From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751458AbdAVOk0 (ORCPT ); Sun, 22 Jan 2017 09:40:26 -0500 Received: from mail-pf0-f195.google.com ([209.85.192.195]:36060 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750907AbdAVOkY (ORCPT ); Sun, 22 Jan 2017 09:40:24 -0500 Date: Sun, 22 Jan 2017 22:40:17 +0800 From: Geliang Tang To: Tejun Heo Cc: Andrew Morton , Michal Hocko , Jens Axboe , Johannes Weiner , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] writeback: use rb_entry() Message-ID: <20170122144017.4uqlvmzhravsrprf@ThinkPad> References: <5b23d0cb523f4719673a462ab1569ae99084337e.1483685419.git.geliangtang@gmail.com> <671275de093d93ddc7c6f77ddc0d357149691a39.1484306840.git.geliangtang@gmail.com> <20170115235431.GF14446@mtj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170115235431.GF14446@mtj.duckdns.org> User-Agent: Mutt/1.6.2-neo (2016-08-21) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jan 15, 2017 at 06:54:31PM -0500, Tejun Heo wrote: > On Fri, Jan 13, 2017 at 11:17:12PM +0800, Geliang Tang wrote: > > To make the code clearer, use rb_entry() instead of container_of() to > > deal with rbtree. > > > > Signed-off-by: Geliang Tang > > --- > > mm/backing-dev.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/mm/backing-dev.c b/mm/backing-dev.c > > index 3bfed5ab..ffb77a1 100644 > > --- a/mm/backing-dev.c > > +++ b/mm/backing-dev.c > > @@ -410,8 +410,8 @@ wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp) > > > > while (*node != NULL) { > > parent = *node; > > - congested = container_of(parent, struct bdi_writeback_congested, > > - rb_node); > > + congested = rb_entry(parent, struct bdi_writeback_congested, > > + rb_node); > > I don't get the rb_entry() macro. It's just another name for > container_of(). I have no objection to the patch but this macro is a > bit silly. > There are several *_entry macros which are defined in kernel data structures, like list_entry, hlist_entry, rb_entry, etc. Each of them is just another name for container_of. We use different *_entry so that we could identify the specific type of data structure that we are dealing with. -Geliang