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

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Message-ID: <20200914081921.GA15113@linux>
Date:   Mon, 14 Sep 2020 10:19:26 +0200
From:   Oscar Salvador <osalvador@...e.de>
To:     David Hildenbrand <david@...hat.com>
Cc:     Laurent Dufour <ldufour@...ux.ibm.com>, akpm@...ux-foundation.org,
        mhocko@...nel.org, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-mm@...ck.org, "Rafael J . Wysocki" <rafael@...nel.org>,
        nathanl@...ux.ibm.com, cheloha@...ux.ibm.com,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>, linux-ia64@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH 2/3] mm: don't rely on system state to detect hot-plug
 operations

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.

> 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?

-- 
Oscar Salvador
SUSE L3