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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7243FC433EF for ; Fri, 13 May 2022 00:39:30 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AD6AF6B0073; Thu, 12 May 2022 20:39:29 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A850C6B0075; Thu, 12 May 2022 20:39:29 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 94F2C8D0001; Thu, 12 May 2022 20:39:29 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 820086B0073 for ; Thu, 12 May 2022 20:39:29 -0400 (EDT) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 522BD20ED1 for ; Fri, 13 May 2022 00:39:29 +0000 (UTC) X-FDA: 79458861258.06.7A3AA82 Received: from mail-pf1-f176.google.com (mail-pf1-f176.google.com [209.85.210.176]) by imf18.hostedemail.com (Postfix) with ESMTP id 93DB31C00A7 for ; Fri, 13 May 2022 00:39:17 +0000 (UTC) Received: by mail-pf1-f176.google.com with SMTP id y41so6257510pfw.12 for ; Thu, 12 May 2022 17:39:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=7e6wfjAxaZjaju6D1NvWiHjOZBPRA/6UlCOIWPAz7WY=; b=ZRv1j/j2JxnIRnnea9h1mllFFPvyPfc3xrHsFntRegrnZ5gAId7c6/btd/GvncShxU GIkVxGxlHGkJ3qgFXb7meHRsF/RjTOB3Cqn4rEuZdszqt9rptreB0WOSxF8jZCOOOfzb +x17dssNHlTcWKLF1TXOTBWkLzIKnLLbV4o0n++oIn6oS6Mu/G1lUzDvi+fEMJAPzXLD LALutqYhzNf2yHhs6W6xiDlzqnUyQlmaZ+07V0kif0x43Zho6664h/U/EdSoeux0nnCv EgpA4sjlgL9wrRAF7Y2sZ2qQVd+q8nkq3ByPkjLu1MTV8svIUUjKwbnJWZVQwStR1+NX iIjA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=7e6wfjAxaZjaju6D1NvWiHjOZBPRA/6UlCOIWPAz7WY=; b=CB+iKYlwASMe5VIv6lh9TA/NJyhspRApugjTOAtoUm3wnLzrouykKDTvdsuVwNV8Lj 9zivTlJU2d3xbMDjJW5C6VwbJcHmnb7a/kC1QvxnXYYfSNBmhrgp7IDF2M6v0w7BEhj0 I5Fv5O4D7EMXtJhd3EAzwQ6jU4jVDx57jHd12eF5m+5cXbz2s5MKUTQNtM0zMlL0zm6X 5N2wjl4vRLXXJn4ZIiuR0sXOD/TACvxm9YlFAgZ+L1MVkPRyyq0Xs1htwQPUC9ga7jcm YDDkVZyng4Ng2q6fZvZaFTLR5nOjhIrjBcTWpa2SA1qPr6RP6Rl7XnuEzsNH959ts8Ta tAMA== X-Gm-Message-State: AOAM530YOo8fZd6CKKd7YWG6Gso8k4oXUMEcM6WafGJopat45ADcdzes Br/4kGJmr8PrIp116dOUeS3+3rL8pf9KoUw1N+4= X-Google-Smtp-Source: ABdhPJzaVc+5yDtomLwz2d4JcPHlxpuBxcEfqkQ2Sk82Aq5lDzUASkJNa2+8uzIMbNLgR08K7dcXvLFN8ra53YYHdAI= X-Received: by 2002:a62:1613:0:b0:510:82a9:e3bf with SMTP id 19-20020a621613000000b0051082a9e3bfmr2163573pfw.23.1652402367793; Thu, 12 May 2022 17:39:27 -0700 (PDT) MIME-Version: 1.0 References: <20220512174551.81279-1-shy828301@gmail.com> <20220512174551.81279-2-shy828301@gmail.com> <20220512163902.5e128f6dd5dd6e44afa53259@linux-foundation.org> In-Reply-To: <20220512163902.5e128f6dd5dd6e44afa53259@linux-foundation.org> From: Yang Shi Date: Thu, 12 May 2022 17:39:15 -0700 Message-ID: Subject: Re: [PATCH 2/2] mm: pvmw: check possible huge PMD map by transhuge_vma_suitable() To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, songmuchun@bytedance.com, willy@infradead.org Content-Type: multipart/alternative; boundary="00000000000028948105ded9e8cb" X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 93DB31C00A7 X-Stat-Signature: ky6k37w8a91xpb3icuu3sadg7bmh5jc9 X-Rspam-User: Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b="ZRv1j/j2"; spf=pass (imf18.hostedemail.com: domain of shy828301@gmail.com designates 209.85.210.176 as permitted sender) smtp.mailfrom=shy828301@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-HE-Tag: 1652402357-988550 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: --00000000000028948105ded9e8cb Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Andrew Morton =E4=BA=8E2022=E5=B9=B45=E6=9C=8812= =E6=97=A5 =E5=91=A8=E5=9B=9B=E4=B8=8B=E5=8D=884:39=E5=86=99=E9=81=93=EF=BC= =9A > On Thu, 12 May 2022 10:45:51 -0700 Yang Shi wrote: > > > IIUC PVMW checks if the vma is possibly huge PMD mapped by > > transparent_hugepage_active() and "pvmw->nr_pages >=3D HPAGE_PMD_NR". > > > > Actually pvmw->nr_pages is returned by compound_nr() or > > folio_nr_pages(), so the page should be THP as long as "pvmw->nr_pages > > >=3D HPAGE_PMD_NR". And it is guaranteed THP is allocated for valid VM= A > > in the first place. But it may be not PMD mapped if the VMA is file > > VMA and it is not properly aligned. The transhuge_vma_suitable() > > is used to do such check, so replace transparent_hugepage_active() to > > it, which is too heavy and overkilling. > > > > ... > > > > --- a/mm/page_vma_mapped.c > > +++ b/mm/page_vma_mapped.c > > @@ -237,13 +237,14 @@ bool page_vma_mapped_walk(struct > page_vma_mapped_walk *pvmw) > > spin_unlock(pvmw->ptl); > > pvmw->ptl =3D NULL; > > } else if (!pmd_present(pmde)) { > > + unsigned long haddr =3D pvmw->address & > HPAGE_PMD_MASK; > > This hits > > #define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; }) > > when CONFIG_TRANSPARENT_HUGEPAGE=3Dn (x86_64 allnoconfig). Thanks for catching this. I think the best way is to round the address in transhuge_vma_suitable() which is protected by the config. Will prepare v2 soon. > > --00000000000028948105ded9e8cb Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


