Re: [PATCH v2] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug

[Hao Li <hao.li@linux.dev>]

On Mon, Mar 30, 2026 at 05:28:34PM +0900, Harry Yoo (Oracle) wrote:
> On Mon, Mar 30, 2026 at 11:57:49AM +0800, Hao Li wrote:
> > N_NORMAL_MEMORY is initialized from zone population at boot, but memory
> > hotplug currently only updates N_MEMORY. As a result, a node that gains
> > normal memory via hotplug can remain invisible to users iterating over
> > N_NORMAL_MEMORY, while a node that loses its last normal memory can stay
> > incorrectly marked as such.
> > 
> > Restore N_NORMAL_MEMORY maintenance directly in online_pages() and
> > offline_pages(). Set the bit when a node that currently lacks normal
> > memory onlines pages into a zone <= ZONE_NORMAL, and clear it when
> > offlining removes the last present pages from zones <= ZONE_NORMAL.
> > 
> > This restores the intended semantics without bringing back the old
> > status_change_nid_normal notifier plumbing which was removed in
> > 8d2882a8edb8.
> > 
> > Current users that benefit include list_lru, zswap, nfsd filecache,
> > hugetlb_cgroup, and has_normal_memory sysfs reporting.
> > 
> > Fixes: 8d2882a8edb8 ("mm,memory_hotplug: remove status_change_nid_normal and update documentation")
> 
> The Fixes: tag indeed looks correct to me.
> 
> By the way, MM needs an explicit Cc: stable@vger.kernel.org for backporting.
> 
> Since this commit was introduced in v6.17 and we have v6.18 as LTS,
> this should to be backported to v6.18.

I had gone back and forth on whether to add the Cc tag, but I'm happy to
include it now!

> 
> > Signed-off-by: Hao Li <hao.li@linux.dev>
> > ---
> 
> Otherwise looks good to me,
> Reviewed-by: Harry Yoo (Oracle) <harry@kernel.org>

Thanks for the review!

-- 
Thanks,
Hao