From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9BF12C3A59C for ; Fri, 16 Aug 2019 15:45:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7D9ED206C2 for ; Fri, 16 Aug 2019 15:45:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727364AbfHPPpm (ORCPT ); Fri, 16 Aug 2019 11:45:42 -0400 Received: from mx2.suse.de ([195.135.220.15]:60788 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727345AbfHPPpm (ORCPT ); Fri, 16 Aug 2019 11:45:42 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id E8AACAE1C; Fri, 16 Aug 2019 15:45:37 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 3EB341E4009; Fri, 16 Aug 2019 17:45:37 +0200 (CEST) Date: Fri, 16 Aug 2019 17:45:37 +0200 From: Jan Kara To: Tejun Heo Cc: axboe@kernel.dk, jack@suse.cz, hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, guro@fb.com, akpm@linux-foundation.org Subject: Re: [PATCH 3/5] writeback: Separate out wb_get_lookup() from wb_get_create() Message-ID: <20190816154537.GG3041@quack2.suse.cz> References: <20190815195619.GA2263813@devbig004.ftw2.facebook.com> <20190815195823.GD2263813@devbig004.ftw2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190815195823.GD2263813@devbig004.ftw2.facebook.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Thu 15-08-19 12:58:23, Tejun Heo wrote: > Separate out wb_get_lookup() which doesn't try to create one if there > isn't already one from wb_get_create(). This will be used by later > patches. > > Signed-off-by: Tejun Heo Looks good to me. You can add: Reviewed-by: Jan Kara Honza > --- > include/linux/backing-dev.h | 2 + > mm/backing-dev.c | 55 +++++++++++++++++++++++++++++--------------- > 2 files changed, 39 insertions(+), 18 deletions(-) > > --- a/include/linux/backing-dev.h > +++ b/include/linux/backing-dev.h > @@ -230,6 +230,8 @@ static inline int bdi_sched_wait(void *w > struct bdi_writeback_congested * > wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp); > void wb_congested_put(struct bdi_writeback_congested *congested); > +struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi, > + struct cgroup_subsys_state *memcg_css); > struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi, > struct cgroup_subsys_state *memcg_css, > gfp_t gfp); > --- a/mm/backing-dev.c > +++ b/mm/backing-dev.c > @@ -618,13 +618,12 @@ out_put: > } > > /** > - * wb_get_create - get wb for a given memcg, create if necessary > + * wb_get_lookup - get wb for a given memcg > * @bdi: target bdi > * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref) > - * @gfp: allocation mask to use > * > - * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to > - * create one. The returned wb has its refcount incremented. > + * Try to get the wb for @memcg_css on @bdi. The returned wb has its > + * refcount incremented. > * > * This function uses css_get() on @memcg_css and thus expects its refcnt > * to be positive on invocation. IOW, rcu_read_lock() protection on > @@ -641,6 +640,39 @@ out_put: > * each lookup. On mismatch, the existing wb is discarded and a new one is > * created. > */ > +struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi, > + struct cgroup_subsys_state *memcg_css) > +{ > + struct bdi_writeback *wb; > + > + if (!memcg_css->parent) > + return &bdi->wb; > + > + rcu_read_lock(); > + wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id); > + if (wb) { > + struct cgroup_subsys_state *blkcg_css; > + > + /* see whether the blkcg association has changed */ > + blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys); > + if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb))) > + wb = NULL; > + css_put(blkcg_css); > + } > + rcu_read_unlock(); > + > + return wb; > +} > + > +/** > + * wb_get_create - get wb for a given memcg, create if necessary > + * @bdi: target bdi > + * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref) > + * @gfp: allocation mask to use > + * > + * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to > + * create one. See wb_get_lookup() for more details. > + */ > struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi, > struct cgroup_subsys_state *memcg_css, > gfp_t gfp) > @@ -653,20 +685,7 @@ struct bdi_writeback *wb_get_create(stru > return &bdi->wb; > > do { > - rcu_read_lock(); > - wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id); > - if (wb) { > - struct cgroup_subsys_state *blkcg_css; > - > - /* see whether the blkcg association has changed */ > - blkcg_css = cgroup_get_e_css(memcg_css->cgroup, > - &io_cgrp_subsys); > - if (unlikely(wb->blkcg_css != blkcg_css || > - !wb_tryget(wb))) > - wb = NULL; > - css_put(blkcg_css); > - } > - rcu_read_unlock(); > + wb = wb_get_lookup(bdi, memcg_css); > } while (!wb && !cgwb_create(bdi, memcg_css, gfp)); > > return wb; -- Jan Kara SUSE Labs, CR