1 files changed, 92 insertions, 3 deletions

diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 776137828dc..281c0c9bc39 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -35,7 +35,7 @@ static const struct super_operations sysfs_ops = {
 struct sysfs_dirent sysfs_root = {
 	.s_name		= "",
 	.s_count	= ATOMIC_INIT(1),
-	.s_flags	= SYSFS_DIR,
+	.s_flags	= SYSFS_DIR | (KOBJ_NS_TYPE_NONE << SYSFS_NS_TYPE_SHIFT),
 	.s_mode		= S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 	.s_ino		= 1,
 };
@@ -72,18 +72,107 @@ static int sysfs_fill_super(struct super_block *sb, void *data, int silent)
 	return 0;
 }
 
+static int sysfs_test_super(struct super_block *sb, void *data)
+{
+	struct sysfs_super_info *sb_info = sysfs_info(sb);
+	struct sysfs_super_info *info = data;
+	enum kobj_ns_type type;
+	int found = 1;
+
+	for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++) {
+		if (sb_info->ns[type] != info->ns[type])
+			found = 0;
+	}
+	return found;
+}
+
+static int sysfs_set_super(struct super_block *sb, void *data)
+{
+	int error;
+	error = set_anon_super(sb, data);
+	if (!error)
+		sb->s_fs_info = data;
+	return error;
+}
+
 static int sysfs_get_sb(struct file_system_type *fs_type,
 	int flags, const char *dev_name, void *data, struct vfsmount *mnt)
 {
-	return get_sb_single(fs_type, flags, data, sysfs_fill_super, mnt);
+	struct sysfs_super_info *info;
+	enum kobj_ns_type type;
+	struct super_block *sb;
+	int error;
+
+	error = -ENOMEM;
+	info = kzalloc(sizeof(*info), GFP_KERNEL);
+	if (!info)
+		goto out;
+
+	for (type = KOBJ_NS_TYPE_NONE; type < KOBJ_NS_TYPES; type++)
+		info->ns[type] = kobj_ns_current(type);
+
+	sb = sget(fs_type, sysfs_test_super, sysfs_set_super, info);
+	if (IS_ERR(sb) || sb->s_fs_info != info)
+		kfree(info);
+	if (IS_ERR(sb)) {
+		error = PTR_ERR(sb);
+		goto out;
+	}
+	if (!sb->s_root) {
+		sb->s_flags = flags;
+		error = sysfs_fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
+		if (error) {
+			deactivate_locked_super(sb);
+			goto out;
+		}
+		sb->s_flags |= MS_ACTIVE;
+	}
+
+	simple_set_mnt(mnt, sb);
+	error = 0;
+out:
+	return error;
+}
+
+static void sysfs_kill_sb(struct super_block *sb)
+{
+	struct sysfs_super_info *info = sysfs_info(sb);
+
+	/* Remove the superblock from fs_supers/s_instances
+	 * so we can't find it, before freeing sysfs_super_info.
+	 */
+	kill_anon_super(sb);
+	kfree(info);
 }
 
 static struct file_system_type sysfs_fs_type = {
 	.name		= "sysfs",
 	.get_sb		= sysfs_get_sb,
-	.kill_sb	= kill_anon_super,
+	.kill_sb	= sysfs_kill_sb,
 };
 
+void sysfs_exit_ns(enum kobj_ns_type type, const void *ns)
+{
+	struct super_block *sb;
+
+	mutex_lock(&sysfs_mutex);
+	spin_lock(&sb_lock);
+	list_for_each_entry(sb, &sysfs_fs_type.fs_supers, s_instances) {
+		struct sysfs_super_info *info = sysfs_info(sb);
+		/*
+		 * If we see a superblock on the fs_supers/s_instances
+		 * list the unmount has not completed and sb->s_fs_info
+		 * points to a valid struct sysfs_super_info.
+		 */
+		/* Ignore superblocks with the wrong ns */
+		if (info->ns[type] != ns)
+			continue;
+		info->ns[type] = NULL;
+	}
+	spin_unlock(&sb_lock);
+	mutex_unlock(&sysfs_mutex);
+}
+
 int __init sysfs_init(void)
 {
 	int err = -ENOMEM;