Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <e6b415c8-4905-8bbd-fe72-d3d95d77c890@suse.cz>
Date:   Mon, 24 Oct 2022 13:10:57 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.3.3
Subject: Re: [PATCH] mm/slub: remove dead code for debug caches on
 deactivate_slab()
Content-Language: en-US
To:     Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc:     Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Roman Gushchin <roman.gushchin@linux.dev>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <20221014114322.97512-1-42.hyeyoo@gmail.com>
 <82e8147e-f031-6bc2-9395-56d2052e62cb@suse.cz> <Y1NuEhXgxmr2OHeH@hyeyoo>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <Y1NuEhXgxmr2OHeH@hyeyoo>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 10/22/22 06:14, Hyeonggon Yoo wrote:
> On Fri, Oct 21, 2022 at 12:43:42PM +0200, Vlastimil Babka wrote:
>> On 10/14/22 13:43, Hyeonggon Yoo wrote:
>> > After commit c7323a5ad0786 ("mm/slub: restrict sysfs validation to debug
>> > caches and make it safe"), SLUB does not take a slab from partial list for
>> 
>> I'm confused by "SLUB does not take a slab from partial list" here. Did you
>> mean something like "SLUB never installs (even temporarily) a percpu slab
>> for debug caches"?
> 
> Yes.
> 
>> So that means we never deactivate percpu slabs for debug
>> caches.
> 
> Yes.
> 
>> And since debug caches are also the only ones that use the full
>> list, we no longer need to care about the full list in deactivate_slab(), right?
> 
> Yes, You got it right, exactly!
> 
> Let me rephrase:
> 
> "After commit c7323a5ad0786 ("mm/slub: restrict sysfs validation to debug
> caches and make it safe"), SLUB never installs percpu slab for debug caches
> and thus never deactivates percpu slab for them.
> 
> Since only some of debug caches care about the full list, SLUB no longer
> deactivates to full list. Remove dead code in deactivate_slab()."
> 
> 
> Feel free to change this ;-)

Great, thanks!

Pushed to slab/for-6.2/cleanups