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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,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 DD80BC2D0C0 for ; Thu, 5 Dec 2019 22:00:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B3A8E24675 for ; Thu, 5 Dec 2019 22:00:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387419AbfLEWAk (ORCPT ); Thu, 5 Dec 2019 17:00:40 -0500 Received: from out4436.biz.mail.alibaba.com ([47.88.44.36]:12080 "EHLO out4436.biz.mail.alibaba.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387396AbfLEWAk (ORCPT ); Thu, 5 Dec 2019 17:00:40 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R931e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07486;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0Tk4-tJ8_1575583231; Received: from US-143344MP.local(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0Tk4-tJ8_1575583231) by smtp.aliyun-inc.com(127.0.0.1); Fri, 06 Dec 2019 06:00:35 +0800 Subject: Re: [v3 PATCH] mm: move_pages: return valid node id in status if the page is already on the target node To: John Hubbard , fabecassis@nvidia.com, mhocko@suse.com, cl@linux.com, vbabka@suse.cz, mgorman@techsingularity.net, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <1575572053-128363-1-git-send-email-yang.shi@linux.alibaba.com> From: Yang Shi Message-ID: <93b8f639-baff-b198-84b5-713df9406a51@linux.alibaba.com> Date: Thu, 5 Dec 2019 14:00:31 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/5/19 1:27 PM, John Hubbard wrote: > On 12/5/19 10:54 AM, Yang Shi wrote: >> Felix Abecassis reports move_pages() would return random status if the >> pages are already on the target node by the below test program: >> >> ---8<--- >> >> int main(void) >> { >> const long node_id = 1; >> const long page_size = sysconf(_SC_PAGESIZE); >> const int64_t num_pages = 8; >> >> unsigned long nodemask = 1 << node_id; >> long ret = set_mempolicy(MPOL_BIND, &nodemask, sizeof(nodemask)); >> if (ret < 0) >> return (EXIT_FAILURE); >> >> void **pages = malloc(sizeof(void*) * num_pages); >> for (int i = 0; i < num_pages; ++i) { >> pages[i] = mmap(NULL, page_size, PROT_WRITE | PROT_READ, >> MAP_PRIVATE | MAP_POPULATE | MAP_ANONYMOUS, >> -1, 0); >> if (pages[i] == MAP_FAILED) >> return (EXIT_FAILURE); >> } >> >> ret = set_mempolicy(MPOL_DEFAULT, NULL, 0); >> if (ret < 0) >> return (EXIT_FAILURE); >> >> int *nodes = malloc(sizeof(int) * num_pages); >> int *status = malloc(sizeof(int) * num_pages); >> for (int i = 0; i < num_pages; ++i) { >> nodes[i] = node_id; >> status[i] = 0xd0; /* simulate garbage values */ >> } >> >> ret = move_pages(0, num_pages, pages, nodes, status, MPOL_MF_MOVE); >> printf("move_pages: %ld\n", ret); >> for (int i = 0; i < num_pages; ++i) >> printf("status[%d] = %d\n", i, status[i]); >> } >> ---8<--- >> >> Then running the program would return nonsense status values: >> $ ./move_pages_bug >> move_pages: 0 >> status[0] = 208 >> status[1] = 208 >> status[2] = 208 >> status[3] = 208 >> status[4] = 208 >> status[5] = 208 >> status[6] = 208 >> status[7] = 208 >> >> This is because the status is not set if the page is already on the >> target node, but move_pages() should return valid status as long as it >> succeeds. The valid status may be errno or node id. >> >> We can't simply initialize status array to zero since the pages may be >> not on node 0. Fix it by updating status with node id which the page is >> already on. >> >> Fixes: a49bd4d71637 ("mm, numa: rework do_pages_move") >> Reported-by: Felix Abecassis >> Tested-by: Felix Abecassis >> Suggested-by: Michal Hocko >> Cc: John Hubbard >> Cc: Christoph Lameter >> Cc: Vlastimil Babka >> Cc: Mel Gorman >> Cc: 4.17+ >> Signed-off-by: Yang Shi >> --- >> v3: * Adopted the suggestion from Michal. >> v2: * Correted the return value when add_page_for_migration() returns 1. >> >> mm/migrate.c | 24 ++++++++++++++++++------ >> 1 file changed, 18 insertions(+), 6 deletions(-) >> >> diff --git a/mm/migrate.c b/mm/migrate.c >> index a8f87cb..9c172f4 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -1512,9 +1512,11 @@ static int do_move_pages_to_node(struct mm_struct *mm, >> /* >> * Resolves the given address to a struct page, isolates it from the LRU and >> * puts it to the given pagelist. >> - * Returns -errno if the page cannot be found/isolated or 0 when it has been >> - * queued or the page doesn't need to be migrated because it is already on >> - * the target node >> + * Returns: >> + * errno - if the page cannot be found/isolated >> + * 0 - when it doesn't have to be migrated because it is already on the >> + * target node >> + * 1 - when it has been queued >> */ >> static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, >> int node, struct list_head *pagelist, bool migrate_all) >> @@ -1553,7 +1555,7 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, >> if (PageHuge(page)) { >> if (PageHead(page)) { >> isolate_huge_page(page, pagelist); >> - err = 0; >> + err = 1; >> } >> } else { >> struct page *head; >> @@ -1563,7 +1565,7 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, >> if (err) >> goto out_putpage; >> >> - err = 0; >> + err = 1; >> list_add_tail(&head->lru, pagelist); >> mod_node_page_state(page_pgdat(head), >> NR_ISOLATED_ANON + page_is_file_cache(head), >> @@ -1578,6 +1580,7 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, >> put_page(page); >> out: >> up_read(&mm->mmap_sem); >> + >> return err; >> } >> >> @@ -1640,8 +1643,17 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, >> */ >> err = add_page_for_migration(mm, addr, current_node, >> &pagelist, flags & MPOL_MF_MOVE_ALL); >> - if (!err) >> + >> + /* The page is already on the target node */ >> + if (!err) { >> + err = store_status(status, i, current_node, 1); >> + if (err) >> + goto out_flush; >> continue; >> + /* The page is successfully queued */ > Nit: could you move this comment down one line, so that it's clear that it > applies to the "else" branch? Like this: > > } else if (err > 0) { > /* The page is successfully queued for migration */ > continue; > } Sure. > > >> + } else if (err > 0) { >> + continue; >> + } >> >> err = store_status(status, i, err, 1); >> if (err) >> > Also agree with Christopher's requests, but all of these don't affect the > correct operation of the patch, so you can add: > > Reviewed-by: John Hubbard > > thanks,