From mboxrd@z Thu Jan 1 00:00:00 1970 From: Asias He Subject: [PATCH v3] virtio-blk: Fix hot-unplug race in remove method Date: Fri, 4 May 2012 20:22:04 +0800 Message-ID: <1336134124-14744-1-git-send-email-asias@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: virtualization@lists.linux-foundation.org, Rusty Russell , "Michael S. Tsirkin" Cc: kvm@vger.kernel.org List-Id: virtualization@lists.linuxfoundation.org If we reset the virtio-blk device before the requests already dispatched to the virtio-blk driver from the block layer are finised, we will stuck in blk_cleanup_queue() and the remove will fail. blk_cleanup_queue() calls blk_drain_queue() to drain all requests queued before DEAD marking. However it will never success if the device is already stopped. We'll have q->in_flight[] > 0, so the drain will not finish. How to reproduce the race: 1. hot-plug a virtio-blk device 2. keep reading/writing the device in guest 3. hot-unplug while the device is busy serving I/O Test: ~1000 rounds of hot-plug/hot-unplug test passed with this patch. Changes in v3: - Drop blk_abort_queue and blk_abort_request - Use __blk_end_request_all to complete request dispatched to driver Changes in v2: - Drop req_in_flight - Use virtqueue_detach_unused_buf to get request dispatched to driver Signed-off-by: Asias He --- drivers/block/virtio_blk.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c index 72fe55d..693187d 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -576,6 +576,8 @@ 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); @@ -588,6 +590,15 @@ static void __devexit virtblk_remove(struct virtio_device *vdev) flush_work(&vblk->config_work); del_gendisk(vblk->disk); + + /* 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); -- 1.7.10.1