On Fri, May 25, 2012 at 10:34:48AM +0800, Asias He wrote: > blk_cleanup_queue() will call blk_drian_queue() to drain all the > requests before queue DEAD marking. If we reset the device before > blk_cleanup_queue() the drain would fail. > > 1) if the queue is stopped in do_virtblk_request() because device is > full, the q->request_fn() will not be called. > > blk_drain_queue() { > while(true) { > ... > if (!list_empty(&q->queue_head)) > __blk_run_queue(q) { > if (queue is not stoped) > q->request_fn() > } > ... > } > } > > Do no reset the device before blk_cleanup_queue() gives the chance to > start the queue in interrupt handler blk_done(). > > 2) In commit b79d866c8b7014a51f611a64c40546109beaf24a, We abort requests > dispatched to driver before blk_cleanup_queue(). There is a race if > requests are dispatched to driver after the abort and before the queue > DEAD mark. To fix this, instead of aborting the requests explicitly, we > can just reset the device after after blk_cleanup_queue so that the > device can complete all the requests before queue DEAD marking in the > drain process. > > Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx> > Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx> > Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx > Cc: kvm@xxxxxxxxxxxxxxx > Signed-off-by: Asias He <asias@xxxxxxxxxx> > --- > drivers/block/virtio_blk.c | 12 +----------- > 1 file changed, 1 insertion(+), 11 deletions(-) > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > index 1bed517..b4fa2d7 100644 > --- a/drivers/block/virtio_blk.c > +++ b/drivers/block/virtio_blk.c > @@ -576,8 +576,6 @@ static void __devexit virtblk_remove(struct virtio_device *vdev) > { > struct virtio_blk *vblk = vdev->priv; > int index = vblk->index; > - struct virtblk_req *vbr; > - unsigned long flags; > > /* Prevent config work handler from accessing the device. */ > mutex_lock(&vblk->config_lock); > @@ -585,21 +583,13 @@ static void __devexit virtblk_remove(struct virtio_device *vdev) > mutex_unlock(&vblk->config_lock); > > del_gendisk(vblk->disk); > + blk_cleanup_queue(vblk->disk->queue); Device is not reset here yet, so it will process some requests in parallel with blk_cleanup_queue. Is this a problem? Why not? > > /* Stop all the virtqueues. */ > vdev->config->reset(vdev); > > flush_work(&vblk->config_work); > > - /* Abort requests dispatched to driver. */ > - spin_lock_irqsave(&vblk->lock, flags); > - while ((vbr = virtqueue_detach_unused_buf(vblk->vq))) { > - __blk_end_request_all(vbr->req, -EIO); > - mempool_free(vbr, vblk->pool); > - } > - spin_unlock_irqrestore(&vblk->lock, flags); > - > - blk_cleanup_queue(vblk->disk->queue); > put_disk(vblk->disk); > mempool_destroy(vblk->pool); > vdev->config->del_vqs(vdev); > -- > 1.7.10.2 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html