Re: [PATCH 1/5] io_uring: grab any needed state during defer prep

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

On 19/09/2020 19:56, Pavel Begunkov wrote:
> On 19/09/2020 18:27, Pavel Begunkov wrote:
>> On 14/09/2020 19:25, Jens Axboe wrote:
>>> Always grab work environment for deferred links. The assumption that we
>>> will be running it always from the task in question is false, as exiting
>>> tasks may mean that we're deferring this one to a thread helper. And at
>>> that point it's too late to grab the work environment.
> Forgot that they will be cancelled there. So, how it could happen?
> Is that the initial thread will run task_work but loosing
> some resources like mm prior to that? e.g. in do_exit()

Jens, please let me know when you get time for that. I was thinking that
you were meaning do_exit(), which does task_work_run() after killing mm,
etc., but you mentioned a thread helper in the description... Which one
do you mean?

>
>>
>>>
>>> Fixes: debb85f496c9 ("io_uring: factor out grab_env() from defer_prep()")
>>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>>> ---
>>>  fs/io_uring.c | 2 ++
>>>  1 file changed, 2 insertions(+)
>>>
>>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>>> index 175fb647d099..be9d628e7854 100644
>>> --- a/fs/io_uring.c
>>> +++ b/fs/io_uring.c
>>> @@ -5449,6 +5449,8 @@ static int io_req_defer_prep(struct io_kiocb *req,
>>>  	if (unlikely(ret))
>>>  		return ret;
>>>  
>>> +	io_prep_async_work(req);
>>> +
>>>  	switch (req->opcode) {
>>>  	case IORING_OP_NOP:
>>>  		break;
>>>
>>
> 

-- 
Pavel Begunkov