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-rw-r--r--fs/btrfs/backref.c3648
1 files changed, 3648 insertions, 0 deletions
diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
new file mode 100644
index 0000000000..a4a809efc9
--- /dev/null
+++ b/fs/btrfs/backref.c
@@ -0,0 +1,3648 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2011 STRATO. All rights reserved.
+ */
+
+#include <linux/mm.h>
+#include <linux/rbtree.h>
+#include <trace/events/btrfs.h>
+#include "ctree.h"
+#include "disk-io.h"
+#include "backref.h"
+#include "ulist.h"
+#include "transaction.h"
+#include "delayed-ref.h"
+#include "locking.h"
+#include "misc.h"
+#include "tree-mod-log.h"
+#include "fs.h"
+#include "accessors.h"
+#include "extent-tree.h"
+#include "relocation.h"
+#include "tree-checker.h"
+
+/* Just arbitrary numbers so we can be sure one of these happened. */
+#define BACKREF_FOUND_SHARED 6
+#define BACKREF_FOUND_NOT_SHARED 7
+
+struct extent_inode_elem {
+ u64 inum;
+ u64 offset;
+ u64 num_bytes;
+ struct extent_inode_elem *next;
+};
+
+static int check_extent_in_eb(struct btrfs_backref_walk_ctx *ctx,
+ const struct btrfs_key *key,
+ const struct extent_buffer *eb,
+ const struct btrfs_file_extent_item *fi,
+ struct extent_inode_elem **eie)
+{
+ const u64 data_len = btrfs_file_extent_num_bytes(eb, fi);
+ u64 offset = key->offset;
+ struct extent_inode_elem *e;
+ const u64 *root_ids;
+ int root_count;
+ bool cached;
+
+ if (!ctx->ignore_extent_item_pos &&
+ !btrfs_file_extent_compression(eb, fi) &&
+ !btrfs_file_extent_encryption(eb, fi) &&
+ !btrfs_file_extent_other_encoding(eb, fi)) {
+ u64 data_offset;
+
+ data_offset = btrfs_file_extent_offset(eb, fi);
+
+ if (ctx->extent_item_pos < data_offset ||
+ ctx->extent_item_pos >= data_offset + data_len)
+ return 1;
+ offset += ctx->extent_item_pos - data_offset;
+ }
+
+ if (!ctx->indirect_ref_iterator || !ctx->cache_lookup)
+ goto add_inode_elem;
+
+ cached = ctx->cache_lookup(eb->start, ctx->user_ctx, &root_ids,
+ &root_count);
+ if (!cached)
+ goto add_inode_elem;
+
+ for (int i = 0; i < root_count; i++) {
+ int ret;
+
+ ret = ctx->indirect_ref_iterator(key->objectid, offset,
+ data_len, root_ids[i],
+ ctx->user_ctx);
+ if (ret)
+ return ret;
+ }
+
+add_inode_elem:
+ e = kmalloc(sizeof(*e), GFP_NOFS);
+ if (!e)
+ return -ENOMEM;
+
+ e->next = *eie;
+ e->inum = key->objectid;
+ e->offset = offset;
+ e->num_bytes = data_len;
+ *eie = e;
+
+ return 0;
+}
+
+static void free_inode_elem_list(struct extent_inode_elem *eie)
+{
+ struct extent_inode_elem *eie_next;
+
+ for (; eie; eie = eie_next) {
+ eie_next = eie->next;
+ kfree(eie);
+ }
+}
+
+static int find_extent_in_eb(struct btrfs_backref_walk_ctx *ctx,
+ const struct extent_buffer *eb,
+ struct extent_inode_elem **eie)
+{
+ u64 disk_byte;
+ struct btrfs_key key;
+ struct btrfs_file_extent_item *fi;
+ int slot;
+ int nritems;
+ int extent_type;
+ int ret;
+
+ /*
+ * from the shared data ref, we only have the leaf but we need
+ * the key. thus, we must look into all items and see that we
+ * find one (some) with a reference to our extent item.
+ */
+ nritems = btrfs_header_nritems(eb);
+ for (slot = 0; slot < nritems; ++slot) {
+ btrfs_item_key_to_cpu(eb, &key, slot);
+ if (key.type != BTRFS_EXTENT_DATA_KEY)
+ continue;
+ fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
+ extent_type = btrfs_file_extent_type(eb, fi);
+ if (extent_type == BTRFS_FILE_EXTENT_INLINE)
+ continue;
+ /* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
+ disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
+ if (disk_byte != ctx->bytenr)
+ continue;
+
+ ret = check_extent_in_eb(ctx, &key, eb, fi, eie);
+ if (ret == BTRFS_ITERATE_EXTENT_INODES_STOP || ret < 0)
+ return ret;
+ }
+
+ return 0;
+}
+
+struct preftree {
+ struct rb_root_cached root;
+ unsigned int count;
+};
+
+#define PREFTREE_INIT { .root = RB_ROOT_CACHED, .count = 0 }
+
+struct preftrees {
+ struct preftree direct; /* BTRFS_SHARED_[DATA|BLOCK]_REF_KEY */
+ struct preftree indirect; /* BTRFS_[TREE_BLOCK|EXTENT_DATA]_REF_KEY */
+ struct preftree indirect_missing_keys;
+};
+
+/*
+ * Checks for a shared extent during backref search.
+ *
+ * The share_count tracks prelim_refs (direct and indirect) having a
+ * ref->count >0:
+ * - incremented when a ref->count transitions to >0
+ * - decremented when a ref->count transitions to <1
+ */
+struct share_check {
+ struct btrfs_backref_share_check_ctx *ctx;
+ struct btrfs_root *root;
+ u64 inum;
+ u64 data_bytenr;
+ u64 data_extent_gen;
+ /*
+ * Counts number of inodes that refer to an extent (different inodes in
+ * the same root or different roots) that we could find. The sharedness
+ * check typically stops once this counter gets greater than 1, so it
+ * may not reflect the total number of inodes.
+ */
+ int share_count;
+ /*
+ * The number of times we found our inode refers to the data extent we
+ * are determining the sharedness. In other words, how many file extent
+ * items we could find for our inode that point to our target data
+ * extent. The value we get here after finishing the extent sharedness
+ * check may be smaller than reality, but if it ends up being greater
+ * than 1, then we know for sure the inode has multiple file extent
+ * items that point to our inode, and we can safely assume it's useful
+ * to cache the sharedness check result.
+ */
+ int self_ref_count;
+ bool have_delayed_delete_refs;
+};
+
+static inline int extent_is_shared(struct share_check *sc)
+{
+ return (sc && sc->share_count > 1) ? BACKREF_FOUND_SHARED : 0;
+}
+
+static struct kmem_cache *btrfs_prelim_ref_cache;
+
+int __init btrfs_prelim_ref_init(void)
+{
+ btrfs_prelim_ref_cache = kmem_cache_create("btrfs_prelim_ref",
+ sizeof(struct prelim_ref),
+ 0,
+ SLAB_MEM_SPREAD,
+ NULL);
+ if (!btrfs_prelim_ref_cache)
+ return -ENOMEM;
+ return 0;
+}
+
+void __cold btrfs_prelim_ref_exit(void)
+{
+ kmem_cache_destroy(btrfs_prelim_ref_cache);
+}
+
+static void free_pref(struct prelim_ref *ref)
+{
+ kmem_cache_free(btrfs_prelim_ref_cache, ref);
+}
+
+/*
+ * Return 0 when both refs are for the same block (and can be merged).
+ * A -1 return indicates ref1 is a 'lower' block than ref2, while 1
+ * indicates a 'higher' block.
+ */
+static int prelim_ref_compare(struct prelim_ref *ref1,
+ struct prelim_ref *ref2)
+{
+ if (ref1->level < ref2->level)
+ return -1;
+ if (ref1->level > ref2->level)
+ return 1;
+ if (ref1->root_id < ref2->root_id)
+ return -1;
+ if (ref1->root_id > ref2->root_id)
+ return 1;
+ if (ref1->key_for_search.type < ref2->key_for_search.type)
+ return -1;
+ if (ref1->key_for_search.type > ref2->key_for_search.type)
+ return 1;
+ if (ref1->key_for_search.objectid < ref2->key_for_search.objectid)
+ return -1;
+ if (ref1->key_for_search.objectid > ref2->key_for_search.objectid)
+ return 1;
+ if (ref1->key_for_search.offset < ref2->key_for_search.offset)
+ return -1;
+ if (ref1->key_for_search.offset > ref2->key_for_search.offset)
+ return 1;
+ if (ref1->parent < ref2->parent)
+ return -1;
+ if (ref1->parent > ref2->parent)
+ return 1;
+
+ return 0;
+}
+
+static void update_share_count(struct share_check *sc, int oldcount,
+ int newcount, struct prelim_ref *newref)
+{
+ if ((!sc) || (oldcount == 0 && newcount < 1))
+ return;
+
+ if (oldcount > 0 && newcount < 1)
+ sc->share_count--;
+ else if (oldcount < 1 && newcount > 0)
+ sc->share_count++;
+
+ if (newref->root_id == sc->root->root_key.objectid &&
+ newref->wanted_disk_byte == sc->data_bytenr &&
+ newref->key_for_search.objectid == sc->inum)
+ sc->self_ref_count += newref->count;
+}
+
+/*
+ * Add @newref to the @root rbtree, merging identical refs.
+ *
+ * Callers should assume that newref has been freed after calling.
+ */
+static void prelim_ref_insert(const struct btrfs_fs_info *fs_info,
+ struct preftree *preftree,
+ struct prelim_ref *newref,
+ struct share_check *sc)
+{
+ struct rb_root_cached *root;
+ struct rb_node **p;
+ struct rb_node *parent = NULL;
+ struct prelim_ref *ref;
+ int result;
+ bool leftmost = true;
+
+ root = &preftree->root;
+ p = &root->rb_root.rb_node;
+
+ while (*p) {
+ parent = *p;
+ ref = rb_entry(parent, struct prelim_ref, rbnode);
+ result = prelim_ref_compare(ref, newref);
+ if (result < 0) {
+ p = &(*p)->rb_left;
+ } else if (result > 0) {
+ p = &(*p)->rb_right;
+ leftmost = false;
+ } else {
+ /* Identical refs, merge them and free @newref */
+ struct extent_inode_elem *eie = ref->inode_list;
+
+ while (eie && eie->next)
+ eie = eie->next;
+
+ if (!eie)
+ ref->inode_list = newref->inode_list;
+ else
+ eie->next = newref->inode_list;
+ trace_btrfs_prelim_ref_merge(fs_info, ref, newref,
+ preftree->count);
+ /*
+ * A delayed ref can have newref->count < 0.
+ * The ref->count is updated to follow any
+ * BTRFS_[ADD|DROP]_DELAYED_REF actions.
+ */
+ update_share_count(sc, ref->count,
+ ref->count + newref->count, newref);
+ ref->count += newref->count;
+ free_pref(newref);
+ return;
+ }
+ }
+
+ update_share_count(sc, 0, newref->count, newref);
+ preftree->count++;
+ trace_btrfs_prelim_ref_insert(fs_info, newref, NULL, preftree->count);
+ rb_link_node(&newref->rbnode, parent, p);
+ rb_insert_color_cached(&newref->rbnode, root, leftmost);
+}
+
+/*
+ * Release the entire tree. We don't care about internal consistency so
+ * just free everything and then reset the tree root.
+ */
+static void prelim_release(struct preftree *preftree)
+{
+ struct prelim_ref *ref, *next_ref;
+
+ rbtree_postorder_for_each_entry_safe(ref, next_ref,
+ &preftree->root.rb_root, rbnode) {
+ free_inode_elem_list(ref->inode_list);
+ free_pref(ref);
+ }
+
+ preftree->root = RB_ROOT_CACHED;
+ preftree->count = 0;
+}
+
+/*
+ * the rules for all callers of this function are:
+ * - obtaining the parent is the goal
+ * - if you add a key, you must know that it is a correct key
+ * - if you cannot add the parent or a correct key, then we will look into the
+ * block later to set a correct key
+ *
+ * delayed refs
+ * ============
+ * backref type | shared | indirect | shared | indirect
+ * information | tree | tree | data | data
+ * --------------------+--------+----------+--------+----------
+ * parent logical | y | - | - | -
+ * key to resolve | - | y | y | y
+ * tree block logical | - | - | - | -
+ * root for resolving | y | y | y | y
+ *
+ * - column 1: we've the parent -> done
+ * - column 2, 3, 4: we use the key to find the parent
+ *
+ * on disk refs (inline or keyed)
+ * ==============================
+ * backref type | shared | indirect | shared | indirect
+ * information | tree | tree | data | data
+ * --------------------+--------+----------+--------+----------
+ * parent logical | y | - | y | -
+ * key to resolve | - | - | - | y
+ * tree block logical | y | y | y | y
+ * root for resolving | - | y | y | y
+ *
+ * - column 1, 3: we've the parent -> done
+ * - column 2: we take the first key from the block to find the parent
+ * (see add_missing_keys)
+ * - column 4: we use the key to find the parent
+ *
+ * additional information that's available but not required to find the parent
+ * block might help in merging entries to gain some speed.
+ */
+static int add_prelim_ref(const struct btrfs_fs_info *fs_info,
+ struct preftree *preftree, u64 root_id,
+ const struct btrfs_key *key, int level, u64 parent,
+ u64 wanted_disk_byte, int count,
+ struct share_check *sc, gfp_t gfp_mask)
+{
+ struct prelim_ref *ref;
+
+ if (root_id == BTRFS_DATA_RELOC_TREE_OBJECTID)
+ return 0;
+
+ ref = kmem_cache_alloc(btrfs_prelim_ref_cache, gfp_mask);
+ if (!ref)
+ return -ENOMEM;
+
+ ref->root_id = root_id;
+ if (key)
+ ref->key_for_search = *key;
+ else
+ memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
+
+ ref->inode_list = NULL;
+ ref->level = level;
+ ref->count = count;
+ ref->parent = parent;
+ ref->wanted_disk_byte = wanted_disk_byte;
+ prelim_ref_insert(fs_info, preftree, ref, sc);
+ return extent_is_shared(sc);
+}
+
+/* direct refs use root == 0, key == NULL */
+static int add_direct_ref(const struct btrfs_fs_info *fs_info,
+ struct preftrees *preftrees, int level, u64 parent,
+ u64 wanted_disk_byte, int count,
+ struct share_check *sc, gfp_t gfp_mask)
+{
+ return add_prelim_ref(fs_info, &preftrees->direct, 0, NULL, level,
+ parent, wanted_disk_byte, count, sc, gfp_mask);
+}
+
+/* indirect refs use parent == 0 */
+static int add_indirect_ref(const struct btrfs_fs_info *fs_info,
+ struct preftrees *preftrees, u64 root_id,
+ const struct btrfs_key *key, int level,
+ u64 wanted_disk_byte, int count,
+ struct share_check *sc, gfp_t gfp_mask)
+{
+ struct preftree *tree = &preftrees->indirect;
+
+ if (!key)
+ tree = &preftrees->indirect_missing_keys;
+ return add_prelim_ref(fs_info, tree, root_id, key, level, 0,
+ wanted_disk_byte, count, sc, gfp_mask);
+}
+
+static int is_shared_data_backref(struct preftrees *preftrees, u64 bytenr)
+{
+ struct rb_node **p = &preftrees->direct.root.rb_root.rb_node;
+ struct rb_node *parent = NULL;
+ struct prelim_ref *ref = NULL;
+ struct prelim_ref target = {};
+ int result;
+
+ target.parent = bytenr;
+
+ while (*p) {
+ parent = *p;
+ ref = rb_entry(parent, struct prelim_ref, rbnode);
+ result = prelim_ref_compare(ref, &target);
+
+ if (result < 0)
+ p = &(*p)->rb_left;
+ else if (result > 0)
+ p = &(*p)->rb_right;
+ else
+ return 1;
+ }
+ return 0;
+}
+
+static int add_all_parents(struct btrfs_backref_walk_ctx *ctx,
+ struct btrfs_root *root, struct btrfs_path *path,
+ struct ulist *parents,
+ struct preftrees *preftrees, struct prelim_ref *ref,
+ int level)
+{
+ int ret = 0;
+ int slot;
+ struct extent_buffer *eb;
+ struct btrfs_key key;
+ struct btrfs_key *key_for_search = &ref->key_for_search;
+ struct btrfs_file_extent_item *fi;
+ struct extent_inode_elem *eie = NULL, *old = NULL;
+ u64 disk_byte;
+ u64 wanted_disk_byte = ref->wanted_disk_byte;
+ u64 count = 0;
+ u64 data_offset;
+ u8 type;
+
+ if (level != 0) {
+ eb = path->nodes[level];
+ ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
+ if (ret < 0)
+ return ret;
+ return 0;
+ }
+
+ /*
+ * 1. We normally enter this function with the path already pointing to
+ * the first item to check. But sometimes, we may enter it with
+ * slot == nritems.
