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bcachefs: Kill equiv_seen arg to delete_dead_snapshots_process_key()

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When deleting dead snapshots, we move keys from redundant interior
snapshot nodes to child nodes - unless there's already a key, in which
case the ancestor key is deleted.

Previously, we tracked via equiv_seen whether the child snapshot had a
key, but this was tricky w.r.t. transaction restarts, and not
transactionally safe w.r.t. updates in the child snapshot.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet
2024-12-12 02:41:37 -05:00
parent 92e31d4251
commit 85c060f62d
1 changed files with 17 additions and 34 deletions
Download Patch File Download Diff File Expand all files Collapse all files
fs/bcachefs/snapshot.c
+17 -34
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@@ -1421,9 +1421,7 @@ int bch2_snapshot_node_create(struct btree_trans *trans, u32 parent,
static int delete_dead_snapshots_process_key(struct btree_trans *trans,
struct btree_iter *iter,
struct bkey_s_c k,
snapshot_id_list *deleted,
snapshot_id_list *equiv_seen,
struct bpos *last_pos)
snapshot_id_list *deleted)
{
int ret = bch2_check_key_has_snapshot(trans, iter, k);
if (ret)
@@ -1434,24 +1432,10 @@ static int delete_dead_snapshots_process_key(struct btree_trans *trans,
if (!equiv) /* key for invalid snapshot node, but we chose not to delete */
return 0;
if (!bkey_eq(k.k->p, *last_pos))
equiv_seen->nr = 0;
if (snapshot_list_has_id(deleted, k.k->p.snapshot))
return bch2_btree_delete_at(trans, iter,
BTREE_UPDATE_internal_snapshot_node);
if (!bpos_eq(*last_pos, k.k->p) &&
snapshot_list_has_id(equiv_seen, equiv))
return bch2_btree_delete_at(trans, iter,
BTREE_UPDATE_internal_snapshot_node);
*last_pos = k.k->p;
ret = snapshot_list_add_nodup(c, equiv_seen, equiv);
if (ret)
return ret;
/*
* When we have a linear chain of snapshot nodes, we consider
* those to form an equivalence class: we're going to collapse
@@ -1473,20 +1457,23 @@ static int delete_dead_snapshots_process_key(struct btree_trans *trans,
new->k.p.snapshot = equiv;
struct btree_iter new_iter;
bch2_trans_iter_init(trans, &new_iter, iter->btree_id, new->k.p,
BTREE_ITER_all_snapshots|
BTREE_ITER_cached|
BTREE_ITER_intent);
ret = bch2_btree_iter_traverse(&new_iter) ?:
bch2_trans_update(trans, &new_iter, new,
BTREE_UPDATE_internal_snapshot_node) ?:
bch2_btree_delete_at(trans, iter,
BTREE_UPDATE_internal_snapshot_node);
bch2_trans_iter_exit(trans, &new_iter);
struct btree_iter dst_iter;
struct bkey_s_c dst_k = bch2_bkey_get_iter(trans, &dst_iter,
iter->btree_id, new->k.p,
BTREE_ITER_all_snapshots|
BTREE_ITER_intent);
ret = bkey_err(dst_k);
if (ret)
return ret;
ret = (bkey_deleted(dst_k.k)
? bch2_trans_update(trans, &dst_iter, new,
BTREE_UPDATE_internal_snapshot_node)
: 0) ?:
bch2_btree_delete_at(trans, iter,
BTREE_UPDATE_internal_snapshot_node);
bch2_trans_iter_exit(trans, &dst_iter);
return ret;
}
return 0;
@@ -1648,8 +1635,6 @@ int bch2_delete_dead_snapshots(struct bch_fs *c)
goto err;
for (unsigned btree = 0; btree < BTREE_ID_NR; btree++) {
struct bpos last_pos = POS_MIN;
snapshot_id_list equiv_seen = { 0 };
struct disk_reservation res = { 0 };
if (!btree_type_has_snapshots(btree))
@@ -1659,11 +1644,9 @@ int bch2_delete_dead_snapshots(struct bch_fs *c)
btree, POS_MIN,
BTREE_ITER_prefetch|BTREE_ITER_all_snapshots, k,
&res, NULL, BCH_TRANS_COMMIT_no_enospc,
delete_dead_snapshots_process_key(trans, &iter, k, &deleted,
&equiv_seen, &last_pos));
delete_dead_snapshots_process_key(trans, &iter, k, &deleted));
bch2_disk_reservation_put(c, &res);
darray_exit(&equiv_seen);
bch_err_msg(c, ret, "deleting keys from dying snapshots");
if (ret)