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bcachefs: Fix transaction restarts due to upgrading of cloned iterators

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This fixes a regression from
  52d86202fd bcachefs: Improve bch2_btree_iter_traverse_all()

We want to avoid mucking with other iterators in the btree transaction
in operations that are only supposed to be touching individual iterators
- that patch was a cleanup to move lock ordering handling to
bch2_btree_iter_traverse_all(). But it broke upgrading of cloned
iterators.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2021-04-16 14:29:26 -04:00 committed by Kent Overstreet
parent 96f399d0ee
commit 5e6a668b19
1 changed files with 34 additions and 1 deletions
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35
fs/bcachefs/btree_iter.c
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@ -387,11 +387,44 @@ bool bch2_btree_iter_relock(struct btree_iter *iter, bool trace)
bool __bch2_btree_iter_upgrade(struct btree_iter *iter,
unsigned new_locks_want)
{
struct btree_iter *linked;
EBUG_ON(iter->locks_want >= new_locks_want);
iter->locks_want = new_locks_want;
return btree_iter_get_locks(iter, true, true);
if (btree_iter_get_locks(iter, true, true))
return true;
/*
* XXX: this is ugly - we'd prefer to not be mucking with other
* iterators in the btree_trans here.
*
* On failure to upgrade the iterator, setting iter->locks_want and
* calling get_locks() is sufficient to make bch2_btree_iter_traverse()
* get the locks we want on transaction restart.
*
* But if this iterator was a clone, on transaction restart what we did
* to this iterator isn't going to be preserved.
*
* Possibly we could add an iterator field for the parent iterator when
* an iterator is a copy - for now, we'll just upgrade any other
* iterators with the same btree id.
*
* The code below used to be needed to ensure ancestor nodes get locked
* before interior nodes - now that's handled by
* bch2_btree_iter_traverse_all().
*/
trans_for_each_iter(iter->trans, linked)
if (linked != iter &&
btree_iter_type(linked) == btree_iter_type(iter) &&
linked->btree_id == iter->btree_id &&
linked->locks_want < new_locks_want) {
linked->locks_want = new_locks_want;
btree_iter_get_locks(linked, true, false);
}
return false;
}
void __bch2_btree_iter_downgrade(struct btree_iter *iter,