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Mon, 8 Nov 2021 20:03:26 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0072.hostedemail.com [216.40.44.72]) by kanga.kvack.org (Postfix) with ESMTP id C23906B0071 for ; Mon, 8 Nov 2021 20:03:26 -0500 (EST) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 8099F181B5E9E for ; Tue, 9 Nov 2021 01:03:26 +0000 (UTC) X-FDA: 78787593612.02.2E5D747 Received: from mail-ed1-f50.google.com (mail-ed1-f50.google.com [209.85.208.50]) by imf19.hostedemail.com (Postfix) with ESMTP id ED03FB000442 for ; Tue, 9 Nov 2021 01:03:17 +0000 (UTC) Received: by mail-ed1-f50.google.com with SMTP id o8so69742039edc.3 for ; Mon, 08 Nov 2021 17:03:26 -0800 (PST) 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=KZr9FPrZOxgsc8U/wDnZ9LLLwqLTqPz85QXmM/1k+jk=; b=TeNAQ5OubajkI3l1MfahzCgoz+EVErCV6IZJNzki5F7+gKV4K8rgOl14X8FjjJP/zO nqAzQ+GiDxTt9tl/D5/Gm2R4rPkaZEYiTDGCHO0rPxTqXZCKR7B4FiB9zO0jKkFV4DR9 4u5vDGWVkhoTyt5MlGEo8V1xdwn1a2oJ3fVC/5PDkl9urx6+gjNILjk0NtPmxknDXrXN 03sUtFermnuyKGUwqdDzOJcUTR3hgMB99n0Sypc1pUReDXLaVG2YObyb0vunZ9A0yyGh RWOjvjyfNU9xyf30L89p8TPlzzY4M9Vi5iu66MVV74j04Vc7WLjnCloIf/2YnErlyI3F Q2Jw== 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=KZr9FPrZOxgsc8U/wDnZ9LLLwqLTqPz85QXmM/1k+jk=; b=ujwsuYV++uZRqQg6Ts8DRdVMroZO3emyYZB5f5K95wnj5BrEHXJvWBVeCVSs/uDfm3 QaaC3wvzgTYD/hc6L2RxaLzu3tCLddvOPG9JnaRKvFOpDJiQlNr0UZr9JWfG3oSXN1DK veZ33VFoIq0kut7QBOLxqEKPPlT7cvSGQvEN/k7Chnr33kUlMemQpKRdY5wdNWv57DzX tVDbs9HQDu7A7Cg3fn0OdliZUGSk6RmnDhfCXgua4IUx4YK2AshjbcPwj20Pqf4kEiSw qSiLX/jqsubfgiVyxSKMsfsyMHO1NjvvRj/Q9PaTMTfiek8AL00PCSk3kQbk6AVFMda9 IVBA== X-Gm-Message-State: AOAM532bljWRYWVLyO9EvBfudcf6XFnttFlYQToR0qP7NgIKVjg/Jvbm EI5uYDoqE6U+a7ThZLKkLE6pqqcbWNQYqPM86Ek= X-Google-Smtp-Source: ABdhPJxkaEeOP7RUo6eIVTAm9qolIyX+ECKaCMHrhmyNtkLMv8worAYtlC3m+2ROqdlUd5ukHIn2jnstxCAyb/h6DMk= X-Received: by 2002:a05:6402:520b:: with SMTP id s11mr4531859edd.363.1636419804995; Mon, 08 Nov 2021 17:03:24 -0800 (PST) MIME-Version: 1.0 References: <20211105055058.3152564-1-naoya.horiguchi@linux.dev> <20211105055058.3152564-4-naoya.horiguchi@linux.dev> <20211109005320.GA3341842@u2004> In-Reply-To: <20211109005320.GA3341842@u2004> From: Yang Shi Date: Mon, 8 Nov 2021 17:03:13 -0800 Message-ID: Subject: Re: [PATCH v3 3/3] mm/hwpoison: fix unpoison_memory() To: Naoya Horiguchi Cc: Linux MM , Andrew Morton , David Hildenbrand , Oscar Salvador , Michal Hocko , Ding Hui , Tony Luck , "Aneesh Kumar K.V" , Miaohe Lin , Peter Xu , Naoya Horiguchi , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=TeNAQ5Ou; spf=pass (imf19.hostedemail.com: domain of shy828301@gmail.com designates 209.85.208.50 as permitted sender) smtp.mailfrom=shy828301@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: ED03FB000442 X-Stat-Signature: 3jd3dy461dikpca8ssee8fi5s4ip3pa3 X-HE-Tag: 1636419797-52879 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Nov 8, 2021 at 4:53 PM Naoya Horiguchi wrote: > > On Mon, Nov 08, 2021 at 03:27:55PM -0800, Yang Shi wrote: > > On Thu, Nov 4, 2021 at 10:52 PM Naoya Horiguchi > > wrote: > ... > > > @@ -1942,6 +1987,26 @@ core_initcall(memory_failure_init); > > > pr_info(fmt, pfn); \ > > > }) > > > > > > +static inline int clear_page_hwpoison(struct ratelimit_state *rs, struct page *p) > > > +{ > > > + if (TestClearPageHWPoison(p)) { > > > + unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n", > > > + page_to_pfn(p), rs); > > > + num_poisoned_pages_dec(); > > > + return 1; > > > + } > > > + return 0; > > > +} > > > + > > > +static inline int unpoison_taken_off_page(struct ratelimit_state *rs, > > > + struct page *p) > > > +{ > > > + if (put_page_back_buddy(p) && clear_page_hwpoison(rs, p)) > > > > It seems there might be race condition between free and allocation to > > kick the page out of buddy before the hwpoisoned flag is cleared IIUC? > > > > CPU A CPU B > > Free: Allocation: > > acquire zone lock > > put back to buddy > > release zone lock > > acquire zone lock > > try to allocate this page > > if it is hwpoisoned then reset > > PageBuddy (not buddy page anymore) > > release zone lock > > > > Did I miss something? > > No, this is a nice catch. CPU B finds hwpoisoned page on free list then > calling bad_page(). So doing "put back to buddy" and clear_page_hwpoison > inside a single zone lock should prevent this race. Yeah, or clear the flag before putting it back to buddy? Anyway clearing the flag under zone lock is not a big deal either. > > Thanks, > Naoya Horiguchi