Re: [Qemu-devel] [PATCH] bitmap: Update count after a merge

[Vladimir Sementsov-Ogievskiy]

27.09.2018 06:11, Eric Blake wrote:
> We need an accurate count of the number of bits set in a bitmap
> after a merge. In particular, since the merge operation short-circuits
> a merge from an empty source, if you have bitmaps A, B, and C where
> B started empty, then merge C into B, and B into A, an inaccurate
> count meant that A did not get the contents of C.
>
> Fixes: be58721db
> CC: address@hidden
> Signed-off-by: Eric Blake <address@hidden>


Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>

> ---
>
> Probably worth some testsuite coverage, but for a late-night one-liner,
> this is as much as I can do today.
>
>   util/hbitmap.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/util/hbitmap.c b/util/hbitmap.c
> index bcd304041aa..52e12da4b48 100644
> --- a/util/hbitmap.c
> +++ b/util/hbitmap.c
> @@ -753,3 +753,4 @@ bool hbitmap_merge(HBitmap *a, const HBitmap *b)
>               a->levels[i][j] |= b->levels[i][j];
>           }
>       }
> +    a->count = hb_count_between(a, 0, a->size - 1);
>
>       return true;
>   }


--
Best regards,
Vladimir