rbd: skip the copyup when an entire object writing

It need to copyup the parent's content when layered writing,
but an entire object write would overwrite it, so skip it.

Signed-off-by: Guangliang Zhao <lucienchao@gmail.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 6dae658..16eb247 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2769,6 +2769,14 @@ static bool img_obj_request_simple(struct rbd_obj_request *obj_request)
        if (!obj_request_overlaps_parent(obj_request))
                return true;
 
+       /*
+        * Entire-object layered writes - we will overwrite whatever
+        * parent data there is anyway.
+        */
+       if (!obj_request->offset &&
+           obj_request->length == rbd_obj_bytes(&rbd_dev->header))
+               return true;
+
        /*
         * If the object is known to already exist, its parent data has
         * already been copied.