bury struct proc_ns in fs/proc

a) make get_proc_ns() return a pointer to struct ns_common
b) mirror ns_ops in dentry->d_fsdata of ns dentries, so that
is_mnt_ns_file() could get away with fewer dereferences.

That way struct proc_ns becomes invisible outside of fs/proc/*.c

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namespace.c

@@ -1570,16 +1570,7 @@ 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;
-
-	if (!proc_ns_inode(inode))
-		return false;
-
-	ei = get_proc_ns(inode);
-	if (ei->ns_ops != &mntns_operations)
-		return false;
-
-	return true;
+	return proc_ns_inode(inode) && dentry->d_fsdata == &mntns_operations;
 }
 
 struct mnt_namespace *to_mnt_ns(struct ns_common *ns)
@@ -1596,7 +1587,7 @@ static bool mnt_ns_loop(struct dentry *dentry)
 	if (!is_mnt_ns_file(dentry))
 		return false;
 
-	mnt_ns = to_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;
 }
 

fs/proc/internal.h

@@ -57,6 +57,11 @@ union proc_op {
 		struct task_struct *task);
 };
 
+struct proc_ns {
+	struct ns_common *ns;
+	const struct proc_ns_operations *ns_ops;
+};
+
 struct proc_inode {
 	struct pid *pid;
 	int fd;

fs/proc/namespaces.c

@@ -45,7 +45,7 @@ static const struct inode_operations ns_inode_operations = {
 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;
+	const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
 
 	return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
 		ns_ops->name, inode->i_ino);
@@ -75,6 +75,7 @@ static struct dentry *proc_ns_get_dentry(struct super_block *sb,
 		ns_ops->put(ns);
 		return ERR_PTR(-ENOMEM);
 	}
+	dentry->d_fsdata = (void *)ns_ops;
 
 	inode = iget_locked(sb, ns->inum);
 	if (!inode) {
@@ -286,9 +287,9 @@ struct file *proc_ns_fget(int fd)
 	return ERR_PTR(-EINVAL);
 }
 
-struct proc_ns *get_proc_ns(struct inode *inode)
+struct ns_common *get_proc_ns(struct inode *inode)
 {
-	return &PROC_I(inode)->ns;
+	return PROC_I(inode)->ns.ns;
 }
 
 bool proc_ns_inode(struct inode *inode)

include/linux/proc_ns.h

@@ -16,11 +16,6 @@ struct proc_ns_operations {
 	int (*install)(struct nsproxy *nsproxy, struct ns_common *ns);
 };
 
-struct proc_ns {
-	struct ns_common *ns;
-	const struct proc_ns_operations *ns_ops;
-};
-
 extern const struct proc_ns_operations netns_operations;
 extern const struct proc_ns_operations utsns_operations;
 extern const struct proc_ns_operations ipcns_operations;
@@ -44,7 +39,7 @@ 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 struct ns_common *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);
@@ -59,7 +54,7 @@ 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 struct ns_common *get_proc_ns(struct inode *inode) { return NULL; }
 
 static inline int proc_alloc_inum(unsigned int *inum)
 {

kernel/nsproxy.c

@@ -222,7 +222,6 @@ SYSCALL_DEFINE2(setns, int, fd, int, nstype)
 {
 	struct task_struct *tsk = current;
 	struct nsproxy *new_nsproxy;
-	struct proc_ns *ei;
 	struct file *file;
 	struct ns_common *ns;
 	int err;
@@ -232,8 +231,7 @@ SYSCALL_DEFINE2(setns, int, fd, int, nstype)
 		return PTR_ERR(file);
 
 	err = -EINVAL;
-	ei = get_proc_ns(file_inode(file));
-	ns = ei->ns;
+	ns = get_proc_ns(file_inode(file));
 	if (nstype && (ns->ops->type != nstype))
 		goto out;
 

net/core/net_namespace.c

@@ -337,7 +337,6 @@ EXPORT_SYMBOL_GPL(__put_net);
 
 struct net *get_net_ns_by_fd(int fd)
 {
-	struct proc_ns *ei;
 	struct file *file;
 	struct ns_common *ns;
 	struct net *net;
@@ -346,8 +345,7 @@ struct net *get_net_ns_by_fd(int fd)
 	if (IS_ERR(file))
 		return ERR_CAST(file);
 
-	ei = get_proc_ns(file_inode(file));
-	ns = ei->ns;
+	ns = get_proc_ns(file_inode(file));
 	if (ns->ops == &netns_operations)
 		net = get_net(container_of(ns, struct net, ns));
 	else