Re: [PATCH 4/6] block: clear BIO_PERCPU_CACHE flag if polling isn't supported
From: Keith Busch <kbusch@kernel.org>
Date: 2021-08-13 20:17:27
Also in:
io-uring
On Thu, Aug 12, 2021 at 11:41:58AM -0600, Jens Axboe wrote:
quoted hunk ↗ jump to hunk
Indeed. Wonder if we should make that a small helper, as any clear of REQ_HIPRI should clear BIO_PERCPU_CACHE as well.diff --git a/block/blk-core.c b/block/blk-core.c index 7e852242f4cc..d2722ecd4d9b 100644 --- a/block/blk-core.c +++ b/block/blk-core.c@@ -821,11 +821,8 @@ static noinline_for_stack bool submit_bio_checks(struct bio *bio) } } - if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) { - /* can't support alloc cache if we turn off polling */ - bio_clear_flag(bio, BIO_PERCPU_CACHE); - bio->bi_opf &= ~REQ_HIPRI; - } + if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) + bio_clear_hipri(bio);
Since BIO_PERCPU_CACHE doesn't work without REQ_HIRPI, should this check look more like this? if (!test_bit(QUEUE_FLAG_POLL, &q->queue_flags)) bio->bi_opf &= ~REQ_HIPRI; if (!(bio->bi_opf & REQ_HIPRI)) bio_clear_flag(bio, BIO_PERCPU_CACHE); I realise the only BIO_PERCPU_CACHE user in this series never sets it without REQ_HIPRI, but it looks like a problem waiting to happen if nothing enforces this pairing: someone could set the CACHE flag on a QUEUE_FLAG_POLL enabled queue without setting HIPRI and get the wrong bio_put() action.