Re: [PATCH v5 2/2] io_uring: avoid unnecessary io_wq_work copy for fast poll feature

[Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>]

hi Jens, Pavel,

Will you have a look at this V5 version? Or we hold on this patchset, and
do the refactoring work related io_wq_work firstly.

Regards,
Xiaoguang Wang


> Basically IORING_OP_POLL_ADD command and async armed poll handlers
> for regular commands don't touch io_wq_work, so only REQ_F_WORK_INITIALIZED
> is set, can we do io_wq_work copy and restore.
> 
> Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
> ---
> V3:
>    drop the REQ_F_WORK_NEED_RESTORE flag introduced in V2 patch, just
>    use REQ_F_WORK_INITIALIZED to control whether to do io_wq_work copy
>    and restore.
> ---
>   fs/io_uring.c | 13 +++++++++----
>   1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 8e022d0f0c86..b761ef7366f9 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -4527,7 +4527,8 @@ static void io_async_task_func(struct callback_head *cb)
>   	spin_unlock_irq(&ctx->completion_lock);
>   
>   	/* restore ->work in case we need to retry again */
> -	memcpy(&req->work, &apoll->work, sizeof(req->work));
> +	if (req->flags & REQ_F_WORK_INITIALIZED)
> +		memcpy(&req->work, &apoll->work, sizeof(req->work));
>   	kfree(apoll);
>   
>   	if (!canceled) {
> @@ -4624,7 +4625,8 @@ static bool io_arm_poll_handler(struct io_kiocb *req)
>   		return false;
>   
>   	req->flags |= REQ_F_POLLED;
> -	memcpy(&apoll->work, &req->work, sizeof(req->work));
> +	if (req->flags & REQ_F_WORK_INITIALIZED)
> +		memcpy(&apoll->work, &req->work, sizeof(req->work));
>   	had_io = req->io != NULL;
>   
>   	get_task_struct(current);
> @@ -4649,7 +4651,8 @@ static bool io_arm_poll_handler(struct io_kiocb *req)
>   		if (!had_io)
>   			io_poll_remove_double(req);
>   		spin_unlock_irq(&ctx->completion_lock);
> -		memcpy(&req->work, &apoll->work, sizeof(req->work));
> +		if (req->flags & REQ_F_WORK_INITIALIZED)
> +			memcpy(&req->work, &apoll->work, sizeof(req->work));
>   		kfree(apoll);
>   		return false;
>   	}
> @@ -4694,7 +4697,9 @@ static bool io_poll_remove_one(struct io_kiocb *req)
>   			 * io_req_work_drop_env below when dropping the
>   			 * final reference.
>   			 */
> -			memcpy(&req->work, &apoll->work, sizeof(req->work));
> +			if (req->flags & REQ_F_WORK_INITIALIZED)
> +				memcpy(&req->work, &apoll->work,
> +				       sizeof(req->work));
>   			kfree(apoll);
>   		}
>   	}
>