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diff --git a/fs/btrfs/backref.h b/fs/btrfs/backref.h
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+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2011 STRATO. All rights reserved.
+ */
+
+#ifndef BTRFS_BACKREF_H
+#define BTRFS_BACKREF_H
+
+#include <linux/btrfs.h>
+#include "messages.h"
+#include "ulist.h"
+#include "disk-io.h"
+#include "extent_io.h"
+
+/*
+ * Used by implementations of iterate_extent_inodes_t (see definition below) to
+ * signal that backref iteration can stop immediately and no error happened.
+ * The value must be non-negative and must not be 0, 1 (which is a common return
+ * value from things like btrfs_search_slot() and used internally in the backref
+ * walking code) and different from BACKREF_FOUND_SHARED and
+ * BACKREF_FOUND_NOT_SHARED
+ */
+#define BTRFS_ITERATE_EXTENT_INODES_STOP 5
+
+/*
+ * Should return 0 if no errors happened and iteration of backrefs should
+ * continue. Can return BTRFS_ITERATE_EXTENT_INODES_STOP or any other non-zero
+ * value to immediately stop iteration and possibly signal an error back to
+ * the caller.
+ */
+typedef int (iterate_extent_inodes_t)(u64 inum, u64 offset, u64 num_bytes,
+ u64 root, void *ctx);
+
+/*
+ * Context and arguments for backref walking functions. Some of the fields are
+ * to be filled by the caller of such functions while other are filled by the
+ * functions themselves, as described below.
+ */
+struct btrfs_backref_walk_ctx {
+ /*
+ * The address of the extent for which we are doing backref walking.
+ * Can be either a data extent or a metadata extent.
+ *
+ * Must always be set by the top level caller.
+ */
+ u64 bytenr;
+ /*
+ * Offset relative to the target extent. This is only used for data
+ * extents, and it's meaningful because we can have file extent items
+ * that point only to a section of a data extent ("bookend" extents),
+ * and we want to filter out any that don't point to a section of the
+ * data extent containing the given offset.
+ *
+ * Must always be set by the top level caller.
+ */
+ u64 extent_item_pos;
+ /*
+ * If true and bytenr corresponds to a data extent, then references from
+ * all file extent items that point to the data extent are considered,
+ * @extent_item_pos is ignored.
+ */
+ bool ignore_extent_item_pos;
+ /*
+ * If true and bytenr corresponds to a data extent, then the inode list
+ * (each member describing inode number, file offset and root) is not
+ * added to each reference added to the @refs ulist.
+ */
+ bool skip_inode_ref_list;
+ /* A valid transaction handle or NULL. */
+ struct btrfs_trans_handle *trans;
+ /*
+ * The file system's info object, can not be NULL.
+ *
+ * Must always be set by the top level caller.
+ */
+ struct btrfs_fs_info *fs_info;
+ /*
+ * Time sequence acquired from btrfs_get_tree_mod_seq(), in case the
+ * caller joined the tree mod log to get a consistent view of b+trees
+ * while we do backref walking, or BTRFS_SEQ_LAST.
+ * When using BTRFS_SEQ_LAST, delayed refs are not checked and it uses
+ * commit roots when searching b+trees - this is a special case for
+ * qgroups used during a transaction commit.
+ */
+ u64 time_seq;
+ /*
+ * Used to collect the bytenr of metadata extents that point to the
+ * target extent.
+ */
+ struct ulist *refs;
+ /*
+ * List used to collect the IDs of the roots from which the target
+ * extent is accessible. Can be NULL in case the caller does not care
+ * about collecting root IDs.
+ */
+ struct ulist *roots;
+ /*
+ * Used by iterate_extent_inodes() and the main backref walk code
+ * (find_parent_nodes()). Lookup and store functions for an optional
+ * cache which maps the logical address (bytenr) of leaves to an array
+ * of root IDs.
