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Subject[PATCH RESEND 1/2] ida: document IDA_BITMAP_LONGS calculation
Date
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@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
---
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


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