+ * 2. We are searching for normal backref but bytenr of this leaf
+ * matches shared data backref
+ * 3. The leaf owner is not equal to the root we are searching
+ *
+ * For these cases, go to the next leaf before we continue.
+ */
+ eb = path->nodes[0];
+ if (path->slots[0] >= btrfs_header_nritems(eb) ||
+ is_shared_data_backref(preftrees, eb->start) ||
+ ref->root_id != btrfs_header_owner(eb)) {
+ if (ctx->time_seq == BTRFS_SEQ_LAST)
+ ret = btrfs_next_leaf(root, path);
+ else
+ ret = btrfs_next_old_leaf(root, path, ctx->time_seq);
+ }
+
+ while (!ret && count < ref->count) {
+ eb = path->nodes[0];
+ slot = path->slots[0];
+
+ btrfs_item_key_to_cpu(eb, &key, slot);
+
+ if (key.objectid != key_for_search->objectid ||
+ key.type != BTRFS_EXTENT_DATA_KEY)
+ break;
+
+ /*
+ * We are searching for normal backref but bytenr of this leaf
+ * matches shared data backref, OR
+ * the leaf owner is not equal to the root we are searching for
+ */
+ if (slot == 0 &&
+ (is_shared_data_backref(preftrees, eb->start) ||
+ ref->root_id != btrfs_header_owner(eb))) {
+ if (ctx->time_seq == BTRFS_SEQ_LAST)
+ ret = btrfs_next_leaf(root, path);
+ else
+ ret = btrfs_next_old_leaf(root, path, ctx->time_seq);
+ continue;
+ }
+ fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
+ type = btrfs_file_extent_type(eb, fi);
+ if (type == BTRFS_FILE_EXTENT_INLINE)
+ goto next;
+ disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
+ data_offset = btrfs_file_extent_offset(eb, fi);
+
+ if (disk_byte == wanted_disk_byte) {
+ eie = NULL;
+ old = NULL;
+ if (ref->key_for_search.offset == key.offset - data_offset)
+ count++;
+ else
+ goto next;
+ if (!ctx->skip_inode_ref_list) {
+ ret = check_extent_in_eb(ctx, &key, eb, fi, &eie);
+ if (ret == BTRFS_ITERATE_EXTENT_INODES_STOP ||
+ ret < 0)
+ break;
+ }
+ if (ret > 0)
+ goto next;
+ ret = ulist_add_merge_ptr(parents, eb->start,
+ eie, (void **)&old, GFP_NOFS);
+ if (ret < 0)
+ break;
+ if (!ret && !ctx->skip_inode_ref_list) {
+ while (old->next)
+ old = old->next;
+ old->next = eie;
+ }
+ eie = NULL;
+ }
+next:
+ if (ctx->time_seq == BTRFS_SEQ_LAST)
+ ret = btrfs_next_item(root, path);
+ else
+ ret = btrfs_next_old_item(root, path, ctx->time_seq);
+ }
+
+ if (ret == BTRFS_ITERATE_EXTENT_INODES_STOP || ret < 0)
+ free_inode_elem_list(eie);
+ else if (ret > 0)
+ ret = 0;
+
+ return ret;
+}
+
+/*
+ * resolve an indirect backref in the form (root_id, key, level)
+ * to a logical address
+ */
+static int resolve_indirect_ref(struct btrfs_backref_walk_ctx *ctx,
+ struct btrfs_path *path,
+ struct preftrees *preftrees,
+ struct prelim_ref *ref, struct ulist *parents)
+{
+ struct btrfs_root *root;
+ struct extent_buffer *eb;
+ int ret = 0;
+ int root_level;
+ int level = ref->level;
+ struct btrfs_key search_key = ref->key_for_search;
+
+ /*
+ * If we're search_commit_root we could possibly be holding locks on
+ * other tree nodes. This happens when qgroups does backref walks when
+ * adding new delayed refs. To deal with this we need to look in cache
+ * for the root, and if we don't find it then we need to search the
+ * tree_root's commit root, thus the btrfs_get_fs_root_commit_root usage
+ * here.
+ */
+ if (path->search_commit_root)
+ root = btrfs_get_fs_root_commit_root(ctx->fs_info, path, ref->root_id);
+ else
+ root = btrfs_get_fs_root(ctx->fs_info, ref->root_id, false);
+ if (IS_ERR(root)) {
+ ret = PTR_ERR(root);
+ goto out_free;
+ }
+
+ if (!path->search_commit_root &&
+ test_bit(BTRFS_ROOT_DELETING, &root->state)) {
+ ret = -ENOENT;
+ goto out;
+ }
+
+ if (btrfs_is_testing(ctx->fs_info)) {
+ ret = -ENOENT;
+ goto out;
+ }
+
+ if (path->search_commit_root)
+ root_level = btrfs_header_level(root->commit_root);
+ else if (ctx->time_seq == BTRFS_SEQ_LAST)
+ root_level = btrfs_header_level(root->node);
+ else
+ root_level = btrfs_old_root_level(root, ctx->time_seq);
+
+ if (root_level + 1 == level)
+ goto out;
+
+ /*
+ * We can often find data backrefs with an offset that is too large
+ * (>= LLONG_MAX, maximum allowed file offset) due to underflows when
+ * subtracting a file's offset with the data offset of its
+ * corresponding extent data item. This can happen for example in the
+ * clone ioctl.
+ *
+ * So if we detect such case we set the search key's offset to zero to
+ * make sure we will find the matching file extent item at
+ * add_all_parents(), otherwise we will miss it because the offset
+ * taken form the backref is much larger then the offset of the file
+ * extent item. This can make us scan a very large number of file
+ * extent items, but at least it will not make us miss any.
+ *
+ * This is an ugly workaround for a behaviour that should have never
+ * existed, but it does and a fix for the clone ioctl would touch a lot
+ * of places, cause backwards incompatibility and would not fix the
+ * problem for extents cloned with older kernels.
+ */
+ if (search_key.type == BTRFS_EXTENT_DATA_KEY &&
+ search_key.offset >= LLONG_MAX)
+ search_key.offset = 0;
+ path->lowest_level = level;
+ if (ctx->time_seq == BTRFS_SEQ_LAST)
+ ret = btrfs_search_slot(NULL, root, &search_key, path, 0, 0);
+ else
+ ret = btrfs_search_old_slot(root, &search_key, path, ctx->time_seq);
+
+ btrfs_debug(ctx->fs_info,
+ "search slot in root %llu (level %d, ref count %d) returned %d for key (%llu %u %llu)",
+ ref->root_id, level, ref->count, ret,
+ ref->key_for_search.objectid, ref->key_for_search.type,
+ ref->key_for_search.offset);
+ if (ret < 0)
+ goto out;
+
+ eb = path->nodes[level];
+ while (!eb) {
+ if (WARN_ON(!level)) {
+ ret = 1;
+ goto out;
+ }
+ level--;
+ eb = path->nodes[level];
+ }
+
+ ret = add_all_parents(ctx, root, path, parents, preftrees, ref, level);
+out:
+ btrfs_put_root(root);
+out_free:
+ path->lowest_level = 0;
+ btrfs_release_path(path);
+ return ret;
+}
+
+static struct extent_inode_elem *
+unode_aux_to_inode_list(struct ulist_node *node)
+{
+ if (!node)
+ return NULL;
+ return (struct extent_inode_elem *)(uintptr_t)node->aux;
+}
+
+static void free_leaf_list(struct ulist *ulist)
+{
+ struct ulist_node *node;
+ struct ulist_iterator uiter;
+
+ ULIST_ITER_INIT(&uiter);
+ while ((node = ulist_next(ulist, &uiter)))
+ free_inode_elem_list(unode_aux_to_inode_list(node));
+
+ ulist_free(ulist);
+}
+
+/*
+ * We maintain three separate rbtrees: one for direct refs, one for
+ * indirect refs which have a key, and one for indirect refs which do not
+ * have a key. Each tree does merge on insertion.
+ *
+ * Once all of the references are located, we iterate over the tree of
+ * indirect refs with missing keys. An appropriate key is located and
+ * the ref is moved onto the tree for indirect refs. After all missing
+ * keys are thus located, we iterate over the indirect ref tree, resolve
+ * each reference, and then insert the resolved reference onto the
+ * direct tree (merging there too).
+ *
+ * New backrefs (i.e., for parent nodes) are added to the appropriate
+ * rbtree as they are encountered. The new backrefs are subsequently
+ * resolved as above.
+ */
+static int resolve_indirect_refs(struct btrfs_backref_walk_ctx *ctx,
+ struct btrfs_path *path,
+ struct preftrees *preftrees,
+ struct share_check *sc)
+{
+ int err;
+ int ret = 0;
+ struct ulist *parents;
+ struct ulist_node *node;
+ struct ulist_iterator uiter;
+ struct rb_node *rnode;
+
+ parents = ulist_alloc(GFP_NOFS);
+ if (!parents)
+ return -ENOMEM;
+
+ /*
+ * We could trade memory usage for performance here by iterating
+ * the tree, allocating new refs for each insertion, and then
+ * freeing the entire indirect tree when we're done. In some test
+ * cases, the tree can grow quite large (~200k objects).
+ */
+ while ((rnode = rb_first_cached(&preftrees->indirect.root))) {
+ struct prelim_ref *ref;
+
+ ref = rb_entry(rnode, struct prelim_ref, rbnode);
+ if (WARN(ref->parent,
+ "BUG: direct ref found in indirect tree")) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ rb_erase_cached(&ref->rbnode, &preftrees->indirect.root);
+ preftrees->indirect.count--;
+
+ if (ref->count == 0) {
+ free_pref(ref);
+ continue;
+ }
+
+ if (sc && ref->root_id != sc->root->root_key.objectid) {
+ free_pref(ref);
+ ret = BACKREF_FOUND_SHARED;
+ goto out;
+ }
+ err = resolve_indirect_ref(ctx, path, preftrees, ref, parents);
+ /*
+ * we can only tolerate ENOENT,otherwise,we should catch error
+ * and return directly.
+ */
+ if (err == -ENOENT) {
+ prelim_ref_insert(ctx->fs_info, &preftrees->direct, ref,
+ NULL);
+ continue;
+ } else if (err) {
+ free_pref(ref);
+ ret = err;
+ goto out;
+ }
+
+ /* we put the first parent into the ref at hand */
+ ULIST_ITER_INIT(&uiter);
+ node = ulist_next(parents, &uiter);
+ ref->parent = node ? node->val : 0;
+ ref->inode_list = unode_aux_to_inode_list(node);
+
+ /* Add a prelim_ref(s) for any other parent(s). */
+ while ((node = ulist_next(parents, &uiter))) {
+ struct prelim_ref *new_ref;
+
+ new_ref = kmem_cache_alloc(btrfs_prelim_ref_cache,
+ GFP_NOFS);
+ if (!new_ref) {
+ free_pref(ref);
+ ret = -ENOMEM;
+ goto out;
+ }
+ memcpy(new_ref, ref, sizeof(*ref));
+ new_ref->parent = node->val;
+ new_ref->inode_list = unode_aux_to_inode_list(node);
+ prelim_ref_insert(ctx->fs_info, &preftrees->direct,
+ new_ref, NULL);
+ }
+
+ /*
+ * Now it's a direct ref, put it in the direct tree. We must
+ * do this last because the ref could be merged/freed here.
+ */
+ prelim_ref_insert(ctx->fs_info, &preftrees->direct, ref, NULL);
+
+ ulist_reinit(parents);
+ cond_resched();
+ }
+out:
+ /*
+ * We may have inode lists attached to refs in the parents ulist, so we
+ * must free them before freeing the ulist and its refs.
+ */
+ free_leaf_list(parents);
+ return ret;
+}
+
+/*
+ * read tree blocks and add keys where required.
+ */
+static int add_missing_keys(struct btrfs_fs_info *fs_info,
+ struct preftrees *preftrees, bool lock)
+{
+ struct prelim_ref *ref;
+ struct extent_buffer *eb;
+ struct preftree *tree = &preftrees->indirect_missing_keys;
+ struct rb_node *node;
+
+ while ((node = rb_first_cached(&tree->root))) {
+ struct btrfs_tree_parent_check check = { 0 };
+
+ ref = rb_entry(node, struct prelim_ref, rbnode);
+ rb_erase_cached(node, &tree->root);
+
+ BUG_ON(ref->parent); /* should not be a direct ref */
+ BUG_ON(ref->key_for_search.type);
+ BUG_ON(!ref->wanted_disk_byte);
+
+ check.level = ref->level - 1;
+ check.owner_root = ref->root_id;
+
+ eb = read_tree_block(fs_info, ref->wanted_disk_byte, &check);
+ if (IS_ERR(eb)) {
+ free_pref(ref);
+ return PTR_ERR(eb);
+ }
+ if (!extent_buffer_uptodate(eb)) {
+ free_pref(ref);
+ free_extent_buffer(eb);
+ return -EIO;
+ }
+
+ if (lock)
+ btrfs_tree_read_lock(eb);
+ if (btrfs_header_level(eb) == 0)
+ btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
+ else
+ btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
+ if (lock)
+ btrfs_tree_read_unlock(eb);
+ free_extent_buffer(eb);
+ prelim_ref_insert(fs_info, &preftrees->indirect, ref, NULL);
+ cond_resched();
+ }
+ return 0;
+}
+
+/*
+ * add all currently queued delayed refs from this head whose seq nr is
+ * smaller or equal that seq to the list
+ */
+static int add_delayed_refs(const struct btrfs_fs_info *fs_info,
+ struct btrfs_delayed_ref_head *head, u64 seq,
+ struct preftrees *preftrees, struct share_check *sc)
+{
+ struct btrfs_delayed_ref_node *node;
+ struct btrfs_key key;
+ struct rb_node *n;
+ int count;
+ int ret = 0;
+
+ spin_lock(&head->lock);
+ for (n = rb_first_cached(&head->ref_tree); n; n = rb_next(n)) {
+ node = rb_entry(n, struct btrfs_delayed_ref_node,
+ ref_node);
+ if (node->seq > seq)
+ continue;
+
+ switch (node->action) {
+ case BTRFS_ADD_DELAYED_EXTENT:
+ case BTRFS_UPDATE_DELAYED_HEAD:
+ WARN_ON(1);
+ continue;
+ case BTRFS_ADD_DELAYED_REF:
+ count = node->ref_mod;
+ break;
+ case BTRFS_DROP_DELAYED_REF:
+ count = node->ref_mod * -1;
+ break;
+ default:
+ BUG();
+ }
+ switch (node->type) {
+ case BTRFS_TREE_BLOCK_REF_KEY: {
+ /* NORMAL INDIRECT METADATA backref */
+ struct btrfs_delayed_tree_ref *ref;
+ struct btrfs_key *key_ptr = NULL;
+
+ if (head->extent_op && head->extent_op->update_key) {
+ btrfs_disk_key_to_cpu(&key, &head->extent_op->key);
+ key_ptr = &key;
+ }
+
+ ref = btrfs_delayed_node_to_tree_ref(node);
+ ret = add_indirect_ref(fs_info, preftrees, ref->root,
+ key_ptr, ref->level + 1,
+ node->bytenr, count, sc,
+ GFP_ATOMIC);
+ break;
+ }
+ case BTRFS_SHARED_BLOCK_REF_KEY: {
+ /* SHARED DIRECT METADATA backref */
+ struct btrfs_delayed_tree_ref *ref;
+
+ ref = btrfs_delayed_node_to_tree_ref(node);
+
+ ret = add_direct_ref(fs_info, preftrees, ref->level + 1,
+ ref->parent, node->bytenr, count,
+ sc, GFP_ATOMIC);
+ break;
+ }
+ case BTRFS_EXTENT_DATA_REF_KEY: {
+ /* NORMAL INDIRECT DATA backref */
+ struct btrfs_delayed_data_ref *ref;
+ ref = btrfs_delayed_node_to_data_ref(node);
+
+ key.objectid = ref->objectid;
+ key.type = BTRFS_EXTENT_DATA_KEY;
+ key.offset = ref->offset;
+
+ /*
+ * If we have a share check context and a reference for
+ * another inode, we can't exit immediately. This is
+ * because even if this is a BTRFS_ADD_DELAYED_REF
+ * reference we may find next a BTRFS_DROP_DELAYED_REF
+ * which cancels out this ADD reference.
