Re: RFA (Request for Advice): block/bio: get_user_pages() --> pin_user_pages()

[John Hubbard <jhubbard@nvidia.com>]

On 1/24/22 02:05, Jan Kara wrote:
...
>> do_direct_IO()
>>      dio_zero_block()
>>          page = ZERO_PAGE(0); <-- This is a problem
>>
>> I'm not sure what to use, instead of that zero page! The zero page
>> doesn't need to be allocated nor tracked, and so any replacement
>> approaches would need either other storage, or some horrid scheme that I
>> won't go so far as to write on the screen. :)
> 
> Well, I'm not sure if you consider this ugly but currently we use
> get_page() in that path exactly so that bio_release_pages() does not have
> to care about zero page. So now we could grab pin on the zero page instead
> through try_grab_page() or something like that...
> 
> 								Honza

So it sounds like you prefer this over checking for the zero page in
bio_release_pages(). I'll take a look at both ideas, then, and see what
it looks like.


thanks,
-- 
John Hubbard
NVIDIA