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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 8ABEBC3F2D0 for ; Fri, 28 Feb 2020 03:38:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6B5E4246A2 for ; Fri, 28 Feb 2020 03:38:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730829AbgB1Dil (ORCPT ); Thu, 27 Feb 2020 22:38:41 -0500 Received: from mga09.intel.com ([134.134.136.24]:36522 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730807AbgB1Dik (ORCPT ); Thu, 27 Feb 2020 22:38:40 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 27 Feb 2020 19:38:40 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,493,1574150400"; d="scan'208";a="232107356" Received: from yhuang-dev.sh.intel.com ([10.239.159.23]) by orsmga008.jf.intel.com with ESMTP; 27 Feb 2020 19:38:37 -0800 From: "Huang, Ying" To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Huang Ying , Dave Hansen , David Hildenbrand , Mel Gorman , Vlastimil Babka , Zi Yan , Michal Hocko , Minchan Kim , Johannes Weiner , Hugh Dickins Subject: [RFC 1/3] mm, migrate: Check return value of try_to_unmap() Date: Fri, 28 Feb 2020 11:38:17 +0800 Message-Id: <20200228033819.3857058-2-ying.huang@intel.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200228033819.3857058-1-ying.huang@intel.com> References: <20200228033819.3857058-1-ying.huang@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Huang Ying During the page migration, try_to_unmap() is called to replace the page table entries with the migration entries. Now its return value is ignored, that is generally OK in most cases. But in theory, it's possible that try_to_unmap() return false (failure) for the page migration after arch_unmap_one() is called in unmap code. Even if without arch_unmap_one(), it makes code more robust for the future code changing to check the return value. Known issue: I don't know what is the appropriate error code for try_to_unmap() failure. Whether EIO is OK? Signed-off-by: "Huang, Ying" Cc: Dave Hansen Cc: David Hildenbrand Cc: Mel Gorman Cc: Vlastimil Babka Cc: Zi Yan Cc: Michal Hocko Cc: Minchan Kim Cc: Johannes Weiner Cc: Hugh Dickins --- mm/migrate.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index 3900044cfaa6..981f8374a6ef 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1116,8 +1116,11 @@ static int __unmap_and_move(struct page *page, struct page *newpage, /* Establish migration ptes */ VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma, page); - try_to_unmap(page, - TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); + if (!try_to_unmap(page, + TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS)) { + rc = -EIO; + goto out_unlock_both; + } page_was_mapped = 1; } @@ -1337,8 +1340,11 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, goto put_anon; if (page_mapped(hpage)) { - try_to_unmap(hpage, - TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); + if (!try_to_unmap(hpage, + TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS)) { + rc = -EIO; + goto unlock_both; + } page_was_mapped = 1; } @@ -1349,6 +1355,7 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, remove_migration_ptes(hpage, rc == MIGRATEPAGE_SUCCESS ? new_hpage : hpage, false); +unlock_both: unlock_page(new_hpage); put_anon: @@ -2558,8 +2565,7 @@ static void migrate_vma_unmap(struct migrate_vma *migrate) continue; if (page_mapped(page)) { - try_to_unmap(page, flags); - if (page_mapped(page)) + if (!try_to_unmap(page, flags)) goto restore; } -- 2.25.0