Re: [PATCH 5/6] NFS: direct-io: convert to FOLL_PIN pages

[John Hubbard]

On 8/27/22 15:48, Al Viro wrote:
> On Sat, Aug 27, 2022 at 01:36:06AM -0700, John Hubbard wrote:
>> Convert the NFS Direct IO layer to use pin_user_pages_fast() and
>> unpin_user_page(), instead of get_user_pages_fast() and put_page().
> 
> Again, this stuff can be hit with ITER_BVEC iterators
> 
>> -		result = iov_iter_get_pages_alloc2(iter, &pagevec,
>> +		result = dio_w_iov_iter_pin_pages_alloc(iter, &pagevec,
>>  						  rsize, &pgbase);
> 
> and this will break on those.

If anyone has an example handy, of a user space program that leads
to this situation (O_DIRECT with ITER_BVEC), it would really help
me reach enlightenment a lot quicker in this area. :)

thanks,

-- 
John Hubbard
NVIDIA