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=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 2EE98C43613 for ; Mon, 24 Jun 2019 04:44:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0BB1A2133F for ; Mon, 24 Jun 2019 04:44:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727869AbfFXEoo (ORCPT ); Mon, 24 Jun 2019 00:44:44 -0400 Received: from mga01.intel.com ([192.55.52.88]:20793 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726343AbfFXEoo (ORCPT ); Mon, 24 Jun 2019 00:44:44 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Jun 2019 21:44:44 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.63,411,1557212400"; d="scan'208";a="244579823" Received: from yhuang-dev.sh.intel.com (HELO yhuang-dev) ([10.239.159.29]) by orsmga001.jf.intel.com with ESMTP; 23 Jun 2019 21:44:41 -0700 From: "Huang\, Ying" To: Ming Lei Cc: Andrew Morton , , , Michal Hocko , "Johannes Weiner" , Hugh Dickins , Minchan Kim , Rik van Riel , Daniel Jordan Subject: Re: [PATCH -mm] mm, swap: Fix THP swap out References: <20190624022336.12465-1-ying.huang@intel.com> <20190624033438.GB6563@ming.t460p> Date: Mon, 24 Jun 2019 12:44:41 +0800 In-Reply-To: <20190624033438.GB6563@ming.t460p> (Ming Lei's message of "Mon, 24 Jun 2019 11:34:40 +0800") Message-ID: <87imsvbnie.fsf@yhuang-dev.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Ming Lei writes: > Hi Huang Ying, > > On Mon, Jun 24, 2019 at 10:23:36AM +0800, Huang, Ying wrote: >> From: Huang Ying >> >> 0-Day test system reported some OOM regressions for several >> THP (Transparent Huge Page) swap test cases. These regressions are >> bisected to 6861428921b5 ("block: always define BIO_MAX_PAGES as >> 256"). In the commit, BIO_MAX_PAGES is set to 256 even when THP swap >> is enabled. So the bio_alloc(gfp_flags, 512) in get_swap_bio() may >> fail when swapping out THP. That causes the OOM. >> >> As in the patch description of 6861428921b5 ("block: always define >> BIO_MAX_PAGES as 256"), THP swap should use multi-page bvec to write >> THP to swap space. So the issue is fixed via doing that in >> get_swap_bio(). >> >> BTW: I remember I have checked the THP swap code when >> 6861428921b5 ("block: always define BIO_MAX_PAGES as 256") was merged, >> and thought the THP swap code needn't to be changed. But apparently, >> I was wrong. I should have done this at that time. >> >> Fixes: 6861428921b5 ("block: always define BIO_MAX_PAGES as 256") >> Signed-off-by: "Huang, Ying" >> Cc: Ming Lei >> Cc: Michal Hocko >> Cc: Johannes Weiner >> Cc: Hugh Dickins >> Cc: Minchan Kim >> Cc: Rik van Riel >> Cc: Daniel Jordan >> --- >> mm/page_io.c | 7 ++----- >> 1 file changed, 2 insertions(+), 5 deletions(-) >> >> diff --git a/mm/page_io.c b/mm/page_io.c >> index 2e8019d0e048..4ab997f84061 100644 >> --- a/mm/page_io.c >> +++ b/mm/page_io.c >> @@ -29,10 +29,9 @@ >> static struct bio *get_swap_bio(gfp_t gfp_flags, >> struct page *page, bio_end_io_t end_io) >> { >> - int i, nr = hpage_nr_pages(page); >> struct bio *bio; >> >> - bio = bio_alloc(gfp_flags, nr); >> + bio = bio_alloc(gfp_flags, 1); >> if (bio) { >> struct block_device *bdev; >> >> @@ -41,9 +40,7 @@ static struct bio *get_swap_bio(gfp_t gfp_flags, >> bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9; >> bio->bi_end_io = end_io; >> >> - for (i = 0; i < nr; i++) >> - bio_add_page(bio, page + i, PAGE_SIZE, 0); > > bio_add_page() supposes to work, just wondering why it doesn't recently. Yes. Just checked and bio_add_page() works too. I should have used that. The problem isn't bio_add_page(), but bio_alloc(), because nr == 512 > 256, mempool cannot be used during swapout, so swapout will fail. Best Regards, Huang, Ying > Could you share me one test case for reproducing it? > >> - VM_BUG_ON(bio->bi_iter.bi_size != PAGE_SIZE * nr); >> + __bio_add_page(bio, page, PAGE_SIZE * hpage_nr_pages(page), 0); >> } >> return bio; > > Actually the above code can be simplified as: > > diff --git a/mm/page_io.c b/mm/page_io.c > index 2e8019d0e048..c20b4189d0a1 100644 > --- a/mm/page_io.c > +++ b/mm/page_io.c > @@ -29,7 +29,7 @@ > static struct bio *get_swap_bio(gfp_t gfp_flags, > struct page *page, bio_end_io_t end_io) > { > - int i, nr = hpage_nr_pages(page); > + int nr = hpage_nr_pages(page); > struct bio *bio; > > bio = bio_alloc(gfp_flags, nr); > @@ -41,8 +41,7 @@ static struct bio *get_swap_bio(gfp_t gfp_flags, > bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9; > bio->bi_end_io = end_io; > > - for (i = 0; i < nr; i++) > - bio_add_page(bio, page + i, PAGE_SIZE, 0); > + bio_add_page(bio, page, PAGE_SIZE * nr, 0); > VM_BUG_ON(bio->bi_iter.bi_size != PAGE_SIZE * nr); > } > return bio; > > > Thanks, > Ming