btrfs: Don't assign retval of btrfs_try_tree_write_lock/btrfs_tree_read_lock_atomic

Those function are simple boolean predicates there is no need to assign
their return values to interim variables. Use them directly as
predicates. No functional changes.
Signed-off-by: NNikolay Borisov <nborisov@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/ctree.c

@@ -2913,15 +2913,13 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 			if (!p->skip_locking) {
 				level = btrfs_header_level(b);
 				if (level <= write_lock_level) {
-					err = btrfs_try_tree_write_lock(b);
-					if (!err) {
+					if (!btrfs_try_tree_write_lock(b)) {
 						btrfs_set_path_blocking(p);
 						btrfs_tree_lock(b);
 					}
 					p->locks[level] = BTRFS_WRITE_LOCK;
 				} else {
-					err = btrfs_tree_read_lock_atomic(b);
-					if (!err) {
+					if (!btrfs_tree_read_lock_atomic(b)) {
 						btrfs_set_path_blocking(p);
 						btrfs_tree_read_lock(b);
 					}
@@ -3055,8 +3053,7 @@ int btrfs_search_old_slot(struct btrfs_root *root, const struct btrfs_key *key,
 			}
 
 			level = btrfs_header_level(b);
-			err = btrfs_tree_read_lock_atomic(b);
-			if (!err) {
+			if (!btrfs_tree_read_lock_atomic(b)) {
 				btrfs_set_path_blocking(p);
 				btrfs_tree_read_lock(b);
 			}