1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * Copyright (C) 2011 STRATO. All rights reserved.
4 */
5
6#ifndef BTRFS_BACKREF_H
7#define BTRFS_BACKREF_H
8
9#include <linux/types.h>
10#include <linux/rbtree.h>
11#include <linux/list.h>
12#include <linux/slab.h>
13#include <uapi/linux/btrfs.h>
14#include <uapi/linux/btrfs_tree.h>
15#include "messages.h"
16#include "locking.h"
17#include "disk-io.h"
18#include "extent_io.h"
19#include "ctree.h"
20
21struct extent_inode_elem;
22struct ulist;
23struct btrfs_extent_item;
24struct btrfs_trans_handle;
25struct btrfs_fs_info;
26
27/*
28 * Used by implementations of iterate_extent_inodes_t (see definition below) to
29 * signal that backref iteration can stop immediately and no error happened.
30 * The value must be non-negative and must not be 0, 1 (which is a common return
31 * value from things like btrfs_search_slot() and used internally in the backref
32 * walking code) and different from BACKREF_FOUND_SHARED and
33 * BACKREF_FOUND_NOT_SHARED
34 */
35#define BTRFS_ITERATE_EXTENT_INODES_STOP 5
36
37/*
38 * Should return 0 if no errors happened and iteration of backrefs should
39 * continue. Can return BTRFS_ITERATE_EXTENT_INODES_STOP or any other non-zero
40 * value to immediately stop iteration and possibly signal an error back to
41 * the caller.
42 */
43typedef int (iterate_extent_inodes_t)(u64 inum, u64 offset, u64 num_bytes,
44 u64 root, void *ctx);
45
46/*
47 * Context and arguments for backref walking functions. Some of the fields are
48 * to be filled by the caller of such functions while other are filled by the
49 * functions themselves, as described below.
50 */
51struct btrfs_backref_walk_ctx {
52 /*
53 * The address of the extent for which we are doing backref walking.
54 * Can be either a data extent or a metadata extent.
55 *
56 * Must always be set by the top level caller.
57 */
58 u64 bytenr;
59 /*
60 * Offset relative to the target extent. This is only used for data
61 * extents, and it's meaningful because we can have file extent items
62 * that point only to a section of a data extent ("bookend" extents),
63 * and we want to filter out any that don't point to a section of the
64 * data extent containing the given offset.
65 *
66 * Must always be set by the top level caller.
67 */
68 u64 extent_item_pos;
69 /*
70 * If true and bytenr corresponds to a data extent, then references from
71 * all file extent items that point to the data extent are considered,
72 * @extent_item_pos is ignored.
73 */
74 bool ignore_extent_item_pos;
75 /*
76 * If true and bytenr corresponds to a data extent, then the inode list
77 * (each member describing inode number, file offset and root) is not
78 * added to each reference added to the @refs ulist.
79 */
80 bool skip_inode_ref_list;
81 /* A valid transaction handle or NULL. */
82 struct btrfs_trans_handle *trans;
83 /*
84 * The file system's info object, can not be NULL.
85 *
86 * Must always be set by the top level caller.
87 */
88 struct btrfs_fs_info *fs_info;
89 /*
90 * Time sequence acquired from btrfs_get_tree_mod_seq(), in case the
91 * caller joined the tree mod log to get a consistent view of b+trees
92 * while we do backref walking, or BTRFS_SEQ_LAST.
93 * When using BTRFS_SEQ_LAST, delayed refs are not checked and it uses
94 * commit roots when searching b+trees - this is a special case for
95 * qgroups used during a transaction commit.
96 */
97 u64 time_seq;
98 /*
99 * Used to collect the bytenr of metadata extents that point to the
100 * target extent.
101 */
102 struct ulist *refs;
103 /*
104 * List used to collect the IDs of the roots from which the target
105 * extent is accessible. Can be NULL in case the caller does not care
106 * about collecting root IDs.
107 */
108 struct ulist *roots;
109 /*
110 * Used by iterate_extent_inodes() and the main backref walk code
111 * (find_parent_nodes()). Lookup and store functions for an optional
112 * cache which maps the logical address (bytenr) of leaves to an array
113 * of root IDs.
