Re: [patch 1/4] Network namespaces: cleanup of dev_base list use

Hi Eric,

On Mon, Jun 26, 2006 at 09:13:52AM -0600, Eric W. Biederman wrote:

Andrey Savochkin [off-list ref] writes:

quoted

Cleanup of dev_base list use, with the aim to make device list per-namespace.
In almost every occasion, use of dev_base variable and dev->next pointer
could be easily replaced by for_each_netdev loop.
A few most complicated places were converted to using
first_netdev()/next_netdev().

As a proof of concept patch this is ok.

As a real world patch this is much too big, which prevents review.
Plus it takes a few actions that are more than replace just
iterators through the device list.

dev_base list is historically not the cleanest part of Linux networking.
I've still spotted a place where the first device in dev_base list is assumed
to be loopback.  In early days we had more, now only one place or two...

In addition I suspect several if not all of these iterators
can be replaced with the an appropriate helper function.

The normal structure for a patch like this would be to
introduce the new helper function.  for_each_netdev.
And then to replace all of the users while cc'ing the
maintainers of those drivers.  With each different
driver being a different patch.

There is another topic for discussion in this patch as well.
How much of the context should be implicit and how much
should be explicit.

If the changes from netchannels had already been implemented, and all of
the network processing was happening in a process context then I would
trivially agree that implicit would be the way to go.

Why would we want all network processing happen in a process context?

However short of always having code always execute in the proper
context I'm not comfortable with implicit parameters to functions.
Not that this the contents of this patch should address this but the
later patches should.

We just have too many layers in networking code, and FIB/routing
illustrates it well.

When I went through this, my patchset just added an explicit
continue if the devices was not in the appropriate namespace.
I actually prefer the multiple list implementation but at
the same time I think it is harder to get a clean implementation
out of it.

Certainly, dev_base list reorganization is not the crucial point in network
namespaces.  But it has to be done some way or other.
If people vote for a single list with skipping devices from a wrong
namespace, it's fine with me, I can re-make this patch.

I personally prefer per-namespace device list since we have too many places
in the kernel where this list is walked in a linear fashion,
and with many namespaces this list may become quite long.

Regards

Andrey