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Commit c6b3d5bc authored by Li Zefan's avatar Li Zefan Committed by Tejun Heo
Browse files

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: default avatarLi Zefan <lizefan@huawei.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 4a4389ab

kernel/cgroup.c

+3 −2
Original line number Diff line number Diff line
@@ -1487,6 +1487,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
	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 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
	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;

}