Re: [patch 10/11] net: use numa_node in net_device->dev instead of parent

(warning, adjusted CC's and added netdev mailing list)


David Miller wrote:

From: akpm@linux-foundation.org
Date: Wed, 26 Sep 2007 18:14:42 -0700

quoted

From: Yinghai Lu <redacted>

Signed-off-by: Yinghai Lu <redacted>
Cc: Christoph Lameter <redacted>
Cc: Andy Whitcroft <redacted>
Cc: Jeff Garzik <redacted>
Cc: Andi Kleen <redacted>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

I'm not applying this, I'm still not convinced it is right.

The device of netdev->dev is a network subsystem pseudo device and
it's not a real I/O device at all.  It's there for creating the
class/net/name info under sysfs for the network device.

So pulling the NUMA node information out of there is completely

Agreed.

illogical even if you do add some ugly hack to propagate the NUMA
information from the I/O device parent into the device struct the
netdev has embedded in it.

I don't think it's an ugly hack at all.  The following is the standard 
way to tell the net device your parent:

#define SET_NETDEV_DEV(net, pdev)       ((net)->dev.parent = (pdev))

so therefore reading the parent is the standard (only?) way to retrieve 
that same information.

Using IETF RFC language:  Every net driver SHOULD have an associated 
struct device via SET_NETDEV_DEV(), even if it's another pseudo-device 
in the case where the net_device is not associated with real hardware.


However, that said, the overall /system/ employed here is a hack, 
because SET_NETDEV_DEV() does not actually adjust any reference counts 
or anything, for the associated net_device or associated struct device.

Al Viro pointed out problems related to this, ISTR, when someone tried 
to convert net drivers over to using the new devres stuff.  That's why I 
haven't been merging the devres net driver conversions -- they 
exacerbate existing object lifetime-related problems.

	Jeff