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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 93365C433E0 for ; Mon, 15 Jun 2020 13:08:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 775782076A for ; Mon, 15 Jun 2020 13:08:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730215AbgFONIj (ORCPT ); Mon, 15 Jun 2020 09:08:39 -0400 Received: from mx2.suse.de ([195.135.220.15]:47024 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729875AbgFONIh (ORCPT ); Mon, 15 Jun 2020 09:08:37 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 70E58ACB8; Mon, 15 Jun 2020 13:08:39 +0000 (UTC) Subject: Re: [PATCH] mm/slab: Add a __GFP_ACCOUNT GFP flag check for slab allocation To: Muchun Song , cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Roman Gushchin References: <20200614063858.85118-1-songmuchun@bytedance.com> From: Vlastimil Babka Message-ID: Date: Mon, 15 Jun 2020 15:08:32 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200614063858.85118-1-songmuchun@bytedance.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/14/20 8:38 AM, Muchun Song wrote: > When a kmem_cache is initialized with SLAB_ACCOUNT slab flag, we must > not call kmem_cache_alloc with __GFP_ACCOUNT GFP flag. In this case, > we can be accounted to kmemcg twice. This is not correct. So we add a Are you sure? How does that happen? The only place I see these evaluated is this condition in slab_pre_alloc_hook(): if (memcg_kmem_enabled() && ((flags & __GFP_ACCOUNT) || (s->flags & SLAB_ACCOUNT))) return memcg_kmem_get_cache(s); And it doesn't matter if one or both are set? Am I missing something? > __GFP_ACCOUNT GFP flag check for slab allocation. > > We also introduce a new helper named fixup_gfp_flags to do that check. > We can reuse the fixup_gfp_flags for SLAB/SLUB. > > Signed-off-by: Muchun Song > --- > mm/slab.c | 10 +--------- > mm/slab.h | 21 +++++++++++++++++++++ > mm/slub.c | 10 +--------- > 3 files changed, 23 insertions(+), 18 deletions(-) > > diff --git a/mm/slab.c b/mm/slab.c > index 9350062ffc1a..6e0110bef2d6 100644 > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -126,8 +126,6 @@ > > #include > > -#include "internal.h" > - > #include "slab.h" > > /* > @@ -2579,13 +2577,7 @@ static struct page *cache_grow_begin(struct kmem_cache *cachep, > * Be lazy and only check for valid flags here, keeping it out of the > * critical path in kmem_cache_alloc(). > */ > - if (unlikely(flags & GFP_SLAB_BUG_MASK)) { > - gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK; > - flags &= ~GFP_SLAB_BUG_MASK; > - pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n", > - invalid_mask, &invalid_mask, flags, &flags); > - dump_stack(); > - } > + flags = fixup_gfp_flags(cachep, flags); > WARN_ON_ONCE(cachep->ctor && (flags & __GFP_ZERO)); > local_flags = flags & (GFP_CONSTRAINT_MASK|GFP_RECLAIM_MASK); > > diff --git a/mm/slab.h b/mm/slab.h > index 815e4e9a94cd..0b91f2a7b033 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -109,6 +109,7 @@ struct memcg_cache_params { > #include > #include > #include > +#include "internal.h" > > /* > * State of the slab allocator. > @@ -627,6 +628,26 @@ struct kmem_cache_node { > > }; > > +static inline gfp_t fixup_gfp_flags(struct kmem_cache *s, gfp_t flags) > +{ > + gfp_t invalid_mask = 0; > + > + if (unlikely(flags & GFP_SLAB_BUG_MASK)) > + invalid_mask |= flags & GFP_SLAB_BUG_MASK; > + > + if (unlikely(flags & __GFP_ACCOUNT && s->flags & SLAB_ACCOUNT)) > + invalid_mask |= __GFP_ACCOUNT; > + > + if (unlikely(invalid_mask)) { > + flags &= ~invalid_mask; > + pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n", > + invalid_mask, &invalid_mask, flags, &flags); > + dump_stack(); > + } > + > + return flags; > +} > + > static inline struct kmem_cache_node *get_node(struct kmem_cache *s, int node) > { > return s->node[node]; > diff --git a/mm/slub.c b/mm/slub.c > index b8f798b50d44..49b5cb7da318 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -37,8 +37,6 @@ > > #include > > -#include "internal.h" > - > /* > * Lock order: > * 1. slab_mutex (Global Mutex) > @@ -1745,13 +1743,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) > > static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node) > { > - if (unlikely(flags & GFP_SLAB_BUG_MASK)) { > - gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK; > - flags &= ~GFP_SLAB_BUG_MASK; > - pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n", > - invalid_mask, &invalid_mask, flags, &flags); > - dump_stack(); > - } > + flags = fixup_gfp_flags(s, flags); > > return allocate_slab(s, > flags & (GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK), node); >