blk-mq: fix race in IO start accounting

Commit c6d600c6 opened up a small race where we could attempt to
account IO completion on a request, racing with IO start accounting.
Fix this up by ensuring that we've accounted for IO start before
inserting the request.

Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 9f07a266f7ab1e052cd187558fb1484114bd5ae4..526feee31bffdc9d663438bb84a757793c38fbd6 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1088,17 +1088,15 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
        }
 
        if (!(hctx->flags & BLK_MQ_F_SHOULD_MERGE)) {
-               init_request_from_bio(rq, bio);
-
+               blk_mq_bio_to_request(rq, bio);
                spin_lock(&ctx->lock);
 insert_rq:
                __blk_mq_insert_request(hctx, rq, false);
                spin_unlock(&ctx->lock);
-               blk_account_io_start(rq, 1);
        } else {
                spin_lock(&ctx->lock);
                if (!blk_mq_attempt_merge(q, ctx, bio)) {
-                       init_request_from_bio(rq, bio);
+                       blk_mq_bio_to_request(rq, bio);
                        goto insert_rq;
                }