114 */
115 bool (*cache_lookup)(u64 leaf_bytenr, void *user_ctx,
116 const u64 **root_ids_ret, int *root_count_ret);
117 void (*cache_store)(u64 leaf_bytenr, const struct ulist *root_ids,
118 void *user_ctx);
119 /*
120 * If this is not NULL, then the backref walking code will call this
121 * for each indirect data extent reference as soon as it finds one,
122 * before collecting all the remaining backrefs and before resolving
123 * indirect backrefs. This allows for the caller to terminate backref
124 * walking as soon as it finds one backref that matches some specific
125 * criteria. The @cache_lookup and @cache_store callbacks should not
126 * be NULL in order to use this callback.
127 */
128 iterate_extent_inodes_t *indirect_ref_iterator;
129 /*
130 * If this is not NULL, then the backref walking code will call this for
131 * each extent item it's meant to process before it actually starts
132 * processing it. If this returns anything other than 0, then it stops
133 * the backref walking code immediately.
134 */
135 int (*check_extent_item)(u64 bytenr, const struct btrfs_extent_item *ei,
136 const struct extent_buffer *leaf, void *user_ctx);
137 /*
138 * If this is not NULL, then the backref walking code will call this for
139 * each extent data ref it finds (BTRFS_EXTENT_DATA_REF_KEY keys) before
140 * processing that data ref. If this callback return false, then it will
141 * ignore this data ref and it will never resolve the indirect data ref,
142 * saving time searching for leaves in a fs tree with file extent items
143 * matching the data ref.
144 */
145 bool (*skip_data_ref)(u64 root, u64 ino, u64 offset, void *user_ctx);
146 /* Context object to pass to the callbacks defined above. */
147 void *user_ctx;
148};
149
150struct inode_fs_paths {
151 struct btrfs_path *btrfs_path;
152 struct btrfs_root *fs_root;
153 struct btrfs_data_container *fspath;
154};
155
156struct btrfs_backref_shared_cache_entry {
157 u64 bytenr;
158 u64 gen;
159 bool is_shared;
160};
161
162#define BTRFS_BACKREF_CTX_PREV_EXTENTS_SIZE 8
163
164struct btrfs_backref_share_check_ctx {
165 /* Ulists used during backref walking. */
166 struct ulist refs;
167 /*
168 * The current leaf the caller of btrfs_is_data_extent_shared() is at.
169 * Typically the caller (at the moment only fiemap) tries to determine
170 * the sharedness of data extents point by file extent items from entire
171 * leaves.
172 */
173 u64 curr_leaf_bytenr;
174 /*
175 * The previous leaf the caller was at in the previous call to
176 * btrfs_is_data_extent_shared(). This may be the same as the current
177 * leaf. On the first call it must be 0.
178 */
179 u64 prev_leaf_bytenr;
180 /*
181 * A path from a root to a leaf that has a file extent item pointing to
182 * a given data extent should never exceed the maximum b+tree height.
183 */
184 struct btrfs_backref_shared_cache_entry path_cache_entries[BTRFS_MAX_LEVEL];
185 bool use_path_cache;
186 /*
187 * Cache the sharedness result for the last few extents we have found,
188 * but only for extents for which we have multiple file extent items
189 * that point to them.
190 * It's very common to have several file extent items that point to the
191 * same extent (bytenr) but with different offsets and lengths. This
192 * typically happens for COW writes, partial writes into prealloc
193 * extents, NOCOW writes after snapshoting a root, hole punching or
194 * reflinking within the same file (less common perhaps).
195 * So keep a small cache with the lookup results for the extent pointed
196 * by the last few file extent items. This cache is checked, with a
197 * linear scan, whenever btrfs_is_data_extent_shared() is called, so
198 * it must be small so that it does not negatively affect performance in
199 * case we don't have multiple file extent items that point to the same
200 * data extent.
201 */
202 struct {
203 u64 bytenr;
204 bool is_shared;
205 } prev_extents_cache[BTRFS_BACKREF_CTX_PREV_EXTENTS_SIZE];
206 /*
207 * The slot in the prev_extents_cache array that will be used for
208 * storing the sharedness result of a new data extent.
