On Tue, Nov 19 2013, Jens Axboe wrote:
> > Looks like a race condition, below works for me, please try.
> >
> >
> > Subject: virtio_blk: fix race condition
> >
> > virtqueue_kick() isn't multi-thread safe.
> >
> > Signed-off-by: Shaohua Li <s...@fusionio.com>
> >
> > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> > index 588479d..f353959 100644
> > --- a/drivers/block/virtio_blk.c
> > +++ b/drivers/block/virtio_blk.c
> > @@ -204,10 +204,11 @@ static int virtio_queue_rq(struct blk_mq_hw_ctx
> > *hctx, struct request *req)
> > virtqueue_kick(vblk->vq);
> > return BLK_MQ_RQ_QUEUE_BUSY;
> > }
> > - spin_unlock_irqrestore(&vblk->vq_lock, flags);
> >
> > if (last)
> > virtqueue_kick(vblk->vq);
> > + spin_unlock_irqrestore(&vblk->vq_lock, flags);
> > +
> > return BLK_MQ_RQ_QUEUE_OK;
> > }
>
> Just stumbled on that too. You need one more, btw, for the sg failure
> case:
>
>
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 588479d58f52..6a680d4de7f1 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -199,15 +199,16 @@ 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);
> - virtqueue_kick(vblk->vq);
> return BLK_MQ_RQ_QUEUE_BUSY;
> }
> - spin_unlock_irqrestore(&vblk->vq_lock, flags);
>
> if (last)
> virtqueue_kick(vblk->vq);
> +
> + spin_unlock_irqrestore(&vblk->vq_lock, flags);
> return BLK_MQ_RQ_QUEUE_OK;
> }
Tested successfully here too. Dave, please give it a go, looks like this
should fix it up for you. Committed here:
http://git.kernel.dk/?p=linux-block.git;a=commit;h=f02b9ac35a47dff745c7637fbc095f01cc03646e
and will send it upstream today, so we can avoid having an -rc1 with a
broken virtio-blk.
--
Jens Axboe
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