btrfs: simplify IS_ERR/PTR_ERR checks

IS_ERR(p) && PTR_ERR(p) == n is a weird way to spell p == ERR_PTR(n).

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: David Sterba <dsterba@suse.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/transaction.c

@@ -680,7 +680,7 @@ btrfs_attach_transaction_barrier(struct btrfs_root *root)
 
 	trans = start_transaction(root, 0, TRANS_ATTACH,
 				  BTRFS_RESERVE_NO_FLUSH, true);
-	if (IS_ERR(trans) && PTR_ERR(trans) == -ENOENT)
+	if (trans == ERR_PTR(-ENOENT))
 		btrfs_wait_for_commit(root->fs_info, 0);
 
 	return trans;

fs/btrfs/tree-log.c

@@ -2181,7 +2181,7 @@ again:
 						     dir_key->offset,
 						     name, name_len, 0);
 		}
-		if (!log_di || (IS_ERR(log_di) && PTR_ERR(log_di) == -ENOENT)) {
+		if (!log_di || log_di == ERR_PTR(-ENOENT)) {
 			btrfs_dir_item_key_to_cpu(eb, di, &location);
 			btrfs_release_path(path);
 			btrfs_release_path(log_path);
@@ -5011,8 +5011,7 @@ again:
 				 * we don't need to do more work nor fallback to
 				 * a transaction commit.
 				 */
-				if (IS_ERR(other_inode) &&
-				    PTR_ERR(other_inode) == -ENOENT) {
+				if (other_inode == ERR_PTR(-ENOENT)) {
 					goto next_key;
 				} else if (IS_ERR(other_inode)) {
 					err = PTR_ERR(other_inode);