From: Ilya Dryomov Date: Tue, 6 Feb 2018 18:26:34 +0000 (+0100) Subject: rbd: create+truncate for whole-object layered discards X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=2bb1e56ec6450ce533c644c5bfa548dc34c551a0;p=openwrt%2Fstaging%2Fblogic.git rbd: create+truncate for whole-object layered discards A whole-object layered discard is implemented as a truncate rather than a delete: a dummy object is needed to prevent the CoW machinery from kicking in. However, a truncate on a non-existent object is a no-op. If the object doesn't exist in HEAD, a discard request is effectively ignored, which violates our "discard zeroes data" promise and breaks REQ_OP_WRITE_ZEROES implementation. A non-exclusive create on an existing object is also a no-op, so the fix is to do a compound create+truncate instead. Signed-off-by: Ilya Dryomov --- diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index 0aa95e08664d..fc94e2c45e28 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -1884,6 +1884,8 @@ static void __rbd_obj_setup_discard(struct rbd_obj_request *obj_req, if (rbd_obj_is_entire(obj_req)) { if (obj_req->num_img_extents) { + osd_req_op_init(obj_req->osd_req, which++, + CEPH_OSD_OP_CREATE, 0); opcode = CEPH_OSD_OP_TRUNCATE; } else { osd_req_op_init(obj_req->osd_req, which++, @@ -1917,7 +1919,10 @@ static int rbd_obj_setup_discard(struct rbd_obj_request *obj_req) if (rbd_obj_is_entire(obj_req)) { obj_req->write_state = RBD_OBJ_WRITE_FLAT; - num_osd_ops = 1; /* truncate/delete */ + if (obj_req->num_img_extents) + num_osd_ops = 2; /* create + truncate */ + else + num_osd_ops = 1; /* delete */ } else { if (obj_req->num_img_extents) { obj_req->write_state = RBD_OBJ_WRITE_GUARD;