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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 16C7FC433C1 for ; Fri, 26 Mar 2021 01:53:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D51AA61A3E for ; Fri, 26 Mar 2021 01:53:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230210AbhCZBwm (ORCPT ); Thu, 25 Mar 2021 21:52:42 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:14477 "EHLO szxga05-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230137AbhCZBwP (ORCPT ); Thu, 25 Mar 2021 21:52:15 -0400 Received: from DGGEMS413-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4F64fr1NYkzyNHl; Fri, 26 Mar 2021 09:50:12 +0800 (CST) Received: from [10.174.178.163] (10.174.178.163) by DGGEMS413-HUB.china.huawei.com (10.3.19.213) with Microsoft SMTP Server id 14.3.498.0; Fri, 26 Mar 2021 09:52:10 +0800 Subject: Re: [PATCH 3/8] hugetlb: add per-hstate mutex to synchronize user adjustments To: Mike Kravetz , , CC: Roman Gushchin , Michal Hocko , Shakeel Butt , Oscar Salvador , David Hildenbrand , Muchun Song , David Rientjes , Peter Zijlstra , Matthew Wilcox , HORIGUCHI NAOYA , "Aneesh Kumar K . V" , Waiman Long , Peter Xu , Mina Almasry , "Hillf Danton" , Andrew Morton References: <20210325002835.216118-1-mike.kravetz@oracle.com> <20210325002835.216118-4-mike.kravetz@oracle.com> From: Miaohe Lin Message-ID: Date: Fri, 26 Mar 2021 09:52:10 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20210325002835.216118-4-mike.kravetz@oracle.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.178.163] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/3/25 8:28, Mike Kravetz wrote: > The helper routine hstate_next_node_to_alloc accesses and modifies the > hstate variable next_nid_to_alloc. The helper is used by the routines > alloc_pool_huge_page and adjust_pool_surplus. adjust_pool_surplus is > called with hugetlb_lock held. However, alloc_pool_huge_page can not > be called with the hugetlb lock held as it will call the page allocator. > Two instances of alloc_pool_huge_page could be run in parallel or > alloc_pool_huge_page could run in parallel with adjust_pool_surplus > which may result in the variable next_nid_to_alloc becoming invalid > for the caller and pages being allocated on the wrong node. > > Both alloc_pool_huge_page and adjust_pool_surplus are only called from > the routine set_max_huge_pages after boot. set_max_huge_pages is only > called as the reusult of a user writing to the proc/sysfs nr_hugepages, > or nr_hugepages_mempolicy file to adjust the number of hugetlb pages. > > It makes little sense to allow multiple adjustment to the number of > hugetlb pages in parallel. Add a mutex to the hstate and use it to only > allow one hugetlb page adjustment at a time. This will synchronize > modifications to the next_nid_to_alloc variable. > > Signed-off-by: Mike Kravetz > --- > include/linux/hugetlb.h | 1 + > mm/hugetlb.c | 5 +++++ > 2 files changed, 6 insertions(+) > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index a7f7d5f328dc..8817ec987d68 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -566,6 +566,7 @@ HPAGEFLAG(Freed, freed) > #define HSTATE_NAME_LEN 32 > /* Defines one hugetlb page size */ > struct hstate { > + struct mutex mutex; I am also with Michal and Oscar here, renaming the mutex to something closer to its function. Reviewed-by: Miaohe Lin > int next_nid_to_alloc; > int next_nid_to_free; > unsigned int order; > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index f9ba63fc1747..404b0b1c5258 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -2616,6 +2616,8 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid, > else > return -ENOMEM; > > + /* mutex prevents concurrent adjustments for the same hstate */ > + mutex_lock(&h->mutex); > spin_lock(&hugetlb_lock); > > /* > @@ -2648,6 +2650,7 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid, > if (hstate_is_gigantic(h) && !IS_ENABLED(CONFIG_CONTIG_ALLOC)) { > if (count > persistent_huge_pages(h)) { > spin_unlock(&hugetlb_lock); > + mutex_unlock(&h->mutex); > NODEMASK_FREE(node_alloc_noretry); > return -EINVAL; > } > @@ -2722,6 +2725,7 @@ static int set_max_huge_pages(struct hstate *h, unsigned long count, int nid, > out: > h->max_huge_pages = persistent_huge_pages(h); > spin_unlock(&hugetlb_lock); > + mutex_unlock(&h->mutex); > > NODEMASK_FREE(node_alloc_noretry); > > @@ -3209,6 +3213,7 @@ void __init hugetlb_add_hstate(unsigned int order) > BUG_ON(hugetlb_max_hstate >= HUGE_MAX_HSTATE); > BUG_ON(order == 0); > h = &hstates[hugetlb_max_hstate++]; > + mutex_init(&h->mutex); > h->order = order; > h->mask = ~(huge_page_size(h) - 1); > for (i = 0; i < MAX_NUMNODES; ++i) >