Use readpage, not read for fastpath access
Modify the fast path case so that it uses readpage(), rather than read()
to access data in the cache. This removes a lot of the hidden, uncessary
work that the kernel was doing behind the scenes, and takes advantage of
the fact that we know a page read will always result in a page read
against the backing cache.
Reviewed-on: http://gerrit.openafs.org/535
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>