Re: [Qemu-devel] [PATCH] vmdk: return ENOTSUP before offset overflow

[Eric Blake]

On 03/21/2018 09:40 PM, yuchenlin--- via Qemu-devel wrote:
> From: yuchenlin <address@hidden>
>
> VMDK has a hard limitation of extent size, which is due to the size of grain
> table entry is 32 bits. It means it can only point to a grain located at
> offset = 2^32. To prevent offset overflow and record a useless offset
> in grain table. We should return un-support here.
>
> Signed-off-by: yuchenlin <address@hidden>
> ---
>   block/vmdk.c | 6 ++++++
>   1 file changed, 6 insertions(+)
>
> diff --git a/block/vmdk.c b/block/vmdk.c
> index f94c49a9c0..d8fc961940 100644
> --- a/block/vmdk.c
> +++ b/block/vmdk.c
> @@ -47,6 +47,9 @@
>   #define VMDK4_FLAG_MARKER (1 << 17)
>   #define VMDK4_GD_AT_END 0xffffffffffffffffULL
>   
> +/* 2TB */
> +#define VMDK_EXTENT_SIZE_LIMIT (2199023255552)

Please spell this '(2ULL * 1024 * 1024 * 1024 * 1024)', or even rebase 
it on top of Phillipe's BYTE-based definitions as '2 * T_BYTE' (v2 
proposed a cunits.h, although v3 is still pending posting and may rename 
the header units.h)

https://lists.gnu.org/archive/html/qemu-devel/2018-03/msg01077.html

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org