Commit b5e4cd08 authored by Kent Overstreet's avatar Kent Overstreet
Browse files

bcachefs: Don't rely on snapshot_tree.master_subvol for reattaching 



Previously, fsck used the snapshot tree's master subvol for finding the
root inode number - but the master subvol might have been deleting, and
setting a new one should be a user operation; meaning we can't rely on
it existing.

Fortunately, for finding the root inode number in a tree of snapshots,
finding any associated subvolume works.

Signed-off-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent 45414083

fs/bcachefs/errcode.h

+1 −0
Original line number Diff line number Diff line
@@ -118,6 +118,7 @@ 
	x(ENOENT,			ENOENT_dev_not_found)			\

	x(ENOENT,			ENOENT_dev_idx_not_found)		\

	x(ENOENT,			ENOENT_inode_no_backpointer)		\

	x(ENOENT,			ENOENT_no_snapshot_tree_subvol)		\

	x(ENOTEMPTY,			ENOTEMPTY_dir_not_empty)		\

	x(ENOTEMPTY,			ENOTEMPTY_subvol_not_empty)		\

	x(EEXIST,			EEXIST_str_hash_set)			\

fs/bcachefs/fsck.c

+45 −7
Original line number Diff line number Diff line
@@ -205,6 +205,36 @@ static int __remove_dirent(struct btree_trans *trans, struct bpos pos) 
	return ret;

}



/*

 * Find any subvolume associated with a tree of snapshots

 * We can't rely on master_subvol - it might have been deleted.

 */

static int find_snapshot_tree_subvol(struct btree_trans *trans,

				     u32 tree_id, u32 *subvol)

{

	struct btree_iter iter;

	struct bkey_s_c k;

	int ret;



	for_each_btree_key_norestart(trans, iter, BTREE_ID_snapshots, POS_MIN, 0, k, ret) {

		if (k.k->type != KEY_TYPE_snapshot)

			continue;



		struct bkey_s_c_snapshot s = bkey_s_c_to_snapshot(k);

		if (le32_to_cpu(s.v->tree) != tree_id)

			continue;



		if (s.v->subvol) {

			*subvol = le32_to_cpu(s.v->subvol);

			goto found;

		}

	}

	ret = -BCH_ERR_ENOENT_no_snapshot_tree_subvol;

found:

	bch2_trans_iter_exit(trans, &iter);

	return ret;

}



/* Get lost+found, create if it doesn't exist: */

static int lookup_lostfound(struct btree_trans *trans, u32 snapshot,

			    struct bch_inode_unpacked *lostfound,
@@ -223,19 +253,24 @@ static int lookup_lostfound(struct btree_trans *trans, u32 snapshot, 
	if (ret)

		return ret;



	subvol_inum root_inum = { .subvol = le32_to_cpu(st.master_subvol) };

	u32 subvolid;

	ret = find_snapshot_tree_subvol(trans,

				bch2_snapshot_tree(c, snapshot), &subvolid);

	bch_err_msg(c, ret, "finding subvol associated with snapshot tree %u",

		    bch2_snapshot_tree(c, snapshot));

	if (ret)

		return ret;



	struct bch_subvolume subvol;

	ret = bch2_subvolume_get(trans, le32_to_cpu(st.master_subvol), false, &subvol);

	bch_err_msg(c, ret, "looking up root subvol %u for snapshot %u",

		    le32_to_cpu(st.master_subvol), snapshot);

	ret = bch2_subvolume_get(trans, subvolid, false, &subvol);

	bch_err_msg(c, ret, "looking up subvol %u for snapshot %u", subvolid, snapshot);

	if (ret)

		return ret;



	if (!subvol.inode) {

		struct btree_iter iter;

		struct bkey_i_subvolume *subvol = bch2_bkey_get_mut_typed(trans, &iter,

				BTREE_ID_subvolumes, POS(0, le32_to_cpu(st.master_subvol)),

				BTREE_ID_subvolumes, POS(0, subvolid),

				0, subvolume);

		ret = PTR_ERR_OR_ZERO(subvol);

		if (ret)
@@ -245,13 +280,16 @@ static int lookup_lostfound(struct btree_trans *trans, u32 snapshot, 
		bch2_trans_iter_exit(trans, &iter);

	}



	root_inum.inum = le64_to_cpu(subvol.inode);

	subvol_inum root_inum = {

		.subvol = subvolid,

		.inum = le64_to_cpu(subvol.inode)

	};



	struct bch_inode_unpacked root_inode;

	struct bch_hash_info root_hash_info;

	ret = lookup_inode(trans, root_inum.inum, snapshot, &root_inode);

	bch_err_msg(c, ret, "looking up root inode %llu for subvol %u",

		    root_inum.inum, le32_to_cpu(st.master_subvol));

		    root_inum.inum, subvolid);

	if (ret)

		return ret;