Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull vfs pile #2 from Al Viro:
"Next pile (and there'll be one or two more).

The large piece in this one is getting rid of /proc/*/ns/* weirdness;
among other things, it allows to (finally) make nameidata completely
opaque outside of fs/namei.c, making for easier further cleanups in
there"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
coda_venus_readdir(): use file_inode()
fs/namei.c: fold link_path_walk() call into path_init()
path_init(): don't bother with LOOKUP_PARENT in argument
fs/namei.c: new helper (path_cleanup())
path_init(): store the "base" pointer to file in nameidata itself
make default ->i_fop have ->open() fail with ENXIO
make nameidata completely opaque outside of fs/namei.c
kill proc_ns completely
take the targets of /proc/*/ns/* symlinks to separate fs
bury struct proc_ns in fs/proc
copy address of proc_ns_ops into ns_common
new helpers: ns_alloc_inum/ns_free_inum
make proc_ns_operations work with struct ns_common * instead of void *
switch the rest of proc_ns_operations to working with &...->ns
netns: switch ->get()/->put()/->install()/->inum() to working with &net->ns
make mntns ->get()/->put()/->install()/->inum() work with &mnt_ns->ns
common object embedded into various struct ....ns

arch/ia64/kernel/perfmon.c

···
 	return 0;
 }
 
-static int
-pfm_no_open(struct inode *irrelevant, struct file *dontcare)
-{
-	DPRINT(("pfm_no_open called\n"));
-	return -ENXIO;
-}
-
-
-
 static const struct file_operations pfm_file_ops = {
 	.llseek		= no_llseek,
 	.read		= pfm_read,
 	.write		= pfm_write,
 	.poll		= pfm_poll,
 	.unlocked_ioctl = pfm_ioctl,
-	.open		= pfm_no_open,	/* special open code to disallow open via /proc */
 	.fasync		= pfm_fasync,
 	.release	= pfm_close,
 	.flush		= pfm_flush

fs/Makefile

···
 		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/coda/dir.c

···
 	struct coda_file_info *cfi;
 	struct coda_inode_info *cii;
 	struct file *host_file;
-	struct dentry *de;
 	struct venus_dirent *vdir;
 	unsigned long vdir_size = offsetof(struct venus_dirent, d_name);
 	unsigned int type;
···
 	BUG_ON(!cfi || cfi->cfi_magic != CODA_MAGIC);
 	host_file = cfi->cfi_container;
 
-	de = coda_file->f_path.dentry;
-	cii = ITOC(de->d_inode);
+	cii = ITOC(file_inode(coda_file));
 
 	vdir = kmalloc(sizeof(*vdir), GFP_KERNEL);
 	if (!vdir) return -ENOMEM;

fs/inode.c

···
 }
 #endif
 
+static int no_open(struct inode *inode, struct file *file)
+{
+	return -ENXIO;
+}
+
 /**
  * inode_init_always - perform inode structure intialisation
  * @sb: superblock inode belongs to
···
 int inode_init_always(struct super_block *sb, struct inode *inode)
 {
 	static const struct inode_operations empty_iops;
-	static const struct file_operations empty_fops;
+	static const struct file_operations no_open_fops = {.open = no_open};
 	struct address_space *const mapping = &inode->i_data;
 
 	inode->i_sb = sb;
···
 	inode->i_flags = 0;
 	atomic_set(&inode->i_count, 1);
 	inode->i_op = &empty_iops;
-	inode->i_fop = &empty_fops;
+	inode->i_fop = &no_open_fops;
 	inode->__i_nlink = 1;
 	inode->i_opflags = 0;
 	i_uid_write(inode, 0);
···
 	} else if (S_ISFIFO(mode))
 		inode->i_fop = &pipefifo_fops;
 	else if (S_ISSOCK(mode))
-		inode->i_fop = &bad_sock_fops;
+		;	/* leave it no_open_fops */
 	else
 		printk(KERN_DEBUG "init_special_inode: bogus i_mode (%o) for"
 				  " inode %s:%lu\n", mode, inode->i_sb->s_id,

fs/internal.h

···
  */
 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

···
 #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/namei.c

···
 }
 EXPORT_SYMBOL(path_put);
 
