rbd: restore zeroing past the overlap when reading from parent

The parent image is read only up to the overlap point, the rest of
the buffer should be zeroed.  This snuck in because as it turns out
the overlap test case has not been triggering this code path for
a while now.

Fixes: a9b67e69949d ("rbd: replace obj_req->tried_parent with obj_req->read_state")
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Jason Dillaman <dillaman@redhat.com>

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 3327192bb71f73c9e4f4500203f39d8c1de01a0a..c8fb886aebd4e9ea569203c446cf537c756026d0 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -3038,6 +3038,17 @@ again:
                }
                return true;
        case RBD_OBJ_READ_PARENT:
+               /*
+                * The parent image is read only up to the overlap -- zero-fill
+                * from the overlap to the end of the request.
+                */
+               if (!*result) {
+                       u32 obj_overlap = rbd_obj_img_extents_bytes(obj_req);
+
+                       if (obj_overlap < obj_req->ex.oe_len)
+                               rbd_obj_zero_range(obj_req, obj_overlap,
+                                           obj_req->ex.oe_len - obj_overlap);
+               }
                return true;
        default:
                BUG();