;
1075	type = btrfs_get_extent_inline_ref_type(eb: leaf, iref,
1076	is_data: BTRFS_REF_TYPE_ANY);
1077	if (type == BTRFS_REF_TYPE_INVALID)
1078	return -EUCLEAN;
1079
1080	offset = btrfs_extent_inline_ref_offset(eb: leaf, s: iref);
1081
1082	switch (type) {
1083	case BTRFS_SHARED_BLOCK_REF_KEY:
1084	ret = add_direct_ref(fs_info: ctx->fs_info, preftrees,
1085	level: *info_level + 1, parent: offset,
1086	wanted_disk_byte: ctx->bytenr, count: 1, NULL, GFP_NOFS);
1087	break;
1088	case BTRFS_SHARED_DATA_REF_KEY: {
1089	struct btrfs_shared_data_ref *sdref;
1090	int count;
1091
1092	sdref = (struct btrfs_shared_data_ref *)(iref + 1);
1093	count = btrfs_shared_data_ref_count(eb: leaf, s: sdref);
1094
1095	ret = add_direct_ref(fs_info: ctx->fs_info, preftrees, level: 0, parent: offset,
1096	wanted_disk_byte: ctx->bytenr, count, sc, GFP_NOFS);
1097	break;
1098	}
1099	case BTRFS_TREE_BLOCK_REF_KEY:
1100	ret = add_indirect_ref(fs_info: ctx->fs_info, preftrees, root_id: offset,
1101	NULL, level: *info_level + 1,
1102	wanted_disk_byte: ctx->bytenr, count: 1, NULL, GFP_NOFS);
1103	break;
1104	case BTRFS_EXTENT_DATA_REF_KEY: {
1105	struct btrfs_extent_data_ref *dref;
1106	int count;
1107	u64 root;
1108
1109	dref = (struct btrfs_extent_data_ref *)(&iref->offset);
1110	count = btrfs_extent_data_ref_count(eb: leaf, s: dref);
1111	key.objectid = btrfs_extent_data_ref_objectid(eb: leaf,
1112	s: dref);
1113	key.type = BTRFS_EXTENT_DATA_KEY;
1114	key.offset = btrfs_extent_data_ref_offset(eb: leaf, s: dref);
1115
1116	if (sc && key.objectid != sc->inum &&
1117	!sc->have_delayed_delete_refs) {
1118	ret = BACKREF_FOUND_SHARED;
1119	break;
1120	}
1121
1122	root = btrfs_extent_data_ref_root(eb: leaf, s: dref);
1123
1124	if (!ctx->skip_data_ref ||
1125	!ctx->skip_data_ref(root, key.objectid, key.offset,
1126	ctx->user_ctx))
1127	ret = add_indirect_ref(fs_info: ctx->fs_info, preftrees,
1128	root_id: root, key: &key, level: 0, wanted_disk_byte: ctx->bytenr,
1129	count, sc, GFP_NOFS);
1130	break;
1131	}
1132	case BTRFS_EXTENT_OWNER_REF_KEY:
1133	ASSERT(btrfs_fs_incompat(ctx->fs_info, SIMPLE_QUOTA));
1134	break;
1135	default:
1136	WARN_ON(1);
1137	}
1138	if (ret)
1139	return ret;
1140	ptr += btrfs_extent_inline_ref_size(type);
1141	}
1142
1143	return 0;
1144	}
1145
1146	/*
1147	* add all non-inline backrefs for bytenr to the list
1148	*
1149	* Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
1150	*/
1151	static int add_keyed_refs(struct btrfs_backref_walk_ctx *ctx,
1152	struct btrfs_root *extent_root,
1153	struct btrfs_path *path,
1154	int info_level, struct preftrees *preftrees,
1155	struct share_check *sc)
1156	{
1157	struct btrfs_fs_info *fs_info = extent_root->fs_info;
1158	int ret;
1159	int slot;
1160	struct extent_buffer *leaf;
1161	struct btrfs_key key;
1162
1163	while (1) {
1164	ret = btrfs_next_item(root: extent_root, p: path);
1165	if (ret < 0)
1166	break;
1167	if (ret) {
1168	ret = 0;
1169	break;
1170	}
1171
1172	slot = path->slots[0];
1173	leaf = path->nodes[0];
1174	btrfs_item_key_to_cpu(eb: leaf, cpu_key: &key, nr: slot);
1175
1176	if (key.objectid != ctx->bytenr)
1177	break;
1178	if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
1179	continue;
1180	if (key.type > BTRFS_SHARED_DATA_REF_KEY)
1181	break;
1182
1183	switch (key.type) {
1184	case BTRFS_SHARED_BLOCK_REF_KEY:
1185	/* SHARED DIRECT METADATA backref */
1186	ret = add_direct_ref(fs_info, preftrees,
1187	level: info_level + 1, parent: key.offset,
1188	wanted_disk_byte: ctx->bytenr, count: 1, NULL, GFP_NOFS);
1189	break;
1190	case BTRFS_SHARED_DATA_REF_KEY: {
1191	/* SHARED DIRECT FULL backref */
1192	struct btrfs_shared_data_ref *sdref;
1193	int count;
1194
1195	sdref = btrfs_item_ptr(leaf, slot,
1196	struct btrfs_shared_data_ref);
1197	count = btrfs_shared_data_ref_count(eb: leaf, s: sdref);
1198	ret = add_direct_ref(fs_info, preftrees, level: 0,
1199	parent: key.offset, wanted_disk_byte: ctx->bytenr, count,
1200	sc, GFP_NOFS);
1201	break;
1202	}
1203	case BTRFS_TREE_BLOCK_REF_KEY:
1204	/* NORMAL INDIRECT METADATA backref */
1205	ret = add_indirect_ref(fs_info, preftrees, root_id: key.offset,
1206	NULL, level: info_level + 1, wanted_disk_byte: ctx->bytenr,
1207	count: 1, NULL, GFP_NOFS);
1208	break;
1209	case BTRFS_EXTENT_DATA_REF_KEY: {
1210	/* NORMAL INDIRECT DATA backref */
1211	struct btrfs_extent_data_ref *dref;
1212	int count;
1213	u64 root;
1214
1215	dref = btrfs_item_ptr(leaf, slot,
1216	struct btrfs_extent_data_ref);
1217	count = btrfs_extent_data_ref_count(eb: leaf, s: dref);
1218	key.objectid = btrfs_extent_data_ref_objectid(eb: leaf,
1219	s: dref);
1220	key.type = BTRFS_EXTENT_DATA_KEY;
1221	key.offset = btrfs_extent_data_ref_offset(eb: leaf, s: dref);
1222
1223	if (sc && key.objectid != sc->inum &&
1224	!sc->have_delayed_delete_refs) {
1225	ret = BACKREF_FOUND_SHARED;
1226	break;
1227	}
1228
1229	root = btrfs_extent_data_ref_root(eb: leaf, s: dref);
1230
1231	if (!ctx->skip_data_ref ||
1232	!ctx->skip_data_ref(root, key.objectid, key.offset,
1233	ctx->user_ctx))
1234	ret = add_indirect_ref(fs_info, preftrees, root_id: root,
1235	key: &key, level: 0, wanted_disk_byte: ctx->bytenr,
1236	count, sc, GFP_NOFS);
1237	break;
1238	}
1239	default:
1240	WARN_ON(1);
1241	}
1242	if (ret)
1243	return ret;
1244
1245	}
1246
1247	return ret;
1248	}
1249
1250	/*
1251	* The caller has joined a transaction or is holding a read lock on the
1252	* fs_info->commit_root_sem semaphore, so no need to worry about the root's last
1253	* snapshot field changing while updating or checking the cache.
1254	*/
1255	static bool lookup_backref_shared_cache(struct btrfs_backref_share_check_ctx *ctx,
1256	struct btrfs_root *root,
1257	u64 bytenr, int level, bool *is_shared)
1258	{
1259	const struct btrfs_fs_info *fs_info = root->fs_info;
1260	struct btrfs_backref_shared_cache_entry *entry;
1261
1262	if (!current->journal_info)
1263	lockdep_assert_held(&fs_info->commit_root_sem);
1264
1265	if (!ctx->use_path_cache)
1266	return false;
1267
1268	if (WARN_ON_ONCE(level >= BTRFS_MAX_LEVEL))
1269	return false;
1270
1271	/*
1272	* Level -1 is used for the data extent, which is not reliable to cache
1273	* because its reference count can increase or decrease without us
1274	* realizing. We cache results only for extent buffers that lead from
1275	* the root node down to the leaf with the file extent item.
1276	*/
1277	ASSERT(level >= 0);
1278
1279	entry = &ctx->path_cache_entries[level];
1280
1281	/* Unused cache entry or being used for some other extent buffer. */
1282	if (entry->bytenr != bytenr)
1283	return false;
1284
1285	/*
1286	* We cached a false result, but the last snapshot generation of the
1287	* root changed, so we now have a snapshot. Don't trust the result.
1288	*/
1289	if (!entry->is_shared &&
1290	entry->gen != btrfs_root_last_snapshot(s: &root->root_item))
1291	return false;
1292
1293	/*
1294	* If we cached a true result and the last generation used for dropping
1295	* a root changed, we can not trust the result, because the dropped root
1296	* could be a snapshot sharing this extent buffer.
1297	*/
1298	if (entry->is_shared &&
1299	entry->gen != btrfs_get_last_root_drop_gen(fs_info))
1300	return false;
1301
1302	*is_shared = entry->is_shared;
1303	/*
1304	* If the node at this level is shared, than all nodes below are also
1305	* shared. Currently some of the nodes below may be marked as not shared
1306	* because we have just switched from one leaf to another, and switched
1307	* also other nodes above the leaf and below the current level, so mark
1308	* them as shared.
1309	*/
1310	if (*is_shared) {
1311	for (int i = 0; i < level; i++) {
1312	ctx->path_cache_entries[i].is_shared = true;
1313	ctx->path_cache_entries[i].gen = entry->gen;
1314	}
1315	}
1316
1317	return true;
1318	}
1319
1320	/*
1321	* The caller has joined a transaction or is holding a read lock on the
1322	* fs_info->commit_root_sem semaphore, so no need to worry about the root's last
1323	* snapshot field changing while updating or checking the cache.
1324	*/
1325	static void store_backref_shared_cache(struct btrfs_backref_share_check_ctx *ctx,
1326	struct btrfs_root *root,
1327	u64 bytenr, int level, bool is_shared)
1328	{
1329	const struct btrfs_fs_info *fs_info = root->fs_info;
1330	struct btrfs_backref_shared_cache_entry *entry;
1331	u64 gen;
1332
1333	if (!current->journal_info)
1334	lockdep_assert_held(&fs_info->commit_root_sem);
1335
1336	if (!ctx->use_path_cache)
1337	return;
1338
1339	if (WARN_ON_ONCE(level >= BTRFS_MAX_LEVEL))
1340	return;
1341
1342	/*
1343	* Level -1 is used for the data extent, which is not reliable to cache
1344	* because its reference count can increase or decrease without us
1345	* realizing. We cache results only for extent buffers that lead from
1346	* the root node down to the leaf with the file extent item.
1347	*/
1348	ASSERT(level >= 0);
1349
1350	if (is_shared)
1351	gen = btrfs_get_last_root_drop_gen(fs_info);
1352	else
1353	gen = btrfs_root_last_snapshot(s: &root->root_item);
1354
1355	entry = &ctx->path_cache_entries[level];
1356	entry->bytenr = bytenr;
1357	entry->is_shared = is_shared;
1358	entry->gen = gen;
1359
1360	/*
1361	* If we found an extent buffer is shared, set the cache result for all
1362	* extent buffers below it to true. As nodes in the path are COWed,
1363	* their sharedness is moved to their children, and if a leaf is COWed,
1364	* then the sharedness of a data extent becomes direct, the refcount of
1365	* data extent is increased in the extent item at the extent tree.
1366	*/
1367	if (is_shared) {
1368	for (int i = 0; i < level; i++) {
1369	entry = &ctx->path_cache_entries[i];
1370	entry->is_shared = is_shared;
1371	entry->gen = gen;
1372	}
1373	}
1374	}
1375
1376	/*
1377	* this adds all existing backrefs (inline backrefs, backrefs and delayed
1378	* refs) for the given bytenr to the refs list, merges duplicates and resolves
1379	* indirect refs to their parent bytenr.
1380	* When roots are found, they're added to the roots list
1381	*
1382	* @ctx: Backref walking context object, must be not NULL.
