linux-kernel - [PATCH 6/8] radix_tree: Loop based on shift count, not height

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Date:	Tue, 19 Jan 2016 09:25:31 -0500
From:	Matthew Wilcox <matthew.r.wilcox@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>
Cc:	Matthew Wilcox <willy@...ux.intel.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCH 6/8] radix_tree: Loop based on shift count, not height

From: Matthew Wilcox <willy@...ux.intel.com>

When we introduce entries that can cover multiple indices, we will need
to stop in __radix_tree_create based on the shift, not the height.  Split
out for ease of bisect.

Signed-off-by: Matthew Wilcox <willy@...ux.intel.com>
---
 lib/radix-tree.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 422a92a..869be33 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -407,10 +407,10 @@ int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
 	slot = indirect_to_ptr(root->rnode);
 
 	height = root->height;
-	shift = (height-1) * RADIX_TREE_MAP_SHIFT;
+	shift = height * RADIX_TREE_MAP_SHIFT;
 
 	offset = 0;			/* uninitialised var warning */
-	while (height > 0) {
+	while (shift > 0) {
 		if (slot == NULL) {
 			/* Have to add a child node.  */
 			slot = radix_tree_node_alloc(root);
@@ -429,11 +429,11 @@ int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
 		}
 
 		/* Go a level down */
+		shift -= RADIX_TREE_MAP_SHIFT;
 		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
 		node = slot;
 		slot = node->slots[offset];
 		slot = indirect_to_ptr(slot);
-		shift -= RADIX_TREE_MAP_SHIFT;
 		height--;
 	}
 
-- 
2.7.0.rc3