[Qemu-devel] [PATCH 1/2] block-backend: Introduce blk_drain() and replace blk_drain_all()

[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 only one
BlockDriverState needs to be drained.

This patch introduces the blk_drain() function and replaces
blk_drain_all() on it in virtio_blk_reset().

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>
---
 block/block-backend.c          | 5 +++++
 hw/block/virtio-blk.c          | 2 +-
 include/sysemu/block-backend.h | 1 +
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index 93e46f3..aee8a12 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -700,6 +700,11 @@ int blk_flush_all(void)
     return bdrv_flush_all();
 }
 
+void blk_drain(BlockBackend *blk)
+{
+    bdrv_drain(blk->bs);
+}
+
 void blk_drain_all(void)
 {
     bdrv_drain_all();
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index e6afe97..abaca58 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -660,7 +660,7 @@ static void virtio_blk_reset(VirtIODevice *vdev)
      * This should cancel pending requests, but can't do nicely until there
      * are per-device request lists.
      */
-    blk_drain_all();
+    blk_drain(s->blk);
     blk_set_enable_write_cache(s->blk, s->original_wce);
 }
 
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index b4a4d5e..8fc960f 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -118,6 +118,7 @@ int blk_co_discard(BlockBackend *blk, int64_t sector_num, int nb_sectors);
 int blk_co_flush(BlockBackend *blk);
 int blk_flush(BlockBackend *blk);
 int blk_flush_all(void);
+void blk_drain(BlockBackend *blk);
 void blk_drain_all(void);
 BlockdevOnError blk_get_on_error(BlockBackend *blk, bool is_read);
 BlockErrorAction blk_get_error_action(BlockBackend *blk, bool is_read,
-- 
1.9.1