md bitmap-based asynchronous writes

These three patches provide the ability to perform asynchronous writes with raid1. The asynchronous write capability is primarily useful when raid1 is employed in network replication (i.e., with one or more of the disks located on a remote system). It allows us to acknowledge writes before they reach the remote system, thus making much more efficient use of the network.

The kernel patches build on the md bitmap code and the 117WriteMostly-update patch. The first patch provides the framework for async writes. The second implements async writes for raid1. The third patch (for mdadm) provides the write-mostly updates and the ability to configure raid1 arrays for async writes.

Thnaks,
Paul