linux-kernel - Re: [PATCH 1/5] mm, slab: Make kmalloc

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Date:   Mon, 9 Sep 2019 21:48:59 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Pengfei Li <lpf.vector@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Christopher Lameter <cl@...ux.com>, penberg@...nel.org,
        rientjes@...gle.com, iamjoonsoo.kim@....com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] mm, slab: Make kmalloc_info[] contain all types of
 names

On 9/9/19 8:30 PM, Rasmus Villemoes wrote:
> On 09/09/2019 18.53, Pengfei Li wrote:
>> On Mon, Sep 9, 2019 at 10:59 PM Vlastimil Babka <vbabka@...e.cz> wrote:
> 
>>>>   /*
>>>>    * kmalloc_info[] is to make slub_debug=,kmalloc-xx option work at boot time.
>>>>    * kmalloc_index() supports up to 2^26=64MB, so the final entry of the table is
>>>>    * kmalloc-67108864.
>>>>    */
>>>>   const struct kmalloc_info_struct kmalloc_info[] __initconst = {
>>>
>>> BTW should it really be an __initconst, when references to the names
>>> keep on living in kmem_cache structs? Isn't this for data that's
>>> discarded after init?
>>
>> You are right, I will remove __initconst in v2.
> 
> No, __initconst is correct, and should be kept. The string literals
> which the .name pointers point to live in .rodata, and we're copying the
> values of these .name pointers. Nothing refers to something inside
> kmalloc_info[] after init. (It would be a whole different matter if
> struct kmalloc_info_struct consisted of { char name[NN]; unsigned int
> size; }).

*slaps forehead* ah, of course, string literals themselves are not
affected by the __initconst, thanks! Sorry for the wrong suggestion Pengfei.

> Rasmus
>