+struct nameidata {
+	struct path	path;
+	struct qstr	last;
+	struct path	root;
+	struct inode	*inode; /* path.dentry.d_inode */
+	unsigned int	flags;
+	unsigned	seq, m_seq;
+	int		last_type;
+	unsigned	depth;
+	struct file	*base;
+	char *saved_names[MAX_NESTED_LINKS + 1];
+};
+
 /*
  * Path walking has 2 modes, rcu-walk and ref-walk (see
  * Documentation/filesystems/path-lookup.txt).  In situations when we can't
···
 	nd->inode = nd->path.dentry->d_inode;
 	nd->flags |= LOOKUP_JUMPED;
 }
+
+void nd_set_link(struct nameidata *nd, char *path)
+{
+	nd->saved_names[nd->depth] = path;
+}
+EXPORT_SYMBOL(nd_set_link);
+
+char *nd_get_link(struct nameidata *nd)
+{
+	return nd->saved_names[nd->depth];
+}
+EXPORT_SYMBOL(nd_get_link);
 
 static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
 {
···
 }
 
 static int path_init(int dfd, const char *name, unsigned int flags,
-		     struct nameidata *nd, struct file **fp)
+		     struct nameidata *nd)
 {
 	int retval = 0;
 
 	nd->last_type = LAST_ROOT; /* if there are only slashes... */
-	nd->flags = flags | LOOKUP_JUMPED;
+	nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT;
 	nd->depth = 0;
+	nd->base = NULL;
 	if (flags & LOOKUP_ROOT) {
 		struct dentry *root = nd->root.dentry;
 		struct inode *inode = root->d_inode;
···
 		} else {
 			path_get(&nd->path);
 		}
-		return 0;
+		goto done;
 	}
 
 	nd->root.mnt = NULL;
···
 		nd->path = f.file->f_path;
 		if (flags & LOOKUP_RCU) {
 			if (f.flags & FDPUT_FPUT)
-				*fp = f.file;
+				nd->base = f.file;
 			nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
 			rcu_read_lock();
 		} else {
···
 
 	nd->inode = nd->path.dentry->d_inode;
 	if (!(flags & LOOKUP_RCU))
-		return 0;
+		goto done;
 	if (likely(!read_seqcount_retry(&nd->path.dentry->d_seq, nd->seq)))
-		return 0;
+		goto done;
 	if (!(nd->flags & LOOKUP_ROOT))
 		nd->root.mnt = NULL;
 	rcu_read_unlock();
 	return -ECHILD;
+done:
+	current->total_link_count = 0;
+	return link_path_walk(name, nd);
+}
+
+static void path_cleanup(struct nameidata *nd)
+{
+	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
+		path_put(&nd->root);
+		nd->root.mnt = NULL;
+	}
+	if (unlikely(nd->base))
+		fput(nd->base);
 }
 
 static inline int lookup_last(struct nameidata *nd, struct path *path)
···
 static int path_lookupat(int dfd, const char *name,
 				unsigned int flags, struct nameidata *nd)
 {
-	struct file *base = NULL;
 	struct path path;
 	int err;
 
···
 	 * be handled by restarting a traditional ref-walk (which will always
 	 * be able to complete).
 	 */
-	err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base);
-
-	if (unlikely(err))
-		goto out;
-
-	current->total_link_count = 0;
-	err = link_path_walk(name, nd);
-
+	err = path_init(dfd, name, flags, nd);
 	if (!err && !(flags & LOOKUP_PARENT)) {
 		err = lookup_last(nd, &path);
 		while (err > 0) {
···
 		}
 	}
 
