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>

diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index 9645d0194a8c16b4b0aaeef3bd0f15d4d61c11c1..2e45752da14d9b4ee4cb3ba82bd609b484ac82fa 100644 (file)
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -113,11 +113,6 @@ 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 the moment scsi_req_cancel is called, independent of whether
-         * bdrv_aio_cancel completes the request or not.  */
-        scsi_req_unref(&r->req);
     }
     r->req.aiocb = NULL;
 }
@@ -197,9 +192,7 @@ static void scsi_aio_complete(void *opaque, int ret)
     scsi_req_complete(&r->req, GOOD);
 
 done:
-    if (!r->req.io_canceled) {
-        scsi_req_unref(&r->req);
-    }
+    scsi_req_unref(&r->req);
 }
 
 static bool scsi_is_cmd_fua(SCSICommand *cmd)
@@ -246,9 +239,7 @@ static void scsi_write_do_fua(SCSIDiskReq *r)
     scsi_req_complete(&r->req, GOOD);
 
 done:
-    if (!r->req.io_canceled) {
-        scsi_req_unref(&r->req);
-    }
+    scsi_req_unref(&r->req);
 }
 
 static void scsi_dma_complete_noio(void *opaque, int ret)
@@ -280,9 +271,7 @@ static void scsi_dma_complete_noio(void *opaque, int ret)
     }
 
 done:
-    if (!r->req.io_canceled) {
-        scsi_req_unref(&r->req);
-    }
+    scsi_req_unref(&r->req);
 }
 
 static void scsi_dma_complete(void *opaque, int ret)
@@ -320,9 +309,7 @@ static void scsi_read_complete(void * opaque, int ret)
     scsi_req_data(&r->req, r->qiov.size);
 
 done:
-    if (!r->req.io_canceled) {
-        scsi_req_unref(&r->req);
-    }
+    scsi_req_unref(&r->req);
 }
 
 /* Actually issue a read to the block device.  */
@@ -363,9 +350,7 @@ static void scsi_do_read(void *opaque, int ret)
     }
 
 done:
-    if (!r->req.io_canceled) {
-        scsi_req_unref(&r->req);
-    }
+    scsi_req_unref(&r->req);
 }
 
 /* Read more data from scsi device into buffer.  */
@@ -481,9 +466,7 @@ static void scsi_write_complete(void * opaque, int ret)
     }
 
 done:
-    if (!r->req.io_canceled) {
-        scsi_req_unref(&r->req);
-    }
+    scsi_req_unref(&r->req);
 }
 
 static void scsi_write_data(SCSIRequest *req)
@@ -1582,9 +1565,7 @@ static void scsi_unmap_complete(void *opaque, int ret)
     scsi_req_complete(&r->req, GOOD);
 
 done:
-    if (!r->req.io_canceled) {
-        scsi_req_unref(&r->req);
-    }
+    scsi_req_unref(&r->req);
     g_free(data);
 }
 
@@ -1678,9 +1659,7 @@ static void scsi_write_same_complete(void *opaque, int ret)
     scsi_req_complete(&r->req, GOOD);
 
 done:
-    if (!r->req.io_canceled) {
-        scsi_req_unref(&r->req);
-    }
+    scsi_req_unref(&r->req);
     qemu_vfree(data->iov.iov_base);
     g_free(data);
 }

diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c
index 2a73a43d1d3ba6e99ce92ffd408e26d21d9642a6..e92b418933b9daaec5f0b08cac887785547a2cee 100644 (file)
--- 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);
     }
 }