linux-kernel - Re: [PATCH 04/10] drm/i915: Fix MAX_ORDER usage in i915_gem_object_get_pages

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Message-ID: <f2f35037-d662-19c4-722a-02ec10f86f85@linux.intel.com>
Date:   Wed, 15 Mar 2023 15:35:23 +0000
From:   Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>
Subject: Re: [PATCH 04/10] drm/i915: Fix MAX_ORDER usage in
 i915_gem_object_get_pages_internal()


On 15/03/2023 15:28, Kirill A. Shutemov wrote:
> On Wed, Mar 15, 2023 at 02:18:52PM +0000, Tvrtko Ursulin wrote:
>>
>> On 15/03/2023 11:31, Kirill A. Shutemov wrote:
>>> MAX_ORDER is not inclusive: the maximum allocation order buddy allocator
>>> can deliver is MAX_ORDER-1.
>>
>> This looks to be true on inspection:
>>
>> __alloc_pages():
>> ..
>> 	if (WARN_ON_ONCE_GFP(order >= MAX_ORDER, gfp))
>>
>> So a bit of a misleading name "max".. For the i915 patch:
>>
>> Acked-by: Tvrtko Ursulin <tvrtko.ursulin@...el.com>
>>
>> I don't however see the whole series to understand the context, or how you
>> want to handle the individual patches. Is it a tree wide cleanup of the same
>> mistake?
> 
> The whole patchset can be seen here:
> 
> https://lore.kernel.org/all/20230315113133.11326-1-kirill.shutemov@linux.intel.com/
> 
> The idea is to fix all MAX_ORDER bugs first and then re-define MAX_ORDER
> more sensibly.

Sounds good.

Would you like i915 to take this patch or you will be bringing the whole 
lot via some other route? Former is okay and latter should also be fine 
for i915 since I don't envisage any conflicts here.

Regards,

Tvrtko