-out:
-	if (base)
-		fput(base);
-
-	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
-		path_put(&nd->root);
-		nd->root.mnt = NULL;
-	}
+	path_cleanup(nd);
 	return err;
 }
 
···
 static int
 path_mountpoint(int dfd, const char *name, struct path *path, unsigned int flags)
 {
-	struct file *base = NULL;
 	struct nameidata nd;
 	int err;
 
-	err = path_init(dfd, name, flags | LOOKUP_PARENT, &nd, &base);
+	err = path_init(dfd, name, flags, &nd);
 	if (unlikely(err))
-		goto out;
-
-	current->total_link_count = 0;
-	err = link_path_walk(name, &nd);
-	if (err)
 		goto out;
 
 	err = mountpoint_last(&nd, path);
···
 		put_link(&nd, &link, cookie);
 	}
 out:
-	if (base)
-		fput(base);
-
-	if (nd.root.mnt && !(nd.flags & LOOKUP_ROOT))
-		path_put(&nd.root);
-
+	path_cleanup(&nd);
 	return err;
 }
 
···
 static struct file *path_openat(int dfd, struct filename *pathname,
 		struct nameidata *nd, const struct open_flags *op, int flags)
 {
-	struct file *base = NULL;
 	struct file *file;
 	struct path path;
 	int opened = 0;
···
 		goto out;
 	}
 
-	error = path_init(dfd, pathname->name, flags | LOOKUP_PARENT, nd, &base);
-	if (unlikely(error))
-		goto out;
-
-	current->total_link_count = 0;
-	error = link_path_walk(pathname->name, nd);
+	error = path_init(dfd, pathname->name, flags, nd);
 	if (unlikely(error))
 		goto out;
 
···
 		put_link(nd, &link, cookie);
 	}
 out:
-	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
-		path_put(&nd->root);
-	if (base)
-		fput(base);
+	path_cleanup(nd);
 	if (!(opened & FILE_OPENED)) {
 		BUG_ON(!error);
 		put_filp(file);

fs/namespace.c

···
 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)
···
 	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;
 }
 
···
 	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))
···
 
 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);
 }
···
 	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;
···
 	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) ||
···
 	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

···
+#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

···
 {
 	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);
···
 		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;
···
 	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

···
 	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

···
 #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>
···
 	&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;
 }
 
···
 	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);
···
 	.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/fs.h

···
 extern int sync_filesystem(struct super_block *);
 extern const struct file_operations def_blk_fops;
 extern const struct file_operations def_chr_fops;
-extern const struct file_operations bad_sock_fops;
 #ifdef CONFIG_BLOCK
 extern int ioctl_by_bdev(struct block_device *, unsigned, unsigned long);
 extern int blkdev_ioctl(struct block_device *, fmode_t, unsigned, unsigned long);

include/linux/ipc_namespace.h

···
 #include <linux/rwsem.h>
 #include <linux/notifier.h>
 #include <linux/nsproxy.h>
+#include <linux/ns_common.h>
 
 struct user_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/namei.h

···
 #include <linux/path.h>
 
 struct vfsmount;
+struct nameidata;
 
 enum { MAX_NESTED_LINKS = 8 };
-
-struct nameidata {
-	struct path	path;
-	struct qstr	last;
-	struct path	root;
-	struct inode	*inode; /* path.dentry.d_inode */
-	unsigned int	flags;
-	unsigned	seq, m_seq;
-	int		last_type;
-	unsigned	depth;
-	char *saved_names[MAX_NESTED_LINKS + 1];
-};
 
