From: Cedric Le Goater <clg@fr.ibm.com>

This patch adds a struct mq_namespace holding the common attributes 
of the mqueue namespace. 

The current code is modified to use the default mqueue namespace 
object 'init_mq_ns' and to prepare the ground for futur dynamic 
objects.

Todo:
	- use CONFIG_NAMESPACE when next -mm is released

Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
---
 include/linux/mq_namespace.h |   60 +++++++++++++++++++++++
 ipc/mqueue.c                 |  111 +++++++++++++++++++++++++++----------------
 2 files changed, 130 insertions(+), 41 deletions(-)

Index: 2.6.23-rc8-mm2/include/linux/mq_namespace.h
===================================================================
--- /dev/null
+++ 2.6.23-rc8-mm2/include/linux/mq_namespace.h
@@ -0,0 +1,60 @@
+#ifndef _LINUX_MQ_NAMESPACE_H
+#define _LINUX_MQ_NAMESPACE_H
+
+#include <linux/kref.h>
+
+struct vfsmount;
+
+struct mq_namespace {
+	struct kref	kref;
+	struct vfsmount *mnt;
+
+	unsigned int	queues_count;
+	unsigned int	queues_max;
+	unsigned int	msg_max;
+	unsigned int	msgsize_max;
+};
+
+extern struct mq_namespace init_mq_ns;
+
+#ifdef CONFIG_POSIX_MQUEUE
+
+#define INIT_MQ_NS(ns)		.ns		= &init_mq_ns,
+
+static inline struct mq_namespace *get_mq_ns(struct mq_namespace *ns)
+{
+	if (ns)
+		kref_get(&ns->kref);
+	return ns;
+}
+
+extern struct mq_namespace *copy_mq_ns(unsigned long flags,
+				struct mq_namespace *old_ns);
+extern void free_mq_ns(struct kref *kref);
+
+static inline void put_mq_ns(struct mq_namespace *ns)
+{
+	if (ns)
+		kref_put(&ns->kref, free_mq_ns);
+}
+
+#else
+
+#define INIT_MQ_NS(ns)
+
+static inline struct mq_namespace *get_mq_ns(struct mq_namespace *ns)
+{
+	return ns;
+}
+
+static inline struct mq_namespace *copy_mq_ns(unsigned long flags,
+					struct mq_namespace *old_ns)
+{
+	return old_ns;
+}
+
+static inline void put_mq_ns(struct mq_namespace *ns) { }
+
+#endif /* CONFIG_POSIX_MQUEUE */
+
+#endif /* _LINUX_MQ_H */
Index: 2.6.23-rc8-mm2/ipc/mqueue.c
===================================================================
--- 2.6.23-rc8-mm2.orig/ipc/mqueue.c
+++ 2.6.23-rc8-mm2/ipc/mqueue.c
@@ -31,6 +31,7 @@
 #include <linux/mutex.h>
 #include <linux/nsproxy.h>
 #include <linux/pid.h>
+#include <linux/mq_namespace.h>
 
 #include <net/sock.h>
 #include "util.h"
@@ -87,12 +88,18 @@ static void remove_notification(struct m
 
 static spinlock_t mq_lock;
 static struct kmem_cache *mqueue_inode_cachep;
-static struct vfsmount *mqueue_mnt;
 
-static unsigned int queues_count;
-static unsigned int queues_max 	= DFLT_QUEUESMAX;
-static unsigned int msg_max 	= DFLT_MSGMAX;
-static unsigned int msgsize_max = DFLT_MSGSIZEMAX;
+struct mq_namespace init_mq_ns = {
+	.kref = {
+		.refcount = ATOMIC_INIT(2),
+	},
+	.mnt		= NULL,
+	.queues_count	= 0,
+	.queues_max 	= DFLT_QUEUESMAX,
+	.msg_max 	= DFLT_MSGMAX,
+	.msgsize_max	= DFLT_MSGSIZEMAX,
+};
+
 
 static struct ctl_table_header * mq_sysctl_table;
 
@@ -101,6 +108,21 @@ static inline struct mqueue_inode_info *
 	return container_of(inode, struct mqueue_inode_info, vfs_inode);
 }
 
