[Qemu-devel] [PATCH v2 6/7] scsi: Introduce scsi_req_cancel_async

[Fam Zheng <famz@redhat.com>]

Devices will call this function to start an asynchronous cancellation. The
bus->info->cancel will be called after the request is canceled.

Devices will probably need to track a separate TMF request that triggers this
cancellation, and wait until the cancellation is done before completing it. So
we store a notifier list in SCSIRequest and in scsi_req_canceled we notify them.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 hw/scsi/scsi-bus.c     | 31 ++++++++++++++++++++++++++++---
 include/hw/scsi/scsi.h |  3 +++
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c
index fca4a9e..c1b05a1 100644
--- a/hw/scsi/scsi-bus.c
+++ b/hw/scsi/scsi-bus.c
@@ -553,9 +553,10 @@ SCSIRequest *scsi_req_alloc(const SCSIReqOps *reqops, SCSIDevice *d,
     BusState *qbus = BUS(bus);
     const int memset_off = offsetof(SCSIRequest, sense)
                            + sizeof(req->sense);
+    size_t reqops_size = reqops ? reqops->size : sizeof(SCSIRequest);
 
-    req = g_slice_alloc(reqops->size);
-    memset((uint8_t *)req + memset_off, 0, reqops->size - memset_off);
+    req = g_slice_alloc(reqops_size);
+    memset((uint8_t *)req + memset_off, 0, reqops_size - memset_off);
     req->refcount = 1;
     req->bus = bus;
     req->dev = d;
@@ -566,6 +567,7 @@ SCSIRequest *scsi_req_alloc(const SCSIReqOps *reqops, SCSIDevice *d,
     req->ops = reqops;
     object_ref(OBJECT(d));
     object_ref(OBJECT(qbus->parent));
+    notifier_list_init(&req->cancel_notifiers);
     trace_scsi_req_alloc(req->dev->id, req->lun, req->tag);
     return req;
 }
@@ -1600,7 +1602,7 @@ void scsi_req_unref(SCSIRequest *req)
         if (bus->info->free_request && req->hba_private) {
             bus->info->free_request(bus, req->hba_private);
         }
-        if (req->ops->free_req) {
+        if (req->ops && req->ops->free_req) {
             req->ops->free_req(req);
         }
         object_unref(OBJECT(req->dev));
@@ -1725,9 +1727,32 @@ void scsi_req_canceled(SCSIRequest *req)
     if (req->bus->info->cancel) {
         req->bus->info->cancel(req);
     }
+    notifier_list_notify(&req->cancel_notifiers, req);
     scsi_req_unref(req);
 }
 
+/* Cancel @req asynchronously.
+ * @tmf_req is added to @req's cancellation dependency list, the bus will be
+ * notified with @tmf_req when all the requests it depends on are canceled.
+ *
+ * @red:     The request to cancel.
+ * @tmf_req: The tmf request which cancels @req.
+ * */
+void scsi_req_cancel_async(SCSIRequest *req, Notifier *notifier)
+{
+    trace_scsi_req_cancel(req->dev->id, req->lun, req->tag);
+    notifier_list_add(&req->cancel_notifiers, notifier);
+    if (req->io_canceled) {
+        return;
+    }
+    scsi_req_ref(req);
+    scsi_req_dequeue(req);
+    req->io_canceled = true;
+    if (req->aiocb) {
+        bdrv_aio_cancel_async(req->aiocb);
+    }
+}
+
 void scsi_req_cancel(SCSIRequest *req)
 {
     trace_scsi_req_cancel(req->dev->id, req->lun, req->tag);
diff --git a/include/hw/scsi/scsi.h b/include/hw/scsi/scsi.h
index 0fa2a8a..6a051df 100644
--- a/include/hw/scsi/scsi.h
+++ b/include/hw/scsi/scsi.h
@@ -5,6 +5,7 @@
 #include "block/block.h"
 #include "hw/block/block.h"
 #include "sysemu/sysemu.h"
+#include "qemu/notify.h"
 
 #define MAX_SCSI_DEVS	255
 
@@ -53,6 +54,7 @@ struct SCSIRequest {
     void              *hba_private;
     size_t            resid;
     SCSICommand       cmd;
+    NotifierList      cancel_notifiers;
 
     /* Note:
      * - fields before sense are initialized by scsi_req_alloc;
@@ -267,6 +269,7 @@ int scsi_req_get_sense(SCSIRequest *req, uint8_t *buf, int len);
 void scsi_req_abort(SCSIRequest *req, int status);
 void scsi_req_canceled(SCSIRequest *req);
 void scsi_req_cancel(SCSIRequest *req);
+void scsi_req_cancel_async(SCSIRequest *req, Notifier *notifier);
 void scsi_req_retry(SCSIRequest *req);
 void scsi_device_purge_requests(SCSIDevice *sdev, SCSISense sense);
 void scsi_device_set_ua(SCSIDevice *sdev, SCSISense sense);
-- 
1.9.3