Re: [Qemu-devel] [PATCH 12/12] Add disk_size field to BlockDriverState structure

[Stefan Hajnoczi <stefanha@gmail.com>]

On Sat, Jun 4, 2011 at 1:44 AM, Fam Zheng <famcool@gmail.com> wrote:
> The `qemu-img info` results for mono flat image are no longer
> accurate, as the "disk size" was the length of bs->file, which is not
> the case for multi file images (such as vmdk images with multiple
> files).
> The new field disk_size in BlockDriverState can be used by block
> driver to tell the exact disk size of block image (only valid if the
> field is set to non-zero).
>
> Signed-off-by: Fam Zheng <famcool@gmail.com>
> ---
>  block/vmdk.c |    1 +
>  block_int.h  |    1 +
>  qemu-img.c   |    6 +++++-
>  3 files changed, 7 insertions(+), 1 deletions(-)

Instead of introducing a variable please add a new BlockDriver
.bdrv_get_allocated_file_size() function pointer and move
get_allocated_file_size() from qemu-img.c into block/raw-posix.c and
block/raw-win32.c.

qemu-img.c should call bdrv_get_allocated_file_size() and
bdrv_get_allocated_file_size() could look like this:

int bdrv_get_allocated_file_size(BlockDriverState *bs, int64_t *size)
{
    BlockDriver *drv = bs->drv;

    if (!drv) {
        return -ENOMEDIUM;
    }

    if (drv->bdrv_get_allocated_file_size) {
        return drv->bdrv_get_allocated_file_size(bs, size);
    }

    if (bs->file) {
        return bdrv_get_allocated_file_size(bs->file, size);
    }
    return -ENOTSUP;
}

> @@ -607,6 +607,7 @@ static int vmdk_open_desc_file(BlockDriverState
> *bs, int flags)
>     extent = s->extents;
>     vmdk_parse_extents(buf, s->extents, bs->file->filename);
>     bs->total_sectors = extent->sectors;
> +    bs->disk_size = bdrv_getlength(bs->file) + bdrv_getlength(extent->file);

This should call bdrv_get_allocated_file_size() so add together the
actually allocated amount, not what bdrv_getlength() returns.

Stefan