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bcachefs: Don't downgrade iterators in bch2_trans_get_iter()

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This fixes a livelock with btree node splits.

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
2021-04-15 12:36:40 -04:00
committed by Kent Overstreet
parent 2527dd9158
commit 558509aa01
1 changed files with 8 additions and 3 deletions
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11
fs/bcachefs/btree_iter.c
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@@ -2038,13 +2038,18 @@ struct btree_iter *__bch2_trans_get_iter(struct btree_trans *trans,
iter->snapshot = pos.snapshot;
locks_want = min(locks_want, BTREE_MAX_DEPTH);
/*
* If the iterator has locks_want greater than requested, we explicitly
* do not downgrade it here - on transaction restart because btree node
* split needs to upgrade locks, we might be putting/getting the
* iterator again. Downgrading iterators only happens via an explicit
* bch2_trans_downgrade().
*/
locks_want = min(locks_want, BTREE_MAX_DEPTH);
if (locks_want > iter->locks_want) {
iter->locks_want = locks_want;
btree_iter_get_locks(iter, true, false);
} else if (locks_want < iter->locks_want) {
__bch2_btree_iter_downgrade(iter, locks_want);
}
while (iter->level < depth) {