+ */
+ bool (*cache_lookup)(u64 leaf_bytenr, void *user_ctx,
+ const u64 **root_ids_ret, int *root_count_ret);
+ void (*cache_store)(u64 leaf_bytenr, const struct ulist *root_ids,
+ void *user_ctx);
+ /*
+ * If this is not NULL, then the backref walking code will call this
+ * for each indirect data extent reference as soon as it finds one,
+ * before collecting all the remaining backrefs and before resolving
+ * indirect backrefs. This allows for the caller to terminate backref
+ * walking as soon as it finds one backref that matches some specific
+ * criteria. The @cache_lookup and @cache_store callbacks should not
+ * be NULL in order to use this callback.
+ */
+ iterate_extent_inodes_t *indirect_ref_iterator;
+ /*
+ * If this is not NULL, then the backref walking code will call this for
+ * each extent item it's meant to process before it actually starts
+ * processing it. If this returns anything other than 0, then it stops
+ * the backref walking code immediately.
+ */
+ int (*check_extent_item)(u64 bytenr, const struct btrfs_extent_item *ei,
+ const struct extent_buffer *leaf, void *user_ctx);
+ /*
+ * If this is not NULL, then the backref walking code will call this for
+ * each extent data ref it finds (BTRFS_EXTENT_DATA_REF_KEY keys) before
+ * processing that data ref. If this callback return false, then it will
+ * ignore this data ref and it will never resolve the indirect data ref,
+ * saving time searching for leaves in a fs tree with file extent items
+ * matching the data ref.
+ */
+ bool (*skip_data_ref)(u64 root, u64 ino, u64 offset, void *user_ctx);
+ /* Context object to pass to the callbacks defined above. */
+ void *user_ctx;
+};
+
+struct inode_fs_paths {
+ struct btrfs_path *btrfs_path;
+ struct btrfs_root *fs_root;
+ struct btrfs_data_container *fspath;
+};
+
+struct btrfs_backref_shared_cache_entry {
+ u64 bytenr;
+ u64 gen;
+ bool is_shared;
+};
+
+#define BTRFS_BACKREF_CTX_PREV_EXTENTS_SIZE 8
+
+struct btrfs_backref_share_check_ctx {
+ /* Ulists used during backref walking. */
+ struct ulist refs;
+ /*
+ * The current leaf the caller of btrfs_is_data_extent_shared() is at.
+ * Typically the caller (at the moment only fiemap) tries to determine
+ * the sharedness of data extents point by file extent items from entire
+ * leaves.
+ */
+ u64 curr_leaf_bytenr;
+ /*
+ * The previous leaf the caller was at in the previous call to
+ * btrfs_is_data_extent_shared(). This may be the same as the current
+ * leaf. On the first call it must be 0.
+ */
+ u64 prev_leaf_bytenr;
+ /*
+ * A path from a root to a leaf that has a file extent item pointing to
+ * a given data extent should never exceed the maximum b+tree height.
+ */
+ struct btrfs_backref_shared_cache_entry path_cache_entries[BTRFS_MAX_LEVEL];
+ bool use_path_cache;
+ /*
+ * Cache the sharedness result for the last few extents we have found,
+ * but only for extents for which we have multiple file extent items
+ * that point to them.
+ * It's very common to have several file extent items that point to the
+ * same extent (bytenr) but with different offsets and lengths. This
+ * typically happens for COW writes, partial writes into prealloc
+ * extents, NOCOW writes after snapshoting a root, hole punching or
+ * reflinking within the same file (less common perhaps).
+ * So keep a small cache with the lookup results for the extent pointed
+ * by the last few file extent items. This cache is checked, with a
+ * linear scan, whenever btrfs_is_data_extent_shared() is called, so
+ * it must be small so that it does not negatively affect performance in
+ * case we don't have multiple file extent items that point to the same
+ * data extent.
+ */
+ struct {
+ u64 bytenr;
+ bool is_shared;
+ } prev_extents_cache[BTRFS_BACKREF_CTX_PREV_EXTENTS_SIZE];
+ /*
+ * The slot in the prev_extents_cache array that will be used for
+ * storing the sharedness result of a new data extent.
