Re: [Qemu-block] [PATCH v4 4/6] nbd/server: implement dirty bitmap export

[Vladimir Sementsov-Ogievskiy]

08.06.2018 18:23, Vladimir Sementsov-Ogievskiy wrote:
> Handle new NBD meta namespace: "qemu", and corresponding queries:
> "qemu:dirty-bitmap:<export bitmap name>".
>
> With new metadata context negotiated, BLOCK_STATUS query will reply
> with dirty-bitmap data, converted to extents. New public function
> nbd_export_bitmap selects bitmap to export. For now, only one bitmap
> may be exported.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---

[...]

> +static unsigned bitmap_to_extents(BdrvDirtyBitmap *bitmap, uint64_t offset,
> +                                  uint64_t length, NBDExtent *extents,
> +                                  unsigned nb_extents)
> +{
> +    uint64_t begin = offset, end;
> +    uint64_t overall_end = offset + length;
> +    unsigned i = 0;
> +    BdrvDirtyBitmapIter *it;
> +    bool dirty;
> +
> +    bdrv_dirty_bitmap_lock(bitmap);
> +
> +    it = bdrv_dirty_iter_new(bitmap);
> +    dirty = bdrv_get_dirty_locked(NULL, bitmap, offset);
> +
> +    while (begin < overall_end && i < nb_extents) {
> +        if (dirty) {
> +            end = bdrv_dirty_bitmap_next_zero(bitmap, begin);
> +        } else {
> +            bdrv_set_dirty_iter(it, begin);
> +            end = bdrv_dirty_iter_next(it);
> +        }
> +        if (end == -1) {
> +            end = overall_end;

here better is bdrv_dirty_bitmap_size()

> +        }

and here we should crop it to overall_end in case of REQ_ONE

> +
> +        i += add_extents(extents + i, nb_extents - i, end - begin,
> +                         dirty ? NBD_STATE_DIRTY : 0);
> +        begin = end;
> +        dirty = !dirty;
> +    }
> +
> +    bdrv_dirty_iter_free(it);
> +
> +    bdrv_dirty_bitmap_unlock(bitmap);
> +
> +    return i;
> +}

--
Best regards,
Vladimir