scsi: Unify request unref in scsi_req_cancel

Before, scsi_req_cancel will take ownership of the canceled request and unref
it. We did this because we didn't know whether AIO CB will be called or not
during the cancelling, so we set the io_canceled flag before calling it, and
skip unref in the potentially called callbacks, which is not very nice.

Now, bdrv_aio_cancel has a stricter contract that the completion callbacks are
always called, so we can remove the checks of req->io_canceled and just unref
it in callbacks.

It will also make implementing asynchronous cancellation easier.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 2 insertions, 11 deletions

diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c
index 2a73a43d1d..e92b418933 100644
--- a/hw/scsi/scsi-generic.c
+++ b/hw/scsi/scsi-generic.c
@@ -137,9 +137,7 @@ static void scsi_command_complete(void *opaque, int ret)
 
     scsi_req_complete(&r->req, status);
 done:
-    if (!r->req.io_canceled) {
-        scsi_req_unref(&r->req);
-    }
+    scsi_req_unref(&r->req);
 }
 
 /* Cancel a pending data transfer.  */
@@ -150,11 +148,6 @@ static void scsi_cancel_io(SCSIRequest *req)
     DPRINTF("Cancel tag=0x%x\n", req->tag);
     if (r->req.aiocb) {
         bdrv_aio_cancel(r->req.aiocb);
-
-        /* This reference was left in by scsi_*_data.  We take ownership of
-         * it independent of whether bdrv_aio_cancel completes the request
-         * or not.  */
-        scsi_req_unref(&r->req);
     }
     r->req.aiocb = NULL;
 }
@@ -214,9 +207,7 @@ static void scsi_read_complete(void * opaque, int ret)
         bdrv_set_guest_block_size(s->conf.bs, s->blocksize);
 
         scsi_req_data(&r->req, len);
-        if (!r->req.io_canceled) {
-            scsi_req_unref(&r->req);
-        }
+        scsi_req_unref(&r->req);
     }
 }