Merge branch 'nsfs' into for-next

fs/Makefile

@@ -11,7 +11,7 @@ obj-y :=	open.o read_write.o file_table.o super.o \
 		attr.o bad_inode.o file.o filesystems.o namespace.o \
 		seq_file.o xattr.o libfs.o fs-writeback.o \
 		pnode.o splice.o sync.o utimes.o \
-		stack.o fs_struct.o statfs.o fs_pin.o
+		stack.o fs_struct.o statfs.o fs_pin.o nsfs.o
 
 ifeq ($(CONFIG_BLOCK),y)
 obj-y +=	buffer.o block_dev.o direct-io.o mpage.o

fs/internal.h

@@ -147,3 +147,8 @@ extern const struct file_operations pipefifo_fops;
  */
 extern void sb_pin_kill(struct super_block *sb);
 extern void mnt_pin_kill(struct mount *m);
+
+/*
+ * fs/nsfs.c
+ */
+extern struct dentry_operations ns_dentry_operations;

fs/mount.h

@@ -1,10 +1,11 @@
 #include <linux/mount.h>
 #include <linux/seq_file.h>
 #include <linux/poll.h>
+#include <linux/ns_common.h>
 
 struct mnt_namespace {
 	atomic_t		count;
-	unsigned int		proc_inum;
+	struct ns_common	ns;
 	struct mount *	root;
 	struct list_head	list;
 	struct user_namespace	*user_ns;

fs/namespace.c

@@ -1569,17 +1569,13 @@ SYSCALL_DEFINE1(oldumount, char __user *, name)
 static bool is_mnt_ns_file(struct dentry *dentry)
 {
 	/* Is this a proxy for a mount namespace? */
-	struct inode *inode = dentry->d_inode;
-	struct proc_ns *ei;
+	return dentry->d_op == &ns_dentry_operations &&
+	       dentry->d_fsdata == &mntns_operations;
+}
 
-	if (!proc_ns_inode(inode))
-		return false;
-
-	ei = get_proc_ns(inode);
-	if (ei->ns_ops != &mntns_operations)
-		return false;
-
-	return true;
+struct mnt_namespace *to_mnt_ns(struct ns_common *ns)
+{
+	return container_of(ns, struct mnt_namespace, ns);
 }
 
 static bool mnt_ns_loop(struct dentry *dentry)
@@ -1591,7 +1587,7 @@ static bool mnt_ns_loop(struct dentry *dentry)
 	if (!is_mnt_ns_file(dentry))
 		return false;
 
-	mnt_ns = get_proc_ns(dentry->d_inode)->ns;
+	mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode));
 	return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
 }
 
@@ -2020,7 +2016,10 @@ static int do_loopback(struct path *path, const char *old_name,
 	if (IS_MNT_UNBINDABLE(old))
 		goto out2;
 
-	if (!check_mnt(parent) || !check_mnt(old))
+	if (!check_mnt(parent))
+		goto out2;
+
+	if (!check_mnt(old) && old_path.dentry->d_op != &ns_dentry_operations)
 		goto out2;
 
 	if (!recurse && has_locked_children(old, old_path.dentry))
@@ -2640,7 +2639,7 @@ dput_out:
 
 static void free_mnt_ns(struct mnt_namespace *ns)
 {
-	proc_free_inum(ns->proc_inum);
+	ns_free_inum(&ns->ns);
 	put_user_ns(ns->user_ns);
 	kfree(ns);
 }
@@ -2662,11 +2661,12 @@ static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
 	new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
 	if (!new_ns)
 		return ERR_PTR(-ENOMEM);
-	ret = proc_alloc_inum(&new_ns->proc_inum);
+	ret = ns_alloc_inum(&new_ns->ns);
 	if (ret) {
 		kfree(new_ns);
 		return ERR_PTR(ret);
 	}
+	new_ns->ns.ops = &mntns_operations;
 	new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
 	atomic_set(&new_ns->count, 1);
 	new_ns->root = NULL;
@@ -3144,31 +3144,31 @@ found:
 	return visible;
 }
 
