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

[John Snow]

On 09/26/2018 11:11 PM, 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>
> ---
> 
> 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;
>  }
> 

OK, tests coming up. Thanks for the CC to stable.

--js