1 files changed, 6 insertions, 16 deletions

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 0599b583d21e..1098dd73a4f7 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -104,7 +104,6 @@ struct n_tty_data {
         unsigned int echo_pos;
         unsigned int echo_cnt;
 
-        int canon_data;
         size_t canon_head;
         unsigned int canon_column;
 
@@ -158,7 +157,7 @@ static int receive_room(struct tty_struct *tty)
          * characters will be beeped.
          */
         if (left <= 0)
-                left = ldata->icanon && !ldata->canon_data;
+                left = ldata->icanon && ldata->canon_head == ldata->read_tail;
 
         return left;
 }
@@ -237,14 +236,14 @@ static void reset_buffer_flags(struct n_tty_data *ldata)
         unsigned long flags;
 
         raw_spin_lock_irqsave(&ldata->read_lock, flags);
-        ldata->read_head = ldata->read_tail = 0;
+        ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
         raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
 
         mutex_lock(&ldata->echo_lock);
         ldata->echo_pos = ldata->echo_cnt = ldata->echo_overrun = 0;
         mutex_unlock(&ldata->echo_lock);
 
-        ldata->canon_head = ldata->canon_data = ldata->erasing = 0;
+        ldata->erasing = 0;
         bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
 }
 
@@ -1360,7 +1359,6 @@ handle_newline:
                         set_bit(ldata->read_head & (N_TTY_BUF_SIZE - 1), ldata->read_flags);
                         put_tty_queue_nolock(c, ldata);
                         ldata->canon_head = ldata->read_head;
-                        ldata->canon_data++;
                         raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
                         kill_fasync(&tty->fasync, SIGIO, POLL_IN);
                         if (waitqueue_active(&tty->read_wait))
@@ -1562,7 +1560,6 @@ static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
         if (canon_change) {
                 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
                 ldata->canon_head = ldata->read_tail;
-                ldata->canon_data = 0;
                 ldata->erasing = 0;
         }
 
@@ -1713,7 +1710,7 @@ static inline int input_available_p(struct tty_struct *tty, int amt)
 
         tty_flush_to_ldisc(tty);
         if (ldata->icanon && !L_EXTPROC(tty)) {
-                if (ldata->canon_data)
+                if (ldata->canon_head != ldata->read_tail)
                         return 1;
         } else if (read_cnt(ldata) >= (amt ? amt : 1))
                 return 1;
@@ -1850,15 +1847,8 @@ static int canon_copy_from_read_buf(struct tty_struct *tty,
 
         raw_spin_lock_irqsave(&ldata->read_lock, flags);
         ldata->read_tail += c;
-        if (found) {
+        if (found)
                 __clear_bit(eol, ldata->read_flags);
-                /* this test should be redundant:
-                 * we shouldn't be reading data if
-                 * canon_data is 0
-                 */
-                if (--ldata->canon_data < 0)
-                        ldata->canon_data = 0;
-        }
         raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
 
         if (found)
@@ -2264,7 +2254,7 @@ static unsigned long inq_canon(struct n_tty_data *ldata)
 {
         size_t nr, head, tail;
 
-        if (!ldata->canon_data)
+        if (ldata->canon_head == ldata->read_tail)
                 return 0;
         head = ldata->canon_head;
         tail = ldata->read_tail;