From 86c15b51f390cfb72d4d9fe7cef9d5dbb828d919 Mon Sep 17 00:00:00 2001 From: Jianchao Wang Date: Tue, 12 Feb 2019 09:56:25 +0800 Subject: [PATCH] blk-mq: insert rq with DONTPREP to hctx dispatch list when requeue [ Upstream commit aef1897cd36dcf5e296f1d2bae7e0d268561b685 ] When requeue, if RQF_DONTPREP, rq has contained some driver specific data, so insert it to hctx dispatch list to avoid any merge. Take scsi as example, here is the trace event log (no io scheduler, because RQF_STARTED would prevent merging), kworker/0:1H-339 [000] ...1 2037.209289: block_rq_insert: 8,0 R 4096 () 32768 + 8 [kworker/0:1H] scsi_inert_test-1987 [000] .... 2037.220465: block_bio_queue: 8,0 R 32776 + 8 [scsi_inert_test] scsi_inert_test-1987 [000] ...2 2037.220466: block_bio_backmerge: 8,0 R 32776 + 8 [scsi_inert_test] kworker/0:1H-339 [000] .... 2047.220913: block_rq_issue: 8,0 R 8192 () 32768 + 16 [kworker/0:1H] scsi_inert_test-1996 [000] ..s1 2047.221007: block_rq_complete: 8,0 R () 32768 + 8 [0] scsi_inert_test-1996 [000] .Ns1 2047.221045: block_rq_requeue: 8,0 R () 32776 + 8 [0] kworker/0:1H-339 [000] ...1 2047.221054: block_rq_insert: 8,0 R 4096 () 32776 + 8 [kworker/0:1H] kworker/0:1H-339 [000] ...1 2047.221056: block_rq_issue: 8,0 R 4096 () 32776 + 8 [kworker/0:1H] scsi_inert_test-1986 [000] ..s1 2047.221119: block_rq_complete: 8,0 R () 32776 + 8 [0] (32768 + 8) was requeued by scsi_queue_insert and had RQF_DONTPREP. Then it was merged with (32776 + 8) and issued. Due to RQF_DONTPREP, the sdb only contained the part of (32768 + 8), then only that part was completed. The lucky thing was that scsi_io_completion detected it and requeued the remaining part. So we didn't get corrupted data. However, the requeue of (32776 + 8) is not expected. Suggested-by: Jens Axboe Signed-off-by: Jianchao Wang Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin Signed-off-by: Yang Yingliang --- block/blk-mq.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 8122359fa429..5949ba8aca03 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -701,12 +701,20 @@ static void blk_mq_requeue_work(struct work_struct *work) spin_unlock_irq(&q->requeue_lock); list_for_each_entry_safe(rq, next, &rq_list, queuelist) { - if (!(rq->rq_flags & RQF_SOFTBARRIER)) + if (!(rq->rq_flags & (RQF_SOFTBARRIER | RQF_DONTPREP))) continue; rq->rq_flags &= ~RQF_SOFTBARRIER; list_del_init(&rq->queuelist); - blk_mq_sched_insert_request(rq, true, false, false); + /* + * If RQF_DONTPREP, rq has contained some driver specific + * data, so insert it to hctx dispatch list to avoid any + * merge. + */ + if (rq->rq_flags & RQF_DONTPREP) + blk_mq_request_bypass_insert(rq, false); + else + blk_mq_sched_insert_request(rq, true, false, false); } while (!list_empty(&rq_list)) { -- GitLab