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 BDBE9C77B7A for ; Fri, 19 May 2023 09:02:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 17B62900005; Fri, 19 May 2023 05:02:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 12A3E900004; Fri, 19 May 2023 05:02:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 018D5900005; Fri, 19 May 2023 05:02:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id E6078900004 for ; Fri, 19 May 2023 05:02:54 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 9FE3EC094B for ; Fri, 19 May 2023 09:02:54 +0000 (UTC) X-FDA: 80806414668.21.B684004 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf03.hostedemail.com (Postfix) with ESMTP id 88EF620012 for ; Fri, 19 May 2023 09:02:52 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf03.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1684486972; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=jtxlwEbadlbsMKgGCDNmUp7O/cLZZVwXR2Eqt/No1y8=; b=UeTlULjmx7QKI4/U7S+Mbk2gL4x4BfL+2tnmL65sRDBKZU6Kfmp2rz45i76f5b4euOJEF9 t2PeQTuMsX19dOIt7ys/89J/60dyEOOXoUGdC93Zc5veU6Hf/XtBk8LzSTAjACpNo3YfsX TNT6VoQOaq32Gb2Bfq//uW7SBWIzVbY= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf03.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1684486972; a=rsa-sha256; cv=none; b=03QiL460ESvsGvVik7RrmiTIAwOp7D5soqbwXO8c/rSdvk7yFMajG44XUOIIT8SHpF2rt7 2cMtSgwJz77Bxqc3lfOclKKdZFCLPCCqk+FwRipbL8GkIVuwwRw4Y+xYaCKM1M8mjVscpe ZGG8cq8OHtmOp/0o3PgTm9Ix0aF03rw= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 552991FB; Fri, 19 May 2023 02:03:36 -0700 (PDT) Received: from [10.57.73.191] (unknown [10.57.73.191]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D578A3F73F; Fri, 19 May 2023 02:02:49 -0700 (PDT) Message-ID: <88c125fd-2294-4650-65b1-6be56589120e@arm.com> Date: Fri, 19 May 2023 10:02:48 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [PATCH v2 2/5] mm: damon must atomically clear young on ptes and pmds To: Yu Zhao Cc: Andrew Morton , SeongJae Park , Christoph Hellwig , "Matthew Wilcox (Oracle)" , "Kirill A. Shutemov" , Lorenzo Stoakes , Uladzislau Rezki , Zi Yan , linux-kernel@vger.kernel.org, linux-mm@kvack.org, damon@lists.linux.dev References: <20230518110727.2106156-1-ryan.roberts@arm.com> <20230518110727.2106156-3-ryan.roberts@arm.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: hz5zd5p74xqij3uuntgphq6dypw41djz X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 88EF620012 X-HE-Tag: 1684486972-631855 X-HE-Meta: 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 lFd1GPDx qe6LUQEe6w7acKzH7XeLwN8WrVSLjoW/d4vdUDYmZn0ryNJMxZyysddTX/sLn2N+3QlWGWUlzUGjs6SEJstXCI/hR5DQ8HGvO+93NASYrj/gXGaazhlAvknMn9XCsQl0ab94h08OvsHGqZ1Wfatsyp5UVjNrHP9r+IlGae/b9kHGyEpfAOoQTUUh9L6TWRikNPV/5 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 19/05/2023 00:19, Yu Zhao wrote: > On Thu, May 18, 2023 at 5:07 AM Ryan Roberts wrote: >> >> It is racy to non-atomically read a pte, then clear the young bit, then >> write it back as this could discard dirty information. Further, it is >> bad practice to directly set a pte entry within a table. Instead >> clearing young must go through the arch-provided helper, >> ptep_test_and_clear_young() to ensure it is modified atomically and to >> give the arch code visibility and allow it to check (and potentially >> modify) the operation. >> >> Fixes: 46c3a0accdc4 ("mm/damon/vaddr: separate commonly usable functions") > > This should be a separate patch, since it's independent from what the > series tries to do. > > And that patch should cc stable, since it fixes user data corruption. Fair point. The first 3 patches are fixes for issues I found during the conversion. So if you're ok with it, I'll split into 2 series; the first 3 patches in the first, and the conversion to ptep_deref() (or ptep_get(), as per your comments in the other thread) in the second. I guess the whole first series should go to stable. Let me know if you disagree. > >> Signed-off-by: Ryan Roberts >> Reviewed-by: Zi Yan >> --- >> mm/damon/ops-common.c | 16 ++++++---------- >> mm/damon/ops-common.h | 4 ++-- >> mm/damon/paddr.c | 4 ++-- >> mm/damon/vaddr.c | 4 ++-- >> 4 files changed, 12 insertions(+), 16 deletions(-) >> >> diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c >> index cc63cf953636..acc264b97903 100644 >> --- a/mm/damon/ops-common.c >> +++ b/mm/damon/ops-common.c >> @@ -37,7 +37,7 @@ struct folio *damon_get_folio(unsigned long pfn) >> return folio; >> } >> >> -void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, unsigned long addr) >> +void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr) >> { >> bool referenced = false; >> struct folio *folio = damon_get_folio(pte_pfn(*pte)); >> @@ -45,13 +45,11 @@ void damon_ptep_mkold(pte_t *pte, struct mm_struct *mm, unsigned long addr) >> if (!folio) >> return; >> >> - if (pte_young(*pte)) { >> + if (ptep_test_and_clear_young(vma, addr, pte)) >> referenced = true; >> - *pte = pte_mkold(*pte); >> - } >> >> #ifdef CONFIG_MMU_NOTIFIER >> - if (mmu_notifier_clear_young(mm, addr, addr + PAGE_SIZE)) >> + if (mmu_notifier_clear_young(vma->vm_mm, addr, addr + PAGE_SIZE)) >> referenced = true; >> #endif /* CONFIG_MMU_NOTIFIER */ > > Use ptep_clear_young_notify(). Similar below. This looks sensible but I'd like clarification from SeongJae: Are you happy for me to do this refactoring as part of the patch? Thanks, Ryan