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authorJianchao Wang <jianchao.w.wang@oracle.com>2019-02-12 09:56:25 +0800
committerJens Axboe <axboe@kernel.dk>2019-02-11 19:51:52 -0700
commitaef1897cd36dcf5e296f1d2bae7e0d268561b685 (patch)
tree4812066877528cf64a626af166ba0da0fb59e682 /block
parent2698484178ca5cbfdde189b1d8809e1528f82a10 (diff)
downloadlinux-stericsson-aef1897cd36dcf5e296f1d2bae7e0d268561b685.tar.gz
blk-mq: insert rq with DONTPREP to hctx dispatch list when requeue
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 <axboe@kernel.dk> Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
-rw-r--r--block/blk-mq.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 8f5b533764ca..9437a5eb07cf 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -737,12 +737,20 @@ 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)) {