From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756349Ab2IIXdb (ORCPT ); Sun, 9 Sep 2012 19:33:31 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:51178 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755831Ab2IIXQJ (ORCPT ); Sun, 9 Sep 2012 19:16:09 -0400 Message-Id: <20120909224202.366987058@decadent.org.uk> User-Agent: quilt/0.60-1 Date: Sun, 09 Sep 2012 23:43:16 +0100 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Asias He , Rusty Russell Subject: [ 86/95] virtio-blk: Fix hot-unplug race in remove method In-Reply-To: <20120909224150.641491654@decadent.org.uk> X-SA-Exim-Connect-IP: 2001:470:1f08:1539:21c:bfff:fe03:f805 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Asias He commit b79d866c8b7014a51f611a64c40546109beaf24a upstream. 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 Signed-off-by: Rusty Russell Signed-off-by: Ben Hutchings --- 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 0d39f2f..9d2223b 100644 --- a/drivers/block/virtio_blk.c +++ b/drivers/block/virtio_blk.c @@ -583,6 +583,8 @@ 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); @@ -598,6 +600,15 @@ 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);