* Re: [PATCH v2] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug
2026-03-30 3:57 [PATCH v2] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug Hao Li
@ 2026-03-30 8:28 ` Harry Yoo (Oracle)
2026-03-30 9:34 ` Hao Li
2026-03-30 12:07 ` Vlastimil Babka (SUSE)
` (2 subsequent siblings)
3 siblings, 1 reply; 10+ messages in thread
From: Harry Yoo (Oracle) @ 2026-03-30 8:28 UTC (permalink / raw)
To: Hao Li
Cc: david, osalvador, akpm, vbabka, joshua.hahnjy, linux-mm,
linux-kernel, linux-cxl
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.
> Signed-off-by: Hao Li <hao.li@linux.dev>
> ---
Otherwise looks good to me,
Reviewed-by: Harry Yoo (Oracle) <harry@kernel.org>
--
Cheers,
Harry / Hyeonggon
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH v2] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug
2026-03-30 8:28 ` Harry Yoo (Oracle)
@ 2026-03-30 9:34 ` Hao Li
2026-03-30 21:46 ` Andrew Morton
0 siblings, 1 reply; 10+ messages in thread
From: Hao Li @ 2026-03-30 9:34 UTC (permalink / raw)
To: Harry Yoo (Oracle)
Cc: david, osalvador, akpm, vbabka, joshua.hahnjy, linux-mm,
linux-kernel, linux-cxl
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
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH v2] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug
2026-03-30 9:34 ` Hao Li
@ 2026-03-30 21:46 ` Andrew Morton
2026-03-31 4:24 ` Hao Li
0 siblings, 1 reply; 10+ messages in thread
From: Andrew Morton @ 2026-03-30 21:46 UTC (permalink / raw)
To: Hao Li
Cc: Harry Yoo (Oracle),
david, osalvador, vbabka, joshua.hahnjy, linux-mm, linux-kernel,
linux-cxl
On Mon, 30 Mar 2026 17:34:21 +0800 Hao Li <hao.li@linux.dev> wrote:
> > > 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!
That's OK, I'm very cc:stable-vigilant. Thanks, I'll get this upstreamed during
this -rc cycle.
I do like our cc:stable patches to include a clear description of the
userspace-visible impacts of the bug. Two reasons:
- To explain to -stable maintainers why we're requesting the
backport. If they care. Heck, and to explain to me why I'm doing
this!
- To help out someone who is using an older kernel (there are many)
who is dealing with a bug report. They're looking at this changelog
thinking "hm, I wonder if this patch will fix that bug". Let's add a
few words in there to help out with their pattern matching.
So, and not for the first time ;), what are the userspace-visible
runtime effects of this bug?
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH v2] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug
2026-03-30 21:46 ` Andrew Morton
@ 2026-03-31 4:24 ` Hao Li
2026-03-31 5:15 ` Andrew Morton
0 siblings, 1 reply; 10+ messages in thread
From: Hao Li @ 2026-03-31 4:24 UTC (permalink / raw)
To: Andrew Morton
Cc: Harry Yoo (Oracle),
david, osalvador, vbabka, joshua.hahnjy, linux-mm, linux-kernel,
linux-cxl
On Mon, Mar 30, 2026 at 02:46:40PM -0700, Andrew Morton wrote:
> On Mon, 30 Mar 2026 17:34:21 +0800 Hao Li <hao.li@linux.dev> wrote:
>
> > > > 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!
>
> That's OK, I'm very cc:stable-vigilant. Thanks, I'll get this upstreamed during
> this -rc cycle.
Thanks!
>
> I do like our cc:stable patches to include a clear description of the
> userspace-visible impacts of the bug. Two reasons:
>
> - To explain to -stable maintainers why we're requesting the
> backport. If they care. Heck, and to explain to me why I'm doing
> this!
>
> - To help out someone who is using an older kernel (there are many)
> who is dealing with a bug report. They're looking at this changelog
> thinking "hm, I wonder if this patch will fix that bug". Let's add a
> few words in there to help out with their pattern matching.
Agreed, and thanks for spelling out the rationale!
>
> So, and not for the first time ;), what are the userspace-visible
> runtime effects of this bug?
>
The most visible effect is that
/sys/devices/system/node/has_normal_memory does not report a node even
after that node has gained normal memory via hotplug.
Also, list_lru-based shrinkers can undercount objects on such a node and
may skip reclaim on that node entirely, which can lead to a higher memory
footprint than expected.
Feel free to fold the above into the changelog if useful :)
--
Thanks,
Hao
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH v2] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug
2026-03-31 4:24 ` Hao Li
@ 2026-03-31 5:15 ` Andrew Morton
0 siblings, 0 replies; 10+ messages in thread
From: Andrew Morton @ 2026-03-31 5:15 UTC (permalink / raw)
To: Hao Li
Cc: Harry Yoo (Oracle),
david, osalvador, vbabka, joshua.hahnjy, linux-mm, linux-kernel,
linux-cxl
On Tue, 31 Mar 2026 12:24:46 +0800 Hao Li <hao.li@linux.dev> wrote:
> The most visible effect is that
> /sys/devices/system/node/has_normal_memory does not report a node even
> after that node has gained normal memory via hotplug.
