rbd: send snapshot context with writes

jdurgin · Sage Weil · commit d2d1f17a0dad · 2013-06-27T05:55:29.000-07:00
Sending the right snapshot context with each write is required for snapshots to work. Due to the ordering of calls, the snapshot context is never set for any requests. This causes writes to the current version of the image to be reflected in all snapshots, which are supposed to be read-only. This happens because rbd_osd_req_format_write() sets the snapshot context based on obj_request->img_request. At this point, however, obj_request->img_request has not been set yet, to the snapshot context is set to NULL. Fix this by moving rbd_img_obj_request_add(), which sets obj_request->img_request, before the osd request formatting calls. This resolves: http://tracker.ceph.com/issues/5465 Reported-by: Karol Jurak <karol.jurak@gmail.com> Signed-off-by: Josh Durgin <josh.durgin@inktank.com> Reviewed-by: Sage Weil <sage@inktank.com> Reviewed-by: Alex Elder <elder@linaro.org>
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
@@ -2254,13 +2254,17 @@ static int rbd_img_request_fill(struct rbd_img_request *img_request,
 					obj_request->pages, length,
 					offset & ~PAGE_MASK, false, false);
 
+		/*
+		 * set obj_request->img_request before formatting
+		 * the osd_request so that it gets the right snapc
+		 */
+		rbd_img_obj_request_add(img_request, obj_request);
 		if (write_request)
 			rbd_osd_req_format_write(obj_request);
 		else
 			rbd_osd_req_format_read(obj_request);
 
 		obj_request->img_offset = img_offset;
-		rbd_img_obj_request_add(img_request, obj_request);
 
 		img_offset += length;
 		resid -= length;
