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
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>
---
drivers/block/virtio_blk.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 72fe55d..670c28f 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -443,7 +443,7 @@ static int __devinit virtblk_probe(struct virtio_device *vdev)
if (err)
goto out_free_vblk;
- vblk->pool = mempool_create_kmalloc_pool(1,sizeof(struct virtblk_req));
+ vblk->pool = mempool_create_kmalloc_pool(1, sizeof(struct virtblk_req));
if (!vblk->pool) {
err = -ENOMEM;
goto out_free_vq;
@@ -576,20 +576,30 @@ static void __devexit virtblk_remove(struct virtio_device *vdev)
{
struct virtio_blk *vblk = vdev->priv;
int index = vblk->index;
+ struct virtblk_req *vbr;
/* Prevent config work handler from accessing the device. */
mutex_lock(&vblk->config_lock);
vblk->config_enable = false;
mutex_unlock(&vblk->config_lock);
+ /* Abort all request on the queue. */
+ blk_abort_queue(vblk->disk->queue);
+ del_gendisk(vblk->disk);
+
/* Stop all the virtqueues. */
vdev->config->reset(vdev);
-
flush_work(&vblk->config_work);
- del_gendisk(vblk->disk);
+ /* Abort request dispatched to driver. */
+ while ((vbr = virtqueue_detach_unused_buf(vblk->vq))) {
+ blk_abort_request(vbr->req);
+ mempool_free(vbr, vblk->pool);
+ }
+
blk_cleanup_queue(vblk->disk->queue);
put_disk(vblk->disk);
+
mempool_destroy(vblk->pool);
vdev->config->del_vqs(vdev);
kfree(vblk);
--
1.7.10
--
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