There is a race condition in virtscsi_handle_event, when many device
hotplug/unplug events flush in quickly.
The scsi_remove_device in virtscsi_handle_transport_reset may trigger
the BUG_ON in scsi_target_reap, because the state is altered behind it,
probably by scsi_scan_host of another event. I'm able to reproduce it by
repeatedly plugging and unplugging a scsi disk with the same lun number.
To fix this, a single thread workqueue (local to the module) is added,
which makes the scan work serialized. With this change, the panic goes
away.
Signed-off-by: Fam Zheng <famz@xxxxxxxxxx>
---
v4: Addressing MST's comments:
Use ordered workqueue, with WQ_FREEZABLE and WQ_MEM_RECLAIM flags.
Coding style fixes.
v3: Fix spacing and destroy order. (MST)
---
drivers/scsi/virtio_scsi.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index c52bb5d..0db63b5 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -120,6 +120,7 @@ struct virtio_scsi {
static struct kmem_cache *virtscsi_cmd_cache;
static mempool_t *virtscsi_cmd_pool;
+static struct workqueue_struct *virtscsi_scan_wq;
static inline struct Scsi_Host *virtio_scsi_host(struct virtio_device *vdev)
{
@@ -404,7 +405,7 @@ static void virtscsi_complete_event(struct virtio_scsi *vscsi, void *buf)
struct virtio_scsi_event_node *event_node = buf;
if (!vscsi->stop_events)
- queue_work(system_freezable_wq, &event_node->work);
+ queue_work(virtscsi_scan_wq, &event_node->work);
}
static void virtscsi_event_done(struct virtqueue *vq)
@@ -1119,6 +1120,14 @@ static int __init init(void)
pr_err("mempool_create() for virtscsi_cmd_pool failed\n");
goto error;
}
+
+ virtscsi_scan_wq =
+ alloc_ordered_workqueue("virtscsi-scan", WQ_FREEZABLE | WQ_MEM_RECLAIM);
+ if (!virtscsi_scan_wq) {
+ pr_err("create_singlethread_workqueue() for virtscsi_scan_wq failed\n");
+ goto error;
+ }
+
ret = register_virtio_driver(&virtio_scsi_driver);
if (ret < 0)
goto error;
@@ -1126,6 +1135,8 @@ static int __init init(void)
return 0;
error:
+ if (virtscsi_scan_wq)
+ destroy_workqueue(virtscsi_scan_wq);
if (virtscsi_cmd_pool) {
mempool_destroy(virtscsi_cmd_pool);
virtscsi_cmd_pool = NULL;
@@ -1140,6 +1151,7 @@ error:
static void __exit fini(void)
{
unregister_virtio_driver(&virtio_scsi_driver);
+ destroy_workqueue(virtscsi_scan_wq);
mempool_destroy(virtscsi_cmd_pool);
kmem_cache_destroy(virtscsi_cmd_cache);
}
--
1.9.3
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