[Qemu-devel] [PATCH v3 2/2] virtio-blk: Use blk_drain() to drain IO requests

[Alexander Yarygin <yarygin@linux.vnet.ibm.com>]

Each call of the virtio_blk_reset() function calls blk_drain_all(),
which works for all existing BlockDriverStates, while draining only
one is needed.

This patch replaces blk_drain_all() by blk_drain() in
virtio_blk_reset(). virtio_blk_data_plane_stop() should be called
after draining because it restores vblk->complete_request.

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
---
 hw/block/virtio-blk.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index e6afe97..d8a906f 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -651,16 +651,21 @@ static void virtio_blk_dma_restart_cb(void *opaque, int running,
 static void virtio_blk_reset(VirtIODevice *vdev)
 {
     VirtIOBlock *s = VIRTIO_BLK(vdev);
-
-    if (s->dataplane) {
-        virtio_blk_data_plane_stop(s->dataplane);
-    }
+    AioContext *ctx;
 
     /*
      * This should cancel pending requests, but can't do nicely until there
      * are per-device request lists.
      */
-    blk_drain_all();
+    ctx = blk_get_aio_context(s->blk);
+    aio_context_acquire(ctx);
+    blk_drain(s->blk);
+
+    if (s->dataplane) {
+        virtio_blk_data_plane_stop(s->dataplane);
+    }
+    aio_context_release(ctx);
+
     blk_set_enable_write_cache(s->blk, s->original_wce);
 }
 
-- 
1.9.1