[Libguestfs] Communication issues between NBD driver and NBDKit server

[yukuai (C)]

On 2022/05/16 3:25, Richard W.M. Jones wrote:
> On Sun, May 15, 2022 at 08:12:59PM +0100, Nikolaus Rath wrote:
>> Do you see any way for this to happen?
> 
> I think it's impossible.  A more likely explanation follows.
> 
> If you look at the kernel code, the NBD_CMD_INFLIGHT command flag is
> cleared when a command times out:
> 
>    https://github.com/torvalds/linux/blob/0cdd776ec92c0fec768c7079331804d3e52d4b27/drivers/block/nbd.c#L407
> 
> That's the place where it would have printed the "Possible stuck
> request" message.
> 
> Some time later, nbdkit actually replies to the message (for the first
> and only time) and in that code the flag is checked and found to be
> clear already, causing the "Suspicious reply" message to be printed:
Hi,

You are right, can you try the following patch?

https://lists.debian.org/nbd/2022/04/msg00212.html

Thanks,
Kuai
> 
>    https://github.com/torvalds/linux/blob/0cdd776ec92c0fec768c7079331804d3e52d4b27/drivers/block/nbd.c#L749
> 
> I'd say you need to increase the timeout and/or work out why the S3
> plugin is taking so long to respond.
> 
> Rich.
>