Re: [PATCH 2/7] sysfs: make attr namespace interface less convoluted

David Miller
2013-09-12T19:46:32Z

From: Tejun Heo <tj@kernel.org>
Date: Wed, 11 Sep 2013 22:29:04 -0400

> sysfs ns (namespace) implementation became more convoluted than
> necessary while trying to hide ns information from visible interface.
> The relatively recent attr ns support is a good example.
>
> * attr ns tag is determined by sysfs_ops->namespace() callback while
> dir tag is determined by kobj_type->namespace(). The placement is
> arbitrary.
>
> * Instead of performing operations with explicit ns tag, the namespace
> callback is routed through sysfs_attr_ns(), sysfs_ops->namespace(),
> class_attr_namespace(), class_attr->namespace(). It's not simpler
> in any sense. The only thing this convolution does is traversing
> the whole stack backwards.
>
> The namespace callbacks are unncessary because the operations involved
> are inherently synchronous. The information can be provided in in
> straight-forward top-down direction and reversing that direction is
> unnecessary and against basic design principles.
>
> This backward interface is unnecessarily convoluted and hinders
> properly separating out sysfs from driver model / kobject for proper
> layering. This patch updates attr ns support such that
>
> * sysfs_ops->namespace() and class_attr->namespace() are dropped.
>
> * sysfs_{create|remove}_file_ns(), which take explicit @ns param, are
> added and sysfs_{create|remove}_file() are now simple wrappers
> around the ns aware functions.
>
> * ns handling is dropped from sysfs_chmod_file(). Nobody uses it at
> this point. sysfs_chmod_file_ns() can be added later if necessary.
>
> * Explicit @ns is propagated through class_{create|remove}_file_ns()
> and netdev_class_{create|remove}_file_ns().
>
> * driver/net/bonding which is currently the only user of attr
> namespace is updated to use netdev_class_{create|remove}_file_ns()
> with @bh->net as the ns tag instead of using the namespace callback.
>
> This patch should be an equivalent conversion without any functional
> difference. It makes the code easier to follow, reduces lines of code
> a bit and helps proper separation and layering.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>

For networking bits:

Acked-by: David S. Miller <davem@davemloft.net>