btrfs: switch extent_buffer::lock_nested to bool

The member is tracking simple status of the lock, we can use bool for
that and make some room for further space reduction in the structure.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -4679,7 +4679,7 @@ __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
 	rwlock_init(&eb->lock);
 	atomic_set(&eb->blocking_readers, 0);
 	atomic_set(&eb->blocking_writers, 0);
-	eb->lock_nested = 0;
+	eb->lock_nested = false;
 	init_waitqueue_head(&eb->write_lock_wq);
 	init_waitqueue_head(&eb->read_lock_wq);
 

fs/btrfs/extent_io.h

@@ -162,7 +162,7 @@ struct extent_buffer {
 
 	atomic_t blocking_writers;
 	atomic_t blocking_readers;
-	short lock_nested;
+	bool lock_nested;
 	/* >= 0 if eb belongs to a log tree, -1 otherwise */
 	short log_index;
 

fs/btrfs/locking.c

@@ -172,7 +172,7 @@ void btrfs_tree_read_lock(struct extent_buffer *eb)
 		 * called on a partly (write-)locked tree.
 		 */
 		BUG_ON(eb->lock_nested);
-		eb->lock_nested = 1;
+		eb->lock_nested = true;
 		read_unlock(&eb->lock);
 		return;
 	}
@@ -261,7 +261,7 @@ void btrfs_tree_read_unlock(struct extent_buffer *eb)
 	 * field only matters to the lock owner.
 	 */
 	if (eb->lock_nested && current->pid == eb->lock_owner) {
-		eb->lock_nested = 0;
+		eb->lock_nested = false;
 		return;
 	}
 	btrfs_assert_tree_read_locked(eb);
@@ -282,7 +282,7 @@ void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
 	 * field only matters to the lock owner.
 	 */
 	if (eb->lock_nested && current->pid == eb->lock_owner) {
-		eb->lock_nested = 0;
+		eb->lock_nested = false;
 		return;
 	}
 	btrfs_assert_tree_read_locked(eb);