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

From: Randy Dunlap
Date: Wed Sep 15 2010 - 11:22:33 EST


On Wed, 15 Sep 2010 21:46:01 +0900 Namhyung Kim wrote:

> 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)

Might as well do:

#define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1)

instead of repeating the 128.


> -#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;
> --


---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***
--
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/