[Libguestfs] Communication issues between NBD driver and NBDKit server

[Nikolaus Rath]

On May 16 2022, "yukuai (C)" <yukuai3 at huawei.com> wrote:
> 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

Ah, I guess that makes sense. I thought that not specifying a timeout
meant "never time out".

I'll set this to a large value and report back if the problem recurs.

Thanks!
-Nikolaus

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