lkml.org 
[lkml]   [2022]   [Aug]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH 5/6] NFS: direct-io: convert to FOLL_PIN pages
From
On 8/27/22 17:39, Al Viro wrote:
> On Sun, Aug 28, 2022 at 01:38:57AM +0100, Al Viro wrote:
>> On Sat, Aug 27, 2022 at 04:55:18PM -0700, John Hubbard wrote:
>>> 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. :)
>>
>> Er... splice(2) to O_DIRECT-opened file on e.g. ext4? Or
>> sendfile(2) to the same, for that matter...
>
> s/ext4/nfs/ to hit this particular codepath, obviously.

aha, thanks. I do remember that you alerted me earlier to splice(2)
problems, and I thought I'd neatly sidestepped those this time, by
staying with user_backed_iter(i) cases.

But I see that it's going to take something more, after all.



thanks,

--
John Hubbard
NVIDIA

\
 
 \ /
  Last update: 2022-08-28 02:47    [W:0.073 / U:0.044 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site