[PATCH 49/76] tty: Move parts of tty_init_dev into new functions

Alan Cox
2008-10-05T16:22:51Z

From: Sukadev Bhattiprolu <sukadev@us.ibm.com>

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>
---

drivers/char/tty_io.c | 139 +++++++++++++++++++++++++++++++------------------
1 files changed, 87 insertions(+), 52 deletions(-)

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index fdcc43c..a540849 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;