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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7C5CAC433EF for ; Wed, 13 Jul 2022 08:30:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235345AbiGMIak (ORCPT ); Wed, 13 Jul 2022 04:30:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40496 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235238AbiGMIaf (ORCPT ); Wed, 13 Jul 2022 04:30:35 -0400 Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3F74071BE0 for ; Wed, 13 Jul 2022 01:30:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1657701035; x=1689237035; h=from:to:cc:subject:references:date:in-reply-to: message-id:mime-version; bh=YQUSBazFo/c4fVEPXFT3RG1PGjmSxbf7eA6p2HwqTTo=; b=GUTfm0VASzTQ05aMMkq2k7jDE5CaolM1Z6Qr1L9mucIGJ4Fm5kMqmebZ jQubqqeiQf0M/SsISnMjx+A83nommhqxsu5/gK5JQJTufAvhonhg355BY 9A7/3lrvit4Pyj0C64tEoK0hTcUezajeiP6fHHox+XOXQzAW/+Ds0EhjS E6wwyOddTJjYdELAbZ6oI1yL6eVgpdyhW4EkQ4QSGsOlE52Pvy0pHGcrK owtfBvljnEB4C17vyHQzOkkNGQenCPTwx5BtW9DVhLe3RG/ZfnypbHfaY 2RzLGC8jrA/KN2mhbcDTFq31HHZf4VNdM2Et5uitOKzPT/06EoYJJcRM+ Q==; X-IronPort-AV: E=McAfee;i="6400,9594,10406"; a="283905557" X-IronPort-AV: E=Sophos;i="5.92,267,1650956400"; d="scan'208";a="283905557" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Jul 2022 01:30:34 -0700 X-IronPort-AV: E=Sophos;i="5.92,267,1650956400"; d="scan'208";a="570535384" Received: from yhuang6-desk2.sh.intel.com (HELO yhuang6-desk2.ccr.corp.intel.com) ([10.239.13.94]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Jul 2022 01:30:32 -0700 From: "Huang, Ying" To: Oscar Salvador Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Baolin Wang , Zi Yan , Yang Shi Subject: Re: [PATCH -V2 5/7] migrate_pages(): fix failure counting for THP on -ENOSYS References: <20220711084948.274787-1-ying.huang@intel.com> <20220711084948.274787-6-ying.huang@intel.com> Date: Wed, 13 Jul 2022 16:30:27 +0800 In-Reply-To: (Oscar Salvador's message of "Mon, 11 Jul 2022 14:26:20 +0200") Message-ID: <87wnch4dp8.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Oscar Salvador writes: > On Mon, Jul 11, 2022 at 04:49:46PM +0800, Huang Ying wrote: >> If THP or hugetlbfs page migration isn't supported, unmap_and_move() >> or unmap_and_move_huge_page() will return -ENOSYS. For THP, splitting >> will be tried, but if splitting doesn't succeed, the THP will be left >> in "from" list wrongly. If some other pages are retried, the THP >> migration failure will counted again. This is fixed via moving the >> failure THP from "from" to "ret_pages". >> >> Another issue of the original code is that the unsupported failure >> processing isn't consistent between THP and hugetlbfs page. Make them >> consistent in this patch to make the code easier to be understood too. >> >> Signed-off-by: "Huang, Ying" >> Fixes: 5984fabb6e82 ("mm: move_pages: report the number of non-attempted pages") >> Reviewed-by: Baolin Wang >> Cc: Zi Yan >> Cc: Yang Shi >> --- >> mm/migrate.c | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/mm/migrate.c b/mm/migrate.c >> index 4bceba143db0..8cce73b7c046 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -1192,10 +1192,8 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, >> * tables or check whether the hugepage is pmd-based or not before >> * kicking migration. >> */ >> - if (!hugepage_migration_supported(page_hstate(hpage))) { >> - list_move_tail(&hpage->lru, ret); >> + if (!hugepage_migration_supported(page_hstate(hpage))) >> return -ENOSYS; >> - } >> >> if (page_count(hpage) == 1) { >> /* page was freed from under us. So we are done. */ >> @@ -1392,6 +1390,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, >> * page will be put back >> * -EAGAIN: stay on the from list >> * -ENOMEM: stay on the from list >> + * -ENOSYS: stay on the from list >> * Other errno: put on ret_pages list then splice to >> * from list >> */ >> @@ -1421,6 +1420,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page, >> } >> >> nr_failed_pages += nr_subpages; >> + list_move_tail(&page->lru, &ret_pages); > > I must be missing something, but migrate_pages() calls unmap_and_move_huge_page() > with ret being ret_pages, so > > list_move_tail(&hpage->lru, ret) == list_move_tail(&page->lru, &ret_pages) > > Yet, you say "This is fixed via moving the failure THP from "from" to "ret_pages"". > /me confused. To make it consistent between hugetlb page and THP/normal page, I have revised the unmap_and_move_huge_page() via deleting the list_move_tail() there for ENOSYS. After that, we move the hugetlb page and THP/normal page in the same way in migrate_pages(). Best Regards, Huang, Ying