xref: /linux/fs/btrfs/backref.h (revision 79790b6818e96c58fe2bffee1b418c16e64e7b80)
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 
21 struct extent_inode_elem;
22 struct ulist;
23 struct btrfs_extent_item;
24 struct btrfs_trans_handle;
25 struct 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  */
43 typedef 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  */
51 struct 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 
150 struct inode_fs_paths {
151 	struct btrfs_path		*btrfs_path;
152 	struct btrfs_root		*fs_root;
153 	struct btrfs_data_container	*fspath;
154 };
155 
156 struct 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 
164 struct 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 
213 struct btrfs_backref_share_check_ctx *btrfs_alloc_backref_share_check_ctx(void);
214 void btrfs_free_backref_share_ctx(struct btrfs_backref_share_check_ctx *ctx);
215 
216 int 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 
220 int 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 
224 int iterate_extent_inodes(struct btrfs_backref_walk_ctx *ctx,
225 			  bool search_commit_root,
226 			  iterate_extent_inodes_t *iterate, void *user_ctx);
227 
228 int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
229 				struct btrfs_path *path, void *ctx,
230 				bool ignore_offset);
231 
232 int paths_from_inode(u64 inum, struct inode_fs_paths *ipath);
233 
234 int btrfs_find_all_leafs(struct btrfs_backref_walk_ctx *ctx);
235 int btrfs_find_all_roots(struct btrfs_backref_walk_ctx *ctx,
236 			 bool skip_commit_root_sem);
237 char *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 
242 struct btrfs_data_container *init_data_container(u32 total_bytes);
243 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
244 					struct btrfs_path *path);
245 void free_ipath(struct inode_fs_paths *ipath);
246 
247 int 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);
251 int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
252 				u64 extent_gen,
253 				struct btrfs_backref_share_check_ctx *ctx);
254 
255 int __init btrfs_prelim_ref_init(void);
256 void __cold btrfs_prelim_ref_exit(void);
257 
258 struct 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  */
274 struct 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 
284 struct 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  */
btrfs_backref_has_tree_block_info(struct btrfs_backref_iter * iter)292 static 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 
301 int btrfs_backref_iter_start(struct btrfs_backref_iter *iter, u64 bytenr);
302 
303 int 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  */
315 struct btrfs_backref_node {
316 	struct {
317 		struct rb_node rb_node;
318 		u64 bytenr;
319 	}; /* Use rb_simple_node for search/insert */
320 
321 	u64 new_bytenr;
322 	/* Objectid of tree block owner, can be not uptodate */
323 	u64 owner;
324 	/* Link to pending, changed or detached list */
325 	struct list_head list;
326 
327 	/* List of upper level edges, which link this node to its parents */
328 	struct list_head upper;
329 	/* List of lower level edges, which link this node to its children */
330 	struct list_head lower;
331 
332 	/* NULL if this node is not tree root */
333 	struct btrfs_root *root;
334 	/* Extent buffer got by COWing the block */
335 	struct extent_buffer *eb;
336 	/* Level of the tree block */
337 	unsigned int level:8;
338 	/* Is the block in a non-shareable tree */
339 	unsigned int cowonly:1;
340 	/* 1 if no child node is in the cache */
341 	unsigned int lowest:1;
342 	/* Is the extent buffer locked */
343 	unsigned int locked:1;
344 	/* Has the block been processed */
345 	unsigned int processed:1;
346 	/* Have backrefs of this block been checked */
347 	unsigned int checked:1;
348 	/*
349 	 * 1 if corresponding block has been COWed but some upper level block
350 	 * pointers may not point to the new location
351 	 */
352 	unsigned int pending:1;
353 	/* 1 if the backref node isn't connected to any other backref node */
354 	unsigned int detached:1;
355 
356 	/*
357 	 * For generic purpose backref cache, where we only care if it's a reloc
358 	 * root, doesn't care the source subvolid.
359 	 */
360 	unsigned int is_reloc_root:1;
361 };
362 
363 #define LOWER	0
364 #define UPPER	1
365 
366 /*
367  * Represent an edge connecting upper and lower backref nodes.
368  */
369 struct btrfs_backref_edge {
370 	/*
371 	 * list[LOWER] is linked to btrfs_backref_node::upper of lower level
372 	 * node, and list[UPPER] is linked to btrfs_backref_node::lower of
373 	 * upper level node.
