linux-kernel - Re: [PATCH v3] mm/gup: stop leaking pinned pages in low memory conditions

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Message-ID: <142152a5-d265-4aa5-b103-dede882f9715@nvidia.com>
Date: Sun, 20 Oct 2024 20:26:50 -0700
From: John Hubbard <jhubbard@...dia.com>
To: Alistair Popple <apopple@...dia.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
 David Hildenbrand <david@...hat.com>, Shigeru Yoshida <syoshida@...hat.com>,
 Jason Gunthorpe <jgg@...dia.com>, Minchan Kim <minchan@...nel.org>,
 Pasha Tatashin <pasha.tatashin@...een.com>
Subject: Re: [PATCH v3] mm/gup: stop leaking pinned pages in low memory
 conditions

On 10/20/24 4:26 PM, Alistair Popple wrote:
> John Hubbard <jhubbard@...dia.com> writes:
> [...]
>> @@ -2437,8 +2440,10 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages,
>>   	long i, ret;
>>   
>>   	folios = kmalloc_array(nr_pages, sizeof(*folios), GFP_KERNEL);
>> -	if (!folios)
>> +	if (!folios) {
>> +		unpin_user_pages(pages, nr_pages);
> 
> ie. Doesn't this unpinning need to happen in
> check_and_migrate_movable_folios()?

It already does.

check_and_migrate_movable_folios() calls
migrate_longterm_unpinnable_folios(), which unpins if errors occur.


thanks,
-- 
John Hubbard