netdev - Re: [PATCH] rds_rdma: don't assume infiniband device is PCI

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Date:	Fri, 6 Jan 2012 13:57:50 -0200
From:	Thadeu Lima de Souza Cascardo <cascardo@...ux.vnet.ibm.com>
To:	Venkat Venkatsubra <venkat.x.venkatsubra@...cle.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, dledford@...hat.com,
	Jes.Sorensen@...hat.com, rds-devel@....oracle.com
Subject: Re: [PATCH] rds_rdma: don't assume infiniband device is PCI

On Thu, Jan 05, 2012 at 03:05:24PM -0200, Thadeu Lima de Souza Cascardo wrote:
> > ----- Original Message -----
> > From: cascardo@...ux.vnet.ibm.com
> > To: venkat.x.venkatsubra@...cle.com
> > Cc: davem@...emloft.net, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, cascardo@...ux.vnet.ibm.com, dledford@...hat.com, Jes.Sorensen@...hat.com, rds-devel@....oracle.com
> > Sent: Wednesday, January 4, 2012 4:03:42 PM GMT -06:00 US/Canada Central
> > Subject: [PATCH] rds_rdma: don't assume infiniband device is PCI
> > 
> > RDS code assumes that the struct ib_device dma_device member, which is a
> > pointer, points to a struct device embedded in a struct pci_dev.
> > 
> > This is not the case for ehca, for example, which is a OF driver, and
> > makes dma_device point to a struct device embedded in a struct
> > platform_device.
> > 
> > This will make the system crash when rds_rdma is loaded in a system
> > with ehca, since it will try to access the bus member of a non-existent
> > struct pci_dev.
> > 
> > The only reason rds_rdma uses the struct pci_dev is to get the NUMA node
> > the device is attached to. Using dev_to_node for that is much better,
> > since it won't assume which bus the infiniband is attached to.
> > 
> > Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@...ux.vnet.ibm.com>
> > Cc: dledford@...hat.com
> > Cc: Jes.Sorensen@...hat.com
> > Cc: Venkat Venkatsubra <venkat.x.venkatsubra@...cle.com>
> > Cc: rds-devel@....oracle.com
> > ---
> >  net/rds/ib.h |    3 +--
> >  1 files changed, 1 insertions(+), 2 deletions(-)
> > 
> > diff --git a/net/rds/ib.h b/net/rds/ib.h
> > index edfaaaf..8d2b3d5 100644
> > --- a/net/rds/ib.h
> > +++ b/net/rds/ib.h
> > @@ -186,8 +186,7 @@ struct rds_ib_device {
> >  	struct work_struct	free_work;
> >  };
> >  
> > -#define pcidev_to_node(pcidev) pcibus_to_node(pcidev->bus)
> > -#define ibdev_to_node(ibdev) pcidev_to_node(to_pci_dev(ibdev->dma_device))
> > +#define ibdev_to_node(ibdev) dev_to_node(ibdev->dma_device)
> >  #define rdsibdev_to_node(rdsibdev) ibdev_to_node(rdsibdev->dev)
> >  
> >  /* bits for i_ack_flags */
> > -- 
> > 1.7.4.4
> > 
> 
> On Thu, Jan 05, 2012 at 08:56:34AM -0800, Venkat Venkatsubra wrote:
> > Hi Cascardo,
> > 
> > Your changes look good to me.
> > But our latest code doesn't use this rdsibdev_to_node macro anywhere.
> > Checking with the people in my group who know the history of the NUMA feature.
> > Trying to find out if the call to kzalloc_node() can be replaced by kzalloc().
> > In which case this macro can be removed.
> > 
> > I will keep you posted.
> > 
> > Venkat
> > 
> 
> Hi, Venkat.
> 
> Do you have any public tree where we can track the last changes in RDS?
> Note that I have changed ibsdev_to_node, which rdsibdev_to_node makes
> use of. Anyway, replacing kzalloc_node with kzalloc has crossed my mind,
> but since I was not sure if this would affect latency of RDS in any use
> cases, I kept that and used a better function to get the node from the
> device. And we have dev_to_node since 2.6.20, so it should not be a
> problem to use it.
> 
> If possible, keep everyone copied and avoid top posting.
> 
> Regards.
> Cascardo.

Just to make it clean, ibdev_to_node is used in Linus' tree and
next/master as of today and this patch fixes a real oops. I should have
probably added the stack trace in the log message. For completion, here
it is, running 3.2.0-rc7-00039-g89307ba:

NET: Registered protocol family 21
Registered RDS/iwarp transport
Unable to handle kernel paging request for data at address 0x00000088
Faulting instruction address: 0xc0000000000336d0
cpu 0x6: Vector: 300 (Data Access) at [c0000000ddd837e0]
    pc: c0000000000336d0: .pcibus_to_node+0x0/0x10
    lr: d000000004590de0: .rds_ib_add_one+0x100/0x360 [rds_rdma]
    sp: c0000000ddd83a60
   msr: 8000000000009032
   dar: 88
 dsisr: 40000000
  current = 0xc0000000ee6c0000
  paca    = 0xc000000006c32d00
    pid   = 8574, comm = modprobe
enter ? for help
[link register   ] d000000004590de0 .rds_ib_add_one+0x100/0x360
[rds_rdma]
[c0000000ddd83a60] d000000004590d88 .rds_ib_add_one+0xa8/0x360
[rds_rdma] (unreliable)
[c0000000ddd83b10] d000000003195240 .ib_register_client+0xc0/0x120
[ib_core]
[c0000000ddd83bb0] d00000000459074c .rds_ib_init+0x2c/0xf0 [rds_rdma]
[c0000000ddd83c30] d000000004590144 .rds_rdma_init+0xe4/0x180 [rds_rdma]
[c0000000ddd83cd0] c00000000000aa54 .do_one_initcall+0x64/0x1e0
[c0000000ddd83d90] c0000000000d359c .SyS_init_module+0xcc/0x220
[c0000000ddd83e30] c0000000000097e4 syscall_exit+0x0/0x40
--- Exception: c00 (System Call) at 00000fff7dc3d3d8
SP (fffe87eeeb0) is in userspace

Regards.
Cascardo.

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