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/fs/devpts/inode.c b/fs/devpts/inode.c
index f120e12..285b64a 100644
--- 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 @@
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;