-static void *mntns_get(struct task_struct *task)
+static struct ns_common *mntns_get(struct task_struct *task)
 {
-	struct mnt_namespace *ns = NULL;
+	struct ns_common *ns = NULL;
 	struct nsproxy *nsproxy;
 
 	task_lock(task);
 	nsproxy = task->nsproxy;
 	if (nsproxy) {
-		ns = nsproxy->mnt_ns;
-		get_mnt_ns(ns);
+		ns = &nsproxy->mnt_ns->ns;
+		get_mnt_ns(to_mnt_ns(ns));
 	}
 	task_unlock(task);
 
 	return ns;
 }
 
-static void mntns_put(void *ns)
+static void mntns_put(struct ns_common *ns)
 {
-	put_mnt_ns(ns);
+	put_mnt_ns(to_mnt_ns(ns));
 }
 
-static int mntns_install(struct nsproxy *nsproxy, void *ns)
+static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)
 {
 	struct fs_struct *fs = current->fs;
-	struct mnt_namespace *mnt_ns = ns;
+	struct mnt_namespace *mnt_ns = to_mnt_ns(ns);
 	struct path root;
 
 	if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
@@ -3198,17 +3198,10 @@ static int mntns_install(struct nsproxy *nsproxy, void *ns)
 	return 0;
 }
 
-static unsigned int mntns_inum(void *ns)
-{
-	struct mnt_namespace *mnt_ns = ns;
-	return mnt_ns->proc_inum;
-}
-
 const struct proc_ns_operations mntns_operations = {
 	.name		= "mnt",
 	.type		= CLONE_NEWNS,
 	.get		= mntns_get,
 	.put		= mntns_put,
 	.install	= mntns_install,
-	.inum		= mntns_inum,
 };

fs/nsfs.c

@@ -0,0 +1,161 @@
+#include <linux/mount.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/proc_ns.h>
+#include <linux/magic.h>
+#include <linux/ktime.h>
+
+static struct vfsmount *nsfs_mnt;
+
+static const struct file_operations ns_file_operations = {
+	.llseek		= no_llseek,
+};
+
+static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
+{
+	struct inode *inode = dentry->d_inode;
+	const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
+
+	return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
+		ns_ops->name, inode->i_ino);
+}
+
+static void ns_prune_dentry(struct dentry *dentry)
+{
+	struct inode *inode = dentry->d_inode;
+	if (inode) {
+		struct ns_common *ns = inode->i_private;
+		atomic_long_set(&ns->stashed, 0);
+	}
+}
+
+const struct dentry_operations ns_dentry_operations =
+{
+	.d_prune	= ns_prune_dentry,
+	.d_delete	= always_delete_dentry,
+	.d_dname	= ns_dname,
+};
+
+static void nsfs_evict(struct inode *inode)
+{
+	struct ns_common *ns = inode->i_private;
+	clear_inode(inode);
+	ns->ops->put(ns);
+}
+
+void *ns_get_path(struct path *path, struct task_struct *task,
+			const struct proc_ns_operations *ns_ops)
+{
+	struct vfsmount *mnt = mntget(nsfs_mnt);
+	struct qstr qname = { .name = "", };
+	struct dentry *dentry;
+	struct inode *inode;
+	struct ns_common *ns;
+	unsigned long d;
+
+again:
+	ns = ns_ops->get(task);
+	if (!ns) {
+		mntput(mnt);
+		return ERR_PTR(-ENOENT);
+	}
+	rcu_read_lock();
+	d = atomic_long_read(&ns->stashed);
+	if (!d)
+		goto slow;
+	dentry = (struct dentry *)d;
+	if (!lockref_get_not_dead(&dentry->d_lockref))
+		goto slow;
+	rcu_read_unlock();
+	ns_ops->put(ns);
+got_it:
+	path->mnt = mnt;
+	path->dentry = dentry;
+	return NULL;
+slow:
+	rcu_read_unlock();
+	inode = new_inode_pseudo(mnt->mnt_sb);
+	if (!inode) {
+		ns_ops->put(ns);
+		mntput(mnt);
+		return ERR_PTR(-ENOMEM);
+	}
+	inode->i_ino = ns->inum;
+	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
+	inode->i_flags |= S_IMMUTABLE;
+	inode->i_mode = S_IFREG | S_IRUGO;
+	inode->i_fop = &ns_file_operations;
+	inode->i_private = ns;
+
+	dentry = d_alloc_pseudo(mnt->mnt_sb, &qname);
+	if (!dentry) {
+		iput(inode);
+		mntput(mnt);
+		return ERR_PTR(-ENOMEM);
+	}
+	d_instantiate(dentry, inode);
+	dentry->d_fsdata = (void *)ns_ops;
+	d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry);
+	if (d) {
+		d_delete(dentry);	/* make sure ->d_prune() does nothing */
+		dput(dentry);
+		cpu_relax();
+		goto again;
+	}
+	goto got_it;
+}
+
+int ns_get_name(char *buf, size_t size, struct task_struct *task,
+			const struct proc_ns_operations *ns_ops)
+{
+	struct ns_common *ns;
+	int res = -ENOENT;
+	ns = ns_ops->get(task);
+	if (ns) {
+		res = snprintf(buf, size, "%s:[%u]", ns_ops->name, ns->inum);
+		ns_ops->put(ns);
+	}
+	return res;
+}
+
+struct file *proc_ns_fget(int fd)
+{
+	struct file *file;
+
+	file = fget(fd);
+	if (!file)
+		return ERR_PTR(-EBADF);
+
+	if (file->f_op != &ns_file_operations)
+		goto out_invalid;
+
+	return file;
+
+out_invalid:
+	fput(file);
+	return ERR_PTR(-EINVAL);
+}
+
+static const struct super_operations nsfs_ops = {
+	.statfs = simple_statfs,
+	.evict_inode = nsfs_evict,
+};
+static struct dentry *nsfs_mount(struct file_system_type *fs_type,
+			int flags, const char *dev_name, void *data)
+{
+	return mount_pseudo(fs_type, "nsfs:", &nsfs_ops,
+			&ns_dentry_operations, NSFS_MAGIC);
+}
+static struct file_system_type nsfs = {
+	.name = "nsfs",
+	.mount = nsfs_mount,
+	.kill_sb = kill_anon_super,
+};
+
+void __init nsfs_init(void)
+{
+	nsfs_mnt = kern_mount(&nsfs);
+	if (IS_ERR(nsfs_mnt))
+		panic("can't set nsfs up\n");
+	nsfs_mnt->mnt_sb->s_flags &= ~MS_NOUSER;
+}

