Feedback-ID: ie3994620:Fastmail
Date:   Wed, 15 Mar 2023 18:28:02 +0300
From:   "Kirill A. Shutemov" <kirill@shutemov.name>
To:     Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mgorman@suse.de>, Vlastimil Babka <vbabka@suse.cz>,
        David Hildenbrand <david@redhat.com>, linux-mm@kvack.org,
        linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>
Subject: Re: [PATCH 04/10] drm/i915: Fix MAX_ORDER usage in
 i915_gem_object_get_pages_internal()
Message-ID: <20230315152802.gr2olzji5zhu6vdo@box>
References: <20230315113133.11326-1-kirill.shutemov@linux.intel.com>
 <20230315113133.11326-5-kirill.shutemov@linux.intel.com>
 <7fe9a4a0-9b30-38db-e739-1dc1f7a8f74e@linux.intel.com>
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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@intel.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.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov