linux-kernel - patch devtmpfs-convert-dirlock-to-a-mutex.patch added to gregkh-2.6 tree

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Message-ID: <12610617252519@kroah.org>
Date:	Thu, 17 Dec 2009 06:55:25 -0800
From:	<gregkh@...e.de>
To:	tglx@...utronix.de, gregkh@...e.de, kay.sievers@...y.org,
	linux-kernel@...r.kernel.org, stable@...nel.org
Subject: patch devtmpfs-convert-dirlock-to-a-mutex.patch added to gregkh-2.6 tree


This is a note to let you know that I've just added the patch titled

    Subject: devtmpfs: Convert dirlock to a mutex

to my gregkh-2.6 tree.  Its filename is

    devtmpfs-convert-dirlock-to-a-mutex.patch

This tree can be found at 
    http://www.kernel.org/pub/linux/kernel/people/gregkh/gregkh-2.6/patches/


>From tglx@...utronix.de  Thu Dec 17 06:44:07 2009
From: Thomas Gleixner <tglx@...utronix.de>
Date: Wed, 16 Dec 2009 21:31:33 -0000
Subject: devtmpfs: Convert dirlock to a mutex
To: LKML <linux-kernel@...r.kernel.org>
Cc: Kay Sievers <kay.sievers@...y.org>, Greg Kroah-Hartman <gregkh@...e.de>
Message-ID: <20091216212730.308081108@...utronix.de>


devtmpfs has a rw_lock dirlock which serializes delete_path and
create_path.

This code was obviously never tested with the usual set of debugging
facilities enabled. In the dirlock held sections the code calls:

 - vfs functions which take mutexes
 - kmalloc(, GFP_KERNEL)

In both code pathes the might sleep warning triggers and spams dmesg.

Convert the rw_lock to a mutex. There is no reason why this needs to
be a rwlock.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Kay Sievers <kay.sievers@...y.org>
Cc: stable <stable@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/base/devtmpfs.c |   12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -32,7 +32,7 @@ static int dev_mount = 1;
 static int dev_mount;
 #endif
 
-static rwlock_t dirlock;
+static DEFINE_MUTEX(dirlock);
 
 static int __init mount_param(char *str)
 {
@@ -93,7 +93,7 @@ static int create_path(const char *nodep
 {
 	int err;
 
-	read_lock(&dirlock);
+	mutex_lock(&dirlock);
 	err = dev_mkdir(nodepath, 0755);
 	if (err == -ENOENT) {
 		char *path;
@@ -117,7 +117,7 @@ static int create_path(const char *nodep
 		}
 		kfree(path);
 	}
-	read_unlock(&dirlock);
+	mutex_unlock(&dirlock);
 	return err;
 }
 
@@ -229,7 +229,7 @@ static int delete_path(const char *nodep
 	if (!path)
 		return -ENOMEM;
 
-	write_lock(&dirlock);
+	mutex_lock(&dirlock);
 	for (;;) {
 		char *base;
 
@@ -241,7 +241,7 @@ static int delete_path(const char *nodep
 		if (err)
 			break;
 	}
-	write_unlock(&dirlock);
+	mutex_unlock(&dirlock);
 
 	kfree(path);
 	return err;
@@ -352,8 +352,6 @@ int __init devtmpfs_init(void)
 	int err;
 	struct vfsmount *mnt;
 
-	rwlock_init(&dirlock);
-
 	err = register_filesystem(&dev_fs_type);
 	if (err) {
 		printk(KERN_ERR "devtmpfs: unable to register devtmpfs "

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