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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11345C67790 for ; Fri, 27 Jul 2018 21:50:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BA88F20842 for ; Fri, 27 Jul 2018 21:50:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BA88F20842 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389853AbeG0XOB (ORCPT ); Fri, 27 Jul 2018 19:14:01 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:36118 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389728AbeG0XOB (ORCPT ); Fri, 27 Jul 2018 19:14:01 -0400 Received: from localhost.localdomain (c-24-4-125-7.hsd1.ca.comcast.net [24.4.125.7]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id BF661CBD; Fri, 27 Jul 2018 21:50:11 +0000 (UTC) Date: Fri, 27 Jul 2018 14:50:09 -0700 From: Andrew Morton To: Jane Chu Cc: dan.j.williams@intel.com, mhocko@suse.com, jack@suse.cz, jglisse@redhat.com, mike.kravetz@oracle.com, dave@stgolabs.net, linux-mm@kvack.org, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org, Hugh Dickins Subject: Re: [PATCH] ipc/shm.c add ->pagesize function to shm_vm_ops Message-Id: <20180727145009.5dde68fb680ec148a7504f37@linux-foundation.org> In-Reply-To: <20180727211727.5020-1-jane.chu@oracle.com> References: <20180727211727.5020-1-jane.chu@oracle.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 27 Jul 2018 15:17:27 -0600 Jane Chu wrote: > Commit 05ea88608d4e13 (mm, hugetlbfs: introduce ->pagesize() to > vm_operations_struct) adds a new ->pagesize() function to > hugetlb_vm_ops, intended to cover all hugetlbfs backed files. That was merged three months ago. Can you suggest why this was only noticed now? What workload triggered this? I see no cc:stable, but 4.17 is affected? > With System V shared memory model, if "huge page" is specified, > the "shared memory" is backed by hugetlbfs files, but the mappings > initiated via shmget/shmat have their original vm_ops overwritten > with shm_vm_ops, so we need to add a ->pagesize function to shm_vm_ops. > Otherwise, vma_kernel_pagesize() returns PAGE_SIZE given a hugetlbfs > backed vma, result in below BUG: > > fs/hugetlbfs/inode.c > 443 if (unlikely(page_mapped(page))) { > 444 BUG_ON(truncate_op); OK, help me out here. How does an incorrect return value from vma_kernel_pagesize() result in remove_inode_hugepages() deciding that it's truncating a mapped page?