Andrew Morton <akpm@linux-foundation.org>=E4=BA=8E2022=E5=B9=B45=E6=9C=8812=E6= =97=A5 =E5=91=A8=E5=9B=9B=E4=B8=8B=E5=8D=884:39=E5=86=99=E9=81=93=EF=BC=9A<= br>
On Thu, 12 May 2022 10:45:51 -0700 = Yang Shi <shy82= 8301@gmail.com> wrote:

> IIUC PVMW checks if the vma is possibly huge PMD mapped by
> transparent_hugepage_active() and "pvmw->nr_pages >=3D HPAG= E_PMD_NR".
>
> Actually pvmw->nr_pages is returned by compound_nr() or
> folio_nr_pages(), so the page should be THP as long as "pvmw->= nr_pages
> >=3D HPAGE_PMD_NR".=C2=A0 And it is guaranteed THP is allocate= d for valid VMA
> in the first place.=C2=A0 But it may be not PMD mapped if the VMA is f= ile
> VMA and it is not properly aligned.=C2=A0 The transhuge_vma_suitable()=
> is used to do such check, so replace transparent_hugepage_active() to<= br> > it, which is too heavy and overkilling.
>
> ...
>
> --- a/mm/page_vma_mapped.c
> +++ b/mm/page_vma_mapped.c
> @@ -237,13 +237,14 @@ bool page_vma_mapped_walk(struct page_vma_mapped= _walk *pvmw)
>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0spin_unlock(pvmw->ptl);
>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0pvmw->ptl =3D NULL;
>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0} else if (!pmd_= present(pmde)) {
> +=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0= =C2=A0unsigned long haddr =3D pvmw->address & HPAGE_PMD_MASK;

This hits

=C2=A0 =C2=A0 =C2=A0 =C2=A0 #define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; })
when CONFIG_TRANSPARENT_HUGEPAGE=3Dn (x86_64 allnoconfig).

Thanks for catching this. I think= the best way is to round the address in transhuge_vma_suitable() which is = protected by the config.

Will prepare v2 soon.



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