Re: [PATCH] Add cloexec information to fdinfo

KOSAKI Motohiro
2011-06-13T02:54:58Z

(2011/06/10 12:55), drepper@akkadia.org wrote:
> There is one piece of information about a file descriptor which is
> currently not visible from the outside: the close-on-exec flag. The
> /proc/PID/fdinfo/* files have the mode information but this is
> missing. Is the following patch acceptable?
>
> What I don't know is whether the RCU locking is needed given that
> real locks are taken. Someone with more knowledge could just
> remove those two lines.
>
>
> Signed-off-by: Ulrich Drepper <drepper@gmail.com>
>
> base.c | 17 ++++++++++++++---
> 1 file changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 14def99..bda3651 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -1924,12 +1924,23 @@ static int proc_fd_info(struct inode *inode, struct path *path, char *info)
> *path = file->f_path;
> path_get(&file->f_path);
> }
> - if (info)
> + if (info) {
> + int cloexec;
> + struct fdtable *fdt;
> +
> + rcu_read_lock();
> + fdt = files_fdtable(files);
> + cloexec = FD_ISSET(fd, fdt->close_on_exec);
> + rcu_read_unlock();
> +
> snprintf(info, PROC_FDINFO_MAX,
> "pos:\t%lli\n"
> - "flags:\t0%o\n",
> + "flags:\t0%o\n"
> + "cloexec: %d\n",
> (long long) file->f_pos,
> - file->f_flags);
> + file->f_flags,
> + cloexec);
> + }
> spin_unlock(&files->file_lock);
> put_files_struct(files);
> return 0;

I think this is correct and useful. However I don't know fdtable life cycle detail.
cc to linux-fsdevel.