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

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Message-ID: <80984553-a2b9-46b4-acdc-f7abba3c755f@redhat.com>
Date: Mon, 20 Jan 2025 09:46:20 +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

On 20.01.25 08:49, David Hildenbrand wrote:
> 
>>>    	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.

I'm also wondering, if in do_migrate_range(), we want to 
pr_warn_ratelimit() in case still mapped after the call. IIUC, we don't 
really expect this to happen with SYNC set.

-- 
Cheers,

David / dhildenb