1383	* @sc: If !NULL, then immediately return BACKREF_FOUND_SHARED when a
1384	* shared extent is detected.
1385	*
1386	* Otherwise this returns 0 for success and <0 for an error.
1387	*
1388	* FIXME some caching might speed things up
1389	*/
1390	static int find_parent_nodes(struct btrfs_backref_walk_ctx *ctx,
1391	struct share_check *sc)
1392	{
1393	struct btrfs_root *root = btrfs_extent_root(fs_info: ctx->fs_info, bytenr: ctx->bytenr);
1394	struct btrfs_key key;
1395	struct btrfs_path *path;
1396	struct btrfs_delayed_ref_root *delayed_refs = NULL;
1397	struct btrfs_delayed_ref_head *head;
1398	int info_level = 0;
1399	int ret;
1400	struct prelim_ref *ref;
1401	struct rb_node *node;
1402	struct extent_inode_elem *eie = NULL;
1403	struct preftrees preftrees = {
1404	.direct = PREFTREE_INIT,
1405	.indirect = PREFTREE_INIT,
1406	.indirect_missing_keys = PREFTREE_INIT
1407	};
1408
1409	/* Roots ulist is not needed when using a sharedness check context. */
1410	if (sc)
1411	ASSERT(ctx->roots == NULL);
1412
1413	key.objectid = ctx->bytenr;
1414	key.offset = (u64)-1;
1415	if (btrfs_fs_incompat(ctx->fs_info, SKINNY_METADATA))
1416	key.type = BTRFS_METADATA_ITEM_KEY;
1417	else
1418	key.type = BTRFS_EXTENT_ITEM_KEY;
1419
1420	path = btrfs_alloc_path();
1421	if (!path)
1422	return -ENOMEM;
1423	if (!ctx->trans) {
1424	path->search_commit_root = 1;
1425	path->skip_locking = 1;
1426	}
1427
1428	if (ctx->time_seq == BTRFS_SEQ_LAST)
1429	path->skip_locking = 1;
1430
1431	again:
1432	head = NULL;
1433
1434	ret = btrfs_search_slot(NULL, root, key: &key, p: path, ins_len: 0, cow: 0);
1435	if (ret < 0)
1436	goto out;
1437	if (ret == 0) {
1438	/* This shouldn't happen, indicates a bug or fs corruption. */
1439	ASSERT(ret != 0);
1440	ret = -EUCLEAN;
1441	goto out;
1442	}
1443
1444	if (ctx->trans && likely(ctx->trans->type != __TRANS_DUMMY) &&
1445	ctx->time_seq != BTRFS_SEQ_LAST) {
1446	/*
1447	* We have a specific time_seq we care about and trans which
1448	* means we have the path lock, we need to grab the ref head and
1449	* lock it so we have a consistent view of the refs at the given
1450	* time.
1451	*/
1452	delayed_refs = &ctx->trans->transaction->delayed_refs;
1453	spin_lock(lock: &delayed_refs->lock);
1454	head = btrfs_find_delayed_ref_head(delayed_refs, bytenr: ctx->bytenr);
1455	if (head) {
1456	if (!mutex_trylock(lock: &head->mutex)) {
1457	refcount_inc(r: &head->refs);
1458	spin_unlock(lock: &delayed_refs->lock);
1459
1460	btrfs_release_path(p: path);
1461
1462	/*
1463	* Mutex was contended, block until it's
1464	* released and try again
1465	*/
1466	mutex_lock(&head->mutex);
1467	mutex_unlock(lock: &head->mutex);
1468	btrfs_put_delayed_ref_head(head);
1469	goto again;
1470	}
1471	spin_unlock(lock: &delayed_refs->lock);
1472	ret = add_delayed_refs(fs_info: ctx->fs_info, head, seq: ctx->time_seq,
1473	preftrees: &preftrees, sc);
1474	mutex_unlock(lock: &head->mutex);
1475	if (ret)
1476	goto out;
1477	} else {
1478	spin_unlock(lock: &delayed_refs->lock);
1479	}
1480	}
1481
1482	if (path->slots[0]) {
1483	struct extent_buffer *leaf;
1484	int slot;
1485
1486	path->slots[0]--;
1487	leaf = path->nodes[0];
1488	slot = path->slots[0];
1489	btrfs_item_key_to_cpu(eb: leaf, cpu_key: &key, nr: slot);
1490	if (key.objectid == ctx->bytenr &&
1491	(key.type == BTRFS_EXTENT_ITEM_KEY ||
1492	key.type == BTRFS_METADATA_ITEM_KEY)) {
1493	ret = add_inline_refs(ctx, path, info_level: &info_level,
1494	preftrees: &preftrees, sc);
1495	if (ret)
1496	goto out;
1497	ret = add_keyed_refs(ctx, extent_root: root, path, info_level,
1498	preftrees: &preftrees, sc);
1499	if (ret)
1500	goto out;
1501	}
1502	}
1503
1504	/*
1505	* If we have a share context and we reached here, it means the extent
1506	* is not directly shared (no multiple reference items for it),
1507	* otherwise we would have exited earlier with a return value of
1508	* BACKREF_FOUND_SHARED after processing delayed references or while
1509	* processing inline or keyed references from the extent tree.
1510	* The extent may however be indirectly shared through shared subtrees
1511	* as a result from creating snapshots, so we determine below what is
1512	* its parent node, in case we are dealing with a metadata extent, or
1513	* what's the leaf (or leaves), from a fs tree, that has a file extent
1514	* item pointing to it in case we are dealing with a data extent.
1515	*/
1516	ASSERT(extent_is_shared(sc) == 0);
1517
1518	/*
1519	* If we are here for a data extent and we have a share_check structure
1520	* it means the data extent is not directly shared (does not have
1521	* multiple reference items), so we have to check if a path in the fs
1522	* tree (going from the root node down to the leaf that has the file
1523	* extent item pointing to the data extent) is shared, that is, if any
1524	* of the extent buffers in the path is referenced by other trees.
1525	*/
1526	if (sc && ctx->bytenr == sc->data_bytenr) {
1527	/*
1528	* If our data extent is from a generation more recent than the
1529	* last generation used to snapshot the root, then we know that
1530	* it can not be shared through subtrees, so we can skip
1531	* resolving indirect references, there's no point in
1532	* determining the extent buffers for the path from the fs tree
1533	* root node down to the leaf that has the file extent item that
1534	* points to the data extent.
1535	*/
1536	if (sc->data_extent_gen >
1537	btrfs_root_last_snapshot(s: &sc->root->root_item)) {
1538	ret = BACKREF_FOUND_NOT_SHARED;
1539	goto out;
1540	}
1541
1542	/*
1543	* If we are only determining if a data extent is shared or not
1544	* and the corresponding file extent item is located in the same
1545	* leaf as the previous file extent item, we can skip resolving
1546	* indirect references for a data extent, since the fs tree path
1547	* is the same (same leaf, so same path). We skip as long as the
1548	* cached result for the leaf is valid and only if there's only
1549	* one file extent item pointing to the data extent, because in
1550	* the case of multiple file extent items, they may be located
1551	* in different leaves and therefore we have multiple paths.
1552	*/
1553	if (sc->ctx->curr_leaf_bytenr == sc->ctx->prev_leaf_bytenr &&
1554	sc->self_ref_count == 1) {
1555	bool cached;
1556	bool is_shared;
1557
1558	cached = lookup_backref_shared_cache(ctx: sc->ctx, root: sc->root,
1559	bytenr: sc->ctx->curr_leaf_bytenr,
1560	level: 0, is_shared: &is_shared);
1561	if (cached) {
1562	if (is_shared)
1563	ret = BACKREF_FOUND_SHARED;
1564	else
1565	ret = BACKREF_FOUND_NOT_SHARED;
1566	goto out;
1567	}
1568	}
1569	}
1570
1571	btrfs_release_path(p: path);
1572
1573	ret = add_missing_keys(fs_info: ctx->fs_info, preftrees: &preftrees, lock: path->skip_locking == 0);
1574	if (ret)
1575	goto out;
1576
1577	WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect_missing_keys.root.rb_root));
1578
1579	ret = resolve_indirect_refs(ctx, path, preftrees: &preftrees, sc);
1580	if (ret)
1581	goto out;
1582
1583	WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect.root.rb_root));
1584
1585	/*
1586	* This walks the tree of merged and resolved refs. Tree blocks are
1587	* read in as needed. Unique entries are added to the ulist, and
1588	* the list of found roots is updated.
1589	*
1590	* We release the entire tree in one go before returning.
1591	*/
1592	node = rb_first_cached(&preftrees.direct.root);
1593	while (node) {
1594	ref = rb_entry(node, struct prelim_ref, rbnode);
1595	node = rb_next(&ref->rbnode);
1596	/*
1597	* ref->count < 0 can happen here if there are delayed
1598	* refs with a node->action of BTRFS_DROP_DELAYED_REF.
1599	* prelim_ref_insert() relies on this when merging
1600	* identical refs to keep the overall count correct.
1601	* prelim_ref_insert() will merge only those refs
1602	* which compare identically. Any refs having
1603	* e.g. different offsets would not be merged,
1604	* and would retain their original ref->count < 0.
1605	*/
1606	if (ctx->roots && ref->count && ref->root_id && ref->parent == 0) {
1607	/* no parent == root of tree */
1608	ret = ulist_add(ulist: ctx->roots, val: ref->root_id, aux: 0, GFP_NOFS);
1609	if (ret < 0)
1610	goto out;
1611	}
1612	if (ref->count && ref->parent) {
1613	if (!ctx->skip_inode_ref_list && !ref->inode_list &&
1614	ref->level == 0) {
1615	struct btrfs_tree_parent_check check = { 0 };
1616	struct extent_buffer *eb;
1617
1618	check.level = ref->level;
1619
1620	eb = read_tree_block(fs_info: ctx->fs_info, bytenr: ref->parent,
1621	check: &check);
1622	if (IS_ERR(ptr: eb)) {
1623	ret = PTR_ERR(ptr: eb);
1624	goto out;
1625	}
1626	if (!extent_buffer_uptodate(eb)) {
1627	free_extent_buffer(eb);
1628	ret = -EIO;
1629	goto out;
1630	}
1631
1632	if (!path->skip_locking)
1633	btrfs_tree_read_lock(eb);
1634	ret = find_extent_in_eb(ctx, eb, eie: &eie);
1635	if (!path->skip_locking)
1636	btrfs_tree_read_unlock(eb);
1637	free_extent_buffer(eb);
1638	if (ret == BTRFS_ITERATE_EXTENT_INODES_STOP ||
1639	ret < 0)
1640	goto out;
1641	ref->inode_list = eie;
1642	/*
1643	* We transferred the list ownership to the ref,
1644	* so set to NULL to avoid a double free in case
1645	* an error happens after this.
1646	*/
1647	eie = NULL;
1648	}
1649	ret = ulist_add_merge_ptr(ulist: ctx->refs, val: ref->parent,
1650	aux: ref->inode_list,
1651	old_aux: (void **)&eie, GFP_NOFS);
1652	if (ret < 0)
1653	goto out;
1654	if (!ret && !ctx->skip_inode_ref_list) {
1655	/*
1656	* We've recorded that parent, so we must extend
1657	* its inode list here.
1658	*
1659	* However if there was corruption we may not
1660	* have found an eie, return an error in this
1661	* case.
1662	*/
1663	ASSERT(eie);
1664	if (!eie) {
1665	ret = -EUCLEAN;
1666	goto out;
1667	}
1668	while (eie->next)
1669	eie = eie->next;
1670	eie->next = ref->inode_list;
1671	}
1672	eie = NULL;
1673	/*
1674	* We have transferred the inode list ownership from
1675	* this ref to the ref we added to the 'refs' ulist.
1676	* So set this ref's inode list to NULL to avoid
1677	* use-after-free when our caller uses it or double
1678	* frees in case an error happens before we return.
1679	*/
1680	ref->inode_list = NULL;
1681	}
1682	cond_resched();
1683	}
1684
1685	out:
1686	btrfs_free_path(p: path);
1687
1688	prelim_release(preftree: &preftrees.direct);
1689	prelim_release(preftree: &preftrees.indirect);
1690	prelim_release(preftree: &preftrees.indirect_missing_keys);
1691
1692	if (ret == BTRFS_ITERATE_EXTENT_INODES_STOP || ret < 0)
1693	free_inode_elem_list(eie);
1694	return ret;
1695	}
1696
1697	/*
1698	* Finds all leaves with a reference to the specified combination of
1699	* @ctx->bytenr and @ctx->extent_item_pos. The bytenr of the found leaves are
1700	* added to the ulist at @ctx->refs, and that ulist is allocated by this
1701	* function. The caller should free the ulist with free_leaf_list() if
1702	* @ctx->ignore_extent_item_pos is false, otherwise a fimple ulist_free() is
1703	* enough.
