releases/3.4.2/radix-tree-fix-contiguous-iterator.patch

   1 From fffaee365fded09f9ebf2db19066065fa54323c3 Mon Sep 17 00:00:00 2001
   2 From: Konstantin Khlebnikov <khlebnikov@openvz.org>
   3 Date: Tue, 5 Jun 2012 21:36:33 +0400
   4 Subject: radix-tree: fix contiguous iterator
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   8
   9 From: Konstantin Khlebnikov <khlebnikov@openvz.org>
  10
  11 commit fffaee365fded09f9ebf2db19066065fa54323c3 upstream.
  12
  13 This patch fixes bug in macro radix_tree_for_each_contig().
  14
  15 If radix_tree_next_slot() sees NULL in next slot it returns NULL, but following
  16 radix_tree_next_chunk() switches iterating into next chunk. As result iterating
  17 becomes non-contiguous and breaks vfs "splice" and all its users.
  18
  19 Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
  20 Reported-and-bisected-by: Hans de Bruin <jmdebruin@xmsnet.nl>
  21 Reported-and-bisected-by: Ondrej Zary <linux@rainbow-software.org>
  22 Reported-bisected-and-tested-by: Toralf Förster <toralf.foerster@gmx.de>
  23 Link: https://lkml.org/lkml/2012/6/5/64
  24 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  25 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  26
  27 ---
  28  include/linux/radix-tree.h |    5 ++++-
  29  lib/radix-tree.c           |    3 +++
  30  2 files changed, 7 insertions(+), 1 deletion(-)
  31
  32 --- a/include/linux/radix-tree.h
  33 +++ b/include/linux/radix-tree.h
  34 @@ -368,8 +368,11 @@ radix_tree_next_slot(void **slot, struct
  35                         iter->index++;
  36                         if (likely(*slot))
  37                                 return slot;
  38 -                       if (flags & RADIX_TREE_ITER_CONTIG)
  39 +                       if (flags & RADIX_TREE_ITER_CONTIG) {
  40 +                               /* forbid switching to the next chunk */
  41 +                               iter->next_index = 0;
  42                                 break;
  43 +                       }
  44                 }
  45         }
  46         return NULL;
  47 --- a/lib/radix-tree.c
  48 +++ b/lib/radix-tree.c
  49 @@ -673,6 +673,9 @@ void **radix_tree_next_chunk(struct radi
  50          * during iterating; it can be zero only at the beginning.
  51          * And we cannot overflow iter->next_index in a single step,
  52          * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
  53 +        *
  54 +        * This condition also used by radix_tree_next_slot() to stop
  55 +        * contiguous iterating, and forbid swithing to the next chunk.
  56          */
  57         index = iter->next_index;
  58         if (!index && iter->index)