netdev - Re: [PATCH] cnic: Fix ISCSI_KEVENT_IF

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Date:	Wed, 29 Jul 2009 01:42:51 -0700
From:	"Anil Veerabhadrappa" <anilgv@...adcom.com>
To:	"open-iscsi@...glegroups.com" <open-iscsi@...glegroups.com>
cc:	"'Mike Christie'" <michaelc@...wisc.edu>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"James.Bottomley@...senPartnership.com" 
	<James.Bottomley@...senPartnership.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>
Subject: Re: [PATCH] cnic: Fix ISCSI_KEVENT_IF_DOWN message handling.

On Wed, 2009-07-29 at 00:55 -0700, Michael Chan wrote:
> Mike Christie wrote:
> 
> > Michael Chan wrote:
> > > When a net device goes down or when the bnx2i driver is unloaded,
> > > the code was not generating the ISCSI_KEVENT_IF_DOWN message
> > > properly and this could cause the userspace driver to crash.
> > >
> > > This is fixed by sending the message properly in the shutdown
> path.
> > > cnic_uio_stop() is also added to send the message when bnx2i is
> > > unregistering.
> > >
> > > Signed-off-by: Michael Chan <mchan@...adcom.com>
> > > ---
> > >  drivers/net/cnic.c |   23 +++++++++++++++++++++--
> > >  1 files changed, 21 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/net/cnic.c b/drivers/net/cnic.c
> > > index 4d1515f..4869d77 100644
> > > --- a/drivers/net/cnic.c
> > > +++ b/drivers/net/cnic.c
> > > @@ -227,7 +227,7 @@ static int cnic_send_nlmsg(struct
> > cnic_local *cp, u32 type,
> > >     }
> > >
> > >     rcu_read_lock();
> > > -   ulp_ops = rcu_dereference(cp->ulp_ops[CNIC_ULP_ISCSI]);
> > > +   ulp_ops = rcu_dereference(cnic_ulp_tbl[CNIC_ULP_ISCSI]);
> > >     if (ulp_ops)
> > >             ulp_ops->iscsi_nl_send_msg(cp->dev, msg_type, buf,
> len);
> > >     rcu_read_unlock();
> > > @@ -319,6 +319,20 @@ static int cnic_abort_prep(struct
> > cnic_sock *csk)
> > >     return 0;
> > >  }
> > >
> > > +static void cnic_uio_stop(void)
> > > +{
> > > +   struct cnic_dev *dev;
> > > +
> > > +   read_lock(&cnic_dev_lock);
> > > +   list_for_each_entry(dev, &cnic_dev_list, list) {
> > > +           struct cnic_local *cp = dev->cnic_priv;
> > > +
> > > +           if (cp->cnic_uinfo)
> > > +                   cnic_send_nlmsg(cp, ISCSI_KEVENT_IF_DOWN,
> NULL);
> >
> > I don't think you can call this with the cnic_dev_lock held.
> > They have
> > the same sleeping restrictions as a spin_lock right? If so,
> > the problem
> > is that iscsi_nl_send_ms calls iscsi_offload_mesg which uses
> GFP_NOIO
> > and can sleep.
> >
> >
> In that case, can I send in a patch to change iscsi_offload_mesg() to
> use GFP_ATOMIC?
> 
After this change, if iscsi_transport is unable to push the message to
user daemon because of memory issues, will the original issue of uio
crash re-appear?

Original issue: A did not notify B
Fix : A calls C to send message to B
      if C cannot deliver message to B, original problem stays???


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