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vhost-scsi: Handle vhost_vq_work_queue failures for events

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Currently, we can try to queue an event's work before the vhost_task is
created. When this happens we just drop it in vhost_scsi_do_plug before
even calling vhost_vq_work_queue. During a device shutdown we do the
same thing after vhost_scsi_clear_endpoint has cleared the backends.

In the next patches we will be able to kill the vhost_task before we
have cleared the endpoint. In that case, vhost_vq_work_queue can fail
and we will leak the event's memory. This has handle the failure by
just freeing the event. This is safe to do, because
vhost_vq_work_queue will only return failure for us when the vhost_task
is killed and so userspace will not be able to handle events if we
sent them.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Message-Id: <20240316004707.45557-2-michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Mike Christie 2024-03-15 19:46:59 -05:00 committed by Michael S. Tsirkin
parent 7b1b5c7fff
commit b1b2ce58ed
1 changed files with 12 additions and 5 deletions
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17
drivers/vhost/scsi.c
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@ -497,10 +497,8 @@ vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
vq_err(vq, "Faulted on vhost_scsi_send_event\n");
}
static void vhost_scsi_evt_work(struct vhost_work *work)
static void vhost_scsi_complete_events(struct vhost_scsi *vs, bool drop)
{
struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
vs_event_work);
struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
struct vhost_scsi_evt *evt, *t;
struct llist_node *llnode;
@ -508,12 +506,20 @@ static void vhost_scsi_evt_work(struct vhost_work *work)
mutex_lock(&vq->mutex);
llnode = llist_del_all(&vs->vs_event_list);
llist_for_each_entry_safe(evt, t, llnode, list) {
vhost_scsi_do_evt_work(vs, evt);
if (!drop)
vhost_scsi_do_evt_work(vs, evt);
vhost_scsi_free_evt(vs, evt);
}
mutex_unlock(&vq->mutex);
}
static void vhost_scsi_evt_work(struct vhost_work *work)
{
struct vhost_scsi *vs = container_of(work, struct vhost_scsi,
vs_event_work);
vhost_scsi_complete_events(vs, false);
}
static int vhost_scsi_copy_sgl_to_iov(struct vhost_scsi_cmd *cmd)
{
struct iov_iter *iter = &cmd->saved_iter;
@ -1509,7 +1515,8 @@ vhost_scsi_send_evt(struct vhost_scsi *vs, struct vhost_virtqueue *vq,
}
llist_add(&evt->list, &vs->vs_event_list);
vhost_vq_work_queue(vq, &vs->vs_event_work);
if (!vhost_vq_work_queue(vq, &vs->vs_event_work))
vhost_scsi_complete_events(vs, true);
}
static void vhost_scsi_evt_handle_kick(struct vhost_work *work)