btrfs: assert that extent buffers are write locked instead of only locked

We currently use lockdep_assert_held() at btrfs_assert_tree_locked(), and
that checks that we hold a lock either in read mode or write mode.

However in all contexts we use btrfs_assert_tree_locked(), we actually
want to check if we are holding a write lock on the extent buffer's rw
semaphore - it would be a bug if in any of those contexts we were holding
a read lock instead.

So change btrfs_assert_tree_locked() to use lockdep_assert_held_write()
instead and, to make it more explicit, rename btrfs_assert_tree_locked()
to btrfs_assert_tree_write_locked(), so that it's clear we want to check
we are holding a write lock.

For now there are no contexts where we want to assert that we must have
a read lock, but in case that is needed in the future, we can add a new
helper function that just calls out lockdep_assert_held_read().

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/fs/btrfs/locking.h b/fs/btrfs/locking.h
index a2e1f1f5c6e3..bbc45534ae9a 100644
--- a/fs/btrfs/locking.h
+++ b/fs/btrfs/locking.h
@@ -96,11 +96,12 @@ struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root);
 struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root);
 
 #ifdef CONFIG_BTRFS_DEBUG
-static inline void btrfs_assert_tree_locked(struct extent_buffer *eb) {
-	lockdep_assert_held(&eb->lock);
+static inline void btrfs_assert_tree_write_locked(struct extent_buffer *eb)
+{
+	lockdep_assert_held_write(&eb->lock);
 }
 #else
-static inline void btrfs_assert_tree_locked(struct extent_buffer *eb) { }
+static inline void btrfs_assert_tree_write_locked(struct extent_buffer *eb) { }
 #endif
 
 void btrfs_unlock_up_safe(struct btrfs_path *path, int level);