rbd: make discard trigger copy-on-write

Discard requests are a form of write, so they should go through the
same process as plain write requests and trigger copy-on-write for
layered images.

Signed-off-by: Josh Durgin <josh.durgin@inktank.com>

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 835a96a..6fb93cd 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2851,7 +2851,8 @@ static bool img_obj_request_simple(struct rbd_obj_request *obj_request)
        rbd_dev = img_request->rbd_dev;
 
        /* Reads */
-       if (!img_request_write_test(img_request))
+       if (!img_request_write_test(img_request) &&
+           !img_request_discard_test(img_request))
                return true;
 
        /* Non-layered writes */