radix-tree: fix radix_tree_create for sibling entries

If the radix tree user attempted to insert a colliding entry with an
existing multiorder entry, then radix_tree_create() could encounter a
sibling entry when walking down the tree to look for a slot.  Use
radix_tree_descend() to fix the problem, and add a test-case to make
sure the problem doesn't come back in future.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index b1ca74489bc2..9b5d8a963897 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -548,9 +548,9 @@ int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
                 /* Go a level down */
                 height--;
                 shift -= RADIX_TREE_MAP_SHIFT;
-                offset = (index >> shift) & RADIX_TREE_MAP_MASK;
                 node = indirect_to_ptr(slot);
-                slot = node->slots[offset];
+                offset = (index >> shift) & RADIX_TREE_MAP_MASK;
+                offset = radix_tree_descend(node, &slot, offset);
         }
 
 #ifdef CONFIG_RADIX_TREE_MULTIORDER