devpts: factor out PTY index allocation

Factor out the code used to allocate/free a pts index into new interfaces,
devpts_new_index() and devpts_kill_index().  This localizes the external data
structures used in managing the pts indices.

[akpm@linux-foundation.org: undo accidental mutex2sem conversion]
Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 34 deletions

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index edcb7e471f02..1d298c2cf930 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -91,7 +91,6 @@
 #include <linux/module.h>
 #include <linux/smp_lock.h>
 #include <linux/device.h>
-#include <linux/idr.h>
 #include <linux/wait.h>
 #include <linux/bitops.h>
 #include <linux/delay.h>
@@ -137,9 +136,6 @@ EXPORT_SYMBOL(tty_mutex);
 
 #ifdef CONFIG_UNIX98_PTYS
 extern struct tty_driver *ptm_driver;   /* Unix98 pty masters; for /dev/ptmx */
-extern int pty_limit;                   /* Config limit on Unix98 ptys */
-static DEFINE_IDR(allocated_ptys);
-static DEFINE_MUTEX(allocated_ptys_lock);
 static int ptmx_open(struct inode *, struct file *);
 #endif
 
@@ -2639,15 +2635,9 @@ static void release_dev(struct file *filp)
          */
         release_tty(tty, idx);
 
-#ifdef CONFIG_UNIX98_PTYS
         /* Make this pty number available for reallocation */
-        if (devpts) {
-                mutex_lock(&allocated_ptys_lock);
-                idr_remove(&allocated_ptys, idx);
-                mutex_unlock(&allocated_ptys_lock);
-        }
-#endif
-
+        if (devpts)
+                devpts_kill_index(idx);
 }
 
 /**
@@ -2803,29 +2793,13 @@ static int ptmx_open(struct inode *inode, struct file *filp)
         struct tty_struct *tty;
         int retval;
         int index;
-        int idr_ret;
 
         nonseekable_open(inode, filp);
 
         /* find a device that is not in use. */
-        mutex_lock(&allocated_ptys_lock);
-        if (!idr_pre_get(&allocated_ptys, GFP_KERNEL)) {
-                mutex_unlock(&allocated_ptys_lock);
-                return -ENOMEM;
-        }
-        idr_ret = idr_get_new(&allocated_ptys, NULL, &index);
-        if (idr_ret < 0) {
-                mutex_unlock(&allocated_ptys_lock);
-                if (idr_ret == -EAGAIN)
-                        return -ENOMEM;
-                return -EIO;
-        }
-        if (index >= pty_limit) {
-                idr_remove(&allocated_ptys, index);
-                mutex_unlock(&allocated_ptys_lock);
-                return -EIO;
-        }
-        mutex_unlock(&allocated_ptys_lock);
+        index = devpts_new_index();
+        if (index < 0)
+                return index;
 
         mutex_lock(&tty_mutex);
         retval = init_dev(ptm_driver, index, &tty);
@@ -2850,9 +2824,7 @@ out1:
         release_dev(filp);
         return retval;
 out:
-        mutex_lock(&allocated_ptys_lock);
-        idr_remove(&allocated_ptys, index);
-        mutex_unlock(&allocated_ptys_lock);
+        devpts_kill_index(index);
         return retval;
 }
 #endif