block: Introduce buf register API

Allow block driver to map and unmap a buffer for later I/O, as a performance
hint.

Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20180116060901.17413-5-famz@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index baef8e7abc..f66349c2c9 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -2096,3 +2096,13 @@ static void blk_root_drained_end(BdrvChild *child)
         }
     }
 }
+
+void blk_register_buf(BlockBackend *blk, void *host, size_t size)
+{
+    bdrv_register_buf(blk_bs(blk), host, size);
+}
+
+void blk_unregister_buf(BlockBackend *blk, void *host)
+{
+    bdrv_unregister_buf(blk_bs(blk), host);
+}