1704	*
1705	* Returns 0 on success and < 0 on error. On error @ctx->refs is not allocated.
1706	*/
1707	int btrfs_find_all_leafs(struct btrfs_backref_walk_ctx *ctx)
1708	{
1709	int ret;
1710
1711	ASSERT(ctx->refs == NULL);
1712
1713	ctx->refs = ulist_alloc(GFP_NOFS);
1714	if (!ctx->refs)
1715	return -ENOMEM;
1716
1717	ret = find_parent_nodes(ctx, NULL);
1718	if (ret == BTRFS_ITERATE_EXTENT_INODES_STOP ||
1719	(ret < 0 && ret != -ENOENT)) {
1720	free_leaf_list(ulist: ctx->refs);
1721	ctx->refs = NULL;
1722	return ret;
1723	}
1724
1725	return 0;
1726	}
1727
1728	/*
1729	* Walk all backrefs for a given extent to find all roots that reference this
1730	* extent. Walking a backref means finding all extents that reference this
1731	* extent and in turn walk the backrefs of those, too. Naturally this is a
1732	* recursive process, but here it is implemented in an iterative fashion: We
1733	* find all referencing extents for the extent in question and put them on a
1734	* list. In turn, we find all referencing extents for those, further appending
1735	* to the list. The way we iterate the list allows adding more elements after
1736	* the current while iterating. The process stops when we reach the end of the
1737	* list.
1738	*
1739	* Found roots are added to @ctx->roots, which is allocated by this function if
1740	* it points to NULL, in which case the caller is responsible for freeing it
1741	* after it's not needed anymore.
1742	* This function requires @ctx->refs to be NULL, as it uses it for allocating a
1743	* ulist to do temporary work, and frees it before returning.
1744	*
1745	* Returns 0 on success, < 0 on error.
1746	*/
1747	static int btrfs_find_all_roots_safe(struct btrfs_backref_walk_ctx *ctx)
1748	{
1749	const u64 orig_bytenr = ctx->bytenr;
1750	const bool orig_skip_inode_ref_list = ctx->skip_inode_ref_list;
1751	bool roots_ulist_allocated = false;
1752	struct ulist_iterator uiter;
1753	int ret = 0;
1754
1755	ASSERT(ctx->refs == NULL);
1756
1757	ctx->refs = ulist_alloc(GFP_NOFS);
1758	if (!ctx->refs)
1759	return -ENOMEM;
1760
1761	if (!ctx->roots) {
1762	ctx->roots = ulist_alloc(GFP_NOFS);
1763	if (!ctx->roots) {
1764	ulist_free(ulist: ctx->refs);
1765	ctx->refs = NULL;
1766	return -ENOMEM;
1767	}
1768	roots_ulist_allocated = true;
1769	}
1770
1771	ctx->skip_inode_ref_list = true;
1772
1773	ULIST_ITER_INIT(&uiter);
1774	while (1) {
1775	struct ulist_node *node;
1776
1777	ret = find_parent_nodes(ctx, NULL);
1778	if (ret < 0 && ret != -ENOENT) {
1779	if (roots_ulist_allocated) {
1780	ulist_free(ulist: ctx->roots);
1781	ctx->roots = NULL;
1782	}
1783	break;
1784	}
1785	ret = 0;
1786	node = ulist_next(ulist: ctx->refs, uiter: &uiter);
1787	if (!node)
1788	break;
1789	ctx->bytenr = node->val;
1790	cond_resched();
1791	}
1792
1793	ulist_free(ulist: ctx->refs);
1794	ctx->refs = NULL;
1795	ctx->bytenr = orig_bytenr;
1796	ctx->skip_inode_ref_list = orig_skip_inode_ref_list;
1797
1798	return ret;
1799	}
1800
1801	int btrfs_find_all_roots(struct btrfs_backref_walk_ctx *ctx,
1802	bool skip_commit_root_sem)
1803	{
1804	int ret;
1805
1806	if (!ctx->trans && !skip_commit_root_sem)
1807	down_read(sem: &ctx->fs_info->commit_root_sem);
1808	ret = btrfs_find_all_roots_safe(ctx);
1809	if (!ctx->trans && !skip_commit_root_sem)
1810	up_read(sem: &ctx->fs_info->commit_root_sem);
1811	return ret;
1812	}
1813
1814	struct btrfs_backref_share_check_ctx *btrfs_alloc_backref_share_check_ctx(void)
1815	{
1816	struct btrfs_backref_share_check_ctx *ctx;
1817
1818	ctx = kzalloc(size: sizeof(*ctx), GFP_KERNEL);
1819	if (!ctx)
1820	return NULL;
1821
1822	ulist_init(ulist: &ctx->refs);
1823
1824	return ctx;
1825	}
1826
1827	void btrfs_free_backref_share_ctx(struct btrfs_backref_share_check_ctx *ctx)
1828	{
1829	if (!ctx)
1830	return;
1831
1832	ulist_release(ulist: &ctx->refs);
1833	kfree(objp: ctx);
1834	}
1835
1836	/*
1837	* Check if a data extent is shared or not.
1838	*
1839	* @inode: The inode whose extent we are checking.
1840	* @bytenr: Logical bytenr of the extent we are checking.
1841	* @extent_gen: Generation of the extent (file extent item) or 0 if it is
1842	* not known.
1843	* @ctx: A backref sharedness check context.
1844	*
1845	* btrfs_is_data_extent_shared uses the backref walking code but will short
1846	* circuit as soon as it finds a root or inode that doesn't match the
1847	* one passed in. This provides a significant performance benefit for
1848	* callers (such as fiemap) which want to know whether the extent is
1849	* shared but do not need a ref count.
1850	*
1851	* This attempts to attach to the running transaction in order to account for
1852	* delayed refs, but continues on even when no running transaction exists.
1853	*
1854	* Return: 0 if extent is not shared, 1 if it is shared, < 0 on error.
1855	*/
1856	int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
1857	u64 extent_gen,
1858	struct btrfs_backref_share_check_ctx *ctx)
1859	{
1860	struct btrfs_backref_walk_ctx walk_ctx = { 0 };
1861	struct btrfs_root *root = inode->root;
1862	struct btrfs_fs_info *fs_info = root->fs_info;
1863	struct btrfs_trans_handle *trans;
1864	struct ulist_iterator uiter;
1865	struct ulist_node *node;
1866	struct btrfs_seq_list elem = BTRFS_SEQ_LIST_INIT(elem);
1867	int ret = 0;
1868	struct share_check shared = {
1869	.ctx = ctx,
1870	.root = root,
1871	.inum = btrfs_ino(inode),
1872	.data_bytenr = bytenr,
1873	.data_extent_gen = extent_gen,
1874	.share_count = 0,
1875	.self_ref_count = 0,
1876	.have_delayed_delete_refs = false,
1877	};
1878	int level;
1879	bool leaf_cached;
1880	bool leaf_is_shared;
1881
1882	for (int i = 0; i < BTRFS_BACKREF_CTX_PREV_EXTENTS_SIZE; i++) {
1883	if (ctx->prev_extents_cache[i].bytenr == bytenr)
1884	return ctx->prev_extents_cache[i].is_shared;
1885	}
1886
1887	ulist_init(ulist: &ctx->refs);
1888
1889	trans = btrfs_join_transaction_nostart(root);
1890	if (IS_ERR(ptr: trans)) {
1891	if (PTR_ERR(ptr: trans) != -ENOENT && PTR_ERR(ptr: trans) != -EROFS) {
1892	ret = PTR_ERR(ptr: trans);
1893	goto out;
1894	}
1895	trans = NULL;
1896	down_read(sem: &fs_info->commit_root_sem);
1897	} else {
1898	btrfs_get_tree_mod_seq(fs_info, elem: &elem);
1899	walk_ctx.time_seq = elem.seq;
1900	}
1901
1902	ctx->use_path_cache = true;
1903
1904	/*
1905	* We may have previously determined that the current leaf is shared.
1906	* If it is, then we have a data extent that is shared due to a shared
1907	* subtree (caused by snapshotting) and we don't need to check for data
1908	* backrefs. If the leaf is not shared, then we must do backref walking
1909	* to determine if the data extent is shared through reflinks.
1910	*/
1911	leaf_cached = lookup_backref_shared_cache(ctx, root,
1912	bytenr: ctx->curr_leaf_bytenr, level: 0,
1913	is_shared: &leaf_is_shared);
1914	if (leaf_cached && leaf_is_shared) {
1915	ret = 1;
1916	goto out_trans;
1917	}
1918
1919	walk_ctx.skip_inode_ref_list = true;
1920	walk_ctx.trans = trans;
1921	walk_ctx.fs_info = fs_info;
1922	walk_ctx.refs = &ctx->refs;
1923
1924	/* -1 means we are in the bytenr of the data extent. */
1925	level = -1;
1926	ULIST_ITER_INIT(&uiter);
1927	while (1) {
1928	const unsigned long prev_ref_count = ctx->refs.nnodes;
1929
1930	walk_ctx.bytenr = bytenr;
1931	ret = find_parent_nodes(ctx: &walk_ctx, sc: &shared);
1932	if (ret == BACKREF_FOUND_SHARED ||
1933	ret == BACKREF_FOUND_NOT_SHARED) {
1934	/* If shared must return 1, otherwise return 0. */
1935	ret = (ret == BACKREF_FOUND_SHARED) ? 1 : 0;
1936	if (level >= 0)
1937	store_backref_shared_cache(ctx, root, bytenr,
1938	level, is_shared: ret == 1);
1939	break;
1940	}
1941	if (ret < 0 && ret != -ENOENT)
1942	break;
1943	ret = 0;
1944
1945	/*
1946	* More than one extent buffer (bytenr) may have been added to
1947	* the ctx->refs ulist, in which case we have to check multiple
1948	* tree paths in case the first one is not shared, so we can not
1949	* use the path cache which is made for a single path. Multiple
1950	* extent buffers at the current level happen when:
1951	*
1952	* 1) level -1, the data extent: If our data extent was not
1953	* directly shared (without multiple reference items), then
1954	* it might have a single reference item with a count > 1 for
1955	* the same offset, which means there are 2 (or more) file
1956	* extent items that point to the data extent - this happens
1957	* when a file extent item needs to be split and then one
1958	* item gets moved to another leaf due to a b+tree leaf split
1959	* when inserting some item. In this case the file extent
1960	* items may be located in different leaves and therefore
1961	* some of the leaves may be referenced through shared
1962	* subtrees while others are not. Since our extent buffer
1963	* cache only works for a single path (by far the most common
1964	* case and simpler to deal with), we can not use it if we
1965	* have multiple leaves (which implies multiple paths).
1966	*
1967	* 2) level >= 0, a tree node/leaf: We can have a mix of direct
1968	* and indirect references on a b+tree node/leaf, so we have
1969	* to check multiple paths, and the extent buffer (the
1970	* current bytenr) may be shared or not. One example is
1971	* during relocation as we may get a shared tree block ref
1972	* (direct ref) and a non-shared tree block ref (indirect
1973	* ref) for the same node/leaf.
1974	*/
1975	if ((ctx->refs.nnodes - prev_ref_count) > 1)
1976	ctx->use_path_cache = false;
1977
1978	if (level >= 0)
1979	store_backref_shared_cache(ctx, root, bytenr,
1980	level, is_shared: false);
1981	node = ulist_next(ulist: &ctx->refs, uiter: &uiter);
1982	if (!node)
1983	break;
1984	bytenr = node->val;
1985	if (ctx->use_path_cache) {
1986	bool is_shared;
1987	bool cached;
1988
1989	level++;
1990	cached = lookup_backref_shared_cache(ctx, root, bytenr,
1991	level, is_shared: &is_shared);
1992	if (cached) {
1993	ret = (is_shared ? 1 : 0);
1994	break;
1995	}
1996	}
1997	shared.share_count = 0;
1998	shared.have_delayed_delete_refs = false;
1999	cond_resched();
2000	}
2001
2002	/*
2003	* If the path cache is disabled, then it means at some tree level we
2004	* got multiple parents due to a mix of direct and indirect backrefs or
2005	* multiple leaves with file extent items pointing to the same data
2006	* extent. We have to invalidate the cache and cache only the sharedness
2007	* result for the levels where we got only one node/reference.
