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

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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: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2024-12-20 23:56:42 -05:00
parent 4541408391
commit b5e4cd0871
2 changed files with 46 additions and 7 deletions
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1
fs/bcachefs/errcode.h
View File

@ -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) \

52
fs/bcachefs/fsck.c
View File

@ -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;