linux-kernel - Re: [PATCH v5 3/3] mm/mempolicy: Support memory hotplug in weighted interleave

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Message-ID: <Z-1GUrdcOeYQgkE3@gourry-fedora-PF4VCD3F>
Date: Wed, 2 Apr 2025 10:14:42 -0400
From: Gregory Price <gourry@...rry.net>
To: Oscar Salvador <osalvador@...e.de>
Cc: Rakie Kim <rakie.kim@...com>, akpm@...ux-foundation.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linux-cxl@...r.kernel.org, joshua.hahnjy@...il.com,
	dan.j.williams@...el.com, ying.huang@...ux.alibaba.com,
	david@...hat.com, Jonathan.Cameron@...wei.com,
	kernel_team@...ynix.com, honggyu.kim@...com, yunjeong.mun@...com
Subject: Re: [PATCH v5 3/3] mm/mempolicy: Support memory hotplug in weighted
 interleave

On Wed, Apr 02, 2025 at 11:51:17AM +0200, Oscar Salvador wrote:
> > +	case MEM_OFFLINE:
> > +		if (!node_state(nid, N_MEMORY))
> > +			sysfs_wi_node_release(nid);
> 
> This check is not needed.
> 
> If status_change_nid is different than NUMA_NO_NODE, it means that the memory
> state of the numa node was effectively changed.
> So doing:
>  
>   case MEM_OFFLINE:
>           sysfs_wi_node_release(nid)
>  
> is enough.

offline_pages will call this callback unconditionally any time it's
called (and succeeds).  If 2 dax devices online into the same node, it's
possible to offline one chunk of blocks without offlining the other
chunks of blocks - which is why we did the additional check.

~Gregory