radix-tree: fix contiguous iterator

radix-tree: fix contiguous iterator

This patch fixes bug in macro radix_tree_for_each_contig().

If radix_tree_next_slot() sees NULL in next slot it returns NULL, but following
radix_tree_next_chunk() switches iterating into next chunk. As result iterating
becomes non-contiguous and breaks vfs "splice" and all its users.

Signed-off-by: Konstantin Khlebnikov <[email protected]>
Reported-and-bisected-by: Hans de Bruin <[email protected]>
Reported-and-bisected-by: Ondrej Zary <[email protected]>
Reported-bisected-and-tested-by: Toralf Förster <[email protected]>
Link: https://lkml.org/lkml/2012/6/5/64
Cc: stable <[email protected]> # 3.4.x
Signed-off-by: Linus Torvalds <[email protected]>