 /*
  * Type of the last component on LOOKUP_PARENT
···
 extern void unlock_rename(struct dentry *, struct dentry *);
 
 extern void nd_jump_link(struct nameidata *nd, struct path *path);
-
-static inline void nd_set_link(struct nameidata *nd, char *path)
-{
-	nd->saved_names[nd->depth] = path;
-}
-
-static inline char *nd_get_link(struct nameidata *nd)
-{
-	return nd->saved_names[nd->depth];
-}
+extern void nd_set_link(struct nameidata *nd, char *path);
+extern char *nd_get_link(struct nameidata *nd);
 
 static inline void nd_terminate_link(void *name, size_t len, size_t maxlen)
 {

include/linux/ns_common.h

···
+#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

···
 #include <linux/threads.h>
 #include <linux/nsproxy.h>
 #include <linux/kref.h>
+#include <linux/ns_common.h>
 
 struct pidmap {
        atomic_t nr_free;
···
 	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

···
 #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;
···
 
 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)
 {
···
 	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

···
 
 #include <linux/kref.h>
 #include <linux/nsproxy.h>
+#include <linux/ns_common.h>
 #include <linux/sched.h>
 #include <linux/err.h>
 
···
 	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

···
 #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>
 
···
 	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

···
 #endif
 #include <net/netns/nftables.h>
 #include <net/netns/xfrm.h>
+#include <linux/ns_common.h>
 
 struct user_namespace;
 struct proc_dir_entry;
···
 
 	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

···
 #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

···
 #include <linux/random.h>
 #include <linux/list.h>
 #include <linux/integrity.h>
+#include <linux/proc_ns.h>
 
 #include <asm/io.h>
 #include <asm/bugs.h>
···
 	/* rootfs populating might need page-writeback */
 	page_writeback_init();
 	proc_root_init();
+	nsfs_init();
 	cgroup_init();
 	cpuset_init();
 	taskstats_init_early();

init/version.c

···
 		.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

···
 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

···
 	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);
 	}
···
 	atomic_dec(&nr_ipc_ns);
 
 	put_user_ns(ns->user_ns);
-	proc_free_inum(ns->proc_inum);
+	ns_free_inum(&ns->ns);
 	kfree(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;
···
 		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;
···
 	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,
 };

kernel/nsproxy.c

···
 
 SYSCALL_DEFINE2(setns, int, fd, int, nstype)
 {
-	const struct proc_ns_operations *ops;
 	struct task_struct *tsk = current;
 	struct nsproxy *new_nsproxy;
-	struct proc_ns *ei;
 	struct file *file;
+	struct ns_common *ns;
 	int err;
 
 	file = proc_ns_fget(fd);
···
 		return PTR_ERR(file);
 
 	err = -EINVAL;
-	ei = get_proc_ns(file_inode(file));
-	ops = ei->ns_ops;
-	if (nstype && (ops->type != nstype))
+	ns = get_proc_ns(file_inode(file));
+	if (nstype && (ns->ops->type != nstype))
 		goto out;
 
 	new_nsproxy = create_new_namespaces(0, tsk, current_user_ns(), tsk->fs);
···
 		goto out;
 	}
 
-	err = ops->install(new_nsproxy, ei->ns);
+	err = ns->ops->install(new_nsproxy, ns);
 	if (err) {
 		free_nsproxy(new_nsproxy);
 		goto out;

kernel/pid.c

···
 	.level = 0,
 	.child_reaper = &init_task,
 	.user_ns = &init_user_ns,
-	.proc_inum = PROC_PID_INIT_INO,
+	.ns.inum = PROC_PID_INIT_INO,
+#ifdef CONFIG_PID_NS
+	.ns.ops = &pidns_operations,
+#endif
 };
 EXPORT_SYMBOL_GPL(init_pid_ns);
 

kernel/pid_namespace.c

···
 	if (ns->pid_cachep == NULL)
 		goto out_free_map;
 
-	err = proc_alloc_inum(&ns->proc_inum);
+	err = ns_alloc_inum(&ns->ns);
 	if (err)
 		goto out_free_map;
+	ns->ns.ops = &pidns_operations;
 
 	kref_init(&ns->kref);
 	ns->level = level;
···
 {
 	int i;
 
