[PATCH 00/22] cache cursors: an introduction

[ This series is posted for review and comments. ]

The following patch series introduces an abstraction called a "cache cursor" that will eventually allow us to replace the current active_cache array with something else.

A cache cursor represents a position inside the cache. This position has a cache_entry associated with it, of course, but since the cache is ordered, a cache cursor also has the concept of next, previous, and end-of-cache.

With a cache cursor we can build a simple iterator mechanism that calls a particular function for every entry in the cache, in order. This allows us to hide further the specifics of the active cache implementation -- the function gets to see the cache cursor and an element, but does not have direct access to the cache and cannot assume it has a particular structure.

Currently the cache cursor type is just a structure with an integer in it, so it largely mimics the existing implementation.

This patch series is against the "proposed updates" branch, as of a couple of days ago. It has been tested via "make test" and I'm currently using it for my own work without issue.

Signed-off-by: Chuck Lever <cel@netapp.com>
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