linux-kernel - [PATCH -next 5/5] mm/mglru: factor lrugen state out of shrink

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Message-Id: <20251209012557.1949239-6-chenridong@huaweicloud.com>
Date: Tue,  9 Dec 2025 01:25:57 +0000
From: Chen Ridong <chenridong@...weicloud.com>
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Subject: [PATCH -next 5/5] mm/mglru: factor lrugen state out of shrink_lruvec

From: Chen Ridong <chenridong@...wei.com>

A previous patch updated shrink_node_memcgs to handle lrugen root reclaim
and extended shrink_one to support both lrugen and non-lrugen. However,
in shrink_one, lrugen non-root reclaim still invokes shrink_lruvec, which
should only be used for non-lrugen reclaim.

To clarify the semantics, this patch moves the lrugen-specific logic out of
shrink_lruvec, leaving shrink_lruvec exclusively for non-lrugen reclaim.

Now for lrugen, shrink_one invokes lru_gen_shrink_lruvec, which calls
try_to_shrink_lruvec directly, without extra handling for root reclaim, as
that processing is already done in lru_gen_shrink_node. Non-root reclaim
behavior remains unchanged.

Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
 mm/vmscan.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index dbf2cfbe3243..c5f517ec52a7 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4762,7 +4762,12 @@ static void lru_gen_shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc
 {
 	struct blk_plug plug;
 
-	VM_WARN_ON_ONCE(root_reclaim(sc));
+	/* Root reclaim has finished other extra work outside, just shrink. */
+	if (root_reclaim(sc)) {
+		try_to_shrink_lruvec(lruvec, sc);
+		return;
+	}
+
 	VM_WARN_ON_ONCE(!sc->may_writepage || !sc->may_unmap);
 
 	lru_add_drain();
@@ -5524,11 +5529,6 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc)
 	bool proportional_reclaim;
 	struct blk_plug plug;
 
-	if (lru_gen_enabled() && !root_reclaim(sc)) {
-		lru_gen_shrink_lruvec(lruvec, sc);
-		return;
-	}
-
 	get_scan_count(lruvec, sc, nr);
 
 	/* Record the original scan target for proportional adjustments later */
@@ -5708,8 +5708,8 @@ static void shrink_one(struct lruvec *lruvec, struct scan_control *sc)
 	struct pglist_data *pgdat = lruvec_pgdat(lruvec);
 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
 
-	if (lru_gen_enabled() && root_reclaim(sc))
-		try_to_shrink_lruvec(lruvec, sc);
+	if (lru_gen_enabled())
+		lru_gen_shrink_lruvec(lruvec, sc);
 	else
 		shrink_lruvec(lruvec, sc);
 
-- 
2.34.1