linux-kernel - [PATCH 1/3] radix_tree: clean away saw_unset

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Date:	Tue, 19 Jul 2011 15:52:52 -0700 (PDT)
From:	Hugh Dickins <hughd@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 1/3] radix_tree: clean away saw_unset_tag leftovers

radix_tree_tag_get()'s BUG (when it sees a tag after saw_unset_tag) was
unsafe and removed in 2.6.34, but the pointless saw_unset_tag left behind.

Remove it now, and return 0 as soon as we see unset tag - we already rely
upon the root tag to be correct, returning 0 immediately if it's not set.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
 lib/radix-tree.c |   10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

--- mmotm.orig/lib/radix-tree.c	2011-07-08 18:57:14.810702665 -0700
+++ mmotm/lib/radix-tree.c	2011-07-19 11:11:21.285234139 -0700
@@ -576,7 +576,6 @@ int radix_tree_tag_get(struct radix_tree
 {
 	unsigned int height, shift;
 	struct radix_tree_node *node;
-	int saw_unset_tag = 0;
 
 	/* check the root's tag bit */
 	if (!root_tag_get(root, tag))
@@ -603,15 +602,10 @@ int radix_tree_tag_get(struct radix_tree
 			return 0;
 
 		offset = (index >> shift) & RADIX_TREE_MAP_MASK;
-
-		/*
-		 * This is just a debug check.  Later, we can bale as soon as
-		 * we see an unset tag.
-		 */
 		if (!tag_get(node, tag, offset))
-			saw_unset_tag = 1;
+			return 0;
 		if (height == 1)
-			return !!tag_get(node, tag, offset);
+			return 1;
 		node = rcu_dereference_raw(node->slots[offset]);
 		shift -= RADIX_TREE_MAP_SHIFT;
 		height--;
--
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