linux-kernel - Re: [PATCH v2 1/3] mm: memory-failure: update ttu flag inside unmap_poisoned

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Message-ID: <34ccd133-7623-4cd8-aad7-08526a97c472@redhat.com>
Date: Mon, 20 Jan 2025 08:49:59 +0100
From: David Hildenbrand <david@...hat.com>
To: Miaohe Lin <linmiaohe@...wei.com>, Wupeng Ma <mawupeng1@...wei.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 akpm@...ux-foundation.org, osalvador@...e.de, nao.horiguchi@...il.com,
 mhocko@...e.com
Subject: Re: [PATCH v2 1/3] mm: memory-failure: update ttu flag inside
 unmap_poisoned_folio


>>   	if (folio_test_hugetlb(folio) && !folio_test_anon(folio)) {
>>   		struct address_space *mapping;
>>   
>> @@ -1572,7 +1598,7 @@ void unmap_poisoned_folio(struct folio *folio, enum ttu_flags ttu)
>>   		if (!mapping) {
>>   			pr_info("%#lx: could not lock mapping for mapped hugetlb folio\n",
>>   				folio_pfn(folio));
>> -			return;
>> +			return -EBUSY;
>>   		}
>>   
>>   		try_to_unmap(folio, ttu|TTU_RMAP_LOCKED);
>> @@ -1580,6 +1606,8 @@ void unmap_poisoned_folio(struct folio *folio, enum ttu_flags ttu)
>>   	} else {
>>   		try_to_unmap(folio, ttu);
>>   	}
>> +
>> +	return folio_mapped(folio) ? -EBUSY : 0;
> 
> Do we really need this return value? It's unused in do_migrate_range().

I suggested it, because the folio_mapped() is nowadays extremely cheap. 
It cleans up hwpoison_user_mappings() quite nicely.

Any particular reason we shouldn't be doing that?

-- 
Cheers,

David / dhildenb