+struct mq_namespace *copy_mq_ns(unsigned long flags,
+				struct mq_namespace *old_ns)
+{
+	BUG_ON(!old_ns);
+	return get_mq_ns(old_ns);
+}
+
+void free_mq_ns(struct kref *kref)
+{
+	struct mq_namespace *mq_ns;
+
+	mq_ns = container_of(kref, struct mq_namespace, kref);
+	kfree(mq_ns);
+}
+
 static struct inode *mqueue_get_inode(struct super_block *sb, int mode,
 							struct mq_attr *attr)
 {
@@ -235,6 +257,7 @@ static void mqueue_delete_inode(struct i
 	struct user_struct *user;
 	unsigned long mq_bytes;
 	int i;
+	struct mq_namespace *mq_ns = &init_mq_ns;
 
 	if (S_ISDIR(inode->i_mode)) {
 		clear_inode(inode);
@@ -255,7 +278,7 @@ static void mqueue_delete_inode(struct i
 	if (user) {
 		spin_lock(&mq_lock);
 		user->mq_bytes -= mq_bytes;
-		queues_count--;
+		mq_ns->queues_count--;
 		spin_unlock(&mq_lock);
 		free_uid(user);
 	}
@@ -267,20 +290,22 @@ static int mqueue_create(struct inode *d
 	struct inode *inode;
 	struct mq_attr *attr = dentry->d_fsdata;
 	int error;
+	struct mq_namespace *mq_ns = &init_mq_ns;
 
 	spin_lock(&mq_lock);
-	if (queues_count >= queues_max && !capable(CAP_SYS_RESOURCE)) {
+	if (mq_ns->queues_count >= mq_ns->queues_max &&
+		!capable(CAP_SYS_RESOURCE)) {
 		error = -ENOSPC;
 		goto out_lock;
 	}
-	queues_count++;
+	mq_ns->queues_count++;
 	spin_unlock(&mq_lock);
 
 	inode = mqueue_get_inode(dir->i_sb, mode, attr);
 	if (!inode) {
 		error = -ENOMEM;
 		spin_lock(&mq_lock);
-		queues_count--;
+		mq_ns->queues_count--;
 		goto out_lock;
 	}
 
@@ -571,7 +596,7 @@ static void remove_notification(struct m
 	info->notify_owner = NULL;
 }
 
-static int mq_attr_ok(struct mq_attr *attr)
+static int mq_attr_ok(struct mq_namespace *mq_ns, struct mq_attr *attr)
 {
 	if (attr->mq_maxmsg <= 0 || attr->mq_msgsize <= 0)
 		return 0;
@@ -579,8 +604,8 @@ static int mq_attr_ok(struct mq_attr *at
 		if (attr->mq_maxmsg > HARD_MSGMAX)
 			return 0;
 	} else {
-		if (attr->mq_maxmsg > msg_max ||
-				attr->mq_msgsize > msgsize_max)
+		if (attr->mq_maxmsg > mq_ns->msg_max ||
+				attr->mq_msgsize > mq_ns->msgsize_max)
 			return 0;
 	}
 	/* check for overflow */
@@ -596,8 +621,9 @@ static int mq_attr_ok(struct mq_attr *at
 /*
  * Invoked when creating a new queue via sys_mq_open
  */
-static struct file *do_create(struct dentry *dir, struct dentry *dentry,
-			int oflag, mode_t mode, struct mq_attr __user *u_attr)
+static struct file *do_create(struct mq_namespace *mq_ns, struct dentry *dir,
+			struct dentry *dentry, int oflag, mode_t mode,
+			struct mq_attr __user *u_attr)
 {
 	struct mq_attr attr;
 	int ret;
@@ -607,7 +633,7 @@ static struct file *do_create(struct den
 		if (copy_from_user(&attr, u_attr, sizeof(attr)))
 			goto out;
 		ret = -EINVAL;
-		if (!mq_attr_ok(&attr))
+		if (!mq_attr_ok(mq_ns, &attr))
 			goto out;
 		/* store for use during create */
 		dentry->d_fsdata = &attr;
@@ -619,33 +645,34 @@ static struct file *do_create(struct den
 	if (ret)
 		goto out;
 
-	return dentry_open(dentry, mqueue_mnt, oflag);
+	return dentry_open(dentry, mq_ns->mnt, oflag);
 
 out:
 	dput(dentry);
-	mntput(mqueue_mnt);
+	mntput(mq_ns->mnt);
 	return ERR_PTR(ret);
 }
 
 /* Opens existing queue */
-static struct file *do_open(struct dentry *dentry, int oflag)
+static struct file *do_open(struct mq_namespace *mq_ns, struct dentry *dentry,
+			int oflag)
 {
 static int oflag2acc[O_ACCMODE] = { MAY_READ, MAY_WRITE,
 					MAY_READ | MAY_WRITE };
 
 	if ((oflag & O_ACCMODE) == (O_RDWR | O_WRONLY)) {
 		dput(dentry);
-		mntput(mqueue_mnt);
+		mntput(mq_ns->mnt);
 		return ERR_PTR(-EINVAL);
 	}
 
 	if (permission(dentry->d_inode, oflag2acc[oflag & O_ACCMODE], NULL)) {
 		dput(dentry);
-		mntput(mqueue_mnt);
+		mntput(mq_ns->mnt);
 		return ERR_PTR(-EACCES);
 	}
 
