[Qemu-devel] [PATCH 3/3] virtio-scsi: Handle TMF request cancellation asynchronously

[Fam Zheng <famz@redhat.com>]

For VIRTIO_SCSI_T_TMF_ABORT_TASK and VIRTIO_SCSI_T_TMF_ABORT_TASK_SET,
use scsi_req_cancel_async to start the cancellation. In
virtio_scsi_handle_ctrl, wait for virtio_scsi_cancel_dep_complete before
completing the request.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 hw/scsi/virtio-scsi.c | 45 ++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 38 insertions(+), 7 deletions(-)

diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index 86aba88..323140e 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -226,12 +226,27 @@ static void *virtio_scsi_load_request(QEMUFile *f, SCSIRequest *sreq)
     return req;
 }
 
-static void virtio_scsi_do_tmf(VirtIOSCSI *s, VirtIOSCSIReq *req)
+static void virtio_scsi_cancel_req(SCSIDevice *d, SCSIRequest *req,
+                                   VirtIOSCSIReq *tmf_req)
+{
+    if (!tmf_req->sreq) {
+        /* Allocate a dummy sreq in order to keep track of the
+         * dependency */
+        tmf_req->sreq = scsi_req_alloc(NULL, NULL, 0, 0, req);
+    }
+    scsi_req_cancel_async(req, tmf_req->sreq);
+}
+
+/* Return true if the request is ready to be completed and return to guest;
+ * false if the request will be completed (by some other events) later, for
+ * example in the case of async cancellation. */
+static bool virtio_scsi_do_tmf(VirtIOSCSI *s, VirtIOSCSIReq *req)
 {
     SCSIDevice *d = virtio_scsi_device_find(s, req->req.tmf.lun);
     SCSIRequest *r, *next;
     BusChild *kid;
     int target;
+    bool ret = true;
 
     /* Here VIRTIO_SCSI_S_OK means "FUNCTION COMPLETE".  */
     req->resp.tmf.response = VIRTIO_SCSI_S_OK;
@@ -264,7 +279,8 @@ static void virtio_scsi_do_tmf(VirtIOSCSI *s, VirtIOSCSIReq *req)
                  */
                 req->resp.tmf.response = VIRTIO_SCSI_S_FUNCTION_SUCCEEDED;
             } else {
-                scsi_req_cancel(r);
+                virtio_scsi_cancel_req(d, r, req);
+                ret = false;
             }
         }
         break;
@@ -299,7 +315,8 @@ static void virtio_scsi_do_tmf(VirtIOSCSI *s, VirtIOSCSIReq *req)
                     req->resp.tmf.response = VIRTIO_SCSI_S_FUNCTION_SUCCEEDED;
                     break;
                 } else {
-                    scsi_req_cancel(r);
+                    virtio_scsi_cancel_req(d, r, req);
+                    ret = false;
                 }
             }
         }
@@ -323,20 +340,22 @@ static void virtio_scsi_do_tmf(VirtIOSCSI *s, VirtIOSCSIReq *req)
         break;
     }
 
-    return;
+    return ret;
 
 incorrect_lun:
     req->resp.tmf.response = VIRTIO_SCSI_S_INCORRECT_LUN;
-    return;
+    return ret;
 
 fail:
     req->resp.tmf.response = VIRTIO_SCSI_S_BAD_TARGET;
+    return ret;
 }
 
 static void virtio_scsi_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
 {
     VirtIOSCSI *s = (VirtIOSCSI *)vdev;
     VirtIOSCSIReq *req;
+    bool should_complete = true;
 
     while ((req = virtio_scsi_pop_req(s, vq))) {
         int type;
@@ -353,7 +372,7 @@ static void virtio_scsi_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
                                       sizeof(VirtIOSCSICtrlTMFResp)) < 0) {
                 virtio_scsi_bad_req();
             } else {
-                virtio_scsi_do_tmf(s, req);
+                should_complete = virtio_scsi_do_tmf(s, req);
             }
 
         } else if (req->req.tmf.type == VIRTIO_SCSI_T_AN_QUERY ||
@@ -366,7 +385,9 @@ static void virtio_scsi_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
                 req->resp.an.response = VIRTIO_SCSI_S_OK;
             }
         }
-        virtio_scsi_complete_req(req);
+        if (should_complete) {
+            virtio_scsi_complete_req(req);
+        }
     }
 }
 
@@ -437,6 +458,15 @@ static QEMUSGList *virtio_scsi_get_sg_list(SCSIRequest *r)
     return &req->qsgl;
 }
 
+static void virtio_scsi_cancel_dep_complete(SCSIRequest *r)
+{
+    VirtIOSCSIReq *req = r->hba_private;
+
+    scsi_req_unref(req->sreq);
+    req->sreq = NULL;
+    virtio_scsi_complete_req(req);
+}
+
 static void virtio_scsi_request_cancelled(SCSIRequest *r)
 {
     VirtIOSCSIReq *req = r->hba_private;
@@ -679,6 +709,7 @@ static struct SCSIBusInfo virtio_scsi_scsi_info = {
 
     .complete = virtio_scsi_command_complete,
     .cancel = virtio_scsi_request_cancelled,
+    .cancel_dep_complete = virtio_scsi_cancel_dep_complete,
     .change = virtio_scsi_change,
     .hotplug = virtio_scsi_hotplug,
     .hot_unplug = virtio_scsi_hot_unplug,
-- 
1.9.3