linux-kernel - Re: [PATCH] virtio: Return correct errno for function init

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Message-Id: <20160713140540.78c9ab01.cornelia.huck@de.ibm.com>
Date:	Wed, 13 Jul 2016 14:05:40 +0200
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	Minfei Huang <mnghuan@...il.com>
Cc:	mst@...hat.com, Minfei Huang <minfei.hmf@...baba-inc.com>,
	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH] virtio: Return correct errno for function init_vq's
 failure

On Wed, 13 Jul 2016 19:54:00 +0800
Minfei Huang <mnghuan@...il.com> wrote:

> On 07/06/16 at 11:18P, Cornelia Huck wrote:
> > On Mon, 27 Jun 2016 10:09:18 +0800
> > Minfei Huang <mnghuan@...il.com> wrote:
> > 
> > > The error number -ENOENT or 0 will be returned, if we can not allocate
> > > more memory in function init_vq. If host can support multiple virtual
> > > queues, and we fails to allocate necessary memory structures for vq,
> > > kernel may crash due to incorrect returning.
> > > 
> > > To fix it, kernel will return correct value in init_vq.
> > The error handling in this function looks horrible.
> > 
> > When mq was introduced, init_vq started mixing up several things:
> > - The mq feature is not available - which is not an error, and
> > therefore should not have any influence on the return code.
> > - One of the several memory allocations failed - only ->vqs gets
> > special treatment, however.
> > - The ->find_vqs callback failed.
> 
> Yep. And without this patch, it is silent for boot failure. I think it
> makes sense to let user notify about this failure.

Agreed.

> 
> > 
> > Your patch fixes the code, but it is still very convoluted due to the
> > temporary arrays.
> > 
> > May it be worthwile to introduce a helper for setting up the virtqueues
> > where all virtqueues are essentially the same and just get a
> > consecutive number? Michael?
> > 
> 
> Hmm, How about refactor this function to make it more readable, since we
> do a lot of work in it.
> 
> I will post an update to refactor this function.

Anything to make this more readable probably helps :)