[PATCH] mm/vmscan: drop the combined limit gate in __node_reclaim()

[Ridong Chen <ridong.chen@linux.dev>]

From: Ridong Chen <chenridong@xiaomi.com>

__node_reclaim() is called from two paths: node_reclaim() and
user_proactive_reclaim().

node_reclaim() already bails out early unless node_pagecache_reclaimable()
is over pgdat->min_unmapped_pages or the reclaimable slab is over
pgdat->min_slab_pages.  The identical check inside __node_reclaim() that
guards the shrink_node() loop is therefore redundant for this path.

user_proactive_reclaim() is proactive reclaim driven by userspace and
should not be gated by the per-node min_unmapped_pages / min_slab_pages
limits at all [1].  With the gate in place, a proactive request is silently
turned into a no-op whenever the node happens to sit below both
thresholds.

Drop the gate in __node_reclaim() and always run the shrink_node() loop.
The node_reclaim() path is unchanged, since its caller has already applied
the same test; the proactive path is no longer wrongly gated.

[1] https://sashiko.dev/#/patchset/20260723045718.2052070-1-ridong.chen@linux.dev
Fixes: b980077899ea ("mm: introduce per-node proactive reclaim interface")
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Ridong Chen <chenridong@xiaomi.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/vmscan.c | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index f11491ee9ed5..6dff207ad8c6 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -7851,16 +7851,9 @@ static unsigned long __node_reclaim(struct pglist_data *pgdat,
 	noreclaim_flag = memalloc_noreclaim_save();
 	set_task_reclaim_state(p, &sc->reclaim_state);
 
-	if (node_pagecache_reclaimable(pgdat) > pgdat->min_unmapped_pages ||
-	    node_page_state_pages(pgdat, NR_SLAB_RECLAIMABLE_B) > pgdat->min_slab_pages) {
-		/*
-		 * Free memory by calling shrink node with increasing
-		 * priorities until we have enough memory freed.
-		 */
-		do {
-			shrink_node(pgdat, sc);
-		} while (sc->nr_reclaimed < nr_pages && --sc->priority >= 0);
-	}
+	do {
+		shrink_node(pgdat, sc);
+	} while (sc->nr_reclaimed < nr_pages && --sc->priority >= 0);
 
 	set_task_reclaim_state(p, NULL);
 	memalloc_noreclaim_restore(noreclaim_flag);
-- 
2.34.1