linux-kernel - Re: [PATCH 4/5] exit: add internal include file with helpers

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Message-ID: <c36db018-79a5-e071-ef80-00c5fd05d4fb@kernel.dk>
Date:   Fri, 14 Jul 2023 14:21:08 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Christian Brauner <brauner@...nel.org>
Cc:     io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
        arnd@...db.de
Subject: Re: [PATCH 4/5] exit: add internal include file with helpers

On 7/14/23 2:16?PM, Jens Axboe wrote:
> On 7/14/23 9:38?AM, Christian Brauner wrote:
>>> diff --git a/kernel/exit.h b/kernel/exit.h
>>> new file mode 100644
>>> index 000000000000..f10207ba1341
>>> --- /dev/null
>>> +++ b/kernel/exit.h
>>> @@ -0,0 +1,30 @@
>>> +// SPDX-License-Identifier: GPL-2.0-only
>>> +#ifndef LINUX_WAITID_H
>>> +#define LINUX_WAITID_H
>>> +
>>> +struct waitid_info {
>>> +	pid_t pid;
>>> +	uid_t uid;
>>> +	int status;
>>> +	int cause;
>>> +};
>>> +
>>> +struct wait_opts {
>>> +	enum pid_type		wo_type;
>>> +	int			wo_flags;
>>> +	struct pid		*wo_pid;
>>> +
>>> +	struct waitid_info	*wo_info;
>>> +	int			wo_stat;
>>> +	struct rusage		*wo_rusage;
>>> +
>>> +	wait_queue_entry_t		child_wait;
>>> +	int			notask_error;
>>> +};
>>> +
>>> +bool pid_child_should_wake(struct wait_opts *wo, struct task_struct *p);
>>> +long __do_wait(struct wait_opts *wo);
>>> +int kernel_waitid_prepare(struct wait_opts *wo, int which, pid_t upid,
>>> +			  struct waitid_info *infop, int options,
>>> +			  struct rusage *ru, unsigned int *f_flags);
>>
>> I know this isn't your mess obviously but could you try and see whether
>> you can expose a nicer, dedicated struct and helper suited to io_uring's
>> needs instead of exposing the messy kernel/exit.c format?
> 
> From a quick look, I think the wait_opts is pretty much what we need,
> not much to cut from that. For waitid_info, we can make do with just a
> forward declaration, we don't need the whole thing.

I'm wrong obviously, we do need waitid_info as well as that is the
output side... Seems to me that none of them have anything redundant wrt
io_uring. They could be combined into one thing, but is it worth it?

-- 
Jens Axboe