+ */
+ int prev_extents_cache_slot;
+};
+
+struct btrfs_backref_share_check_ctx *btrfs_alloc_backref_share_check_ctx(void);
+void btrfs_free_backref_share_ctx(struct btrfs_backref_share_check_ctx *ctx);
+
+int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
+ struct btrfs_path *path, struct btrfs_key *found_key,
+ u64 *flags);
+
+int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
+ struct btrfs_key *key, struct btrfs_extent_item *ei,
+ u32 item_size, u64 *out_root, u8 *out_level);
+
+int iterate_extent_inodes(struct btrfs_backref_walk_ctx *ctx,
+ bool search_commit_root,
+ iterate_extent_inodes_t *iterate, void *user_ctx);
+
+int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
+ struct btrfs_path *path, void *ctx,
+ bool ignore_offset);
+
+int paths_from_inode(u64 inum, struct inode_fs_paths *ipath);
+
+int btrfs_find_all_leafs(struct btrfs_backref_walk_ctx *ctx);
+int btrfs_find_all_roots(struct btrfs_backref_walk_ctx *ctx,
+ bool skip_commit_root_sem);
+char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
+ u32 name_len, unsigned long name_off,
+ struct extent_buffer *eb_in, u64 parent,
+ char *dest, u32 size);
+
+struct btrfs_data_container *init_data_container(u32 total_bytes);
+struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
+ struct btrfs_path *path);
+void free_ipath(struct inode_fs_paths *ipath);
+
+int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
+ u64 start_off, struct btrfs_path *path,
+ struct btrfs_inode_extref **ret_extref,
+ u64 *found_off);
+int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
+ u64 extent_gen,
+ struct btrfs_backref_share_check_ctx *ctx);
+
+int __init btrfs_prelim_ref_init(void);
+void __cold btrfs_prelim_ref_exit(void);
+
+struct prelim_ref {
+ struct rb_node rbnode;
+ u64 root_id;
+ struct btrfs_key key_for_search;
+ int level;
+ int count;
+ struct extent_inode_elem *inode_list;
+ u64 parent;
+ u64 wanted_disk_byte;
+};
+
+/*
+ * Iterate backrefs of one extent.
+ *
+ * Now it only supports iteration of tree block in commit root.
+ */
+struct btrfs_backref_iter {
+ u64 bytenr;
+ struct btrfs_path *path;
+ struct btrfs_fs_info *fs_info;
+ struct btrfs_key cur_key;
+ u32 item_ptr;
+ u32 cur_ptr;
+ u32 end_ptr;
+};
+
+struct btrfs_backref_iter *btrfs_backref_iter_alloc(struct btrfs_fs_info *fs_info);
+
+static inline void btrfs_backref_iter_free(struct btrfs_backref_iter *iter)
+{
+ if (!iter)
+ return;
+ btrfs_free_path(iter->path);
+ kfree(iter);
+}
+
+static inline struct extent_buffer *btrfs_backref_get_eb(
+ struct btrfs_backref_iter *iter)
+{
+ if (!iter)
+ return NULL;
+ return iter->path->nodes[0];
+}
+
+/*
+ * For metadata with EXTENT_ITEM key (non-skinny) case, the first inline data
+ * is btrfs_tree_block_info, without a btrfs_extent_inline_ref header.
+ *
+ * This helper determines if that's the case.
+ */
+static inline bool btrfs_backref_has_tree_block_info(
+ struct btrfs_backref_iter *iter)
+{
+ if (iter->cur_key.type == BTRFS_EXTENT_ITEM_KEY &&
+ iter->cur_ptr - iter->item_ptr == sizeof(struct btrfs_extent_item))
+ return true;
+ return false;
+}
+
+int btrfs_backref_iter_start(struct btrfs_backref_iter *iter, u64 bytenr);
+
+int btrfs_backref_iter_next(struct btrfs_backref_iter *iter);
+
+static inline bool btrfs_backref_iter_is_inline_ref(
+ struct btrfs_backref_iter *iter)
+{
+ if (iter->cur_key.type == BTRFS_EXTENT_ITEM_KEY ||
+ iter->cur_key.type == BTRFS_METADATA_ITEM_KEY)
+ return true;
+ return false;
+}
+
+static inline void btrfs_backref_iter_release(struct btrfs_backref_iter *iter)
+{
+ iter->bytenr = 0;
+ iter->item_ptr = 0;
+ iter->cur_ptr = 0;
+ iter->end_ptr = 0;
+ btrfs_release_path(iter->path);
+ memset(&iter->cur_key, 0, sizeof(iter->cur_key));
+}
+
+/*
+ * Backref cache related structures
+ *
+ * The whole objective of backref_cache is to build a bi-directional map
+ * of tree blocks (represented by backref_node) and all their parents.