209 */
210 int prev_extents_cache_slot;
211};
212
213struct btrfs_backref_share_check_ctx *btrfs_alloc_backref_share_check_ctx(void);
214void btrfs_free_backref_share_ctx(struct btrfs_backref_share_check_ctx *ctx);
215
216int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
217 struct btrfs_path *path, struct btrfs_key *found_key,
218 u64 *flags);
219
220int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
221 struct btrfs_key *key, struct btrfs_extent_item *ei,
222 u32 item_size, u64 *out_root, u8 *out_level);
223
224int iterate_extent_inodes(struct btrfs_backref_walk_ctx *ctx,
225 bool search_commit_root,
226 iterate_extent_inodes_t *iterate, void *user_ctx);
227
228int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
229 struct btrfs_path *path, void *ctx,
230 bool ignore_offset);
231
232int paths_from_inode(u64 inum, struct inode_fs_paths *ipath);
233
234int btrfs_find_all_leafs(struct btrfs_backref_walk_ctx *ctx);
235int btrfs_find_all_roots(struct btrfs_backref_walk_ctx *ctx,
236 bool skip_commit_root_sem);
237char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
238 u32 name_len, unsigned long name_off,
239 struct extent_buffer *eb_in, u64 parent,
240 char *dest, u32 size);
241
242struct btrfs_data_container *init_data_container(u32 total_bytes);
243struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
244 struct btrfs_path *path);
245void free_ipath(struct inode_fs_paths *ipath);
246
247int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
248 u64 start_off, struct btrfs_path *path,
249 struct btrfs_inode_extref **ret_extref,
250 u64 *found_off);
251int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
252 u64 extent_gen,
253 struct btrfs_backref_share_check_ctx *ctx);
254
255int __init btrfs_prelim_ref_init(void);
256void __cold btrfs_prelim_ref_exit(void);
257
258struct prelim_ref {
259 struct rb_node rbnode;
260 u64 root_id;
261 struct btrfs_key key_for_search;
262 u8 level;
263 int count;
264 struct extent_inode_elem *inode_list;
265 u64 parent;
266 u64 wanted_disk_byte;
267};
268
269/*
270 * Iterate backrefs of one extent.
271 *
272 * Now it only supports iteration of tree block in commit root.
273 */
274struct btrfs_backref_iter {
275 u64 bytenr;
276 struct btrfs_path *path;
277 struct btrfs_fs_info *fs_info;
278 struct btrfs_key cur_key;
279 u32 item_ptr;
280 u32 cur_ptr;
281 u32 end_ptr;
282};
283
284struct btrfs_backref_iter *btrfs_backref_iter_alloc(struct btrfs_fs_info *fs_info);
285
286/*
287 * For metadata with EXTENT_ITEM key (non-skinny) case, the first inline data
288 * is btrfs_tree_block_info, without a btrfs_extent_inline_ref header.
289 *
290 * This helper determines if that's the case.
291 */
292static inline bool btrfs_backref_has_tree_block_info(
293 struct btrfs_backref_iter *iter)
294{
295 if (iter->cur_key.type == BTRFS_EXTENT_ITEM_KEY &&
296 iter->cur_ptr - iter->item_ptr == sizeof(struct btrfs_extent_item))
297 return true;
298 return false;
299}
300
301int btrfs_backref_iter_start(struct btrfs_backref_iter *iter, u64 bytenr);
302
303int btrfs_backref_iter_next(struct btrfs_backref_iter *iter);
304
305/*
306 * Backref cache related structures
307 *
308 * The whole objective of backref_cache is to build a bi-directional map
309 * of tree blocks (represented by backref_node) and all their parents.
310 */
311
312/*
313 * Represent a tree block in the backref cache
314 */
315struct btrfs_backref_node {
316 struct {
317 struct rb_node rb_node;
318 u64 bytenr;
319 }; /* Use rb_simple_node for search/insert */
320
321 /*
322 * This is a sanity check, whenever we COW a block we will update
323 * new_bytenr with it's current location, and we will check this in
324 * various places to validate that the cache makes sense, it shouldn't
325 * be used for anything else.
326 */
327 u64 new_bytenr;
328 /* Objectid of tree block owner, can be not uptodate */
329 u64 owner;
330 /* Link to pending, changed or detached list */
331 struct list_head list;
332
333 /* List of upper level edges, which link this node to its parents */
334 struct list_head upper;
335 /* List of lower level edges, which link this node to its children */
336 struct list_head lower;
337
338 /* NULL if this node is not tree root */
339 struct btrfs_root *root;
340 /* Extent buffer got by COWing the block */
341 struct extent_buffer *eb;
342 /* Level of the tree block */
343 unsigned int level:8;
344 /* Is the extent buffer locked */
345 unsigned int locked:1;
346 /* Has the block been processed */
347 unsigned int processed:1;
348 /* Have backrefs of this block been checked */
349 unsigned int checked:1;
350 /*
351 * 1 if corresponding block has been COWed but some upper level block
352 * pointers may not point to the new location
353 */
354 unsigned int pending:1;
355 /* 1 if the backref node isn't connected to any other backref node */
356 unsigned int detached:1;
357
358 /*
359 * For generic purpose backref cache, where we only care if it's a reloc
360 * root, doesn't care the source subvolid.
