bcachefs: Check for subvolume children when deleting subvolumes

Recursively destroying subvolumes isn't allowed yet.

Fixes: https://github.com/koverstreet/bcachefs/issues/634Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/dirent.c

@@ -525,7 +525,7 @@ int bch2_empty_dir_snapshot(struct btree_trans *trans, u64 dir, u32 subvol, u32
 			struct bkey_s_c_dirent d = bkey_s_c_to_dirent(k);
 			if (d.v->d_type == DT_SUBVOL && le32_to_cpu(d.v->d_parent_subvol) != subvol)
 				continue;
-			ret = -ENOTEMPTY;
+			ret = -BCH_ERR_ENOTEMPTY_dir_not_empty;
 			break;
 		}
 	bch2_trans_iter_exit(trans, &iter);

fs/bcachefs/errcode.h

@@ -109,6 +109,8 @@
 	x(ENOENT,			ENOENT_dirent_doesnt_match_inode)	\
 	x(ENOENT,			ENOENT_dev_not_found)			\
 	x(ENOENT,			ENOENT_dev_idx_not_found)		\
+	x(ENOTEMPTY,			ENOTEMPTY_dir_not_empty)		\
+	x(ENOTEMPTY,			ENOTEMPTY_subvol_not_empty)		\
 	x(0,				open_buckets_empty)			\
 	x(0,				freelist_empty)				\
 	x(BCH_ERR_freelist_empty,	no_buckets_found)			\

fs/bcachefs/fs-common.c

@@ -243,7 +243,7 @@ int bch2_unlink_trans(struct btree_trans *trans,
 		      struct bch_inode_unpacked *dir_u,
 		      struct bch_inode_unpacked *inode_u,
 		      const struct qstr *name,
-		      bool deleting_snapshot)
+		      bool deleting_subvol)
 {
 	struct bch_fs *c = trans->c;
 	struct btree_iter dir_iter = { NULL };
@@ -271,18 +271,25 @@ int bch2_unlink_trans(struct btree_trans *trans,
 	if (ret)
 		goto err;
 
-	if (!deleting_snapshot && S_ISDIR(inode_u->bi_mode)) {
+	if (!deleting_subvol && S_ISDIR(inode_u->bi_mode)) {
 		ret = bch2_empty_dir_trans(trans, inum);
 		if (ret)
 			goto err;
 	}
 
-	if (deleting_snapshot && !inode_u->bi_subvol) {
+	if (deleting_subvol && !inode_u->bi_subvol) {
 		ret = -BCH_ERR_ENOENT_not_subvol;
 		goto err;
 	}
 
-	if (deleting_snapshot || inode_u->bi_subvol) {
+	if (inode_u->bi_subvol) {
+		/* Recursive subvolume destroy not allowed (yet?) */
+		ret = bch2_subvol_has_children(trans, inode_u->bi_subvol);
+		if (ret)
+			goto err;
+	}
+
+	if (deleting_subvol || inode_u->bi_subvol) {
 		ret = bch2_subvolume_unlink(trans, inode_u->bi_subvol);
 		if (ret)
 			goto err;
@@ -479,10 +486,10 @@ int bch2_rename_trans(struct btree_trans *trans,
 			goto err;
 		}
 
-		if (S_ISDIR(dst_inode_u->bi_mode) &&
-		    bch2_empty_dir_trans(trans, dst_inum)) {
-			ret = -ENOTEMPTY;
-			goto err;
+		if (S_ISDIR(dst_inode_u->bi_mode)) {
+			ret = bch2_empty_dir_trans(trans, dst_inum);
+			if (ret)
+				goto err;
 		}
 	}
 

fs/bcachefs/subvolume.c

@@ -262,6 +262,19 @@ int bch2_subvolume_trigger(struct btree_trans *trans,
 	return 0;
 }
 
+int bch2_subvol_has_children(struct btree_trans *trans, u32 subvol)
+{
+	struct btree_iter iter;
+
+	bch2_trans_iter_init(trans, &iter, BTREE_ID_subvolume_children, POS(subvol, 0), 0);
+	struct bkey_s_c k = bch2_btree_iter_peek(&iter);
+	bch2_trans_iter_exit(trans, &iter);
+
+	return bkey_err(k) ?: k.k && k.k->p.inode == subvol
+		? -BCH_ERR_ENOTEMPTY_subvol_not_empty
+		: 0;
+}
+
 static __always_inline int
 bch2_subvolume_get_inlined(struct btree_trans *trans, unsigned subvol,
 			   bool inconsistent_if_not_found,

fs/bcachefs/subvolume.h

@@ -23,6 +23,7 @@ int bch2_subvolume_trigger(struct btree_trans *, enum btree_id, unsigned,
 	.min_val_size	= 16,					\
 })
 
+int bch2_subvol_has_children(struct btree_trans *, u32);
 int bch2_subvolume_get(struct btree_trans *, unsigned,
 		       bool, int, struct bch_subvolume *);
 int bch2_subvolume_get_snapshot(struct btree_trans *, u32, u32 *);