On 17.12.2016 15:58, Vladimir Sementsov-Ogievskiy wrote:
> 09.12.2016 20:05, Max Reitz wrote:
>> On 22.11.2016 18:26, Vladimir Sementsov-Ogievskiy wrote:
>>> Realize block bitmap storing interface, to allow qcow2 images store
>>> persistent bitmaps.
>>>
>>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>>> ---
>>>  block/qcow2-bitmap.c | 451 +++++++++++++++++++++++++++++++++++++++++++++++++++
>>>  block/qcow2.c        |   1 +
> 
> [...]
> 
>>> +
>>> +/* store_bitmap_data()
>>> + * Store bitmap to image, filling bitmap table accordingly.
>>> + */
>>> +static uint64_t *store_bitmap_data(BlockDriverState *bs,
>>> +                                   BdrvDirtyBitmap *bitmap,
>>> +                                   uint32_t *bitmap_table_size, Error **errp)
>>> +{
>>> +    int ret;
>>> +    BDRVQcow2State *s = bs->opaque;
>>> +    int64_t sector;
>>> +    uint64_t dsc;
>>> +    uint64_t bm_size = bdrv_dirty_bitmap_size(bitmap);
>>> +    const char *bm_name = bdrv_dirty_bitmap_name(bitmap);
>>> +    uint8_t *buf = NULL;
>>> +    BdrvDirtyBitmapIter *dbi;
>>> +    uint64_t *tb;
>>> +    uint64_t tb_size =
>>> +            size_to_clusters(s,
>>> +                bdrv_dirty_bitmap_serialization_size(bitmap, 0, bm_size));
>>> +
>>> +    if (tb_size > BME_MAX_TABLE_SIZE ||
>>> +            tb_size * s->cluster_size > BME_MAX_PHYS_SIZE) {
>> Alignment to the opening parenthesis, please.
>>
>>> +        error_setg(errp, "Bitmap '%s' is too big", bm_name);
>>> +        return NULL;
>>> +    }
>>> +
>>> +    tb = g_try_new0(uint64_t, tb_size);
>>> +    if (tb == NULL) {
>>> +        error_setg(errp, "No memory");
>>> +        return NULL;
>>> +    }
>>> +
>>> +    dbi = bdrv_dirty_iter_new(bitmap, 0);
>>> +    buf = g_malloc(s->cluster_size);
>>> +    dsc = disk_sectors_in_bitmap_cluster(s, bitmap);
>>> +
>>> +    while ((sector = bdrv_dirty_iter_next(dbi)) != -1) {
>>> +        uint64_t cluster = sector / dsc;
>>> +        uint64_t end, write_size;
>>> +        int64_t off;
>>> +
>>> +        sector = cluster * dsc;
>>> +        end = MIN(bm_size, sector + dsc);
>>> +        write_size =
>>> +            bdrv_dirty_bitmap_serialization_size(bitmap, sector, end - sector);
>>> +
>>> +        off = qcow2_alloc_clusters(bs, s->cluster_size);
>>> +        if (off < 0) {
>>> +            error_setg_errno(errp, -off,
>>> +                             "Failed to allocate clusters for bitmap '%s'",
>>> +                             bm_name);
>>> +            goto fail;
>>> +        }
>>> +        tb[cluster] = off;
>> Somehow I would feel better with either an assert(cluster < tb_size);
>> here or an assert(bdrv_nb_sectors(bs) / dsc == tb_size); (plus the error
>> handling for bdrv_nb_sectors()) above the loop.
> 
> assert((bm_size - 1) / dsc == tb_size - 1) seems ok. and no additional
> error handling. Right?

Right, bm_size is already equal to bdrv_nb_sectors(bs), and it's not
necessarily a multiple of dsc. So that should be good. Alternatively, I
think the following would be slightly easier to read:

assert(DIV_ROUND_UP(bm_size, dsc) == tb_size);

> 
>>> +
>>> +        bdrv_dirty_bitmap_serialize_part(bitmap, buf, sector, end - sector);
>>> +        if (write_size < s->cluster_size) {
>>> +            memset(buf + write_size, 0, s->cluster_size - write_size);
>>> +        }
>> Should we assert that write_size <= s->cluster_size?
> 
> Ok
> 
> [...].
> 
>>
>>> +        const char *name = bdrv_dirty_bitmap_name(bitmap);
>>> +        uint32_t granularity = bdrv_dirty_bitmap_granularity(bitmap);
>>> +        Qcow2Bitmap *bm;
>>> +
>>> +        if (!bdrv_dirty_bitmap_get_persistance(bitmap)) {
>>> +            continue;
>>> +        }
>>> +
>>> +        if (++new_nb_bitmaps > QCOW2_MAX_BITMAPS) {
>>> +            error_setg(errp, "Too many persistent bitmaps");
>>> +            goto fail;
>>> +        }
>>> +
>>> +        new_dir_size += calc_dir_entry_size(strlen(name), 0);
>>> +        if (new_dir_size > QCOW2_MAX_BITMAP_DIRECTORY_SIZE) {
>>> +            error_setg(errp, "Too large bitmap directory");
>>> +            goto fail;
>>> +        }
>> You only need to increment new_nb_bitmaps and increase new_dir_size if
>> the bitmap does not already exist in the image (i.e. if
>> find_bitmap_by_name() below returns NULL).
> 
> Why? No, I need to check the whole sum and the whole size.

If the bitmap already exists, you don't create a new directory entry but
reuse the existing one. Therefore, the number of bitmaps in the image
and the directory size will not grow then.

Max

>>> +
>>> +        if (check_constraints_on_bitmap(bs, name, granularity) < 0) {
>>> +            error_setg(errp, "Bitmap '%s' doesn't satisfy the constraints",
>>> +                       name);
>>> +            goto fail;
>>> +        }
>>> +
>>> +        bm = find_bitmap_by_name(bm_list, name);
>>> +        if (bm == NULL) {
>>> +            bm = g_new0(Qcow2Bitmap, 1);
>>> +            bm->name = g_strdup(name);
>>> +            QSIMPLEQ_INSERT_TAIL(bm_list, bm, entry);
>>> +        } else {
>>> +            if (!(bm->flags & BME_FLAG_IN_USE) && can_write(bs)) {
>> Shouldn't we error out right at the beginning of this function if
>> can_write(bs) is false?
> 
> Hmm, right.
> 
> [...]
> 
> -- 
> Best regards,
> Vladimir
>