Made several updates on the dm-cache code. The major ones include,
* The change on handling of reads: cache insertions are now performed
in background for read bio requests, so the reads would appear faster.
* The feature of persistent metadata: cache metadata is automatically
dumped onto cache disk before a cache is removed, and it can be loaded
again when creating a cache so that the existing data on the cache
disk can be reused.
* The handling of status ioctl is also added, so on dmsetup status,
the cache outputs the cache stats, and on dmsetup table, it outputs
the cache configuration.
Signed-off-by: Ming Zhao <[email protected]>