-	proc_free_inum(ns->proc_inum);
+	ns_free_inum(&ns->ns);
 	for (i = 0; i < PIDMAP_ENTRIES; i++)
 		kfree(ns->pidmap[i].page);
 	put_user_ns(ns->user_ns);
···
 	return 0;
 }
 
-static void *pidns_get(struct task_struct *task)
+static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
+{
+	return container_of(ns, struct pid_namespace, ns);
+}
+
+static struct ns_common *pidns_get(struct task_struct *task)
 {
 	struct pid_namespace *ns;
 
···
 		get_pid_ns(ns);
 	rcu_read_unlock();
 
-	return ns;
+	return ns ? &ns->ns : NULL;
 }
 
-static void pidns_put(void *ns)
+static void pidns_put(struct ns_common *ns)
 {
-	put_pid_ns(ns);
+	put_pid_ns(to_pid_ns(ns));
 }
 
-static int pidns_install(struct nsproxy *nsproxy, void *ns)
+static int pidns_install(struct nsproxy *nsproxy, struct ns_common *ns)
 {
 	struct pid_namespace *active = task_active_pid_ns(current);
-	struct pid_namespace *ancestor, *new = ns;
+	struct pid_namespace *ancestor, *new = to_pid_ns(ns);
 
 	if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
 	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
···
 	return 0;
 }
 
-static unsigned int pidns_inum(void *ns)
-{
-	struct pid_namespace *pid_ns = ns;
-	return pid_ns->proc_inum;
-}
-
 const struct proc_ns_operations pidns_operations = {
 	.name		= "pid",
 	.type		= CLONE_NEWPID,
 	.get		= pidns_get,
 	.put		= pidns_put,
 	.install	= pidns_install,
-	.inum		= pidns_inum,
 };
 
 static __init int pid_namespaces_init(void)

kernel/user.c

···
 	.count = ATOMIC_INIT(3),
 	.owner = GLOBAL_ROOT_UID,
 	.group = GLOBAL_ROOT_GID,
-	.proc_inum = PROC_USER_INIT_INO,
+	.ns.inum = PROC_USER_INIT_INO,
+#ifdef CONFIG_USER_NS
+	.ns.ops = &userns_operations,
+#endif
 #ifdef CONFIG_PERSISTENT_KEYRINGS
 	.persistent_keyring_register_sem =
 	__RWSEM_INITIALIZER(init_user_ns.persistent_keyring_register_sem),

kernel/user_namespace.c

···
 	if (!ns)
 		return -ENOMEM;
 
-	ret = proc_alloc_inum(&ns->proc_inum);
+	ret = ns_alloc_inum(&ns->ns);
 	if (ret) {
 		kmem_cache_free(user_ns_cachep, ns);
 		return ret;
 	}
+	ns->ns.ops = &userns_operations;
 
 	atomic_set(&ns->count, 1);
 	/* Leave the new->user_ns reference with the new user namespace. */
···
 #ifdef CONFIG_PERSISTENT_KEYRINGS
 		key_put(ns->persistent_keyring_register);
 #endif
-		proc_free_inum(ns->proc_inum);
+		ns_free_inum(&ns->ns);
 		kmem_cache_free(user_ns_cachep, ns);
 		ns = parent;
 	} while (atomic_dec_and_test(&parent->count));
···
 	return false;
 }
 
-static void *userns_get(struct task_struct *task)
+static inline struct user_namespace *to_user_ns(struct ns_common *ns)
+{
+	return container_of(ns, struct user_namespace, ns);
+}
+
+static struct ns_common *userns_get(struct task_struct *task)
 {
 	struct user_namespace *user_ns;
 
···
 	user_ns = get_user_ns(__task_cred(task)->user_ns);
 	rcu_read_unlock();
 
-	return user_ns;
+	return user_ns ? &user_ns->ns : NULL;
 }
 
-static void userns_put(void *ns)
+static void userns_put(struct ns_common *ns)
 {
-	put_user_ns(ns);
+	put_user_ns(to_user_ns(ns));
 }
 
