Re: NFS client broken in Linus' tip

Russell King - ARM Linux
2014-02-03T20:25:37Z

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@infradead.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?

--
FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation
in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad.
Estimate before purchase was "up to 13.2Mbit".