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SubjectRe: NFSv3 support (bugs, some fixes, and more)
Quoting Jamie Lokier (lkd@tantalophile.demon.co.uk):
> Michael Kaminsky wrote:
> > RFC 1813 (NFSv3) says
> >
> > To the client, the file handle is opaque. The client stores file
> > handles for use in a later request and can compare two file
> > handles from the same server for equality by doing a
> > byte-by-byte comparison, but cannot otherwise interpret the
> > contents of file handles. If two file handles from the same
> > server are equal, they must refer to the same file, but if they
> > are not equal, no conclusions can be drawn. Servers should try
> > to maintain a one-to-one correspondence between file handles and
> > files, but this is not required. Clients should use file handle
> > comparisons only to improve performance, not for correct
> > behavior.
> >
> > From my reading of the above, if an NFS server returns a different
> > file handle for two files that are hard-linked (i.e., the same file
> > on the server), the client cannot assume that they are the same ("no
> > conclusions can be drawn"). So, in the hard link case, the server
> > should be returning the same handle (and the same fileid), right?
>
> My reading of it says: in the hard link case, the server MAY send the
> same handle.

The server certainly is not required to send back the same filehandle
for hardlinked files, but it should. Otherwise, the client (linux
kernel) cannot assume the files are the same according to the RFC
(which in reality they are). Currently, the kernel makes the
assumption they are the same implicitly, by only using fileid to lookup
inodes.

Michael

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