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>

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index edcb7e471f029ff7ce829a815ad33e53ece74139..1d298c2cf9301c0a1ac2026577463e6a3a6b1813 100644 (file)
--- 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

diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index f120e1207874715b052788ea9105458da9348145..285b64a8b06e125b1aee42a8317cfd0873d69f20 100644 (file)
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -17,6 +17,8 @@
 #include <linux/namei.h>
 #include <linux/mount.h>
 #include <linux/tty.h>
+#include <linux/mutex.h>
+#include <linux/idr.h>
 #include <linux/devpts_fs.h>
 #include <linux/parser.h>
 #include <linux/fsnotify.h>
@@ -26,6 +28,10 @@
 
 #define DEVPTS_DEFAULT_MODE 0600
 
+extern int pty_limit;                  /* Config limit on Unix98 ptys */
+static DEFINE_IDR(allocated_ptys);
+static DEFINE_MUTEX(allocated_ptys_lock);
+
 static struct vfsmount *devpts_mnt;
 static struct dentry *devpts_root;
 
@@ -171,9 +177,44 @@ static struct dentry *get_node(int num)
        return lookup_one_len(s, root, sprintf(s, "%d", num));
 }
 
+int devpts_new_index(void)
+{
+       int index;
+       int idr_ret;
+
+retry:
+       if (!idr_pre_get(&allocated_ptys, GFP_KERNEL)) {
+               return -ENOMEM;
+       }
+
+       mutex_lock(&allocated_ptys_lock);
+       idr_ret = idr_get_new(&allocated_ptys, NULL, &index);
+       if (idr_ret < 0) {
+               mutex_unlock(&allocated_ptys_lock);
+               if (idr_ret == -EAGAIN)
+                       goto retry;
+               return -EIO;
+       }
+
+       if (index >= pty_limit) {
+               idr_remove(&allocated_ptys, index);
+               mutex_unlock(&allocated_ptys_lock);
+               return -EIO;
+       }
+       mutex_unlock(&allocated_ptys_lock);
+       return index;
+}
+
+void devpts_kill_index(int idx)
+{
+       mutex_lock(&allocated_ptys_lock);
+       idr_remove(&allocated_ptys, idx);
+       mutex_unlock(&allocated_ptys_lock);
+}
+
 int devpts_pty_new(struct tty_struct *tty)
 {
-       int number = tty->index;
+       int number = tty->index; /* tty layer puts index from devpts_new_index() in here */
        struct tty_driver *driver = tty->driver;
        dev_t device = MKDEV(driver->major, driver->minor_start+number);
        struct dentry *dentry;

diff --git a/include/linux/devpts_fs.h b/include/linux/devpts_fs.h
index b672ddc007357bc2cd5395d34e6102f6870315a6..154769cad3f31c7207b3113ec5e00753a4684ee2 100644 (file)
--- a/include/linux/devpts_fs.h
+++ b/include/linux/devpts_fs.h
@@ -17,6 +17,8 @@
 
 #ifdef CONFIG_UNIX98_PTYS
 
+int devpts_new_index(void);
+void devpts_kill_index(int idx);
 int devpts_pty_new(struct tty_struct *tty);      /* mknod in devpts */
 struct tty_struct *devpts_get_tty(int number);  /* get tty structure */
 void devpts_pty_kill(int number);               /* unlink */
@@ -24,6 +26,8 @@ void devpts_pty_kill(int number);              /* unlink */
 #else
 
 /* Dummy stubs in the no-pty case */
+static inline int devpts_new_index(void) { return -EINVAL; }
+static inline void devpts_kill_index(int idx) { }
 static inline int devpts_pty_new(struct tty_struct *tty) { return -EINVAL; }
 static inline struct tty_struct *devpts_get_tty(int number) { return NULL; }
 static inline void devpts_pty_kill(int number) { }