Commit c6b3d5bc authored Apr 04, 2014 by Li Zefan Committed by Tejun Heo Apr 04, 2014

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>

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 @@ out_unlock:
		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;
		}

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