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_buffer.c

@@ -27,9 +27,9 @@
  *	Locking: none
  */
 
-void tty_buffer_free_all(struct tty_struct *tty)
+void tty_buffer_free_all(struct tty_port *port)
 {
-	struct tty_bufhead *buf = &tty->buf;
+	struct tty_bufhead *buf = &port->buf;
 	struct tty_buffer *thead;
 
 	while ((thead = buf->head) != NULL) {
@@ -56,11 +56,11 @@ void tty_buffer_free_all(struct tty_struct *tty)
  *	Locking: Caller must hold tty->buf.lock
  */
 
-static struct tty_buffer *tty_buffer_alloc(struct tty_struct *tty, size_t size)
+static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
 {
 	struct tty_buffer *p;
 
-	if (tty->buf.memory_used + size > 65536)
+	if (port->buf.memory_used + size > 65536)
 		return NULL;
 	p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
 	if (p == NULL)
@@ -72,7 +72,7 @@ static struct tty_buffer *tty_buffer_alloc(struct tty_struct *tty, size_t size)
 	p->read = 0;
 	p->char_buf_ptr = (char *)(p->data);
 	p->flag_buf_ptr = (unsigned char *)p->char_buf_ptr + size;
-	tty->buf.memory_used += size;
+	port->buf.memory_used += size;
 	return p;
 }
 
@@ -87,9 +87,9 @@ static struct tty_buffer *tty_buffer_alloc(struct tty_struct *tty, size_t size)
  *	Locking: Caller must hold tty->buf.lock
  */
 
-static void tty_buffer_free(struct tty_struct *tty, struct tty_buffer *b)
+static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b)
 {
-	struct tty_bufhead *buf = &tty->buf;
+	struct tty_bufhead *buf = &port->buf;
 
 	/* Dumb strategy for now - should keep some stats */
 	buf->memory_used -= b->size;
@@ -114,14 +114,14 @@ static void tty_buffer_free(struct tty_struct *tty, struct tty_buffer *b)
  *	Locking: Caller must hold tty->buf.lock
  */
 
-static void __tty_buffer_flush(struct tty_struct *tty)
+static void __tty_buffer_flush(struct tty_port *port)
 {
-	struct tty_bufhead *buf = &tty->buf;
+	struct tty_bufhead *buf = &port->buf;
 	struct tty_buffer *thead;
 
 	while ((thead = buf->head) != NULL) {
 		buf->head = thead->next;
-		tty_buffer_free(tty, thead);
+		tty_buffer_free(port, thead);
 	}
 	buf->tail = NULL;
 }
@@ -140,7 +140,7 @@ static void __tty_buffer_flush(struct tty_struct *tty)
 void tty_buffer_flush(struct tty_struct *tty)
 {
 	struct tty_port *port = tty->port;
-	struct tty_bufhead *buf = &tty->buf;
+	struct tty_bufhead *buf = &port->buf;
 	unsigned long flags;
 
 	spin_lock_irqsave(&buf->lock, flags);
@@ -155,7 +155,7 @@ void tty_buffer_flush(struct tty_struct *tty)
 				test_bit(TTYP_FLUSHPENDING, &port->iflags) == 0);
 		return;
 	} else
-		__tty_buffer_flush(tty);
+		__tty_buffer_flush(port);
 	spin_unlock_irqrestore(&buf->lock, flags);
 }
 
@@ -171,9 +171,9 @@ void tty_buffer_flush(struct tty_struct *tty)
  *	Locking: Caller must hold tty->buf.lock
  */
 
-static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size)
+static struct tty_buffer *tty_buffer_find(struct tty_port *port, size_t size)
 {
-	struct tty_buffer **tbh = &tty->buf.free;
+	struct tty_buffer **tbh = &port->buf.free;
 	while ((*tbh) != NULL) {
 		struct tty_buffer *t = *tbh;
 		if (t->size >= size) {
@@ -182,14 +182,14 @@ static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size)
 			t->used = 0;
 			t->commit = 0;
 			t->read = 0;
-			tty->buf.memory_used += t->size;
+			port->buf.memory_used += t->size;
 			return t;
 		}
 		tbh = &((*tbh)->next);
 	}
 	/* Round the buffer size out */
 	size = (size + 0xFF) & ~0xFF;
-	return tty_buffer_alloc(tty, size);
+	return tty_buffer_alloc(port, size);
 	/* Should possibly check if this fails for the largest buffer we
 	   have queued and recycle that ? */
 }
@@ -200,11 +200,11 @@ static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size)
  *
  *	Make at least size bytes of linear space available for the tty
  *	buffer. If we fail return the size we managed to find.
- *      Locking: Caller must hold tty->buf.lock
+ *      Locking: Caller must hold port->buf.lock
  */
-static int __tty_buffer_request_room(struct tty_struct *tty, size_t size)
+static int __tty_buffer_request_room(struct tty_port *port, size_t size)
 {
-	struct tty_bufhead *buf = &tty->buf;
+	struct tty_bufhead *buf = &port->buf;
 	struct tty_buffer *b, *n;
 	int left;
 	/* OPTIMISATION: We could keep a per tty "zero" sized buffer to
@@ -218,7 +218,7 @@ static int __tty_buffer_request_room(struct tty_struct *tty, size_t size)
 
