# Re: \[PATCH v6 4/7\] pid: move pidfd\_get\_pid function to pid.c

- From: Suren Baghdasaryan \<surenb@google.com\>
- Date: 2020-02-28 22:22:55 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2020/02/5879893
- Thread: https://ratatoskr.run/linux-mm/2020/02/5866950/t.md

```text
On Tue, Feb 18, 2020 at 5:44 PM Minchan Kim [ref] wrote:
>
> process_madvise syscall needs pidfd_get_pid function to translate
> pidfd to pid so this patch move the function to kernel/pid.c.
>
> Cc: Christoph Hellwig <hch@infradead.org>
> Cc: Christian Brauner <christian@brauner.io>
> Suggested-by: Alexander Duyck <redacted>
> Reviewed-by: Alexander Duyck <redacted>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
>  include/linux/pid.h |  1 +
>  kernel/exit.c       | 17 -----------------
>  kernel/pid.c        | 17 +++++++++++++++++
>  3 files changed, 18 insertions(+), 17 deletions(-)
>
> diff --git a/include/linux/pid.h b/include/linux/pid.h
> index 998ae7d24450..993f68cb45c2 100644
> --- a/include/linux/pid.h
> +++ b/include/linux/pid.h
> @@ -75,6 +75,7 @@ extern const struct file_operations pidfd_fops;
>  struct file;
>
>  extern struct pid *pidfd_pid(const struct file *file);
> +struct pid *pidfd_get_pid(unsigned int fd);
>
>  static inline struct pid *get_pid(struct pid *pid)
>  {
> diff --git a/kernel/exit.c b/kernel/exit.c
> index 0b81b26a872a..43375f9d8bbc 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -1470,23 +1470,6 @@ static long do_wait(struct wait_opts *wo)
>         return retval;
>  }
>
> -static struct pid *pidfd_get_pid(unsigned int fd)
> -{
> -       struct fd f;
> -       struct pid *pid;
> -
> -       f = fdget(fd);
> -       if (!f.file)
> -               return ERR_PTR(-EBADF);
> -
> -       pid = pidfd_pid(f.file);
> -       if (!IS_ERR(pid))
> -               get_pid(pid);
> -
> -       fdput(f);
> -       return pid;
> -}
> -
>  static long kernel_waitid(int which, pid_t upid, struct waitid_info *infop,
>                           int options, struct rusage *ru)
>  {
> diff --git a/kernel/pid.c b/kernel/pid.c
> index 0f4ecb57214c..360ba480a2a9 100644
> --- a/kernel/pid.c
> +++ b/kernel/pid.c
> @@ -496,6 +496,23 @@ struct pid *find_ge_pid(int nr, struct pid_namespace *ns)
>         return idr_get_next(&ns->idr, &nr);
>  }
>
> +struct pid *pidfd_get_pid(unsigned int fd)
> +{
> +       struct fd f;
> +       struct pid *pid;
> +
> +       f = fdget(fd);
> +       if (!f.file)
> +               return ERR_PTR(-EBADF);
> +
> +       pid = pidfd_pid(f.file);
> +       if (!IS_ERR(pid))
> +               get_pid(pid);
> +
> +       fdput(f);
> +       return pid;
> +}
> +
>  /**
>   * pidfd_create() - Create a new pid file descriptor.
>   *
> --
> 2.25.0.265.gbab2e86ba0-goog
>

Reviewed-by: Suren Baghdasaryan <surenb@google.com>
```