From patchwork Thu Dec 10 16:00:20 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vlastimil Babka X-Patchwork-Id: 11965203 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 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 freed. SLAB and SLUB use the slab_cache field which is in union with mapping, but 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_cache 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 allocator doesn't care about those). While using the 'mapping' name would automagically keep the code correct if the unions in struct page changed, such changes should be done consciously and needed changes evaluated - the comment should help with that. Signed-off-by: Vlastimil Babka Acked-by: David Rientjes Acked-by: Joonsoo Kim --- 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 *cachep, struct page *page) __ClearPageSlabPfmemalloc(page); __ClearPageSlab(page); page_mapcount_reset(page); - page->mapping = NULL; + /* In union with page->mapping where page allocator expects NULL */ + page->slab_cache = NULL; if (current->reclaim_state) current->reclaim_state->reclaimed_slab += 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, struct page *page) __ClearPageSlabPfmemalloc(page); __ClearPageSlab(page); - - page->mapping = NULL; + /* In union with page->mapping where page allocator expects NULL */ + page->slab_cache = NULL; if (current->reclaim_state) current->reclaim_state->reclaimed_slab += pages; unaccount_slab_page(page, order, s);