Re: [Qemu-devel] [PATCH] block/iscsi: speed up read for unallocated sectors

[Paolo Bonzini]

Il 27/03/2014 14:43, Peter Lieven ha scritto:
> +static void iscsi_allocationmap_set(IscsiLun *iscsilun, int64_t sector_num,
> +                                    int nb_sectors)
> +{
> +    if (!iscsilun->cluster_sectors) {
> +        return;
> +    }
> +    bitmap_set(iscsilun->allocationmap,
> +               sector_num / iscsilun->cluster_sectors,
> +               DIV_ROUND_UP(nb_sectors, iscsilun->cluster_sectors));
> +}
> +
> +static void iscsi_allocationmap_clear(IscsiLun *iscsilun, int64_t sector_num,
> +                                      int nb_sectors)
> +{
> +    if (!iscsilun->cluster_sectors) {
> +        return;
> +    }
> +    bitmap_clear(iscsilun->allocationmap,
> +                 sector_num / iscsilun->cluster_sectors,
> +                 DIV_ROUND_UP(nb_sectors, iscsilun->cluster_sectors));
> +}
> +

Here you need to round the other way, because partial clusters are not 
unmapped:

        cluster_num = DIV_ROUND_UP(sector_num, iscsi->cluster_sectors);
        nb_clusters = (sector_num + nb_sectors) / iscsi->cluster_sectors
                - cluster_num;
        bitmap_clear(iscsilun->allocationmap, cluster_num, nb_clusters);

Paolo