[Libguestfs] [PATCH nbdkit] cow: Fix assert failure in cow_extents

[Eric Blake]

On Sat, Jul 24, 2021 at 02:06:16PM +0100, Richard W.M. Jones wrote:
> $ nbdkit sparse-random 4G --filter=cow --run 'nbdinfo --map $uri'
> nbdkit: cow.c:591: cow_extents: Assertion `count > 0' failed.
> 
> This is caused because nbdinfo calls us with count = 0xfffffe00 which
> is rounded up to the next boundary and overflows (so count = 0).
> 
> Use a 64 bit variable for count to allow rounding up.
> ---
>  tests/Makefile.am               |  2 ++
>  filters/cow/cow.c               | 16 +++++++++---
>  tests/test-cow-extents-large.sh | 46 +++++++++++++++++++++++++++++++++
>  3 files changed, 61 insertions(+), 3 deletions(-)

Ack.

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