2008	*/
2009	if (!ctx->use_path_cache) {
2010	int i = 0;
2011
2012	level--;
2013	if (ret >= 0 && level >= 0) {
2014	bytenr = ctx->path_cache_entries[level].bytenr;
2015	ctx->use_path_cache = true;
2016	store_backref_shared_cache(ctx, root, bytenr, level, is_shared: ret);
2017	i = level + 1;
2018	}
2019
2020	for ( ; i < BTRFS_MAX_LEVEL; i++)
2021	ctx->path_cache_entries[i].bytenr = 0;
2022	}
2023
2024	/*
2025	* Cache the sharedness result for the data extent if we know our inode
2026	* has more than 1 file extent item that refers to the data extent.
2027	*/
2028	if (ret >= 0 && shared.self_ref_count > 1) {
2029	int slot = ctx->prev_extents_cache_slot;
2030
2031	ctx->prev_extents_cache[slot].bytenr = shared.data_bytenr;
2032	ctx->prev_extents_cache[slot].is_shared = (ret == 1);
2033
2034	slot = (slot + 1) % BTRFS_BACKREF_CTX_PREV_EXTENTS_SIZE;
2035	ctx->prev_extents_cache_slot = slot;
2036	}
2037
2038	out_trans:
2039	if (trans) {
2040	btrfs_put_tree_mod_seq(fs_info, elem: &elem);
2041	btrfs_end_transaction(trans);
2042	} else {
2043	up_read(sem: &fs_info->commit_root_sem);
2044	}
2045	out:
2046	ulist_release(ulist: &ctx->refs);
2047	ctx->prev_leaf_bytenr = ctx->curr_leaf_bytenr;
2048
2049	return ret;
2050	}
2051
2052	int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
2053	u64 start_off, struct btrfs_path *path,
2054	struct btrfs_inode_extref **ret_extref,
2055	u64 *found_off)
2056	{
2057	int ret, slot;
2058	struct btrfs_key key;
2059	struct btrfs_key found_key;
2060	struct btrfs_inode_extref *extref;
2061	const struct extent_buffer *leaf;
2062	unsigned long ptr;
2063
2064	key.objectid = inode_objectid;
2065	key.type = BTRFS_INODE_EXTREF_KEY;
2066	key.offset = start_off;
2067
2068	ret = btrfs_search_slot(NULL, root, key: &key, p: path, ins_len: 0, cow: 0);
2069	if (ret < 0)
2070	return ret;
2071
2072	while (1) {
2073	leaf = path->nodes[0];
2074	slot = path->slots[0];
2075	if (slot >= btrfs_header_nritems(eb: leaf)) {
2076	/*
2077	* If the item at offset is not found,
2078	* btrfs_search_slot will point us to the slot
2079	* where it should be inserted. In our case
2080	* that will be the slot directly before the
2081	* next INODE_REF_KEY_V2 item. In the case
2082	* that we're pointing to the last slot in a
2083	* leaf, we must move one leaf over.
2084	*/
2085	ret = btrfs_next_leaf(root, path);
2086	if (ret) {
2087	if (ret >= 1)
2088	ret = -ENOENT;
2089	break;
2090	}
2091	continue;
2092	}
2093
2094	btrfs_item_key_to_cpu(eb: leaf, cpu_key: &found_key, nr: slot);
2095
2096	/*
2097	* Check that we're still looking at an extended ref key for
2098	* this particular objectid. If we have different
2099	* objectid or type then there are no more to be found
2100	* in the tree and we can exit.
2101	*/
2102	ret = -ENOENT;
2103	if (found_key.objectid != inode_objectid)
2104	break;
2105	if (found_key.type != BTRFS_INODE_EXTREF_KEY)
2106	break;
2107
2108	ret = 0;
2109	ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
2110	extref = (struct btrfs_inode_extref *)ptr;
2111	*ret_extref = extref;
2112	if (found_off)
2113	*found_off = found_key.offset;
2114	break;
2115	}
2116
2117	return ret;
2118	}
2119
2120	/*
2121	* this iterates to turn a name (from iref/extref) into a full filesystem path.
2122	* Elements of the path are separated by '/' and the path is guaranteed to be
2123	* 0-terminated. the path is only given within the current file system.
2124	* Therefore, it never starts with a '/'. the caller is responsible to provide
2125	* "size" bytes in "dest". the dest buffer will be filled backwards. finally,
2126	* the start point of the resulting string is returned. this pointer is within
2127	* dest, normally.
2128	* in case the path buffer would overflow, the pointer is decremented further
2129	* as if output was written to the buffer, though no more output is actually
2130	* generated. that way, the caller can determine how much space would be
2131	* required for the path to fit into the buffer. in that case, the returned
2132	* value will be smaller than dest. callers must check this!
2133	*/
2134	char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
2135	u32 name_len, unsigned long name_off,
2136	struct extent_buffer *eb_in, u64 parent,
2137	char *dest, u32 size)
2138	{
2139	int slot;
2140	u64 next_inum;
2141	int ret;
2142	s64 bytes_left = ((s64)size) - 1;
2143	struct extent_buffer *eb = eb_in;
2144	struct btrfs_key found_key;
2145	struct btrfs_inode_ref *iref;
2146
2147	if (bytes_left >= 0)
2148	dest[bytes_left] = '\0';
2149
2150	while (1) {
2151	bytes_left -= name_len;
2152	if (bytes_left >= 0)
2153	read_extent_buffer(eb, dst: dest + bytes_left,
2154	start: name_off, len: name_len);
2155	if (eb != eb_in) {
2156	if (!path->skip_locking)
2157	btrfs_tree_read_unlock(eb);
2158	free_extent_buffer(eb);
2159	}
2160	ret = btrfs_find_item(fs_root, path, inum: parent, ioff: 0,
2161	BTRFS_INODE_REF_KEY, found_key: &found_key);
2162	if (ret > 0)
2163	ret = -ENOENT;
2164	if (ret)
2165	break;
2166
2167	next_inum = found_key.offset;
2168
2169	/* regular exit ahead */
2170	if (parent == next_inum)
2171	break;
2172
2173	slot = path->slots[0];
2174	eb = path->nodes[0];
2175	/* make sure we can use eb after releasing the path */
2176	if (eb != eb_in) {
2177	path->nodes[0] = NULL;
2178	path->locks[0] = 0;
2179	}
2180	btrfs_release_path(p: path);
2181	iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
2182
2183	name_len = btrfs_inode_ref_name_len(eb, s: iref);
2184	name_off = (unsigned long)(iref + 1);
2185
2186	parent = next_inum;
2187	--bytes_left;
2188	if (bytes_left >= 0)
2189	dest[bytes_left] = '/';
2190	}
2191
2192	btrfs_release_path(p: path);
2193
2194	if (ret)
2195	return ERR_PTR(error: ret);
2196
2197	return dest + bytes_left;
2198	}
2199
2200	/*
2201	* this makes the path point to (logical EXTENT_ITEM *)
2202	* returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
2203	* tree blocks and <0 on error.
2204	*/
2205	int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
2206	struct btrfs_path *path, struct btrfs_key *found_key,
2207	u64 *flags_ret)
2208	{
2209	struct btrfs_root *extent_root = btrfs_extent_root(fs_info, bytenr: logical);
2210	int ret;
2211	u64 flags;
2212	u64 size = 0;
2213	u32 item_size;
2214	const struct extent_buffer *eb;
2215	struct btrfs_extent_item *ei;
2216	struct btrfs_key key;
2217
2218	if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
2219	key.type = BTRFS_METADATA_ITEM_KEY;
2220	else
2221	key.type = BTRFS_EXTENT_ITEM_KEY;
2222	key.objectid = logical;
2223	key.offset = (u64)-1;
2224
2225	ret = btrfs_search_slot(NULL, root: extent_root, key: &key, p: path, ins_len: 0, cow: 0);
2226	if (ret < 0)
2227	return ret;
2228
2229	ret = btrfs_previous_extent_item(root: extent_root, path, min_objectid: 0);
2230	if (ret) {
2231	if (ret > 0)
2232	ret = -ENOENT;
2233	return ret;
2234	}
2235	btrfs_item_key_to_cpu(eb: path->nodes[0], cpu_key: found_key, nr: path->slots[0]);
2236	if (found_key->type == BTRFS_METADATA_ITEM_KEY)
2237	size = fs_info->nodesize;
2238	else if (found_key->type == BTRFS_EXTENT_ITEM_KEY)
2239	size = found_key->offset;
2240
2241	if (found_key->objectid > logical ||
2242	found_key->objectid + size <= logical) {
2243	btrfs_debug(fs_info,
2244	"logical %llu is not within any extent", logical);
2245	return -ENOENT;
2246	}
2247
2248	eb = path->nodes[0];
2249	item_size = btrfs_item_size(eb, slot: path->slots[0]);
2250	BUG_ON(item_size < sizeof(*ei));
2251
2252	ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
2253	flags = btrfs_extent_flags(eb, s: ei);
2254
2255	btrfs_debug(fs_info,
2256	"logical %llu is at position %llu within the extent (%llu EXTENT_ITEM %llu) flags %#llx size %u",
2257	logical, logical - found_key->objectid, found_key->objectid,
2258	found_key->offset, flags, item_size);
2259
2260	WARN_ON(!flags_ret);
2261	if (flags_ret) {
2262	if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
2263	*flags_ret = BTRFS_EXTENT_FLAG_TREE_BLOCK;
2264	else if (flags & BTRFS_EXTENT_FLAG_DATA)
2265	*flags_ret = BTRFS_EXTENT_FLAG_DATA;
2266	else
2267	BUG();
2268	return 0;
2269	}
2270
2271	return -EIO;
2272	}
2273
2274	/*
2275	* helper function to iterate extent inline refs. ptr must point to a 0 value
2276	* for the first call and may be modified. it is used to track state.
2277	* if more refs exist, 0 is returned and the next call to
2278	* get_extent_inline_ref must pass the modified ptr parameter to get the
2279	* next ref. after the last ref was processed, 1 is returned.
2280	* returns <0 on error
2281	*/
2282	static int get_extent_inline_ref(unsigned long *ptr,
2283	const struct extent_buffer *eb,
2284	const struct btrfs_key *key,
2285	const struct btrfs_extent_item *ei,
2286	u32 item_size,
2287	struct btrfs_extent_inline_ref **out_eiref,
2288	int *out_type)
2289	{
2290	unsigned long end;
2291	u64 flags;
2292	struct btrfs_tree_block_info *info;
2293
2294	if (!*ptr) {
2295	/* first call */
2296	flags = btrfs_extent_flags(eb, s: ei);
2297	if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
2298	if (key->type == BTRFS_METADATA_ITEM_KEY) {
2299	/* a skinny metadata extent */
2300	*out_eiref =
2301	(struct btrfs_extent_inline_ref *)(ei + 1);
2302	} else {
2303	WARN_ON(key->type != BTRFS_EXTENT_ITEM_KEY);
2304	info = (struct btrfs_tree_block_info *)(ei + 1);
2305	*out_eiref =
2306	(struct btrfs_extent_inline_ref *)(info + 1);
2307	}
2308	} else {
2309	*out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
2310	}
2311	*ptr = (unsigned long)*out_eiref;
2312	if ((unsigned long)(*ptr) >= (unsigned long)ei + item_size)
2313	return -ENOENT;
2314	}
2315
2316	end = (unsigned long)ei + item_size;
2317	*out_eiref = (struct btrfs_extent_inline_ref *)(*ptr);
2318	*out_type = btrfs_get_extent_inline_ref_type(eb, iref: *out_eiref,
2319	is_data: BTRFS_REF_TYPE_ANY);
2320	if (*out_type == BTRFS_REF_TYPE_INVALID)
2321	return -EUCLEAN;
2322
2323	*ptr += btrfs_extent_inline_ref_size(type: *out_type);
2324	WARN_ON(*ptr > end);
2325	if (*ptr == end)
2326	return 1; /* last */
2327
2328	return 0;
2329	}
2330
2331	/*
2332	* reads the tree block backref for an extent. tree level and root are returned
2333	* through out_level and out_root. ptr must point to a 0 value for the first
2334	* call and may be modified (see get_extent_inline_ref comment).
2335	* returns 0 if data was provided, 1 if there was no more data to provide or
2336	* <0 on error.
