diff options
| -rw-r--r-- | fs/btrfs/locking.c | 32 |
1 files changed, 21 insertions, 11 deletions
diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c index 00edf91c3d1c..4cd593a2f58c 100644 --- a/fs/btrfs/locking.c +++ b/fs/btrfs/locking.c @@ -109,7 +109,7 @@ void btrfs_set_lock_blocking_write(struct extent_buffer *eb) if (eb->blocking_writers == 0) { btrfs_assert_spinning_writers_put(eb); btrfs_assert_tree_locked(eb); - eb->blocking_writers = 1; + WRITE_ONCE(eb->blocking_writers, 1); write_unlock(&eb->lock); } } @@ -145,7 +145,7 @@ again: } read_unlock(&eb->lock); wait_event(eb->write_lock_wq, - eb->blocking_writers == 0); + READ_ONCE(eb->blocking_writers) == 0); goto again; } btrfs_assert_tree_read_locks_get(eb); @@ -160,11 +160,12 @@ again: */ int btrfs_tree_read_lock_atomic(struct extent_buffer *eb) { - if (eb->blocking_writers) + if (READ_ONCE(eb->blocking_writers)) return 0; read_lock(&eb->lock); - if (eb->blocking_writers) { + /* Refetch value after lock */ + if (READ_ONCE(eb->blocking_writers)) { read_unlock(&eb->lock); return 0; } @@ -180,13 +181,14 @@ int btrfs_tree_read_lock_atomic(struct extent_buffer *eb) */ int btrfs_try_tree_read_lock(struct extent_buffer *eb) { - if (eb->blocking_writers) + if (READ_ONCE(eb->blocking_writers)) return 0; if (!read_trylock(&eb->lock)) return 0; - if (eb->blocking_writers) { + /* Refetch value after lock */ + if (READ_ONCE(eb->blocking_writers)) { read_unlock(&eb->lock); return 0; } @@ -202,11 +204,12 @@ int btrfs_try_tree_read_lock(struct extent_buffer *eb) */ int btrfs_try_tree_write_lock(struct extent_buffer *eb) { - if (eb->blocking_writers || atomic_read(&eb->blocking_readers)) + if (READ_ONCE(eb->blocking_writers) || atomic_read(&eb->blocking_readers)) return 0; write_lock(&eb->lock); - if (eb->blocking_writers || atomic_read(&eb->blocking_readers)) { + /* Refetch value after lock */ + if (READ_ONCE(eb->blocking_writers) || atomic_read(&eb->blocking_readers)) { write_unlock(&eb->lock); return 0; } @@ -277,9 +280,11 @@ void btrfs_tree_lock(struct extent_buffer *eb) WARN_ON(eb->lock_owner == current->pid); again: wait_event(eb->read_lock_wq, atomic_read(&eb->blocking_readers) == 0); - wait_event(eb->write_lock_wq, eb->blocking_writers == 0); + wait_event(eb->write_lock_wq, READ_ONCE(eb->blocking_writers) == 0); write_lock(&eb->lock); - if (atomic_read(&eb->blocking_readers) || eb->blocking_writers) { + /* Refetch value after lock */ + if (atomic_read(&eb->blocking_readers) || + READ_ONCE(eb->blocking_writers)) { write_unlock(&eb->lock); goto again; } @@ -294,6 +299,10 @@ again: */ void btrfs_tree_unlock(struct extent_buffer *eb) { + /* + * This is read both locked and unlocked but always by the same thread + * that already owns the lock so we don't need to use READ_ONCE + */ int blockers = eb->blocking_writers; BUG_ON(blockers > 1); @@ -305,7 +314,8 @@ void btrfs_tree_unlock(struct extent_buffer *eb) if (blockers) { btrfs_assert_no_spinning_writers(eb); - eb->blocking_writers = 0; + /* Unlocked write */ + WRITE_ONCE(eb->blocking_writers, 0); /* * We need to order modifying blocking_writers above with * actually waking up the sleepers to ensure they see the |