Unfortunately Lemire's wyhash code was licensed as Apache, we'd rather
have something compatible with GPLv2. This probably a more appropriate
choice anyway.
Things not done because probably disruptive:
* kmod filesystem string
* sysctl/debugfs/trace
* metrics names
* xmon instance names
Some of these might be renamed too, but starting with a relatively
safe set.
Initial version really by Pawel, but many changes in between.
Big outstanding issues:
* span cache reclamation (unbounded memory otherwise...)
* bad block service detection and workarounds
* corrupted blocks detection and workaround
Co-authored-by: Paweł Dziepak <pawel.dziepak@xtxmarkets.com>
The main thing that's added is full RS support, but a lot of things
were rejigged along the way. The tests are still a bit lacking,
and will be augmented in future commits.
