[libvirt PATCH] vircgroupv2devices: fix counting entries in BPF map

[Erik Skultety]

On Tue, Aug 11, 2020 at 12:13:47PM +0200, Pavel Hrdina wrote:
> BPF syscall BPF_MAP_GET_NEXT_KEY returns -1 if something fails but it
> will also return -1 if trying to get next key using the last key in the
> map with errno set to ENOENT.
>
> If there are VMs running and libvirtd is restarted and user tries to
> call some cgroup devices operation on a VM we need to get the count of
> entries in BPF map and it fails which will result in error when trying
> to attach/detech devices.
>
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1833321
>
> Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
> ---
Reviewed-by: Erik Skultety <eskultet at redhat.com>