linux-kernel - Re: [PATCH 04/16] mm/slab: activate debug_pagealloc in SLAB when it is actually enabled

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Date:	Fri, 15 Jan 2016 01:16:55 +0900
From:	Joonsoo Kim <js1304@...il.com>
To:	Jesper Dangaard Brouer <brouer@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Linux Memory Management List <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 04/16] mm/slab: activate debug_pagealloc in SLAB when it
 is actually enabled

2016-01-14 21:09 GMT+09:00 Jesper Dangaard Brouer <brouer@...hat.com>:
> On Thu, 14 Jan 2016 14:24:17 +0900
> Joonsoo Kim <js1304@...il.com> wrote:
>
>> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
>> ---
>>  mm/slab.c | 15 ++++++++++-----
>>  1 file changed, 10 insertions(+), 5 deletions(-)
>>
>> diff --git a/mm/slab.c b/mm/slab.c
>> index bbe4df2..4b55516 100644
>> --- a/mm/slab.c
>> +++ b/mm/slab.c
>> @@ -1838,7 +1838,8 @@ static void slab_destroy_debugcheck(struct kmem_cache *cachep,
>>
>>               if (cachep->flags & SLAB_POISON) {
>>  #ifdef CONFIG_DEBUG_PAGEALLOC
>> -                     if (cachep->size % PAGE_SIZE == 0 &&
>> +                     if (debug_pagealloc_enabled() &&
>> +                             cachep->size % PAGE_SIZE == 0 &&
>>                                       OFF_SLAB(cachep))
>>                               kernel_map_pages(virt_to_page(objp),
>>                                       cachep->size / PAGE_SIZE, 1);
>> @@ -2176,7 +2177,8 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
>>        * to check size >= 256. It guarantees that all necessary small
>>        * sized slab is initialized in current slab initialization sequence.
>>        */
>> -     if (!slab_early_init && size >= kmalloc_size(INDEX_NODE) &&
>> +     if (debug_pagealloc_enabled() &&
>> +             !slab_early_init && size >= kmalloc_size(INDEX_NODE) &&
>>               size >= 256 && cachep->object_size > cache_line_size() &&
>>               ALIGN(size, cachep->align) < PAGE_SIZE) {
>>               cachep->obj_offset += PAGE_SIZE - ALIGN(size, cachep->align);
>> @@ -2232,7 +2234,8 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
>>                * poisoning, then it's going to smash the contents of
>>                * the redzone and userword anyhow, so switch them off.
>>                */
>> -             if (size % PAGE_SIZE == 0 && flags & SLAB_POISON)
>> +             if (debug_pagealloc_enabled() &&
>> +                     size % PAGE_SIZE == 0 && flags & SLAB_POISON)
>>                       flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER);
>
> Sorry, but I dislike the indention style here (when the if covers
> several lines). Same goes for other changes in this patch.  Looking,
> there are several example of this indention style in the existing
> mm/slab.c. Thus, I don't know if this is accepted in the MM area (it is
> definitely not accepted in the NET-area).

I guess it is acceptable in the MM. :)
Moreover, it is cleaned-up in the following patch.
But, I hope to know how it is handled in the NET-area.

Thanks.