Re: [PATCH 02/19] mm/gup: factor out duplicate code from four routines

John Hubbard
2019-10-31T18:43:46Z

On 10/31/19 11:35 AM, Ira Weiny wrote:
> On Wed, Oct 30, 2019 at 03:49:13PM -0700, John Hubbard wrote:
...
>> +
>> +static void __remove_refs_from_head(struct page *page, int refs)
>> +{
>> + /* Do a get_page() first, in case refs == page->_refcount */
>> + get_page(page);
>> + page_ref_sub(page, refs);
>> + put_page(page);
>> +}
>
> I wonder if this is better implemented as "put_compound_head()"? To match the
> try_get_compound_head() call below?

Hi Ira,

Good idea, I'll rename it to that.

>
>> +
>> +static int __huge_pt_done(struct page *head, int nr_recorded_pages, int *nr)
>> +{
>> + *nr += nr_recorded_pages;
>> + SetPageReferenced(head);
>> + return 1;
>
> When will this return anything but 1?
>

Never, but it saves a line at all four call sites, by having it return like that.

I could see how maybe people would prefer to just have it be a void function,
and return 1 directly at the call sites. Since this was a lower line count I
thought maybe it would be slightly better, but it's hard to say really.

thanks,

John Hubbard
NVIDIA