fs/proc/inode.c

@@ -32,8 +32,6 @@ static void proc_evict_inode(struct inode *inode)
 {
 	struct proc_dir_entry *de;
 	struct ctl_table_header *head;
-	const struct proc_ns_operations *ns_ops;
-	void *ns;
 
 	truncate_inode_pages_final(&inode->i_data);
 	clear_inode(inode);
@@ -50,11 +48,6 @@ static void proc_evict_inode(struct inode *inode)
 		RCU_INIT_POINTER(PROC_I(inode)->sysctl, NULL);
 		sysctl_head_put(head);
 	}
-	/* Release any associated namespace */
-	ns_ops = PROC_I(inode)->ns.ns_ops;
-	ns = PROC_I(inode)->ns.ns;
-	if (ns_ops && ns)
-		ns_ops->put(ns);
 }
 
 static struct kmem_cache * proc_inode_cachep;
@@ -73,8 +66,7 @@ static struct inode *proc_alloc_inode(struct super_block *sb)
 	ei->pde = NULL;
 	ei->sysctl = NULL;
 	ei->sysctl_entry = NULL;
-	ei->ns.ns = NULL;
-	ei->ns.ns_ops = NULL;
+	ei->ns_ops = NULL;
 	inode = &ei->vfs_inode;
 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 	return inode;

fs/proc/internal.h

@@ -64,7 +64,7 @@ struct proc_inode {
 	struct proc_dir_entry *pde;
 	struct ctl_table_header *sysctl;
 	struct ctl_table *sysctl_entry;
-	struct proc_ns ns;
+	const struct proc_ns_operations *ns_ops;
 	struct inode vfs_inode;
 };
 

fs/proc/namespaces.c

@@ -1,10 +1,6 @@
 #include <linux/proc_fs.h>
 #include <linux/nsproxy.h>
-#include <linux/sched.h>
 #include <linux/ptrace.h>
-#include <linux/fs_struct.h>
-#include <linux/mount.h>
-#include <linux/path.h>
 #include <linux/namei.h>
 #include <linux/file.h>
 #include <linux/utsname.h>
@@ -34,138 +30,45 @@ static const struct proc_ns_operations *ns_entries[] = {
 	&mntns_operations,
 };
 