+ */
+
+/*
+ * Represent a tree block in the backref cache
+ */
+struct btrfs_backref_node {
+ struct {
+ struct rb_node rb_node;
+ u64 bytenr;
+ }; /* Use rb_simple_node for search/insert */
+
+ u64 new_bytenr;
+ /* Objectid of tree block owner, can be not uptodate */
+ u64 owner;
+ /* Link to pending, changed or detached list */
+ struct list_head list;
+
+ /* List of upper level edges, which link this node to its parents */
+ struct list_head upper;
+ /* List of lower level edges, which link this node to its children */
+ struct list_head lower;
+
+ /* NULL if this node is not tree root */
+ struct btrfs_root *root;
+ /* Extent buffer got by COWing the block */
+ struct extent_buffer *eb;
+ /* Level of the tree block */
+ unsigned int level:8;
+ /* Is the block in a non-shareable tree */
+ unsigned int cowonly:1;
+ /* 1 if no child node is in the cache */
+ unsigned int lowest:1;
+ /* Is the extent buffer locked */
+ unsigned int locked:1;
+ /* Has the block been processed */
+ unsigned int processed:1;
+ /* Have backrefs of this block been checked */
+ unsigned int checked:1;
+ /*
+ * 1 if corresponding block has been COWed but some upper level block
+ * pointers may not point to the new location
+ */
+ unsigned int pending:1;
+ /* 1 if the backref node isn't connected to any other backref node */
+ unsigned int detached:1;
+
+ /*
+ * For generic purpose backref cache, where we only care if it's a reloc
+ * root, doesn't care the source subvolid.
+ */
+ unsigned int is_reloc_root:1;
+};
+
+#define LOWER 0
+#define UPPER 1
+
+/*
+ * Represent an edge connecting upper and lower backref nodes.
+ */
+struct btrfs_backref_edge {
+ /*
+ * list[LOWER] is linked to btrfs_backref_node::upper of lower level
+ * node, and list[UPPER] is linked to btrfs_backref_node::lower of
+ * upper level node.
+ *
+ * Also, build_backref_tree() uses list[UPPER] for pending edges, before
+ * linking list[UPPER] to its upper level nodes.
+ */
+ struct list_head list[2];
+
+ /* Two related nodes */
+ struct btrfs_backref_node *node[2];
+};
+
+struct btrfs_backref_cache {
+ /* Red black tree of all backref nodes in the cache */
+ struct rb_root rb_root;
+ /* For passing backref nodes to btrfs_reloc_cow_block */
+ struct btrfs_backref_node *path[BTRFS_MAX_LEVEL];
+ /*
+ * List of blocks that have been COWed but some block pointers in upper
+ * level blocks may not reflect the new location
+ */
+ struct list_head pending[BTRFS_MAX_LEVEL];
+ /* List of backref nodes with no child node */
+ struct list_head leaves;
+ /* List of blocks that have been COWed in current transaction */
+ struct list_head changed;
+ /* List of detached backref node. */
+ struct list_head detached;
+
+ u64 last_trans;
+
+ int nr_nodes;
+ int nr_edges;
+
+ /* List of unchecked backref edges during backref cache build */
+ struct list_head pending_edge;
+
+ /* List of useless backref nodes during backref cache build */
+ struct list_head useless_node;
+
+ struct btrfs_fs_info *fs_info;
+
+ /*
+ * Whether this cache is for relocation
+ *
+ * Reloction backref cache require more info for reloc root compared
+ * to generic backref cache.
