[RFC] Splitting CacheFS into general manager and cache backend bits

From: David Howells
Date: Tue Oct 05 2004 - 05:18:30 EST



I've whipped up a patch to split CacheFS into two:

(1) FS-Cache

This is a general cache manager that the interested netfs's talk to. It
is supplied with a number of cache backends over which it distributes the
operations from the netfs's.

(2) CacheFS

This is then made into a cache backend. The act of mounting a block
device as cachefs causes the space contained therein to be made available
through FS-Cache.

To give you a clearer idea of what I'm thinking, this diagram might help:

+---------+
| | +-----------+
| NFS |--+ | |
| | | +-->| CacheFS |
+---------+ | +----------+ | | /dev/hda5 |
| | | | +-----------+
+---------+ +-->| | |
| | | |--+ +-------------+
| AFS |----->| FS-Cache | | |
| | | |----->| Cache Files |
+---------+ +-->| | | /var/cache |
| | |--+ +-------------+
+---------+ | +----------+ |
| | | | +-------------+
| ISOFS |--+ | | |
| | +-->| ReiserCache |
+---------+ | / |
+-------------+

So, for example, you might have a block device mounted with CacheFS as one of
your backends, the traditional bunch of cache files as another backend and
some sort of Reiser4 plug-in as a third backend.

A netfs only has to be modified to take account of FS-Cache. It then shouldn't
need to be modified further to support each different type of cache.

David
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