lkml.org 
[lkml]   [2021]   [Sep]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [git pull] iov_iter fixes
From
Date
On 9/9/21 3:19 PM, Jens Axboe wrote:
>> That "req->result" is once again the *original* length, and the above
>> code once again mis-handles the case of "oh, the iov got truncated
>> because of some IO limit".
>>
>> So I've pulled this, but I think it is
>>
>> (a) ugly nasty
>>
>> (b) incomplete and misses a case
>>
>> and needs more thought. At the VERY least it needs that
>> iov_iter_reexpand() in io_resubmit_prep() too, I think.
>>
>> I'd like the comments expanded too. In particular that
>>
>> /* some cases will consume bytes even on error returns */
>
> That comment is from me, and it goes back a few years. IIRC, it was the
> iomap or xfs code that I hit this with, but honestly I don't remember
> all the details at this point. I can try and play with it and see if it
> still reproduces.

OK, one that I immediately found is just doing O_DIRECT to a block
device or file on XFS. As pages are mapped and added, the iov_iter is
advanced. If we then go and submit and get -EAGAIN, for example, then we
return with what we mapped already consumed.

--
Jens Axboe

\
 
 \ /
  Last update: 2021-09-09 23:40    [W:0.124 / U:0.036 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site