From 0c29e93eae8a7f703e463c7b38ebc85d8718cae2 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Fri, 16 May 2014 23:31:21 +0800 Subject: [PATCH] virtio_blk: fix race between start and stop queue When there isn't enough vring descriptor for adding to vq, blk-mq will be put as stopped state until some of pending descriptors are completed & freed. Unfortunately, the vq's interrupt may come just before blk-mq's BLK_MQ_S_STOPPED flag is set, so the blk-mq will still be kept as stopped even though lots of descriptors are completed and freed in the interrupt handler. The worst case is that all pending descriptors are freed in the interrupt handler, and the queue is kept as stopped forever. This patch fixes the problem by starting/stopping blk-mq with holding vq_lock. Cc: Jens Axboe Cc: Rusty Russell Signed-off-by: Ming Lei Signed-off-by: Jens Axboe --- drivers/block/virtio_blk.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 7a51f065edcd..9f340fafca5c 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -147,11 +147,11 @@ static void virtblk_done(struct virtqueue *vq) if (unlikely(virtqueue_is_broken(vq))) break; } while (!virtqueue_enable_cb(vq)); - spin_unlock_irqrestore(&vblk->vq_lock, flags); /* In case queue is stopped waiting for more buffers. */ if (req_done) blk_mq_start_stopped_hw_queues(vblk->disk->queue, true); + spin_unlock_irqrestore(&vblk->vq_lock, flags); } static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req) @@ -205,8 +205,8 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req) err = __virtblk_add_req(vblk->vq, vbr, vbr->sg, num); if (err) { virtqueue_kick(vblk->vq); - spin_unlock_irqrestore(&vblk->vq_lock, flags); blk_mq_stop_hw_queue(hctx); + spin_unlock_irqrestore(&vblk->vq_lock, flags); /* Out of mem doesn't actually happen, since we fall back * to direct descriptors */ if (err == -ENOMEM || err == -ENOSPC) -- 2.34.1