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 E9C67C433F5 for ; Wed, 13 Apr 2022 19:08:13 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 29E156B0072; Wed, 13 Apr 2022 15:08:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 24E4A6B0073; Wed, 13 Apr 2022 15:08:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1165C6B0074; Wed, 13 Apr 2022 15:08:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0059.hostedemail.com [216.40.44.59]) by kanga.kvack.org (Postfix) with ESMTP id F2B896B0072 for ; Wed, 13 Apr 2022 15:08:12 -0400 (EDT) Received: from smtpin27.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id A54A3AA480 for ; Wed, 13 Apr 2022 19:08:12 +0000 (UTC) X-FDA: 79352791224.27.8E6050D Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf31.hostedemail.com (Postfix) with ESMTP id 79D9C20005 for ; Wed, 13 Apr 2022 19:08:11 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 6D5CFB8275E; Wed, 13 Apr 2022 19:08:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3C7C7C385A3; Wed, 13 Apr 2022 19:08:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1649876887; bh=HS2szbOJxe7C3PIkz+onUkqYqx0zj5ZuzRc1VOGk0IM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=DD5eWZ+7y7wEUnMyatZWxirBYZvREPY7llxtxRnNTa36xQjeWepf5jUk7HQvhTzkM vcb10gqp4plEO0lSUDjx0bwDBE1yl4O6/OjlwSS1E2eqjTF3/YRuCqRQ0oe1KRdPbI hy9guWV8Z+7Yo9UAghXSkCglT+RBOroKfE96qpO4= Date: Wed, 13 Apr 2022 12:08:04 -0700 From: Andrew Morton To: Muchun Song Cc: corbet@lwn.net, mike.kravetz@oracle.com, mcgrof@kernel.org, keescook@chromium.org, yzaikin@google.com, osalvador@suse.de, david@redhat.com, masahiroy@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com, smuchun@gmail.com Subject: Re: [PATCH v8 1/4] mm: hugetlb_vmemmap: introduce CONFIG_HUGETLB_PAGE_HAS_OPTIMIZE_VMEMMAP Message-Id: <20220413120804.3570dc230a958f4923e3f3c3@linux-foundation.org> In-Reply-To: <20220413144748.84106-2-songmuchun@bytedance.com> References: <20220413144748.84106-1-songmuchun@bytedance.com> <20220413144748.84106-2-songmuchun@bytedance.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: rt6e16ktfdy1ts51dcf35uxnmjpcmgwc Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=DD5eWZ+7; dmarc=none; spf=pass (imf31.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 79D9C20005 X-HE-Tag: 1649876891-833564 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 Wed, 13 Apr 2022 22:47:45 +0800 Muchun Song wrote: > If the size of "struct page" is not the power of two but with the feature > of minimizing overhead of struct page associated with each HugeTLB is > enabled, then the vmemmap pages of HugeTLB will be corrupted after > remapping (panic is about to happen in theory). But this only exists when > !CONFIG_MEMCG && !CONFIG_SLUB on x86_64. However, it is not a conventional > configuration nowadays. So it is not a real word issue, just the result > of a code review. The patch does add a whole bunch of tricky junk to address something which won't happen. How about we simply disable CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP if (!CONFIG_MEMCG && !CONFIG_SLUB)?