+ *
+ * If this is a DROP reference and there was no previous
+ * ADD reference, then we need to signal that when we
+ * process references from the extent tree (through
+ * add_inline_refs() and add_keyed_refs()), we should
+ * not exit early if we find a reference for another
+ * inode, because one of the delayed DROP references
+ * may cancel that reference in the extent tree.
+ */
+ if (sc && count < 0)
+ sc->have_delayed_delete_refs = true;
+
+ ret = add_indirect_ref(fs_info, preftrees, ref->root,
+ &key, 0, node->bytenr, count, sc,
+ GFP_ATOMIC);
+ break;
+ }
+ case BTRFS_SHARED_DATA_REF_KEY: {
+ /* SHARED DIRECT FULL backref */
+ struct btrfs_delayed_data_ref *ref;
+
+ ref = btrfs_delayed_node_to_data_ref(node);
+
+ ret = add_direct_ref(fs_info, preftrees, 0, ref->parent,
+ node->bytenr, count, sc,
+ GFP_ATOMIC);
+ break;
+ }
+ default:
+ WARN_ON(1);
+ }
+ /*
+ * We must ignore BACKREF_FOUND_SHARED until all delayed
+ * refs have been checked.
+ */
+ if (ret && (ret != BACKREF_FOUND_SHARED))
+ break;
+ }
+ if (!ret)
+ ret = extent_is_shared(sc);
+
+ spin_unlock(&head->lock);
+ return ret;
+}
+
+/*
+ * add all inline backrefs for bytenr to the list
+ *
+ * Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
+ */
+static int add_inline_refs(struct btrfs_backref_walk_ctx *ctx,
+ struct btrfs_path *path,
+ int *info_level, struct preftrees *preftrees,
+ struct share_check *sc)
+{
+ int ret = 0;
+ int slot;
+ struct extent_buffer *leaf;
+ struct btrfs_key key;
+ struct btrfs_key found_key;
+ unsigned long ptr;
+ unsigned long end;
+ struct btrfs_extent_item *ei;
+ u64 flags;
+ u64 item_size;
+
+ /*
+ * enumerate all inline refs
+ */
+ leaf = path->nodes[0];
+ slot = path->slots[0];
+
+ item_size = btrfs_item_size(leaf, slot);
+ BUG_ON(item_size < sizeof(*ei));
+
+ ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
+
+ if (ctx->check_extent_item) {
+ ret = ctx->check_extent_item(ctx->bytenr, ei, leaf, ctx->user_ctx);
+ if (ret)
+ return ret;
+ }
+
+ flags = btrfs_extent_flags(leaf, ei);
+ btrfs_item_key_to_cpu(leaf, &found_key, slot);
+
+ ptr = (unsigned long)(ei + 1);
+ end = (unsigned long)ei + item_size;
+
+ if (found_key.type == BTRFS_EXTENT_ITEM_KEY &&
+ flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
+ struct btrfs_tree_block_info *info;
+
+ info = (struct btrfs_tree_block_info *)ptr;
+ *info_level = btrfs_tree_block_level(leaf, info);
+ ptr += sizeof(struct btrfs_tree_block_info);
+ BUG_ON(ptr > end);
+ } else if (found_key.type == BTRFS_METADATA_ITEM_KEY) {
+ *info_level = found_key.offset;
+ } else {
+ BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
+ }
+
+ while (ptr < end) {
+ struct btrfs_extent_inline_ref *iref;
+ u64 offset;
+ int type;
+
+ iref = (struct btrfs_extent_inline_ref *)ptr;
+ type = btrfs_get_extent_inline_ref_type(leaf, iref,
+ BTRFS_REF_TYPE_ANY);
+ if (type == BTRFS_REF_TYPE_INVALID)
+ return -EUCLEAN;
+
+ offset = btrfs_extent_inline_ref_offset(leaf, iref);
+
+ switch (type) {
+ case BTRFS_SHARED_BLOCK_REF_KEY:
+ ret = add_direct_ref(ctx->fs_info, preftrees,
+ *info_level + 1, offset,
+ ctx->bytenr, 1, NULL, GFP_NOFS);
+ break;
+ case BTRFS_SHARED_DATA_REF_KEY: {
+ struct btrfs_shared_data_ref *sdref;
+ int count;
+
+ sdref = (struct btrfs_shared_data_ref *)(iref + 1);
+ count = btrfs_shared_data_ref_count(leaf, sdref);
+
+ ret = add_direct_ref(ctx->fs_info, preftrees, 0, offset,
+ ctx->bytenr, count, sc, GFP_NOFS);
+ break;
+ }
+ case BTRFS_TREE_BLOCK_REF_KEY:
+ ret = add_indirect_ref(ctx->fs_info, preftrees, offset,
+ NULL, *info_level + 1,
+ ctx->bytenr, 1, NULL, GFP_NOFS);
+ break;
+ case BTRFS_EXTENT_DATA_REF_KEY: {
+ struct btrfs_extent_data_ref *dref;
+ int count;
+ u64 root;
+
+ dref = (struct btrfs_extent_data_ref *)(&iref->offset);
+ count = btrfs_extent_data_ref_count(leaf, dref);
+ key.objectid = btrfs_extent_data_ref_objectid(leaf,
+ dref);
+ key.type = BTRFS_EXTENT_DATA_KEY;
+ key.offset = btrfs_extent_data_ref_offset(leaf, dref);
+
+ if (sc && key.objectid != sc->inum &&
+ !sc->have_delayed_delete_refs) {
+ ret = BACKREF_FOUND_SHARED;
+ break;
+ }
+
+ root = btrfs_extent_data_ref_root(leaf, dref);
+
+ if (!ctx->skip_data_ref ||
+ !ctx->skip_data_ref(root, key.objectid, key.offset,
+ ctx->user_ctx))
+ ret = add_indirect_ref(ctx->fs_info, preftrees,
+ root, &key, 0, ctx->bytenr,
+ count, sc, GFP_NOFS);
+ break;
+ }
+ default:
+ WARN_ON(1);
+ }
+ if (ret)
+ return ret;
+ ptr += btrfs_extent_inline_ref_size(type);
+ }
+
+ return 0;
+}
+
+/*
+ * add all non-inline backrefs for bytenr to the list
+ *
+ * Returns 0 on success, <0 on error, or BACKREF_FOUND_SHARED.
+ */
+static int add_keyed_refs(struct btrfs_backref_walk_ctx *ctx,
+ struct btrfs_root *extent_root,
+ struct btrfs_path *path,
+ int info_level, struct preftrees *preftrees,
+ struct share_check *sc)
+{
+ struct btrfs_fs_info *fs_info = extent_root->fs_info;
+ int ret;
+ int slot;
+ struct extent_buffer *leaf;
+ struct btrfs_key key;
+
+ while (1) {
+ ret = btrfs_next_item(extent_root, path);
+ if (ret < 0)
+ break;
+ if (ret) {
+ ret = 0;
+ break;
+ }
+
+ slot = path->slots[0];
+ leaf = path->nodes[0];
+ btrfs_item_key_to_cpu(leaf, &key, slot);
+
+ if (key.objectid != ctx->bytenr)
+ break;
+ if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
+ continue;
+ if (key.type > BTRFS_SHARED_DATA_REF_KEY)
+ break;
+
+ switch (key.type) {
+ case BTRFS_SHARED_BLOCK_REF_KEY:
+ /* SHARED DIRECT METADATA backref */
+ ret = add_direct_ref(fs_info, preftrees,
+ info_level + 1, key.offset,
+ ctx->bytenr, 1, NULL, GFP_NOFS);
+ break;
+ case BTRFS_SHARED_DATA_REF_KEY: {
+ /* SHARED DIRECT FULL backref */
+ struct btrfs_shared_data_ref *sdref;
+ int count;
+
+ sdref = btrfs_item_ptr(leaf, slot,
+ struct btrfs_shared_data_ref);
+ count = btrfs_shared_data_ref_count(leaf, sdref);
+ ret = add_direct_ref(fs_info, preftrees, 0,
+ key.offset, ctx->bytenr, count,
+ sc, GFP_NOFS);
+ break;
+ }
+ case BTRFS_TREE_BLOCK_REF_KEY:
+ /* NORMAL INDIRECT METADATA backref */
+ ret = add_indirect_ref(fs_info, preftrees, key.offset,
+ NULL, info_level + 1, ctx->bytenr,
+ 1, NULL, GFP_NOFS);
+ break;
+ case BTRFS_EXTENT_DATA_REF_KEY: {
+ /* NORMAL INDIRECT DATA backref */
+ struct btrfs_extent_data_ref *dref;
+ int count;
+ u64 root;
+
+ dref = btrfs_item_ptr(leaf, slot,
+ struct btrfs_extent_data_ref);
+ count = btrfs_extent_data_ref_count(leaf, dref);
+ key.objectid = btrfs_extent_data_ref_objectid(leaf,
+ dref);
+ key.type = BTRFS_EXTENT_DATA_KEY;
+ key.offset = btrfs_extent_data_ref_offset(leaf, dref);
+
+ if (sc && key.objectid != sc->inum &&
+ !sc->have_delayed_delete_refs) {
+ ret = BACKREF_FOUND_SHARED;
+ break;
+ }
+
+ root = btrfs_extent_data_ref_root(leaf, dref);
+
+ if (!ctx->skip_data_ref ||
+ !ctx->skip_data_ref(root, key.objectid, key.offset,
+ ctx->user_ctx))
+ ret = add_indirect_ref(fs_info, preftrees, root,
+ &key, 0, ctx->bytenr,
+ count, sc, GFP_NOFS);
+ break;
+ }
+ default:
+ WARN_ON(1);
+ }
+ if (ret)
+ return ret;
+
+ }
+
+ return ret;
+}
+
+/*
+ * The caller has joined a transaction or is holding a read lock on the
+ * fs_info->commit_root_sem semaphore, so no need to worry about the root's last
+ * snapshot field changing while updating or checking the cache.
+ */
+static bool lookup_backref_shared_cache(struct btrfs_backref_share_check_ctx *ctx,
+ struct btrfs_root *root,
+ u64 bytenr, int level, bool *is_shared)
+{
+ const struct btrfs_fs_info *fs_info = root->fs_info;
+ struct btrfs_backref_shared_cache_entry *entry;
+
+ if (!current->journal_info)
+ lockdep_assert_held(&fs_info->commit_root_sem);
+
+ if (!ctx->use_path_cache)
+ return false;
+
+ if (WARN_ON_ONCE(level >= BTRFS_MAX_LEVEL))
+ return false;
+
+ /*
+ * Level -1 is used for the data extent, which is not reliable to cache
+ * because its reference count can increase or decrease without us
+ * realizing. We cache results only for extent buffers that lead from
+ * the root node down to the leaf with the file extent item.
+ */
+ ASSERT(level >= 0);
+
+ entry = &ctx->path_cache_entries[level];
+
+ /* Unused cache entry or being used for some other extent buffer. */
+ if (entry->bytenr != bytenr)
+ return false;
+
+ /*
+ * We cached a false result, but the last snapshot generation of the
+ * root changed, so we now have a snapshot. Don't trust the result.
+ */
+ if (!entry->is_shared &&
+ entry->gen != btrfs_root_last_snapshot(&root->root_item))
+ return false;
+
+ /*
+ * If we cached a true result and the last generation used for dropping
+ * a root changed, we can not trust the result, because the dropped root
+ * could be a snapshot sharing this extent buffer.
+ */
+ if (entry->is_shared &&
+ entry->gen != btrfs_get_last_root_drop_gen(fs_info))
+ return false;
+
+ *is_shared = entry->is_shared;
+ /*
+ * If the node at this level is shared, than all nodes below are also
+ * shared. Currently some of the nodes below may be marked as not shared
+ * because we have just switched from one leaf to another, and switched
+ * also other nodes above the leaf and below the current level, so mark
+ * them as shared.
+ */
+ if (*is_shared) {
+ for (int i = 0; i < level; i++) {
+ ctx->path_cache_entries[i].is_shared = true;
+ ctx->path_cache_entries[i].gen = entry->gen;
+ }
+ }
+
+ return true;
+}
+
+/*
+ * The caller has joined a transaction or is holding a read lock on the
+ * fs_info->commit_root_sem semaphore, so no need to worry about the root's last
+ * snapshot field changing while updating or checking the cache.
+ */
+static void store_backref_shared_cache(struct btrfs_backref_share_check_ctx *ctx,
+ struct btrfs_root *root,
+ u64 bytenr, int level, bool is_shared)
+{
+ const struct btrfs_fs_info *fs_info = root->fs_info;
+ struct btrfs_backref_shared_cache_entry *entry;
+ u64 gen;
+
+ if (!current->journal_info)
+ lockdep_assert_held(&fs_info->commit_root_sem);
+
+ if (!ctx->use_path_cache)
+ return;
+
+ if (WARN_ON_ONCE(level >= BTRFS_MAX_LEVEL))
+ return;
+
+ /*
+ * Level -1 is used for the data extent, which is not reliable to cache
+ * because its reference count can increase or decrease without us
+ * realizing. We cache results only for extent buffers that lead from
+ * the root node down to the leaf with the file extent item.
+ */
+ ASSERT(level >= 0);
+
+ if (is_shared)
+ gen = btrfs_get_last_root_drop_gen(fs_info);
+ else
+ gen = btrfs_root_last_snapshot(&root->root_item);
+
+ entry = &ctx->path_cache_entries[level];
+ entry->bytenr = bytenr;
+ entry->is_shared = is_shared;
+ entry->gen = gen;
+
+ /*
+ * If we found an extent buffer is shared, set the cache result for all
+ * extent buffers below it to true. As nodes in the path are COWed,
+ * their sharedness is moved to their children, and if a leaf is COWed,
+ * then the sharedness of a data extent becomes direct, the refcount of
+ * data extent is increased in the extent item at the extent tree.