>
> Also, list_lru-based shrinkers can undercount objects on such a node and
> may skip reclaim on that node entirely, which can lead to a higher memory
> footprint than expected.
>
> Feel free to fold the above into the changelog if useful :)
Very useful. Added, thanks!
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v2] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug
2026-03-30 3:57 [PATCH v2] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug Hao Li
2026-03-30 8:28 ` Harry Yoo (Oracle)
@ 2026-03-30 12:07 ` Vlastimil Babka (SUSE)
2026-03-30 13:53 ` Joshua Hahn
2026-03-30 14:20 ` David Hildenbrand (Arm)
3 siblings, 0 replies; 10+ messages in thread
From: Vlastimil Babka (SUSE) @ 2026-03-30 12:07 UTC (permalink / raw)
To: Hao Li, david, osalvador, akpm
Cc: vbabka, harry.yoo, joshua.hahnjy, linux-mm, linux-kernel, linux-cxl
On 3/30/26 05:57, 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")
> Signed-off-by: Hao Li <hao.li@linux.dev>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Thanks!
> ---
> Changes: simplify the code. (Thanks Joshua and David)
> ---
> mm/memory_hotplug.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index bc805029da51..05a47953ef21 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1209,6 +1209,13 @@ int online_pages(unsigned long pfn, unsigned long nr_pages,
>
> if (node_arg.nid >= 0)
> node_set_state(nid, N_MEMORY);
> + /*
> + * Check whether we are adding normal memory to the node for the first
> + * time.
> + */
> + if (!node_state(nid, N_NORMAL_MEMORY) && zone_idx(zone) <= ZONE_NORMAL)
> + node_set_state(nid, N_NORMAL_MEMORY);
> +
> if (need_zonelists_rebuild)
> build_all_zonelists(NULL);
>
> @@ -1908,6 +1915,8 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages,
> unsigned long flags;
> char *reason;
> int ret;
> + unsigned long normal_pages = 0;
> + enum zone_type zt;
>
> /*
> * {on,off}lining is constrained to full memory sections (or more
> @@ -2055,6 +2064,17 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages,
> /* reinitialise watermarks and update pcp limits */
> init_per_zone_wmark_min();
>
> + /*
> + * Check whether this operation removes the last normal memory from
> + * the node. We do this before clearing N_MEMORY to avoid the possible
> + * transient "!N_MEMORY && N_NORMAL_MEMORY" state.
> + */
> + if (zone_idx(zone) <= ZONE_NORMAL) {
> + for (zt = 0; zt <= ZONE_NORMAL; zt++)
> + normal_pages += pgdat->node_zones[zt].present_pages;
> + if (!normal_pages)
> + node_clear_state(node, N_NORMAL_MEMORY);
> + }
> /*
> * Make sure to mark the node as memory-less before rebuilding the zone
> * list. Otherwise this node would still appear in the fallback lists.
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH v2] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug
2026-03-30 3:57 [PATCH v2] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug Hao Li
2026-03-30 8:28 ` Harry Yoo (Oracle)
2026-03-30 12:07 ` Vlastimil Babka (SUSE)
@ 2026-03-30 13:53 ` Joshua Hahn
2026-03-30 14:20 ` David Hildenbrand (Arm)
3 siblings, 0 replies; 10+ messages in thread
From: Joshua Hahn @ 2026-03-30 13:53 UTC (permalink / raw)
To: Hao Li
Cc: david, osalvador, akpm, vbabka, harry.yoo, joshua.hahnjy,
linux-mm, linux-kernel, linux-cxl
On Mon, 30 Mar 2026 11:57:49 +0800 Hao Li <hao.li@linux.dev> 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")
> Signed-off-by: Hao Li <hao.li@linux.dev>
LGTM, thanks for the new version Hao! I hope you have a great day : -)
Reviewed-by: Joshua Hahn <joshua.hahnjy@gmail.com>
> ---
> Changes: simplify the code. (Thanks Joshua and David)
> ---
> mm/memory_hotplug.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index bc805029da51..05a47953ef21 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH v2] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug
2026-03-30 3:57 [PATCH v2] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug Hao Li
` (2 preceding siblings ...)
2026-03-30 13:53 ` Joshua Hahn
@ 2026-03-30 14:20 ` David Hildenbrand (Arm)
2026-03-31 4:14 ` Hao Li
3 siblings, 1 reply; 10+ messages in thread
From: David Hildenbrand (Arm) @ 2026-03-30 14:20 UTC (permalink / raw)
To: Hao Li, osalvador, akpm
Cc: vbabka, harry.yoo, joshua.hahnjy, linux-mm, linux-kernel, linux-cxl
On 3/30/26 05:57, 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")
Agreed on CCing stable.
> Signed-off-by: Hao Li <hao.li@linux.dev>
> ---
> Changes: simplify the code. (Thanks Joshua and David)
> ---
> mm/memory_hotplug.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index bc805029da51..05a47953ef21 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1209,6 +1209,13 @@ int online_pages(unsigned long pfn, unsigned long nr_pages,
>
> if (node_arg.nid >= 0)
> node_set_state(nid, N_MEMORY);
> + /*
> + * Check whether we are adding normal memory to the node for the first
> + * time.
