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| author | Jan Schmidt <list.btrfs@jan-o-sch.net> | 2012-06-04 16:54:57 +0200 |
|---|---|---|
| committer | Jan Schmidt <list.btrfs@jan-o-sch.net> | 2012-06-14 18:44:21 +0200 |
| commit | 8ba97a15e7d4f70b9af71fa1db86a28dd17ad1b2 (patch) | |
| tree | 08a2e49743eee382eca3e4b12415b372f898e3d8 /fs | |
| parent | f617e2fd52484fb74236a597d0f9068ec7d9d2dd (diff) | |
| download | op-kernel-dev-8ba97a15e7d4f70b9af71fa1db86a28dd17ad1b2.zip op-kernel-dev-8ba97a15e7d4f70b9af71fa1db86a28dd17ad1b2.tar.gz | |
Btrfs: use btrfs_read_lock_root_node in get_old_root
get_old_root could race with root node updates because we weren't locking
the node early enough. Use btrfs_read_lock_root_node to grab the root locked
in the very beginning and release the lock as soon as possible (just like
btrfs_search_slot does).
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/btrfs/ctree.c | 20 |
1 files changed, 16 insertions, 4 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 836e4e0..2cde7b0 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -1143,6 +1143,13 @@ tree_mod_log_rewind(struct btrfs_fs_info *fs_info, struct extent_buffer *eb, return eb_rewin; } +/* + * get_old_root() rewinds the state of @root's root node to the given @time_seq + * value. If there are no changes, the current root->root_node is returned. If + * anything changed in between, there's a fresh buffer allocated on which the + * rewind operations are done. In any case, the returned buffer is read locked. + * Returns NULL on error (with no locks held). + */ static inline struct extent_buffer * get_old_root(struct btrfs_root *root, u64 time_seq) { @@ -1151,6 +1158,7 @@ get_old_root(struct btrfs_root *root, u64 time_seq) struct tree_mod_root *old_root; u64 old_generation; + eb = btrfs_read_lock_root_node(root); tm = __tree_mod_log_oldest_root(root->fs_info, root, time_seq); if (!tm) return root->node; @@ -1173,15 +1181,21 @@ get_old_root(struct btrfs_root *root, u64 time_seq) /* there's a root replace operation for the current root */ eb = alloc_dummy_extent_buffer(tm->index << PAGE_CACHE_SHIFT, root->nodesize); + } + btrfs_tree_read_unlock(root->node); + free_extent_buffer(root->node); + if (!eb) + return NULL; + btrfs_tree_read_lock(eb); + if (old_root->logical != root->node->start) { btrfs_set_header_bytenr(eb, eb->start); btrfs_set_header_backref_rev(eb, BTRFS_MIXED_BACKREF_REV); btrfs_set_header_owner(eb, root->root_key.objectid); } - if (!eb) - return NULL; btrfs_set_header_level(eb, old_root->level); btrfs_set_header_generation(eb, old_generation); __tree_mod_log_rewind(eb, time_seq, tm); + extent_buffer_get(eb); return eb; } @@ -2612,9 +2626,7 @@ int btrfs_search_old_slot(struct btrfs_root *root, struct btrfs_key *key, again: b = get_old_root(root, time_seq); - extent_buffer_get(b); level = btrfs_header_level(b); - btrfs_tree_read_lock(b); p->locks[level] = BTRFS_READ_LOCK; while (b) { |
