Re: [PATCH for-5.10] io_uring: remove req cancel in ->flush()

[Pavel Begunkov <asml.silence@gmail.com>]

On 20/10/2020 15:09, Jens Axboe wrote:
> On 10/19/20 5:40 PM, Pavel Begunkov wrote:
>> On 19/10/2020 21:08, Jens Axboe wrote:
>>> On 10/19/20 9:45 AM, Pavel Begunkov wrote:
>>>> Every close(io_uring) causes cancellation of all inflight requests
>>>> carrying ->files. That's not nice but was neccessary up until recently.
>>>> Now task->files removal is handled in the core code, so that part of
>>>> flush can be removed.
>>>
>>> Why not just keep the !data for task_drop? Would make the diff take
>>> away just the hunk we're interested in. Even adding a comment would be
>>> better, imho.
>>
>> That would look cleaner, but I just left what already was there. TBH,
>> I don't even entirely understand why exiting=!data. Looking up how
>> exit_files() works, it passes down non-NULL files to
>> put_files_struct() -> ... filp_close() -> f_op->flush().
>>
>> I'm curious how does this filp_close(file, files=NULL) happens?
> 
> It doesn't, we just clear it internall to match all requests, not just
> files backed ones.

Then my "bool exiting = !data;" at the start doesn't make sense since
passed in @data is always non-NULL.

> 
>> Moreover, if that's exit_files() which is interesting, then first
>> it calls io_uring_cancel_task_requests(), which should remove all
>> struct file from tctx->xa. I haven't tested it though.
> 
> Yep, further cleanups are certainly possible there.
> 
> I've queued this up, thanks.
> 

-- 
Pavel Begunkov