Messages in this thread Patch in this message | | | Date | Sat, 27 May 2006 23:48:51 +0800 | From | Wu Fengguang <> | Subject | [PATCH 02/32] radixtree: introduce radix_tree_scan_hole[_backward]() |
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Introduce a pair of functions to scan radix tree for hole/empty item. - radix_tree_scan_hole(root, index, max_scan) - radix_tree_scan_hole_backward(root, index, max_scan)
The implementation is dumb and obviously correct. It will help to debug the smart ones to be introduced in future.
Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn> ---
include/linux/radix-tree.h | 4 ++ lib/radix-tree.c | 71 +++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 75 insertions(+)
--- linux-2.6.17-rc4-mm3.orig/include/linux/radix-tree.h +++ linux-2.6.17-rc4-mm3/include/linux/radix-tree.h @@ -55,6 +55,10 @@ void *radix_tree_delete(struct radix_tre unsigned int radix_tree_gang_lookup(struct radix_tree_root *root, void **results, unsigned long first_index, unsigned int max_items); +unsigned long radix_tree_scan_hole_backward(struct radix_tree_root *root, + unsigned long index, unsigned long max_scan); +unsigned long radix_tree_scan_hole(struct radix_tree_root *root, + unsigned long index, unsigned long max_scan); int radix_tree_preload(gfp_t gfp_mask); void radix_tree_init(void); void *radix_tree_tag_set(struct radix_tree_root *root, --- linux-2.6.17-rc4-mm3.orig/lib/radix-tree.c +++ linux-2.6.17-rc4-mm3/lib/radix-tree.c @@ -541,6 +541,77 @@ int radix_tree_tag_get(struct radix_tree EXPORT_SYMBOL(radix_tree_tag_get); #endif +static unsigned long radix_tree_scan_hole_dumb(struct radix_tree_root *root, + unsigned long index, unsigned long max_scan) +{ + unsigned long i; + + for (i = 0; i < max_scan; i++) { + if (!radix_tree_lookup(root, index + i)) + break; + if (index + i == ULONG_MAX) + break; + } + + return index + i; +} + +static unsigned long radix_tree_scan_hole_backward_dumb( + struct radix_tree_root *root, + unsigned long index, unsigned long max_scan) +{ + unsigned long i; + + for (i = 0; i < max_scan; i++) { + if (!radix_tree_lookup(root, index - i)) + break; + if (index - i == 0) + break; + } + + return index - i; +} + +/** + * radix_tree_scan_hole - scan for hole + * @root: radix tree root + * @index: index key + * @max_scan: advice on max items to scan (it may scan a little more) + * + * Scan forward from @index for a hole/empty item, stop when + * - hit hole + * - hit index ULONG_MAX + * - @max_scan or more items scanned + * + * One can be sure that (@returned_index >= @index). + */ +unsigned long radix_tree_scan_hole(struct radix_tree_root *root, + unsigned long index, unsigned long max_scan) +{ + return radix_tree_scan_hole_dumb(root, index, max_scan); +} +EXPORT_SYMBOL(radix_tree_scan_hole); + +/** + * radix_tree_scan_hole_backward - scan backward for hole + * @root: radix tree root + * @index: index key + * @max_scan: advice on max items to scan (it may scan a little more) + * + * Scan backward from @index for a hole/empty item, stop when + * - hit hole + * - hit index 0 + * - @max_scan or more items scanned + * + * One can be sure that (@returned_index <= @index). + */ +unsigned long radix_tree_scan_hole_backward(struct radix_tree_root *root, + unsigned long index, unsigned long max_scan) +{ + return radix_tree_scan_hole_backward_dumb(root, index, max_scan); +} +EXPORT_SYMBOL(radix_tree_scan_hole_backward); + static unsigned int __lookup(struct radix_tree_root *root, void **results, unsigned long index, unsigned int max_items, unsigned long *next_index) -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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