Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=26fb1589cb0aaec3a0b4418c54f30c1a2b1781f6
Commit: 26fb1589cb0aaec3a0b4418c54f30c1a2b1781f6
Parent: a4b0672db3a698d0684ee6e54f44e2e162a3da1b
Author: Jeff Moyer <[EMAIL PROTECTED]>
AuthorDate: Tue Oct 16 01:24:49 2007 -0700
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Tue Oct 16 09:42:54 2007 -0700
fix the max path calculation in radix-tree.c
A while back, Nick Piggin introduced a patch to reduce the node memory
usage for small files (commit cfd9b7df4abd3257c9e381b0e445817b26a51c0c):
-#define RADIX_TREE_MAP_SHIFT 6
+#define RADIX_TREE_MAP_SHIFT (CONFIG_BASE_SMALL ? 4 : 6)
Unfortunately, he didn't take into account the fact that the
calculation of the maximum path was based on an assumption of having
to round up:
#define RADIX_TREE_MAX_PATH (RADIX_TREE_INDEX_BITS/RADIX_TREE_MAP_SHIFT + 2)
So, if CONFIG_BASE_SMALL is set, you will end up with a
RADIX_TREE_MAX_PATH that is one greater than necessary. The practical
upshot of this is just a bit of wasted memory (one long in the
height_to_maxindex array, an extra pre-allocated radix tree node per
cpu, and extra stack usage in a couple of functions), but it seems
worth getting right.
It's also worth noting that I never build with CONFIG_BASE_SMALL.
What I did to test this was duplicate the code in a small user-space
program and check the results of the calculations for max path and the
contents of the height_to_maxindex array.
Signed-off-by: Jeff Moyer <[EMAIL PROTECTED]>
Acked-by: Nick Piggin <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
lib/radix-tree.c | 21 +++++++++++++++++----
1 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 0eee402..519d3f0 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -60,9 +60,14 @@ struct radix_tree_path {
};
#define RADIX_TREE_INDEX_BITS (8 /* CHAR_BIT */ * sizeof(unsigned long))
-#define RADIX_TREE_MAX_PATH (RADIX_TREE_INDEX_BITS/RADIX_TREE_MAP_SHIFT + 2)
+#define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
+ RADIX_TREE_MAP_SHIFT))
-static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH] __read_mostly;
+/*
+ * The height_to_maxindex array needs to be one deeper than the maximum
+ * path as height 0 holds only 1 entry.
+ */
+static unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1] __read_mostly;
/*
* Radix tree node cache.
@@ -492,7 +497,11 @@ EXPORT_SYMBOL(radix_tree_tag_set);
void *radix_tree_tag_clear(struct radix_tree_root *root,
unsigned long index, unsigned int tag)
{
- struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
+ /*
+ * The radix tree path needs to be one longer than the maximum path
+ * since the "list" is null terminated.
+ */
+ struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
struct radix_tree_node *slot = NULL;
unsigned int height, shift;
@@ -934,7 +943,11 @@ static inline void radix_tree_shrink(struct
radix_tree_root *root)
*/
void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
{
- struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
+ /*
+ * The radix tree path needs to be one longer than the maximum path
+ * since the "list" is null terminated.
+ */
+ struct radix_tree_path path[RADIX_TREE_MAX_PATH + 1], *pathp = path;
struct radix_tree_node *slot = NULL;
struct radix_tree_node *to_free;
unsigned int height, shift;
-
To unsubscribe from this list: send the line "unsubscribe git-commits-head" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
