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Subject[PATCH 3/7] TTY: extract driver lookup from tty_open
Date
The error handling in tty_open became unbearable. There were many
errors fixed recently. Extract the tty driver lookup from tty_open to
a separate function. This reduces the fail paths significantly and
makes tty_open more readable.

In the next patch we will move the fail path handling to the end of
the function.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
---
drivers/tty/tty_io.c | 93 +++++++++++++++++++++++++++++--------------------
1 files changed, 55 insertions(+), 38 deletions(-)
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 1b90c98..00b8498 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1824,6 +1824,53 @@ static struct tty_struct *tty_open_current_tty(dev_t device, struct file *filp)
}

/**
+ * tty_lookup_driver - lookup a tty driver for a given device file
+ * @device: device number
+ * @filp: file pointer to tty
+ * @noctty: set if the device should not become a controlling tty
+ * @index: index for the device in the @return driver
+ * @return: driver for this inode (with increased refcount)
+ *
+ * If @return is not erroneous, the caller is responsible to decrement the
+ * refcount by tty_driver_kref_put.
+ *
+ * Locking: tty_mutex protects get_tty_driver
+ */
+static struct tty_driver *tty_lookup_driver(dev_t device, struct file *filp,
+ int *noctty, int *index)
+{
+ struct tty_driver *driver;
+
+#ifdef CONFIG_VT
+ if (device == MKDEV(TTY_MAJOR, 0)) {
+ extern struct tty_driver *console_driver;
+ driver = tty_driver_kref_get(console_driver);
+ *index = fg_console;
+ *noctty = 1;
+ return driver;
+ }
+#endif
+ if (device == MKDEV(TTYAUX_MAJOR, 1)) {
+ struct tty_driver *console_driver = console_device(index);
+ if (console_driver) {
+ driver = tty_driver_kref_get(console_driver);
+ if (driver) {
+ /* Don't let /dev/console block */
+ filp->f_flags |= O_NONBLOCK;
+ *noctty = 1;
+ return driver;
+ }
+ }
+ return ERR_PTR(-ENODEV);
+ }
+
+ driver = get_tty_driver(device, index);
+ if (!driver)
+ return ERR_PTR(-ENODEV);
+ return driver;
+}
+
+/**
* tty_open - open a tty device
* @inode: inode of device file
* @filp: file pointer to tty
@@ -1839,7 +1886,7 @@ static struct tty_struct *tty_open_current_tty(dev_t device, struct file *filp)
* The termios state of a pty is reset on first open so that
* settings don't persist across reuse.
*
- * Locking: tty_mutex protects tty, get_tty_driver and tty_init_dev work.
+ * Locking: tty_mutex protects tty, tty_lookup_driver and tty_init_dev.
* tty->count should protect the rest.
* ->siglock protects ->signal/->sighand
*/
@@ -1873,47 +1920,17 @@ retry_open:
mutex_unlock(&tty_mutex);
tty_free_file(filp);
return PTR_ERR(tty);
- } else if (tty)
- goto got_driver;
-
-#ifdef CONFIG_VT
- if (device == MKDEV(TTY_MAJOR, 0)) {
- extern struct tty_driver *console_driver;
- driver = tty_driver_kref_get(console_driver);
- index = fg_console;
- noctty = 1;
- goto got_driver;
- }
-#endif
- if (device == MKDEV(TTYAUX_MAJOR, 1)) {
- struct tty_driver *console_driver = console_device(&index);
- if (console_driver) {
- driver = tty_driver_kref_get(console_driver);
- if (driver) {
- /* Don't let /dev/console block */
- filp->f_flags |= O_NONBLOCK;
- noctty = 1;
- goto got_driver;
- }
+ } else if (!tty) {
+ driver = tty_lookup_driver(device, filp, &noctty, &index);
+ if (IS_ERR(driver)) {
+ tty_unlock();
+ mutex_unlock(&tty_mutex);
+ tty_free_file(filp);
+ return PTR_ERR(driver);
}
- tty_unlock();
- mutex_unlock(&tty_mutex);
- tty_free_file(filp);
- return -ENODEV;
- }

- driver = get_tty_driver(device, &index);
- if (!driver) {
- tty_unlock();
- mutex_unlock(&tty_mutex);
- tty_free_file(filp);
- return -ENODEV;
- }
-got_driver:
- 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);
--
1.7.7



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