TTY: move tty buffers to tty_port

So this is it. The big step why we did all the work over the past
kernel releases. Now everything is prepared, so nothing protects us
from doing that big step.

           |  |            \  \ nnnn/^l      |  |
           |  |             \  /     /       |  |
           |  '-,.__   =>    \/   ,-`    =>  |  '-,.__
           | O __.´´)        (  .`           | O __.´´)
            ~~~   ~~          ``              ~~~   ~~
The buffers are now in the tty_port structure and we can start
teaching the buffer helpers (insert char/string, flip etc.) to use
tty_port instead of tty_struct all around.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/n_tty.c

@@ -149,8 +149,11 @@ static void n_tty_set_room(struct tty_struct *tty)
 	tty->receive_room = left;
 
 	/* Did this open up the receive buffer? We may need to flip */
-	if (left && !old_left)
-		schedule_work(&tty->buf.work);
+	if (left && !old_left) {
+		WARN_RATELIMIT(tty->port->itty == NULL,
+				"scheduling with invalid itty");
+		schedule_work(&tty->port->buf.work);
+	}
 }
 
 static void put_tty_queue_nolock(unsigned char c, struct n_tty_data *ldata)

drivers/tty/pty.c

@@ -93,7 +93,7 @@ static void pty_unthrottle(struct tty_struct *tty)
 
 static int pty_space(struct tty_struct *to)
 {
-	int n = 8192 - to->buf.memory_used;
+	int n = 8192 - to->port->buf.memory_used;
 	if (n < 0)
 		return 0;
 	return n;

drivers/tty/tty_io.c

@@ -186,7 +186,6 @@ void free_tty_struct(struct tty_struct *tty)
 	if (tty->dev)
 		put_device(tty->dev);
 	kfree(tty->write_buf);
-	tty_buffer_free_all(tty);
 	tty->magic = 0xDEADDEAD;
 	kfree(tty);
 }
@@ -2935,7 +2934,6 @@ void initialize_tty_struct(struct tty_struct *tty,
 	tty_ldisc_init(tty);
 	tty->session = NULL;
 	tty->pgrp = NULL;
-	tty_buffer_init(tty);
 	mutex_init(&tty->legacy_mutex);
 	mutex_init(&tty->termios_mutex);
 	mutex_init(&tty->ldisc_mutex);

drivers/tty/tty_ldisc.c

@@ -512,7 +512,7 @@ static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
 static int tty_ldisc_halt(struct tty_struct *tty)
 {
 	clear_bit(TTY_LDISC, &tty->flags);
-	return cancel_work_sync(&tty->buf.work);
+	return cancel_work_sync(&tty->port->buf.work);
 }
 
 /**
@@ -525,7 +525,7 @@ static void tty_ldisc_flush_works(struct tty_struct *tty)
 {
 	flush_work(&tty->hangup_work);
 	flush_work(&tty->SAK_work);
-	flush_work(&tty->buf.work);
+	flush_work(&tty->port->buf.work);
 }
 
 /**
@@ -704,9 +704,9 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
 	/* Restart the work queue in case no characters kick it off. Safe if
 	   already running */
 	if (work)
-		schedule_work(&tty->buf.work);
+		schedule_work(&tty->port->buf.work);
 	if (o_work)
-		schedule_work(&o_tty->buf.work);
+		schedule_work(&o_tty->port->buf.work);
 	mutex_unlock(&tty->ldisc_mutex);
 	tty_unlock(tty);
 	return retval;
@@ -817,7 +817,7 @@ void tty_ldisc_hangup(struct tty_struct *tty)
 	 */
 	clear_bit(TTY_LDISC, &tty->flags);
 	tty_unlock(tty);
-	cancel_work_sync(&tty->buf.work);
+	cancel_work_sync(&tty->port->buf.work);
 	mutex_unlock(&tty->ldisc_mutex);
 retry:
 	tty_lock(tty);

drivers/tty/tty_port.c

@@ -21,6 +21,7 @@
 void tty_port_init(struct tty_port *port)
 {
 	memset(port, 0, sizeof(*port));
+	tty_buffer_init(port);
 	init_waitqueue_head(&port->open_wait);
 	init_waitqueue_head(&port->close_wait);
 	init_waitqueue_head(&port->delta_msr_wait);
@@ -126,6 +127,7 @@ static void tty_port_destructor(struct kref *kref)
 	struct tty_port *port = container_of(kref, struct tty_port, kref);
 	if (port->xmit_buf)
 		free_page((unsigned long)port->xmit_buf);
+	tty_buffer_free_all(port);
 	if (port->ops->destruct)
 		port->ops->destruct(port);
 	else

include/linux/tty.h

@@ -188,6 +188,7 @@ struct tty_port_operations {
 };
 	
 struct tty_port {
+	struct tty_bufhead	buf;		/* Locked internally */
 	struct tty_struct	*tty;		/* Back pointer */
 	struct tty_struct	*itty;		/* internal back ptr */
 	const struct tty_port_operations *ops;	/* Port operations */
@@ -259,7 +260,6 @@ struct tty_struct {
 
 	struct tty_struct *link;
 	struct fasync_struct *fasync;
-	struct tty_bufhead buf;		/* Locked internally */
 	int alt_speed;		/* For magic substitution of 38400 bps */
 	wait_queue_head_t write_wait;
 	wait_queue_head_t read_wait;
@@ -388,9 +388,9 @@ extern void disassociate_ctty(int priv);
 extern void no_tty(void);
 extern void tty_flip_buffer_push(struct tty_struct *tty);
 extern void tty_flush_to_ldisc(struct tty_struct *tty);
-extern void tty_buffer_free_all(struct tty_struct *tty);
+extern void tty_buffer_free_all(struct tty_port *port);
 extern void tty_buffer_flush(struct tty_struct *tty);
-extern void tty_buffer_init(struct tty_struct *tty);
+extern void tty_buffer_init(struct tty_port *port);
 extern speed_t tty_get_baud_rate(struct tty_struct *tty);
 extern speed_t tty_termios_baud_rate(struct ktermios *termios);
 extern speed_t tty_termios_input_baud_rate(struct ktermios *termios);

include/linux/tty_flip.h

@@ -11,7 +11,7 @@ void tty_schedule_flip(struct tty_struct *tty);
 static inline int tty_insert_flip_char(struct tty_struct *tty,
 					unsigned char ch, char flag)
 {
-	struct tty_buffer *tb = tty->buf.tail;
+	struct tty_buffer *tb = tty->port->buf.tail;
 	if (tb && tb->used < tb->size) {
 		tb->flag_buf_ptr[tb->used] = flag;
 		tb->char_buf_ptr[tb->used++] = ch;