blk-mq: fix racy updates of rq->errors

blk_mq_complete_request may be a no-op if the request has already
been completed by others means (e.g. a timeout or cancellation), but
currently drivers have to set rq->errors before calling
blk_mq_complete_request, which might leave us with the wrong error value.

Add an error parameter to blk_mq_complete_request so that we can
defer setting rq->errors until we known we won the race to complete the
request.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 31c0c62..2306330 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -393,14 +393,16 @@ void __blk_mq_complete_request(struct request *rq)
  *     Ends all I/O on a request. It does not handle partial completions.
  *     The actual completion happens out-of-order, through a IPI handler.
  **/
-void blk_mq_complete_request(struct request *rq)
+void blk_mq_complete_request(struct request *rq, int error)
 {
        struct request_queue *q = rq->q;
 
        if (unlikely(blk_should_fake_timeout(q)))
                return;
-       if (!blk_mark_rq_complete(rq))
+       if (!blk_mark_rq_complete(rq)) {
+               rq->errors = error;
                __blk_mq_complete_request(rq);
+       }
 }
 EXPORT_SYMBOL(blk_mq_complete_request);
 
@@ -616,10 +618,8 @@ static void blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
                 * If a request wasn't started before the queue was
                 * marked dying, kill it here or it'll go unnoticed.
                 */
-               if (unlikely(blk_queue_dying(rq->q))) {
-                       rq->errors = -EIO;
-                       blk_mq_complete_request(rq);
-               }
+               if (unlikely(blk_queue_dying(rq->q)))
+                       blk_mq_complete_request(rq, -EIO);
                return;
        }
        if (rq->cmd_flags & REQ_NO_TIMEOUT)

diff --cc drivers/block/loop.c
Simple merge

diff --cc drivers/block/null_blk.c
Simple merge

diff --cc drivers/block/nvme-core.c
Simple merge

diff --cc drivers/block/virtio_blk.c
Simple merge

diff --cc drivers/block/xen-blkfront.c
Simple merge

diff --cc drivers/scsi/scsi_lib.c
Simple merge

diff --cc include/linux/blk-mq.h
Simple merge