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Subject: Re: [PATCH v4 23/23] mm/gup: remove support for gup(FOLL_LONGTERM)
To:     Ira Weiny <ira.weiny@intel.com>
CC:     Andrew Morton <akpm@linux-foundation.org>,
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References: <20191113042710.3997854-1-jhubbard@nvidia.com>
 <20191113042710.3997854-24-jhubbard@nvidia.com>
 <20191113190935.GD12947@iweiny-DESK2.sc.intel.com>
From:   John Hubbard <jhubbard@nvidia.com>
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Date:   Wed, 13 Nov 2019 15:27:00 -0800
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On 11/13/19 11:09 AM, Ira Weiny wrote:
...
>> diff --git a/mm/gup.c b/mm/gup.c
>> index 82e7e4ce5027..90f5f95ee7ac 100644
>> --- a/mm/gup.c
>> +++ b/mm/gup.c
>> @@ -1756,11 +1756,11 @@ long get_user_pages(unsigned long start, unsigned long nr_pages,
>>   		struct vm_area_struct **vmas)
>>   {
>>   	/*
>> -	 * FOLL_PIN must only be set internally by the pin_user_page*() and
>> -	 * pin_longterm_*() APIs, never directly by the caller, so enforce that
>> -	 * with an assertion:
>> +	 * FOLL_PIN and FOLL_LONGTERM must only be set internally by the
>> +	 * pin_user_page*() and pin_longterm_*() APIs, never directly by the
>> +	 * caller, so enforce that with an assertion:
>>   	 */
>> -	if (WARN_ON_ONCE(gup_flags & FOLL_PIN))
>> +	if (WARN_ON_ONCE(gup_flags & (FOLL_PIN | FOLL_LONGTERM)))
> 
> Don't we want to block FOLL_LONGTERM in get_user_pages_fast() as well after all
> this?
> 

Yes. But with the latest idea to restore FOLL_LONGTERM to its original glory,
that won't be an issue in the next version. heh.


thanks,
-- 
John Hubbard
NVIDIA