On 08/07/2017 10:45 AM, Markus Armbruster wrote:
> Block dirty bitmaps represent granularity in bytes as uint32_t. It
> must be a power of two and a multiple of BDRV_SECTOR_SIZE.
>
> The trouble with uint32_t is computations like this one in
> mirror_do_read():
>
> uint64_t max_bytes;
>
> max_bytes = s->granularity * s->max_iov;
>
> The operands of * are uint32_t and int, so the product is computed in
> uint32_t (assuming 32 bit int), then zero-extended to uint64_t.
>
> Since granularity is generally combined with 64 bit file offsets, it's
> best to make it 64 bits, too. Less opportunity to screw up.
>
> Signed-off-by: Markus Armbruster <arm...@redhat.com>
[bweeooop]
> --- a/block/dirty-bitmap.c
> +++ b/block/dirty-bitmap.c
[buuuuweeeep]
> @@ -506,16 +506,11 @@ uint32_t
> bdrv_get_default_bitmap_granularity(BlockDriverState *bs)
> return granularity;
> }
>
> -uint32_t bdrv_dirty_bitmap_granularity(const BdrvDirtyBitmap *bitmap)
> +uint64_t bdrv_dirty_bitmap_granularity(const BdrvDirtyBitmap *bitmap)
> {
> return BDRV_SECTOR_SIZE << hbitmap_granularity(bitmap->bitmap);
> }
>
> -uint32_t bdrv_dirty_bitmap_meta_granularity(BdrvDirtyBitmap *bitmap)
> -{
> - return BDRV_SECTOR_SIZE << hbitmap_granularity(bitmap->meta);
> -}
Why? Unused? Not cool enough to mention?
