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Subject: Re: [PATCH v5 10/12] mm/gup: /proc/vmstat: pin_user_pages (FOLL_PIN)
 reporting
To:     Jan Kara <jack@suse.cz>
CC:     Andrew Morton <akpm@linux-foundation.org>,
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References: <20200207033735.308000-1-jhubbard@nvidia.com>
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From:   John Hubbard <jhubbard@nvidia.com>
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On 2/10/20 2:16 AM, Jan Kara wrote:
> On Thu 06-02-20 19:37:33, John Hubbard wrote:
>> @@ -2258,6 +2268,8 @@ static int record_subpages(struct page *page, unsigned long addr,
>>   
>>   static void put_compound_head(struct page *page, int refs, unsigned int flags)
>>   {
>> +	int orig_refs = refs;
>> +
>>   	if (flags & FOLL_PIN) {
>>   		if (hpage_pincount_available(page))
>>   			hpage_pincount_sub(page, refs);
>> @@ -2273,6 +2285,8 @@ static void put_compound_head(struct page *page, int refs, unsigned int flags)
>>   	if (refs > 1)
>>   		page_ref_sub(page, refs - 1);
>>   	put_page(page);
>> +
>> +	mod_node_page_state(page_pgdat(page), NR_FOLL_PIN_RELEASED, orig_refs);
>>   }
> 
> Still not quite happy about this :) Now you update NR_FOLL_PIN_RELEASED
> even if 'flags' don't have FOLL_PIN set. You need to have the
> mod_node_page_state() inside the "if (flags & FOLL_PIN)" branch above...
> 
> 									Honza

Arggh, yes that's true. Thanks for catching that, will fix in v6.


thanks,
-- 
John Hubbard
NVIDIA