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

## Advertising

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