This is a note to let you know that I've just added the patch titled
virtio-blk: Fix hot-unplug race in remove method
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
virtio-blk-fix-hot-unplug-race-in-remove-method.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From e5000b33460e5008a3a189dc2107d274d8096eff Mon Sep 17 00:00:00 2001
From: Asias He <asias@xxxxxxxxxx>
Date: Fri, 4 May 2012 20:22:04 +0800
Subject: virtio-blk: Fix hot-unplug race in remove method
From: Asias He <asias@xxxxxxxxxx>
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 <asias@xxxxxxxxxx>
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Cc: Yijing Wang <wangyijing@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/block/virtio_blk.c | 11 +++++++++++
1 file changed, 11 insertions(+)
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -573,6 +573,8 @@ static void __devexit virtblk_remove(str
{
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);
@@ -585,6 +587,15 @@ static void __devexit virtblk_remove(str
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);
Patches currently in stable-queue which might be from asias@xxxxxxxxxx are
queue-3.4/virtio-blk-fix-hot-unplug-race-in-remove-method.patch
queue-3.4/virtio-blk-call-del_gendisk-before-disable-guest-kick.patch
queue-3.4/virtio_blk-drop-unused-request-tracking-list.patch
queue-3.4/virtio-blk-reset-device-after-blk_cleanup_queue.patch
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