1 files changed, 10 insertions, 16 deletions

diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c
index 99ccab86bb..6a0b7abb5b 100644
--- a/fs/btrfs/locking.c
+++ b/fs/btrfs/locking.c
@@ -97,7 +97,7 @@ void btrfs_set_buffer_lockdep_class(u64 objectid, struct extent_buffer *eb, int
 void btrfs_maybe_reset_lockdep_class(struct btrfs_root *root, struct extent_buffer *eb)
 {
 	if (test_bit(BTRFS_ROOT_RESET_LOCKDEP_CLASS, &root->state))
-		btrfs_set_buffer_lockdep_class(root->root_key.objectid,
+		btrfs_set_buffer_lockdep_class(btrfs_root_id(root),
 					       eb, btrfs_header_level(eb));
 }
 
@@ -129,14 +129,14 @@ static void btrfs_set_eb_lock_owner(struct extent_buffer *eb, pid_t owner) { }
  */
 
 /*
- * __btrfs_tree_read_lock - lock extent buffer for read
+ * btrfs_tree_read_lock_nested - lock extent buffer for read
  * @eb:		the eb to be locked
  * @nest:	the nesting level to be used for lockdep
  *
  * This takes the read lock on the extent buffer, using the specified nesting
  * level for lockdep purposes.
  */
-void __btrfs_tree_read_lock(struct extent_buffer *eb, enum btrfs_lock_nesting nest)
+void btrfs_tree_read_lock_nested(struct extent_buffer *eb, enum btrfs_lock_nesting nest)
 {
 	u64 start_ns = 0;
 
@@ -147,11 +147,6 @@ void __btrfs_tree_read_lock(struct extent_buffer *eb, enum btrfs_lock_nesting ne
 	trace_btrfs_tree_read_lock(eb, start_ns);
 }
 
-void btrfs_tree_read_lock(struct extent_buffer *eb)
-{
-	__btrfs_tree_read_lock(eb, BTRFS_NESTING_NORMAL);
-}
-
 /*
  * Try-lock for read.
  *
@@ -198,7 +193,7 @@ void btrfs_tree_read_unlock(struct extent_buffer *eb)
  *
  * Returns with the eb->lock write locked.
  */
-void __btrfs_tree_lock(struct extent_buffer *eb, enum btrfs_lock_nesting nest)
+void btrfs_tree_lock_nested(struct extent_buffer *eb, enum btrfs_lock_nesting nest)
 	__acquires(&eb->lock)
 {
 	u64 start_ns = 0;
@@ -211,11 +206,6 @@ void __btrfs_tree_lock(struct extent_buffer *eb, enum btrfs_lock_nesting nest)
 	trace_btrfs_tree_lock(eb, start_ns);
 }
 
-void btrfs_tree_lock(struct extent_buffer *eb)
-{
-	__btrfs_tree_lock(eb, BTRFS_NESTING_NORMAL);
-}
-
 /*
  * Release the write lock.
  */
@@ -374,8 +364,12 @@ void btrfs_drew_write_lock(struct btrfs_drew_lock *lock)
 
 void btrfs_drew_write_unlock(struct btrfs_drew_lock *lock)
 {
-	atomic_dec(&lock->writers);
-	cond_wake_up(&lock->pending_readers);
+	/*
+	 * atomic_dec_and_test() implies a full barrier, so woken up readers are
+	 * guaranteed to see the decrement.
+	 */
+	if (atomic_dec_and_test(&lock->writers))
+		wake_up(&lock->pending_readers);
 }
 
 void btrfs_drew_read_lock(struct btrfs_drew_lock *lock)