netdev - Re: [Xen-devel] [PATCH 2/8] netback: add module unload function

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Date:	Tue, 5 Mar 2013 13:30:04 +0000
From:	Wei Liu <wei.liu2@...rix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	<wei.liu2@...rix.com>,
	"xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Ian Campbell <Ian.Campbell@...rix.com>,
	"annie.li@...cle.com" <annie.li@...cle.com>
Subject: Re: [Xen-devel] [PATCH 2/8] netback: add module unload function

On Mon, 2013-03-04 at 20:55 +0000, Konrad Rzeszutek Wilk wrote:
> On Fri, Feb 15, 2013 at 04:00:03PM +0000, Wei Liu wrote:
> > Enable users to unload netback module. Users should make sure there is not vif
> > runnig.
> 
> 'sure there are no vif's running.'
> 
> Any way of making this VIF part be automatic? Meaning that netback
> can figure out if there are VIFs running and if so don't unload
> all of the parts and just mention that you are leaking memory.
> 
> This looks quite dangerous - meaning if there are guests running and
> we for fun do 'rmmod xen_netback' it looks like we could crash dom0?
> 

Dom0 will not crash. But as you suggested in a latter email, I should
move the get/put module patch before this one.

The rationale behind this patch is that if there's anything wrong
discovered inside netback, we can just migrate all VMs to a new host,
unload old netback, load new netback then migrate all VMs back. This
should be useful for both production and testing.


Wei.

> > 
> > Signed-off-by: Wei Liu <wei.liu2@...rix.com>
> > ---
> >  drivers/net/xen-netback/common.h  |    1 +
> >  drivers/net/xen-netback/netback.c |   18 ++++++++++++++++++
> >  drivers/net/xen-netback/xenbus.c  |    5 +++++
> >  3 files changed, 24 insertions(+)
> > 
> > diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h
> > index 9d7f172..35d8772 100644
> > --- a/drivers/net/xen-netback/common.h
> > +++ b/drivers/net/xen-netback/common.h
> > @@ -120,6 +120,7 @@ void xenvif_get(struct xenvif *vif);
> >  void xenvif_put(struct xenvif *vif);
> >  
> >  int xenvif_xenbus_init(void);
> > +void xenvif_xenbus_exit(void);
> >  
> >  int xenvif_schedulable(struct xenvif *vif);
> >  
> > diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> > index db8d45a..de59098 100644
> > --- a/drivers/net/xen-netback/netback.c
> > +++ b/drivers/net/xen-netback/netback.c
> > @@ -1761,5 +1761,23 @@ failed_init:
> >  
> >  module_init(netback_init);
> >  
> > +static void __exit netback_exit(void)
> > +{
> > +	int group, i;
> > +	xenvif_xenbus_exit();
> 
> You should check the return code of this function.
> 
> > +	for (group = 0; group < xen_netbk_group_nr; group++) {
> > +		struct xen_netbk *netbk = &xen_netbk[group];
> > +		for (i = 0; i < MAX_PENDING_REQS; i++) {
> > +			if (netbk->mmap_pages[i])
> > +				__free_page(netbk->mmap_pages[i]);
> > +		}
> > +		del_timer_sync(&netbk->net_timer);
> > +		kthread_stop(netbk->task);
> > +	}
> > +	vfree(xen_netbk);
> > +}
> > +
> > +module_exit(netback_exit);
> > +
> >  MODULE_LICENSE("Dual BSD/GPL");
> >  MODULE_ALIAS("xen-backend:vif");
> > diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c
> > index 410018c..65d14f2 100644
> > --- a/drivers/net/xen-netback/xenbus.c
> > +++ b/drivers/net/xen-netback/xenbus.c
> > @@ -485,3 +485,8 @@ int xenvif_xenbus_init(void)
> >  {
> >  	return xenbus_register_backend(&netback_driver);
> >  }
> > +
> > +void xenvif_xenbus_exit(void)
> > +{
> > +	return xenbus_unregister_driver(&netback_driver);
> > +}
> > -- 
> > 1.7.10.4
> > 
> > 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@...ts.xen.org
> > http://lists.xen.org/xen-devel
> > 


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