Bcache: Caching beyond just RAM

Checksumming won't save you here - what's it supposed to compared the checksum against? If you fill up your cache, turn of caching, write some data, and then turn caching back on without telling bcache about it... well, computers can't always save you from rm -rf either.

I am looking into invalidating the cache contents if a filesystem was already opened read write, or perhaps checking if the first page or so matches what it previously had - this would catch it provided the filesystem superblock changed. But the real performance gains are to be had with write behind caching, and none of this really matters there, since the cached device is now inconsistent if you use it without the cache. By the time bcache saw the cache was out of date it'd be too late to do anything.