Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D532CC54E94 for ; Thu, 26 Jan 2023 16:19:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232618AbjAZQTK (ORCPT ); Thu, 26 Jan 2023 11:19:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56430 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232646AbjAZQSo (ORCPT ); Thu, 26 Jan 2023 11:18:44 -0500 Received: from mail-yb1-xb32.google.com (mail-yb1-xb32.google.com [IPv6:2607:f8b0:4864:20::b32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 620F5233FD for ; Thu, 26 Jan 2023 08:18:43 -0800 (PST) Received: by mail-yb1-xb32.google.com with SMTP id c124so2555822ybb.13 for ; Thu, 26 Jan 2023 08:18:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=vvEyqxPpR8M4BC65XVopg/XEu9SCivMiAr3QBDUWiyU=; b=H348+fayL/o7ZK4OMOl0X4WP2eMya1R6g3s71mVa0DA8XCsYAD7Mno2OaEE7NA0CmO e4033coOL787sHvi/S6s9OFvGkRHoLaUuJ1duFsKOvl5kj/wYF8+5cRX76ijn0+r9mVN /MK6vYc4x8jCg28wjYXYjcmydOgZp19VGDCnfGGlA3w2bC3Yw6+bgXPCcc6kwlaa/Dld Xkvgt3oautRKkhJGYhlwnO6TvcpaegDMiJu4G7chvMyMJzFUHGEi5AWj6fisELCIR8Mt LiDJG1ULptGXP+W67GIwNcq68sjgGTmxbYOeP0BP5KnuDIfe/tA0SCD/oII/g1WHFURW dp6w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=vvEyqxPpR8M4BC65XVopg/XEu9SCivMiAr3QBDUWiyU=; b=NrKyNLH4tQpLBbNMBDAohDhcLS/MKSl/dj/ZQyYb4vpdJI4RVu7yqn35TWFvcDJko7 zP5i5ctb+FXJLx1da/WUmxC4EzWWOEMZM4KrwIk3HNXlVnoPBFpoopscqdIC7a3TWcUM Owg3j+XDSrUlQz7Ku5uexiNMrxhmm12Pzo4TntFKWgI+M1pzmu6FvPdxcQTaNzbSW41i 4VQsdQkkmkPxfEsRSgZUDEcGKTIGBdliWRNj90d4X8XHrb1C5Dl6AZX+2mvi3ulng/KF DVoNibj3tYImX6m4r4JolauiaDwQ7XdLoGAvHLMEY9A4ICwYfFMBG127frU6dXgag82Y 3PZA== X-Gm-Message-State: AO0yUKXkiM2a+ZXbyl2QkODOW4xF/7sYvIgqHfsxXizVY/N5t2JMzd1V H86LVmM41ZJwfkxaKV7h8PHGTXNfrhgtKBro7BUg/w== X-Google-Smtp-Source: AK7set9P+5mtUtKJMZFiPeuyZhPr8TwEdg7FU3uDJVhz4F2UDpdSR6q0zVgkPPrpoaJxmCX2P+Pz2XDq0fuB0xLwifk= X-Received: by 2002:a25:6811:0:b0:80b:c92b:ed7c with SMTP id d17-20020a256811000000b0080bc92bed7cmr466120ybc.593.1674749922312; Thu, 26 Jan 2023 08:18:42 -0800 (PST) MIME-Version: 1.0 References: <20230125233554.153109-1-surenb@google.com> <20230125233554.153109-7-surenb@google.com> <20230126154740.j3a3lu4x557c56yi@techsingularity.net> In-Reply-To: <20230126154740.j3a3lu4x557c56yi@techsingularity.net> From: Suren Baghdasaryan Date: Thu, 26 Jan 2023 08:18:31 -0800 Message-ID: Subject: Re: [PATCH v3 6/7] mm: introduce mod_vm_flags_nolock and use it in untrack_pfn To: Mel Gorman Cc: akpm@linux-foundation.org, michel@lespinasse.org, jglisse@google.com, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, peterz@infradead.org, ldufour@linux.ibm.com, paulmck@kernel.org, mingo@redhat.com, will@kernel.org, luto@kernel.org, songliubraving@fb.com, peterx@redhat.com, david@redhat.com, dhowells@redhat.com, hughd@google.com, bigeasy@linutronix.de, kent.overstreet@linux.dev, punit.agrawal@bytedance.com, lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, jannh@google.com, shakeelb@google.com, tatashin@google.com, edumazet@google.com, gthelen@google.com, gurua@google.com, arjunroy@google.com, soheil@google.com, hughlynch@google.com, leewalsh@google.com, posk@google.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 26, 2023 at 7:47 AM Mel Gorman wrote: > > On Wed, Jan 25, 2023 at 03:35:53PM -0800, Suren Baghdasaryan wrote: > > In cases when VMA flags are modified after VMA was isolated and mmap_lock > > was downgraded, flags modifications would result in an assertion because > > mmap write lock is not held. > > Add note that it's also used during exit when the locking of the VMAs > becomes irrelevant (mm users is 0, should be no VMA modifications taking > place other than zap). Ack. > > The typical naming pattern when a caller either knows it holds the necessary > lock or knows it does not matter is __mod_vm_flags() Ok. It sounds less explicit but plenty of examples, so I'm fine with such rename. Will apply in the next version. > > > Introduce mod_vm_flags_nolock to be used in such situation, when VMA is > > not part of VMA tree and locking it is not required. > > Instead of such situations, describe in as "used when the caller takes > responsibility for the required locking". Ack. > > > Pass a hint to untrack_pfn to conditionally use mod_vm_flags_nolock for > > flags modification and to avoid assertion. > > > > Signed-off-by: Suren Baghdasaryan > > Patch itself looks ok. It strays close to being "conditional locking" > though which might attract some complaints. The description seems to accurately describe what's done here but I'm open to better suggestions. Thanks! > > -- > Mel Gorman > SUSE Labs