-static const struct file_operations ns_file_operations = {
-	.llseek		= no_llseek,
-};
-
-static const struct inode_operations ns_inode_operations = {
-	.setattr	= proc_setattr,
-};
-
-static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
-{
-	struct inode *inode = dentry->d_inode;
-	const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns.ns_ops;
-
-	return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
-		ns_ops->name, inode->i_ino);
-}
-
-const struct dentry_operations ns_dentry_operations =
-{
-	.d_delete	= always_delete_dentry,
-	.d_dname	= ns_dname,
-};
-
-static struct dentry *proc_ns_get_dentry(struct super_block *sb,
-	struct task_struct *task, const struct proc_ns_operations *ns_ops)
-{
-	struct dentry *dentry, *result;
-	struct inode *inode;
-	struct proc_inode *ei;
-	struct qstr qname = { .name = "", };
-	void *ns;
-
-	ns = ns_ops->get(task);
-	if (!ns)
-		return ERR_PTR(-ENOENT);
-
-	dentry = d_alloc_pseudo(sb, &qname);
-	if (!dentry) {
-		ns_ops->put(ns);
-		return ERR_PTR(-ENOMEM);
-	}
-
-	inode = iget_locked(sb, ns_ops->inum(ns));
-	if (!inode) {
-		dput(dentry);
-		ns_ops->put(ns);
-		return ERR_PTR(-ENOMEM);
-	}
-
-	ei = PROC_I(inode);
-	if (inode->i_state & I_NEW) {
-		inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
-		inode->i_op = &ns_inode_operations;
-		inode->i_mode = S_IFREG | S_IRUGO;
-		inode->i_fop = &ns_file_operations;
-		ei->ns.ns_ops = ns_ops;
-		ei->ns.ns = ns;
-		unlock_new_inode(inode);
-	} else {
-		ns_ops->put(ns);
-	}
-
-	d_set_d_op(dentry, &ns_dentry_operations);
-	result = d_instantiate_unique(dentry, inode);
-	if (result) {
-		dput(dentry);
-		dentry = result;
-	}
-
-	return dentry;
-}
-
 static void *proc_ns_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
 	struct inode *inode = dentry->d_inode;
-	struct super_block *sb = inode->i_sb;
-	struct proc_inode *ei = PROC_I(inode);
+	const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns_ops;
 	struct task_struct *task;
 	struct path ns_path;
 	void *error = ERR_PTR(-EACCES);
 
 	task = get_proc_task(inode);
 	if (!task)
-		goto out;
+		return error;
 
-	if (!ptrace_may_access(task, PTRACE_MODE_READ))
-		goto out_put_task;
-
-	ns_path.dentry = proc_ns_get_dentry(sb, task, ei->ns.ns_ops);
-	if (IS_ERR(ns_path.dentry)) {
-		error = ERR_CAST(ns_path.dentry);
-		goto out_put_task;
+	if (ptrace_may_access(task, PTRACE_MODE_READ)) {
+		error = ns_get_path(&ns_path, task, ns_ops);
+		if (!error)
+			nd_jump_link(nd, &ns_path);
 	}
-
-	ns_path.mnt = mntget(nd->path.mnt);
-	nd_jump_link(nd, &ns_path);
-	error = NULL;
-
-out_put_task:
 	put_task_struct(task);
-out:
 	return error;
 }
 
 static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int buflen)
 {
 	struct inode *inode = dentry->d_inode;
-	struct proc_inode *ei = PROC_I(inode);
-	const struct proc_ns_operations *ns_ops = ei->ns.ns_ops;
+	const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns_ops;
 	struct task_struct *task;
-	void *ns;
 	char name[50];
 	int res = -EACCES;
 
 	task = get_proc_task(inode);
 	if (!task)
-		goto out;
+		return res;
 
