[Devel] [PATCH 12/20] Make proc hav emultiple superblocks - one for each namespace

[xemul at openvz.org]

Each pid namespace have to be visible through its own proc mount.
Thus we need to have per-namespace proc trees with their own
superblocks.

Signed-off-by: Pavel Emelyanov <xemul at openvz.org>

---

 fs/proc/inode.c               |    2 -
 fs/proc/root.c                |   67 +++++++++++++++++++++++++++++++++++++++---
 include/linux/pid_namespace.h |    3 +
 include/linux/proc_fs.h       |    3 +
 4 files changed, 69 insertions(+), 6 deletions(-)

--- ./fs/proc/inode.c.ve12	2007-08-06 14:54:42.000000000 +0400
+++ ./fs/proc/inode.c	2007-08-06 14:58:51.000000000 +0400
@@ -427,7 +428,7 @@ out_mod:
 	return NULL;
 }			
 
-int proc_fill_super(struct super_block *s, void *data, int silent)
+int proc_fill_super(struct super_block *s)
 {
 	struct inode * root_inode;
 
--- ./fs/proc/root.c.ve12	2007-08-06 14:54:42.000000000 +0400
+++ ./fs/proc/root.c	2007-08-06 14:58:51.000000000 +0400
@@ -18,32 +18,90 @@
 #include <linux/bitops.h>
 #include <linux/smp_lock.h>
 #include <linux/mount.h>
+#include <linux/pid_namespace.h>
 
 #include "internal.h"
 
 struct proc_dir_entry *proc_net, *proc_net_stat, *proc_bus, *proc_root_fs, *proc_root_driver;
 
+static int proc_test_super(struct super_block *sb, void *data)
+{
+	return sb->s_fs_info == data;
+}
+
+static int proc_set_super(struct super_block *sb, void *data)
+{
+	struct pid_namespace *ns;
+
+	ns = (struct pid_namespace *)data;
+	sb->s_fs_info = get_pid_ns(ns);
+	return set_anon_super(sb, NULL);
+}
+
 static int proc_get_sb(struct file_system_type *fs_type,
 	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 {
+	int err;
+	struct super_block *sb;
+	struct pid_namespace *ns;
+	struct proc_inode *ei;
+
 	if (proc_mnt) {
 		/* Seed the root directory with a pid so it doesn't need
 		 * to be special in base.c.  I would do this earlier but
 		 * the only task alive when /proc is mounted the first time
 		 * is the init_task and it doesn't have any pids.
 		 */
-		struct proc_inode *ei;
 		ei = PROC_I(proc_mnt->mnt_sb->s_root->d_inode);
 		if (!ei->pid)
 			ei->pid = find_get_pid(1);
 	}
-	return get_sb_single(fs_type, flags, data, proc_fill_super, mnt);
+
+	if (flags & MS_KERNMOUNT)
+		ns = (struct pid_namespace *)data;
+	else
+		ns = current->nsproxy->pid_ns;
+
+	sb = sget(fs_type, proc_test_super, proc_set_super, ns);
+	if (IS_ERR(sb))
+		return PTR_ERR(sb);
+
+	if (!sb->s_root) {
+		sb->s_flags = flags;
+		err = proc_fill_super(sb);
+		if (err) {
+			up_write(&sb->s_umount);
+			deactivate_super(sb);
+			return err;
+		}
+
+		ei = PROC_I(sb->s_root->d_inode);
+		if (!ei->pid) {
+			rcu_read_lock();
+			ei->pid = get_pid(find_pid_ns(1, ns));
+			rcu_read_unlock();
+		}
+
+		sb->s_flags |= MS_ACTIVE;
+		ns->proc_mnt = mnt;
+	}
+
+	return simple_set_mnt(mnt, sb);
+}
+
+static void proc_kill_sb(struct super_block *sb)
+{
+	struct pid_namespace *ns;
+
+	ns = (struct pid_namespace *)sb->s_fs_info;
+	kill_anon_super(sb);
+	put_pid_ns(ns);
 }
 
 static struct file_system_type proc_fs_type = {
 	.name		= "proc",
 	.get_sb		= proc_get_sb,
-	.kill_sb	= kill_anon_super,
+	.kill_sb	= proc_kill_sb,
 };
 
 void __init proc_root_init(void)
@@ -54,12 +112,13 @@ void __init proc_root_init(void)
 	err = register_filesystem(&proc_fs_type);
 	if (err)
 		return;
-	proc_mnt = kern_mount(&proc_fs_type);
+	proc_mnt = kern_mount_data(&proc_fs_type, &init_pid_ns);
 	err = PTR_ERR(proc_mnt);
 	if (IS_ERR(proc_mnt)) {
 		unregister_filesystem(&proc_fs_type);
 		return;
 	}
+
 	proc_misc_init();
 	proc_net = proc_mkdir("net", NULL);
 	proc_net_stat = proc_mkdir("net/stat", NULL);
--- ./include/linux/pid_namespace.h.ve12	2007-08-06 14:58:51.000000000 +0400
+++ ./include/linux/pid_namespace.h	2007-08-06 14:59:02.000000000 +0400
@@ -23,6 +23,9 @@ struct pid_namespace {
 	struct kmem_cache *pid_cachep;
 	int level;
 	struct pid_namespace *parent;
+#ifdef CONFIG_PROC_FS
+	struct vfsmount *proc_mnt;
+#endif
 };
 
 extern struct pid_namespace init_pid_ns;
--- ./include/linux/proc_fs.h.ve12	2007-08-06 14:58:51.000000000 +0400
+++ ./include/linux/proc_fs.h	2007-08-06 14:58:51.000000000 +0400
@@ -126,7 +126,8 @@ extern struct proc_dir_entry *create_pro
 extern void remove_proc_entry(const char *name, struct proc_dir_entry *parent);
 
 extern struct vfsmount *proc_mnt;
-extern int proc_fill_super(struct super_block *,void *,int);
+struct pid_namespace;
+extern int proc_fill_super(struct super_block *);
 extern struct inode *proc_get_inode(struct super_block *, unsigned int, struct proc_dir_entry *);
 
 /*