Re: [PATCH v3] mm, slub: change run-time assertion in kmalloc_index() to compile-time

Nathan Chancellor
2021-05-18T00:43:29Z

On 5/17/2021 5:38 PM, Hyeonggon Yoo wrote:
> On Sat, May 15, 2021 at 11:34:49PM -0700, Nathan Chancellor wrote:
>> This should work I think:
>
> compiled well with clang-10.0.1, clang-11.0.0,
> and gcc-10.2.0 with x86_64 default config.
>
> is the condition CONFIG_CLANG_VERSION > 110000,
> not including 110000 it self?

Ah sorry, that should definitely be >= :(

That is what I get for writing an email that late... in reality, it
probably won't matter due to the availability of 11.0.1 and 11.1.0 but
it should absolutely be changed.

I have not given Nick's patch a go yet but would something like this be
acceptable? If so, did you want me to send a formal fixup patch or did
you want to send a v4? I have no personal preference.

>> diff --git a/include/linux/slab.h b/include/linux/slab.h
>> index 9d316aac0aba..1b653266f2aa 100644
>> --- a/include/linux/slab.h
>> +++ b/include/linux/slab.h
>> @@ -413,7 +413,7 @@ static __always_inline unsigned int __kmalloc_index(size_t size,
>> if (size <= 16 * 1024 * 1024) return 24;
>> if (size <= 32 * 1024 * 1024) return 25;
>>
>> - if (size_is_constant)
>> + if ((IS_ENABLED(CONFIG_CC_IS_GCC) || CONFIG_CLANG_VERSION > 110000) && size_is_constant)
>> BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()");
>> else
>> BUG();