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[209.132.183.28]) by mx.google.com with ESMTPS id u11si6884869qvf.139.2019.06.24.00.28.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 24 Jun 2019 00:28:56 -0700 (PDT) Received-SPF: pass (google.com: domain of ming.lei@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of ming.lei@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=ming.lei@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 56D955AFF8; Mon, 24 Jun 2019 07:28:50 +0000 (UTC) Received: from ming.t460p (ovpn-8-18.pek2.redhat.com [10.72.8.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DC51B5C1B5; Mon, 24 Jun 2019 07:28:36 +0000 (UTC) Date: Mon, 24 Jun 2019 15:28:31 +0800 From: Ming Lei To: "Huang, Ying" Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko , Johannes Weiner , Hugh Dickins , Minchan Kim , Rik van Riel , Daniel Jordan Subject: Re: [PATCH -mm] mm, swap: Fix THP swap out Message-ID: <20190624072830.GA10539@ming.t460p> References: <20190624022336.12465-1-ying.huang@intel.com> <20190624033438.GB6563@ming.t460p> <87imsvbnie.fsf@yhuang-dev.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87imsvbnie.fsf@yhuang-dev.intel.com> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Mon, 24 Jun 2019 07:28:55 +0000 (UTC) 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 Mon, Jun 24, 2019 at 12:44:41PM +0800, Huang, Ying wrote: > 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. Then we can pass 1 to bio_alloc(), together with single bio_add_page() for making the code more readable. thanks, Ming