+ */
+ if (is_shared) {
+ for (int i = 0; i < level; i++) {
+ entry = &ctx->path_cache_entries[i];
+ entry->is_shared = is_shared;
+ entry->gen = gen;
+ }
+ }
+}
+
+/*
+ * this adds all existing backrefs (inline backrefs, backrefs and delayed
+ * refs) for the given bytenr to the refs list, merges duplicates and resolves
+ * indirect refs to their parent bytenr.
+ * When roots are found, they're added to the roots list
+ *
+ * @ctx: Backref walking context object, must be not NULL.
+ * @sc: If !NULL, then immediately return BACKREF_FOUND_SHARED when a
+ * shared extent is detected.
+ *
+ * Otherwise this returns 0 for success and <0 for an error.
+ *
+ * FIXME some caching might speed things up
+ */
+static int find_parent_nodes(struct btrfs_backref_walk_ctx *ctx,
+ struct share_check *sc)
+{
+ struct btrfs_root *root = btrfs_extent_root(ctx->fs_info, ctx->bytenr);
+ struct btrfs_key key;
+ struct btrfs_path *path;
+ struct btrfs_delayed_ref_root *delayed_refs = NULL;
+ struct btrfs_delayed_ref_head *head;
+ int info_level = 0;
+ int ret;
+ struct prelim_ref *ref;
+ struct rb_node *node;
+ struct extent_inode_elem *eie = NULL;
+ struct preftrees preftrees = {
+ .direct = PREFTREE_INIT,
+ .indirect = PREFTREE_INIT,
+ .indirect_missing_keys = PREFTREE_INIT
+ };
+
+ /* Roots ulist is not needed when using a sharedness check context. */
+ if (sc)
+ ASSERT(ctx->roots == NULL);
+
+ key.objectid = ctx->bytenr;
+ key.offset = (u64)-1;
+ if (btrfs_fs_incompat(ctx->fs_info, SKINNY_METADATA))
+ key.type = BTRFS_METADATA_ITEM_KEY;
+ else
+ key.type = BTRFS_EXTENT_ITEM_KEY;
+
+ path = btrfs_alloc_path();
+ if (!path)
+ return -ENOMEM;
+ if (!ctx->trans) {
+ path->search_commit_root = 1;
+ path->skip_locking = 1;
+ }
+
+ if (ctx->time_seq == BTRFS_SEQ_LAST)
+ path->skip_locking = 1;
+
+again:
+ head = NULL;
+
+ ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+ if (ret < 0)
+ goto out;
+ if (ret == 0) {
+ /* This shouldn't happen, indicates a bug or fs corruption. */
+ ASSERT(ret != 0);
+ ret = -EUCLEAN;
+ goto out;
+ }
+
+ if (ctx->trans && likely(ctx->trans->type != __TRANS_DUMMY) &&
+ ctx->time_seq != BTRFS_SEQ_LAST) {
+ /*
+ * We have a specific time_seq we care about and trans which
+ * means we have the path lock, we need to grab the ref head and
+ * lock it so we have a consistent view of the refs at the given
+ * time.
+ */
+ delayed_refs = &ctx->trans->transaction->delayed_refs;
+ spin_lock(&delayed_refs->lock);
+ head = btrfs_find_delayed_ref_head(delayed_refs, ctx->bytenr);
+ if (head) {
+ if (!mutex_trylock(&head->mutex)) {
+ refcount_inc(&head->refs);
+ spin_unlock(&delayed_refs->lock);
+
+ btrfs_release_path(path);
+
+ /*
+ * Mutex was contended, block until it's
+ * released and try again
+ */
+ mutex_lock(&head->mutex);
+ mutex_unlock(&head->mutex);
+ btrfs_put_delayed_ref_head(head);
+ goto again;
+ }
+ spin_unlock(&delayed_refs->lock);
+ ret = add_delayed_refs(ctx->fs_info, head, ctx->time_seq,
+ &preftrees, sc);
+ mutex_unlock(&head->mutex);
+ if (ret)
+ goto out;
+ } else {
+ spin_unlock(&delayed_refs->lock);
+ }
+ }
+
+ if (path->slots[0]) {
+ struct extent_buffer *leaf;
+ int slot;
+
+ path->slots[0]--;
+ leaf = path->nodes[0];
+ slot = path->slots[0];
+ btrfs_item_key_to_cpu(leaf, &key, slot);
+ if (key.objectid == ctx->bytenr &&
+ (key.type == BTRFS_EXTENT_ITEM_KEY ||
+ key.type == BTRFS_METADATA_ITEM_KEY)) {
+ ret = add_inline_refs(ctx, path, &info_level,
+ &preftrees, sc);
+ if (ret)
+ goto out;
+ ret = add_keyed_refs(ctx, root, path, info_level,
+ &preftrees, sc);
+ if (ret)
+ goto out;
+ }
+ }
+
+ /*
+ * If we have a share context and we reached here, it means the extent
+ * is not directly shared (no multiple reference items for it),
+ * otherwise we would have exited earlier with a return value of
+ * BACKREF_FOUND_SHARED after processing delayed references or while
+ * processing inline or keyed references from the extent tree.
+ * The extent may however be indirectly shared through shared subtrees
+ * as a result from creating snapshots, so we determine below what is
+ * its parent node, in case we are dealing with a metadata extent, or
+ * what's the leaf (or leaves), from a fs tree, that has a file extent
+ * item pointing to it in case we are dealing with a data extent.
+ */
+ ASSERT(extent_is_shared(sc) == 0);
+
+ /*
+ * If we are here for a data extent and we have a share_check structure
+ * it means the data extent is not directly shared (does not have
+ * multiple reference items), so we have to check if a path in the fs
+ * tree (going from the root node down to the leaf that has the file
+ * extent item pointing to the data extent) is shared, that is, if any
+ * of the extent buffers in the path is referenced by other trees.
+ */
+ if (sc && ctx->bytenr == sc->data_bytenr) {
+ /*
+ * If our data extent is from a generation more recent than the
+ * last generation used to snapshot the root, then we know that
+ * it can not be shared through subtrees, so we can skip
+ * resolving indirect references, there's no point in
+ * determining the extent buffers for the path from the fs tree
+ * root node down to the leaf that has the file extent item that
+ * points to the data extent.
+ */
+ if (sc->data_extent_gen >
+ btrfs_root_last_snapshot(&sc->root->root_item)) {
+ ret = BACKREF_FOUND_NOT_SHARED;
+ goto out;
+ }
+
+ /*
+ * If we are only determining if a data extent is shared or not
+ * and the corresponding file extent item is located in the same
+ * leaf as the previous file extent item, we can skip resolving
+ * indirect references for a data extent, since the fs tree path
+ * is the same (same leaf, so same path). We skip as long as the
+ * cached result for the leaf is valid and only if there's only
+ * one file extent item pointing to the data extent, because in
+ * the case of multiple file extent items, they may be located
+ * in different leaves and therefore we have multiple paths.
+ */
+ if (sc->ctx->curr_leaf_bytenr == sc->ctx->prev_leaf_bytenr &&
+ sc->self_ref_count == 1) {
+ bool cached;
+ bool is_shared;
+
+ cached = lookup_backref_shared_cache(sc->ctx, sc->root,
+ sc->ctx->curr_leaf_bytenr,
+ 0, &is_shared);
+ if (cached) {
+ if (is_shared)
+ ret = BACKREF_FOUND_SHARED;
+ else
+ ret = BACKREF_FOUND_NOT_SHARED;
+ goto out;
+ }
+ }
+ }
+
+ btrfs_release_path(path);
+
+ ret = add_missing_keys(ctx->fs_info, &preftrees, path->skip_locking == 0);
+ if (ret)
+ goto out;
+
+ WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect_missing_keys.root.rb_root));
+
+ ret = resolve_indirect_refs(ctx, path, &preftrees, sc);
+ if (ret)
+ goto out;
+
+ WARN_ON(!RB_EMPTY_ROOT(&preftrees.indirect.root.rb_root));
+
+ /*
+ * This walks the tree of merged and resolved refs. Tree blocks are
+ * read in as needed. Unique entries are added to the ulist, and
+ * the list of found roots is updated.
+ *
+ * We release the entire tree in one go before returning.
+ */
+ node = rb_first_cached(&preftrees.direct.root);
+ while (node) {
+ ref = rb_entry(node, struct prelim_ref, rbnode);
+ node = rb_next(&ref->rbnode);
+ /*
+ * ref->count < 0 can happen here if there are delayed
+ * refs with a node->action of BTRFS_DROP_DELAYED_REF.
+ * prelim_ref_insert() relies on this when merging
+ * identical refs to keep the overall count correct.
+ * prelim_ref_insert() will merge only those refs
+ * which compare identically. Any refs having
+ * e.g. different offsets would not be merged,
+ * and would retain their original ref->count < 0.
+ */
+ if (ctx->roots && ref->count && ref->root_id && ref->parent == 0) {
+ /* no parent == root of tree */
+ ret = ulist_add(ctx->roots, ref->root_id, 0, GFP_NOFS);
+ if (ret < 0)
+ goto out;
+ }
+ if (ref->count && ref->parent) {
+ if (!ctx->skip_inode_ref_list && !ref->inode_list &&
+ ref->level == 0) {
+ struct btrfs_tree_parent_check check = { 0 };
+ struct extent_buffer *eb;
+
+ check.level = ref->level;
+
+ eb = read_tree_block(ctx->fs_info, ref->parent,
+ &check);
+ if (IS_ERR(eb)) {
+ ret = PTR_ERR(eb);
+ goto out;
+ }
+ if (!extent_buffer_uptodate(eb)) {
+ free_extent_buffer(eb);
+ ret = -EIO;
+ goto out;
+ }
+
+ if (!path->skip_locking)
+ btrfs_tree_read_lock(eb);
+ ret = find_extent_in_eb(ctx, eb, &eie);
+ if (!path->skip_locking)
+ btrfs_tree_read_unlock(eb);
+ free_extent_buffer(eb);
+ if (ret == BTRFS_ITERATE_EXTENT_INODES_STOP ||
+ ret < 0)
+ goto out;
+ ref->inode_list = eie;
+ /*
+ * We transferred the list ownership to the ref,
+ * so set to NULL to avoid a double free in case
+ * an error happens after this.
+ */
+ eie = NULL;
+ }
+ ret = ulist_add_merge_ptr(ctx->refs, ref->parent,
+ ref->inode_list,
+ (void **)&eie, GFP_NOFS);
+ if (ret < 0)
+ goto out;
+ if (!ret && !ctx->skip_inode_ref_list) {
+ /*
+ * We've recorded that parent, so we must extend
+ * its inode list here.
+ *
+ * However if there was corruption we may not
+ * have found an eie, return an error in this
+ * case.
+ */
+ ASSERT(eie);
+ if (!eie) {
+ ret = -EUCLEAN;
+ goto out;
+ }
+ while (eie->next)
+ eie = eie->next;
+ eie->next = ref->inode_list;
+ }
+ eie = NULL;
+ /*
+ * We have transferred the inode list ownership from
+ * this ref to the ref we added to the 'refs' ulist.
+ * So set this ref's inode list to NULL to avoid
+ * use-after-free when our caller uses it or double
+ * frees in case an error happens before we return.
+ */
+ ref->inode_list = NULL;
+ }
+ cond_resched();
+ }
+
+out:
+ btrfs_free_path(path);
+
+ prelim_release(&preftrees.direct);
+ prelim_release(&preftrees.indirect);
+ prelim_release(&preftrees.indirect_missing_keys);
+
+ if (ret == BTRFS_ITERATE_EXTENT_INODES_STOP || ret < 0)
+ free_inode_elem_list(eie);
+ return ret;
+}
+
+/*
+ * Finds all leaves with a reference to the specified combination of
+ * @ctx->bytenr and @ctx->extent_item_pos. The bytenr of the found leaves are
+ * added to the ulist at @ctx->refs, and that ulist is allocated by this
+ * function. The caller should free the ulist with free_leaf_list() if
+ * @ctx->ignore_extent_item_pos is false, otherwise a fimple ulist_free() is
+ * enough.
+ *
+ * Returns 0 on success and < 0 on error. On error @ctx->refs is not allocated.
+ */
+int btrfs_find_all_leafs(struct btrfs_backref_walk_ctx *ctx)
+{
+ int ret;
+
+ ASSERT(ctx->refs == NULL);
+
+ ctx->refs = ulist_alloc(GFP_NOFS);
+ if (!ctx->refs)
+ return -ENOMEM;
+
+ ret = find_parent_nodes(ctx, NULL);
+ if (ret == BTRFS_ITERATE_EXTENT_INODES_STOP ||
+ (ret < 0 && ret != -ENOENT)) {
+ free_leaf_list(ctx->refs);
+ ctx->refs = NULL;
+ return ret;
+ }
+
+ return 0;
+}
+
+/*
+ * Walk all backrefs for a given extent to find all roots that reference this
+ * extent. Walking a backref means finding all extents that reference this
+ * extent and in turn walk the backrefs of those, too. Naturally this is a
+ * recursive process, but here it is implemented in an iterative fashion: We
+ * find all referencing extents for the extent in question and put them on a
+ * list. In turn, we find all referencing extents for those, further appending
+ * to the list. The way we iterate the list allows adding more elements after
+ * the current while iterating. The process stops when we reach the end of the
+ * list.
+ *
+ * Found roots are added to @ctx->roots, which is allocated by this function if
+ * it points to NULL, in which case the caller is responsible for freeing it
+ * after it's not needed anymore.
+ * This function requires @ctx->refs to be NULL, as it uses it for allocating a
+ * ulist to do temporary work, and frees it before returning.
+ *
+ * Returns 0 on success, < 0 on error.
+ */
+static int btrfs_find_all_roots_safe(struct btrfs_backref_walk_ctx *ctx)
+{
+ const u64 orig_bytenr = ctx->bytenr;
+ const bool orig_skip_inode_ref_list = ctx->skip_inode_ref_list;
+ bool roots_ulist_allocated = false;
+ struct ulist_iterator uiter;
+ int ret = 0;
+
+ ASSERT(ctx->refs == NULL);
+
+ ctx->refs = ulist_alloc(GFP_NOFS);
+ if (!ctx->refs)
+ return -ENOMEM;
+
+ if (!ctx->roots) {
+ ctx->roots = ulist_alloc(GFP_NOFS);
+ if (!ctx->roots) {
+ ulist_free(ctx->refs);
+ ctx->refs = NULL;
+ return -ENOMEM;
+ }
+ roots_ulist_allocated = true;
+ }
+
+ ctx->skip_inode_ref_list = true;
+
+ ULIST_ITER_INIT(&uiter);
+ while (1) {
+ struct ulist_node *node;
+
+ ret = find_parent_nodes(ctx, NULL);
+ if (ret < 0 && ret != -ENOENT) {
+ if (roots_ulist_allocated) {
+ ulist_free(ctx->roots);
+ ctx->roots = NULL;
+ }
+ break;
+ }
+ ret = 0;
+ node = ulist_next(ctx->refs, &uiter);
+ if (!node)
+ break;
+ ctx->bytenr = node->val;
+ cond_resched();
+ }
+
+ ulist_free(ctx->refs);
+ ctx->refs = NULL;
+ ctx->bytenr = orig_bytenr;
+ ctx->skip_inode_ref_list = orig_skip_inode_ref_list;
+
+ return ret;
+}
+
+int btrfs_find_all_roots(struct btrfs_backref_walk_ctx *ctx,
+ bool skip_commit_root_sem)
+{
+ int ret;
+
+ if (!ctx->trans && !skip_commit_root_sem)
+ down_read(&ctx->fs_info->commit_root_sem);
+ ret = btrfs_find_all_roots_safe(ctx);
+ if (!ctx->trans && !skip_commit_root_sem)
+ up_read(&ctx->fs_info->commit_root_sem);
+ return ret;
+}
+
+struct btrfs_backref_share_check_ctx *btrfs_alloc_backref_share_check_ctx(void)
+{
+ struct btrfs_backref_share_check_ctx *ctx;
+
+ ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+ if (!ctx)
+ return NULL;
+
+ ulist_init(&ctx->refs);
+
+ return ctx;
+}
+
+void btrfs_free_backref_share_ctx(struct btrfs_backref_share_check_ctx *ctx)
+{
+ if (!ctx)
+ return;
+
+ ulist_release(&ctx->refs);
+ kfree(ctx);
+}
+
+/*
+ * Check if a data extent is shared or not.
