Re: [PATCH vfs/for-next v2] cgroup: fix top cgroup refcnt leak

[Andrei Vagin <avagin@gmail.com>]

Alexander and David,

This patch fixed the problem which was reported more than a mounth ago
https://patchwork.kernel.org/patch/10610671/

Now this code is in the linux-next and the problem blocks running CRIU
tests on the linux next kernels:

https://travis-ci.org/avagin/linux/builds

Thanks,
Andrei

On Fri, Dec 28, 2018 at 04:04:00PM -0800, Andrei Vagin wrote:
> It looks like the c6b3d5bcd67c ("cgroup: fix top cgroup refcnt leak")
> commit was reverted by mistake.
> 
> $ mkdir /tmp/cgroup
> $ mkdir /tmp/cgroup2
> $ mount -t cgroup -o none,name=test test /tmp/cgroup
> $ mount -t cgroup -o none,name=test test /tmp/cgroup2
> $ umount /tmp/cgroup
> $ umount /tmp/cgroup2
> $ cat /proc/self/cgroup | grep test
> 12:name=test:/
> 
> You can see the test cgroup was not freed.
> 
> Cc: Li Zefan <lizefan@huawei.com>
> Fixes: aea3f2676c83 ("kernfs, sysfs, cgroup, intel_rdt: Support fs_context")
> Signed-off-by: Andrei Vagin <avagin@gmail.com>
> ---
> 
> v2: clean up code and add the vfs/for-next tag
> 
>  kernel/cgroup/cgroup.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
> index fb0717696895..f63974a3725f 100644
> --- a/kernel/cgroup/cgroup.c
> +++ b/kernel/cgroup/cgroup.c
> @@ -2047,6 +2047,9 @@ int cgroup_do_get_tree(struct fs_context *fc)
>  	ret = 0;
>  	if (ctx->kfc.new_sb_created)
>  		goto out_cgrp;
> +	else
> +		cgroup_put(&ctx->root->cgrp);
> +
>  	apply_cgroup_root_flags(ctx->flags);
>  	return 0;
>  
> -- 
> 2.17.2
>