FSTree file counter used by writecache. As writecache has now only one
storage, so it is required to use real object size to get writecache
size more accurate than `count * max_object_size`.
Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>
It is not a part of FSTree itself, but rather a way to solve concurrent
counter update on non-linux implementations. New linux implementations
is pretty simple: link fails when the file exists, unlink fails when the
file doesn't exist.
Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>
