Re: [LSF/MM/BPF TOPIC] block drivers in user space

From: Hannes Reinecke <hare@suse.de>
To: Mike Christie <michael.christie@oracle.com>,
	Gabriel Krisman Bertazi <krisman@collabora.com>,
	lsf-pc@lists.linux-foundation.org
Cc: linux-block@vger.kernel.org
Subject: Re: [LSF/MM/BPF TOPIC] block drivers in user space
Date: Thu, 3 Mar 2022 08:09:00 +0100	[thread overview]
Message-ID: <57af4fe0-9042-729a-18e9-839a5f0a84ac@suse.de> (raw)
In-Reply-To: <526a8360-d7d3-1211-087b-c86d5a68380b@oracle.com>

On 3/2/22 17:52, Mike Christie wrote:
> On 2/21/22 1:59 PM, Gabriel Krisman Bertazi wrote:
>> I'd like to discuss an interface to implement user space block devices,
>> while avoiding local network NBD solutions.  There has been reiterated
> 
> Besides the tcmu approach, I've also worked on the local nbd based
> solution like here:
> 
> https://github.com/gluster/nbd-runner
> 
> Have you looked into a modern take that uses io_uring's socket features
> with the zero copy work that's being worked on for it? If so, what are
> the issues you have hit with that? Was it mostly issues with the zero
> copy part of it?
> 
> 
Problem is that we'd need an _inverse_ io_uring interface.
The current io_uring interface writes submission queue elements,
and waits for completion queue elements.

For this use-case we'd need to convert it to wait for submission queue 
elements, and write completion queue elements.

IE completely invert the operation.

Not sure if we can convert it _that_ easily ...

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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