linux-kernel - Re: NFS client broken in Linus' tip

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Message-ID: <20140203202521.GM26684@n2100.arm.linux.org.uk>
Date:	Mon, 3 Feb 2014 20:25:21 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Trond Myklebust <trond.myklebust@...marydata.com>
Cc:	Christoph Hellwig <hch@...radead.org>,
	linuxnfs <linux-nfs@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Viro Alexander <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@....de>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: NFS client broken in Linus' tip

On Mon, Feb 03, 2014 at 03:22:15PM -0500, Trond Myklebust wrote:
> On Mon, 2014-02-03 at 10:45 -0500, Trond Myklebust wrote:
> > On Feb 3, 2014, at 9:57, Christoph Hellwig <hch@...radead.org> wrote:
> > 
> > > On Mon, Feb 03, 2014 at 09:17:30AM -0500, Trond Myklebust wrote:
> > >> As I said above, that causes posix_acl_xattr_get() to return the wrong answer (ENODATA instead of EOPNOTSUPP).
> > > 
> > > Is it really the wrong answer?  How does userspace care wether this
> > > server doesn't support ACLs at all or none is set?  The resulting
> > > behavior is the same.
> > 
> > It will certainly cause acl_get_file() to behave differently than previously. I’ve no idea how that will affect applications, though.
> > 
> > > If there's a good reason to care we might have to go with your patch,
> > > but if we can avoid it I'd prefer to keep things simple.
> > 
> > One alternative is to simply wrap posix_acl_xattr_get() in fs/nfs/nfs3acl.c, and have it check the value of nfs_server_capable(inode, NFS_CAP_ACLS) before returning ENODATA. That’s rather ugly too...
> 
> FWIW, here is the alternative patch. I've tested it, and it seems to
> work.

Thanks.

As there's now two fixes, which would you like me to test?

One comment on this patch though:

> +static int
> +nfs_posix_acl_xattr_get(struct dentry *dentry, const char *name,
> +		void *value, size_t size, int type)
> +{
> +	int ret;
> +
> +	ret = posix_acl_xattr_get(dentry, name, value, size, type);
> +	/*
> +	 * This check is needed to override the ENODATA error that
> +	 * posix_acl_xattr_get will return if the acl probe fails.
> +	 */
> +	if (!nfs_server_capable(dentry->d_inode, NFS_CAP_ACLS))
> +		ret = -EOPNOTSUPP;

I'm not familiar with this code, but the above looks slightly weird,
and a little suspicious - especially with the lack of blank line
before the comment.  Is the above actually intended?

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