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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 DA6E8C4361B for ; Thu, 10 Dec 2020 16:00:45 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6502623E25 for ; Thu, 10 Dec 2020 16:00:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6502623E25 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id ADDB06B0036; Thu, 10 Dec 2020 11:00:44 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A8D8B6B005D; Thu, 10 Dec 2020 11:00:44 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9A26C6B0068; Thu, 10 Dec 2020 11:00:44 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0038.hostedemail.com [216.40.44.38]) by kanga.kvack.org (Postfix) with ESMTP id 7F99F6B0036 for ; Thu, 10 Dec 2020 11:00:44 -0500 (EST) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 36B7D180AD83A for ; Thu, 10 Dec 2020 16:00:44 +0000 (UTC) X-FDA: 77577835608.22.glue22_3705932273f9 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin22.hostedemail.com (Postfix) with ESMTP id CDD5618038C56 for ; Thu, 10 Dec 2020 16:00:36 +0000 (UTC) X-HE-Tag: glue22_3705932273f9 X-Filterd-Recvd-Size: 2928 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf28.hostedemail.com (Postfix) with ESMTP for ; Thu, 10 Dec 2020 16:00:35 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id A4ABFAE2E; Thu, 10 Dec 2020 16:00:34 +0000 (UTC) From: Vlastimil Babka To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Matthew Wilcox , Vlastimil Babka Subject: [PATCH] mm, slab, slub: clear the slab_cache field when freeing page Date: Thu, 10 Dec 2020 17:00:20 +0100 Message-Id: <20201210160020.21562-1-vbabka@suse.cz> X-Mailer: git-send-email 2.29.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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: The page allocator expects that page->mapping is NULL for a page being fr= eed. SLAB and SLUB use the slab_cache field which is in union with mapping, bu= t before freeing the page, the field is referenced with the "mapping" name = when set to NULL. It's IMHO more correct (albeit functionally the same) to use the slab_cac= he name as that's the field we use in SL*B, and document why we clear it in = a comment (we don't clear fields such as s_mem or freelist, as page allocat= or doesn't care about those). While using the 'mapping' name would automagic= ally keep the code correct if the unions in struct page changed, such changes = should be done consciously and needed changes evaluated - the comment should hel= p with that. Signed-off-by: Vlastimil Babka --- mm/slab.c | 3 ++- mm/slub.c | 4 ++-- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/mm/slab.c b/mm/slab.c index 72b6743bdccf..b667f03095f1 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -1399,7 +1399,8 @@ static void kmem_freepages(struct kmem_cache *cache= p, struct page *page) __ClearPageSlabPfmemalloc(page); __ClearPageSlab(page); page_mapcount_reset(page); - page->mapping =3D NULL; + /* In union with page->mapping where page allocator expects NULL */ + page->slab_cache =3D NULL; =20 if (current->reclaim_state) current->reclaim_state->reclaimed_slab +=3D 1 << order; diff --git a/mm/slub.c b/mm/slub.c index d3406ef65863..81c22f4c7e63 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1836,8 +1836,8 @@ static void __free_slab(struct kmem_cache *s, struc= t page *page) =20 __ClearPageSlabPfmemalloc(page); __ClearPageSlab(page); - - page->mapping =3D NULL; + /* In union with page->mapping where page allocator expects NULL */ + page->slab_cache =3D NULL; if (current->reclaim_state) current->reclaim_state->reclaimed_slab +=3D pages; unaccount_slab_page(page, order, s); --=20 2.29.2