Commit b79d866c authored by Asias He's avatar Asias He Committed by Rusty Russell

virtio-blk: Fix hot-unplug race in remove method

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

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

~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: default avatarAsias He <>
Signed-off-by: default avatarRusty Russell <>
parent 90e03207
......@@ -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. */
......@@ -598,6 +600,15 @@ static void __devexit virtblk_remove(struct virtio_device *vdev)
/* 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);
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