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=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 05E05C43603 for ; Wed, 4 Dec 2019 22:54:20 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id AD73E206DB for ; Wed, 4 Dec 2019 22:54:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="k6HK0wB7" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AD73E206DB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=nvidia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 5A4266B0CF9; Wed, 4 Dec 2019 17:54:19 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 554E56B0CFA; Wed, 4 Dec 2019 17:54:19 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 444026B0CFB; Wed, 4 Dec 2019 17:54:19 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0185.hostedemail.com [216.40.44.185]) by kanga.kvack.org (Postfix) with ESMTP id 2D9F76B0CF9 for ; Wed, 4 Dec 2019 17:54:19 -0500 (EST) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id BC4A38051831 for ; Wed, 4 Dec 2019 22:54:18 +0000 (UTC) X-FDA: 76228964196.26.pig23_84bf38e2ba61 X-HE-Tag: pig23_84bf38e2ba61 X-Filterd-Recvd-Size: 7133 Received: from hqnvemgate25.nvidia.com (hqnvemgate25.nvidia.com [216.228.121.64]) by imf35.hostedemail.com (Postfix) with ESMTP for ; Wed, 4 Dec 2019 22:54:16 +0000 (UTC) Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate25.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Wed, 04 Dec 2019 14:54:11 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Wed, 04 Dec 2019 14:54:15 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Wed, 04 Dec 2019 14:54:15 -0800 Received: from nvidia.com (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Wed, 4 Dec 2019 22:54:14 +0000 Date: Wed, 4 Dec 2019 14:54:13 -0800 From: Felix Abecassis To: Yang Shi CC: Linux MM , Andrew Morton Subject: Re: bug: move_pages(2) does not udpate "status" if no pages are moved Message-ID: <20191204225413.GA625719@nvidia.com> References: MIME-Version: 1.0 In-Reply-To: X-NVConfidentiality: public User-Agent: Mutt/1.12.2 (2019-09-21) X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL111.nvidia.com (172.20.187.18) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1575500051; bh=N5Vi6nCW808ntmOff98ybKBhPTgm0uLPekS5XgZHA98=; h=X-PGP-Universal:Date:From:To:CC:Subject:Message-ID:References: MIME-Version:In-Reply-To:X-NVConfidentiality:User-Agent: X-Originating-IP:X-ClientProxiedBy:Content-Type: Content-Disposition; b=k6HK0wB7PDjUiuV1QyO2FKTK2I1vaLLrCnMuUCU8n6b9T2zq0dNizDBKjDqVUclST Y7lYFkZEhDCZjN4z3yOIcXQqvcSxYqMF6CmmVv0zKueEMyCy/rlX19TSXxUMxMN4GP /pdy+A+5QosvhwiTP8lKe7jgP7pJLhDQZibdz6ZhI8xyeiTiKRMEOyyq4UNj8XV2yb pCG54uZmBeqZ5/uAxBe1qDKasIWtPS0iHc49EkOUwhTTXqWgwsm2Z5odg+9WZl4bAE XIx1Pup36trMZA7mAxAdmS36RnE1rHyp2f8sFmIwfrrWrkbPh1TnHw9Zu9SyObR7cs i2QWK/hpottNA== 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 04, 2019 at 12:17:59PM -0800, Yang Shi wrote: > 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; > Thanks! I have tested this patch on top of 5.4-rc8, and I can comfirm it fixes this particular test case. > > > > 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, > >