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Wed, 22 Oct 2025 14:18:40 +0800 (CST) Received: from dggpemf100008.china.huawei.com (unknown [7.185.36.138]) by mail.maildlp.com (Postfix) with ESMTPS id 79C4C1A0188; Wed, 22 Oct 2025 14:19:21 +0800 (CST) Received: from [10.174.177.243] (10.174.177.243) by dggpemf100008.china.huawei.com (7.185.36.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 22 Oct 2025 14:19:20 +0800 Message-ID: Date: Wed, 22 Oct 2025 14:19:19 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64: mte: Do not warn if the page is already tagged in copy_highpage() To: Yang Shi , Catalin Marinas CC: , , , Will Deacon , David Hildenbrand References: <20251021181353.3842660-1-catalin.marinas@arm.com> Content-Language: en-US From: Kefeng Wang In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: kwepems200001.china.huawei.com (7.221.188.67) To dggpemf100008.china.huawei.com (7.185.36.138) X-Rspamd-Server: rspam01 X-Stat-Signature: x9pn3bbm83u3iasj4ya4oo4bshmxusbk X-Rspam-User: X-Rspamd-Queue-Id: E10E140008 X-HE-Tag: 1761113965-943278 X-HE-Meta: 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 bVtQ4zC9 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 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: List-Subscribe: List-Unsubscribe: On 2025/10/22 3:00, Yang Shi wrote: > On Tue, Oct 21, 2025 at 11:14 AM Catalin Marinas > wrote: >> >> The arm64 copy_highpage() assumes that the destination page is newly >> allocated and not MTE-tagged (PG_mte_tagged unset) and warns >> accordingly. However, following commit 060913999d7a ("mm: migrate: >> support poisoned recover from migrate folio"), __folio_mc_copy() is no "__" prefix >> called before __folio_migrate_mapping(). If the latter fails (-EAGAIN), >> the copy will be done again to the same destination page. Since >> copy_highpage() already set the PG_mte_tagged flag, this second copy >> will warn. >> >> Replace the WARN_ON(page already tagged) in the arm64 copy_highpage() >> with a comment. >> >> Signed-off-by: Catalin Marinas >> Reported-by: syzbot+d1974fc28545a3e6218b@syzkaller.appspotmail.com >> Link: https://lore.kernel.org/r/68dda1ae.a00a0220.102ee.0065.GAE@google.com >> Cc: # 6.12.x >> Cc: Will Deacon >> Cc: David Hildenbrand >> Cc: Kefeng Wang >> --- >> arch/arm64/mm/copypage.c | 9 +++++++-- >> 1 file changed, 7 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c >> index a86c897017df..40749d0a385c 100644 >> --- a/arch/arm64/mm/copypage.c >> +++ b/arch/arm64/mm/copypage.c >> @@ -51,8 +51,13 @@ void copy_highpage(struct page *to, struct page *from) >> } >> folio_set_hugetlb_mte_tagged(dst); >> } else if (page_mte_tagged(from)) { >> - /* It's a new page, shouldn't have been tagged yet */ >> - WARN_ON_ONCE(!try_page_mte_tagging(to)); > > I think you should remove the WARN_ON_ONCE in the above hugetlb chunk > too IIUC. migrate_huge_page_move_mapping() does the similar thing. > Yes, it's better to remove WARN_ON_ONCE for hugetlb too. > Thanks, > Yang > >> + /* >> + * Most of the time it's a new page that shouldn't have been >> + * tagged yet. However, folio migration can end up reusing the >> + * same page without untagging it. Ignore the warning if the >> + * page is already tagged. >> + */ >> + try_page_mte_tagging(to); >> >> mte_copy_page_tags(kto, kfrom); >> set_page_mte_tagged(to); >>