Revert "TTY: call tty_driver_lookup_tty unconditionally"

This reverts commit 631180aca723cb92e128fdac5fd144e913ca84e5.

It caused problems when /dev/tty is a pty:
	https://lkml.org/lkml/2011/10/12/401

Cc: Jiri Slaby <jslaby@suse.cz>
Cc: stable <stable@vger.kernel.org>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Alan Cox <alan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 0425170d9ed62954416cba3ca1c356b4a8498d8d..767ecbb4761a9b24eb1af90d58b72c83e8d14b05 100644 (file)
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1821,7 +1821,7 @@ int tty_release(struct inode *inode, struct file *filp)
 
 static int tty_open(struct inode *inode, struct file *filp)
 {
-       struct tty_struct *tty;
+       struct tty_struct *tty = NULL;
        int noctty, retval;
        struct tty_driver *driver;
        int index;
@@ -1892,14 +1892,17 @@ retry_open:
                return -ENODEV;
        }
 got_driver:
-       /* check whether we're reopening an existing tty */
-       tty = tty_driver_lookup_tty(driver, inode, index);
-       if (IS_ERR(tty)) {
-               tty_unlock();
-               mutex_unlock(&tty_mutex);
-               tty_driver_kref_put(driver);
-               tty_free_file(filp);
-               return PTR_ERR(tty);
+       if (!tty) {
+               /* check whether we're reopening an existing tty */
+               tty = tty_driver_lookup_tty(driver, inode, index);
+
+               if (IS_ERR(tty)) {
+                       tty_unlock();
+                       mutex_unlock(&tty_mutex);
+                       tty_driver_kref_put(driver);
+                       tty_free_file(filp);
+                       return PTR_ERR(tty);
+               }
        }
 
        if (tty) {