On 14.01.19 15:01, Vladimir Sementsov-Ogievskiy wrote:
> 14.01.2019 16:10, Max Reitz wrote:
>> On 29.12.18 13:20, Vladimir Sementsov-Ogievskiy wrote:
>>> Simplify backup_incremental_init_copy_bitmap using the function
>>> bdrv_dirty_bitmap_next_dirty_area.
>>>
>>> Note: move to job->len instead of bitmap size: it should not matter but
>>> less code.
>>>
>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
>>> ---
>>> block/backup.c | 40 ++++++++++++----------------------------
>>> 1 file changed, 12 insertions(+), 28 deletions(-)
>>
>> Overall: What is this function even supposed to do? To me, it looks
>> like it marks all areas in job->copy_bitmap dirty that are dirty in
>> job->sync_bitmap.
>>
>> If so, wouldn't just replacing this by hbitmap_merge() simplify things
>> further?
>>
>>> diff --git a/block/backup.c b/block/backup.c
>>> index 435414e964..fbe7ce19e1 100644
>>> --- a/block/backup.c
>>> +++ b/block/backup.c
>>> @@ -406,43 +406,27 @@ static int coroutine_fn
>>> backup_run_incremental(BackupBlockJob *job)
>>
>> [...]
>>
>>> + while (bdrv_dirty_bitmap_next_dirty_area(job->sync_bitmap,
>>> + &offset, &bytes))
>>> + {
>>> + uint64_t cluster = offset / job->cluster_size;
>>> + uint64_t last_cluster = (offset + bytes) / job->cluster_size;
>>>
>>> - next_cluster = DIV_ROUND_UP(offset, job->cluster_size);
>>> - hbitmap_set(job->copy_bitmap, cluster, next_cluster - cluster);
>>> - if (next_cluster >= end) {
>>> + hbitmap_set(job->copy_bitmap, cluster, last_cluster - cluster + 1);
>>
>> Why the +1? Shouldn't the division for last_cluster round up instead?
>>
>>> +
>>> + offset = (last_cluster + 1) * job->cluster_size;
>>
>> Same here.
>
> last cluster is not "end", but it's last dirty cluster. so number of dirty
> clusters is last_cluster - cluster + 1, and next offset is calculated through
> +1 too.
>
> If I round up division result, I'll get last for most cases, but "end" (next
> after the last), for the case when offset % job->cluster_size == 0, so, how
> to use it?Doesn't bdrv_dirty_bitmap_next_dirty_area() return a range [offset, offset + bytes), i.e. where "offset + bytes" is the first clean offset? Max
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