linux-kernel - Re: [PATCH 7/8] cgroup: mount cgroupns-root when inside non-init cgroupns

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Message-ID: <20151207153911.GF9175@mtj.duckdns.org>
Date:	Mon, 7 Dec 2015 10:39:11 -0500
From:	Tejun Heo <tj@...nel.org>
To:	"Serge E. Hallyn" <serge.hallyn@...ntu.com>
Cc:	serge@...lyn.com, linux-kernel@...r.kernel.org,
	adityakali@...gle.com, linux-api@...r.kernel.org,
	containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
	lxc-devel@...ts.linuxcontainers.org, akpm@...ux-foundation.org,
	ebiederm@...ssion.com
Subject: Re: [PATCH 7/8] cgroup: mount cgroupns-root when inside non-init
 cgroupns

Hello, Serge.

On Thu, Dec 03, 2015 at 04:47:06PM -0600, Serge E. Hallyn wrote:
...
> +	dentry = dget(sb->s_root);
> +	if (!kn->parent) // this is the root
> +		return dentry;
> +
> +	knparent = find_kn_ancestor_below(kn, NULL);
> +	BUG_ON(!knparent);

Doing WARN_ON() and returning failure is better, I think.  Failing ns
mount is an okay failure mode and a lot better than crashing the
system.  Also, how about find_next_ancestor() for the name of the
function?

> +	do {
> +		struct dentry *dtmp;
> +		struct kernfs_node *kntmp;
> +
> +		if (kn == knparent)
> +			return dentry;
> +		kntmp = find_kn_ancestor_below(kn, knparent);
> +		BUG_ON(!kntmp);
> +		dtmp = lookup_one_len(kntmp->name, dentry, strlen(kntmp->name));
> +		dput(dentry);
> +		if (IS_ERR(dtmp))
> +			return dtmp;
> +		knparent = kntmp;
> +		dentry = dtmp;
> +	} while (1);

Other than the nitpicks, looks good to me.

Thanks.

-- 
tejun
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