fs exporting code and introduces a Linux-wide struct fid.

SGI-PV: 970336
SGI-Modid: xfs-linux-melb:xfs-kern:29651a

Signed-off-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
Signed-off-by: Tim Shimmin <tes@sgi.com>
ÊP*b”