linux-kernel - [PATCH v1] mm/vmscan: fix uninitialized variable in demote_folio

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Message-ID: <20260109060622.3742262-1-bingjiao@google.com>
Date: Fri,  9 Jan 2026 06:06:21 +0000
From: Bing Jiao <bingjiao@...gle.com>
To: linux-mm@...ck.org
Cc: Bing Jiao <bingjiao@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Axel Rasmussen <axelrasmussen@...gle.com>, Yuanchu Xie <yuanchu@...gle.com>, 
	Wei Xu <weixugc@...gle.com>, Johannes Weiner <hannes@...xchg.org>, 
	David Hildenbrand <david@...nel.org>, Michal Hocko <mhocko@...nel.org>, 
	Qi Zheng <zhengqi.arch@...edance.com>, Shakeel Butt <shakeel.butt@...ux.dev>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, linux-kernel@...r.kernel.org
Subject: [PATCH v1] mm/vmscan: fix uninitialized variable in demote_folio_list()

Commit d92027a5f30a6c ("mm/vmscan: select the closest preferred node in
demote_folio_list()") refactored the selection logic for demotion target
nodes. However, it removed the initial assignment of 'target_nid' while
leaving a premature check for 'NUMA_NO_NODE' in place.

Since 'target_nid' is now assigned further down in the function based on
preferred and allowed node masks, the initial check at line 1046 is
redundant.

Remove the redundant check to resolve the compiler warning.

Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202601091037.vUSHeJCH-lkp@intel.com/
Fixes: d92027a5f30a6c ("mm/vmscan: select the closest preferred node in demote_folio_list()")
Signed-off-by: Bing Jiao <bingjiao@...gle.com>
---
 mm/vmscan.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 213ee75b3306..590ab3ec1998 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1044,10 +1044,6 @@ static unsigned int demote_folio_list(struct list_head *demote_folios,
 	if (list_empty(demote_folios))
 		return 0;

-	if (target_nid == NUMA_NO_NODE)
-		/* No lower-tier nodes or nodes were hot-unplugged. */
-		return 0;
-
 	node_get_allowed_targets(pgdat, &allowed_mask);
 	mem_cgroup_node_filter_allowed(memcg, &allowed_mask);
 	if (nodes_empty(allowed_mask))
--
2.52.0.457.g6b5491de43-goog