pty: show associative slave of ptmx in fdinfo
This patch adds "tty-index" field to /proc/PID/fdinfo/N if N
specifies /dev/ptmx. The field shows the index of associative
slave pts.
Though a minor number is given for each pts instance, ptmx is not.
It means there is no way in user-space to know the association between
file descriptors for pts/n and ptmx. (n = 0, 1, ...)
This is different from pipe. About pipe such association can be solved
by inode of pipefs.
Providing the way to know the association between pts/n and ptmx helps
users understand the status of running system. lsof can utilize this field.
Signed-off-by: Masatake YAMATO <yamato@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index 284749f..bb672ac 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -741,6 +741,11 @@ static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
}
}
+static void pty_show_fdinfo(struct tty_struct *tty, struct seq_file *m)
+{
+ seq_printf(m, "tty-index:\t%d\n", tty->index);
+}
+
static const struct tty_operations ptm_unix98_ops = {
.lookup = ptm_unix98_lookup,
.install = pty_unix98_install,
@@ -755,7 +760,8 @@ static const struct tty_operations ptm_unix98_ops = {
.ioctl = pty_unix98_ioctl,
.compat_ioctl = pty_unix98_compat_ioctl,
.resize = pty_resize,
- .cleanup = pty_cleanup
+ .cleanup = pty_cleanup,
+ .show_fdinfo = pty_show_fdinfo,
};
static const struct tty_operations pty_unix98_ops = {