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 D1860C433FE for ; Mon, 7 Mar 2022 16:35:28 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 226148D0002; Mon, 7 Mar 2022 11:35:28 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 1D54B8D0001; Mon, 7 Mar 2022 11:35:28 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 09E0E8D0002; Mon, 7 Mar 2022 11:35:28 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0243.hostedemail.com [216.40.44.243]) by kanga.kvack.org (Postfix) with ESMTP id F00FD8D0001 for ; Mon, 7 Mar 2022 11:35:27 -0500 (EST) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 9891CA8329 for ; Mon, 7 Mar 2022 16:35:27 +0000 (UTC) X-FDA: 79218140694.30.9AE9D84 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf08.hostedemail.com (Postfix) with ESMTP id C6CC716000B for ; Mon, 7 Mar 2022 16:35:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=tEpagJj9t2o6OBo2LyfR78mC1PBCzGopqSpUCsiMZj8=; b=mgLq5vWcrbHbqiR1CIRlDBbC1g vM1ubvNcbK3M8PCoJWLMzo3gSOluj7/rCcw7pLHRPVO860CDISJ6STa1uly8hoktHdm2uPe1uDcFC 3Ak/yIdl+4Bh6iy5AKiLZYxzj7fANOYl7ZFaZJDwOoj5FJpNHPg04sUzOqPo9IScToRtej51OxplV 2jQLJv4FGmTSRL/SErTy/dFT8pFGBQ7Z1j+/b3flYSsmUbGbbsaymgQUSITK6kMIhElaugocayadJ BnU+2agxFd9yLoTqG4llKUBSA0FiOnGWX0R26bvNANdmvRHI/s1ucv8GvgwIlGuj9h/HXP2wGtT3F rcharuow==; Received: from mcgrof by bombadil.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nRGKI-000r2h-Pq; Mon, 07 Mar 2022 16:35:14 +0000 Date: Mon, 7 Mar 2022 08:35:14 -0800 From: Luis Chamberlain To: Muchun Song Cc: corbet@lwn.net, mike.kravetz@oracle.com, akpm@linux-foundation.org, keescook@chromium.org, yzaikin@google.com, osalvador@suse.de, david@redhat.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com, smuchun@gmail.com Subject: Re: [PATCH v3 1/4] mm: hugetlb: disable freeing vmemmap pages when struct page crosses page boundaries Message-ID: References: <20220307130708.58771-1-songmuchun@bytedance.com> <20220307130708.58771-2-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220307130708.58771-2-songmuchun@bytedance.com> X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: C6CC716000B X-Stat-Signature: kmeocmd4zxh8c6drebkt4pnspfjaek1j Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=infradead.org header.s=bombadil.20210309 header.b=mgLq5vWc; spf=none (imf08.hostedemail.com: domain of mcgrof@infradead.org has no SPF policy when checking 198.137.202.133) smtp.mailfrom=mcgrof@infradead.org; dmarc=fail reason="No valid SPF, DKIM not aligned (relaxed)" header.from=kernel.org (policy=none) X-Rspam-User: X-HE-Tag: 1646670926-982743 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, Mar 07, 2022 at 09:07:05PM +0800, Muchun Song wrote: > If the size of "struct page" is not the power of two and this > feature is enabled, then the vmemmap pages of HugeTLB will be > corrupted after remapping (panic is about to happen in theory). Huh what? If a panic is possible best we prevent this in kconfig all together. I'd instead just put some work into this instead of adding all this run time hacks. Can you try to add kconfig magic to detect if a PAGE_SIZE is PO2? Luis