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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 85FE6C10F1E for ; Thu, 15 Dec 2022 19:59:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230237AbiLOT7q (ORCPT ); Thu, 15 Dec 2022 14:59:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50398 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230152AbiLOT7p (ORCPT ); Thu, 15 Dec 2022 14:59:45 -0500 Received: from smtpout.efficios.com (unknown [IPv6:2607:5300:203:b2ee::31e5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A9EC8537E4; Thu, 15 Dec 2022 11:59:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1671134382; bh=+8V4Xbe17KtPJZrpnDJiE7xrcUeg7ukGLgngnHFtEzE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=hLTmS3Hy8cET5G/vEXbHoznchyAcWrhro1f3uhdrXrkfiXuqfzjuKBMGDc+NDbSU8 bXYFfld0lCxVYO2VTQ3pLkB1bnKrvrLanAuE1t8bbHHyMcGkN0XIY0eoU4uPuvFYPn UkiDygOVbU/aIfxb0JRpUA9YNlcpast/NNuneACVLp4uQ+7dmDNSYXeHpwOnW3Nc98 vYARm4y7r0TcIKDPcrSQstG+b4sQRkeUG0PBMtTmLb88oln7/GA5A8+JilY78Se49t Losshur3wV8qF8qTNBmnOU2KzHzk54dGOpOQgxU7V+DzbsU8MRY5mTMf3pRbTKr59/ WrWc5mrbusM4Q== Received: from [172.16.0.118] (192-222-180-24.qc.cable.ebox.net [192.222.180.24]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4NY33f2WVjzbdt; Thu, 15 Dec 2022 14:59:42 -0500 (EST) Message-ID: Date: Thu, 15 Dec 2022 15:00:04 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Subject: Re: [PATCH] mm/mempolicy: do not duplicate policy if it is not applicable for set_mempolicy_home_node Content-Language: en-US To: Michal Hocko Cc: Andrew Morton , linux-kernel@vger.kernel.org, "Aneesh Kumar K . V" , Ben Widawsky , Dave Hansen , Feng Tang , Andrea Arcangeli , Mel Gorman , Mike Kravetz , Randy Dunlap , Vlastimil Babka , Andi Kleen , Dan Williams , Huang Ying , linux-api@vger.kernel.org, stable@vger.kernel.org References: <20221214222110.200487-1-mathieu.desnoyers@efficios.com> <72a402db-b156-74ff-2241-a018cd8ee885@efficios.com> From: Mathieu Desnoyers In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On 2022-12-15 09:49, Michal Hocko wrote: > On Thu 15-12-22 09:33:54, Mathieu Desnoyers wrote: >> On 2022-12-15 02:51, Michal Hocko wrote: > [...] >>> Btw. looking at the code again it seems rather pointless to duplicate >>> the policy just to throw it away anyway. A slightly bigger diff but this >>> looks more reasonable to me. What do you think? I can also send it as a >>> clean up on top of your fix. >> >> I think it would be best if this comes as a cleanup on top of my fix. The >> diff is larger than the minimal change needed to fix the leak in stable >> branches. >> >> Your approach looks fine, except for the vma_policy(vma) -> old change >> already spotted by Aneesh. > > This shouldn't have any real effect on the functionality. Anyway, here > is a follow up cleanup: > --- > From f3fdb6f65fa3977aab13378b8e299b168719577c Mon Sep 17 00:00:00 2001 > From: Michal Hocko > Date: Thu, 15 Dec 2022 15:41:27 +0100 > Subject: [PATCH] mm/mempolicy: do not duplicate policy if it is not applicable > for set_mempolicy_home_node > > set_mempolicy_home_node tries to duplicate a memory policy before > checking it whether it is applicable for the operation. There is > no real reason for doing that and it might actually be a pointless > memory allocation and deallocation exercise for MPOL_INTERLEAVE. > > Not a big problem but we can do better. Simply check the policy before > acting on it. > > Signed-off-by: Michal Hocko Reviewed-by: Mathieu Desnoyers > --- > mm/mempolicy.c | 28 ++++++++++++---------------- > 1 file changed, 12 insertions(+), 16 deletions(-) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 02c8a712282f..becf41e10076 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -1489,7 +1489,7 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le > { > struct mm_struct *mm = current->mm; > struct vm_area_struct *vma; > - struct mempolicy *new; > + struct mempolicy *new, *old; > unsigned long vmstart; > unsigned long vmend; > unsigned long end; > @@ -1521,31 +1521,27 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le > return 0; > mmap_write_lock(mm); > for_each_vma_range(vmi, vma, end) { > - vmstart = max(start, vma->vm_start); > - vmend = min(end, vma->vm_end); > - new = mpol_dup(vma_policy(vma)); > - if (IS_ERR(new)) { > - err = PTR_ERR(new); > - break; > - } > - /* > - * Only update home node if there is an existing vma policy > - */ > - if (!new) > - continue; > - > /* > * If any vma in the range got policy other than MPOL_BIND > * or MPOL_PREFERRED_MANY we return error. We don't reset > * the home node for vmas we already updated before. > */ > - if (new->mode != MPOL_BIND && new->mode != MPOL_PREFERRED_MANY) { > - mpol_put(new); > + old = vma_policy(vma); > + if (!old) > + continue; > + if (old->mode != MPOL_BIND && old->mode != MPOL_PREFERRED_MANY) { > err = -EOPNOTSUPP; > break; > } > + new = mpol_dup(old); > + if (IS_ERR(new)) { > + err = PTR_ERR(new); > + break; > + } > > new->home_node = home_node; > + vmstart = max(start, vma->vm_start); > + vmend = min(end, vma->vm_end); > err = mbind_range(mm, vmstart, vmend, new); > mpol_put(new); > if (err) -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com