Am 13.11.2015 um 16:32 hat Lucian Petrut geschrieben:
>
> At the moment, qemu-img extends new image virtual sizes based
> on the CHS algorithm provided by the VHD specs in order to
> ensure that the disk geometry (and payload as seen by some
> guests which use the CHS value) can fit in the requested disk.
>
> This patch drops this behavior, as it breaks compatibility with
> Azure, which requires the MB alignment to be preserved.
>
> Signed-off-by: Lucian Petrut <lpet...@cloudbasesolutions.com>
> ---
> Proposed fix for https://bugs.launchpad.net/qemu/+bug/1490611
This may fix one scenario, but it's sure to break others which are
currently working. The problem has been discussed more than once and
it's essentially a problem with MS using their own file format
inconsistently.
I think we once came to the conclusion that looking at the creator
string might be a working heuristics. Apparently this was never
implemented - I don't remember whether that was because we noticed a
problem with it, or just because noone got to it.
Jeff and Peter, I seem to remember that you were involved the last time
we discussed this, so does one of you remember why we didn't implement
this heuristics in the end?
Kevin
> diff --git a/block/vpc.c b/block/vpc.c
> index 299d373..77c0a28 100644
> --- a/block/vpc.c
> +++ b/block/vpc.c
> @@ -762,7 +762,6 @@ static int vpc_create(const char *filename, QemuOpts
> *opts, Error **errp)
> uint8_t buf[1024];
> VHDFooter *footer = (VHDFooter *) buf;
> char *disk_type_param;
> - int i;
> uint16_t cyls = 0;
> uint8_t heads = 0;
> uint8_t secs_per_cyl = 0;
> @@ -802,31 +801,16 @@ static int vpc_create(const char *filename, QemuOpts
> *opts, Error **errp)
> goto out;
> }
>
> - /*
> - * Calculate matching total_size and geometry. Increase the number of
> - * sectors requested until we get enough (or fail). This ensures that
> - * qemu-img convert doesn't truncate images, but rather rounds up.
> - *
> - * If the image size can't be represented by a spec conform CHS geometry,
> - * we set the geometry to 65535 x 16 x 255 (CxHxS) sectors and use
> - * the image size from the VHD footer to calculate total_sectors.
> - */
> - total_sectors = MIN(VHD_MAX_GEOMETRY, total_size / BDRV_SECTOR_SIZE);
> - for (i = 0; total_sectors > (int64_t)cyls * heads * secs_per_cyl; i++) {
> - calculate_geometry(total_sectors + i, &cyls, &heads, &secs_per_cyl);
> - }
> -
> - if ((int64_t)cyls * heads * secs_per_cyl == VHD_MAX_GEOMETRY) {
> - total_sectors = total_size / BDRV_SECTOR_SIZE;
> + total_sectors = total_size / BDRV_SECTOR_SIZE;
> + if (total_sectors > VHD_MAX_SECTORS) {
> /* Allow a maximum disk size of approximately 2 TB */
> - if (total_sectors > VHD_MAX_SECTORS) {
> - ret = -EFBIG;
> - goto out;
> - }
> - } else {
> - total_sectors = (int64_t)cyls * heads * secs_per_cyl;
> - total_size = total_sectors * BDRV_SECTOR_SIZE;
> + ret = -EFBIG;
> + goto out;
> }
> + /*
> + * Calculate geometry.
> + */
> + calculate_geometry(total_sectors, &cyls, &heads, &secs_per_cyl);
>
> /* Prepare the Hard Disk Footer */
> memset(buf, 0, 1024);