-static int userns_install(struct nsproxy *nsproxy, void *ns)
+static int userns_install(struct nsproxy *nsproxy, struct ns_common *ns)
 {
-	struct user_namespace *user_ns = ns;
+	struct user_namespace *user_ns = to_user_ns(ns);
 	struct cred *cred;
 
 	/* Don't allow gaining capabilities by reentering
···
 	return commit_creds(cred);
 }
 
-static unsigned int userns_inum(void *ns)
-{
-	struct user_namespace *user_ns = ns;
-	return user_ns->proc_inum;
-}
-
 const struct proc_ns_operations userns_operations = {
 	.name		= "user",
 	.type		= CLONE_NEWUSER,
 	.get		= userns_get,
 	.put		= userns_put,
 	.install	= userns_install,
-	.inum		= userns_inum,
 };
 
 static __init int user_namespaces_init(void)

kernel/utsname.c

···
 	if (!ns)
 		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 = &utsns_operations;
 
 	down_read(&uts_sem);
 	memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
···
 
 	ns = container_of(kref, struct uts_namespace, kref);
 	put_user_ns(ns->user_ns);
-	proc_free_inum(ns->proc_inum);
+	ns_free_inum(&ns->ns);
 	kfree(ns);
 }
 
-static void *utsns_get(struct task_struct *task)
+static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
+{
+	return container_of(ns, struct uts_namespace, ns);
+}
+
+static struct ns_common *utsns_get(struct task_struct *task)
 {
 	struct uts_namespace *ns = NULL;
 	struct nsproxy *nsproxy;
···
 	}
 	task_unlock(task);
 
-	return ns;
+	return ns ? &ns->ns : NULL;
 }
 
-static void utsns_put(void *ns)
+static void utsns_put(struct ns_common *ns)
 {
-	put_uts_ns(ns);
+	put_uts_ns(to_uts_ns(ns));
 }
 
-static int utsns_install(struct nsproxy *nsproxy, void *new)
+static int utsns_install(struct nsproxy *nsproxy, struct ns_common *new)
 {
-	struct uts_namespace *ns = new;
+	struct uts_namespace *ns = to_uts_ns(new);
 
 	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
···
 	return 0;
 }
 
-static unsigned int utsns_inum(void *vp)
-{
-	struct uts_namespace *ns = vp;
-
-	return ns->proc_inum;
-}
-
 const struct proc_ns_operations utsns_operations = {
 	.name		= "uts",
 	.type		= CLONE_NEWUTS,
 	.get		= utsns_get,
 	.put		= utsns_put,
 	.install	= utsns_install,
-	.inum		= utsns_inum,
 };

net/Makefile

···
 # Rewritten to use lists instead of if-statements.
 #
 
-obj-y	:= nonet.o
-
 obj-$(CONFIG_NET)		:= socket.o core/
 
 tmp-$(CONFIG_COMPAT) 		:= compat.o

net/core/net_namespace.c

···
 
 struct net *get_net_ns_by_fd(int fd)
 {
-	struct proc_ns *ei;
 	struct file *file;
+	struct ns_common *ns;
 	struct net *net;
 
 	file = proc_ns_fget(fd);
 	if (IS_ERR(file))
 		return ERR_CAST(file);
 
-	ei = get_proc_ns(file_inode(file));
-	if (ei->ns_ops == &netns_operations)
-		net = get_net(ei->ns);
+	ns = get_proc_ns(file_inode(file));
+	if (ns->ops == &netns_operations)
+		net = get_net(container_of(ns, struct net, ns));
 	else
 		net = ERR_PTR(-EINVAL);
 
