rbd: support reading parent page data

Currently, rbd_img_parent_read() assumes the incoming object request
contains bio data.  But if a layered image is part of a multi-layer
stack of images it will result in read requests of page data to parent
images.

Fortunately, it's not hard to add support for page data.

This resolves:
    http://tracker.ceph.com/issues/4939

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 15ac2a54d4f3..2a0e9b81be48 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -2574,7 +2574,7 @@ static void rbd_img_parent_read(struct rbd_obj_request *obj_request)
         rbd_assert(obj_request_img_data_test(obj_request));
         rbd_assert(obj_request->img_request != NULL);
         rbd_assert(obj_request->result == (s32) -ENOENT);
-        rbd_assert(obj_request->type == OBJ_REQUEST_BIO);
+        rbd_assert(obj_request_type_valid(obj_request->type));
 
         rbd_dev = obj_request->img_request->rbd_dev;
         rbd_assert(rbd_dev->parent != NULL);
@@ -2590,8 +2590,12 @@ static void rbd_img_parent_read(struct rbd_obj_request *obj_request)
         rbd_obj_request_get(obj_request);
         img_request->obj_request = obj_request;
 
-        result = rbd_img_request_fill(img_request, OBJ_REQUEST_BIO,
-                                        obj_request->bio_list);
+        if (obj_request->type == OBJ_REQUEST_BIO)
+                result = rbd_img_request_fill(img_request, OBJ_REQUEST_BIO,
+                                                obj_request->bio_list);
+        else
+                result = rbd_img_request_fill(img_request, OBJ_REQUEST_PAGES,
+                                                obj_request->pages);
         if (result)
                 goto out_err;