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=-15.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,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 6E8C1C433DB for ; Wed, 6 Jan 2021 10:23:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1F0BC2310D for ; Wed, 6 Jan 2021 10:23:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726658AbhAFKXO (ORCPT ); Wed, 6 Jan 2021 05:23:14 -0500 Received: from relay.sw.ru ([185.231.240.75]:58152 "EHLO relay3.sw.ru" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726406AbhAFKXN (ORCPT ); Wed, 6 Jan 2021 05:23:13 -0500 Received: from [192.168.15.143] by relay3.sw.ru with esmtp (Exim 4.94) (envelope-from ) id 1kx5wT-00FcpY-3Q; Wed, 06 Jan 2021 13:21:25 +0300 Subject: Re: [v3 PATCH 05/11] mm: vmscan: use a new flag to indicate shrinker is registered To: Yang Shi , guro@fb.com, shakeelb@google.com, david@fromorbit.com, hannes@cmpxchg.org, mhocko@suse.com, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210105225817.1036378-1-shy828301@gmail.com> <20210105225817.1036378-6-shy828301@gmail.com> From: Kirill Tkhai Message-ID: Date: Wed, 6 Jan 2021 13:21:34 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20210105225817.1036378-6-shy828301@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06.01.2021 01:58, Yang Shi wrote: > Currently registered shrinker is indicated by non-NULL shrinker->nr_deferred. > This approach is fine with nr_deferred at the shrinker level, but the following > patches will move MEMCG_AWARE shrinkers' nr_deferred to memcg level, so their > shrinker->nr_deferred would always be NULL. This would prevent the shrinkers > from unregistering correctly. > > Signed-off-by: Yang Shi > --- > include/linux/shrinker.h | 7 ++++--- > mm/vmscan.c | 13 +++++++++---- > 2 files changed, 13 insertions(+), 7 deletions(-) > > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h > index 0f80123650e2..1eac79ce57d4 100644 > --- a/include/linux/shrinker.h > +++ b/include/linux/shrinker.h > @@ -79,13 +79,14 @@ struct shrinker { > #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ > > /* Flags */ > -#define SHRINKER_NUMA_AWARE (1 << 0) > -#define SHRINKER_MEMCG_AWARE (1 << 1) > +#define SHRINKER_REGISTERED (1 << 0) > +#define SHRINKER_NUMA_AWARE (1 << 1) > +#define SHRINKER_MEMCG_AWARE (1 << 2) > /* > * It just makes sense when the shrinker is also MEMCG_AWARE for now, > * non-MEMCG_AWARE shrinker should not have this flag set. > */ > -#define SHRINKER_NONSLAB (1 << 2) > +#define SHRINKER_NONSLAB (1 << 3) > > extern int prealloc_shrinker(struct shrinker *shrinker); > extern void register_shrinker_prepared(struct shrinker *shrinker); > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 8da765a85569..9761c7c27412 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -494,6 +494,7 @@ void register_shrinker_prepared(struct shrinker *shrinker) > if (shrinker->flags & SHRINKER_MEMCG_AWARE) > idr_replace(&shrinker_idr, shrinker, shrinker->id); > #endif > + shrinker->flags |= SHRINKER_REGISTERED; In case of we introduce this new flag, we should kill old flag SHRINKER_REGISTERING, which are not needed anymore (we should you the new flag instead of that). > up_write(&shrinker_rwsem); > } > > @@ -513,13 +514,17 @@ EXPORT_SYMBOL(register_shrinker); > */ > void unregister_shrinker(struct shrinker *shrinker) > { > - if (!shrinker->nr_deferred) > - return; > - if (shrinker->flags & SHRINKER_MEMCG_AWARE) > - unregister_memcg_shrinker(shrinker); > down_write(&shrinker_rwsem); I do not think there are some users which registration may race with unregistration. So, I think we should check SHRINKER_REGISTERED unlocked similar to we used to check shrinker->nr_deferred unlocked. > + if (!(shrinker->flags & SHRINKER_REGISTERED)) { > + up_write(&shrinker_rwsem); > + return; > + } > list_del(&shrinker->list); > + shrinker->flags &= ~SHRINKER_REGISTERED; > up_write(&shrinker_rwsem); > + > + if (shrinker->flags & SHRINKER_MEMCG_AWARE) > + unregister_memcg_shrinker(shrinker); > kfree(shrinker->nr_deferred); > shrinker->nr_deferred = NULL; > } >