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=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 21FEDC433DB for ; Mon, 18 Jan 2021 11:51:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D10E620756 for ; Mon, 18 Jan 2021 11:51:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391075AbhARLvF (ORCPT ); Mon, 18 Jan 2021 06:51:05 -0500 Received: from mail.kernel.org ([198.145.29.99]:35640 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390537AbhARLkI (ORCPT ); Mon, 18 Jan 2021 06:40:08 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2493C2223E; Mon, 18 Jan 2021 11:39:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1610969991; bh=KKV/3+xerDS256hNnw8+B6mkS7/OTuoWitYAw9FvDIM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=c/Ek4YDYnna6sAUG8O4IhXye7PC95sEeQW1Q9SDhsLi3dxfzBUzU/ViN4mhzHAS8I +ZM81GghGlne9bDn9YqKKJWSROa274pd3GS1BautHqlotN9F94760+8t88BZuvV2mf +MnWolvetq393O0vaVFdEO3pUNM7pJiNbm3gl7Z0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jann Horn , David Rientjes , Joonsoo Kim , Christoph Lameter , Pekka Enberg , Andrew Morton , Linus Torvalds Subject: [PATCH 5.4 68/76] mm, slub: consider rest of partial list if acquire_slab() fails Date: Mon, 18 Jan 2021 12:35:08 +0100 Message-Id: <20210118113344.220384656@linuxfoundation.org> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210118113340.984217512@linuxfoundation.org> References: <20210118113340.984217512@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jann Horn commit 8ff60eb052eeba95cfb3efe16b08c9199f8121cf upstream. acquire_slab() fails if there is contention on the freelist of the page (probably because some other CPU is concurrently freeing an object from the page). In that case, it might make sense to look for a different page (since there might be more remote frees to the page from other CPUs, and we don't want contention on struct page). However, the current code accidentally stops looking at the partial list completely in that case. Especially on kernels without CONFIG_NUMA set, this means that get_partial() fails and new_slab_objects() falls back to new_slab(), allocating new pages. This could lead to an unnecessary increase in memory fragmentation. Link: https://lkml.kernel.org/r/20201228130853.1871516-1-jannh@google.com Fixes: 7ced37197196 ("slub: Acquire_slab() avoid loop") Signed-off-by: Jann Horn Acked-by: David Rientjes Acked-by: Joonsoo Kim Cc: Christoph Lameter Cc: Pekka Enberg Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/slub.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/slub.c +++ b/mm/slub.c @@ -1887,7 +1887,7 @@ static void *get_partial_node(struct kme t = acquire_slab(s, n, page, object == NULL, &objects); if (!t) - break; + continue; /* cmpxchg raced */ available += objects; if (!object) {