[Qemu-devel] [PATCH v2] xen_disk: fix io accounting

[Olaf Hering <olaf@aepfle.de>]

bdrv_acct_done was called unconditional. But in case the ioreq has no
segments there is no matching bdrv_acct_start call. This could lead to
bogus accounting values.

Found by code inspection.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
---
v2:
  add comment /* fall through */

 hw/block/xen_disk.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
index 098f6c6..fb4ca4a 100644
--- a/hw/block/xen_disk.c
+++ b/hw/block/xen_disk.c
@@ -483,7 +483,19 @@ static void qemu_aio_complete(void *opaque, int ret)
     ioreq->status = ioreq->aio_errors ? BLKIF_RSP_ERROR : BLKIF_RSP_OKAY;
     ioreq_unmap(ioreq);
     ioreq_finish(ioreq);
-    bdrv_acct_done(ioreq->blkdev->bs, &ioreq->acct);
+    switch (ioreq->req.operation) {
+    case BLKIF_OP_WRITE:
+    case BLKIF_OP_FLUSH_DISKCACHE:
+        if (!ioreq->req.nr_segments) {
+            break;
+        }
+	/* fall through */
+    case BLKIF_OP_READ:
+        bdrv_acct_done(ioreq->blkdev->bs, &ioreq->acct);
+        break;
+    default:
+        break;
+    }
     qemu_bh_schedule(ioreq->blkdev->bh);
 }