From ed9f524ac79457f0c547c85746b19b92526be612 Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Thu, 16 Sep 2010 01:30:19 +0900 Subject: [PATCH] ida: document IDA_BITMAP_LONGS calculation IDA_BITMAP_LONGS value is calculated take into account struct ida_bitmap not to waste memory space. Comment it. Signed-off-by: Namhyung Kim Acked-by: Tejun Heo Acked-by: Randy Dunlap Signed-off-by: Jiri Kosina --- include/linux/idr.h | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/include/linux/idr.h b/include/linux/idr.h index e968db71e33..88607523e2d 100644 --- a/include/linux/idr.h +++ b/include/linux/idr.h @@ -117,10 +117,13 @@ void idr_init(struct idr *idp); /* * IDA - IDR based id allocator, use when translation from id to * pointer isn't necessary. + * + * IDA_BITMAP_LONGS is calculated to be one less to accommodate + * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes. */ #define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */ -#define IDA_BITMAP_LONGS (128 / sizeof(long) - 1) -#define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8) +#define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1) +#define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8) struct ida_bitmap { long nr_busy; -- 2.39.3