n_tty: Factor canonical mode copy from n_tty_read()

Simplify n_tty_read(); extract complex copy algorithm
into separate function, canon_copy_to_user().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index eddeb7889e627c2f6c931af41f230d1a6eccf360..7fd77746f2d022341740dc6e3b23877e38c6569d 100644 (file)
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1747,6 +1747,62 @@ static int copy_from_read_buf(struct tty_struct *tty,
        return retval;
 }
 
+/**
+ *     canon_copy_to_user      -       copy read data in canonical mode
+ *     @tty: terminal device
+ *     @b: user data
+ *     @nr: size of data
+ *
+ *     Helper function for n_tty_read.  It is only called when ICANON is on;
+ *     it copies characters one at a time from the read buffer to the user
+ *     space buffer.
+ *
+ *     Called under the atomic_read_lock mutex
+ */
+
+static int canon_copy_to_user(struct tty_struct *tty,
+                             unsigned char __user **b,
+                             size_t *nr)
+{
+       struct n_tty_data *ldata = tty->disc_data;
+       unsigned long flags;
+       int eol, c;
+
+       /* N.B. avoid overrun if nr == 0 */
+       raw_spin_lock_irqsave(&ldata->read_lock, flags);
+       while (*nr && ldata->read_cnt) {
+
+               eol = test_and_clear_bit(ldata->read_tail, ldata->read_flags);
+               c = ldata->read_buf[ldata->read_tail];
+               ldata->read_tail = (ldata->read_tail+1) & (N_TTY_BUF_SIZE-1);
+               ldata->read_cnt--;
+               if (eol) {
+                       /* 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 (!eol || (c != __DISABLED_CHAR)) {
+                       if (tty_put_user(tty, c, *b))
+                               return -EFAULT;
+                       *b += 1;
+                       *nr -= 1;
+               }
+               if (eol) {
+                       tty_audit_push(tty);
+                       return 0;
+               }
+               raw_spin_lock_irqsave(&ldata->read_lock, flags);
+       }
+       raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
+
+       return 0;
+}
+
 extern ssize_t redirected_tty_write(struct file *, const char __user *,
                                                        size_t, loff_t *);
 
@@ -1916,44 +1972,7 @@ do_it_again:
                }
 
                if (ldata->icanon && !L_EXTPROC(tty)) {
-                       /* N.B. avoid overrun if nr == 0 */
-                       raw_spin_lock_irqsave(&ldata->read_lock, flags);
-                       while (nr && ldata->read_cnt) {
-                               int eol;
-
-                               eol = test_and_clear_bit(ldata->read_tail,
-                                               ldata->read_flags);
-                               c = ldata->read_buf[ldata->read_tail];
-                               ldata->read_tail = ((ldata->read_tail+1) &
-                                                 (N_TTY_BUF_SIZE-1));
-                               ldata->read_cnt--;
-                               if (eol) {
-                                       /* 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 (!eol || (c != __DISABLED_CHAR)) {
-                                       if (tty_put_user(tty, c, b++)) {
-                                               retval = -EFAULT;
-                                               b--;
-                                               raw_spin_lock_irqsave(&ldata->read_lock, flags);
-                                               break;
-                                       }
-                                       nr--;
-                               }
-                               if (eol) {
-                                       tty_audit_push(tty);
-                                       raw_spin_lock_irqsave(&ldata->read_lock, flags);
-                                       break;
-                               }
-                               raw_spin_lock_irqsave(&ldata->read_lock, flags);
-                       }
-                       raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
+                       retval = canon_copy_to_user(tty, &b, &nr);
                        if (retval)
                                break;
                } else {