From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751670AbeCTVfk (ORCPT ); Tue, 20 Mar 2018 17:35:40 -0400 Received: from aserp2130.oracle.com ([141.146.126.79]:44864 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751411AbeCTVfj (ORCPT ); Tue, 20 Mar 2018 17:35:39 -0400 Subject: Re: [PATCH] mm/hugetlb: prevent hugetlb VMA to be misaligned From: Mike Kravetz To: Laurent Dufour , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrea Arcangeli , mhocko@kernel.org, Dan Williams References: <1521566754-30390-1-git-send-email-ldufour@linux.vnet.ibm.com> <86240c1a-d1f1-0f03-855e-c5196762ec0a@oracle.com> Message-ID: <0d24f817-303a-7b4d-4603-b2d14e4b391a@oracle.com> Date: Tue, 20 Mar 2018 14:35:28 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: <86240c1a-d1f1-0f03-855e-c5196762ec0a@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8838 signatures=668695 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1803200127 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/20/2018 02:26 PM, Mike Kravetz wrote: > Thanks Laurent! > > This bug was introduced by 31383c6865a5. Dan's changes for 31383c6865a5 > seem pretty straight forward. It simply replaces an explicit check when > splitting a vma to a new vm_ops split callout. Unfortunately, mappings > created via shmget/shmat have their vm_ops replaced. Therefore, this > split callout is never made. > > The shm vm_ops do indirectly call the original vm_ops routines as needed. > Therefore, I would suggest a patch something like the following instead. > If we move forward with the patch, we should include Laurent's BUG output > and perhaps test program in the commit message. Sorry, patch in previous mail was a mess >>From 7a19414319c7937fd2757c27f936258f16c1f61d Mon Sep 17 00:00:00 2001 From: Mike Kravetz Date: Tue, 20 Mar 2018 13:56:57 -0700 Subject: [PATCH] shm: add split function to shm_vm_ops The split function was added to vm_operations_struct to determine if a mapping can be split. This was mostly for device-dax and hugetlbfs mappings which have specific alignment constraints. mappings initiated via shmget/shmat have their original vm_ops overwritten with shm_vm_ops. shm_vm_ops functions will call back to the original vm_ops if needed. Add such a split function. Fixes: 31383c6865a5 ("mm, hugetlbfs: introduce ->split() to vm_operations_struct) Reported by: Laurent Dufour Signed-off-by: Mike Kravetz --- ipc/shm.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/ipc/shm.c b/ipc/shm.c index 7acda23430aa..50e88fc060b1 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -386,6 +386,17 @@ static int shm_fault(struct vm_fault *vmf) return sfd->vm_ops->fault(vmf); } +static int shm_split(struct vm_area_struct *vma, unsigned long addr) +{ + struct file *file = vma->vm_file; + struct shm_file_data *sfd = shm_file_data(file); + + if (sfd->vm_ops && sfd->vm_ops->split) + return sfd->vm_ops->split(vma, addr); + + return 0; +} + #ifdef CONFIG_NUMA static int shm_set_policy(struct vm_area_struct *vma, struct mempolicy *new) { @@ -510,6 +521,7 @@ static const struct vm_operations_struct shm_vm_ops = { .open = shm_open, /* callback for a new vm-area open */ .close = shm_close, /* callback for when the vm-area is released */ .fault = shm_fault, + .split = shm_split, #if defined(CONFIG_NUMA) .set_policy = shm_set_policy, .get_policy = shm_get_policy, -- 2.13.6