Re: [PATCH 2/3] mm: don't rely on system state to detect hot-plug operations

[Laurent Dufour]

Le 14/09/2020 à 10:19, Oscar Salvador a écrit :
> On Mon, Sep 14, 2020 at 09:57:46AM +0200, David Hildenbrand wrote:
> > >   /* register memory section under specified node if it spans that node */
> > > +struct rmsun_args {
> > > +	int nid;
> > > +	enum memplug_context context;
> > > +};
>
> Uhmf, that is a not so descriptive name.

I do agree, but didn't have a better idea.
Anyway this will disappear since the choosen direction is to have 2 callbacks.

> > Instead of handling this in register_mem_sect_under_node(), I
> > think it would be better two have two separate
> > register_mem_sect_under_node() implementations.
> >
> > static int register_mem_sect_under_node_hotplug(struct memory_block *mem_blk,
> > 						void *arg)
> > {
> > 	const int nid = *(int *)arg;
> > 	int ret;
> >
> > 	/* Hotplugged memory has no holes and belongs to a single node. */
> > 	mem_blk->nid = nid;
> > 	ret = sysfs_create_link_nowarn(&node_devices[nid]->dev.kobj,
> > 				       &mem_blk->dev.kobj,
> > 				       kobject_name(&mem_blk->dev.kobj));
> > 	if (ret)
> > 		returnr et;
> > 	return sysfs_create_link_nowarn(&mem_blk->dev.kobj,
> > 					&node_devices[nid]->dev.kobj,
> > 					kobject_name(&node_devices[nid]->dev.kobj));
> >
> > }
> >
> > Cleaner, right? :) No unnecessary checks.
>
> I tend to agree here, I like more a simplistic version for hotplug.
>
> > One could argue if link_mem_section_hotplug() would be better than passing around the context.
>
> I am not sure if I would duplicate the code there.
> We could just pass the pointer of the function we want to call to
> link_mem_sections? either register_mem_sect_under_node_hotplug or
> register_mem_sect_under_node_early?
> Would not that be clean and clear enough?

That would expose the register_mem_sect_under_node*() prototype to the caller.

I'm wondering if that would be cleaner than passing a MEMPLUG_* constant value 
to link_mem_sections() and let it choose the right callback.