blk-mq: add helper to insert requests from irq context

Both the cache flush state machine and the SCSI midlayer want to submit
requests from irq context, and the current per-request requeue_work
unfortunately causes corruption due to sharing with the csd field for
flushes.  Replace them with a per-request_queue list of requests to
be requeued.

Based on an earlier test by Ming Lei.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Ming Lei <tom.leiming@gmail.com>
Tested-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 4 insertions, 12 deletions

diff --git a/block/blk-flush.c b/block/blk-flush.c
index ec7a224d6733..ef608b35d9be 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -130,21 +130,13 @@ static void blk_flush_restore_request(struct request *rq)
         blk_clear_rq_complete(rq);
 }
 
-static void mq_flush_run(struct work_struct *work)
-{
-        struct request *rq;
-
-        rq = container_of(work, struct request, requeue_work);
-
-        memset(&rq->csd, 0, sizeof(rq->csd));
-        blk_mq_insert_request(rq, false, true, false);
-}
-
 static bool blk_flush_queue_rq(struct request *rq, bool add_front)
 {
         if (rq->q->mq_ops) {
-                INIT_WORK(&rq->requeue_work, mq_flush_run);
-                kblockd_schedule_work(&rq->requeue_work);
+                struct request_queue *q = rq->q;
+
+                blk_mq_add_to_requeue_list(rq, add_front);
+                blk_mq_kick_requeue_list(q);
                 return false;
         } else {
                 if (add_front)