+ *
+ * @inode: The inode whose extent we are checking.
+ * @bytenr: Logical bytenr of the extent we are checking.
+ * @extent_gen: Generation of the extent (file extent item) or 0 if it is
+ * not known.
+ * @ctx: A backref sharedness check context.
+ *
+ * btrfs_is_data_extent_shared uses the backref walking code but will short
+ * circuit as soon as it finds a root or inode that doesn't match the
+ * one passed in. This provides a significant performance benefit for
+ * callers (such as fiemap) which want to know whether the extent is
+ * shared but do not need a ref count.
+ *
+ * This attempts to attach to the running transaction in order to account for
+ * delayed refs, but continues on even when no running transaction exists.
+ *
+ * Return: 0 if extent is not shared, 1 if it is shared, < 0 on error.
+ */
+int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
+ u64 extent_gen,
+ struct btrfs_backref_share_check_ctx *ctx)
+{
+ struct btrfs_backref_walk_ctx walk_ctx = { 0 };
+ struct btrfs_root *root = inode->root;
+ struct btrfs_fs_info *fs_info = root->fs_info;
+ struct btrfs_trans_handle *trans;
+ struct ulist_iterator uiter;
+ struct ulist_node *node;
+ struct btrfs_seq_list elem = BTRFS_SEQ_LIST_INIT(elem);
+ int ret = 0;
+ struct share_check shared = {
+ .ctx = ctx,
+ .root = root,
+ .inum = btrfs_ino(inode),
+ .data_bytenr = bytenr,
+ .data_extent_gen = extent_gen,
+ .share_count = 0,
+ .self_ref_count = 0,
+ .have_delayed_delete_refs = false,
+ };
+ int level;
+ bool leaf_cached;
+ bool leaf_is_shared;
+
+ for (int i = 0; i < BTRFS_BACKREF_CTX_PREV_EXTENTS_SIZE; i++) {
+ if (ctx->prev_extents_cache[i].bytenr == bytenr)
+ return ctx->prev_extents_cache[i].is_shared;
+ }
+
+ ulist_init(&ctx->refs);
+
+ trans = btrfs_join_transaction_nostart(root);
+ if (IS_ERR(trans)) {
+ if (PTR_ERR(trans) != -ENOENT && PTR_ERR(trans) != -EROFS) {
+ ret = PTR_ERR(trans);
+ goto out;
+ }
+ trans = NULL;
+ down_read(&fs_info->commit_root_sem);
+ } else {
+ btrfs_get_tree_mod_seq(fs_info, &elem);
+ walk_ctx.time_seq = elem.seq;
+ }
+
+ ctx->use_path_cache = true;
+
+ /*
+ * We may have previously determined that the current leaf is shared.
+ * If it is, then we have a data extent that is shared due to a shared
+ * subtree (caused by snapshotting) and we don't need to check for data
+ * backrefs. If the leaf is not shared, then we must do backref walking
+ * to determine if the data extent is shared through reflinks.
+ */
+ leaf_cached = lookup_backref_shared_cache(ctx, root,
+ ctx->curr_leaf_bytenr, 0,
+ &leaf_is_shared);
+ if (leaf_cached && leaf_is_shared) {
+ ret = 1;
+ goto out_trans;
+ }
+
+ walk_ctx.skip_inode_ref_list = true;
+ walk_ctx.trans = trans;
+ walk_ctx.fs_info = fs_info;
+ walk_ctx.refs = &ctx->refs;
+
+ /* -1 means we are in the bytenr of the data extent. */
+ level = -1;
+ ULIST_ITER_INIT(&uiter);
+ while (1) {
+ const unsigned long prev_ref_count = ctx->refs.nnodes;
+
+ walk_ctx.bytenr = bytenr;
+ ret = find_parent_nodes(&walk_ctx, &shared);
+ if (ret == BACKREF_FOUND_SHARED ||
+ ret == BACKREF_FOUND_NOT_SHARED) {
+ /* If shared must return 1, otherwise return 0. */
+ ret = (ret == BACKREF_FOUND_SHARED) ? 1 : 0;
+ if (level >= 0)
+ store_backref_shared_cache(ctx, root, bytenr,
+ level, ret == 1);
+ break;
+ }
+ if (ret < 0 && ret != -ENOENT)
+ break;
+ ret = 0;
+
+ /*
+ * More than one extent buffer (bytenr) may have been added to
+ * the ctx->refs ulist, in which case we have to check multiple
+ * tree paths in case the first one is not shared, so we can not
+ * use the path cache which is made for a single path. Multiple
+ * extent buffers at the current level happen when:
+ *
+ * 1) level -1, the data extent: If our data extent was not
+ * directly shared (without multiple reference items), then
+ * it might have a single reference item with a count > 1 for
+ * the same offset, which means there are 2 (or more) file
+ * extent items that point to the data extent - this happens
+ * when a file extent item needs to be split and then one
+ * item gets moved to another leaf due to a b+tree leaf split
+ * when inserting some item. In this case the file extent
+ * items may be located in different leaves and therefore
+ * some of the leaves may be referenced through shared
+ * subtrees while others are not. Since our extent buffer
+ * cache only works for a single path (by far the most common
+ * case and simpler to deal with), we can not use it if we
+ * have multiple leaves (which implies multiple paths).
+ *
+ * 2) level >= 0, a tree node/leaf: We can have a mix of direct
+ * and indirect references on a b+tree node/leaf, so we have
+ * to check multiple paths, and the extent buffer (the
+ * current bytenr) may be shared or not. One example is
+ * during relocation as we may get a shared tree block ref
+ * (direct ref) and a non-shared tree block ref (indirect
+ * ref) for the same node/leaf.
+ */
+ if ((ctx->refs.nnodes - prev_ref_count) > 1)
+ ctx->use_path_cache = false;
+
+ if (level >= 0)
+ store_backref_shared_cache(ctx, root, bytenr,
+ level, false);
+ node = ulist_next(&ctx->refs, &uiter);
+ if (!node)
+ break;
+ bytenr = node->val;
+ if (ctx->use_path_cache) {
+ bool is_shared;
+ bool cached;
+
+ level++;
+ cached = lookup_backref_shared_cache(ctx, root, bytenr,
+ level, &is_shared);
+ if (cached) {
+ ret = (is_shared ? 1 : 0);
+ break;
+ }
+ }
+ shared.share_count = 0;
+ shared.have_delayed_delete_refs = false;
+ cond_resched();
+ }
+
+ /*
+ * If the path cache is disabled, then it means at some tree level we
+ * got multiple parents due to a mix of direct and indirect backrefs or
+ * multiple leaves with file extent items pointing to the same data
+ * extent. We have to invalidate the cache and cache only the sharedness
+ * result for the levels where we got only one node/reference.
+ */
+ if (!ctx->use_path_cache) {
+ int i = 0;
+
+ level--;
+ if (ret >= 0 && level >= 0) {
+ bytenr = ctx->path_cache_entries[level].bytenr;
+ ctx->use_path_cache = true;
+ store_backref_shared_cache(ctx, root, bytenr, level, ret);
+ i = level + 1;
+ }
+
+ for ( ; i < BTRFS_MAX_LEVEL; i++)
+ ctx->path_cache_entries[i].bytenr = 0;
+ }
+
+ /*
+ * Cache the sharedness result for the data extent if we know our inode
+ * has more than 1 file extent item that refers to the data extent.
+ */
+ if (ret >= 0 && shared.self_ref_count > 1) {
+ int slot = ctx->prev_extents_cache_slot;
+
+ ctx->prev_extents_cache[slot].bytenr = shared.data_bytenr;
+ ctx->prev_extents_cache[slot].is_shared = (ret == 1);
+
+ slot = (slot + 1) % BTRFS_BACKREF_CTX_PREV_EXTENTS_SIZE;
+ ctx->prev_extents_cache_slot = slot;
+ }
+
+out_trans:
+ if (trans) {
+ btrfs_put_tree_mod_seq(fs_info, &elem);
+ btrfs_end_transaction(trans);
+ } else {
+ up_read(&fs_info->commit_root_sem);
+ }
+out:
+ ulist_release(&ctx->refs);
+ ctx->prev_leaf_bytenr = ctx->curr_leaf_bytenr;
+
+ return ret;
+}
+
+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 ret, slot;
+ struct btrfs_key key;
+ struct btrfs_key found_key;
+ struct btrfs_inode_extref *extref;
+ const struct extent_buffer *leaf;
+ unsigned long ptr;
+
+ key.objectid = inode_objectid;
+ key.type = BTRFS_INODE_EXTREF_KEY;
+ key.offset = start_off;
+
+ ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+ if (ret < 0)
+ return ret;
+
+ while (1) {
+ leaf = path->nodes[0];
+ slot = path->slots[0];
+ if (slot >= btrfs_header_nritems(leaf)) {
+ /*
+ * If the item at offset is not found,
+ * btrfs_search_slot will point us to the slot
+ * where it should be inserted. In our case
+ * that will be the slot directly before the
+ * next INODE_REF_KEY_V2 item. In the case
+ * that we're pointing to the last slot in a
+ * leaf, we must move one leaf over.
+ */
+ ret = btrfs_next_leaf(root, path);
+ if (ret) {
+ if (ret >= 1)
+ ret = -ENOENT;
+ break;
+ }
+ continue;
+ }
+
+ btrfs_item_key_to_cpu(leaf, &found_key, slot);
+
+ /*
+ * Check that we're still looking at an extended ref key for
+ * this particular objectid. If we have different
+ * objectid or type then there are no more to be found
+ * in the tree and we can exit.
+ */
+ ret = -ENOENT;
+ if (found_key.objectid != inode_objectid)
+ break;
+ if (found_key.type != BTRFS_INODE_EXTREF_KEY)
+ break;
+
+ ret = 0;
+ ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
+ extref = (struct btrfs_inode_extref *)ptr;
+ *ret_extref = extref;
+ if (found_off)
+ *found_off = found_key.offset;
+ break;
+ }
+
+ return ret;
+}
+
+/*
+ * this iterates to turn a name (from iref/extref) into a full filesystem path.
+ * Elements of the path are separated by '/' and the path is guaranteed to be
+ * 0-terminated. the path is only given within the current file system.
+ * Therefore, it never starts with a '/'. the caller is responsible to provide
+ * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
+ * the start point of the resulting string is returned. this pointer is within
+ * dest, normally.
+ * in case the path buffer would overflow, the pointer is decremented further
+ * as if output was written to the buffer, though no more output is actually
+ * generated. that way, the caller can determine how much space would be
+ * required for the path to fit into the buffer. in that case, the returned
+ * value will be smaller than dest. callers must check this!
+ */
+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)
+{
+ int slot;
+ u64 next_inum;
+ int ret;
+ s64 bytes_left = ((s64)size) - 1;
+ struct extent_buffer *eb = eb_in;
+ struct btrfs_key found_key;
+ struct btrfs_inode_ref *iref;
+
+ if (bytes_left >= 0)
+ dest[bytes_left] = '\0';
+
+ while (1) {
+ bytes_left -= name_len;
+ if (bytes_left >= 0)
+ read_extent_buffer(eb, dest + bytes_left,
+ name_off, name_len);
+ if (eb != eb_in) {
+ if (!path->skip_locking)
+ btrfs_tree_read_unlock(eb);
+ free_extent_buffer(eb);
+ }
+ ret = btrfs_find_item(fs_root, path, parent, 0,
+ BTRFS_INODE_REF_KEY, &found_key);
+ if (ret > 0)
+ ret = -ENOENT;
+ if (ret)
+ break;
+
+ next_inum = found_key.offset;
+
+ /* regular exit ahead */
+ if (parent == next_inum)
+ break;
+
+ slot = path->slots[0];
+ eb = path->nodes[0];
+ /* make sure we can use eb after releasing the path */
+ if (eb != eb_in) {
+ path->nodes[0] = NULL;
+ path->locks[0] = 0;
+ }
+ btrfs_release_path(path);
+ iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
+
+ name_len = btrfs_inode_ref_name_len(eb, iref);
+ name_off = (unsigned long)(iref + 1);
+
+ parent = next_inum;
+ --bytes_left;
+ if (bytes_left >= 0)
+ dest[bytes_left] = '/';
+ }
+
+ btrfs_release_path(path);
+
+ if (ret)
+ return ERR_PTR(ret);
+
+ return dest + bytes_left;
+}
+
+/*
+ * this makes the path point to (logical EXTENT_ITEM *)
+ * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
+ * tree blocks and <0 on error.
+ */
+int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
+ struct btrfs_path *path, struct btrfs_key *found_key,
+ u64 *flags_ret)
+{
+ struct btrfs_root *extent_root = btrfs_extent_root(fs_info, logical);
+ int ret;
+ u64 flags;
+ u64 size = 0;
+ u32 item_size;
+ const struct extent_buffer *eb;
+ struct btrfs_extent_item *ei;
+ struct btrfs_key key;
+
+ if (btrfs_fs_incompat(fs_info, SKINNY_METADATA))
+ key.type = BTRFS_METADATA_ITEM_KEY;
+ else
+ key.type = BTRFS_EXTENT_ITEM_KEY;
+ key.objectid = logical;
+ key.offset = (u64)-1;
+
+ ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
+ if (ret < 0)
+ return ret;
+
+ ret = btrfs_previous_extent_item(extent_root, path, 0);
+ if (ret) {
+ if (ret > 0)
+ ret = -ENOENT;
+ return ret;
+ }
+ btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
+ if (found_key->type == BTRFS_METADATA_ITEM_KEY)
+ size = fs_info->nodesize;
+ else if (found_key->type == BTRFS_EXTENT_ITEM_KEY)
+ size = found_key->offset;
+
+ if (found_key->objectid > logical ||
+ found_key->objectid + size <= logical) {
+ btrfs_debug(fs_info,
+ "logical %llu is not within any extent", logical);
+ return -ENOENT;
+ }
+
+ eb = path->nodes[0];
+ item_size = btrfs_item_size(eb, path->slots[0]);
+ BUG_ON(item_size < sizeof(*ei));
+
+ ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
+ flags = btrfs_extent_flags(eb, ei);
+
+ btrfs_debug(fs_info,
+ "logical %llu is at position %llu within the extent (%llu EXTENT_ITEM %llu) flags %#llx size %u",
+ logical, logical - found_key->objectid, found_key->objectid,
+ found_key->offset, flags, item_size);
+
+ WARN_ON(!flags_ret);
+ if (flags_ret) {
+ if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
+ *flags_ret = BTRFS_EXTENT_FLAG_TREE_BLOCK;
+ else if (flags & BTRFS_EXTENT_FLAG_DATA)
+ *flags_ret = BTRFS_EXTENT_FLAG_DATA;
+ else
+ BUG();
+ return 0;
+ }
+
+ return -EIO;
+}
+
+/*
+ * helper function to iterate extent inline refs. ptr must point to a 0 value
+ * for the first call and may be modified. it is used to track state.
