cgroup: fix top cgroup refcnt leak
As mount() and kill_sb() is not a one-to-one match, If we mount the same
cgroupfs in serveral mount points, and then umount all of them, kill_sb()
will be called only once.
Try:
# mount -t cgroup -o cpuacct xxx /cgroup
# mount -t cgroup -o cpuacct xxx /cgroup2
# cat /proc/cgroups | grep cpuacct
cpuacct 2 1 1
# umount /cgroup
# umount /cgroup2
# cat /proc/cgroups | grep cpuacct
cpuacct 2 1 1
You'll see cgroupfs will never be freed.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index fede3d3..0dfc732 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1487,6 +1487,7 @@
struct cgroup_sb_opts opts;
struct dentry *dentry;
int ret;
+ bool new_sb;
/*
* The first time anyone tries to mount a cgroup, enable the list
@@ -1603,8 +1604,8 @@
if (ret)
return ERR_PTR(ret);
- dentry = kernfs_mount(fs_type, flags, root->kf_root, NULL);
- if (IS_ERR(dentry))
+ dentry = kernfs_mount(fs_type, flags, root->kf_root, &new_sb);
+ if (IS_ERR(dentry) || !new_sb)
cgroup_put(&root->cgrp);
return dentry;
}