+ */
+ unsigned int is_reloc;
+};
+
+void btrfs_backref_init_cache(struct btrfs_fs_info *fs_info,
+ struct btrfs_backref_cache *cache, int is_reloc);
+struct btrfs_backref_node *btrfs_backref_alloc_node(
+ struct btrfs_backref_cache *cache, u64 bytenr, int level);
+struct btrfs_backref_edge *btrfs_backref_alloc_edge(
+ struct btrfs_backref_cache *cache);
+
+#define LINK_LOWER (1 << 0)
+#define LINK_UPPER (1 << 1)
+static inline void btrfs_backref_link_edge(struct btrfs_backref_edge *edge,
+ struct btrfs_backref_node *lower,
+ struct btrfs_backref_node *upper,
+ int link_which)
+{
+ ASSERT(upper && lower && upper->level == lower->level + 1);
+ edge->node[LOWER] = lower;
+ edge->node[UPPER] = upper;
+ if (link_which & LINK_LOWER)
+ list_add_tail(&edge->list[LOWER], &lower->upper);
+ if (link_which & LINK_UPPER)
+ list_add_tail(&edge->list[UPPER], &upper->lower);
+}
+
+static inline void btrfs_backref_free_node(struct btrfs_backref_cache *cache,
+ struct btrfs_backref_node *node)
+{
+ if (node) {
+ ASSERT(list_empty(&node->list));
+ ASSERT(list_empty(&node->lower));
+ ASSERT(node->eb == NULL);
+ cache->nr_nodes--;
+ btrfs_put_root(node->root);
+ kfree(node);
+ }
+}
+
+static inline void btrfs_backref_free_edge(struct btrfs_backref_cache *cache,
+ struct btrfs_backref_edge *edge)
+{
+ if (edge) {
+ cache->nr_edges--;
+ kfree(edge);
+ }
+}
+
+static inline void btrfs_backref_unlock_node_buffer(
+ struct btrfs_backref_node *node)
+{
+ if (node->locked) {
+ btrfs_tree_unlock(node->eb);
+ node->locked = 0;
+ }
+}
+
+static inline void btrfs_backref_drop_node_buffer(
+ struct btrfs_backref_node *node)
+{
+ if (node->eb) {
+ btrfs_backref_unlock_node_buffer(node);
+ free_extent_buffer(node->eb);
+ node->eb = NULL;
+ }
+}
+
+/*
+ * Drop the backref node from cache without cleaning up its children
+ * edges.
+ *
+ * This can only be called on node without parent edges.
+ * The children edges are still kept as is.
+ */
+static inline void btrfs_backref_drop_node(struct btrfs_backref_cache *tree,
+ struct btrfs_backref_node *node)
+{
+ ASSERT(list_empty(&node->upper));
+
+ btrfs_backref_drop_node_buffer(node);
+ list_del_init(&node->list);
+ list_del_init(&node->lower);
+ if (!RB_EMPTY_NODE(&node->rb_node))
+ rb_erase(&node->rb_node, &tree->rb_root);
+ btrfs_backref_free_node(tree, node);
+}
+
+void btrfs_backref_cleanup_node(struct btrfs_backref_cache *cache,
+ struct btrfs_backref_node *node);
+
+void btrfs_backref_release_cache(struct btrfs_backref_cache *cache);
+
+static inline void btrfs_backref_panic(struct btrfs_fs_info *fs_info,
+ u64 bytenr, int errno)
+{
+ btrfs_panic(fs_info, errno,
+ "Inconsistency in backref cache found at offset %llu",
+ bytenr);
+}
+
+int btrfs_backref_add_tree_node(struct btrfs_trans_handle *trans,
+ struct btrfs_backref_cache *cache,
+ struct btrfs_path *path,
+ struct btrfs_backref_iter *iter,
+ struct btrfs_key *node_key,
+ struct btrfs_backref_node *cur);
+
+int btrfs_backref_finish_upper_links(struct btrfs_backref_cache *cache,
+ struct btrfs_backref_node *start);
+
+void btrfs_backref_error_cleanup(struct btrfs_backref_cache *cache,
+ struct btrfs_backref_node *node);
+
+#endif