From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: Re: [PATCH 36/51] writeback: implement bdi_for_each_wb() Date: Fri, 3 Jul 2015 14:26:27 +0200 Message-ID: <20150703122627.GK23329@quack.suse.cz> References: <1432329245-5844-1-git-send-email-tj@kernel.org> <1432329245-5844-37-git-send-email-tj@kernel.org> <20150701072757.GW7252@quack.suse.cz> <20150702022226.GH26440@mtj.duckdns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, mhocko-AlSwsSmVLrQ@public.gmane.org, clm-b10kYP2dOMg@public.gmane.org, fengguang.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org, gthelen-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, khlebnikov-XoJtRXgx1JseBXzfvpsJ4g@public.gmane.org To: Tejun Heo Return-path: Content-Disposition: inline In-Reply-To: <20150702022226.GH26440-qYNAdHglDFBN0TnZuCh8vA@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org On Wed 01-07-15 22:22:26, Tejun Heo wrote: > On Wed, Jul 01, 2015 at 09:27:57AM +0200, Jan Kara wrote: > > > +#define bdi_for_each_wb(wb_cur, bdi, iter, start_blkcg_id) \ > > > + for ((iter)->next_id = (start_blkcg_id); \ > > > + ({ (wb_cur) = !(iter)->next_id++ ? &(bdi)->wb : NULL; }); ) > > > + > > > > This looks quite confusing. Won't it be easier to understand as: > > > > struct wb_iter { > > } __attribute__ ((unused)); > > > > #define bdi_for_each_wb(wb_cur, bdi, iter, start_blkcg_id) \ > > if (((wb_cur) = (!start_blkcg_id ? &(bdi)->wb : NULL))) > > But then break or continue wouldn't work as expected. It can get > really confusing when it's wrapped by an outer loop. That's a good point. Thanks for explanation. Maybe add a comment like: /* * We use use this seemingly complicated 'for' loop so that 'break' and * 'continue' continue to work as expected. */ Honza -- Jan Kara SUSE Labs, CR