+ * if more refs exist, 0 is returned and the next call to
+ * get_extent_inline_ref must pass the modified ptr parameter to get the
+ * next ref. after the last ref was processed, 1 is returned.
+ * returns <0 on error
+ */
+static int get_extent_inline_ref(unsigned long *ptr,
+ const struct extent_buffer *eb,
+ const struct btrfs_key *key,
+ const struct btrfs_extent_item *ei,
+ u32 item_size,
+ struct btrfs_extent_inline_ref **out_eiref,
+ int *out_type)
+{
+ unsigned long end;
+ u64 flags;
+ struct btrfs_tree_block_info *info;
+
+ if (!*ptr) {
+ /* first call */
+ flags = btrfs_extent_flags(eb, ei);
+ if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
+ if (key->type == BTRFS_METADATA_ITEM_KEY) {
+ /* a skinny metadata extent */
+ *out_eiref =
+ (struct btrfs_extent_inline_ref *)(ei + 1);
+ } else {
+ WARN_ON(key->type != BTRFS_EXTENT_ITEM_KEY);
+ info = (struct btrfs_tree_block_info *)(ei + 1);
+ *out_eiref =
+ (struct btrfs_extent_inline_ref *)(info + 1);
+ }
+ } else {
+ *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
+ }
+ *ptr = (unsigned long)*out_eiref;
+ if ((unsigned long)(*ptr) >= (unsigned long)ei + item_size)
+ return -ENOENT;
+ }
+
+ end = (unsigned long)ei + item_size;
+ *out_eiref = (struct btrfs_extent_inline_ref *)(*ptr);
+ *out_type = btrfs_get_extent_inline_ref_type(eb, *out_eiref,
+ BTRFS_REF_TYPE_ANY);
+ if (*out_type == BTRFS_REF_TYPE_INVALID)
+ return -EUCLEAN;
+
+ *ptr += btrfs_extent_inline_ref_size(*out_type);
+ WARN_ON(*ptr > end);
+ if (*ptr == end)
+ return 1; /* last */
+
+ return 0;
+}
+
+/*
+ * reads the tree block backref for an extent. tree level and root are returned
+ * through out_level and out_root. ptr must point to a 0 value for the first
+ * call and may be modified (see get_extent_inline_ref comment).
+ * returns 0 if data was provided, 1 if there was no more data to provide or
+ * <0 on error.
+ */
+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 ret;
+ int type;
+ struct btrfs_extent_inline_ref *eiref;
+
+ if (*ptr == (unsigned long)-1)
+ return 1;
+
+ while (1) {
+ ret = get_extent_inline_ref(ptr, eb, key, ei, item_size,
+ &eiref, &type);
+ if (ret < 0)
+ return ret;
+
+ if (type == BTRFS_TREE_BLOCK_REF_KEY ||
+ type == BTRFS_SHARED_BLOCK_REF_KEY)
+ break;
+
+ if (ret == 1)
+ return 1;
+ }
+
+ /* we can treat both ref types equally here */
+ *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
+
+ if (key->type == BTRFS_EXTENT_ITEM_KEY) {
+ struct btrfs_tree_block_info *info;
+
+ info = (struct btrfs_tree_block_info *)(ei + 1);
+ *out_level = btrfs_tree_block_level(eb, info);
+ } else {
+ ASSERT(key->type == BTRFS_METADATA_ITEM_KEY);
+ *out_level = (u8)key->offset;
+ }
+
+ if (ret == 1)
+ *ptr = (unsigned long)-1;
+
+ return 0;
+}
+
+static int iterate_leaf_refs(struct btrfs_fs_info *fs_info,
+ struct extent_inode_elem *inode_list,
+ u64 root, u64 extent_item_objectid,
+ iterate_extent_inodes_t *iterate, void *ctx)
+{
+ struct extent_inode_elem *eie;
+ int ret = 0;
+
+ for (eie = inode_list; eie; eie = eie->next) {
+ btrfs_debug(fs_info,
+ "ref for %llu resolved, key (%llu EXTEND_DATA %llu), root %llu",
+ extent_item_objectid, eie->inum,
+ eie->offset, root);
+ ret = iterate(eie->inum, eie->offset, eie->num_bytes, root, ctx);
+ if (ret) {
+ btrfs_debug(fs_info,
+ "stopping iteration for %llu due to ret=%d",
+ extent_item_objectid, ret);
+ break;
+ }
+ }
+
+ return ret;
+}
+
+/*
+ * calls iterate() for every inode that references the extent identified by
+ * the given parameters.
+ * when the iterator function returns a non-zero value, iteration stops.
+ */
+int iterate_extent_inodes(struct btrfs_backref_walk_ctx *ctx,
+ bool search_commit_root,
+ iterate_extent_inodes_t *iterate, void *user_ctx)
+{
+ int ret;
+ struct ulist *refs;
+ struct ulist_node *ref_node;
+ struct btrfs_seq_list seq_elem = BTRFS_SEQ_LIST_INIT(seq_elem);
+ struct ulist_iterator ref_uiter;
+
+ btrfs_debug(ctx->fs_info, "resolving all inodes for extent %llu",
+ ctx->bytenr);
+
+ ASSERT(ctx->trans == NULL);
+ ASSERT(ctx->roots == NULL);
+
+ if (!search_commit_root) {
+ struct btrfs_trans_handle *trans;
+
+ trans = btrfs_attach_transaction(ctx->fs_info->tree_root);
+ if (IS_ERR(trans)) {
+ if (PTR_ERR(trans) != -ENOENT &&
+ PTR_ERR(trans) != -EROFS)
+ return PTR_ERR(trans);
+ trans = NULL;
+ }
+ ctx->trans = trans;
+ }
+
+ if (ctx->trans) {
+ btrfs_get_tree_mod_seq(ctx->fs_info, &seq_elem);
+ ctx->time_seq = seq_elem.seq;
+ } else {
+ down_read(&ctx->fs_info->commit_root_sem);
+ }
+
+ ret = btrfs_find_all_leafs(ctx);
+ if (ret)
+ goto out;
+ refs = ctx->refs;
+ ctx->refs = NULL;
+
+ ULIST_ITER_INIT(&ref_uiter);
+ while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
+ const u64 leaf_bytenr = ref_node->val;
+ struct ulist_node *root_node;
+ struct ulist_iterator root_uiter;
+ struct extent_inode_elem *inode_list;
+
+ inode_list = (struct extent_inode_elem *)(uintptr_t)ref_node->aux;
+
+ if (ctx->cache_lookup) {
+ const u64 *root_ids;
+ int root_count;
+ bool cached;
+
+ cached = ctx->cache_lookup(leaf_bytenr, ctx->user_ctx,
+ &root_ids, &root_count);
+ if (cached) {
+ for (int i = 0; i < root_count; i++) {
+ ret = iterate_leaf_refs(ctx->fs_info,
+ inode_list,
+ root_ids[i],
+ leaf_bytenr,
+ iterate,
+ user_ctx);
+ if (ret)
+ break;
+ }
+ continue;
+ }
+ }
+
+ if (!ctx->roots) {
+ ctx->roots = ulist_alloc(GFP_NOFS);
+ if (!ctx->roots) {
+ ret = -ENOMEM;
+ break;
+ }
+ }
+
+ ctx->bytenr = leaf_bytenr;
+ ret = btrfs_find_all_roots_safe(ctx);
+ if (ret)
+ break;
+
+ if (ctx->cache_store)
+ ctx->cache_store(leaf_bytenr, ctx->roots, ctx->user_ctx);
+
+ ULIST_ITER_INIT(&root_uiter);
+ while (!ret && (root_node = ulist_next(ctx->roots, &root_uiter))) {
+ btrfs_debug(ctx->fs_info,
+ "root %llu references leaf %llu, data list %#llx",
+ root_node->val, ref_node->val,
+ ref_node->aux);
+ ret = iterate_leaf_refs(ctx->fs_info, inode_list,
+ root_node->val, ctx->bytenr,
+ iterate, user_ctx);
+ }
+ ulist_reinit(ctx->roots);
+ }
+
+ free_leaf_list(refs);
+out:
+ if (ctx->trans) {
+ btrfs_put_tree_mod_seq(ctx->fs_info, &seq_elem);
+ btrfs_end_transaction(ctx->trans);
+ ctx->trans = NULL;
+ } else {
+ up_read(&ctx->fs_info->commit_root_sem);
+ }
+
+ ulist_free(ctx->roots);
+ ctx->roots = NULL;
+
+ if (ret == BTRFS_ITERATE_EXTENT_INODES_STOP)
+ ret = 0;
+
+ return ret;
+}
+
+static int build_ino_list(u64 inum, u64 offset, u64 num_bytes, u64 root, void *ctx)
+{
+ struct btrfs_data_container *inodes = ctx;
+ const size_t c = 3 * sizeof(u64);
+
+ if (inodes->bytes_left >= c) {
+ inodes->bytes_left -= c;
+ inodes->val[inodes->elem_cnt] = inum;
+ inodes->val[inodes->elem_cnt + 1] = offset;
+ inodes->val[inodes->elem_cnt + 2] = root;
+ inodes->elem_cnt += 3;
+ } else {
+ inodes->bytes_missing += c - inodes->bytes_left;
+ inodes->bytes_left = 0;
+ inodes->elem_missed += 3;
+ }
+
+ return 0;
+}
+
+int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
+ struct btrfs_path *path,
+ void *ctx, bool ignore_offset)
+{
+ struct btrfs_backref_walk_ctx walk_ctx = { 0 };
+ int ret;
+ u64 flags = 0;
+ struct btrfs_key found_key;
+ int search_commit_root = path->search_commit_root;
+
+ ret = extent_from_logical(fs_info, logical, path, &found_key, &flags);
+ btrfs_release_path(path);
+ if (ret < 0)
+ return ret;
+ if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
+ return -EINVAL;
+
+ walk_ctx.bytenr = found_key.objectid;
+ if (ignore_offset)
+ walk_ctx.ignore_extent_item_pos = true;
+ else
+ walk_ctx.extent_item_pos = logical - found_key.objectid;
+ walk_ctx.fs_info = fs_info;
+
+ return iterate_extent_inodes(&walk_ctx, search_commit_root,
+ build_ino_list, ctx);
+}
+
+static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
+ struct extent_buffer *eb, struct inode_fs_paths *ipath);
+
+static int iterate_inode_refs(u64 inum, struct inode_fs_paths *ipath)
+{
+ int ret = 0;
+ int slot;
+ u32 cur;
+ u32 len;
+ u32 name_len;
+ u64 parent = 0;
+ int found = 0;
+ struct btrfs_root *fs_root = ipath->fs_root;
+ struct btrfs_path *path = ipath->btrfs_path;
+ struct extent_buffer *eb;
+ struct btrfs_inode_ref *iref;
+ struct btrfs_key found_key;
+
+ while (!ret) {
+ ret = btrfs_find_item(fs_root, path, inum,
+ parent ? parent + 1 : 0, BTRFS_INODE_REF_KEY,
+ &found_key);
+
+ if (ret < 0)
+ break;
+ if (ret) {
+ ret = found ? 0 : -ENOENT;
+ break;
+ }
+ ++found;
+
+ parent = found_key.offset;
+ slot = path->slots[0];
+ eb = btrfs_clone_extent_buffer(path->nodes[0]);
+ if (!eb) {
+ ret = -ENOMEM;
+ break;
+ }
+ btrfs_release_path(path);
+
+ iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
+
+ for (cur = 0; cur < btrfs_item_size(eb, slot); cur += len) {
+ name_len = btrfs_inode_ref_name_len(eb, iref);
+ /* path must be released before calling iterate()! */
+ btrfs_debug(fs_root->fs_info,
+ "following ref at offset %u for inode %llu in tree %llu",
+ cur, found_key.objectid,
+ fs_root->root_key.objectid);
+ ret = inode_to_path(parent, name_len,
+ (unsigned long)(iref + 1), eb, ipath);
+ if (ret)
+ break;
+ len = sizeof(*iref) + name_len;
+ iref = (struct btrfs_inode_ref *)((char *)iref + len);
+ }
+ free_extent_buffer(eb);
+ }
+
+ btrfs_release_path(path);
+
+ return ret;
+}
+
+static int iterate_inode_extrefs(u64 inum, struct inode_fs_paths *ipath)
+{
+ int ret;
+ int slot;
+ u64 offset = 0;
+ u64 parent;
+ int found = 0;
+ struct btrfs_root *fs_root = ipath->fs_root;
+ struct btrfs_path *path = ipath->btrfs_path;
+ struct extent_buffer *eb;
+ struct btrfs_inode_extref *extref;
+ u32 item_size;
+ u32 cur_offset;
+ unsigned long ptr;
+
+ while (1) {
+ ret = btrfs_find_one_extref(fs_root, inum, offset, path, &extref,
+ &offset);
+ if (ret < 0)
+ break;
+ if (ret) {
+ ret = found ? 0 : -ENOENT;
+ break;
+ }
+ ++found;
+
+ slot = path->slots[0];
+ eb = btrfs_clone_extent_buffer(path->nodes[0]);
+ if (!eb) {
+ ret = -ENOMEM;
+ break;
+ }
+ btrfs_release_path(path);
+
+ item_size = btrfs_item_size(eb, slot);
+ ptr = btrfs_item_ptr_offset(eb, slot);
+ cur_offset = 0;
+
+ while (cur_offset < item_size) {
+ u32 name_len;
+
+ extref = (struct btrfs_inode_extref *)(ptr + cur_offset);
+ parent = btrfs_inode_extref_parent(eb, extref);
+ name_len = btrfs_inode_extref_name_len(eb, extref);
+ ret = inode_to_path(parent, name_len,
+ (unsigned long)&extref->name, eb, ipath);
+ if (ret)
+ break;
+
+ cur_offset += btrfs_inode_extref_name_len(eb, extref);
+ cur_offset += sizeof(*extref);
+ }
+ free_extent_buffer(eb);
+
+ offset++;
+ }
+
+ btrfs_release_path(path);
+
+ return ret;
+}
+
+/*
+ * returns 0 if the path could be dumped (probably truncated)
+ * returns <0 in case of an error
+ */
+static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
+ struct extent_buffer *eb, struct inode_fs_paths *ipath)
+{
+ char *fspath;
+ char *fspath_min;
+ int i = ipath->fspath->elem_cnt;
+ const int s_ptr = sizeof(char *);
+ u32 bytes_left;
+
+ bytes_left = ipath->fspath->bytes_left > s_ptr ?
+ ipath->fspath->bytes_left - s_ptr : 0;
+
+ fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
+ fspath = btrfs_ref_to_path(ipath->fs_root, ipath->btrfs_path, name_len,
+ name_off, eb, inum, fspath_min, bytes_left);
+ if (IS_ERR(fspath))
+ return PTR_ERR(fspath);
+
+ if (fspath > fspath_min) {
+ ipath->fspath->val[i] = (u64)(unsigned long)fspath;
+ ++ipath->fspath->elem_cnt;
+ ipath->fspath->bytes_left = fspath - fspath_min;
+ } else {
+ ++ipath->fspath->elem_missed;
+ ipath->fspath->bytes_missing += fspath_min - fspath;
+ ipath->fspath->bytes_left = 0;
+ }
+
+ return 0;
+}
+
+/*
+ * this dumps all file system paths to the inode into the ipath struct, provided
+ * is has been created large enough. each path is zero-terminated and accessed
+ * from ipath->fspath->val[i].
