linux-kernel - [PATCH 63/80] Simplify devpts_get

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Message-ID: <20081013094304.21645.90958.stgit@localhost.localdomain>
Date:	Mon, 13 Oct 2008 10:43:08 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: [PATCH 63/80] Simplify devpts_get_tty()

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

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@...ibm.com>
Signed-off-by: Alan Cox <alan@...hat.com>
---

 fs/devpts/inode.c |   17 +++++------------
 1 files changed, 5 insertions(+), 12 deletions(-)


diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
index 638db9b..b292ed7 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)

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