Re: [Qemu-devel] [PATCH 2/2] iscsi: add intelligent has_zero_init check

[Paolo Bonzini]

Il 20/06/2013 20:20, Peter Lieven ha scritto:
> +    for (lba = 0; lba < iscsilun->num_blocks; lba += 1 << 26) {
> +        nb_sectors = 1 << 26;
> +        if (lba + nb_sectors > iscsilun->num_blocks) {
> +            nb_sectors = iscsilun->num_blocks - lba;
> +        }
> +        nb_sectors *= (iscsilun->block_size / BDRV_SECTOR_SIZE);
> +        n = 0;
> +        ret = iscsi_co_is_allocated(bs, lba, nb_sectors, &n);
> +        if (ret || n != nb_sectors) {
> +            return 0;
> +        }

I would just do lba += n in the for loop, and only exit if n == 0.  The
SCSI spec does not forbid splitting a single allocated area into
multiple descriptors, or only returning part of an allocated area into
the last descriptor.

Otherwise looks good, but you may want to cache the result.  It would
not be 1 anymore after the first write.

Paolo