for (; eie; eie = eie_next) {
eie_next = eie->next;
kfree(eie);
}
}
staticint find_extent_in_eb(struct btrfs_backref_walk_ctx *ctx, conststruct 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;
}
/* * 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;
};
/* * 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.
*/ staticint prelim_ref_compare(conststruct prelim_ref *ref1, conststruct 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;
/* * prelim_ref_compare() expects the first parameter as the existing one, * different from the rb_find_add_cached() order.
*/ return prelim_ref_compare(ref_exist, ref_new);
}
staticvoid update_share_count(struct share_check *sc, int oldcount, int newcount, conststruct prelim_ref *newref)
{ if ((!sc) || (oldcount == 0 && newcount < 1)) return;
/* * Release the entire tree. We don't care about internal consistency so * just free everything and then reset the tree root.
*/ staticvoid prelim_release(struct preftree *preftree)
{ struct prelim_ref *ref, *next_ref;
/* * 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.
*/ staticint add_prelim_ref(conststruct btrfs_fs_info *fs_info, struct preftree *preftree, u64 root_id, conststruct 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;
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);
}
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); elseif (ret > 0)
ret = 0;
return ret;
}
/* * resolve an indirect backref in the form (root_id, key, level) * to a logical address
*/ staticint 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;
}
/* * 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];
}
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.
*/ staticint resolve_indirect_refs(struct btrfs_backref_walk_ctx *ctx, struct btrfs_path *path, struct preftrees *preftrees, struct share_check *sc)
{ 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; int ret2;
ref = rb_entry(rnode, struct prelim_ref, rbnode); if (WARN(ref->parent, "BUG: direct ref found in indirect tree")) {
ret = -EINVAL; goto out;
}
if (ref->count == 0) {
free_pref(ref); continue;
}
if (sc && ref->root_id != btrfs_root_id(sc->root)) {
free_pref(ref);
ret = BACKREF_FOUND_SHARED; goto out;
}
ret2 = resolve_indirect_ref(ctx, path, preftrees, ref, parents); /* * we can only tolerate ENOENT,otherwise,we should catch error * and return directly.
*/ if (ret2 == -ENOENT) {
prelim_ref_insert(ctx->fs_info, &preftrees->direct, ref,
NULL); continue;
} elseif (ret2) {
free_pref(ref);
ret = ret2; 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;
/* * 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;
}
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
*/ staticint add_delayed_refs(conststruct 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_key *key_ptr = NULL; /* The owner of a tree block ref is the level. */ int level = btrfs_delayed_ref_owner(node);
ret = add_indirect_ref(fs_info, preftrees, node->ref_root,
key_ptr, level + 1, node->bytenr,
count, sc, GFP_ATOMIC); break;
} case BTRFS_SHARED_BLOCK_REF_KEY: { /* * SHARED DIRECT METADATA backref * * The owner of a tree block ref is the level.
*/ int level = btrfs_delayed_ref_owner(node);
ret = add_direct_ref(fs_info, preftrees, level + 1,
node->parent, node->bytenr, count,
sc, GFP_ATOMIC); break;
} case BTRFS_EXTENT_DATA_REF_KEY: { /* NORMAL INDIRECT DATA backref */
key.objectid = btrfs_delayed_ref_owner(node);
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = btrfs_delayed_ref_offset(node);
/* * 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, node->ref_root,
&key, 0, node->bytenr, count, sc,
GFP_ATOMIC); break;
} case BTRFS_SHARED_DATA_REF_KEY: { /* SHARED DIRECT FULL backref */
ret = add_direct_ref(fs_info, preftrees, 0, node->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.
*/ staticint 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; unsignedlong ptr; unsignedlong end; struct btrfs_extent_item *ei;
u64 flags;
u64 item_size;
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.
*/ staticbool lookup_backref_shared_cache(struct btrfs_backref_share_check_ctx *ctx, struct btrfs_root *root,
u64 bytenr, int level, bool *is_shared)
{ conststruct 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) returnfalse;
if (WARN_ON_ONCE(level >= BTRFS_MAX_LEVEL)) returnfalse;
/* * 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) returnfalse;
/* * 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)) returnfalse;
/* * 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)) returnfalse;
*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;
}
}
returntrue;
}
/* * 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.
*/ staticvoid store_backref_shared_cache(struct btrfs_backref_share_check_ctx *ctx, struct btrfs_root *root,
u64 bytenr, int level, bool is_shared)
{ conststruct 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);
/* * 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
*/ staticint 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);
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) { /* * Key with offset -1 found, there would have to exist an extent * item with such offset, but this is out of the valid range.
*/
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(ctx->fs_info, 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;
/* * 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();
}
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.
*/ staticint btrfs_find_all_roots_safe(struct btrfs_backref_walk_ctx *ctx)
{ const u64 orig_bytenr = ctx->bytenr; constbool 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();
}
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;
}
/* -1 means we are in the bytenr of the data extent. */
level = -1;
ULIST_ITER_INIT(&uiter); while (1) { constunsignedlong 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;
/* * 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;
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;
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;
/* * 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, unsignedlong 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);
ret = btrfs_search_slot(NULL, extent_root, &key, path, 0, 0); if (ret < 0) return ret; if (ret == 0) { /* * Key with offset -1 found, there would have to exist an extent * item with such offset, but this is out of the valid range.
*/ return -EUCLEAN;
}
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; elseif (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];
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, btrfs_item_size(eb, path->slots[0]));
/* * 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
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