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Subject: Re: [PATCH] mm/slub: make add_full() condition more explicit
To:     Andrew Morton <akpm@linux-foundation.org>
CC:     Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        "David Rientjes" <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>, <liu.xiang6@zte.com.cn>,
        "open list:SLAB ALLOCATOR" <linux-mm@kvack.org>,
        open list <linux-kernel@vger.kernel.org>,
        <hewenliang4@huawei.com>, <hushiyuan@huawei.com>
References: <20200811020240.1231-1-wuyun.wu@huawei.com>
 <20200819123713.38a2509a2b7651f14db33e61@linux-foundation.org>
From:   Abel Wu <wuyun.wu@huawei.com>
Message-ID: <85259217-3805-92d8-3be1-8279d8a6a85b@huawei.com>
Date:   Thu, 20 Aug 2020 09:56:23 +0800
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On 2020/8/20 3:37, Andrew Morton wrote:
> On Tue, 11 Aug 2020 10:02:36 +0800 <wuyun.wu@huawei.com> wrote:
> 
>> From: Abel Wu <wuyun.wu@huawei.com>
>>
>> The commit below is incomplete, as it didn't handle the add_full() part.
>> commit a4d3f8916c65 ("slub: remove useless kmem_cache_debug() before remove_full()")
>>
>> This patch checks for SLAB_STORE_USER instead of kmem_cache_debug(),
>> since that should be the only context in which we need the list_lock for
>> add_full().
>>
> 
> Does this contradict what the comment tells us?
> 
> * This also ensures that the scanning of full
> * slabs from diagnostic functions will not see
> * any frozen slabs.
> 
I don't think so. If the flag SLAB_STORE_USER is not set, the slab won't
be added to the full list no matter this patch is applied or not, since
the check inside add_full() will guard for that. Am I missing something
here?
Regards,
	Abel