-	return dentry_open(dentry, mqueue_mnt, oflag);
+	return dentry_open(dentry, mq_ns->mnt, oflag);
 }
 
 asmlinkage long sys_mq_open(const char __user *u_name, int oflag, mode_t mode,
@@ -655,6 +682,7 @@ asmlinkage long sys_mq_open(const char _
 	struct file *filp;
 	char *name;
 	int fd, error;
+	struct mq_namespace *mq_ns = &init_mq_ns;
 
 	error = audit_mq_open(oflag, mode, u_attr);
 	if (error != 0)
@@ -667,13 +695,13 @@ asmlinkage long sys_mq_open(const char _
 	if (fd < 0)
 		goto out_putname;
 
-	mutex_lock(&mqueue_mnt->mnt_root->d_inode->i_mutex);
-	dentry = lookup_one_len(name, mqueue_mnt->mnt_root, strlen(name));
+	mutex_lock(&mq_ns->mnt->mnt_root->d_inode->i_mutex);
+	dentry = lookup_one_len(name, mq_ns->mnt->mnt_root, strlen(name));
 	if (IS_ERR(dentry)) {
 		error = PTR_ERR(dentry);
 		goto out_err;
 	}
-	mntget(mqueue_mnt);
+	mntget(mq_ns->mnt);
 
 	if (oflag & O_CREAT) {
 		if (dentry->d_inode) {	/* entry already exists */
@@ -681,12 +709,12 @@ asmlinkage long sys_mq_open(const char _
 			error = -EEXIST;
 			if (oflag & O_EXCL)
 				goto out;
-			filp = do_open(dentry, oflag);
+			filp = do_open(mq_ns, dentry, oflag);
 		} else {
-			error = mnt_want_write(mqueue_mnt);
+			error = mnt_want_write(mq_ns->mnt);
 			if (error)
 				goto out;
-			filp = do_create(mqueue_mnt->mnt_root, dentry,
+			filp = do_create(mq_ns, mq_ns->mnt->mnt_root, dentry,
 						oflag, mode, u_attr);
 		}
 	} else {
@@ -694,7 +722,7 @@ asmlinkage long sys_mq_open(const char _
 		if (!dentry->d_inode)
 			goto out;
 		audit_inode(name, dentry);
-		filp = do_open(dentry, oflag);
+		filp = do_open(mq_ns, dentry, oflag);
 	}
 
 	if (IS_ERR(filp)) {
@@ -708,13 +736,13 @@ asmlinkage long sys_mq_open(const char _
 
 out:
 	dput(dentry);
-	mntput(mqueue_mnt);
+	mntput(mq_ns->mnt);
 out_putfd:
 	put_unused_fd(fd);
 out_err:
 	fd = error;
 out_upsem:
-	mutex_unlock(&mqueue_mnt->mnt_root->d_inode->i_mutex);
+	mutex_unlock(&mq_ns->mnt->mnt_root->d_inode->i_mutex);
 out_putname:
 	putname(name);
 	return fd;
@@ -726,14 +754,15 @@ asmlinkage long sys_mq_unlink(const char
 	char *name;
 	struct dentry *dentry;
 	struct inode *inode = NULL;
+	struct mq_namespace *mq_ns = &init_mq_ns;
 
 	name = getname(u_name);
 	if (IS_ERR(name))
 		return PTR_ERR(name);
 
-	mutex_lock_nested(&mqueue_mnt->mnt_root->d_inode->i_mutex,
+	mutex_lock_nested(&mq_ns->mnt->mnt_root->d_inode->i_mutex,
 			I_MUTEX_PARENT);
-	dentry = lookup_one_len(name, mqueue_mnt->mnt_root, strlen(name));
+	dentry = lookup_one_len(name, mq_ns->mnt->mnt_root, strlen(name));
 	if (IS_ERR(dentry)) {
 		err = PTR_ERR(dentry);
 		goto out_unlock;
@@ -747,16 +776,16 @@ asmlinkage long sys_mq_unlink(const char
 	inode = dentry->d_inode;
 	if (inode)
 		atomic_inc(&inode->i_count);
-	err = mnt_want_write(mqueue_mnt);