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, 24 insertions, 0 deletions

diff --git a/block/io.c b/block/io.c
index 7ea402352e..89d0745e95 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2825,3 +2825,27 @@ void bdrv_io_unplug(BlockDriverState *bs)
         bdrv_io_unplug(child->bs);
     }
 }
+
+void bdrv_register_buf(BlockDriverState *bs, void *host, size_t size)
+{
+    BdrvChild *child;
+
+    if (bs->drv && bs->drv->bdrv_register_buf) {
+        bs->drv->bdrv_register_buf(bs, host, size);
+    }
+    QLIST_FOREACH(child, &bs->children, next) {
+        bdrv_register_buf(child->bs, host, size);
+    }
+}
+
+void bdrv_unregister_buf(BlockDriverState *bs, void *host)
+{
+    BdrvChild *child;
+
+    if (bs->drv && bs->drv->bdrv_unregister_buf) {
+        bs->drv->bdrv_unregister_buf(bs, host);
+    }
+    QLIST_FOREACH(child, &bs->children, next) {
+        bdrv_unregister_buf(child->bs, host);
+    }
+}