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pty: show associative slave of ptmx in fdinfo

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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>
This commit is contained in:
Masatake YAMATO 2017-07-18 06:27:59 +09:00 committed by Greg Kroah-Hartman
parent 199e717f25
commit d01c3289e7
3 changed files with 18 additions and 1 deletions
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8
drivers/tty/pty.c
View file

@ -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 = {

9
drivers/tty/tty_io.c
View file

@ -462,6 +462,14 @@ static int hung_up_tty_fasync(int fd, struct file *file, int on)
return -ENOTTY;
}
static void tty_show_fdinfo(struct seq_file *m, struct file *file)
{
struct tty_struct *tty = file_tty(file);
if (tty && tty->ops && tty->ops->show_fdinfo)
tty->ops->show_fdinfo(tty, m);
}
static const struct file_operations tty_fops = {
.llseek = no_llseek,
.read = tty_read,
@ -472,6 +480,7 @@ static const struct file_operations tty_fops = {
.open = tty_open,
.release = tty_release,
.fasync = tty_fasync,
.show_fdinfo = tty_show_fdinfo,
};
static const struct file_operations console_fops = {

2
include/linux/tty_driver.h
View file

@ -243,6 +243,7 @@
#include <linux/list.h>
#include <linux/cdev.h>
#include <linux/termios.h>
#include <linux/seq_file.h>
struct tty_struct;
struct tty_driver;
@ -285,6 +286,7 @@ struct tty_operations {
int (*set_termiox)(struct tty_struct *tty, struct termiox *tnew);
int (*get_icount)(struct tty_struct *tty,
struct serial_icounter_struct *icount);
void (*show_fdinfo)(struct tty_struct *tty, struct seq_file *m);
#ifdef CONFIG_CONSOLE_POLL
int (*poll_init)(struct tty_driver *driver, int line, char *options);
int (*poll_get_char)(struct tty_driver *driver, int line);