On Sun, Jun 8, 2014 at 9:55 AM, <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> The patch below does not apply to the 3.14-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
Attachment is the backported patch for 3.14.
Thanks,
--
Ming Lei
From d1152f1cc1b1784691746bcfc18729ac4b7eb1b8 Mon Sep 17 00:00:00 2001
From: Ming Lei <tom.leiming@xxxxxxxxx>
Date: Sun, 8 Jun 2014 10:33:34 +0800
Subject: [PATCH] [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 <axboe@xxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Ming Lei <tom.leiming@xxxxxxxxx>
Cc: stable@xxxxxxxxxx v3.13+
Signed-off-by: Jens Axboe <axboe@xxxxxx>
---
backported from:
0c29e93eae8a7f703e463c7b38ebc85d8718cae2
(virtio_blk: fix race between start and stop queue)
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 b1cb3f4..6c911c8 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -144,11 +144,11 @@ 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);
+ spin_unlock_irqrestore(&vblk->vq_lock, flags);
}
static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
@@ -200,8 +200,8 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
spin_lock_irqsave(&vblk->vq_lock, flags);
if (__virtblk_add_req(vblk->vq, vbr, vbr->sg, num) < 0) {
virtqueue_kick(vblk->vq);
- spin_unlock_irqrestore(&vblk->vq_lock, flags);
blk_mq_stop_hw_queue(hctx);
+ spin_unlock_irqrestore(&vblk->vq_lock, flags);
return BLK_MQ_RQ_QUEUE_BUSY;
}
--
1.7.9.5