-	if (!ptrace_may_access(task, PTRACE_MODE_READ))
-		goto out_put_task;
-
-	res = -ENOENT;
-	ns = ns_ops->get(task);
-	if (!ns)
-		goto out_put_task;
-
-	snprintf(name, sizeof(name), "%s:[%u]", ns_ops->name, ns_ops->inum(ns));
-	res = readlink_copy(buffer, buflen, name);
-	ns_ops->put(ns);
-out_put_task:
+	if (ptrace_may_access(task, PTRACE_MODE_READ)) {
+		res = ns_get_name(name, sizeof(name), task, ns_ops);
+		if (res >= 0)
+			res = readlink_copy(buffer, buflen, name);
+	}
 	put_task_struct(task);
-out:
 	return res;
 }
 
@@ -189,7 +92,7 @@ static int proc_ns_instantiate(struct inode *dir,
 	ei = PROC_I(inode);
 	inode->i_mode = S_IFLNK|S_IRWXUGO;
 	inode->i_op = &proc_ns_link_inode_operations;
-	ei->ns.ns_ops = ns_ops;
+	ei->ns_ops = ns_ops;
 
 	d_set_d_op(dentry, &pid_dentry_operations);
 	d_add(dentry, inode);
@@ -267,31 +170,3 @@ const struct inode_operations proc_ns_dir_inode_operations = {
 	.getattr	= pid_getattr,
 	.setattr	= proc_setattr,
 };
-
-struct file *proc_ns_fget(int fd)
-{
-	struct file *file;
-
-	file = fget(fd);
-	if (!file)
-		return ERR_PTR(-EBADF);
-
-	if (file->f_op != &ns_file_operations)
-		goto out_invalid;
-
-	return file;
-
-out_invalid:
-	fput(file);
-	return ERR_PTR(-EINVAL);
-}
-
-struct proc_ns *get_proc_ns(struct inode *inode)
-{
-	return &PROC_I(inode)->ns;
-}
-
-bool proc_ns_inode(struct inode *inode)
-{
-	return inode->i_fop == &ns_file_operations;
-}

include/linux/ipc_namespace.h

@@ -6,6 +6,7 @@
 #include <linux/rwsem.h>
 #include <linux/notifier.h>
 #include <linux/nsproxy.h>
+#include <linux/ns_common.h>
 
 /*
  * ipc namespace events
@@ -68,7 +69,7 @@ struct ipc_namespace {
 	/* user_ns which owns the ipc ns */
 	struct user_namespace *user_ns;
 
-	unsigned int	proc_inum;
+	struct ns_common ns;
 };
 
 extern struct ipc_namespace init_ipc_ns;

include/linux/ns_common.h

@@ -0,0 +1,12 @@
+#ifndef _LINUX_NS_COMMON_H
+#define _LINUX_NS_COMMON_H
+
+struct proc_ns_operations;
+
+struct ns_common {
+	atomic_long_t stashed;
+	const struct proc_ns_operations *ops;
+	unsigned int inum;
+};
+
+#endif

include/linux/pid_namespace.h

@@ -8,6 +8,7 @@
 #include <linux/threads.h>
 #include <linux/nsproxy.h>
 #include <linux/kref.h>
+#include <linux/ns_common.h>
 
 struct pidmap {
        atomic_t nr_free;
@@ -43,7 +44,7 @@ struct pid_namespace {
 	kgid_t pid_gid;
 	int hide_pid;
 	int reboot;	/* group exit code if this pidns was rebooted */
-	unsigned int proc_inum;
+	struct ns_common ns;
 };
 
 extern struct pid_namespace init_pid_ns;

include/linux/proc_ns.h

@@ -4,21 +4,18 @@
 #ifndef _LINUX_PROC_NS_H
 #define _LINUX_PROC_NS_H
 
+#include <linux/ns_common.h>
+
 struct pid_namespace;
 struct nsproxy;
+struct path;
 
 struct proc_ns_operations {
 	const char *name;
 	int type;
-	void *(*get)(struct task_struct *task);
-	void (*put)(void *ns);
-	int (*install)(struct nsproxy *nsproxy, void *ns);
-	unsigned int (*inum)(void *ns);
-};
-
-struct proc_ns {
-	void *ns;
-	const struct proc_ns_operations *ns_ops;
+	struct ns_common *(*get)(struct task_struct *task);
+	void (*put)(struct ns_common *ns);
+	int (*install)(struct nsproxy *nsproxy, struct ns_common *ns);
 };
 
 extern const struct proc_ns_operations netns_operations;
@@ -43,32 +40,38 @@ enum {
 
 extern int pid_ns_prepare_proc(struct pid_namespace *ns);
 extern void pid_ns_release_proc(struct pid_namespace *ns);
-extern struct file *proc_ns_fget(int fd);
-extern struct proc_ns *get_proc_ns(struct inode *);
 extern int proc_alloc_inum(unsigned int *pino);
 extern void proc_free_inum(unsigned int inum);
-extern bool proc_ns_inode(struct inode *inode);
 
