Re: block: DMA alignment of IO buffer allocated from slab

[Jens Axboe]

On 9/21/18 7:05 AM, Christoph Hellwig wrote:
> On Fri, Sep 21, 2018 at 03:04:18PM +0200, Vitaly Kuznetsov wrote:
>> Christoph Hellwig <hch@xxxxxx> writes:
>>
>>> On Wed, Sep 19, 2018 at 05:15:43PM +0800, Ming Lei wrote:
>>>> 1) does kmalloc-N slab guarantee to return N-byte aligned buffer?  If
>>>> yes, is it a stable rule?
>>>
>>> This is the assumption in a lot of the kernel, so I think if somethings
>>> breaks this we are in a lot of pain.
>>
>> It seems that SLUB debug breaks this assumption. Kernel built with
>>
>> CONFIG_SLUB_DEBUG=y
>> CONFIG_SLUB=y
>> CONFIG_SLUB_DEBUG_ON=y
> 
> Looks like we should fix SLUB debug then..

Fully agree, it's such a fundamental property.

-- 
Jens Axboe