 	if (left < size) {
 		/* This is the slow path - looking for new buffers to use */
-		if ((n = tty_buffer_find(tty, size)) != NULL) {
+		if ((n = tty_buffer_find(port, size)) != NULL) {
 			if (b != NULL) {
 				b->next = n;
 				b->commit = b->used;
@@ -241,16 +241,17 @@ static int __tty_buffer_request_room(struct tty_struct *tty, size_t size)
  *	Make at least size bytes of linear space available for the tty
  *	buffer. If we fail return the size we managed to find.
  *
- *	Locking: Takes tty->buf.lock
+ *	Locking: Takes port->buf.lock
  */
 int tty_buffer_request_room(struct tty_struct *tty, size_t size)
 {
+	struct tty_port *port = tty->port;
 	unsigned long flags;
 	int length;
 
-	spin_lock_irqsave(&tty->buf.lock, flags);
-	length = __tty_buffer_request_room(tty, size);
-	spin_unlock_irqrestore(&tty->buf.lock, flags);
+	spin_lock_irqsave(&port->buf.lock, flags);
+	length = __tty_buffer_request_room(port, size);
+	spin_unlock_irqrestore(&port->buf.lock, flags);
 	return length;
 }
 EXPORT_SYMBOL_GPL(tty_buffer_request_room);
@@ -265,13 +266,13 @@ EXPORT_SYMBOL_GPL(tty_buffer_request_room);
  *	Queue a series of bytes to the tty buffering. All the characters
  *	passed are marked with the supplied flag. Returns the number added.
  *
- *	Locking: Called functions may take tty->buf.lock
+ *	Locking: Called functions may take port->buf.lock
  */
 
 int tty_insert_flip_string_fixed_flag(struct tty_struct *tty,
 		const unsigned char *chars, char flag, size_t size)
 {
-	struct tty_bufhead *buf = &tty->buf;
+	struct tty_bufhead *buf = &tty->port->buf;
 	int copied = 0;
 	do {
 		int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
@@ -280,7 +281,7 @@ int tty_insert_flip_string_fixed_flag(struct tty_struct *tty,
 		struct tty_buffer *tb;
 
 		spin_lock_irqsave(&buf->lock, flags);
-		space = __tty_buffer_request_room(tty, goal);
+		space = __tty_buffer_request_room(tty->port, goal);
 		tb = buf->tail;
 		/* If there is no space then tb may be NULL */
 		if (unlikely(space == 0)) {
@@ -311,13 +312,13 @@ EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
  *	the flags array indicates the status of the character. Returns the
  *	number added.
  *
- *	Locking: Called functions may take tty->buf.lock
+ *	Locking: Called functions may take port->buf.lock
  */
 
 int tty_insert_flip_string_flags(struct tty_struct *tty,
 		const unsigned char *chars, const char *flags, size_t size)
 {
-	struct tty_bufhead *buf = &tty->buf;
+	struct tty_bufhead *buf = &tty->port->buf;
 	int copied = 0;
 	do {
 		int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
@@ -326,7 +327,7 @@ int tty_insert_flip_string_flags(struct tty_struct *tty,
 		struct tty_buffer *tb;
 
 		spin_lock_irqsave(&buf->lock, __flags);
-		space = __tty_buffer_request_room(tty, goal);
+		space = __tty_buffer_request_room(tty->port, goal);
 		tb = buf->tail;
 		/* If there is no space then tb may be NULL */
 		if (unlikely(space == 0)) {
@@ -357,12 +358,12 @@ EXPORT_SYMBOL(tty_insert_flip_string_flags);
  *	Note that this function can only be used when the low_latency flag
  *	is unset. Otherwise the workqueue won't be flushed.
  *
- *	Locking: Takes tty->buf.lock
+ *	Locking: Takes port->buf.lock
  */
 
 void tty_schedule_flip(struct tty_struct *tty)
 {
-	struct tty_bufhead *buf = &tty->buf;
+	struct tty_bufhead *buf = &tty->port->buf;
 	unsigned long flags;
 
