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=-17.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 EC190C433E0 for ; Mon, 15 Mar 2021 17:57:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 60B8064F09 for ; Mon, 15 Mar 2021 17:57:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 60B8064F09 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CFE726B0036; Mon, 15 Mar 2021 13:57:02 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id CD62F6B006C; Mon, 15 Mar 2021 13:57:02 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B9D7F6B0070; Mon, 15 Mar 2021 13:57:02 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0091.hostedemail.com [216.40.44.91]) by kanga.kvack.org (Postfix) with ESMTP id 9CB436B0036 for ; Mon, 15 Mar 2021 13:57:02 -0400 (EDT) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 3AF065821 for ; Mon, 15 Mar 2021 17:57:02 +0000 (UTC) X-FDA: 77922864684.21.D6C8B7C Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf05.hostedemail.com (Postfix) with ESMTP id 4D019E162189 for ; Mon, 15 Mar 2021 17:32:10 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id BE55F64E98; Mon, 15 Mar 2021 17:32:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1615829527; bh=VRcbQL7CvY6cs5rG3WUG31fwN9zEEEuuniKBvXrs38c=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=ITjF77TLcgpBt5MuUWlr0DwatVKlFdMISr/3LmxHyhyFvMKGp6gQn80vGywiW0w31 FpvxijhAGClviF7uDoWK4gaNArg84LppRmlLJXz+bXRoR+3VI0gmSLvMzM1Jm+MI2k dg5X5Vzjqe7zn6MVXxbrVduAvjWqo4i+ifgAhjpEuiRoSMYr3tJI5wEWwJTNa/HqEi 0OCY1UxilLOOXcKbekTTfRzdVb+ikDVwpmIBG4uAdnDY+8YX6CRPv6nNkwRmeqlVBM iNLMRzVpYdBXNd8lOlY0wv4gXJ3TXHPQLHcGR2m8m/W9g52M3h5dKTLxxL6HXZU8aJ 94TUcdCYK9HNg== Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 67894352261C; Mon, 15 Mar 2021 10:32:07 -0700 (PDT) Date: Mon, 15 Mar 2021 10:32:07 -0700 From: "Paul E. McKenney" To: Vlastimil Babka Cc: David Rientjes , Andrew Morton , Christoph Lameter , Pekka Enberg , Joonsoo Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org, David Sterba , Oliver Glitta Subject: Re: [PATCH] [PATCH] mm, slub: enable slub_debug static key when creating cache with explicit debug flags Message-ID: <20210315173207.GN2696@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20210315153415.24404-1-vbabka@suse.cz> <2d80f81a-ed85-a36f-6527-b75da3ae209e@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-Stat-Signature: ntrsrpszjmtz55ijghnqs3rkshys9gy4 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 4D019E162189 Received-SPF: none (kernel.org>: No applicable sender policy available) receiver=imf05; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1615829530-349465 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, Mar 15, 2021 at 06:28:42PM +0100, Vlastimil Babka wrote: > On 3/15/21 6:16 PM, David Rientjes wrote: > > On Mon, 15 Mar 2021, Vlastimil Babka wrote: > > > >> Commit ca0cab65ea2b ("mm, slub: introduce static key for slub_debug()") > >> introduced a static key to optimize the case where no debugging is enabled for > >> any cache. The static key is enabled when slub_debug boot parameter is passed, > >> or CONFIG_SLUB_DEBUG_ON enabled. > >> > >> However, some caches might be created with one or more debugging flags > >> explicitly passed to kmem_cache_create(), and the commit missed this. Thus the > >> debugging functionality would not be actually performed for these caches unless > >> the static key gets enabled by boot param or config. > >> > >> This patch fixes it by checking for debugging flags passed to > >> kmem_cache_create() and enabling the static key accordingly. > >> > >> Note such explicit debugging flags should not be used outside of debugging and > >> testing as they will now enable the static key globally. btrfs_init_cachep() > >> creates a cache with SLAB_RED_ZONE but that's a mistake that's being corrected > >> [1]. rcu_torture_stats() creates a cache with SLAB_STORE_USER, but that is a > >> testing module so it's OK and will start working as intended after this patch. > >> > >> Also note that in case of backports to kernels before v5.12 that don't have > >> 59450bbc12be ("mm, slab, slub: stop taking cpu hotplug lock"), > >> static_branch_enable_cpuslocked() should be used. > >> > > > > Since this affects 5.9+, is the plan to propose backports to stable with > > static_branch_enable_cpuslocked() once this is merged? (I notice the > > absence of the stable tag here, which I believe is intended.) > > I was thinking about it, and since the rcutorture user is only in -next (AFAICS) > and btrfs user was unintended, it didn't seem to meet stable criteria to me. But > I won't mind if it's backported. I had better ask... Should rcutorture be doing something different? Thanx, Paul > >> [1] https://lore.kernel.org/linux-btrfs/20210315141824.26099-1-dsterba@suse.com/ > >> > >> Reported-by: Oliver Glitta > >> Fixes: ca0cab65ea2b ("mm, slub: introduce static key for slub_debug()") > >> Signed-off-by: Vlastimil Babka > > > > Acked-by: David Rientjes > > Thanks! > > >> --- > >> mm/slub.c | 9 +++++++++ > >> 1 file changed, 9 insertions(+) > >> > >> diff --git a/mm/slub.c b/mm/slub.c > >> index 350a37f30e60..cd6694ad1a0a 100644 > >> --- a/mm/slub.c > >> +++ b/mm/slub.c > >> @@ -3827,6 +3827,15 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order) > >> > >> static int kmem_cache_open(struct kmem_cache *s, slab_flags_t flags) > >> { > >> +#ifdef CONFIG_SLUB_DEBUG > >> + /* > >> + * If no slub_debug was enabled globally, the static key is not yet > >> + * enabled by setup_slub_debug(). Enable it if the cache is being > >> + * created with any of the debugging flags passed explicitly. > >> + */ > >> + if (flags & SLAB_DEBUG_FLAGS) > >> + static_branch_enable(&slub_debug_enabled); > >> +#endif > >> s->flags = kmem_cache_flags(s->size, flags, s->name); > >> #ifdef CONFIG_SLAB_FREELIST_HARDENED > >> s->random = get_random_long(); > > >