1 files changed, 100 insertions, 112 deletions
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 5e9ca4376d68..6af3f3a0b531 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -56,6 +56,8 @@
  */
 #define WAKEUP_CHARS 256
 
+#define N_TTY_BUF_SIZE 4096
+
 /*
  * This defines the low- and high-watermarks for throttling and
  * unthrottling the TTY driver.  These watermarks are used for
@@ -79,14 +81,6 @@
 #define ECHO_BLOCK		256
 #define ECHO_DISCARD_WATERMARK	N_TTY_BUF_SIZE - (ECHO_BLOCK + 32)
 
-
-#undef N_TTY_TRACE
-#ifdef N_TTY_TRACE
-# define n_tty_trace(f, args...)	trace_printk(f, ##args)
-#else
-# define n_tty_trace(f, args...)	no_printk(f, ##args)
-#endif
-
 struct n_tty_data {
 	/* producer-published */
 	size_t read_head;
@@ -486,18 +480,13 @@ static int do_output_char(u8 c, struct tty_struct *tty, int space)
 static int process_output(u8 c, struct tty_struct *tty)
 {
 	struct n_tty_data *ldata = tty->disc_data;
-	int	space, retval;
 
-	mutex_lock(&ldata->output_lock);
-
-	space = tty_write_room(tty);
-	retval = do_output_char(c, tty, space);
+	guard(mutex)(&ldata->output_lock);
 
-	mutex_unlock(&ldata->output_lock);
-	if (retval < 0)
+	if (do_output_char(c, tty, tty_write_room(tty)) < 0)
 		return -1;
-	else
-		return 0;
+
+	return 0;
 }
 
 /**
@@ -522,17 +511,15 @@ static ssize_t process_output_block(struct tty_struct *tty,
 				    const u8 *buf, unsigned int nr)
 {
 	struct n_tty_data *ldata = tty->disc_data;
-	int	space;
-	int	i;
+	unsigned int space, i;
 	const u8 *cp;
 
-	mutex_lock(&ldata->output_lock);
+	guard(mutex)(&ldata->output_lock);
 
 	space = tty_write_room(tty);
-	if (space <= 0) {
-		mutex_unlock(&ldata->output_lock);
-		return space;
-	}
+	if (space == 0)
+		return 0;
+
 	if (nr > space)
 		nr = space;
 
@@ -544,18 +531,18 @@ static ssize_t process_output_block(struct tty_struct *tty,
 			if (O_ONLRET(tty))
 				ldata->column = 0;
 			if (O_ONLCR(tty))
-				goto break_out;
+				goto do_write;
 			ldata->canon_column = ldata->column;
 			break;
 		case '\r':
 			if (O_ONOCR(tty) && ldata->column == 0)
-				goto break_out;
+				goto do_write;
 			if (O_OCRNL(tty))
-				goto break_out;
+				goto do_write;
 			ldata->canon_column = ldata->column = 0;
 			break;
 		case '\t':
-			goto break_out;
+			goto do_write;
 		case '\b':
 			if (ldata->column > 0)
 				ldata->column--;
@@ -563,18 +550,15 @@ static ssize_t process_output_block(struct tty_struct *tty,
 		default:
 			if (!iscntrl(c)) {
 				if (O_OLCUC(tty))
-					goto break_out;
+					goto do_write;
 				if (!is_continuation(c, tty))
 					ldata->column++;
 			}
 			break;
 		}
 	}
-break_out:
-	i = tty->ops->write(tty, buf, i);
-
-	mutex_unlock(&ldata->output_lock);
-	return i;
+do_write:
+	return tty->ops->write(tty, buf, i);
 }
 
 static int n_tty_process_echo_ops(struct tty_struct *tty, size_t *tail,
@@ -696,7 +680,7 @@ static int n_tty_process_echo_ops(struct tty_struct *tty, size_t *tail,
 static size_t __process_echoes(struct tty_struct *tty)
 {
 	struct n_tty_data *ldata = tty->disc_data;
-	int	space, old_space;
+	unsigned int space, old_space;
 	size_t tail;
 	u8 c;
 
@@ -2034,9 +2018,6 @@ static bool canon_copy_from_read_buf(const struct tty_struct *tty, u8 **kbp,
 	tail = MASK(ldata->read_tail);
 	size = min_t(size_t, tail + n, N_TTY_BUF_SIZE);
 
-	n_tty_trace("%s: nr:%zu tail:%zu n:%zu size:%zu\n",
-		    __func__, *nr, tail, n, size);
-
 	eol = find_next_bit(ldata->read_flags, size, tail);
 	more = n - (size - tail);
 	if (eol == N_TTY_BUF_SIZE && more) {
@@ -2054,9 +2035,6 @@ static bool canon_copy_from_read_buf(const struct tty_struct *tty, u8 **kbp,
 	if (!found || read_buf(ldata, eol) != __DISABLED_CHAR)
 		n = c;
 
-	n_tty_trace("%s: eol:%zu found:%d n:%zu c:%zu tail:%zu more:%zu\n",
-		    __func__, eol, found, n, c, tail, more);
-
 	tty_copy(tty, *kbp, tail, n);
 	*kbp += n;
 	*nr -= n;
@@ -2133,6 +2111,66 @@ static int job_control(struct tty_struct *tty, struct file *file)
 	return __tty_check_change(tty, SIGTTIN);
 }
 