 	spin_lock_irqsave(&buf->lock, flags);
@@ -385,19 +386,19 @@ EXPORT_SYMBOL(tty_schedule_flip);
  *	that need their own block copy routines into the buffer. There is no
  *	guarantee the buffer is a DMA target!
  *
- *	Locking: May call functions taking tty->buf.lock
+ *	Locking: May call functions taking port->buf.lock
  */
 
 int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars,
-								size_t size)
+		size_t size)
 {
-	struct tty_bufhead *buf = &tty->buf;
+	struct tty_bufhead *buf = &tty->port->buf;
 	int space;
 	unsigned long flags;
 	struct tty_buffer *tb;
 
 	spin_lock_irqsave(&buf->lock, flags);
-	space = __tty_buffer_request_room(tty, size);
+	space = __tty_buffer_request_room(tty->port, size);
 
 	tb = buf->tail;
 	if (likely(space)) {
@@ -423,19 +424,19 @@ EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
  *	that need their own block copy routines into the buffer. There is no
  *	guarantee the buffer is a DMA target!
  *
- *	Locking: May call functions taking tty->buf.lock
+ *	Locking: May call functions taking port->buf.lock
  */
 
 int tty_prepare_flip_string_flags(struct tty_struct *tty,
 			unsigned char **chars, char **flags, size_t size)
 {
-	struct tty_bufhead *buf = &tty->buf;
+	struct tty_bufhead *buf = &tty->port->buf;
 	int space;
 	unsigned long __flags;
 	struct tty_buffer *tb;
 
 	spin_lock_irqsave(&buf->lock, __flags);
-	space = __tty_buffer_request_room(tty, size);
+	space = __tty_buffer_request_room(tty->port, size);
 
 	tb = buf->tail;
 	if (likely(space)) {
@@ -464,13 +465,16 @@ EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);
 
 static void flush_to_ldisc(struct work_struct *work)
 {
-	struct tty_struct *tty =
-		container_of(work, struct tty_struct, buf.work);
-	struct tty_port *port = tty->port;
-	struct tty_bufhead *buf = &tty->buf;
+	struct tty_port *port = container_of(work, struct tty_port, buf.work);
+	struct tty_bufhead *buf = &port->buf;
+	struct tty_struct *tty;
 	unsigned long 	flags;
 	struct tty_ldisc *disc;
 
+	tty = port->itty;
+	if (WARN_RATELIMIT(tty == NULL, "tty is NULL"))
+		return;
+
 	disc = tty_ldisc_ref(tty);
 	if (disc == NULL)	/*  !TTY_LDISC */
 		return;
@@ -489,7 +493,7 @@ static void flush_to_ldisc(struct work_struct *work)
 				if (head->next == NULL)
 					break;
 				buf->head = head->next;
-				tty_buffer_free(tty, head);
+				tty_buffer_free(port, head);
 				continue;
 			}
 			/* Ldisc or user is trying to flush the buffers
@@ -515,7 +519,7 @@ static void flush_to_ldisc(struct work_struct *work)
 	/* We may have a deferred request to flush the input buffer,
 	   if so pull the chain under the lock and empty the queue */
 	if (test_bit(TTYP_FLUSHPENDING, &port->iflags)) {
-		__tty_buffer_flush(tty);
+		__tty_buffer_flush(port);
 		clear_bit(TTYP_FLUSHPENDING, &port->iflags);
 		wake_up(&tty->read_wait);
 	}
@@ -535,7 +539,7 @@ static void flush_to_ldisc(struct work_struct *work)
 void tty_flush_to_ldisc(struct tty_struct *tty)
 {
 	if (!tty->low_latency)
-		flush_work(&tty->buf.work);
+		flush_work(&tty->port->buf.work);
 }
 
 /**
@@ -553,7 +557,7 @@ void tty_flush_to_ldisc(struct tty_struct *tty)
 
 void tty_flip_buffer_push(struct tty_struct *tty)
 {
-	struct tty_bufhead *buf = &tty->buf;
+	struct tty_bufhead *buf = &tty->port->buf;
 	unsigned long flags;
 
 	spin_lock_irqsave(&buf->lock, flags);
@@ -578,9 +582,9 @@ EXPORT_SYMBOL(tty_flip_buffer_push);
  *	Locking: none
  */
 
-void tty_buffer_init(struct tty_struct *tty)
+void tty_buffer_init(struct tty_port *port)
 {
-	struct tty_bufhead *buf = &tty->buf;
+	struct tty_bufhead *buf = &port->buf;
 
 	spin_lock_init(&buf->lock);
 	buf->head = NULL;

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;