bcachefs: Fix iterator leak in check_subvol()

A couple small error handling fixes
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/subvolume.c

@@ -92,35 +92,33 @@ static int check_subvol(struct btree_trans *trans,
 	}
 
 	struct bch_inode_unpacked inode;
-	struct btree_iter inode_iter = {};
-	ret = bch2_inode_peek_nowarn(trans, &inode_iter, &inode,
+	ret = bch2_inode_find_by_inum_nowarn_trans(trans,
 				    (subvol_inum) { k.k->p.offset, le64_to_cpu(subvol.v->inode) },
-				    0);
-	bch2_trans_iter_exit(trans, &inode_iter);
-
-	if (ret && !bch2_err_matches(ret, ENOENT))
-		return ret;
-
-	if (fsck_err_on(ret,
-			trans, subvol_to_missing_root,
-			"subvolume %llu points to missing subvolume root %llu:%u",
-			k.k->p.offset, le64_to_cpu(subvol.v->inode),
-			le32_to_cpu(subvol.v->snapshot))) {
-		ret = bch2_subvolume_delete(trans, iter->pos.offset);
-		bch_err_msg(c, ret, "deleting subvolume %llu", iter->pos.offset);
-		return ret ?: -BCH_ERR_transaction_restart_nested;
-	}
-
+				    &inode);
+	if (!ret) {
 		if (fsck_err_on(inode.bi_subvol != subvol.k->p.offset,
 				trans, subvol_root_wrong_bi_subvol,
 				"subvol root %llu:%u has wrong bi_subvol field: got %u, should be %llu",
-			inode.bi_inum, inode_iter.k.p.snapshot,
+				inode.bi_inum, inode.bi_snapshot,
 				inode.bi_subvol, subvol.k->p.offset)) {
 			inode.bi_subvol = subvol.k->p.offset;
 			ret = __bch2_fsck_write_inode(trans, &inode, le32_to_cpu(subvol.v->snapshot));
 			if (ret)
 				goto err;
 		}
+	} else if (bch2_err_matches(ret, ENOENT)) {
+		if (fsck_err(trans, subvol_to_missing_root,
+			     "subvolume %llu points to missing subvolume root %llu:%u",
+			     k.k->p.offset, le64_to_cpu(subvol.v->inode),
+			     le32_to_cpu(subvol.v->snapshot))) {
+			ret = bch2_subvolume_delete(trans, iter->pos.offset);
+			bch_err_msg(c, ret, "deleting subvolume %llu", iter->pos.offset);
+			ret = ret ?: -BCH_ERR_transaction_restart_nested;
+			goto err;
+		}
+	} else {
+		goto err;
+	}
 
 	if (!BCH_SUBVOLUME_SNAP(subvol.v)) {
 		u32 snapshot_root = bch2_snapshot_root(c, le32_to_cpu(subvol.v->snapshot));
@@ -137,7 +135,7 @@ static int check_subvol(struct btree_trans *trans,
 				"%s: snapshot tree %u not found", __func__, snapshot_tree);
 
 		if (ret)
-			return ret;
+			goto err;
 
 		if (fsck_err_on(le32_to_cpu(st.master_subvol) != subvol.k->p.offset,
 				trans, subvol_not_master_and_not_snapshot,
@@ -147,7 +145,7 @@ static int check_subvol(struct btree_trans *trans,
 				bch2_bkey_make_mut_typed(trans, iter, &subvol.s_c, 0, subvolume);
 			ret = PTR_ERR_OR_ZERO(s);
 			if (ret)
-				return ret;
+				goto err;
 
 			SET_BCH_SUBVOLUME_SNAP(&s->v, true);
 		}