+ mm-page_alloc-let-the-highest-memory-node-recover-from-hopeless-state.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/page_alloc: let the highest memory node recover from hopeless state
has been added to the -mm mm-unstable branch.  Its filename is
     mm-page_alloc-let-the-highest-memory-node-recover-from-hopeless-state.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-page_alloc-let-the-highest-memory-node-recover-from-hopeless-state.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Gregory Price (Meta)" <gourry@gourry.net>
Subject: mm/page_alloc: let the highest memory node recover from hopeless state
Date: Mon, 19 Oct 2026 14:48:50 -0400

free_frozen_page_commit() clears a hopeless node's kswapd failures once
its zone recovers above the high watermark, but only if another memory
node exists for allocations to fall back to.

The test `next_memory_node(nid) < MAX_NUMNODES` finds only memory nodes
with a higher id.  The highest-numbered memory node therefore never
recovers on this path, and its kswapd stays disabled until reclaim on that
node makes progress and balances it, or demotion is re-enabled.

In many cases, direct reclaim many never fully run against a lower node
(CXL/kmem), and that means its kswapd can end up full disabled in rare
situations.

To reproduce, fill the highest memory node with bound, non-THP anonymous
memory and no swap until kswapd gives up, then free it: /proc/zoneinfo
keeps showing node_unreclaimable 1 for that node.  A lower node recovers.

Count the memory nodes instead.  Adding first_memory_node != nid to the
existing test would also work, but a count says directly what the check
means: some other memory node exists.

Link: https://lore.kernel.org/20261019184850.3427905-1-gourry@gourry.net
Fixes: e7a5f249e6db ("mm: re-enable kswapd when memory pressure subsides or demotion is toggled")
Signed-off-by: Gregory Price (Meta) <gourry@gourry.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Zi Yan <ziy@nvidia.com>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Brendan Jackman <brendan.jackman@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Chanwon Park <flyinrm@gmail.com>
Cc: <stable@vger.kernel.org>
---

 mm/page_alloc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/page_alloc.c~mm-page_alloc-let-the-highest-memory-node-recover-from-hopeless-state
+++ a/mm/page_alloc.c
@@ -2929,7 +2929,7 @@ static bool free_frozen_page_commit(stru
 		 * kswapd work again by resetting kswapd_failures.
 		 */
 		if (kswapd_test_hopeless(pgdat) &&
-		    next_memory_node(pgdat->node_id) < MAX_NUMNODES)
+		    num_node_state(N_MEMORY) > 1)
 			kswapd_clear_hopeless(pgdat, KSWAPD_CLEAR_HOPELESS_PCP);
 	}
 	return ret;
_

Patches currently in -mm which might be from gourry@gourry.net are

mm-damon-use-damon_get_monitor_folio-for-hugetlb-entries.patch
mm-vmscan-reclaim-every-zone-in-per-node-proactive-reclaim.patch
mm-mempolicy-apply-bind-policies-against-the-scoped-allocation-zone.patch
mm-page_alloc-let-the-highest-memory-node-recover-from-hopeless-state.patch