fix some typos

Signed-off-by: Christoph Anton Mitterer <mail@christoph.anton.mitterer.name>
change "… / …" style to "…/…"

Signed-off-by: Christoph Anton Mitterer <mail@christoph.anton.mitterer.name>
use PAGE_SIZE instead of 4 KiB

Signed-off-by: Christoph Anton Mitterer <mail@christoph.anton.mitterer.name>
don't use words that Neil doesn't know ;-)

Signed-off-by: Christoph Anton Mitterer <mail@christoph.anton.mitterer.name>
chunks aren't relevant in the mirroring

Signed-off-by: Christoph Anton Mitterer <mail@christoph.anton.mitterer.name>