linux-kernel - Re: [PATCH] nfsd: try nfsdcld client tracker in containers

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Message-ID: <20130301080911.2a1a28a2@corrin.poochiereds.net>
Date:	Fri, 1 Mar 2013 08:09:11 -0500
From:	Jeff Layton <jlayton@...hat.com>
To:	Stanislav Kinsbursky <skinsbursky@...allels.com>
Cc:	bfields@...ldses.org, linux-nfs@...r.kernel.org, devel@...nvz.org,
	Trond.Myklebust@...app.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nfsd: try nfsdcld client tracker in containers

On Fri, 01 Mar 2013 11:24:23 +0300
Stanislav Kinsbursky <skinsbursky@...allels.com> wrote:

> Currently, UMH and Legacy trackers are disabled in containers.
> But existent logic can lookup nfs4_recoverydir in a container, and in this
> case will try to init Legacy tracker and skip nfsdcld client tracker.
> This actually means, that no client tracker will be started in a container at
> all, because Legacy tracker init will return -EINVAL for a container.
> So, let's change "-EINVAL" on "-ENOTSUPP" for legacy tracker init call in a
> container and in case of this error code, try nfsdcld client tracker instead
> of returning a error.
> 
> Signed-off-by: Stanislav Kinsbursky <skinsbursky@...allels.com>
> ---
>  fs/nfsd/nfs4recover.c |   12 ++++++++----
>  1 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
> index e0ae1cf..8aa069a 100644
> --- a/fs/nfsd/nfs4recover.c
> +++ b/fs/nfsd/nfs4recover.c
> @@ -524,7 +524,7 @@ nfsd4_legacy_tracking_init(struct net *net)
>  	if (net != &init_net) {
>  		WARN(1, KERN_ERR "NFSD: attempt to initialize legacy client "
>  			"tracking in a container!\n");
> -		return -EINVAL;
> +		return -ENOTSUPP;
>  	}
>  
>  	status = nfs4_legacy_state_init(net);
> @@ -1285,14 +1285,17 @@ nfsd4_client_tracking_init(struct net *net)
>  	/*
>  	 * See if the recoverydir exists and is a directory. If it is,
>  	 * then use the legacy ops.
> +	 * If legacy ops init return -ENOSUPP, then we are in a container and
> +	 * should try nfsdcld client tracking.
>  	 */
>  	nn->client_tracking_ops = &nfsd4_legacy_tracking_ops;
>  	status = kern_path(nfs4_recoverydir(), LOOKUP_FOLLOW, &path);
>  	if (!status) {
> -		status = S_ISDIR(path.dentry->d_inode->i_mode);
> +		if (S_ISDIR(path.dentry->d_inode->i_mode))
> +			status = nn->client_tracking_ops->init(net);
>  		path_put(&path);
> -		if (status)
> -			goto do_init;
> +		if (status != -ENOTSUPP)
> +			goto do_exit;
>  	}
>  
>  	/* Finally, try to use nfsdcld */
> @@ -1302,6 +1305,7 @@ nfsd4_client_tracking_init(struct net *net)
>  			"nfsdcltrack.\n");
>  do_init:
>  	status = nn->client_tracking_ops->init(net);
> +do_exit:
>  	if (status) {
>  		printk(KERN_WARNING "NFSD: Unable to initialize client "
>  				    "recovery tracking! (%d)\n", status);
> 

Seems OK as a stopgap fix. We're removing nfsdcld in 3.10 though so
this won't help prospective users of nfsd in a container for
long...particularly since our expectation is that no one has actually
ever deployed nfsdcld.

This is something that really needs to be fixed the right way since a
NFS server that doesn't allow clients to reclaim state after a reboot is
potentially dangerous...

I'm afraid I haven't been following along as closely as I should have
been. What's the rationale for disabling the UMH upcall? Is there no
way to make it so that new processes it spawns are done within the
correct container?

-- 
Jeff Layton <jlayton@...hat.com>
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