- in cache_check, h must be non-NULL as it has been de-referenced,
  so don't bother checking for NULL.

- When a cache-item is updated, we need to call cache_revisit_request to see
  if there is a pending request waiting for that item.  We were using
  a transition to CACHE_VALID to see if that was needed, however that is
  wrong as an expired entry will still be marked 'valid' (as the data is valid
  and will need to be released).  So instead use an off transition for
  CACHE_PENDING which is exactly the right thing to test.

- Add a little bit more debugging info.
Signed-off-by: NNeil Brown <neilb@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>