diff options
Diffstat (limited to 'fs/btrfs/locking.h')
| -rw-r--r-- | fs/btrfs/locking.h | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/fs/btrfs/locking.h b/fs/btrfs/locking.h index d715846c10b8..3ea81ed3320b 100644 --- a/fs/btrfs/locking.h +++ b/fs/btrfs/locking.h @@ -16,11 +16,81 @@ #define BTRFS_WRITE_LOCK_BLOCKING 3 #define BTRFS_READ_LOCK_BLOCKING 4 +/* + * We are limited in number of subclasses by MAX_LOCKDEP_SUBCLASSES, which at + * the time of this patch is 8, which is how many we use. Keep this in mind if + * you decide you want to add another subclass. + */ +enum btrfs_lock_nesting { + BTRFS_NESTING_NORMAL, + + /* + * When we COW a block we are holding the lock on the original block, + * and since our lockdep maps are rootid+level, this confuses lockdep + * when we lock the newly allocated COW'd block. Handle this by having + * a subclass for COW'ed blocks so that lockdep doesn't complain. + */ + BTRFS_NESTING_COW, + + /* + * Oftentimes we need to lock adjacent nodes on the same level while + * still holding the lock on the original node we searched to, such as + * for searching forward or for split/balance. + * + * Because of this we need to indicate to lockdep that this is + * acceptable by having a different subclass for each of these + * operations. + */ + BTRFS_NESTING_LEFT, + BTRFS_NESTING_RIGHT, + + /* + * When splitting we will be holding a lock on the left/right node when + * we need to cow that node, thus we need a new set of subclasses for + * these two operations. + */ + BTRFS_NESTING_LEFT_COW, + BTRFS_NESTING_RIGHT_COW, + + /* + * When splitting we may push nodes to the left or right, but still use + * the subsequent nodes in our path, keeping our locks on those adjacent + * blocks. Thus when we go to allocate a new split block we've already + * used up all of our available subclasses, so this subclass exists to + * handle this case where we need to allocate a new split block. + */ + BTRFS_NESTING_SPLIT, + + /* + * When promoting a new block to a root we need to have a special + * subclass so we don't confuse lockdep, as it will appear that we are + * locking a higher level node before a lower level one. Copying also + * has this problem as it appears we're locking the same block again + * when we make a snapshot of an existing root. + */ + BTRFS_NESTING_NEW_ROOT, + + /* + * We are limited to MAX_LOCKDEP_SUBLCLASSES number of subclasses, so + * add this in here and add a static_assert to keep us from going over + * the limit. As of this writing we're limited to 8, and we're + * definitely using 8, hence this check to keep us from messing up in + * the future. + */ + BTRFS_NESTING_MAX, +}; + +static_assert(BTRFS_NESTING_MAX <= MAX_LOCKDEP_SUBCLASSES, + "too many lock subclasses defined"); + struct btrfs_path; +void __btrfs_tree_lock(struct extent_buffer *eb, enum btrfs_lock_nesting nest); void btrfs_tree_lock(struct extent_buffer *eb); void btrfs_tree_unlock(struct extent_buffer *eb); +void __btrfs_tree_read_lock(struct extent_buffer *eb, enum btrfs_lock_nesting nest, + bool recurse); void btrfs_tree_read_lock(struct extent_buffer *eb); void btrfs_tree_read_unlock(struct extent_buffer *eb); void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb); @@ -29,6 +99,14 @@ void btrfs_set_lock_blocking_write(struct extent_buffer *eb); int btrfs_try_tree_read_lock(struct extent_buffer *eb); int btrfs_try_tree_write_lock(struct extent_buffer *eb); int btrfs_tree_read_lock_atomic(struct extent_buffer *eb); +struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root); +struct extent_buffer *__btrfs_read_lock_root_node(struct btrfs_root *root, + bool recurse); + +static inline struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root) +{ + return __btrfs_read_lock_root_node(root, false); +} #ifdef CONFIG_BTRFS_DEBUG static inline void btrfs_assert_tree_locked(struct extent_buffer *eb) { |