bcachefs: fsck: Fix reattach_inode() for subvol roots

bch_subvolume.fs_path_parent needs to be updated as well, it should
match inode.bi_parent_subvol.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Author: Kent Overstreet

fs/bcachefs/fsck.c

@@ -372,6 +372,18 @@ static int reattach_inode(struct btree_trans *trans, struct bch_inode_unpacked *
 	if (inode->bi_subvol) {
 		inode->bi_parent_subvol = BCACHEFS_ROOT_SUBVOL;
 
+		struct btree_iter subvol_iter;
+		struct bkey_i_subvolume *subvol =
+			bch2_bkey_get_mut_typed(trans, &subvol_iter,
+						BTREE_ID_subvolumes, POS(0, inode->bi_subvol),
+						0, subvolume);
+		ret = PTR_ERR_OR_ZERO(subvol);
+		if (ret)
+			return ret;
+
+		subvol->v.fs_path_parent = BCACHEFS_ROOT_SUBVOL;
+		bch2_trans_iter_exit(trans, &subvol_iter);
+
 		u64 root_inum;
 		ret = subvol_lookup(trans, inode->bi_parent_subvol,
 				    &dirent_snapshot, &root_inum);