linux-kernel - Re: [PATCH v3 12/13] xen/pvcalls: implement release command

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Date:   Fri, 8 Sep 2017 16:09:02 -0700 (PDT)
From:   Stefano Stabellini <sstabellini@...nel.org>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
cc:     Stefano Stabellini <sstabellini@...nel.org>,
        xen-devel@...ts.xen.org, linux-kernel@...r.kernel.org,
        jgross@...e.com, Stefano Stabellini <stefano@...reto.com>
Subject: Re: [PATCH v3 12/13] xen/pvcalls: implement release command

On Tue, 15 Aug 2017, Boris Ostrovsky wrote:
> On 07/31/2017 06:57 PM, Stefano Stabellini wrote:
> > Send PVCALLS_RELEASE to the backend and wait for a reply. Take both
> > in_mutex and out_mutex to avoid concurrent accesses. Then, free the
> > socket.
> >
> > For passive sockets, check whether we have already pre-allocated an
> > active socket for the purpose of being accepted. If so, free that as
> > well.
> >
> > Signed-off-by: Stefano Stabellini <stefano@...reto.com>
> > CC: boris.ostrovsky@...cle.com
> > CC: jgross@...e.com
> > ---
> >  drivers/xen/pvcalls-front.c | 88 +++++++++++++++++++++++++++++++++++++++++++++
> >  drivers/xen/pvcalls-front.h |  1 +
> >  2 files changed, 89 insertions(+)
> >
> > diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> > index 1c975d6..775a6d2 100644
> > --- a/drivers/xen/pvcalls-front.c
> > +++ b/drivers/xen/pvcalls-front.c
> > @@ -192,6 +192,23 @@ static irqreturn_t pvcalls_front_conn_handler(int irq, void *sock_map)
> >  	return IRQ_HANDLED;
> >  }
> >  
> > +static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
> > +				   struct sock_mapping *map)
> > +{
> > +	int i;
> > +
> > +	spin_lock(&bedata->pvcallss_lock);
> > +	if (!list_empty(&map->list))
> > +		list_del_init(&map->list);
> > +	spin_unlock(&bedata->pvcallss_lock);
> > +
> > +	for (i = 0; i < (1 << map->active.ring->ring_order); i++)
> > +		gnttab_end_foreign_access(map->active.ring->ref[i], 0, 0);
> > +	gnttab_end_foreign_access(map->active.ref, 0, 0);
> > +	free_page((unsigned long)map->active.ring);
> > +	unbind_from_irqhandler(map->active.irq, map);
> 
> Would it better to first unbind the handler? Any chance an interrupt
> might come in?

Fair enough, I'll do that.


> > +}
> > +
> >  int pvcalls_front_socket(struct socket *sock)
> >  {
> >  	struct pvcalls_bedata *bedata;
> > @@ -853,6 +870,77 @@ unsigned int pvcalls_front_poll(struct file *file, struct socket *sock,
> >  		return pvcalls_front_poll_passive(file, bedata, map, wait);
> >  }
> >  
> > +int pvcalls_front_release(struct socket *sock)
> > +{
> > +	struct pvcalls_bedata *bedata;
> > +	struct sock_mapping *map;
> > +	int req_id, notify, ret;
> > +	struct xen_pvcalls_request *req;
> > +
> > +	if (!pvcalls_front_dev)
> > +		return -EIO;
> > +	bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
> > +
> > +	if (sock->sk == NULL)
> > +		return 0;
> 
> This can go above bedata access.

Yes, good idea.


> (You are going to address locking here so I won't review the rest)

Yes, I will. Thanks for the review! And sorry for taking so long to
come back to you.