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

[Christian Brauner <brauner@kernel.org>]

On Tue, Jul 11, 2023 at 02:43:51PM -0600, Jens Axboe wrote:
> Move struct wait_opts and waitid_info into kernel/exit.h, and include
> function declarations for the recently added helpers. Make them
> non-static as well.
> 
> This is in preparation for adding a waitid operation through io_uring.
> With the abtracted helpers, this is now possible.
> 
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
>  kernel/exit.c | 32 +++++++-------------------------
>  kernel/exit.h | 30 ++++++++++++++++++++++++++++++
>  2 files changed, 37 insertions(+), 25 deletions(-)
>  create mode 100644 kernel/exit.h
> 
> diff --git a/kernel/exit.c b/kernel/exit.c
> index 8934c91a9fe1..1c9d1cbadcd0 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -74,6 +74,8 @@
>  #include <asm/unistd.h>
>  #include <asm/mmu_context.h>
>  
> +#include "exit.h"
> +
>  /*
>   * The default value should be high enough to not crash a system that randomly
>   * crashes its kernel from time to time, but low enough to at least not permit
> @@ -1037,26 +1039,6 @@ SYSCALL_DEFINE1(exit_group, int, error_code)
>  	return 0;
>  }
>  
> -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;
> -};
> -
>  static int eligible_pid(struct wait_opts *wo, struct task_struct *p)
>  {
>  	return	wo->wo_type == PIDTYPE_MAX ||
> @@ -1520,7 +1502,7 @@ static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
>  	return 0;
>  }
>  
> -static bool pid_child_should_wake(struct wait_opts *wo, struct task_struct *p)
> +bool pid_child_should_wake(struct wait_opts *wo, struct task_struct *p)
>  {
>  	if (!eligible_pid(wo, p))
>  		return false;
> @@ -1590,7 +1572,7 @@ static int do_wait_pid(struct wait_opts *wo)
>  	return 0;
>  }
>  
> -static long __do_wait(struct wait_opts *wo)
> +long __do_wait(struct wait_opts *wo)
>  {
>  	long retval;
>  
> @@ -1662,9 +1644,9 @@ static long do_wait(struct wait_opts *wo)
>  	return retval;
>  }
>  
> -static 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)
> +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)
>  {
>  	struct pid *pid = NULL;
>  	enum pid_type type;
> 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?