> + */
> + if (!node_state(nid, N_NORMAL_MEMORY) && zone_idx(zone) <= ZONE_NORMAL)
> + node_set_state(nid, N_NORMAL_MEMORY);
> +
> if (need_zonelists_rebuild)
> build_all_zonelists(NULL);
>
> @@ -1908,6 +1915,8 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages,
> unsigned long flags;
> char *reason;
> int ret;
> + unsigned long normal_pages = 0;
> + enum zone_type zt;
>
> /*
> * {on,off}lining is constrained to full memory sections (or more
> @@ -2055,6 +2064,17 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages,
> /* reinitialise watermarks and update pcp limits */
> init_per_zone_wmark_min();
>
> + /*
> + * Check whether this operation removes the last normal memory from
> + * the node. We do this before clearing N_MEMORY to avoid the possible
> + * transient "!N_MEMORY && N_NORMAL_MEMORY" state.
> + */
> + if (zone_idx(zone) <= ZONE_NORMAL) {
> + for (zt = 0; zt <= ZONE_NORMAL; zt++)
> + normal_pages += pgdat->node_zones[zt].present_pages;
> + if (!normal_pages)
> + node_clear_state(node, N_NORMAL_MEMORY);
> + }
Was wondering whether we could just do an early exit, like:
for (zt = 0; zt <= ZONE_NORMAL; zt++) {
if (pgdat->node_zones[zt].present_pages)
break;
}
if (zt > ZONE_NORMAL)
node_clear_state(node, N_NORMAL_MEMORY);
But ends up being harder to digest (incl. all variants I tried :) ), so
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
--
Cheers,
David
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH v2] mm/memory_hotplug: maintain N_NORMAL_MEMORY during hotplug
2026-03-30 14:20 ` David Hildenbrand (Arm)
@ 2026-03-31 4:14 ` Hao Li
0 siblings, 0 replies; 10+ messages in thread
From: Hao Li @ 2026-03-31 4:14 UTC (permalink / raw)
To: David Hildenbrand (Arm)
Cc: osalvador, akpm, vbabka, harry.yoo, joshua.hahnjy, linux-mm,
linux-kernel, linux-cxl
On Mon, Mar 30, 2026 at 04:20:23PM +0200, David Hildenbrand (Arm) wrote:
> On 3/30/26 05:57, 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")
>
> Agreed on CCing stable.
>
> > Signed-off-by: Hao Li <hao.li@linux.dev>
> > ---
> > Changes: simplify the code. (Thanks Joshua and David)
> > ---
> > mm/memory_hotplug.c | 20 ++++++++++++++++++++
> > 1 file changed, 20 insertions(+)
> >
> > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > index bc805029da51..05a47953ef21 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -1209,6 +1209,13 @@ int online_pages(unsigned long pfn, unsigned long nr_pages,
> >
> > if (node_arg.nid >= 0)
> > node_set_state(nid, N_MEMORY);
> > + /*
> > + * Check whether we are adding normal memory to the node for the first
> > + * time.
> > + */
> > + if (!node_state(nid, N_NORMAL_MEMORY) && zone_idx(zone) <= ZONE_NORMAL)
> > + node_set_state(nid, N_NORMAL_MEMORY);
> > +
> > if (need_zonelists_rebuild)
> > build_all_zonelists(NULL);
> >
> > @@ -1908,6 +1915,8 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages,
> > unsigned long flags;
> > char *reason;
> > int ret;
> > + unsigned long normal_pages = 0;
> > + enum zone_type zt;
> >
> > /*
> > * {on,off}lining is constrained to full memory sections (or more
> > @@ -2055,6 +2064,17 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages,
> > /* reinitialise watermarks and update pcp limits */
> > init_per_zone_wmark_min();
> >
> > + /*
> > + * Check whether this operation removes the last normal memory from
> > + * the node. We do this before clearing N_MEMORY to avoid the possible
> > + * transient "!N_MEMORY && N_NORMAL_MEMORY" state.
> > + */
> > + if (zone_idx(zone) <= ZONE_NORMAL) {
> > + for (zt = 0; zt <= ZONE_NORMAL; zt++)
> > + normal_pages += pgdat->node_zones[zt].present_pages;
> > + if (!normal_pages)
> > + node_clear_state(node, N_NORMAL_MEMORY);
> > + }
>
> Was wondering whether we could just do an early exit, like:
>
>
> for (zt = 0; zt <= ZONE_NORMAL; zt++) {
> if (pgdat->node_zones[zt].present_pages)
> break;
> }
> if (zt > ZONE_NORMAL)
> node_clear_state(node, N_NORMAL_MEMORY);
>
> But ends up being harder to digest (incl. all variants I tried :) ), so
Thanks for exploring this.
Yeah, this looks like one of those cases where we have to make a bit of a
tradeoff for readability :)
>
> Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Thanks for the Ack!
--
Thanks,
Hao
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