linux-kernel - Re: [PATCH v2] mm/memory-failure: Support disabling soft offline for HugeTLB pages

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Message-ID: <8c3188da-7078-4099-973a-1d0d74db2720@redhat.com>
Date: Wed, 17 Sep 2025 09:02:55 +0200
From: David Hildenbrand <david@...hat.com>
To: Anshuman Khandual <anshuman.khandual@....com>,
 Kyle Meyer <kyle.meyer@....com>, akpm@...ux-foundation.org, corbet@....net,
 linmiaohe@...wei.com, shuah@...nel.org, tony.luck@...el.com,
 jane.chu@...cle.com, jiaqiyan@...gle.com
Cc: Liam.Howlett@...cle.com, bp@...en8.de, hannes@...xchg.org, jack@...e.cz,
 joel.granados@...nel.org, laoar.shao@...il.com, lorenzo.stoakes@...cle.com,
 mclapinski@...gle.com, mhocko@...e.com, nao.horiguchi@...il.com,
 osalvador@...e.de, rafael.j.wysocki@...el.com, rppt@...nel.org,
 russ.anderson@....com, shawn.fan@...el.com, surenb@...gle.com,
 vbabka@...e.cz, linux-acpi@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
 linux-mm@...ck.org
Subject: Re: [PATCH v2] mm/memory-failure: Support disabling soft offline for
 HugeTLB pages


>> +
>> +	0 - Enable soft offline
>> +	1 - Disable soft offline for HugeTLB pages
>> +
>> +Supported values::
>> +
>> +	0 - Soft offline is disabled
>> +	1 - Soft offline is enabled
>> +	3 - Soft offline is enabled (disabled for HugeTLB pages)
> 
> This looks very adhoc even though existing behavior is preserved.
> 
> - Are HugeTLB pages the only page types to be considered ?
> - How the remaining bits here are going to be used later ?
> 

What I proposed (that could be better documented here) is that all other 
bits except the first one will be a disable mask when bit 0 is set.

2 - ... but yet disabled for hugetlb
4 - ... but yet disabled for $WHATEVER
8 - ... but yet disabled for $WHATEVERELSE

> Also without a bit-wise usage roadmap, is not changing a procfs
> interface (ABI) bit problematic ?

For now we failed setting it to values that are neither 0 or 1, IIUC 
set_enable_soft_offline() correctly?

So there should not be any problem, or which scenario do you have in mind?


-- 
Cheers

David / dhildenb