Simplify devpts_get_tty()

As pointed out by H. Peter Anvin, since the inode for the pty is known,
we don't need to look it up.

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, 5 insertions, 12 deletions

diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index 638db9b769ac..b292ed7ff1ca 100644
--- a/fs/devpts/inode.c
+++ b/fs/devpts/inode.c
@@ -27,6 +27,7 @@
 #define DEVPTS_SUPER_MAGIC 0x1cd1
 
 #define DEVPTS_DEFAULT_MODE 0600
+#define PTMX_MINOR      2
 
 extern int pty_limit;                   /* Config limit on Unix98 ptys */
 static DEFINE_IDA(allocated_ptys);
@@ -247,19 +248,11 @@ int devpts_pty_new(struct inode *ptmx_inode, struct tty_struct *tty)
 
 struct tty_struct *devpts_get_tty(struct inode *pts_inode, int number)
 {
-        struct dentry *dentry = get_node(number);
-        struct tty_struct *tty;
-
-        tty = NULL;
-        if (!IS_ERR(dentry)) {
-                if (dentry->d_inode)
-                        tty = dentry->d_inode->i_private;
-                dput(dentry);
-        }
-
-        mutex_unlock(&devpts_root->d_inode->i_mutex);
+        BUG_ON(pts_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR));
 
-        return tty;
+        if (pts_inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
+                return (struct tty_struct *)pts_inode->i_private;
+        return NULL;
 }
 
 void devpts_pty_kill(struct tty_struct *tty)