+ * when it returns, there are ipath->fspath->elem_cnt number of paths available
+ * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
+ * number of missed paths is recorded in ipath->fspath->elem_missed, otherwise,
+ * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
+ * have been needed to return all paths.
+ */
+int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
+{
+ int ret;
+ int found_refs = 0;
+
+ ret = iterate_inode_refs(inum, ipath);
+ if (!ret)
+ ++found_refs;
+ else if (ret != -ENOENT)
+ return ret;
+
+ ret = iterate_inode_extrefs(inum, ipath);
+ if (ret == -ENOENT && found_refs)
+ return 0;
+
+ return ret;
+}
+
+struct btrfs_data_container *init_data_container(u32 total_bytes)
+{
+ struct btrfs_data_container *data;
+ size_t alloc_bytes;
+
+ alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
+ data = kvmalloc(alloc_bytes, GFP_KERNEL);
+ if (!data)
+ return ERR_PTR(-ENOMEM);
+
+ if (total_bytes >= sizeof(*data)) {
+ data->bytes_left = total_bytes - sizeof(*data);
+ data->bytes_missing = 0;
+ } else {
+ data->bytes_missing = sizeof(*data) - total_bytes;
+ data->bytes_left = 0;
+ }
+
+ data->elem_cnt = 0;
+ data->elem_missed = 0;
+
+ return data;
+}
+
+/*
+ * allocates space to return multiple file system paths for an inode.
+ * total_bytes to allocate are passed, note that space usable for actual path
+ * information will be total_bytes - sizeof(struct inode_fs_paths).
+ * the returned pointer must be freed with free_ipath() in the end.
+ */
+struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
+ struct btrfs_path *path)
+{
+ struct inode_fs_paths *ifp;
+ struct btrfs_data_container *fspath;
+
+ fspath = init_data_container(total_bytes);
+ if (IS_ERR(fspath))
+ return ERR_CAST(fspath);
+
+ ifp = kmalloc(sizeof(*ifp), GFP_KERNEL);
+ if (!ifp) {
+ kvfree(fspath);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ ifp->btrfs_path = path;
+ ifp->fspath = fspath;
+ ifp->fs_root = fs_root;
+
+ return ifp;
+}
+
+void free_ipath(struct inode_fs_paths *ipath)
+{
+ if (!ipath)
+ return;
+ kvfree(ipath->fspath);
+ kfree(ipath);
+}
+
+struct btrfs_backref_iter *btrfs_backref_iter_alloc(struct btrfs_fs_info *fs_info)
+{
+ struct btrfs_backref_iter *ret;
+
+ ret = kzalloc(sizeof(*ret), GFP_NOFS);
+ if (!ret)
+ return NULL;
+
+ ret->path = btrfs_alloc_path();
+ if (!ret->path) {
+ kfree(ret);
+ return NULL;
+ }
+
+ /* Current backref iterator only supports iteration in commit root */
+ ret->path->search_commit_root = 1;
+ ret->path->skip_locking = 1;
+ ret->fs_info = fs_info;
+
+ return ret;
+}
+
+int btrfs_backref_iter_start(struct btrfs_backref_iter *iter, u64 bytenr)
+{
+ struct btrfs_fs_info *fs_info = iter->fs_info;
+ struct btrfs_root *extent_root = btrfs_extent_root(fs_info, bytenr);
+ struct btrfs_path *path = iter->path;
+ struct btrfs_extent_item *ei;
+ struct btrfs_key key;
+ int ret;
+
+ key.objectid = bytenr;
+ key.type = BTRFS_METADATA_ITEM_KEY;
+ key.offset = (u64)-1;
+ iter->bytenr = bytenr;
+
+ ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0);
+ if (ret < 0)
+ return ret;
+ if (ret == 0) {
+ ret = -EUCLEAN;
+ goto release;
+ }
+ if (path->slots[0] == 0) {
+ WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG));
+ ret = -EUCLEAN;
+ goto release;
+ }
+ path->slots[0]--;
+
+ btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
+ if ((key.type != BTRFS_EXTENT_ITEM_KEY &&
+ key.type != BTRFS_METADATA_ITEM_KEY) || key.objectid != bytenr) {
+ ret = -ENOENT;
+ goto release;
+ }
+ memcpy(&iter->cur_key, &key, sizeof(key));
+ iter->item_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
+ path->slots[0]);
+ iter->end_ptr = (u32)(iter->item_ptr +
+ btrfs_item_size(path->nodes[0], path->slots[0]));
+ ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
+ struct btrfs_extent_item);
+
+ /*
+ * Only support iteration on tree backref yet.
+ *
+ * This is an extra precaution for non skinny-metadata, where
+ * EXTENT_ITEM is also used for tree blocks, that we can only use
+ * extent flags to determine if it's a tree block.
+ */
+ if (btrfs_extent_flags(path->nodes[0], ei) & BTRFS_EXTENT_FLAG_DATA) {
+ ret = -ENOTSUPP;
+ goto release;
+ }
+ iter->cur_ptr = (u32)(iter->item_ptr + sizeof(*ei));
+
+ /* If there is no inline backref, go search for keyed backref */
+ if (iter->cur_ptr >= iter->end_ptr) {
+ ret = btrfs_next_item(extent_root, path);
+
+ /* No inline nor keyed ref */
+ if (ret > 0) {
+ ret = -ENOENT;
+ goto release;
+ }
+ if (ret < 0)
+ goto release;
+
+ btrfs_item_key_to_cpu(path->nodes[0], &iter->cur_key,
+ path->slots[0]);
+ if (iter->cur_key.objectid != bytenr ||
+ (iter->cur_key.type != BTRFS_SHARED_BLOCK_REF_KEY &&
+ iter->cur_key.type != BTRFS_TREE_BLOCK_REF_KEY)) {
+ ret = -ENOENT;
+ goto release;
+ }
+ iter->cur_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
+ path->slots[0]);
+ iter->item_ptr = iter->cur_ptr;
+ iter->end_ptr = (u32)(iter->item_ptr + btrfs_item_size(
+ path->nodes[0], path->slots[0]));
+ }
+
+ return 0;
+release:
+ btrfs_backref_iter_release(iter);
+ return ret;
+}
+
+/*
+ * Go to the next backref item of current bytenr, can be either inlined or
+ * keyed.
+ *
+ * Caller needs to check whether it's inline ref or not by iter->cur_key.
+ *
+ * Return 0 if we get next backref without problem.
+ * Return >0 if there is no extra backref for this bytenr.
+ * Return <0 if there is something wrong happened.
+ */
+int btrfs_backref_iter_next(struct btrfs_backref_iter *iter)
+{
+ struct extent_buffer *eb = btrfs_backref_get_eb(iter);
+ struct btrfs_root *extent_root;
+ struct btrfs_path *path = iter->path;
+ struct btrfs_extent_inline_ref *iref;
+ int ret;
+ u32 size;
+
+ if (btrfs_backref_iter_is_inline_ref(iter)) {
+ /* We're still inside the inline refs */
+ ASSERT(iter->cur_ptr < iter->end_ptr);
+
+ if (btrfs_backref_has_tree_block_info(iter)) {
+ /* First tree block info */
+ size = sizeof(struct btrfs_tree_block_info);
+ } else {
+ /* Use inline ref type to determine the size */
+ int type;
+
+ iref = (struct btrfs_extent_inline_ref *)
+ ((unsigned long)iter->cur_ptr);
+ type = btrfs_extent_inline_ref_type(eb, iref);
+
+ size = btrfs_extent_inline_ref_size(type);
+ }
+ iter->cur_ptr += size;
+ if (iter->cur_ptr < iter->end_ptr)
+ return 0;
+
+ /* All inline items iterated, fall through */
+ }
+
+ /* We're at keyed items, there is no inline item, go to the next one */
+ extent_root = btrfs_extent_root(iter->fs_info, iter->bytenr);
+ ret = btrfs_next_item(extent_root, iter->path);
+ if (ret)
+ return ret;
+
+ btrfs_item_key_to_cpu(path->nodes[0], &iter->cur_key, path->slots[0]);
+ if (iter->cur_key.objectid != iter->bytenr ||
+ (iter->cur_key.type != BTRFS_TREE_BLOCK_REF_KEY &&
+ iter->cur_key.type != BTRFS_SHARED_BLOCK_REF_KEY))
+ return 1;
+ iter->item_ptr = (u32)btrfs_item_ptr_offset(path->nodes[0],
+ path->slots[0]);
+ iter->cur_ptr = iter->item_ptr;
+ iter->end_ptr = iter->item_ptr + (u32)btrfs_item_size(path->nodes[0],
+ path->slots[0]);
+ return 0;
+}
+
+void btrfs_backref_init_cache(struct btrfs_fs_info *fs_info,
+ struct btrfs_backref_cache *cache, int is_reloc)
+{
+ int i;
+
+ cache->rb_root = RB_ROOT;
+ for (i = 0; i < BTRFS_MAX_LEVEL; i++)
+ INIT_LIST_HEAD(&cache->pending[i]);
+ INIT_LIST_HEAD(&cache->changed);
+ INIT_LIST_HEAD(&cache->detached);
+ INIT_LIST_HEAD(&cache->leaves);
+ INIT_LIST_HEAD(&cache->pending_edge);
+ INIT_LIST_HEAD(&cache->useless_node);
+ cache->fs_info = fs_info;
+ cache->is_reloc = is_reloc;
+}
+
+struct btrfs_backref_node *btrfs_backref_alloc_node(
+ struct btrfs_backref_cache *cache, u64 bytenr, int level)
+{
+ struct btrfs_backref_node *node;
+
+ ASSERT(level >= 0 && level < BTRFS_MAX_LEVEL);
+ node = kzalloc(sizeof(*node), GFP_NOFS);
+ if (!node)
+ return node;
+
+ INIT_LIST_HEAD(&node->list);
+ INIT_LIST_HEAD(&node->upper);
+ INIT_LIST_HEAD(&node->lower);
+ RB_CLEAR_NODE(&node->rb_node);
+ cache->nr_nodes++;
+ node->level = level;
+ node->bytenr = bytenr;
+
+ return node;
+}
+
+struct btrfs_backref_edge *btrfs_backref_alloc_edge(
+ struct btrfs_backref_cache *cache)
+{
+ struct btrfs_backref_edge *edge;
+
+ edge = kzalloc(sizeof(*edge), GFP_NOFS);
+ if (edge)
+ cache->nr_edges++;
+ return edge;
+}
+
+/*
+ * Drop the backref node from cache, also cleaning up all its
+ * upper edges and any uncached nodes in the path.
+ *
+ * This cleanup happens bottom up, thus the node should either
+ * be the lowest node in the cache or a detached node.
+ */
+void btrfs_backref_cleanup_node(struct btrfs_backref_cache *cache,
+ struct btrfs_backref_node *node)
+{
+ struct btrfs_backref_node *upper;
+ struct btrfs_backref_edge *edge;
+
+ if (!node)
+ return;
+
+ BUG_ON(!node->lowest && !node->detached);
+ while (!list_empty(&node->upper)) {
+ edge = list_entry(node->upper.next, struct btrfs_backref_edge,
+ list[LOWER]);
+ upper = edge->node[UPPER];
+ list_del(&edge->list[LOWER]);
+ list_del(&edge->list[UPPER]);
+ btrfs_backref_free_edge(cache, edge);
+
+ /*
+ * Add the node to leaf node list if no other child block
+ * cached.
+ */
+ if (list_empty(&upper->lower)) {
+ list_add_tail(&upper->lower, &cache->leaves);
+ upper->lowest = 1;
+ }
+ }
+
+ btrfs_backref_drop_node(cache, node);
+}
+
+/*
+ * Release all nodes/edges from current cache
+ */
+void btrfs_backref_release_cache(struct btrfs_backref_cache *cache)
+{
+ struct btrfs_backref_node *node;
+ int i;
+
+ while (!list_empty(&cache->detached)) {
+ node = list_entry(cache->detached.next,
+ struct btrfs_backref_node, list);
+ btrfs_backref_cleanup_node(cache, node);
+ }
+
+ while (!list_empty(&cache->leaves)) {
+ node = list_entry(cache->leaves.next,
+ struct btrfs_backref_node, lower);
+ btrfs_backref_cleanup_node(cache, node);
+ }
+
+ cache->last_trans = 0;
+
+ for (i = 0; i < BTRFS_MAX_LEVEL; i++)
+ ASSERT(list_empty(&cache->pending[i]));
+ ASSERT(list_empty(&cache->pending_edge));
+ ASSERT(list_empty(&cache->useless_node));
+ ASSERT(list_empty(&cache->changed));
+ ASSERT(list_empty(&cache->detached));
+ ASSERT(RB_EMPTY_ROOT(&cache->rb_root));
+ ASSERT(!cache->nr_nodes);
+ ASSERT(!cache->nr_edges);
+}
+
+/*
+ * Handle direct tree backref
+ *
+ * Direct tree backref means, the backref item shows its parent bytenr
+ * directly. This is for SHARED_BLOCK_REF backref (keyed or inlined).
+ *
+ * @ref_key: The converted backref key.
+ * For keyed backref, it's the item key.
+ * For inlined backref, objectid is the bytenr,
+ * type is btrfs_inline_ref_type, offset is
+ * btrfs_inline_ref_offset.
+ */
+static int handle_direct_tree_backref(struct btrfs_backref_cache *cache,
+ struct btrfs_key *ref_key,
+ struct btrfs_backref_node *cur)
+{
+ struct btrfs_backref_edge *edge;
+ struct btrfs_backref_node *upper;
+ struct rb_node *rb_node;
+
+ ASSERT(ref_key->type == BTRFS_SHARED_BLOCK_REF_KEY);
+
+ /* Only reloc root uses backref pointing to itself */
+ if (ref_key->objectid == ref_key->offset) {
+ struct btrfs_root *root;
+
+ cur->is_reloc_root = 1;
+ /* Only reloc backref cache cares about a specific root */
+ if (cache->is_reloc) {
+ root = find_reloc_root(cache->fs_info, cur->bytenr);
+ if (!root)
+ return -ENOENT;
+ cur->root = root;
+ } else {
+ /*
+ * For generic purpose backref cache, reloc root node
+ * is useless.
+ */
+ list_add(&cur->list, &cache->useless_node);
+ }
+ return 0;
+ }
+
+ edge = btrfs_backref_alloc_edge(cache);
+ if (!edge)
+ return -ENOMEM;
+
+ rb_node = rb_simple_search(&cache->rb_root, ref_key->offset);
+ if (!rb_node) {
+ /* Parent node not yet cached */
+ upper = btrfs_backref_alloc_node(cache, ref_key->offset,
+ cur->level + 1);
+ if (!upper) {
+ btrfs_backref_free_edge(cache, edge);
+ return -ENOMEM;
+ }
+
+ /*
+ * Backrefs for the upper level block isn't cached, add the
+ * block to pending list
+ */
+ list_add_tail(&edge->list[UPPER], &cache->pending_edge);
+ } else {
+ /* Parent node already cached */
+ upper = rb_entry(rb_node, struct btrfs_backref_node, rb_node);
+ ASSERT(upper->checked);
+ INIT_LIST_HEAD(&edge->list[UPPER]);
+ }
+ btrfs_backref_link_edge(edge, cur, upper, LINK_LOWER);
+ return 0;
+}
+
+/*
+ * Handle indirect tree backref
+ *
+ * Indirect tree backref means, we only know which tree the node belongs to.
