From 08d383a74948b43eb6e96c86153e63cbf276f1fa Mon Sep 17 00:00:00 2001 From: Paolo Valente Date: Wed, 7 Aug 2019 16:17:53 +0200 Subject: [PATCH] block, bfq: reset last_completed_rq_bfqq if the pointed queue is freed Since commit 13a857a4c4e8 ("block, bfq: detect wakers and unconditionally inject their I/O"), BFQ stores, in a per-device pointer last_completed_rq_bfqq, the last bfq_queue that had an I/O request completed. If some bfq_queue receives new I/O right after the last request of last_completed_rq_bfqq has been completed, then last_completed_rq_bfqq may be a waker bfq_queue. But if the bfq_queue last_completed_rq_bfqq points to is freed, then last_completed_rq_bfqq becomes a dangling reference. This commit resets last_completed_rq_bfqq if the pointed bfq_queue is freed. Fixes: 13a857a4c4e8 ("block, bfq: detect wakers and unconditionally inject their I/O") Reported-by: Douglas Anderson Tested-by: Douglas Anderson Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe --- block/bfq-iosched.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 586fcfe227ea..b2009650afc2 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -1924,12 +1924,13 @@ static void bfq_add_request(struct request *rq) * confirmed no later than during the next * I/O-plugging interval for bfqq. */ - if (!bfq_bfqq_has_short_ttime(bfqq) && + if (bfqd->last_completed_rq_bfqq && + !bfq_bfqq_has_short_ttime(bfqq) && ktime_get_ns() - bfqd->last_completion < 200 * NSEC_PER_USEC) { if (bfqd->last_completed_rq_bfqq != bfqq && - bfqd->last_completed_rq_bfqq != - bfqq->waker_bfqq) { + bfqd->last_completed_rq_bfqq != + bfqq->waker_bfqq) { /* * First synchronization detected with * a candidate waker queue, or with a @@ -4808,6 +4809,9 @@ void bfq_put_queue(struct bfq_queue *bfqq) bfqq->bfqd->burst_size--; } + if (bfqq->bfqd && bfqq->bfqd->last_completed_rq_bfqq == bfqq) + bfqq->bfqd->last_completed_rq_bfqq = NULL; + kmem_cache_free(bfq_pool, bfqq); #ifdef CONFIG_BFQ_GROUP_IOSCHED bfqg_and_blkg_put(bfqg); -- 2.30.2