+/*
+ * We still hold the atomic_read_lock and the termios_rwsem, and can just
+ * continue to copy data.
+ */
+static ssize_t n_tty_continue_cookie(struct tty_struct *tty, u8 *kbuf,
+				   size_t nr, void **cookie)
+{
+	struct n_tty_data *ldata = tty->disc_data;
+	u8 *kb = kbuf;
+
+	if (ldata->icanon && !L_EXTPROC(tty)) {
+		/*
+		 * If we have filled the user buffer, see if we should skip an
+		 * EOF character before releasing the lock and returning done.
+		 */
+		if (!nr)
+			canon_skip_eof(ldata);
+		else if (canon_copy_from_read_buf(tty, &kb, &nr))
+			return kb - kbuf;
+	} else {
+		if (copy_from_read_buf(tty, &kb, &nr))
+			return kb - kbuf;
+	}
+
+	/* No more data - release locks and stop retries */
+	n_tty_kick_worker(tty);
+	n_tty_check_unthrottle(tty);
+	up_read(&tty->termios_rwsem);
+	mutex_unlock(&ldata->atomic_read_lock);
+	*cookie = NULL;
+
+	return kb - kbuf;
+}
+
+static int n_tty_wait_for_input(struct tty_struct *tty, struct file *file,
+				struct wait_queue_entry *wait, long *timeout)
+{
+	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
+		return -EIO;
+	if (tty_hung_up_p(file))
+		return 0;
+	/*
+	 * Abort readers for ttys which never actually get hung up.
+	 * See __tty_hangup().
+	 */
+	if (test_bit(TTY_HUPPING, &tty->flags))
+		return 0;
+	if (!*timeout)
+		return 0;
+	if (tty_io_nonblock(tty, file))
+		return -EAGAIN;
+	if (signal_pending(current))
+		return -ERESTARTSYS;
+
+	up_read(&tty->termios_rwsem);
+	*timeout = wait_woken(wait, TASK_INTERRUPTIBLE, *timeout);
+	down_read(&tty->termios_rwsem);
+
+	return 1;
+}
 
 /**
  * n_tty_read		-	read function for tty
@@ -2166,36 +2204,9 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, u8 *kbuf,
 	bool packet;
 	size_t old_tail;
 
-	/*
-	 * Is this a continuation of a read started earler?
-	 *
-	 * If so, we still hold the atomic_read_lock and the
-	 * termios_rwsem, and can just continue to copy data.
-	 */
-	if (*cookie) {
-		if (ldata->icanon && !L_EXTPROC(tty)) {
-			/*
-			 * If we have filled the user buffer, see
-			 * if we should skip an EOF character before
-			 * releasing the lock and returning done.
-			 */
-			if (!nr)
-				canon_skip_eof(ldata);
-			else if (canon_copy_from_read_buf(tty, &kb, &nr))
-				return kb - kbuf;
-		} else {
-			if (copy_from_read_buf(tty, &kb, &nr))
-				return kb - kbuf;
-		}
-
-		/* No more data - release locks and stop retries */
-		n_tty_kick_worker(tty);
-		n_tty_check_unthrottle(tty);
-		up_read(&tty->termios_rwsem);
-		mutex_unlock(&ldata->atomic_read_lock);
-		*cookie = NULL;
-		return kb - kbuf;
-	}
+	/* Is this a continuation of a read started earlier? */
+	if (*cookie)
+		return n_tty_continue_cookie(tty, kbuf, nr, cookie);
 
 	retval = job_control(tty, file);
 	if (retval < 0)
@@ -2250,34 +2261,12 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, u8 *kbuf,
 			tty_buffer_flush_work(tty->port);
 			down_read(&tty->termios_rwsem);
 			if (!input_available_p(tty, 0)) {
-				if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
-					retval = -EIO;
+				int ret = n_tty_wait_for_input(tty, file, &wait,
+							       &timeout);
+				if (ret <= 0) {
+					retval = ret;
 					break;
 				}
-				if (tty_hung_up_p(file))
-					break;
-				/*
-				 * Abort readers for ttys which never actually
-				 * get hung up.  See __tty_hangup().
-				 */
-				if (test_bit(TTY_HUPPING, &tty->flags))
-					break;
-				if (!timeout)
-					break;
-				if (tty_io_nonblock(tty, file)) {
-					retval = -EAGAIN;
-					break;
-				}
-				if (signal_pending(current)) {
-					retval = -ERESTARTSYS;
-					break;
-				}
-				up_read(&tty->termios_rwsem);
-
-				timeout = wait_woken(&wait, TASK_INTERRUPTIBLE,
-						timeout);
-
-				down_read(&tty->termios_rwsem);
 				continue;
 			}
 		}
@@ -2292,21 +2281,8 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, u8 *kbuf,
 				nr--;
 			}
 
-			/*
-			 * Copy data, and if there is more to be had
-			 * and we have nothing more to wait for, then
-			 * let's mark us for retries.
-			 *
-			 * NOTE! We return here with both the termios_sem
-			 * and atomic_read_lock still held, the retries
-			 * will release them when done.
-			 */
-			if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum) {
-more_to_be_read:
-				remove_wait_queue(&tty->read_wait, &wait);
-				*cookie = cookie;
-				return kb - kbuf;
-			}
+			if (copy_from_read_buf(tty, &kb, &nr) && kb - kbuf >= minimum)
+				goto more_to_be_read;
 		}
 
 		n_tty_check_unthrottle(tty);
@@ -2333,6 +2309,18 @@ more_to_be_read:
 		retval = kb - kbuf;
 
 	return retval;
+more_to_be_read:
+	/*
+	 * There is more to be had and we have nothing more to wait for, so
+	 * let's mark us for retries.
+	 *
+	 * NOTE! We return here with both the termios_sem and atomic_read_lock
+	 * still held, the retries will release them when done.
+	 */
+	remove_wait_queue(&tty->read_wait, &wait);
+	*cookie = cookie;
+
+	return kb - kbuf;
 }
 
 /**