On 08/07/2017 08:55 PM, John Snow wrote: > > > 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.
And definitely conflicts with my work on byte-based block status.
>>
>> -uint32_t bdrv_dirty_bitmap_meta_granularity(BdrvDirtyBitmap *bitmap)
>> -{
>> - return BDRV_SECTOR_SIZE << hbitmap_granularity(bitmap->meta);
>> -}
>
> Why? Unused? Not cool enough to mention?
Already deleted as unused in my byte-based series.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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