 #else /* CONFIG_PROC_FS */
 
 static inline int pid_ns_prepare_proc(struct pid_namespace *ns) { return 0; }
 static inline void pid_ns_release_proc(struct pid_namespace *ns) {}
 
-static inline struct file *proc_ns_fget(int fd)
-{
-	return ERR_PTR(-EINVAL);
-}
-
-static inline struct proc_ns *get_proc_ns(struct inode *inode) { return NULL; }
-
 static inline int proc_alloc_inum(unsigned int *inum)
 {
 	*inum = 1;
 	return 0;
 }
 static inline void proc_free_inum(unsigned int inum) {}
-static inline bool proc_ns_inode(struct inode *inode) { return false; }
 
 #endif /* CONFIG_PROC_FS */
 
+static inline int ns_alloc_inum(struct ns_common *ns)
+{
+	atomic_long_set(&ns->stashed, 0);
+	return proc_alloc_inum(&ns->inum);
+}
+
+#define ns_free_inum(ns) proc_free_inum((ns)->inum)
+
+extern struct file *proc_ns_fget(int fd);
+#define get_proc_ns(inode) ((struct ns_common *)(inode)->i_private)
+extern void *ns_get_path(struct path *path, struct task_struct *task,
+			const struct proc_ns_operations *ns_ops);
+
+extern int ns_get_name(char *buf, size_t size, struct task_struct *task,
+			const struct proc_ns_operations *ns_ops);
+extern void nsfs_init(void);
+
 #endif /* _LINUX_PROC_NS_H */

include/linux/user_namespace.h

@@ -3,6 +3,7 @@
 
 #include <linux/kref.h>
 #include <linux/nsproxy.h>
+#include <linux/ns_common.h>
 #include <linux/sched.h>
 #include <linux/err.h>
 
@@ -26,7 +27,7 @@ struct user_namespace {
 	int			level;
 	kuid_t			owner;
 	kgid_t			group;
-	unsigned int		proc_inum;
+	struct ns_common	ns;
 
 	/* Register of per-UID persistent keyrings for this namespace */
 #ifdef CONFIG_PERSISTENT_KEYRINGS

include/linux/utsname.h

@@ -5,6 +5,7 @@
 #include <linux/sched.h>
 #include <linux/kref.h>
 #include <linux/nsproxy.h>
+#include <linux/ns_common.h>
 #include <linux/err.h>
 #include <uapi/linux/utsname.h>
 
@@ -23,7 +24,7 @@ struct uts_namespace {
 	struct kref kref;
 	struct new_utsname name;
 	struct user_namespace *user_ns;
-	unsigned int proc_inum;
+	struct ns_common ns;
 };
 extern struct uts_namespace init_uts_ns;
 

include/net/net_namespace.h

@@ -26,6 +26,7 @@
 #endif
 #include <net/netns/nftables.h>
 #include <net/netns/xfrm.h>
+#include <linux/ns_common.h>
 
 struct user_namespace;
 struct proc_dir_entry;
@@ -60,7 +61,7 @@ struct net {
 
 	struct user_namespace   *user_ns;	/* Owning user namespace */
 
-	unsigned int		proc_inum;
+	struct ns_common	ns;
 
 	struct proc_dir_entry 	*proc_net;
 	struct proc_dir_entry 	*proc_net_stat;

include/uapi/linux/magic.h

@@ -72,5 +72,6 @@
 #define MTD_INODE_FS_MAGIC      0x11307854
 #define ANON_INODE_FS_MAGIC	0x09041934
 #define BTRFS_TEST_MAGIC	0x73727279
+#define NSFS_MAGIC		0x6e736673
 
 #endif /* __LINUX_MAGIC_H__ */

init/main.c

@@ -78,6 +78,7 @@
 #include <linux/context_tracking.h>
 #include <linux/random.h>
 #include <linux/list.h>
+#include <linux/proc_ns.h>
 
