fs/btrfs/backref.h

   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  */
 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
 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