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=-3.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 CFEE8C43603 for ; Wed, 4 Dec 2019 20:18:13 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 743F1215B2 for ; Wed, 4 Dec 2019 20:18:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="uxb5G/Bi" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 743F1215B2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 15F266B0C5D; Wed, 4 Dec 2019 15:18:13 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 10E3C6B0C5E; Wed, 4 Dec 2019 15:18:13 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 04C346B0C5F; Wed, 4 Dec 2019 15:18:13 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id E2EA66B0C5D for ; Wed, 4 Dec 2019 15:18:12 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 8DC4B180AD801 for ; Wed, 4 Dec 2019 20:18:12 +0000 (UTC) X-FDA: 76228570824.16.scarf41_64b01c14b7a44 X-HE-Tag: scarf41_64b01c14b7a44 X-Filterd-Recvd-Size: 6882 Received: from mail-ed1-f68.google.com (mail-ed1-f68.google.com [209.85.208.68]) by imf33.hostedemail.com (Postfix) with ESMTP for ; Wed, 4 Dec 2019 20:18:11 +0000 (UTC) Received: by mail-ed1-f68.google.com with SMTP id v16so561033edy.6 for ; Wed, 04 Dec 2019 12:18:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=qL0biBiXYq1IzfUW4cJ/JxXOSsAld9Y1/JxBBtCtQUw=; b=uxb5G/BikA3fTjlj5FDaw9hWWYq2zw7O51YE4idyadB4HEexOlDnuu3KL87MlgW1zP kkdZZ2qw36tTAY5M3omsdR/K2h82JJC0j4emISNOx/EOXmooRoTRD+xLzE4SKg0L2pWg i7LOuIjLl2MdpA0QXT2mUpbUZPssQox6shKt0WQE+cWIizw1OUClMmzxS4b2DVbI3NYU uXLWILeFK8eHdYfAoyIXHEOOOaRsYrl8hYRoM1NOolazW9MwdeNvcQhdEfeykPiaayX9 zmuDg8e+luPDnQovIlZURi6GqFA8vtYciATIRbj1iqg00LzOhJwi4Sf9zebhN9nVE1BS Kxtg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=qL0biBiXYq1IzfUW4cJ/JxXOSsAld9Y1/JxBBtCtQUw=; b=fYcWOwi6kexEgPecCNmRe7c5Xmi9Tu79iLOioXVyWoOQwTEp9l5TpipNrvPnY2c71h C+e6OM8rWCyUDynM3CdtSJ2yR5piz3LZxj8xF1QGElR2lhRoVZgCK/FJixXycbFZaAcX +rTmesNmxuwF8yogjOz5F0TjCKf4XWRY936OUhllg2VDgDddOt/uGADOguh3cTnF8y5+ AoVtexOlIGU+ZRCl1QftMpgZD+gZLwlCiZvGKIZ2AYcwmst+up3cdfLXRb5c/Rj/kely iQzmLPmqzT5s1zR/pvGPCLIFhNB5MXMpz3SN9bqpJu+Q8odxLP8YctQtW0TIFi09AD9M jySA== X-Gm-Message-State: APjAAAVyOZjKJuOJzjCD0LfUxjnZlBhGDjzIkFzug0cNPSuuri3CeeTG XNo/qpmQGFtOV7WvkPJUp0p07gd/vhKOdQ8tJaUAhFUM8ek= X-Google-Smtp-Source: APXvYqwLjJrkej7ITkPS47o/G2b6fOo26lkiK77Qy7aDv5QhGtlozkeKfKMP7xkqmHIdH8BE2iUbajjbh3r6sZn+3AQ= X-Received: by 2002:aa7:c159:: with SMTP id r25mr6171731edp.42.1575490690595; Wed, 04 Dec 2019 12:18:10 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Yang Shi Date: Wed, 4 Dec 2019 12:17:59 -0800 Message-ID: Subject: Re: bug: move_pages(2) does not udpate "status" if no pages are moved To: Felix Abecassis Cc: Linux MM , Andrew Morton Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Dec 4, 2019 at 11:01 AM Felix Abecassis wrote: > > Hello all, > > On kernel 5.3, when using the move_pages syscall (wrapped by libnuma) and all > pages happen to be on the right node already, this function returns 0 but the > "status" array is not updated. This array potentially contains garbage values > (e.g. from malloc(3)), and I don't see a way to detect this. > > Looking at the kernel code, we are probably exiting do_pages_move here: > out_flush: > if (list_empty(&pagelist)) > return err; May you please give the below patch a try? I just did build test. diff --git a/mm/migrate.c b/mm/migrate.c index a8f87cb..f2f1279 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1517,7 +1517,8 @@ static int do_move_pages_to_node(struct mm_struct *mm, * the target node */ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, - int node, struct list_head *pagelist, bool migrate_all) + int node, struct list_head *pagelist, bool migrate_all, + int __user *status, int start) { struct vm_area_struct *vma; struct page *page; @@ -1543,8 +1544,10 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr, goto out; err = 0; - if (page_to_nid(page) == node) + if (page_to_nid(page) == node) { + err = store_status(status, start, node, 1); goto out_putpage; + } err = -EACCES; if (page_mapcount(page) > 1 && !migrate_all) @@ -1639,7 +1642,9 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, * report them via status */ err = add_page_for_migration(mm, addr, current_node, - &pagelist, flags & MPOL_MF_MOVE_ALL); + &pagelist, flags & MPOL_MF_MOVE_ALL, status, + i); + if (!err) continue; > > Here is a sample C program to reproduce the problem: > /* $ gcc move_pages_bug.c -lnuma -o move_pages_bug */ > > #define _DEFAULT_SOURCE > #include > > #include > #include > #include > #include > > 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]); > } > > And here is a sample output showing the "garbage" 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 > > Note that passing NULL as the "nodes" argument works as expected here. > > Also, it seems that it's the last "run-length" of pages on the right node(s) > that triggers this problem, e.g. if I add "nodes[0] = nodes[1] = 0", then the > output becomes: > $ ./move_pages_bug > move_pages: 0 > status[0] = 0 > status[1] = 0 > status[2] = 208 > status[3] = 208 > status[4] = 208 > status[5] = 208 > status[6] = 208 > status[7] = 208 > > And with just "nodes[7] = 0;", the first run-length of pages gets assigned > correctly: > $ ./move_pages_bug > move_pages: 0 > status[0] = 1 > status[1] = 1 > status[2] = 1 > status[3] = 1 > status[4] = 1 > status[5] = 1 > status[6] = 1 > status[7] = 0 > > > Thank you, >