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bcachefs: Improve check_snapshot_exists()

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Check if we have snapshot_trees or subvolumes that refer to the snapshot
node being reconstructed, and use them.

With this, the kill_btree_root test that blows away the snapshots btree
now passes, and we're able to successfully reconstruct.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2024-10-09 21:28:11 -04:00
parent 9183c2b11e
commit c986dd7ecb
1 changed files with 30 additions and 2 deletions
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32
fs/bcachefs/snapshot.c
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@ -905,12 +905,30 @@ static int check_snapshot_exists(struct btree_trans *trans, u32 id)
if (bch2_snapshot_equiv(c, id))
return 0;
/* 0 is an invalid tree ID */
/* Do we need to reconstruct the snapshot_tree entry as well? */
struct btree_iter iter;
struct bkey_s_c k;
int ret = 0;
u32 tree_id = 0;
int ret = bch2_snapshot_tree_create(trans, id, 0, &tree_id);
for_each_btree_key_norestart(trans, iter, BTREE_ID_snapshot_trees, POS_MIN,
0, k, ret) {
if (le32_to_cpu(bkey_s_c_to_snapshot_tree(k).v->root_snapshot) == id) {
tree_id = k.k->p.offset;
break;
}
}
bch2_trans_iter_exit(trans, &iter);
if (ret)
return ret;
if (!tree_id) {
ret = bch2_snapshot_tree_create(trans, id, 0, &tree_id);
if (ret)
return ret;
}
struct bkey_i_snapshot *snapshot = bch2_trans_kmalloc(trans, sizeof(*snapshot));
ret = PTR_ERR_OR_ZERO(snapshot);
if (ret)
@ -921,6 +939,16 @@ static int check_snapshot_exists(struct btree_trans *trans, u32 id)
snapshot->v.tree = cpu_to_le32(tree_id);
snapshot->v.btime.lo = cpu_to_le64(bch2_current_time(c));
for_each_btree_key_norestart(trans, iter, BTREE_ID_subvolumes, POS_MIN,
0, k, ret) {
if (le32_to_cpu(bkey_s_c_to_subvolume(k).v->snapshot) == id) {
snapshot->v.subvol = cpu_to_le32(k.k->p.offset);
SET_BCH_SNAPSHOT_SUBVOL(&snapshot->v, true);
break;
}
}
bch2_trans_iter_exit(trans, &iter);
return bch2_btree_insert_trans(trans, BTREE_ID_snapshots, &snapshot->k_i, 0) ?:
bch2_mark_snapshot(trans, BTREE_ID_snapshots, 0,
bkey_s_c_null, bkey_i_to_s(&snapshot->k_i), 0) ?: