linux-kernel - [PATCH 26/30] radix-tree: Fix radix_tree

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Date:	Wed,  6 Apr 2016 17:21:35 -0400
From:	Matthew Wilcox <willy@...ux.intel.com>
To:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Matthew Wilcox <willy@...ux.intel.com>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
	Konstantin Khlebnikov <koct9i@...il.com>,
	Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
	Jan Kara <jack@...e.com>, Neil Brown <neilb@...e.de>
Subject: [PATCH 26/30] 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@...ux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
---
 lib/radix-tree.c                      | 4 ++--
 tools/testing/radix-tree/multiorder.c | 5 +++++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index d894654b5ecc..4291f344cb95 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
diff --git a/tools/testing/radix-tree/multiorder.c b/tools/testing/radix-tree/multiorder.c
index de3d0e96f987..0229e6fb590f 100644
--- a/tools/testing/radix-tree/multiorder.c
+++ b/tools/testing/radix-tree/multiorder.c
@@ -135,6 +135,11 @@ static void multiorder_check(unsigned long index, int order)
 		item_check_absent(&tree, i);
 	for (i = max; i < 2*max; i++)
 		item_check_absent(&tree, i);
+	for (i = min; i < max; i++) {
+		static void *entry = (void *)
+					(0xA0 | RADIX_TREE_EXCEPTIONAL_ENTRY);
+		assert(radix_tree_insert(&tree, i, entry) == -EEXIST);
+	}
 
 	assert(item_delete(&tree, index) != 0);
 
-- 
2.8.0.rc3