Re: [Qemu-devel] [PATCH v2 3/5] qcow2: Make copy_sectors() byte based

[Eric Blake <eblake@redhat.com>]

[-- Attachment #1: Type: text/plain, Size: 1671 bytes --]

On 06/06/2016 08:59 AM, Kevin Wolf wrote:
> This will allow copy on write operations where the overwritten part of
> the cluster is not aligned to sector boundaries.
> 
> Also rename the function because it has nothing to do with sectors any
> more.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/qcow2-cluster.c | 54 +++++++++++++++++++++++++--------------------------
>  1 file changed, 26 insertions(+), 28 deletions(-)
> 

>  
>      if (bs->encrypted) {
>          Error *err = NULL;
> +        int sector = (cluster_offset + offset_in_cluster) >> BDRV_SECTOR_BITS;

Potentially the wrong type...

>          assert(s->cipher);
> -        if (qcow2_encrypt_sectors(s, start_sect + n_start,
> -                                  iov.iov_base, iov.iov_base, n,
> -                                  true, &err) < 0) {
> +        assert((offset_in_cluster & BDRV_SECTOR_MASK) == 0);

Why is this one true? If I have a cluster of 4 sectors, why must
offset_in_cluster fall within only the first of those sectors?  Are you
missing a ~, to instead be asserting that offset_in_cluster is
sector-aligned?

> +        assert((bytes & ~BDRV_SECTOR_MASK) == 0);

This one looks correct, stating that the number of bytes to copy is a
sector multiple.

> +        if (qcow2_encrypt_sectors(s, sector, iov.iov_base, iov.iov_base,
> +                                  bytes >> BDRV_SECTOR_BITS, true, &err) < 0) {

...since encryption allows a 64-bit sector number for the case where the
image is larger than 2T.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 604 bytes --]