tty: Move parts of tty_init_dev into new functions

Move the 'find-tty' and 'fast-track-open' parts of init_dev() to
separate functions.

Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 87 insertions, 52 deletions

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index fdcc43c8ef3c..a5408496d301 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1204,6 +1204,80 @@ static void tty_line_name(struct tty_driver *driver, int index, char *p)
         sprintf(p, "%s%d", driver->name, index + driver->name_base);
 }
 
+/*
+ *      find_tty() - find an existing tty, if any
+ *      @driver: the driver for the tty
+ *      @idx:    the minor number
+ *
+ *      Return the tty, if found or ERR_PTR() otherwise.
+ *
+ *      Locking: tty_mutex must be held. If tty is found, the mutex must
+ *               be held until the 'fast-open' is also done.
+ */
+struct tty_struct *find_tty(struct tty_driver *driver, int idx)
+{
+        struct tty_struct *tty;
+
+        /* check whether we're reopening an existing tty */
+        if (driver->flags & TTY_DRIVER_DEVPTS_MEM) {
+                tty = devpts_get_tty(idx);
+                /*
+                 * If we don't have a tty here on a slave open, it's because
+                 * the master already started the close process and there's
+                 * no relation between devpts file and tty anymore.
+                 */
+                if (!tty && driver->subtype == PTY_TYPE_SLAVE)
+                        return ERR_PTR(-EIO);
+
+                /*
+                 * tty is safe on because we are called with tty_mutex held
+                 * and release_dev() won't change tty->count or tty->flags
+                 * without grabbing tty_mutex.
+                 */
+                if (tty && driver->subtype == PTY_TYPE_MASTER)
+                        tty = tty->link;
+        } else
+                tty = driver->ttys[idx];
+        return tty;
+}
+
+/*
+ *      fast_tty_open() - fast re-open of an open tty
+ *      @tty    - the tty to open
+ *
+ *      Return 0 on success, -errno on error.
+ *
+ *      Locking: tty_mutex must be held from the time the tty was found
+ *               till this open completes.
+ */
+static int fast_tty_open(struct tty_struct *tty)
+{
+        struct tty_driver *driver = tty->driver;
+
+        if (test_bit(TTY_CLOSING, &tty->flags))
+                return -EIO;
+
+        if (driver->type == TTY_DRIVER_TYPE_PTY &&
+            driver->subtype == PTY_TYPE_MASTER) {
+                /*
+                 * special case for PTY masters: only one open permitted,
+                 * and the slave side open count is incremented as well.
+                 */
+                if (tty->count)
+                        return -EIO;
+
+                tty->link->count++;
+        }
+        tty->count++;
+        tty->driver = driver; /* N.B. why do this every time?? */
+
+        /* FIXME */
+        if (!test_bit(TTY_LDISC, &tty->flags))
+                printk(KERN_ERR "fast_tty_open: no ldisc\n");
+
+        return 0;
+}
+
 /**
  *      tty_init_dev            -       initialise a tty device
  *      @driver: tty driver we are opening a device on
@@ -1238,29 +1312,21 @@ int tty_init_dev(struct tty_driver *driver, int idx,
         int retval = 0;
 
         /* check whether we're reopening an existing tty */
-        if (driver->flags & TTY_DRIVER_DEVPTS_MEM) {
-                tty = devpts_get_tty(idx);
-                /*
-                 * If we don't have a tty here on a slave open, it's because
-                 * the master already started the close process and there's
-                 * no relation between devpts file and tty anymore.
-                 */
-                if (!tty && driver->subtype == PTY_TYPE_SLAVE) {
-                        retval = -EIO;
-                        goto end_init;
-                }
-                /*
-                 * It's safe from now on because tty_init_dev() is called with
-                 * tty_mutex held and tty_release_dev() won't change tty->count
-                 * or tty->flags without having to grab tty_mutex
-                 */
-                if (tty && driver->subtype == PTY_TYPE_MASTER)
-                        tty = tty->link;
-        } else {
-                tty = driver->ttys[idx];
+        tty = find_tty(driver, idx);
+        if (IS_ERR(tty)) {
+                retval = PTR_ERR(tty);
+                goto end_init;
+        }
+
+        if (tty) {
+                retval = fast_tty_open(tty);
+                if (retval)
+                        return retval;
+                *ret_tty = tty;
+                return 0;
         }
-        if (tty) goto fast_track;
 
+        /* Check if pty master is being opened multiple times */
         if (driver->subtype == PTY_TYPE_MASTER &&
                 (driver->flags & TTY_DRIVER_DEVPTS_MEM) && !first_ok) {
                 retval = -EIO;
@@ -1400,37 +1466,6 @@ int tty_init_dev(struct tty_driver *driver, int idx,
 
         if (retval)
                 goto release_mem_out;
-        goto success;
-
-        /*
-         * This fast open can be used if the tty is already open.
-         * No memory is allocated, and the only failures are from
-         * attempting to open a closing tty or attempting multiple
-         * opens on a pty master.
-         */
-fast_track:
-        if (test_bit(TTY_CLOSING, &tty->flags)) {
-                retval = -EIO;
-                goto end_init;
-        }
-        if (driver->type == TTY_DRIVER_TYPE_PTY &&
-            driver->subtype == PTY_TYPE_MASTER) {
-                /*
-                 * special case for PTY masters: only one open permitted,
-                 * and the slave side open count is incremented as well.
-                 */
-                if (tty->count) {
-                        retval = -EIO;
-                        goto end_init;
-                }
-                tty->link->count++;
-        }
-        tty->count++;
-        tty->driver = driver; /* N.B. why do this every time?? */
-
-        /* FIXME */
-        if (!test_bit(TTY_LDISC, &tty->flags))
-                printk(KERN_ERR "tty_init_dev but no ldisc\n");
 success:
         *ret_tty = tty;