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>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 6dae6586a8a9..16eb247cb5fb 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2770,6 +2770,14 @@ static bool img_obj_request_simple(struct rbd_obj_request *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.
          */