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 7A706C43334 for ; Fri, 15 Jul 2022 03:56:47 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7F1309401C8; Thu, 14 Jul 2022 23:56:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7A0A49401A5; Thu, 14 Jul 2022 23:56:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6B6D29401C8; Thu, 14 Jul 2022 23:56:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 582A69401A5 for ; Thu, 14 Jul 2022 23:56:46 -0400 (EDT) Received: from smtpin27.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 1F9EA35516 for ; Fri, 15 Jul 2022 03:56:46 +0000 (UTC) X-FDA: 79687972812.27.4678C9F Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by imf08.hostedemail.com (Postfix) with ESMTP id 4736E16006F for ; Fri, 15 Jul 2022 03:56:45 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4LkctV5XsQzkX3S; Fri, 15 Jul 2022 11:54:26 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 15 Jul 2022 11:56:41 +0800 Subject: Re: [PATCH] mm/hugetlb: avoid corrupting page->mapping in hugetlb_mcopy_atomic_pte To: Peter Xu , Axel Rasmussen CC: Andrew Morton , , , , References: <20220712130542.18836-1-linmiaohe@huawei.com> <20220713102357.8328614813db01b569650ffd@linux-foundation.org> From: Miaohe Lin Message-ID: <402ae708-4c86-8feb-75c4-9339e1deac3b@huawei.com> Date: Fri, 15 Jul 2022 11:56:40 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=none; spf=pass (imf08.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1657857405; a=rsa-sha256; cv=none; b=MhUonLMvrbB7HoT6kAO1zDQQQi09Pg6krVhemqO3t3zEwJEX06rhgwAGkgOJ0GGQwXRGvr l9S4m/ZmK8/okGviN+gmLaTdhjuxbxKali1G1ec9I2p6zJXRcZFhVY+6WN1KdChCDT3EkL ilCw+yQbvkMWp7IMkHp+FEQT8JpMadg= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1657857405; 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=oCw7IEIIqHU3zWcvx56D1WqOQslQBIYbw1tA/koHekY=; b=h9P9gWsaGPqregIlbwherwX3qCYgCmD5XY4GPxYdvheMA2xoh0GLd3lgtGhwCW1vpXRRsR vqyXUwNYOj2yGsJlydCNZDqsiop0MoS13ndaYiX/5sCdN5g4lEVQQhPipY3ZIynjkEv1CF pcv6todz8jcu9/q9Ac3XTI3vuveQ39w= Authentication-Results: imf08.hostedemail.com; dkim=none; spf=pass (imf08.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-Rspam-User: X-Stat-Signature: sb471jfz6ii5ku9s6kssdyqcbpo6zqia X-Rspamd-Queue-Id: 4736E16006F X-Rspamd-Server: rspam03 X-HE-Tag: 1657857405-3161 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 2022/7/14 23:52, Peter Xu wrote: > On Thu, Jul 14, 2022 at 05:59:53PM +0800, Miaohe Lin wrote: >> On 2022/7/14 1:23, Andrew Morton wrote: >>> On Tue, 12 Jul 2022 21:05:42 +0800 Miaohe Lin wrote: >>> >>>> In MCOPY_ATOMIC_CONTINUE case with a non-shared VMA, pages in the page >>>> cache are installed in the ptes. But hugepage_add_new_anon_rmap is called >>>> for them mistakenly because they're not vm_shared. This will corrupt the >>>> page->mapping used by page cache code. >>> >>> Well that sounds bad. And theories on why this has gone unnoticed for >>> over a year? I assume this doesn't have coverage in our selftests? >> >> As discussed in another thread, when minor fault handling is proposed, only >> VM_SHARED vma is expected to be supported. And the test case is also missing. > > Yes, after this patch applied it'll be great to have the test case covering > private mappings too. > > It's just that it'll be a bit more than setting test_uffdio_minor=1 for > "hugetlb" test. In hugetlb_allocate_area() we'll need to setup the alias > too for !shared case, it'll be a bit challenging since currently we're > using anonymous hugetlb mappings for private tests, and I'm not sure > whether we'll need the hugetlb path back just like what we have with > "hugetlb_shared" tests. I'm afraid not. When minor fault handling is proposed, only VM_SHARED vma is expected to be supported. It seems it's hard to image how one might benefit from using it with a private mapping. But I'm not sure as I'm still a layman in userfaultfd now. Any further suggestions? > Thanks!