361 */
362 unsigned int is_reloc_root:1;
363};
364
365#define LOWER 0
366#define UPPER 1
367
368/*
369 * Represent an edge connecting upper and lower backref nodes.
370 */
371struct btrfs_backref_edge {
372 /*
373 * list[LOWER] is linked to btrfs_backref_node::upper of lower level
374 * node, and list[UPPER] is linked to btrfs_backref_node::lower of
375 * upper level node.
376 *
377 * Also, build_backref_tree() uses list[UPPER] for pending edges, before
378 * linking list[UPPER] to its upper level nodes.
379 */
380 struct list_head list[2];
381
382 /* Two related nodes */
383 struct btrfs_backref_node *node[2];
384};
385
386struct btrfs_backref_cache {
387 /* Red black tree of all backref nodes in the cache */
388 struct rb_root rb_root;
389 /* For passing backref nodes to btrfs_reloc_cow_block */
390 struct btrfs_backref_node *path[BTRFS_MAX_LEVEL];
391 /*
392 * List of blocks that have been COWed but some block pointers in upper
393 * level blocks may not reflect the new location
394 */
395 struct list_head pending[BTRFS_MAX_LEVEL];
396
397 u64 last_trans;
398
399 int nr_nodes;
400 int nr_edges;
401
402 /* List of unchecked backref edges during backref cache build */
403 struct list_head pending_edge;
404
405 /* List of useless backref nodes during backref cache build */
406 struct list_head useless_node;
407
408 struct btrfs_fs_info *fs_info;
409
410 /*
411 * Whether this cache is for relocation
412 *
413 * Reloction backref cache require more info for reloc root compared
414 * to generic backref cache.
415 */
416 bool is_reloc;
417};
418
419void btrfs_backref_init_cache(struct btrfs_fs_info *fs_info,
420 struct btrfs_backref_cache *cache, bool is_reloc);
421struct btrfs_backref_node *btrfs_backref_alloc_node(
422 struct btrfs_backref_cache *cache, u64 bytenr, int level);
423struct btrfs_backref_edge *btrfs_backref_alloc_edge(
424 struct btrfs_backref_cache *cache);
425
426#define LINK_LOWER (1U << 0)
427#define LINK_UPPER (1U << 1)
428
429void btrfs_backref_link_edge(struct btrfs_backref_edge *edge,
430 struct btrfs_backref_node *lower,
431 struct btrfs_backref_node *upper,
432 int link_which);
433void btrfs_backref_free_node(struct btrfs_backref_cache *cache,
434 struct btrfs_backref_node *node);
435void btrfs_backref_free_edge(struct btrfs_backref_cache *cache,
436 struct btrfs_backref_edge *edge);
437void btrfs_backref_unlock_node_buffer(struct btrfs_backref_node *node);
438void btrfs_backref_drop_node_buffer(struct btrfs_backref_node *node);
439
440void btrfs_backref_cleanup_node(struct btrfs_backref_cache *cache,
441 struct btrfs_backref_node *node);
442void btrfs_backref_drop_node(struct btrfs_backref_cache *tree,
443 struct btrfs_backref_node *node);
444
445void btrfs_backref_release_cache(struct btrfs_backref_cache *cache);
446
447static inline void btrfs_backref_panic(struct btrfs_fs_info *fs_info,
448 u64 bytenr, int error)
449{
450 btrfs_panic(fs_info, error,
451 "Inconsistency in backref cache found at offset %llu",
452 bytenr);
453}
454
455int btrfs_backref_add_tree_node(struct btrfs_trans_handle *trans,
456 struct btrfs_backref_cache *cache,
457 struct btrfs_path *path,
458 struct btrfs_backref_iter *iter,
459 struct btrfs_key *node_key,
460 struct btrfs_backref_node *cur);
461
462int btrfs_backref_finish_upper_links(struct btrfs_backref_cache *cache,
463 struct btrfs_backref_node *start);
464
465void btrfs_backref_error_cleanup(struct btrfs_backref_cache *cache,
466 struct btrfs_backref_node *node);
467
468#endif
469

source code of linux/fs/btrfs/backref.h