Re: [PATCH v3 04/16] qcow2: Keep unknown extra snapshot data

[Eric Blake]

On 10/11/19 10:28 AM, Max Reitz wrote:
> The qcow2 specification says to ignore unknown extra data fields in
> snapshot table entries.  Currently, we discard it whenever we update the
> image, which is a bit different from "ignore".
>
> This patch makes the qcow2 driver keep all unknown extra data fields
> when updating an image's snapshot table.
>
> Signed-off-by: Max Reitz <address@hidden>
> Reviewed-by: Eric Blake <address@hidden>
> ---

>   /* Bitmap header extension constraints */
>   #define QCOW2_MAX_BITMAPS 65535
>   #define QCOW2_MAX_BITMAP_DIRECTORY_SIZE (1024 * QCOW2_MAX_BITMAPS)
> @@ -181,6 +184,8 @@ typedef struct QCowSnapshot {
>       uint32_t date_sec;
>       uint32_t date_nsec;
>       uint64_t vm_clock_nsec;
> +    uint32_t extra_data_size;
> +    void *unknown_extra_data; /* Extra data past QCowSnapshotExtraData */

Would it be worth a comment change:

uint32_t extra_data_size; /* Size of all extra data, including 
QCowSnapshotExtraData */
void *unknown_extra_data; /* Data beyond QCowSnapshotExtraData, if any */

Either way, R-b stands.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org