Re: [PATCH 3/3] io_uring: move struct io_kiocb from task_struct to io_uring_task

[Jens Axboe <axboe@kernel.dk>]

On 11/3/24 3:05 PM, Pavel Begunkov wrote:
> On 11/3/24 21:54, Jens Axboe wrote:
>> On 11/3/24 2:47 PM, Pavel Begunkov wrote:
>>> On 11/3/24 17:49, Jens Axboe wrote:
>>> ...
>>>> diff --git a/include/linux/io_uring/cmd.h b/include/linux/io_uring/cmd.h
>>> ...
>>>>        nd->head = prev_nd->head;
>>>> @@ -115,7 +115,7 @@ struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx)
>>>>        notif->opcode = IORING_OP_NOP;
>>>>        notif->flags = 0;
>>>>        notif->file = NULL;
>>>> -    notif->task = current;
>>>> +    notif->tctx = current->io_uring;
>>>>        io_get_task_refs(1);
>>>>        notif->file_node = NULL;
>>>>        notif->buf_node = NULL;
>>>> diff --git a/io_uring/poll.c b/io_uring/poll.c
>>>> index 7db3010b5733..56332893a4b0 100644
>>>> --- a/io_uring/poll.c
>>>> +++ b/io_uring/poll.c
>>>> @@ -224,8 +224,7 @@ static int io_poll_check_events(struct io_kiocb *req, struct io_tw_state *ts)
>>>>    {
>>>>        int v;
>>>>    -    /* req->task == current here, checking PF_EXITING is safe */
>>>> -    if (unlikely(req->task->flags & PF_EXITING))
>>>> +    if (unlikely(current->flags & PF_EXITING))
>>>>            return -ECANCELED
>>>
>>> Unlike what the comment says, req->task doesn't have to match current,
>>> in which case the new check does nothing and it'll break in many very
>>> interesting ways.
>>
>> In which cases does it not outside of fallback?
> 
> I think it can only be fallback path

I think so too, that's what I was getting at. Hence I think we should just
change these PF_EXITING checks to be PF_KTHREAD instead. If we're invoked
from that kind of context, cancel.

I'll adjust.

-- 
Jens Axboe