Messages in this thread Patch in this message | | | From | Namhyung Kim <> | Subject | Re: [PATCH] ida: fix up bitmap size calculation | Date | Fri, 03 Sep 2010 03:07:16 +0900 |
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Namhyung Kim <namhyung@gmail.com> writes: > Got it. :-) I'll prepare new patch with that comment, then. > Thank you for the explanation.
How about this?
From 38866b19cdbf03d133c54a1f3b7d48279bdd4177 Mon Sep 17 00:00:00 2001 From: Namhyung Kim <namhyung@gmail.com> Date: Fri, 3 Sep 2010 02:44:47 +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 <namhyung@gmail.com> --- include/linux/idr.h | 9 ++++++++- 1 files changed, 8 insertions(+), 1 deletions(-)
diff --git a/include/linux/idr.h b/include/linux/idr.h index e968db7..7807e4b 100644 --- a/include/linux/idr.h +++ b/include/linux/idr.h @@ -119,9 +119,16 @@ void idr_init(struct idr *idp); * pointer isn't necessary. */ #define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */ +/* + * -1 is needed here to fit total chunk size into 128 bytes because + * struct ida_bitmap consists of nr_busy and bitmap. Since it is + * allocated by kmalloc(), chunk size should be matched with kmalloc + * size so that it will not waste memory. + */ #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) +/* IDA bitmap chunk */ struct ida_bitmap { long nr_busy; unsigned long bitmap[IDA_BITMAP_LONGS]; -- 1.7.2.2
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