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Date: Fri, 21 Jun 2013 22:00:00 +0200
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Subject: Re: [Qemu-devel] [PATCH 2/2] iscsi: add intelligent has_zero_init
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To: Peter Lieven <pl@kamp.de>
Cc: Kevin Wolf <kwolf@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, qemu-devel@nongnu.org, ronniesahlberg@gmail.com

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