Re: [Qemu-devel] [PATCH 12/18] block/dirty-bitmap: Add bdrv_dirty_iter_next_area

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

25.09.2017 18:49, Vladimir Sementsov-Ogievskiy wrote:
> I have a patch on list, which adds hbitmap_next_zero function, it may 
> help
> https://lists.nongnu.org/archive/html/qemu-devel/2017-02/msg00809.html

there is a mistake in this hbitmap_next_zero, I'll send today corrected 
version as part of small backup-related series.


>
> 13.09.2017 21:19, Max Reitz wrote:
>> This new function allows to look for a consecutively dirty area in a
>> dirty bitmap.
>>
>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>> ---
>>   include/block/dirty-bitmap.h |  2 ++
>>   block/dirty-bitmap.c         | 52 
>> ++++++++++++++++++++++++++++++++++++++++++++
>>   2 files changed, 54 insertions(+)
>>
>> diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
>> index a79a58d2c3..7654748700 100644
>> --- a/include/block/dirty-bitmap.h
>> +++ b/include/block/dirty-bitmap.h
>> @@ -90,6 +90,8 @@ void bdrv_set_dirty_bitmap_locked(BdrvDirtyBitmap 
>> *bitmap,
>>   void bdrv_reset_dirty_bitmap_locked(BdrvDirtyBitmap *bitmap,
>>                                       int64_t cur_sector, int64_t 
>> nr_sectors);
>>   int64_t bdrv_dirty_iter_next(BdrvDirtyBitmapIter *iter);
>> +bool bdrv_dirty_iter_next_area(BdrvDirtyBitmapIter *iter, uint64_t 
>> max_offset,
>> +                               uint64_t *offset, int *bytes);
>>   void bdrv_set_dirty_iter(BdrvDirtyBitmapIter *hbi, int64_t 
>> sector_num);
>>   int64_t bdrv_get_dirty_count(BdrvDirtyBitmap *bitmap);
>>   int64_t bdrv_get_meta_dirty_count(BdrvDirtyBitmap *bitmap);
>> diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
>> index aee57cf8c8..81b2f78016 100644
>> --- a/block/dirty-bitmap.c
>> +++ b/block/dirty-bitmap.c
>> @@ -550,6 +550,58 @@ int64_t bdrv_dirty_iter_next(BdrvDirtyBitmapIter 
>> *iter)
>>       return hbitmap_iter_next(&iter->hbi, true);
>>   }
>>   +/**
>> + * Return the next consecutively dirty area in the dirty bitmap
>> + * belonging to the given iterator @iter.
>> + *
>> + * @max_offset: Maximum value that may be returned for
>> + *              *offset + *bytes
>> + * @offset:     Will contain the start offset of the next dirty area
>> + * @bytes:      Will contain the length of the next dirty area
>> + *
>> + * Returns: True if a dirty area could be found before max_offset
>> + *          (which means that *offset and *bytes then contain valid
>> + *          values), false otherwise.
>> + */
>> +bool bdrv_dirty_iter_next_area(BdrvDirtyBitmapIter *iter, uint64_t 
>> max_offset,
>> +                               uint64_t *offset, int *bytes)
>> +{
>> +    uint32_t granularity = bdrv_dirty_bitmap_granularity(iter->bitmap);
>> +    uint64_t gran_max_offset;
>> +    int sector_gran = granularity >> BDRV_SECTOR_BITS;
>> +    int64_t ret;
>> +    int size;
>> +
>> +    if (DIV_ROUND_UP(max_offset, BDRV_SECTOR_SIZE) == 
>> iter->bitmap->size) {
>> +        /* If max_offset points to the image end, round it up by the
>> +         * bitmap granularity */
>> +        gran_max_offset = ROUND_UP(max_offset, granularity);
>> +    } else {
>> +        gran_max_offset = max_offset;
>> +    }
>> +
>> +    ret = hbitmap_iter_next(&iter->hbi, false);
>> +    if (ret < 0 || (ret << BDRV_SECTOR_BITS) + granularity > 
>> gran_max_offset) {
>> +        return false;
>> +    }
>> +
>> +    *offset = ret << BDRV_SECTOR_BITS;
>> +    size = 0;
>> +
>> +    assert(granularity <= INT_MAX);
>> +
>> +    do {
>> +        /* Advance iterator */
>> +        ret = hbitmap_iter_next(&iter->hbi, true);
>> +        size += granularity;
>> +    } while ((ret << BDRV_SECTOR_BITS) + granularity <= 
>> gran_max_offset &&
>> +             hbitmap_iter_next(&iter->hbi, false) == ret + 
>> sector_gran &&
>> +             size <= INT_MAX - granularity);
>> +
>> +    *bytes = MIN(size, max_offset - *offset);
>> +    return true;
>> +}
>> +
>>   /* Called within bdrv_dirty_bitmap_lock..unlock */
>>   void bdrv_set_dirty_bitmap_locked(BdrvDirtyBitmap *bitmap,
>>                                     int64_t cur_sector, int64_t 
>> nr_sectors)
>
>


-- 
Best regards,
Vladimir