···
 
 static __net_init int net_ns_net_init(struct net *net)
 {
-	return proc_alloc_inum(&net->proc_inum);
+#ifdef CONFIG_NET_NS
+	net->ns.ops = &netns_operations;
+#endif
+	return ns_alloc_inum(&net->ns);
 }
 
 static __net_exit void net_ns_net_exit(struct net *net)
 {
-	proc_free_inum(net->proc_inum);
+	ns_free_inum(&net->ns);
 }
 
 static struct pernet_operations __net_initdata net_ns_ops = {
···
 EXPORT_SYMBOL_GPL(unregister_pernet_device);
 
 #ifdef CONFIG_NET_NS
-static void *netns_get(struct task_struct *task)
+static struct ns_common *netns_get(struct task_struct *task)
 {
 	struct net *net = NULL;
 	struct nsproxy *nsproxy;
···
 		net = get_net(nsproxy->net_ns);
 	task_unlock(task);
 
-	return net;
+	return net ? &net->ns : NULL;
 }
 
-static void netns_put(void *ns)
+static inline struct net *to_net_ns(struct ns_common *ns)
 {
-	put_net(ns);
+	return container_of(ns, struct net, ns);
 }
 
-static int netns_install(struct nsproxy *nsproxy, void *ns)
+static void netns_put(struct ns_common *ns)
 {
-	struct net *net = ns;
+	put_net(to_net_ns(ns));
+}
+
+static int netns_install(struct nsproxy *nsproxy, struct ns_common *ns)
+{
+	struct net *net = to_net_ns(ns);
 
 	if (!ns_capable(net->user_ns, CAP_SYS_ADMIN) ||
 	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
···
 	return 0;
 }
 
-static unsigned int netns_inum(void *ns)
-{
-	struct net *net = ns;
-	return net->proc_inum;
-}
-
 const struct proc_ns_operations netns_operations = {
 	.name		= "net",
 	.type		= CLONE_NEWNET,
 	.get		= netns_get,
 	.put		= netns_put,
 	.install	= netns_install,
-	.inum		= netns_inum,
 };
 #endif

net/nonet.c

···
-/*
- * net/nonet.c
- *
- * Dummy functions to allow us to configure network support entirely
- * out of the kernel.
- *
- * Distributed under the terms of the GNU GPL version 2.
- * Copyright (c) Matthew Wilcox 2003
- */
-
-#include <linux/module.h>
-#include <linux/errno.h>
-#include <linux/fs.h>
-#include <linux/init.h>
-#include <linux/kernel.h>
-
-static int sock_no_open(struct inode *irrelevant, struct file *dontcare)
-{
-	return -ENXIO;
-}
-
-const struct file_operations bad_sock_fops = {
-	.owner = THIS_MODULE,
-	.open = sock_no_open,
-	.llseek = noop_llseek,
-};

net/socket.c

···
 unsigned int sysctl_net_busy_poll __read_mostly;
 #endif
 
-static int sock_no_open(struct inode *irrelevant, struct file *dontcare);
 static ssize_t sock_aio_read(struct kiocb *iocb, const struct iovec *iov,
 			 unsigned long nr_segs, loff_t pos);
 static ssize_t sock_aio_write(struct kiocb *iocb, const struct iovec *iov,
···
 	.compat_ioctl = compat_sock_ioctl,
 #endif
 	.mmap =		sock_mmap,
-	.open =		sock_no_open,	/* special open code to disallow open via /proc */
 	.release =	sock_close,
 	.fasync =	sock_fasync,
 	.sendpage =	sock_sendpage,
···
 	this_cpu_add(sockets_in_use, 1);
 	return sock;
 }
-
-/*
- *	In theory you can't get an open on this inode, but /proc provides
- *	a back door. Remember to keep it shut otherwise you'll let the
- *	creepy crawlies in.
- */
-
-static int sock_no_open(struct inode *irrelevant, struct file *dontcare)
-{
-	return -ENXIO;
-}
-
-const struct file_operations bad_sock_fops = {
-	.owner = THIS_MODULE,
-	.open = sock_no_open,
-	.llseek = noop_llseek,
-};
 
 /**
  *	sock_release	-	close a socket