374 	 *
375 	 * Also, build_backref_tree() uses list[UPPER] for pending edges, before
376 	 * linking list[UPPER] to its upper level nodes.
377 	 */
378 	struct list_head list[2];
379 
380 	/* Two related nodes */
381 	struct btrfs_backref_node *node[2];
382 };
383 
384 struct btrfs_backref_cache {
385 	/* Red black tree of all backref nodes in the cache */
386 	struct rb_root rb_root;
387 	/* For passing backref nodes to btrfs_reloc_cow_block */
388 	struct btrfs_backref_node *path[BTRFS_MAX_LEVEL];
389 	/*
390 	 * List of blocks that have been COWed but some block pointers in upper
391 	 * level blocks may not reflect the new location
392 	 */
393 	struct list_head pending[BTRFS_MAX_LEVEL];
394 	/* List of backref nodes with no child node */
395 	struct list_head leaves;
396 	/* List of blocks that have been COWed in current transaction */
397 	struct list_head changed;
398 	/* List of detached backref node. */
399 	struct list_head detached;
400 
401 	u64 last_trans;
402 
403 	int nr_nodes;
404 	int nr_edges;
405 
406 	/* List of unchecked backref edges during backref cache build */
407 	struct list_head pending_edge;
408 
409 	/* List of useless backref nodes during backref cache build */
410 	struct list_head useless_node;
411 
412 	struct btrfs_fs_info *fs_info;
413 
414 	/*
415 	 * Whether this cache is for relocation
416 	 *
417 	 * Reloction backref cache require more info for reloc root compared
418 	 * to generic backref cache.
419 	 */
420 	bool is_reloc;
421 };
422 
423 void btrfs_backref_init_cache(struct btrfs_fs_info *fs_info,
424 			      struct btrfs_backref_cache *cache, bool is_reloc);
425 struct btrfs_backref_node *btrfs_backref_alloc_node(
426 		struct btrfs_backref_cache *cache, u64 bytenr, int level);
427 struct btrfs_backref_edge *btrfs_backref_alloc_edge(
428 		struct btrfs_backref_cache *cache);
429 
430 #define		LINK_LOWER	(1 << 0)
431 #define		LINK_UPPER	(1 << 1)
432 
433 void btrfs_backref_link_edge(struct btrfs_backref_edge *edge,
434 			     struct btrfs_backref_node *lower,
435 			     struct btrfs_backref_node *upper,
436 			     int link_which);
437 void btrfs_backref_free_node(struct btrfs_backref_cache *cache,
438 			     struct btrfs_backref_node *node);
439 void btrfs_backref_free_edge(struct btrfs_backref_cache *cache,
440 			     struct btrfs_backref_edge *edge);
441 void btrfs_backref_unlock_node_buffer(struct btrfs_backref_node *node);
442 void btrfs_backref_drop_node_buffer(struct btrfs_backref_node *node);
443 
444 void btrfs_backref_cleanup_node(struct btrfs_backref_cache *cache,
445 				struct btrfs_backref_node *node);
446 void btrfs_backref_drop_node(struct btrfs_backref_cache *tree,
447 			     struct btrfs_backref_node *node);
448 
449 void btrfs_backref_release_cache(struct btrfs_backref_cache *cache);
450 
btrfs_backref_panic(struct btrfs_fs_info * fs_info,u64 bytenr,int error)451 static inline void btrfs_backref_panic(struct btrfs_fs_info *fs_info,
452 				       u64 bytenr, int error)
453 {
454 	btrfs_panic(fs_info, error,
455 		    "Inconsistency in backref cache found at offset %llu",
456 		    bytenr);
457 }
458 
459 int btrfs_backref_add_tree_node(struct btrfs_trans_handle *trans,
460 				struct btrfs_backref_cache *cache,
461 				struct btrfs_path *path,
462 				struct btrfs_backref_iter *iter,
463 				struct btrfs_key *node_key,
464 				struct btrfs_backref_node *cur);
465 
466 int btrfs_backref_finish_upper_links(struct btrfs_backref_cache *cache,
467 				     struct btrfs_backref_node *start);
468 
469 void btrfs_backref_error_cleanup(struct btrfs_backref_cache *cache,
470 				 struct btrfs_backref_node *node);
471 
472 #endif
473