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=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 64DB9C433FE for ; Thu, 23 Sep 2021 17:16:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4EA93610A0 for ; Thu, 23 Sep 2021 17:16:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242356AbhIWRRk (ORCPT ); Thu, 23 Sep 2021 13:17:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59210 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242474AbhIWRRb (ORCPT ); Thu, 23 Sep 2021 13:17:31 -0400 Received: from mail-ed1-x534.google.com (mail-ed1-x534.google.com [IPv6:2a00:1450:4864:20::534]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 32A7EC061574; Thu, 23 Sep 2021 10:15:59 -0700 (PDT) Received: by mail-ed1-x534.google.com with SMTP id v10so21026711edj.10; Thu, 23 Sep 2021 10:15:59 -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=UHYH6Vrz0laBG66JYJnRRiuzY/WhU/BobO0byYWnoRw=; b=XNQffNsPyyD+iqO4CgNLqqilvEBuxRZ4ZByo+ePQFgaw8IItw6RCN02BUMs4QJ1oca GeUY2dFljtG+qZM3ZV6QW+DGUo41vM544PU4TcDUz+4a2FhsT6GUvzzqbsmo0YgRbg0T JVLg20IFfpZX1CLCmMRWAnPBddvzUhFtlwank65jKj/ZS6h+hCIbR+WouCANhfRwwPJp HaXfG/J+1GijdoSu4R9XX3+tabSjdBAYWQi1Ongr8Yp4p1rAWZvspxCUEG5nn67SOklN QN3LnCSGbZ6d+fu/PdAaGFGb1M6JF2hKoiDni30WqBqBLz+3K4Q3dKAzqjDZenpDEitQ WcIw== 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=UHYH6Vrz0laBG66JYJnRRiuzY/WhU/BobO0byYWnoRw=; b=KaSEe6LR08Wc6VB7oqz8NIcU7SaaG5CDpMqHrUkFT27xuBEb/b7OjGFFANYHTNCrkv Mdy5NxnvKugKqAxu/1I/PS4I3kyXUj9jIUCKxvVFT8HSl/wAtuVlKxbgknJF1YlaP0qx Z7jnPFz0pGya38wzHSk84REpuqhHgMZoRAUYXuBtLhCN20wEq7uimhksUMQ3GKrX1dAJ v04BLvbn/yQkpQqlsk0gS2KzU+JNKn+kkAl7J22BNM0ucaAHg/9AZVaqpSWfwSP3cwCI P7R0aGz15R6dG+yeSUWeDRSlAFIlqM15xjqvAzib8gz08narANHt3MTV2lj5ir1wMm6d CIMw== X-Gm-Message-State: AOAM532Cc2mtWW1big4/rQqF9gcgvWn42Nuvto8beJ/XoC5Og3kHtWqp BhrKYsuwKQwZgi1ucODSwYWJkQErK3R4pZGPJ6Y= X-Google-Smtp-Source: ABdhPJxSv7vP1ns4r2NSsMM2sG4AnMbhdMd2u2JGPaOtI9CbdhwHffXf6dgVUZYIL+N/lkjxHxnDfuoEWBS/zZzrLiw= X-Received: by 2002:a05:6402:16c8:: with SMTP id r8mr6836144edx.101.1632417357693; Thu, 23 Sep 2021 10:15:57 -0700 (PDT) MIME-Version: 1.0 References: <20210923032830.314328-1-shy828301@gmail.com> <20210923032830.314328-2-shy828301@gmail.com> <20210923143901.mdc6rejuh7hmr5vh@box.shutemov.name> In-Reply-To: <20210923143901.mdc6rejuh7hmr5vh@box.shutemov.name> From: Yang Shi Date: Thu, 23 Sep 2021 10:15:45 -0700 Message-ID: Subject: Re: [v2 PATCH 1/5] mm: filemap: check if THP has hwpoisoned subpage for PMD page fault To: "Kirill A. Shutemov" Cc: =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= , Hugh Dickins , "Kirill A. Shutemov" , Matthew Wilcox , Peter Xu , Oscar Salvador , Andrew Morton , Linux MM , Linux FS-devel Mailing List , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 23, 2021 at 7:39 AM Kirill A. Shutemov wrote: > > On Wed, Sep 22, 2021 at 08:28:26PM -0700, Yang Shi wrote: > > When handling shmem page fault the THP with corrupted subpage could be PMD > > mapped if certain conditions are satisfied. But kernel is supposed to > > send SIGBUS when trying to map hwpoisoned page. > > > > There are two paths which may do PMD map: fault around and regular fault. > > > > Before commit f9ce0be71d1f ("mm: Cleanup faultaround and finish_fault() codepaths") > > the thing was even worse in fault around path. The THP could be PMD mapped as > > long as the VMA fits regardless what subpage is accessed and corrupted. After > > this commit as long as head page is not corrupted the THP could be PMD mapped. > > > > In the regulat fault path the THP could be PMD mapped as long as the corrupted > > s/regulat/regular/ > > > page is not accessed and the VMA fits. > > > > This loophole could be fixed by iterating every subpage to check if any > > of them is hwpoisoned or not, but it is somewhat costly in page fault path. > > > > So introduce a new page flag called HasHWPoisoned on the first tail page. It > > indicates the THP has hwpoisoned subpage(s). It is set if any subpage of THP > > is found hwpoisoned by memory failure and cleared when the THP is freed or > > split. > > > > Cc: > > Suggested-by: Kirill A. Shutemov > > Signed-off-by: Yang Shi > > --- > > ... > > > diff --git a/mm/filemap.c b/mm/filemap.c > > index dae481293b5d..740b7afe159a 100644 > > --- a/mm/filemap.c > > +++ b/mm/filemap.c > > @@ -3195,12 +3195,14 @@ static bool filemap_map_pmd(struct vm_fault *vmf, struct page *page) > > } > > > > if (pmd_none(*vmf->pmd) && PageTransHuge(page)) { > > - vm_fault_t ret = do_set_pmd(vmf, page); > > - if (!ret) { > > - /* The page is mapped successfully, reference consumed. */ > > - unlock_page(page); > > - return true; > > - } > > + vm_fault_t ret = do_set_pmd(vmf, page); > > + if (ret == VM_FAULT_FALLBACK) > > + goto out; > > Hm.. What? I don't get it. Who will establish page table in the pmd then? Aha, yeah. It should jump to the below PMD populate section. Will fix it in the next version. > > > + if (!ret) { > > + /* The page is mapped successfully, reference consumed. */ > > + unlock_page(page); > > + return true; > > + } > > } > > > > if (pmd_none(*vmf->pmd)) { > > @@ -3220,6 +3222,7 @@ static bool filemap_map_pmd(struct vm_fault *vmf, struct page *page) > > return true; > > } > > > > +out: > > return false; > > } > > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > index 5e9ef0fc261e..0574b1613714 100644 > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -2426,6 +2426,8 @@ static void __split_huge_page(struct page *page, struct list_head *list, > > /* lock lru list/PageCompound, ref frozen by page_ref_freeze */ > > lruvec = lock_page_lruvec(head); > > > > + ClearPageHasHWPoisoned(head); > > + > > Do we serialize the new flag with lock_page() or what? I mean what > prevents the flag being set again after this point, but before > ClearPageCompound()? No, not in this patch. But I think we could use refcount. THP split would freeze refcount and the split is guaranteed to succeed after that point, so refcount can be checked in memory failure. The SetPageHasHWPoisoned() call could be moved to __get_hwpoison_page() when get_unless_page_zero() bumps the refcount successfully. If the refcount is zero it means the THP is under split or being freed, we don't care about these two cases. The THP might be mapped before this flag is set, but the process will be killed later, so it seems fine. > > -- > Kirill A. Shutemov