[PATCH RESEND 1/2] ida: document IDA_BITMAP_LONGS calculation

From: Namhyung Kim
Date: Wed Sep 15 2010 - 08:46:17 EST


IDA_BITMAP_LONGS value is calculated take into account struct ida_bitmap
not to waste memory space. Comment it.

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxx>
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
---
include/linux/idr.h | 5 ++++-
1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/include/linux/idr.h b/include/linux/idr.h
index e968db7..3f4b718 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_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8)

struct ida_bitmap {
long nr_busy;
--
1.7.2.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/