[PATCH] cgroups: handle failure of cgroup_populate_dir() at mount/remount

[Li Zefan <lizf@cn.fujitsu.com>]

Now we have 'stat' file in both memory and cpuacct subsystems. If we
mount these 2 subsystems with option 'noprefix', the creation of 'stat'
file for cpuacct will fail, but without any notificatin to the user.

With this patch, we fail the mount/remount in this case.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
 kernel/cgroup.c |   18 ++++++++++++++++--
 1 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a7267bf..eab83f7 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -896,6 +896,7 @@ static int parse_cgroupfs_options(char *data,
 static int cgroup_remount(struct super_block *sb, int *flags, char *data)
 {
 	int ret = 0;
+	unsigned long subsys_bits;
 	struct cgroupfs_root *root = sb->s_fs_info;
 	struct cgroup *cgrp = &root->top_cgroup;
 	struct cgroup_sb_opts opts;
@@ -914,12 +915,17 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
 		goto out_unlock;
 	}
 
+	subsys_bits = root->subsys_bits;
 	ret = rebind_subsystems(root, opts.subsys_bits);
 	if (ret)
 		goto out_unlock;
 
 	/* (re)populate subsystem files */
-	cgroup_populate_dir(cgrp);
+	ret = cgroup_populate_dir(cgrp);
+	if (ret) {
+		rebind_subsystems(root, subsys_bits);
+		goto out_unlock;
+	}
 
 	if (opts.release_agent)
 		strcpy(root->release_agent_path, opts.release_agent);
@@ -1122,9 +1128,13 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
 		BUG_ON(!list_empty(&root_cgrp->children));
 		BUG_ON(root->number_of_cgroups != 1);
 
-		cgroup_populate_dir(root_cgrp);
+		ret = cgroup_populate_dir(root_cgrp);
+
 		mutex_unlock(&inode->i_mutex);
 		mutex_unlock(&cgroup_mutex);
+
+		if (ret)
+			goto drop_new_super;
 	}
 
 	simple_set_mnt(mnt, sb);
@@ -1803,6 +1813,10 @@ int cgroup_add_file(struct cgroup *cgrp,
 		dput(dentry);
 	} else
 		error = PTR_ERR(dentry);
+
+	if (error)
+		printk(KERN_WARNING "cgroup: Failed to create file '%s': %d\n",
+		       name, error);
 	return error;
 }
 
-- 
1.5.4.rc3