+ * We still need to do a tree search to find out the parents. This is for
+ * TREE_BLOCK_REF backref (keyed or inlined).
+ *
+ * @trans: Transaction handle.
+ * @ref_key: The same as @ref_key in handle_direct_tree_backref()
+ * @tree_key: The first key of this tree block.
+ * @path: A clean (released) path, to avoid allocating path every time
+ * the function get called.
+ */
+static int handle_indirect_tree_backref(struct btrfs_trans_handle *trans,
+ struct btrfs_backref_cache *cache,
+ struct btrfs_path *path,
+ struct btrfs_key *ref_key,
+ struct btrfs_key *tree_key,
+ struct btrfs_backref_node *cur)
+{
+ struct btrfs_fs_info *fs_info = cache->fs_info;
+ struct btrfs_backref_node *upper;
+ struct btrfs_backref_node *lower;
+ struct btrfs_backref_edge *edge;
+ struct extent_buffer *eb;
+ struct btrfs_root *root;
+ struct rb_node *rb_node;
+ int level;
+ bool need_check = true;
+ int ret;
+
+ root = btrfs_get_fs_root(fs_info, ref_key->offset, false);
+ if (IS_ERR(root))
+ return PTR_ERR(root);
+ if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
+ cur->cowonly = 1;
+
+ if (btrfs_root_level(&root->root_item) == cur->level) {
+ /* Tree root */
+ ASSERT(btrfs_root_bytenr(&root->root_item) == cur->bytenr);
+ /*
+ * For reloc backref cache, we may ignore reloc root. But for
+ * general purpose backref cache, we can't rely on
+ * btrfs_should_ignore_reloc_root() as it may conflict with
+ * current running relocation and lead to missing root.
+ *
+ * For general purpose backref cache, reloc root detection is
+ * completely relying on direct backref (key->offset is parent
+ * bytenr), thus only do such check for reloc cache.
+ */
+ if (btrfs_should_ignore_reloc_root(root) && cache->is_reloc) {
+ btrfs_put_root(root);
+ list_add(&cur->list, &cache->useless_node);
+ } else {
+ cur->root = root;
+ }
+ return 0;
+ }
+
+ level = cur->level + 1;
+
+ /* Search the tree to find parent blocks referring to the block */
+ path->search_commit_root = 1;
+ path->skip_locking = 1;
+ path->lowest_level = level;
+ ret = btrfs_search_slot(NULL, root, tree_key, path, 0, 0);
+ path->lowest_level = 0;
+ if (ret < 0) {
+ btrfs_put_root(root);
+ return ret;
+ }
+ if (ret > 0 && path->slots[level] > 0)
+ path->slots[level]--;
+
+ eb = path->nodes[level];
+ if (btrfs_node_blockptr(eb, path->slots[level]) != cur->bytenr) {
+ btrfs_err(fs_info,
+"couldn't find block (%llu) (level %d) in tree (%llu) with key (%llu %u %llu)",
+ cur->bytenr, level - 1, root->root_key.objectid,
+ tree_key->objectid, tree_key->type, tree_key->offset);
+ btrfs_put_root(root);
+ ret = -ENOENT;
+ goto out;
+ }
+ lower = cur;
+
+ /* Add all nodes and edges in the path */
+ for (; level < BTRFS_MAX_LEVEL; level++) {
+ if (!path->nodes[level]) {
+ ASSERT(btrfs_root_bytenr(&root->root_item) ==
+ lower->bytenr);
+ /* Same as previous should_ignore_reloc_root() call */
+ if (btrfs_should_ignore_reloc_root(root) &&
+ cache->is_reloc) {
+ btrfs_put_root(root);
+ list_add(&lower->list, &cache->useless_node);
+ } else {
+ lower->root = root;
+ }
+ break;
+ }
+
+ edge = btrfs_backref_alloc_edge(cache);
+ if (!edge) {
+ btrfs_put_root(root);
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ eb = path->nodes[level];
+ rb_node = rb_simple_search(&cache->rb_root, eb->start);
+ if (!rb_node) {
+ upper = btrfs_backref_alloc_node(cache, eb->start,
+ lower->level + 1);
+ if (!upper) {
+ btrfs_put_root(root);
+ btrfs_backref_free_edge(cache, edge);
+ ret = -ENOMEM;
+ goto out;
+ }
+ upper->owner = btrfs_header_owner(eb);
+ if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
+ upper->cowonly = 1;
+
+ /*
+ * If we know the block isn't shared we can avoid
+ * checking its backrefs.
+ */
+ if (btrfs_block_can_be_shared(trans, root, eb))
+ upper->checked = 0;
+ else
+ upper->checked = 1;
+
+ /*
+ * Add the block to pending list if we need to check its
+ * backrefs, we only do this once while walking up a
+ * tree as we will catch anything else later on.
+ */
+ if (!upper->checked && need_check) {
+ need_check = false;
+ list_add_tail(&edge->list[UPPER],
+ &cache->pending_edge);
+ } else {
+ if (upper->checked)
+ need_check = true;
+ INIT_LIST_HEAD(&edge->list[UPPER]);
+ }
+ } else {
+ upper = rb_entry(rb_node, struct btrfs_backref_node,
+ rb_node);
+ ASSERT(upper->checked);
+ INIT_LIST_HEAD(&edge->list[UPPER]);
+ if (!upper->owner)
+ upper->owner = btrfs_header_owner(eb);
+ }
+ btrfs_backref_link_edge(edge, lower, upper, LINK_LOWER);
+
+ if (rb_node) {
+ btrfs_put_root(root);
+ break;
+ }
+ lower = upper;
+ upper = NULL;
+ }
+out:
+ btrfs_release_path(path);
+ return ret;
+}
+
+/*
+ * Add backref node @cur into @cache.
+ *
+ * NOTE: Even if the function returned 0, @cur is not yet cached as its upper
+ * links aren't yet bi-directional. Needs to finish such links.
+ * Use btrfs_backref_finish_upper_links() to finish such linkage.
+ *
+ * @trans: Transaction handle.
+ * @path: Released path for indirect tree backref lookup
+ * @iter: Released backref iter for extent tree search
+ * @node_key: The first key of the tree block
+ */
+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)
+{
+ struct btrfs_backref_edge *edge;
+ struct btrfs_backref_node *exist;
+ int ret;
+
+ ret = btrfs_backref_iter_start(iter, cur->bytenr);
+ if (ret < 0)
+ return ret;
+ /*
+ * We skip the first btrfs_tree_block_info, as we don't use the key
+ * stored in it, but fetch it from the tree block
+ */
+ if (btrfs_backref_has_tree_block_info(iter)) {
+ ret = btrfs_backref_iter_next(iter);
+ if (ret < 0)
+ goto out;
+ /* No extra backref? This means the tree block is corrupted */
+ if (ret > 0) {
+ ret = -EUCLEAN;
+ goto out;
+ }
+ }
+ WARN_ON(cur->checked);
+ if (!list_empty(&cur->upper)) {
+ /*
+ * The backref was added previously when processing backref of
+ * type BTRFS_TREE_BLOCK_REF_KEY
+ */
+ ASSERT(list_is_singular(&cur->upper));
+ edge = list_entry(cur->upper.next, struct btrfs_backref_edge,
+ list[LOWER]);
+ ASSERT(list_empty(&edge->list[UPPER]));
+ exist = edge->node[UPPER];
+ /*
+ * Add the upper level block to pending list if we need check
+ * its backrefs
+ */
+ if (!exist->checked)
+ list_add_tail(&edge->list[UPPER], &cache->pending_edge);
+ } else {
+ exist = NULL;
+ }
+
+ for (; ret == 0; ret = btrfs_backref_iter_next(iter)) {
+ struct extent_buffer *eb;
+ struct btrfs_key key;
+ int type;
+
+ cond_resched();
+ eb = btrfs_backref_get_eb(iter);
+
+ key.objectid = iter->bytenr;
+ if (btrfs_backref_iter_is_inline_ref(iter)) {
+ struct btrfs_extent_inline_ref *iref;
+
+ /* Update key for inline backref */
+ iref = (struct btrfs_extent_inline_ref *)
+ ((unsigned long)iter->cur_ptr);
+ type = btrfs_get_extent_inline_ref_type(eb, iref,
+ BTRFS_REF_TYPE_BLOCK);
+ if (type == BTRFS_REF_TYPE_INVALID) {
+ ret = -EUCLEAN;
+ goto out;
+ }
+ key.type = type;
+ key.offset = btrfs_extent_inline_ref_offset(eb, iref);
+ } else {
+ key.type = iter->cur_key.type;
+ key.offset = iter->cur_key.offset;
+ }
+
+ /*
+ * Parent node found and matches current inline ref, no need to
+ * rebuild this node for this inline ref
+ */
+ if (exist &&
+ ((key.type == BTRFS_TREE_BLOCK_REF_KEY &&
+ exist->owner == key.offset) ||
+ (key.type == BTRFS_SHARED_BLOCK_REF_KEY &&
+ exist->bytenr == key.offset))) {
+ exist = NULL;
+ continue;
+ }
+
+ /* SHARED_BLOCK_REF means key.offset is the parent bytenr */
+ if (key.type == BTRFS_SHARED_BLOCK_REF_KEY) {
+ ret = handle_direct_tree_backref(cache, &key, cur);
+ if (ret < 0)
+ goto out;
+ } else if (key.type == BTRFS_TREE_BLOCK_REF_KEY) {
+ /*
+ * key.type == BTRFS_TREE_BLOCK_REF_KEY, inline ref
+ * offset means the root objectid. We need to search
+ * the tree to get its parent bytenr.
+ */
+ ret = handle_indirect_tree_backref(trans, cache, path,
+ &key, node_key, cur);
+ if (ret < 0)
+ goto out;
+ }
+ /*
+ * Unrecognized tree backref items (if it can pass tree-checker)
+ * would be ignored.
+ */
+ }
+ ret = 0;
+ cur->checked = 1;
+ WARN_ON(exist);
+out:
+ btrfs_backref_iter_release(iter);
+ return ret;
+}
+
+/*
+ * Finish the upwards linkage created by btrfs_backref_add_tree_node()
+ */
+int btrfs_backref_finish_upper_links(struct btrfs_backref_cache *cache,
+ struct btrfs_backref_node *start)
+{
+ struct list_head *useless_node = &cache->useless_node;
+ struct btrfs_backref_edge *edge;
+ struct rb_node *rb_node;
+ LIST_HEAD(pending_edge);
+
+ ASSERT(start->checked);
+
+ /* Insert this node to cache if it's not COW-only */
+ if (!start->cowonly) {
+ rb_node = rb_simple_insert(&cache->rb_root, start->bytenr,
+ &start->rb_node);
+ if (rb_node)
+ btrfs_backref_panic(cache->fs_info, start->bytenr,
+ -EEXIST);
+ list_add_tail(&start->lower, &cache->leaves);
+ }
+
+ /*
+ * Use breadth first search to iterate all related edges.
+ *
+ * The starting points are all the edges of this node
+ */
+ list_for_each_entry(edge, &start->upper, list[LOWER])
+ list_add_tail(&edge->list[UPPER], &pending_edge);
+
+ while (!list_empty(&pending_edge)) {
+ struct btrfs_backref_node *upper;
+ struct btrfs_backref_node *lower;
+
+ edge = list_first_entry(&pending_edge,
+ struct btrfs_backref_edge, list[UPPER]);
+ list_del_init(&edge->list[UPPER]);
+ upper = edge->node[UPPER];
+ lower = edge->node[LOWER];
+
+ /* Parent is detached, no need to keep any edges */
+ if (upper->detached) {
+ list_del(&edge->list[LOWER]);
+ btrfs_backref_free_edge(cache, edge);
+
+ /* Lower node is orphan, queue for cleanup */
+ if (list_empty(&lower->upper))
+ list_add(&lower->list, useless_node);
+ continue;
+ }
+
+ /*
+ * All new nodes added in current build_backref_tree() haven't
+ * been linked to the cache rb tree.
+ * So if we have upper->rb_node populated, this means a cache
+ * hit. We only need to link the edge, as @upper and all its
+ * parents have already been linked.
+ */
+ if (!RB_EMPTY_NODE(&upper->rb_node)) {
+ if (upper->lowest) {
+ list_del_init(&upper->lower);
+ upper->lowest = 0;
+ }
+
+ list_add_tail(&edge->list[UPPER], &upper->lower);
+ continue;
+ }
+
+ /* Sanity check, we shouldn't have any unchecked nodes */
+ if (!upper->checked) {
+ ASSERT(0);
+ return -EUCLEAN;
+ }
+
+ /* Sanity check, COW-only node has non-COW-only parent */
+ if (start->cowonly != upper->cowonly) {
+ ASSERT(0);
+ return -EUCLEAN;
+ }
+
+ /* Only cache non-COW-only (subvolume trees) tree blocks */
+ if (!upper->cowonly) {
+ rb_node = rb_simple_insert(&cache->rb_root, upper->bytenr,
+ &upper->rb_node);
+ if (rb_node) {
+ btrfs_backref_panic(cache->fs_info,
+ upper->bytenr, -EEXIST);
+ return -EUCLEAN;
+ }
+ }
+
+ list_add_tail(&edge->list[UPPER], &upper->lower);
+
+ /*
+ * Also queue all the parent edges of this uncached node
+ * to finish the upper linkage
+ */
+ list_for_each_entry(edge, &upper->upper, list[LOWER])
+ list_add_tail(&edge->list[UPPER], &pending_edge);
+ }
+ return 0;
+}
+
+void btrfs_backref_error_cleanup(struct btrfs_backref_cache *cache,
+ struct btrfs_backref_node *node)
+{
+ struct btrfs_backref_node *lower;
+ struct btrfs_backref_node *upper;
+ struct btrfs_backref_edge *edge;
+
+ while (!list_empty(&cache->useless_node)) {
+ lower = list_first_entry(&cache->useless_node,
+ struct btrfs_backref_node, list);
+ list_del_init(&lower->list);
+ }
+ while (!list_empty(&cache->pending_edge)) {
+ edge = list_first_entry(&cache->pending_edge,
+ struct btrfs_backref_edge, list[UPPER]);
+ list_del(&edge->list[UPPER]);
+ list_del(&edge->list[LOWER]);
+ lower = edge->node[LOWER];
+ upper = edge->node[UPPER];
+ btrfs_backref_free_edge(cache, edge);
+
+ /*
+ * Lower is no longer linked to any upper backref nodes and
+ * isn't in the cache, we can free it ourselves.
+ */
+ if (list_empty(&lower->upper) &&
+ RB_EMPTY_NODE(&lower->rb_node))
+ list_add(&lower->list, &cache->useless_node);
+
+ if (!RB_EMPTY_NODE(&upper->rb_node))
+ continue;
+
+ /* Add this guy's upper edges to the list to process */
+ list_for_each_entry(edge, &upper->upper, list[LOWER])
+ list_add_tail(&edge->list[UPPER],
+ &cache->pending_edge);
+ if (list_empty(&upper->upper))
+ list_add(&upper->list, &cache->useless_node);
+ }
+
+ while (!list_empty(&cache->useless_node)) {
+ lower = list_first_entry(&cache->useless_node,
+ struct btrfs_backref_node, list);
+ list_del_init(&lower->list);
+ if (lower == node)
+ node = NULL;
+ btrfs_backref_drop_node(cache, lower);
+ }
+
+ btrfs_backref_cleanup_node(cache, node);
+ ASSERT(list_empty(&cache->useless_node) &&
+ list_empty(&cache->pending_edge));
+}