Re: [PATCH 2/2] nvdimm: Set device node in nd_device_register

From: Dan Williams
Date: Tue Sep 25 2018 - 17:33:14 EST


On Tue, Sep 25, 2018 at 2:11 PM Alexander Duyck
<alexander.h.duyck@xxxxxxxxxxxxxxx> wrote:
>
>
>
> On 9/25/2018 2:08 PM, Dan Williams wrote:
> > On Tue, Sep 25, 2018 at 1:56 PM Alexander Duyck
> > <alexander.h.duyck@xxxxxxxxxxxxxxx> wrote:
> >>
> >> This change makes it so that we don't repeatedly overwrite the device node
> >> for nvdimm regions. The earliest we can set the node is immediately after
> >> calling device init, so I have moved the code there so we can avoid
> >> rewriting the node with each uevent.
> >>
> >> Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
> >> ---
> >> drivers/nvdimm/bus.c | 16 ++++++++++------
> >> 1 file changed, 10 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
> >> index 9148015ed803..96f4d0e1706a 100644
> >> --- a/drivers/nvdimm/bus.c
> >> +++ b/drivers/nvdimm/bus.c
> >> @@ -54,12 +54,6 @@ static int to_nd_device_type(struct device *dev)
> >>
> >> static int nvdimm_bus_uevent(struct device *dev, struct kobj_uevent_env *env)
> >> {
> >> - /*
> >> - * Ensure that region devices always have their numa node set as
> >> - * early as possible.
> >> - */
> >> - if (is_nd_region(dev))
> >> - set_dev_node(dev, to_nd_region(dev)->numa_node);
> >> return add_uevent_var(env, "MODALIAS=" ND_DEVICE_MODALIAS_FMT,
> >> to_nd_device_type(dev));
> >> }
> >> @@ -519,6 +513,16 @@ void __nd_device_register(struct device *dev)
> >> void nd_device_register(struct device *dev)
> >> {
> >> device_initialize(dev);
> >> +
> >> + /*
> >> + * Ensure that region devices always have their NUMA node set as
> >> + * early as possible. This way we are able to make certain that any
> >> + * memory associated with the creation and the creation itself of
> >> + * the region is associated with the correct node.
> >> + */
> >> + if (is_nd_region(dev))
> >> + set_dev_node(dev, to_nd_region(dev)->numa_node);
> >> +
> >> __nd_device_register(dev);
> >
> > Any reason to not put this inside __nd_device_register()? If you're ok
> > with that I can just fix up when applying.
>
> I put it here since regions never call __nd_device_register directly,
> they always call nd_device_register. I figured that by placing it here
> we reduce the impact of this on the other devices that aren't going to
> need it.

I can't imagine there's much of an impact because we're already
reading the cacheline that has dev->parent so dev->type is already
there. If we're going to add support for looking up the parent node to
schedule namespace registration work to the proper core I would expect
that to appear in the __nd_device_register() common code as well.

In general the only consideration for calling nd_device_register() vs
__nd_device_register() is whether or not you want a
device_initialize() to occur.