Subject: Re: [PATCH] Allow NBD to be used locally
From: Laurent Vivier <Laurent.Vivier@bull.net>
To: Pavel Machek <pavel@ucw.cz>
Cc: Paul.Clements@steeleye.com, nbd-general@lists.sourceforge.net,
       linux-kernel@vger.kernel.org
In-Reply-To: <20080202112336.GB5362@elf.ucw.cz>
References: <1201872332265-git-send-email-Laurent.Vivier@bull.net>
	 <20080202112336.GB5362@elf.ucw.cz>
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Date: Sat, 02 Feb 2008 16:26:11 +0100
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Le samedi 02 février 2008 à 12:23 +0100, Pavel Machek a écrit :
> On Fri 2008-02-01 14:25:32, Laurent Vivier wrote:
> > This patch allows Network Block Device to be mounted locally.
> 
> What is local nbd good for? Use loop instead...

It allows to write userlevel block device. In my case, I can mount disk
image of Qemu (qcow2, vmdk, ...).

> > It creates a kthread to avoid the deadlock described in NBD tools documentation.
> > So, if nbd-client hangs waiting pages, the kblockd thread can continue its
> > work and free pages.
> 
> Hmm, and if there are no other pages that can be freed? Unlikely, but
> can happen AFAICT.

Correct. The patch improves the NBD behavior even if it is not perfect.
And I think if no other page can be freed your system is in very bad
move ;-)

Laurent
-- 
----------------- Laurent.Vivier@bull.net  ------------------
  "La perfection est atteinte non quand il ne reste rien à
ajouter mais quand il ne reste rien à enlever." Saint Exupéry

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