The 4level mods have caused 2level swapoff to miss entries and hang.
There's probably a one-line fix for that, but the error is really caused
by previous awkwardness - each mask applied on two levels, an "address"
that's an offset plus an "offset" that's an address.  Simplify the four
levels to behave in the same address/next/end way and the bug vanishes.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>