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 <khlebnikov@openvz.org>
Reported-and-bisected-by: Hans de Bruin <jmdebruin@xmsnet.nl>
Reported-and-bisected-by: Ondrej Zary <linux@rainbow-software.org>
Reported-bisected-and-tested-by: Toralf Förster <toralf.foerster@gmx.de>
Link: https://lkml.org/lkml/2012/6/5/64
Cc: stable <stable@vger.kernel.org> # 3.4.x
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index d7c878cc006c..e7964296fd50 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -686,6 +686,9 @@ void **radix_tree_next_chunk(struct radix_tree_root *root,
          * during iterating; it can be zero only at the beginning.
          * And we cannot overflow iter->next_index in a single step,
          * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
+         *
+         * This condition also used by radix_tree_next_slot() to stop
+         * contiguous iterating, and forbid swithing to the next chunk.
          */
         index = iter->next_index;
         if (!index && iter->index)