linux-kernel - Re: [PATCH v8 2/3] mm/memory hotplug/unplug: Add online_memory_block_pages() and offline_memory_block

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Message-ID: <aXhiJFvEKFk1Flpb@kernel.org>
Date: Tue, 27 Jan 2026 08:58:44 +0200
From: Mike Rapoport <rppt@...nel.org>
To: "Li, Tianyou" <tianyou.li@...el.com>
Cc: David Hildenbrand <david@...nel.org>,
	Oscar Salvador <osalvador@...e.de>,
	Wei Yang <richard.weiyang@...il.com>,
	Michal Hocko <mhocko@...e.com>, linux-mm@...ck.org,
	Yong Hu <yong.hu@...el.com>, Nanhai Zou <nanhai.zou@...el.com>,
	Yuan Liu <yuan1.liu@...el.com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Qiuxu Zhuo <qiuxu.zhuo@...el.com>, Yu C Chen <yu.c.chen@...el.com>,
	Pan Deng <pan.deng@...el.com>, Chen Zhang <zhangchen.kidd@...com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 2/3] mm/memory hotplug/unplug: Add
 online_memory_block_pages() and offline_memory_block_pages()

On Sat, Jan 24, 2026 at 08:30:57PM +0800, Li, Tianyou wrote:
> 
> On 1/22/2026 7:32 PM, Mike Rapoport wrote:

> > > diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> > > index 751f248ca4a8..ea4d6fbf34fd 100644
> > > --- a/drivers/base/memory.c
> > > +++ b/drivers/base/memory.c
> > > @@ -246,31 +246,12 @@ static int memory_block_online(struct memory_block *mem)
> > >   		nr_vmemmap_pages = mem->altmap->free;
> > >   	mem_hotplug_begin();
> > > -	if (nr_vmemmap_pages) {
> > > -		ret = mhp_init_memmap_on_memory(start_pfn, nr_vmemmap_pages, zone);
> > > -		if (ret)
> > > -			goto out;
> > > -	}
> > > -
> > > -	ret = online_pages(start_pfn + nr_vmemmap_pages,
> > > -			   nr_pages - nr_vmemmap_pages, zone, mem->group);
> > > -	if (ret) {
> > > -		if (nr_vmemmap_pages)
> > > -			mhp_deinit_memmap_on_memory(start_pfn, nr_vmemmap_pages);
> > > -		goto out;
> > > -	}
> > > -
> > > -	/*
> > > -	 * Account once onlining succeeded. If the zone was unpopulated, it is
> > > -	 * now already properly populated.
> > > -	 */
> > > -	if (nr_vmemmap_pages)
> > > -		adjust_present_page_count(pfn_to_page(start_pfn), mem->group,
> > > -					  nr_vmemmap_pages);
> > > -
> > > -	mem->zone = zone;
> > > -out:
> > > +	ret = online_memory_block_pages(start_pfn, nr_pages, nr_vmemmap_pages,
> > > +					zone, mem->group);
> > > +	if (!ret)
> > > +		mem->zone = zone;
> > I think we can move most of memory_block_online() to the new function and
> > pass struct memory_block to it.
> > I'd suggest
> > 	
> > 	int mhp_block_online(struct memory_block *block)
> > 
> > and
> > 
> > 	int mhp_block_offline(struct memory_block *block)
> > 
> > Other than that LGTM.
> 
> 
> It's doable, if not other comments I can change the code. Would it look like
> moving the functions to mm/memory_hotplug.c, change the name to
> mhp_block_online() and mhp_block_offline(), and change the references where
> the original function invoked in drivers/base/memory.c?

Yeah, that's what I thought about. 

Even more broadly, I think the functionality in drivers/base/memory.c
belongs to mm/ much more than to drivers/ but that's surely out of scope
for these patches.
 
> My prior thoughts on this was just break the code as small pieces as
> necessary to handle the pages online part together with zone contiguous
> state update.

IMHO moving the entire function is cleaner, let's hear what David and Oscar
think.

-- 
Sincerely yours,
Mike.