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Commit cf4b50af authored by Jens Axboe's avatar Jens Axboe
Browse files

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: default avatarJens Axboe <axboe@fb.com>
parent 4bb659b1

block/blk-mq.c

+2 −4
Original line number Diff line number Diff line
@@ -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;

		}