2337	*/
2338	int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
2339	struct btrfs_key *key, struct btrfs_extent_item *ei,
2340	u32 item_size, u64 *out_root, u8 *out_level)
2341	{
2342	int ret;
2343	int type;
2344	struct btrfs_extent_inline_ref *eiref;
2345
2346	if (*ptr == (unsigned long)-1)
2347	return 1;
2348
2349	while (1) {
2350	ret = get_extent_inline_ref(ptr, eb, key, ei, item_size,
2351	out_eiref: &eiref, out_type: &type);
2352	if (ret < 0)
2353	return ret;
2354
2355	if (type == BTRFS_TREE_BLOCK_REF_KEY ||
2356	type == BTRFS_SHARED_BLOCK_REF_KEY)
2357	break;
2358
2359	if (ret == 1)
2360	return 1;
2361	}
2362
2363	/* we can treat both ref types equally here */
2364	*out_root = btrfs_extent_inline_ref_offset(eb, s: eiref);
2365
2366	if (key->type == BTRFS_EXTENT_ITEM_KEY) {
2367	struct btrfs_tree_block_info *info;
2368
2369	info = (struct btrfs_tree_block_info *)(ei + 1);
2370	*out_level = btrfs_tree_block_level(eb, s: info);
2371	} else {
2372	ASSERT(key->type == BTRFS_METADATA_ITEM_KEY);
2373	*out_level = (u8)key->offset;
2374	}
2375
2376	if (ret == 1)
2377	*ptr = (unsigned long)-1;
2378
2379	return 0;
2380	}
2381
2382	static int iterate_leaf_refs(struct btrfs_fs_info *fs_info,
2383	struct extent_inode_elem *inode_list,
2384	u64 root, u64 extent_item_objectid,
2385	iterate_extent_inodes_t *iterate, void *ctx)
2386	{
2387	struct extent_inode_elem *eie;
2388	int ret = 0;
2389
2390	for (eie = inode_list; eie; eie = eie->next) {
2391	btrfs_debug(fs_info,
2392	"ref for %llu resolved, key (%llu EXTEND_DATA %llu), root %llu",
2393	extent_item_objectid, eie->inum,
2394	eie->offset, root);
2395	ret = iterate(eie->inum, eie->offset, eie->num_bytes, root, ctx);
2396	if (ret) {
2397	btrfs_debug(fs_info,
2398	"stopping iteration for %llu due to ret=%d",
2399	extent_item_objectid, ret);
2400	break;
2401	}
2402	}
2403
2404	return ret;
2405	}
2406
2407	/*
2408	* calls iterate() for every inode that references the extent identified by
2409	* the given parameters.
2410	* when the iterator function returns a non-zero value, iteration stops.
2411	*/
2412	int iterate_extent_inodes(struct btrfs_backref_walk_ctx *ctx,
2413	bool search_commit_root,
2414	iterate_extent_inodes_t *iterate, void *user_ctx)
2415	{
2416	int ret;
2417	struct ulist *refs;
2418	struct ulist_node *ref_node;
2419	struct btrfs_seq_list seq_elem = BTRFS_SEQ_LIST_INIT(seq_elem);
2420	struct ulist_iterator ref_uiter;
2421
2422	btrfs_debug(ctx->fs_info, "resolving all inodes for extent %llu",
2423	ctx->bytenr);
2424
2425	ASSERT(ctx->trans == NULL);
2426	ASSERT(ctx->roots == NULL);
2427
2428	if (!search_commit_root) {
2429	struct btrfs_trans_handle *trans;
2430
2431	trans = btrfs_attach_transaction(root: ctx->fs_info->tree_root);
2432	if (IS_ERR(ptr: trans)) {
2433	if (PTR_ERR(ptr: trans) != -ENOENT &&
2434	PTR_ERR(ptr: trans) != -EROFS)
2435	return PTR_ERR(ptr: trans);
2436	trans = NULL;
2437	}
2438	ctx->trans = trans;
2439	}
2440
2441	if (ctx->trans) {
2442	btrfs_get_tree_mod_seq(fs_info: ctx->fs_info, elem: &seq_elem);
2443	ctx->time_seq = seq_elem.seq;
2444	} else {
2445	down_read(sem: &ctx->fs_info->commit_root_sem);
2446	}
2447
2448	ret = btrfs_find_all_leafs(ctx);
2449	if (ret)
2450	goto out;
2451	refs = ctx->refs;
2452	ctx->refs = NULL;
2453
2454	ULIST_ITER_INIT(&ref_uiter);
2455	while (!ret && (ref_node = ulist_next(ulist: refs, uiter: &ref_uiter))) {
2456	const u64 leaf_bytenr = ref_node->val;
2457	struct ulist_node *root_node;
2458	struct ulist_iterator root_uiter;
2459	struct extent_inode_elem *inode_list;
2460
2461	inode_list = (struct extent_inode_elem *)(uintptr_t)ref_node->aux;
2462
2463	if (ctx->cache_lookup) {
2464	const u64 *root_ids;
2465	int root_count;
2466	bool cached;
2467
2468	cached = ctx->cache_lookup(leaf_bytenr, ctx->user_ctx,
2469	&root_ids, &root_count);
2470	if (cached) {
2471	for (int i = 0; i < root_count; i++) {
2472	ret = iterate_leaf_refs(fs_info: ctx->fs_info,
2473	inode_list,
2474	root: root_ids[i],
2475	extent_item_objectid: leaf_bytenr,
2476	iterate,
2477	ctx: user_ctx);
2478	if (ret)
2479	break;
2480	}
2481	continue;
2482	}
2483	}
2484
2485	if (!ctx->roots) {
2486	ctx->roots = ulist_alloc(GFP_NOFS);
2487	if (!ctx->roots) {
2488	ret = -ENOMEM;
2489	break;
2490	}
2491	}
2492
2493	ctx->bytenr = leaf_bytenr;
2494	ret = btrfs_find_all_roots_safe(ctx);
2495	if (ret)
2496	break;
2497
2498	if (ctx->cache_store)
2499	ctx->cache_store(leaf_bytenr, ctx->roots, ctx->user_ctx);
2500
2501	ULIST_ITER_INIT(&root_uiter);
2502	while (!ret && (root_node = ulist_next(ulist: ctx->roots, uiter: &root_uiter))) {
2503	btrfs_debug(ctx->fs_info,
2504	"root %llu references leaf %llu, data list %#llx",
2505	root_node->val, ref_node->val,
2506	ref_node->aux);
2507	ret = iterate_leaf_refs(fs_info: ctx->fs_info, inode_list,
2508	root: root_node->val, extent_item_objectid: ctx->bytenr,
2509	iterate, ctx: user_ctx);
2510	}
2511	ulist_reinit(ulist: ctx->roots);
2512	}
2513
2514	free_leaf_list(ulist: refs);
2515	out:
2516	if (ctx->trans) {
2517	btrfs_put_tree_mod_seq(fs_info: ctx->fs_info, elem: &seq_elem);
2518	btrfs_end_transaction(trans: ctx->trans);
2519	ctx->trans = NULL;
2520	} else {
2521	up_read(sem: &ctx->fs_info->commit_root_sem);
2522	}
2523
2524	ulist_free(ulist: ctx->roots);
2525	ctx->roots = NULL;
2526
2527	if (ret == BTRFS_ITERATE_EXTENT_INODES_STOP)
2528	ret = 0;
2529
2530	return ret;
2531	}
2532
2533	static int build_ino_list(u64 inum, u64 offset, u64 num_bytes, u64 root, void *ctx)
2534	{
2535	struct btrfs_data_container *inodes = ctx;
2536	const size_t c = 3 * sizeof(u64);
2537
2538	if (inodes->bytes_left >= c) {
2539	inodes->bytes_left -= c;
2540	inodes->val[inodes->elem_cnt] = inum;
2541	inodes->val[inodes->elem_cnt + 1] = offset;
2542	inodes->val[inodes->elem_cnt + 2] = root;
2543	inodes->elem_cnt += 3;
2544	} else {
2545	inodes->bytes_missing += c - inodes->bytes_left;
2546	inodes->bytes_left = 0;
2547	inodes->elem_missed += 3;
2548	}
2549
2550	return 0;
2551	}
2552
2553	int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
2554	struct btrfs_path *path,
2555	void *ctx, bool ignore_offset)
2556	{
2557	struct btrfs_backref_walk_ctx walk_ctx = { 0 };
2558	int ret;
2559	u64 flags = 0;
2560	struct btrfs_key found_key;
2561	int search_commit_root = path->search_commit_root;
2562
2563	ret = extent_from_logical(fs_info, logical, path, found_key: &found_key, flags_ret: &flags);
2564	btrfs_release_path(p: path);
2565	if (ret < 0)
2566	return ret;
2567	if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
2568	return -EINVAL;
2569
2570	walk_ctx.bytenr = found_key.objectid;
2571	if (ignore_offset)
2572	walk_ctx.ignore_extent_item_pos = true;
2573	else
2574	walk_ctx.extent_item_pos = logical - found_key.objectid;
2575	walk_ctx.fs_info = fs_info;
2576
2577	return iterate_extent_inodes(ctx: &walk_ctx, search_commit_root,
2578	iterate: build_ino_list, user_ctx: ctx);
2579	}
2580
2581	static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
2582	struct extent_buffer *eb, struct inode_fs_paths *ipath);
2583
2584	static int iterate_inode_refs(u64 inum, struct inode_fs_paths *ipath)
2585	{
2586	int ret = 0;
2587	int slot;
2588	u32 cur;
2589	u32 len;
2590	u32 name_len;
2591	u64 parent = 0;
2592	int found = 0;
2593	struct btrfs_root *fs_root = ipath->fs_root;
2594	struct btrfs_path *path = ipath->btrfs_path;
2595	struct extent_buffer *eb;
2596	struct btrfs_inode_ref *iref;
2597	struct btrfs_key found_key;
2598
2599	while (!ret) {
2600	ret = btrfs_find_item(fs_root, path, inum,
2601	ioff: parent ? parent + 1 : 0, BTRFS_INODE_REF_KEY,
2602	found_key: &found_key);
2603
2604	if (ret < 0)
2605	break;
2606	if (ret) {
2607	ret = found ? 0 : -ENOENT;
2608	break;
2609	}
2610	++found;
2611
2612	parent = found_key.offset;
2613	slot = path->slots[0];
2614	eb = btrfs_clone_extent_buffer(src: path->nodes[0]);
2615	if (!eb) {
2616	ret = -ENOMEM;
2617	break;
2618	}
2619	btrfs_release_path(p: path);
2620
2621	iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
2622
2623	for (cur = 0; cur < btrfs_item_size(eb, slot); cur += len) {
2624	name_len = btrfs_inode_ref_name_len(eb, s: iref);
2625	/* path must be released before calling iterate()! */
2626	btrfs_debug(fs_root->fs_info,
2627	"following ref at offset %u for inode %llu in tree %llu",
2628	cur, found_key.objectid,
2629	fs_root->root_key.objectid);
2630	ret = inode_to_path(inum: parent, name_len,
2631	name_off: (unsigned long)(iref + 1), eb, ipath);
2632	if (ret)
2633	break;
2634	len = sizeof(*iref) + name_len;
2635	iref = (struct btrfs_inode_ref *)((char *)iref + len);
2636	}
2637	free_extent_buffer(eb);
2638	}
2639
2640	btrfs_release_path(p: path);
2641
2642	return ret;
2643	}
2644
2645	static int iterate_inode_extrefs(u64 inum, struct inode_fs_paths *ipath)
2646	{
2647	int ret;
2648	int slot;
2649	u64 offset = 0;
2650	u64 parent;
2651	int found = 0;
2652	struct btrfs_root *fs_root = ipath->fs_root;
2653	struct btrfs_path *path = ipath->btrfs_path;
2654	struct extent_buffer *eb;
2655	struct btrfs_inode_extref *extref;
2656	u32 item_size;
2657	u32 cur_offset;
2658	unsigned long ptr;
2659
2660	while (1) {
2661	ret = btrfs_find_one_extref(root: fs_root, inode_objectid: inum, start_off: offset, path, ret_extref: &extref,
2662	found_off: &offset);
2663	if (ret < 0)
2664	break;
2665	if (ret) {
2666	ret = found ? 0 : -ENOENT;
2667	break;
2668	}
2669	++found;
2670
2671	slot = path->slots[0];
2672	eb = btrfs_clone_extent_buffer(src: path->nodes[0]);
2673	if (!eb) {
2674	ret = -ENOMEM;
2675	break;
2676	}
2677	btrfs_release_path(p: path);
2678
2679	item_size = btrfs_item_size(eb, slot);
2680	ptr = btrfs_item_ptr_offset(eb, slot);
2681	cur_offset = 0;
2682
2683	while (cur_offset < item_size) {
2684	u32 name_len;
2685
2686	extref = (struct btrfs_inode_extref *)(ptr + cur_offset);
2687	parent = btrfs_inode_extref_parent(eb, s: extref);
2688	name_len = btrfs_inode_extref_name_len(eb, s: extref);
2689	ret = inode_to_path(inum: parent, name_len,
2690	name_off: (unsigned long)&extref->name, eb, ipath);
2691	if (ret)
2692	break;
2693
2694	cur_offset += btrfs_inode_extref_name_len(eb, s: extref);
2695	cur_offset += sizeof(*extref);
2696	}
2697	free_extent_buffer(eb);
2698
2699	offset++;
2700	}
2701
2702	btrfs_release_path(p: path);
2703
2704	return ret;
2705	}
2706
2707	/*
2708	* returns 0 if the path could be dumped (probably truncated)
2709	* returns <0 in case of an error
2710	*/
2711	static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
2712	struct extent_buffer *eb, struct inode_fs_paths *ipath)
2713	{
2714	char *fspath;
2715	char *fspath_min;
2716	int i = ipath->fspath->elem_cnt;
2717	const int s_ptr = sizeof(char *);
2718	u32 bytes_left;
2719
2720	bytes_left = ipath->fspath->bytes_left > s_ptr ?