 #include <asm/io.h>
 #include <asm/bugs.h>
@@ -660,6 +661,7 @@ asmlinkage __visible void __init start_kernel(void)
 	/* rootfs populating might need page-writeback */
 	page_writeback_init();
 	proc_root_init();
+	nsfs_init();
 	cgroup_init();
 	cpuset_init();
 	taskstats_init_early();

init/version.c

@@ -35,7 +35,10 @@ struct uts_namespace init_uts_ns = {
 		.domainname	= UTS_DOMAINNAME,
 	},
 	.user_ns = &init_user_ns,
-	.proc_inum = PROC_UTS_INIT_INO,
+	.ns.inum = PROC_UTS_INIT_INO,
+#ifdef CONFIG_UTS_NS
+	.ns.ops = &utsns_operations,
+#endif
 };
 EXPORT_SYMBOL_GPL(init_uts_ns);
 

ipc/msgutil.c

@@ -31,7 +31,10 @@ DEFINE_SPINLOCK(mq_lock);
 struct ipc_namespace init_ipc_ns = {
 	.count		= ATOMIC_INIT(1),
 	.user_ns = &init_user_ns,
-	.proc_inum = PROC_IPC_INIT_INO,
+	.ns.inum = PROC_IPC_INIT_INO,
+#ifdef CONFIG_IPC_NS
+	.ns.ops = &ipcns_operations,
+#endif
 };
 
 atomic_t nr_ipc_ns = ATOMIC_INIT(1);

ipc/namespace.c

@@ -26,16 +26,17 @@ static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
 	if (ns == NULL)
 		return ERR_PTR(-ENOMEM);
 
-	err = proc_alloc_inum(&ns->proc_inum);
+	err = ns_alloc_inum(&ns->ns);
 	if (err) {
 		kfree(ns);
 		return ERR_PTR(err);
 	}
+	ns->ns.ops = &ipcns_operations;
 
 	atomic_set(&ns->count, 1);
 	err = mq_init_ns(ns);
 	if (err) {
-		proc_free_inum(ns->proc_inum);
+		ns_free_inum(&ns->ns);
 		kfree(ns);
 		return ERR_PTR(err);
 	}
@@ -119,7 +120,7 @@ static void free_ipc_ns(struct ipc_namespace *ns)
 	 */
 	ipcns_notify(IPCNS_REMOVED);
 	put_user_ns(ns->user_ns);
-	proc_free_inum(ns->proc_inum);
+	ns_free_inum(&ns->ns);
 	kfree(ns);
 }
 
@@ -149,7 +150,12 @@ void put_ipc_ns(struct ipc_namespace *ns)
 	}
 }
 
-static void *ipcns_get(struct task_struct *task)
+static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
+{
+	return container_of(ns, struct ipc_namespace, ns);
+}
+
+static struct ns_common *ipcns_get(struct task_struct *task)
 {
 	struct ipc_namespace *ns = NULL;
 	struct nsproxy *nsproxy;
@@ -160,17 +166,17 @@ static void *ipcns_get(struct task_struct *task)
 		ns = get_ipc_ns(nsproxy->ipc_ns);
 	task_unlock(task);
 
-	return ns;
+	return ns ? &ns->ns : NULL;
 }
 
-static void ipcns_put(void *ns)
+static void ipcns_put(struct ns_common *ns)
 {
-	return put_ipc_ns(ns);
+	return put_ipc_ns(to_ipc_ns(ns));
 }
 
-static int ipcns_install(struct nsproxy *nsproxy, void *new)
+static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new)
 {
-	struct ipc_namespace *ns = new;
+	struct ipc_namespace *ns = to_ipc_ns(new);
 	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 		return -EPERM;
@@ -182,18 +188,10 @@ static int ipcns_install(struct nsproxy *nsproxy, void *new)
 	return 0;
 }
 
-static unsigned int ipcns_inum(void *vp)
-{
-	struct ipc_namespace *ns = vp;
-
-	return ns->proc_inum;
-}
-
 const struct proc_ns_operations ipcns_operations = {
 	.name		= "ipc",
 	.type		= CLONE_NEWIPC,
 	.get		= ipcns_get,
 	.put		= ipcns_put,
 	.install	= ipcns_install,
-	.inum		= ipcns_inum,
 };