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 A3C79C7EE26 for ; Mon, 22 May 2023 08:54:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2F162900003; Mon, 22 May 2023 04:54:04 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2A17C900002; Mon, 22 May 2023 04:54:04 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 16912900003; Mon, 22 May 2023 04:54:04 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 07598900002 for ; Mon, 22 May 2023 04:54:04 -0400 (EDT) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id CE8AEC0C94 for ; Mon, 22 May 2023 08:54:03 +0000 (UTC) X-FDA: 80817278766.10.D447503 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf25.hostedemail.com (Postfix) with ESMTP id C7793A000A for ; Mon, 22 May 2023 08:54:01 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=none; spf=pass (imf25.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1684745642; 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=UveTCXeiSNmbff7ExNVuWiFTUqJ/2KvZ+OmUAjn9YMw=; b=8k+WiKOHT6becPP/x//ZbXVCXi9CUer/fpAGZ/J1odEe/qyLQ3SyyzqfB+4fuIq3D2Z0kl Z+uutbJPOxMsjNIOiQtIsjKV3SSm7OZUZ9h2dqyFd7aVFakpL1HLnv36ai8AqvLV/bVokr Oh5oGbyOZ20DXTfBiqmVCtH7W7iT+6k= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1684745642; a=rsa-sha256; cv=none; b=akiMZDWgWKyRQDTvwymJ917CHzuwEyh+U/4IJmLJiq93aABe59DzpfMIIZ3t2m4VLu1xwk 8KYMjqzGQyxOeIYYx0T0anVP/tS5Jn1779iJ2OSoEoz1cPA1Odkc0yui0uc30MThCRFuMR yRJ0NpjPzynfw5UJ6JHcUkKYjL071QE= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=none; spf=pass (imf25.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com 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 6FDDC11FB; Mon, 22 May 2023 01:54:45 -0700 (PDT) Received: from [10.57.73.5] (unknown [10.57.73.5]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 62E3C3F6C4; Mon, 22 May 2023 01:53:58 -0700 (PDT) Message-ID: <1a6468c3-0395-173d-7a0a-96dcd4f7616c@arm.com> Date: Mon, 22 May 2023 09:53:56 +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: SeongJae Park Cc: Yu Zhao , Andrew Morton , 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: <20230519195435.90394-1-sj@kernel.org> From: Ryan Roberts In-Reply-To: <20230519195435.90394-1-sj@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: 5cmhqwegdm6iu99upy1d41yfwmpeshtj X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: C7793A000A X-Rspam-User: X-HE-Tag: 1684745641-532234 X-HE-Meta: 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 jTsK7jFx GXFLz6svp//fk+/Z7Uwyohvb9c71d4Ido2ZJ83+QO1l06X8pTDuOj0IboRKJMsdPLcrGpwCSyrqrOdLmTQlDpt4nZonJmmGCHYZIROPCbCElTURjd55X/lA3kH8AzuVVg5uXFcBzr6/ccTQF8hjOXHevfX7zHl0LWxbiJR9Lbq41U/tEHMcVbmfmY2T1/Bvxq/YuM 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 20:54, SeongJae Park wrote: > On Fri, 19 May 2023 10:02:48 +0100 Ryan Roberts wrote: > >> 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? > > Yes, I would be happy for that :) Nevertheless, because that's a refactoring > rather than a fix, I'd be happier if you could do that with a separate patch. Great - I'll do it like this for v3. > > > Thanks, > SJ > >> >> Thanks, >> Ryan >>