2721	ipath->fspath->bytes_left - s_ptr : 0;
2722
2723	fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
2724	fspath = btrfs_ref_to_path(fs_root: ipath->fs_root, path: ipath->btrfs_path, name_len,
2725	name_off, eb_in: eb, parent: inum, dest: fspath_min, size: bytes_left);
2726	if (IS_ERR(ptr: fspath))
2727	return PTR_ERR(ptr: fspath);
2728
2729	if (fspath > fspath_min) {
2730	ipath->fspath->val[i] = (u64)(unsigned long)fspath;
2731	++ipath->fspath->elem_cnt;
2732	ipath->fspath->bytes_left = fspath - fspath_min;
2733	} else {
2734	++ipath->fspath->elem_missed;
2735	ipath->fspath->bytes_missing += fspath_min - fspath;
2736	ipath->fspath->bytes_left = 0;
2737	}
2738
2739	return 0;
2740	}
2741
2742	/*
2743	* this dumps all file system paths to the inode into the ipath struct, provided
2744	* is has been created large enough. each path is zero-terminated and accessed
2745	* from ipath->fspath->val[i].
2746	* when it returns, there are ipath->fspath->elem_cnt number of paths available
2747	* in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
2748	* number of missed paths is recorded in ipath->fspath->elem_missed, otherwise,
2749	* it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
2750	* have been needed to return all paths.
2751	*/
2752	int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
2753	{
2754	int ret;
2755	int found_refs = 0;
2756
2757	ret = iterate_inode_refs(inum, ipath);
2758	if (!ret)
2759	++found_refs;
2760	else if (ret != -ENOENT)
2761	return ret;
2762
2763	ret = iterate_inode_extrefs(inum, ipath);
2764	if (ret == -ENOENT && found_refs)
2765	return 0;
2766
2767	return ret;
2768	}
2769
2770	struct btrfs_data_container *init_data_container(u32 total_bytes)
2771	{
2772	struct btrfs_data_container *data;
2773	size_t alloc_bytes;
2774
2775	alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
2776	data = kvmalloc(size: alloc_bytes, GFP_KERNEL);
2777	if (!data)
2778	return ERR_PTR(error: -ENOMEM);
2779
2780	if (total_bytes >= sizeof(*data)) {
2781	data->bytes_left = total_bytes - sizeof(*data);
2782	data->bytes_missing = 0;
2783	} else {
2784	data->bytes_missing = sizeof(*data) - total_bytes;
2785	data->bytes_left = 0;
2786	}
2787
2788	data->elem_cnt = 0;
2789	data->elem_missed = 0;
2790
2791	return data;
2792	}
2793
2794	/*
2795	* allocates space to return multiple file system paths for an inode.
2796	* total_bytes to allocate are passed, note that space usable for actual path
2797	* information will be total_bytes - sizeof(struct inode_fs_paths).
2798	* the returned pointer must be freed with free_ipath() in the end.
2799	*/
2800	struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
2801	struct btrfs_path *path)
2802	{
2803	struct inode_fs_paths *ifp;
2804	struct btrfs_data_container *fspath;
2805
2806	fspath = init_data_container(total_bytes);
2807	if (IS_ERR(ptr: fspath))
2808	return ERR_CAST(ptr: fspath);
2809
2810	ifp = kmalloc(size: sizeof(*ifp), GFP_KERNEL);
2811	if (!ifp) {
2812	kvfree(addr: fspath);
2813	return ERR_PTR(error: -ENOMEM);
2814	}
2815
2816	ifp->btrfs_path = path;
2817	ifp->fspath = fspath;
2818	ifp->fs_root = fs_root;
2819
2820	return ifp;
2821	}
2822
2823	void free_ipath(struct inode_fs_paths *ipath)
2824	{
2825	if (!ipath)
2826	return;
2827	kvfree(addr: ipath->fspath);
2828	kfree(objp: ipath);
2829	}
2830
2831	struct btrfs_backref_iter *btrfs_backref_iter_alloc(struct btrfs_fs_info *fs_info)
2832	{
2833	struct btrfs_backref_iter *ret;
2834
2835	ret = kzalloc(size: sizeof(*ret), GFP_NOFS);
2836	if (!ret)
2837	return NULL;
2838
2839	ret->path = btrfs_alloc_path();
2840	if (!ret->path) {
2841	kfree(objp: ret);
2842	return NULL;
2843	}
2844
2845	/* Current backref iterator only supports iteration in commit root */
2846	ret->path->search_commit_root = 1;
2847	ret->path->skip_locking = 1;
2848	ret->fs_info = fs_info;
2849
2850	return ret;
2851	}
2852
2853	int btrfs_backref_iter_start(struct btrfs_backref_iter *iter, u64 bytenr)
2854	{
2855	struct btrfs_fs_info *fs_info = iter->fs_info;
2856	struct btrfs_root *extent_root = btrfs_extent_root(fs_info, bytenr);
2857	struct btrfs_path *path = iter->path;
2858	struct btrfs_extent_item *ei;
2859	struct btrfs_key key;
2860	int ret;
2861
2862	key.objectid = bytenr;
2863	key.type = BTRFS_METADATA_ITEM_KEY;
2864	key.offset = (u64)-1;
2865	iter->bytenr = bytenr;
2866
2867	ret = btrfs_search_slot(NULL, root: extent_root, key: &key, p: path, ins_len: 0, cow: 0);
2868	if (ret < 0)
2869	return ret;
2870	if (ret == 0) {
2871	ret = -EUCLEAN;
2872	goto release;
2873	}
2874	if (path->slots[0] == 0) {
2875	WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG));
2876	ret = -EUCLEAN;
2877	goto release;
2878	}
2879	path->slots[0]--;
2880
2881	btrfs_item_key_to_cpu(eb: path->nodes[0], cpu_key: &key, nr: path->slots[0]);
2882	if ((key.type != BTRFS_EXTENT_ITEM_KEY &&
2883	key.type != BTRFS_METADATA_ITEM_KEY) || key.objectid != bytenr) {
2884	ret = -ENOENT;
2885	goto release;
2886	}
2887	memcpy(&iter->cur_key, &key, sizeof(key));
2888	iter->item_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
2889	path->slots[0]);
2890	iter->end_ptr = (u32)(iter->item_ptr +
2891	btrfs_item_size(eb: path->nodes[0], slot: path->slots[0]));
2892	ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
2893	struct btrfs_extent_item);
2894
2895	/*
2896	* Only support iteration on tree backref yet.
2897	*
2898	* This is an extra precaution for non skinny-metadata, where
2899	* EXTENT_ITEM is also used for tree blocks, that we can only use
2900	* extent flags to determine if it's a tree block.
2901	*/
2902	if (btrfs_extent_flags(eb: path->nodes[0], s: ei) & BTRFS_EXTENT_FLAG_DATA) {
2903	ret = -ENOTSUPP;
2904	goto release;
2905	}
2906	iter->cur_ptr = (u32)(iter->item_ptr + sizeof(*ei));
2907
2908	/* If there is no inline backref, go search for keyed backref */
2909	if (iter->cur_ptr >= iter->end_ptr) {
2910	ret = btrfs_next_item(root: extent_root, p: path);
2911
2912	/* No inline nor keyed ref */
2913	if (ret > 0) {
2914	ret = -ENOENT;
2915	goto release;
2916	}
2917	if (ret < 0)
2918	goto release;
2919
2920	btrfs_item_key_to_cpu(eb: path->nodes[0], cpu_key: &iter->cur_key,
2921	nr: path->slots[0]);
2922	if (iter->cur_key.objectid != bytenr ||
2923	(iter->cur_key.type != BTRFS_SHARED_BLOCK_REF_KEY &&
2924	iter->cur_key.type != BTRFS_TREE_BLOCK_REF_KEY)) {
2925	ret = -ENOENT;
2926	goto release;
2927	}
2928	iter->cur_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
2929	path->slots[0]);
2930	iter->item_ptr = iter->cur_ptr;
2931	iter->end_ptr = (u32)(iter->item_ptr + btrfs_item_size(
2932	eb: path->nodes[0], slot: path->slots[0]));
2933	}
2934
2935	return 0;
2936	release:
2937	btrfs_backref_iter_release(iter);
2938	return ret;
2939	}
2940
2941	/*
2942	* Go to the next backref item of current bytenr, can be either inlined or
2943	* keyed.
2944	*
2945	* Caller needs to check whether it's inline ref or not by iter->cur_key.
2946	*
2947	* Return 0 if we get next backref without problem.
2948	* Return >0 if there is no extra backref for this bytenr.
2949	* Return <0 if there is something wrong happened.
2950	*/
2951	int btrfs_backref_iter_next(struct btrfs_backref_iter *iter)
2952	{
2953	struct extent_buffer *eb = btrfs_backref_get_eb(iter);
2954	struct btrfs_root *extent_root;
2955	struct btrfs_path *path = iter->path;
2956	struct btrfs_extent_inline_ref *iref;
2957	int ret;
2958	u32 size;
2959
2960	if (btrfs_backref_iter_is_inline_ref(iter)) {
2961	/* We're still inside the inline refs */
2962	ASSERT(iter->cur_ptr < iter->end_ptr);
2963
2964	if (btrfs_backref_has_tree_block_info(iter)) {
2965	/* First tree block info */
2966	size = sizeof(struct btrfs_tree_block_info);
2967	} else {
2968	/* Use inline ref type to determine the size */
2969	int type;
2970
2971	iref = (struct btrfs_extent_inline_ref *)
2972	((unsigned long)iter->cur_ptr);
2973	type = btrfs_extent_inline_ref_type(eb, s: iref);
2974
2975	size = btrfs_extent_inline_ref_size(type);
2976	}
2977	iter->cur_ptr += size;
2978	if (iter->cur_ptr < iter->end_ptr)
2979	return 0;
2980
2981	/* All inline items iterated, fall through */
2982	}
2983
2984	/* We're at keyed items, there is no inline item, go to the next one */
2985	extent_root = btrfs_extent_root(fs_info: iter->fs_info, bytenr: iter->bytenr);
2986	ret = btrfs_next_item(root: extent_root, p: iter->path);
2987	if (ret)
2988	return ret;
2989
2990	btrfs_item_key_to_cpu(eb: path->nodes[0], cpu_key: &iter->cur_key, nr: path->slots[0]);
2991	if (iter->cur_key.objectid != iter->bytenr ||
2992	(iter->cur_key.type != BTRFS_TREE_BLOCK_REF_KEY &&
2993	iter->cur_key.type != BTRFS_SHARED_BLOCK_REF_KEY))
2994	return 1;
2995	iter->item_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
2996	path->slots[0]);
2997	iter->cur_ptr = iter->item_ptr;
2998	iter->end_ptr = iter->item_ptr + (u32)btrfs_item_size(eb: path->nodes[0],
2999	slot: path->slots[0]);
3000	return 0;
3001	}
3002
3003	void btrfs_backref_init_cache(struct btrfs_fs_info *fs_info,
3004	struct btrfs_backref_cache *cache, bool is_reloc)
3005	{
3006	int i;
3007
3008	cache->rb_root = RB_ROOT;
3009	for (i = 0; i < BTRFS_MAX_LEVEL; i++)
3010	INIT_LIST_HEAD(list: &cache->pending[i]);
3011	INIT_LIST_HEAD(list: &cache->changed);
3012	INIT_LIST_HEAD(list: &cache->detached);
3013	INIT_LIST_HEAD(list: &cache->leaves);
3014	INIT_LIST_HEAD(list: &cache->pending_edge);
3015	INIT_LIST_HEAD(list: &cache->useless_node);
3016	cache->fs_info = fs_info;
3017	cache->is_reloc = is_reloc;
3018	}
3019
3020	struct btrfs_backref_node *btrfs_backref_alloc_node(
3021	struct btrfs_backref_cache *cache, u64 bytenr, int level)
3022	{
3023	struct btrfs_backref_node *node;
3024
3025	ASSERT(level >= 0 && level < BTRFS_MAX_LEVEL);
3026	node = kzalloc(size: sizeof(*node), GFP_NOFS);
3027	if (!node)
3028	return node;
3029
3030	INIT_LIST_HEAD(list: &node->list);
3031	INIT_LIST_HEAD(list: &node->upper);
3032	INIT_LIST_HEAD(list: &node->lower);
3033	RB_CLEAR_NODE(&node->rb_node);
3034	cache->nr_nodes++;
3035	node->level = level;
3036	node->bytenr = bytenr;
3037
3038	return node;
3039	}
3040
3041	struct btrfs_backref_edge *btrfs_backref_alloc_edge(
3042	struct btrfs_backref_cache *cache)
3043	{
3044	struct btrfs_backref_edge *edge;
3045
3046	edge = kzalloc(size: sizeof(*edge), GFP_NOFS);
3047	if (edge)
3048	cache->nr_edges++;
3049	return edge;
3050	}
3051
3052	/*
3053	* Drop the backref node from cache, also cleaning up all its
3054	* upper edges and any uncached nodes in the path.
3055	*
3056	* This cleanup happens bottom up, thus the node should either
3057	* be the lowest node in the cache or a detached node.
3058	*/
3059	void btrfs_backref_cleanup_node(struct btrfs_backref_cache *cache,
3060	struct btrfs_backref_node *node)
3061	{
3062	struct btrfs_backref_node *upper;
3063	struct btrfs_backref_edge *edge;
3064
3065	if (!node)
3066	return;
3067
3068	BUG_ON(!node->lowest && !node->detached);
3069	while (!list_empty(head: &node->upper)) {
3070	edge = list_entry(node->upper.next, struct btrfs_backref_edge,
3071	list[LOWER]);
3072	upper = edge->node[UPPER];
3073	list_del(entry: &edge->list[LOWER]);
3074	list_del(entry: &edge->list[UPPER]);
3075	btrfs_backref_free_edge(cache, edge);
3076
3077	/*
3078	* Add the node to leaf node list if no other child block
3079	* cached.
3080	*/
3081	if (list_empty(head: &upper->lower)) {
3082	list_add_tail(new: &upper->lower, head: &cache->leaves);
3083	upper->lowest = 1;
3084	}
3085	}
3086
3087	btrfs_backref_drop_node(tree: cache, node);
3088	}
3089
3090	/*
3091	* Release all nodes/edges from current cache
3092	*/
3093	void btrfs_backref_release_cache(struct btrfs_backref_cache *cache)
3094	{
3095	struct btrfs_backref_node *node;
3096	int i;
3097
3098	while (!list_empty(head: &cache->detached)) {
3099	node = list_entry(cache->detached.next,
3100	struct btrfs_backref_node, list);
3101	btrfs_backref_cleanup_node(cache, node);
3102	}
3103
3104	while (!list_empty(head: &cache->leaves)) {
3105	node = list_entry(cache->leaves.next,
3106	struct btrfs_backref_node, lower);
3107	btrfs_backref_cleanup_node(cache, node);
3108	}
3109
3110	cache->last_trans = 0;
3111
3112	for (i = 0; i < BTRFS_MAX_LEVEL; i++)
3113	ASSERT(list_empty(&cache->pending[i]));
3114	ASSERT(list_empty(&cache->pending_edge));
3115	ASSERT(list_empty(&cache->useless_node));
3116	ASSERT(list_empty(&cache->changed));
3117	ASSERT(list_empty(&cache->detached));
3118	ASSERT(RB_EMPTY_ROOT(&cache->rb_root));
3119	ASSERT(!cache->nr_nodes);
3120	ASSERT(!cache->nr_edges);
3121	}
3122
3123	/*
3124	* Handle direct tree backref
3125	*
3126	* Direct tree backref means, the backref item shows its parent bytenr
3127	* directly. This is for SHARED_BLOCK_REF backref (keyed or inlined).
3128	*
3129	* @ref_key: The converted backref key.
3130	* For keyed backref, it's the item key.
3131	* For inlined backref, objectid is the bytenr,
3132	* type is btrfs_inline_ref_type, offset is
3133	* btrfs_inline_ref_offset.
3134	*/
3135	static int handle_direct_tree_backref(struct btrfs_backref_cache *cache,
3136	struct btrfs_key *ref_key,
3137	struct btrfs_backref_node *cur)
3138	{
3139	struct btrfs_backref_edge *edge;
3140	struct btrfs_backref_node *upper;
3141	struct rb_node *rb_node;
3142
3143	ASSERT(ref_key->type == BTRFS_SHARED_BLOCK_REF_KEY);
3144
3145	/* Only reloc root uses backref pointing to itself */
3146	if (ref_key->objectid == ref_key->offset) {
3147	struct btrfs_root *root;
3148
3149	cur->is_reloc_root = 1;
3150	/* Only reloc backref cache cares about a specific root */
3151	if (cache->is_reloc) {
3152	root = find_reloc_root(fs_info: cache->fs_info, bytenr: cur->bytenr);
3153	if (!root)
3154	return -ENOENT;
3155	cur->root = root;
3156	} else {
3157	/*
3158	* For generic purpose backref cache, reloc root node
3159	* is useless.
3160	*/
3161	list_add(new: &cur->list, head: &cache->useless_node);
3162	}
3163	return 0;
3164	}
3165
3166	edge = btrfs_backref_alloc_edge(cache);
3167	if (!edge)
3168	return -ENOMEM;
3169
3170	rb_node = rb_simple_search(root: &cache->rb_root, bytenr: ref_key->offset);
3171	if (!rb_node) {
3172	/* Parent node not yet cached */
3173	upper = btrfs_backref_alloc_node(cache, bytenr: ref_key->offset,
3174	level: cur->level + 1);
3175	if (!upper) {
3176	btrfs_backref_free_edge(cache, edge);
3177	return -ENOMEM;
3178	}
3179
3180	/*
3181	* Backrefs for the upper level block isn't cached, add the
3182	* block to pending list
3183	*/
3184	list_add_tail(new: &edge->list[UPPER], head: &cache->pending_edge);
3185	} else {
3186	/* Parent node already cached */
3187	upper = rb_entry(rb_node, struct btrfs_backref_node, rb_node);
3188	ASSERT(upper->checked);
3189	INIT_LIST_HEAD(list: &edge->list[UPPER]);
3190	}
3191	btrfs_backref_link_edge(edge, lower: cur, upper, LINK_LOWER);
3192	return 0;
3193	}
3194
3195	/*
3196	* Handle indirect tree backref
3197	*
3198	* Indirect tree backref means, we only know which tree the node belongs to.
3199	* We still need to do a tree search to find out the parents. This is for
3200	* TREE_BLOCK_REF backref (keyed or inlined).
3201	*
3202	* @trans: Transaction handle.
3203	* @ref_key: The same as @ref_key in handle_direct_tree_backref()
3204	* @tree_key: The first key of this tree block.
3205	* @path: A clean (released) path, to avoid allocating path every time
3206	* the function get called.
3207	*/
3208	static int handle_indirect_tree_backref(struct btrfs_trans_handle *trans,
3209	struct btrfs_backref_cache *cache,
3210	struct btrfs_path *path,
3211	struct btrfs_key *ref_key,
3212	struct btrfs_key *tree_key,
3213	struct btrfs_backref_node *cur)
3214	{
3215	struct btrfs_fs_info *fs_info = cache->fs_info;
3216	struct btrfs_backref_node *upper;
3217	struct btrfs_backref_node *lower;
3218	struct btrfs_backref_edge *edge;
3219	struct extent_buffer *eb;
3220	struct btrfs_root *root;
3221	struct rb_node *rb_node;
3222	int level;
3223	bool need_check = true;
3224	int ret;
3225
3226	root = btrfs_get_fs_root(fs_info, objectid: ref_key->offset, check_ref: false);
3227	if (IS_ERR(ptr: root))
3228	return PTR_ERR(ptr: root);
3229	if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
3230	cur->cowonly = 1;
3231
3232	if (btrfs_root_level(s: &root->root_item) == cur->level) {
3233	/* Tree root */
3234	ASSERT(btrfs_root_bytenr(&root->root_item) == cur->bytenr);
3235	/*
3236	* For reloc backref cache, we may ignore reloc root. But for
3237	* general purpose backref cache, we can't rely on
3238	* btrfs_should_ignore_reloc_root() as it may conflict with
3239	* current running relocation and lead to missing root.
3240	*
3241	* For general purpose backref cache, reloc root detection is
3242	* completely relying on direct backref (key->offset is parent
3243	* bytenr), thus only do such check for reloc cache.
3244	*/
3245	if (btrfs_should_ignore_reloc_root(root) && cache->is_reloc) {
3246	btrfs_put_root(root);
3247	list_add(new: &cur->list, head: &cache->useless_node);
3248	} else {
3249	cur->root = root;
3250	}
3251	return 0;
3252	}
3253
3254	level = cur->level + 1;
3255
3256	/* Search the tree to find parent blocks referring to the block */
3257	path->search_commit_root = 1;
3258	path->skip_locking = 1;
3259	path->lowest_level = level;
3260	ret = btrfs_search_slot(NULL, root, key: tree_key, p: path, ins_len: 0, cow: 0);
3261	path->lowest_level = 0;
3262	if (ret < 0) {
3263	btrfs_put_root(root);
3264	return ret;
3265	}
3266	if (ret > 0 && path->slots[level] > 0)
3267	path->slots[level]--;
3268
3269	eb = path->nodes[level];
3270	if (btrfs_node_blockptr(eb, nr: path->slots[level]) != cur->bytenr) {
3271	btrfs_err(fs_info,
3272	"couldn't find block (%llu) (level %d) in tree (%llu) with key (%llu %u %llu)",
3273	cur->bytenr, level - 1, root->root_key.objectid,
3274	tree_key->objectid, tree_key->type, tree_key->offset);
3275	btrfs_put_root(root);
3276	ret = -ENOENT;
3277	goto out;
3278	}
3279	lower = cur;
3280
3281	/* Add all nodes and edges in the path */
3282	for (; level < BTRFS_MAX_LEVEL; level++) {
3283	if (!path->nodes[level]) {
3284	ASSERT(btrfs_root_bytenr(&root->root_item) ==
3285	lower->bytenr);
3286	/* Same as previous should_ignore_reloc_root() call */
3287	if (btrfs_should_ignore_reloc_root(root) &&
3288	cache->is_reloc) {
3289	btrfs_put_root(root);
3290	list_add(new: &lower->list, head: &cache->useless_node);
3291	} else {
3292	lower->root = root;
3293	}
3294	break;
3295	}
3296
3297	edge = btrfs_backref_alloc_edge(cache);
3298	if (!edge) {
3299	btrfs_put_root(root);
3300	ret = -ENOMEM;
3301	goto out;
3302	}
3303
3304	eb = path->nodes[level];
3305	rb_node = rb_simple_search(root: &cache->rb_root, bytenr: eb->start);
3306	if (!rb_node) {
3307	upper = btrfs_backref_alloc_node(cache, bytenr: eb->start,
3308	level: lower->level + 1);
3309	if (!upper) {
3310	btrfs_put_root(root);
3311	btrfs_backref_free_edge(cache, edge);
3312	ret = -ENOMEM;
3313	goto out;
3314	}
3315	upper->owner = btrfs_header_owner(eb);
3316	if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
3317	upper->cowonly = 1;
3318
3319	/*
3320	* If we know the block isn't shared we can avoid
3321	* checking its backrefs.
3322	*/
3323	if (btrfs_block_can_be_shared(trans, root, buf: eb))
3324	upper->checked = 0;
3325	else
3326	upper->checked = 1;
3327
3328	/*
3329	* Add the block to pending list if we need to check its
3330	* backrefs, we only do this once while walking up a
3331	* tree as we will catch anything else later on.
