linux-kernel - Re: [PATCH v4 4/4] mm/page_isolation: remove migratetype parameter from more functions.

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Message-ID: <BB5A1C92-743E-4114-BA09-CB8C488325FA@nvidia.com>
Date: Sat, 17 May 2025 20:07:28 -0400
From: Zi Yan <ziy@...dia.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: David Hildenbrand <david@...hat.com>, Oscar Salvador <osalvador@...e.de>,
 Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
 Andrew Morton <akpm@...ux-foundation.org>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
 Mel Gorman <mgorman@...hsingularity.net>,
 Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
 Brendan Jackman <jackmanb@...gle.com>, Richard Chang <richardycc@...gle.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 4/4] mm/page_isolation: remove migratetype parameter
 from more functions.

On 17 May 2025, at 16:21, Vlastimil Babka wrote:

> On 5/9/25 22:01, Zi Yan wrote:
>> migratetype is no longer overwritten during pageblock isolation,
>> start_isolate_page_range(), has_unmovable_pages(), and
>> set_migratetype_isolate() no longer need which migratetype to restore
>> during isolation failure.
>>
>> For has_unmoable_pages(), it needs to know if the isolation is for CMA
>> allocation, so adding CMA_ALLOCATION to isolation flags to provide the
>> information.
>>
>> alloc_contig_range() no longer needs migratetype. Replace it with
>> a newly defined acr_flags_t to tell if an allocation is for CMA. So does
>> __alloc_contig_migrate_range().
>>
>> Signed-off-by: Zi Yan <ziy@...dia.com>
>
> AFAICS has_unmovable_pages() adds the flags parameter but doesn't use it.

Yes, will remove it.

>
> But also, I think having both mode and flags is just unnecessary complexity
> in this case? CMA_ALLOCATION could be just a new flag? Even if some flag
> combinations wouldn't logicaly make sense, this has only so few users so we
> don't have to care to make them exclusive with the mode thing.

I was doing that until v3.

> Also I think REPORT_FAILURE is only used with MEMORY_OFFLINE so it could be
> squashed?

Yes, let me do that. Johannes also pointed this out but I missed it.

In the next version, I will remove REPORT_FAILURE as it is implied by
MEMORY_OFFLINE, including isolate_flags_t, and keep the existing enum
with MEMORY_OFFLINE and CMA_ALLOCATION.

Thanks for the review.

--
Best Regards,
Yan, Zi