linux-kernel - Re: [Nbd] [PATCH 2/2] nbd: Disallow ioctls on disconnected block device

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Date:	Sat, 16 Jul 2016 13:26:32 +0200
From:	Wouter Verhelst <w@...r.be>
To:	Pranay Srivastava <pranjas@...il.com>
Cc:	Alex Bligh <alex@...x.org.uk>,
	"nbd-general@...ts.sourceforge.net" 
	<nbd-general@...ts.sourceforge.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Nbd] [PATCH 2/2] nbd: Disallow ioctls on disconnected block
 device

On Sat, Jul 16, 2016 at 03:38:40PM +0530, Pranay Srivastava wrote:
> Okay. So how about we include some negotiated key which goes in with every
> request which the server could maintain for clients that can be checked while
> resetting the connection with the same server?

Wut?

> So am I correct that this situation can
> indeed happen or the server will throw an error back to client in case
> the troubled
> nbd-client is trying to reconnect to the original server but requests
> are going to
> another server?
> 
> If yes to above query then what is the best effort we can do to avoid
> such scenarios?

Tell userspace not to do stupid things?

This isn't a problem. The kernel assumes that whatever userspace does,
once the connection is set up again everything's the way it was before.
If that's not true, then userspace is to blame, not kernel space.

Adding a "key" which we need to pass is going to make things wildly more
complicated for no benefit.

-- 
< ron> I mean, the main *practical* problem with C++, is there's like a dozen
       people in the world who think they really understand all of its rules,
       and pretty much all of them are just lying to themselves too.
 -- #debian-devel, OFTC, 2016-02-12