Hello,

Attached is a patch that enables NFS to use David Howells'
File System Caching implementation (FSCache). Also attached
are two supplemental patches that are need to fixed two oops that
were found during debugging (Note: these patches are also
in people.redhat.com/steved/cachefs/2.6.12-rc3-mm3/)

2.6.12-rc3-mm3-nfs-fscache.patch - David and I have
been working on this for sometime now and the code
seems to be pretty solid. One issue is Trond's dislike
of how the NFS code is dependent on FSCache calls. I did
looking to changing this, but its not clear (at least to
me) how we could make things better... But that's
something that will need to be addressed.

The second issue is what we've been calling "NFS aliasing".
The fact that two mounted NFS super blocks can point to
the same page causes major fits for FSC. David has
proposed some patches to resolve this issue that are still
under review. But at this point, to stop a BUG() popping,
when a second NFS filesystem is mounted, the
2.6.12-rc3-mm3-fscache-cookie-exist.patch is needed.

The final patch 2.6.12-rc3-mm3-cachefs-wb.patch is need
to stop another BUG() from popping during NFS reads.

NFS uses FSC on a per-mount bases which means a new
mount flag 'fsc' is need to activate the caching.
Example:
     mount -t nfs4 -o fsc server:/home /mnt/server/home

(Note: people.redhat.com/steved/cachefs/util-linux/ has the
util-linux binary and source rpms with the fsc support).

To set up a mounted cachefs partition, first initialize
the disk partition by:
    echo "cachefs___" >/dev/hdg9
then mount the partition:
     mount -t cachefs /dev/hdg9 /cache-hdg9

See Documentation/filesystems/caching in the kernel
source for more details.

I'm hopeful that you'll added these patches to your tree
so they will get some much needed testing. I'm also going
to be pushing to get the caching code into a Fedora Core
kernel, but due to the  dependency on David's new vm_ops,
page_mkwrite, this might take some time...
(Note: people.redhat.com/steved/cachefs/mmpatches has all of the
current mm patches)

Comments?

steved.