Re: [Qemu-block] [Qemu-devel] [PATCH] raw-posix: add 'offset' and 'size' options

[Eric Blake]

On 10/02/2016 02:13 PM, Tomáš Golembiovský wrote:
> Added two new options 'offset' and 'size'. This makes it possible to use
> only part of the file as a device. This can be used e.g. to limit the
> access only to single partition in a disk image or use a disk inside a
> tar archive (like OVA).
> 
> For now this is only possible for files in read-only mode. It should be
> possible to extend it later to allow read-write mode, but would probably
> require that the size of the device is kept constant (i.e. no resizing).
> 
> Signed-off-by: Tomáš Golembiovský <address@hidden>
> ---
>  block/raw-posix.c | 97 
> +++++++++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 91 insertions(+), 6 deletions(-)
> 

> +    s->offset = qemu_opt_get_size(opts, "offset", 0);
> +    s->assumed_size = qemu_opt_get_size(opts, BLOCK_OPT_SIZE, 0);
> +
> +    if (((bs->drv != &bdrv_file) || !bs->read_only) &&
> +        ((s->offset > 0) || (s->assumed_size > 0))) {

Over-parenthesized.

> @@ -443,6 +468,23 @@ static int raw_open_common(BlockDriverState *bs, QDict 
> *options,
>      }
>      s->fd = fd;
>  
> +    /* Check size and offset */
> +    real_size = raw_getlength_real(bs);
> +    if (real_size < (s->offset + s->assumed_size)) {
> +        if (s->assumed_size == 0) {
> +            error_setg(errp, "The offset has to be smaller than actual size "
> +                             "of the containing file (%ld) ",
> +                             real_size);

Won't compile on 32-bit platforms.  %ld is not necessarily synonymous
with int64_t; you need to use PRId64 instead.  Multiple times through
your patch.

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

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