From: Frank Filz <ffilzlnx@us.ibm.com>
Subject: Re: Problems with fh_fsid_type=3 exports (device minor id >
	255)
Date: Wed, 31 May 2006 16:15:33 -0700
Message-ID: <1149117333.12795.53.camel@dyn9047022153>
References: <1148669319.12795.44.camel@dyn9047022153>
	 <1149115719.12795.49.camel@dyn9047022153>
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Cc: Neil Brown <neilb@suse.de>,
	Trond Myklebust <trond.myklebust@fys.uio.no>
To: NFS List <nfs@lists.sourceforge.net>
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On Wed, 2006-05-31 at 15:48 -0700, Frank Filz wrote:
> On Fri, 2006-05-26 at 11:48 -0700, Frank Filz wrote:
> > I having a problem with the 2.6.9 kernel and mounting file systems with
> > a minor device id > 255 where the mount fails. It seems like the file
> > handle is never cached. We are able to proceed if fsid is specified
> > in /etc/exports. nfs-utils version is 1.0.6.
> > 
> > Have others seen this problem and is there a fix in a later kernel?
> > 
> > I've been trying to follow the fh_compose and fh_verify code to
> > understand this, but I don't see where there's a difference between type
> > 3 file handles and type 1 file handles (fsid specified in /etc/exports)
> > that could cause a problem. When I add a little bit of debug messages, I
> > see that expkey_parse is being called as a result of a system call for
> > the type 1 handles, but not for the type 3 handles.
> 
> I've trudged my way through the code, and I think I've found the
> problem. The problem seems to be the way the kernel and nfs-utils expect
> the fsid to be coded. The kernel uses this code to encode:
> 
> 	unsigned major = MAJOR(dev);
> 	unsigned minor = MINOR(dev);
> 	return (minor & 0xff) | (major << 8) | ((minor & ~0xff) << 12);
> 
> The user space uses this code to decode:
> 
> 		memcpy(&dev, fsid, 4);
> 		memcpy(&inode, fsid+4, 4);
> 		major = (dev & 0xfff00) >> 8;
> 		minor = (dev & 0xff) | ((dev >> 12) & 0xfff00);

Oops, I'm horribly confused... The above code actually is right, well
mostly, I think it actually should be:

> 		major = (dev & 0xff00) >> 8;
> 		minor = (dev & 0xff) | ((dev >> 12) & 0xfff00);

The bug I'm chasing is because the install is using nfs-utils 1.0.6
which does not handle type 3 file handles at all.

Frank


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