3332	*/
3333	if (!upper->checked && need_check) {
3334	need_check = false;
3335	list_add_tail(new: &edge->list[UPPER],
3336	head: &cache->pending_edge);
3337	} else {
3338	if (upper->checked)
3339	need_check = true;
3340	INIT_LIST_HEAD(list: &edge->list[UPPER]);
3341	}
3342	} else {
3343	upper = rb_entry(rb_node, struct btrfs_backref_node,
3344	rb_node);
3345	ASSERT(upper->checked);
3346	INIT_LIST_HEAD(list: &edge->list[UPPER]);
3347	if (!upper->owner)
3348	upper->owner = btrfs_header_owner(eb);
3349	}
3350	btrfs_backref_link_edge(edge, lower, upper, LINK_LOWER);
3351
3352	if (rb_node) {
3353	btrfs_put_root(root);
3354	break;
3355	}
3356	lower = upper;
3357	upper = NULL;
3358	}
3359	out:
3360	btrfs_release_path(p: path);
3361	return ret;
3362	}
3363
3364	/*
3365	* Add backref node @cur into @cache.
3366	*
3367	* NOTE: Even if the function returned 0, @cur is not yet cached as its upper
3368	* links aren't yet bi-directional. Needs to finish such links.
3369	* Use btrfs_backref_finish_upper_links() to finish such linkage.
3370	*
3371	* @trans: Transaction handle.
3372	* @path: Released path for indirect tree backref lookup
3373	* @iter: Released backref iter for extent tree search
3374	* @node_key: The first key of the tree block
3375	*/
3376	int btrfs_backref_add_tree_node(struct btrfs_trans_handle *trans,
3377	struct btrfs_backref_cache *cache,
3378	struct btrfs_path *path,
3379	struct btrfs_backref_iter *iter,
3380	struct btrfs_key *node_key,
3381	struct btrfs_backref_node *cur)
3382	{
3383	struct btrfs_backref_edge *edge;
3384	struct btrfs_backref_node *exist;
3385	int ret;
3386
3387	ret = btrfs_backref_iter_start(iter, bytenr: cur->bytenr);
3388	if (ret < 0)
3389	return ret;
3390	/*
3391	* We skip the first btrfs_tree_block_info, as we don't use the key
3392	* stored in it, but fetch it from the tree block
3393	*/
3394	if (btrfs_backref_has_tree_block_info(iter)) {
3395	ret = btrfs_backref_iter_next(iter);
3396	if (ret < 0)
3397	goto out;
3398	/* No extra backref? This means the tree block is corrupted */
3399	if (ret > 0) {
3400	ret = -EUCLEAN;
3401	goto out;
3402	}
3403	}
3404	WARN_ON(cur->checked);
3405	if (!list_empty(head: &cur->upper)) {
3406	/*
3407	* The backref was added previously when processing backref of
3408	* type BTRFS_TREE_BLOCK_REF_KEY
3409	*/
3410	ASSERT(list_is_singular(&cur->upper));
3411	edge = list_entry(cur->upper.next, struct btrfs_backref_edge,
3412	list[LOWER]);
3413	ASSERT(list_empty(&edge->list[UPPER]));
3414	exist = edge->node[UPPER];
3415	/*
3416	* Add the upper level block to pending list if we need check
3417	* its backrefs
3418	*/
3419	if (!exist->checked)
3420	list_add_tail(new: &edge->list[UPPER], head: &cache->pending_edge);
3421	} else {
3422	exist = NULL;
3423	}
3424
3425	for (; ret == 0; ret = btrfs_backref_iter_next(iter)) {
3426	struct extent_buffer *eb;
3427	struct btrfs_key key;
3428	int type;
3429
3430	cond_resched();
3431	eb = btrfs_backref_get_eb(iter);
3432
3433	key.objectid = iter->bytenr;
3434	if (btrfs_backref_iter_is_inline_ref(iter)) {
3435	struct btrfs_extent_inline_ref *iref;
3436
3437	/* Update key for inline backref */
3438	iref = (struct btrfs_extent_inline_ref *)
3439	((unsigned long)iter->cur_ptr);
3440	type = btrfs_get_extent_inline_ref_type(eb, iref,
3441	is_data: BTRFS_REF_TYPE_BLOCK);
3442	if (type == BTRFS_REF_TYPE_INVALID) {
3443	ret = -EUCLEAN;
3444	goto out;
3445	}
3446	key.type = type;
3447	key.offset = btrfs_extent_inline_ref_offset(eb, s: iref);
3448	} else {
3449	key.type = iter->cur_key.type;
3450	key.offset = iter->cur_key.offset;
3451	}
3452
3453	/*
3454	* Parent node found and matches current inline ref, no need to
3455	* rebuild this node for this inline ref
3456	*/
3457	if (exist &&
3458	((key.type == BTRFS_TREE_BLOCK_REF_KEY &&
3459	exist->owner == key.offset) ||
3460	(key.type == BTRFS_SHARED_BLOCK_REF_KEY &&
3461	exist->bytenr == key.offset))) {
3462	exist = NULL;
3463	continue;
3464	}
3465
3466	/* SHARED_BLOCK_REF means key.offset is the parent bytenr */
3467	if (key.type == BTRFS_SHARED_BLOCK_REF_KEY) {
3468	ret = handle_direct_tree_backref(cache, ref_key: &key, cur);
3469	if (ret < 0)
3470	goto out;
3471	} else if (key.type == BTRFS_TREE_BLOCK_REF_KEY) {
3472	/*
3473	* key.type == BTRFS_TREE_BLOCK_REF_KEY, inline ref
3474	* offset means the root objectid. We need to search
3475	* the tree to get its parent bytenr.
3476	*/
3477	ret = handle_indirect_tree_backref(trans, cache, path,
3478	ref_key: &key, tree_key: node_key, cur);
3479	if (ret < 0)
3480	goto out;
3481	}
3482	/*
3483	* Unrecognized tree backref items (if it can pass tree-checker)
3484	* would be ignored.
3485	*/
3486	}
3487	ret = 0;
3488	cur->checked = 1;
3489	WARN_ON(exist);
3490	out:
3491	btrfs_backref_iter_release(iter);
3492	return ret;
3493	}
3494
3495	/*
3496	* Finish the upwards linkage created by btrfs_backref_add_tree_node()
3497	*/
3498	int btrfs_backref_finish_upper_links(struct btrfs_backref_cache *cache,
3499	struct btrfs_backref_node *start)
3500	{
3501	struct list_head *useless_node = &cache->useless_node;
3502	struct btrfs_backref_edge *edge;
3503	struct rb_node *rb_node;
3504	LIST_HEAD(pending_edge);
3505
3506	ASSERT(start->checked);
3507
3508	/* Insert this node to cache if it's not COW-only */
3509	if (!start->cowonly) {
3510	rb_node = rb_simple_insert(root: &cache->rb_root, bytenr: start->bytenr,
3511	node: &start->rb_node);
3512	if (rb_node)
3513	btrfs_backref_panic(fs_info: cache->fs_info, bytenr: start->bytenr,
3514	error: -EEXIST);
3515	list_add_tail(new: &start->lower, head: &cache->leaves);
3516	}
3517
3518	/*
3519	* Use breadth first search to iterate all related edges.
3520	*
3521	* The starting points are all the edges of this node
3522	*/
3523	list_for_each_entry(edge, &start->upper, list[LOWER])
3524	list_add_tail(new: &edge->list[UPPER], head: &pending_edge);
3525
3526	while (!list_empty(head: &pending_edge)) {
3527	struct btrfs_backref_node *upper;
3528	struct btrfs_backref_node *lower;
3529
3530	edge = list_first_entry(&pending_edge,
3531	struct btrfs_backref_edge, list[UPPER]);
3532	list_del_init(entry: &edge->list[UPPER]);
3533	upper = edge->node[UPPER];
3534	lower = edge->node[LOWER];
3535
3536	/* Parent is detached, no need to keep any edges */
3537	if (upper->detached) {
3538	list_del(entry: &edge->list[LOWER]);
3539	btrfs_backref_free_edge(cache, edge);
3540
3541	/* Lower node is orphan, queue for cleanup */
3542	if (list_empty(head: &lower->upper))
3543	list_add(new: &lower->list, head: useless_node);
3544	continue;
3545	}
3546
3547	/*
3548	* All new nodes added in current build_backref_tree() haven't
3549	* been linked to the cache rb tree.
3550	* So if we have upper->rb_node populated, this means a cache
3551	* hit. We only need to link the edge, as @upper and all its
3552	* parents have already been linked.
3553	*/
3554	if (!RB_EMPTY_NODE(&upper->rb_node)) {
3555	if (upper->lowest) {
3556	list_del_init(entry: &upper->lower);
3557	upper->lowest = 0;
3558	}
3559
3560	list_add_tail(new: &edge->list[UPPER], head: &upper->lower);
3561	continue;
3562	}
3563
3564	/* Sanity check, we shouldn't have any unchecked nodes */
3565	if (!upper->checked) {
3566	ASSERT(0);
3567	return -EUCLEAN;
3568	}
3569
3570	/* Sanity check, COW-only node has non-COW-only parent */
3571	if (start->cowonly != upper->cowonly) {
3572	ASSERT(0);
3573	return -EUCLEAN;
3574	}
3575
3576	/* Only cache non-COW-only (subvolume trees) tree blocks */
3577	if (!upper->cowonly) {
3578	rb_node = rb_simple_insert(root: &cache->rb_root, bytenr: upper->bytenr,
3579	node: &upper->rb_node);
3580	if (rb_node) {
3581	btrfs_backref_panic(fs_info: cache->fs_info,
3582	bytenr: upper->bytenr, error: -EEXIST);
3583	return -EUCLEAN;
3584	}
3585	}
3586
3587	list_add_tail(new: &edge->list[UPPER], head: &upper->lower);
3588
3589	/*
3590	* Also queue all the parent edges of this uncached node
3591	* to finish the upper linkage
3592	*/
3593	list_for_each_entry(edge, &upper->upper, list[LOWER])
3594	list_add_tail(new: &edge->list[UPPER], head: &pending_edge);
3595	}
3596	return 0;
3597	}
3598
3599	void btrfs_backref_error_cleanup(struct btrfs_backref_cache *cache,
3600	struct btrfs_backref_node *node)
3601	{
3602	struct btrfs_backref_node *lower;
3603	struct btrfs_backref_node *upper;
3604	struct btrfs_backref_edge *edge;
3605
3606	while (!list_empty(head: &cache->useless_node)) {
3607	lower = list_first_entry(&cache->useless_node,
3608	struct btrfs_backref_node, list);
3609	list_del_init(entry: &lower->list);
3610	}
3611	while (!list_empty(head: &cache->pending_edge)) {
3612	edge = list_first_entry(&cache->pending_edge,
3613	struct btrfs_backref_edge, list[UPPER]);
3614	list_del(entry: &edge->list[UPPER]);
3615	list_del(entry: &edge->list[LOWER]);
3616	lower = edge->node[LOWER];
3617	upper = edge->node[UPPER];
3618	btrfs_backref_free_edge(cache, edge);
3619
3620	/*
3621	* Lower is no longer linked to any upper backref nodes and
3622	* isn't in the cache, we can free it ourselves.
3623	*/
3624	if (list_empty(head: &lower->upper) &&
3625	RB_EMPTY_NODE(&lower->rb_node))
3626	list_add(new: &lower->list, head: &cache->useless_node);
3627
3628	if (!RB_EMPTY_NODE(&upper->rb_node))
3629	continue;
3630
3631	/* Add this guy's upper edges to the list to process */
3632	list_for_each_entry(edge, &upper->upper, list[LOWER])
3633	list_add_tail(new: &edge->list[UPPER],
3634	head: &cache->pending_edge);
3635	if (list_empty(head: &upper->upper))
3636	list_add(new: &upper->list, head: &cache->useless_node);
3637	}
3638
3639	while (!list_empty(head: &cache->useless_node)) {
3640	lower = list_first_entry(&cache->useless_node,
3641	struct btrfs_backref_node, list);
3642	list_del_init(entry: &lower->list);
3643	if (lower == node)
3644	node = NULL;
3645	btrfs_backref_drop_node(tree: cache, node: lower);
3646	}
3647
3648	btrfs_backref_cleanup_node(cache, node);
3649	ASSERT(list_empty(&cache->useless_node) &&
3650	list_empty(&cache->pending_edge));
3651	}
3652