[Libguestfs] [PATCH nbdkit] vddk: Suppress errors in can_extents test (RHBZ#1709211).

[Eric Blake]

On 5/7/20 6:23 AM, Richard W.M. Jones wrote:
> In can_extents we test whether the VDDK function
> VixDiskLib_QueryAllocatedBlocks works before declaring that extents
> are supported.  This VDDK function can fail in several ways but most
> notable if the server doesn't support querying extents.
> 
> In this case VDDK raises an error message through the error_function
> callback, which we turn into a call to nbdkit_error.  In most cases
> this will cause something to be printed to stderr and/or logged
> noisily to syslog, which is not desirable.
> 
> This commit adds a per-thread error suppression mechanism so that we
> can temporarily hide errors, especially while doing this test, but I
> guess it might be useful in future in other cases too.
> 
> Note this only affects a narrow range of versions of VMware ESXi and
> VDDK.  In particular to see this problem you would need
> VMware ESXi (server) <= 5.5 and VDDK (client) >= 6.7.
> ---
>   plugins/vddk/vddk.c | 80 ++++++++++++++++++++++++++++++++++++---------
>   1 file changed, 64 insertions(+), 16 deletions(-)

ACK.

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