[PATCH 6.18 078/227] mm: restore per-memcg proactive reclaim with !CONFIG_NUMA

Greg Kroah-Hartman
2026-01-28T15:54:26Z

From: Yosry Ahmed <yosry.ahmed@linux.dev>

commit 16aca2c98a6fdf071e5a1a765a295995d7c7e346 upstream.

Commit 2b7226af730c ("mm/memcg: make memory.reclaim interface generic")
moved proactive reclaim logic from memory.reclaim handler to a generic
user_proactive_reclaim() helper to be used for per-node proactive reclaim.

However, user_proactive_reclaim() was only defined under CONFIG_NUMA, with
a stub always returning 0 otherwise. This broke memory.reclaim on
!CONFIG_NUMA configs, causing it to report success without actually
attempting reclaim.

Move the definition of user_proactive_reclaim() outside CONFIG_NUMA, and
instead define a stub for __node_reclaim() in the !CONFIG_NUMA case.
__node_reclaim() is only called from user_proactive_reclaim() when a write
is made to sys/devices/system/node/nodeX/reclaim, which is only defined
with CONFIG_NUMA.

Link: https://lkml.kernel.org/r/20260116205247.928004-1-yosry.ahmed@linux.dev
Fixes: 2b7226af730c ("mm/memcg: make memory.reclaim interface generic")
Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/internal.h | 8 --------
mm/vmscan.c | 13 +++++++++++--
2 files changed, 11 insertions(+), 10 deletions(-)

--- a/mm/internal.h
+++ b/mm/internal.h
@@ -538,16 +538,8 @@ extern unsigned long highest_memmap_pfn;
bool folio_isolate_lru(struct folio *folio);
void folio_putback_lru(struct folio *folio);
extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason);
-#ifdef CONFIG_NUMA
int user_proactive_reclaim(char *buf,
struct mem_cgroup *memcg, pg_data_t *pgdat);
-#else
-static inline int user_proactive_reclaim(char *buf,
- struct mem_cgroup *memcg, pg_data_t *pgdat)
-{
- return 0;
-}
-#endif

/*
* in mm/rmap.c:
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -7740,6 +7740,17 @@ int node_reclaim(struct pglist_data *pgd
return ret;
}

+#else
+
+static unsigned long __node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask,
+ unsigned long nr_pages,
+ struct scan_control *sc)
+{
+ return 0;
+}
+
+#endif
+
enum {
MEMORY_RECLAIM_SWAPPINESS = 0,
MEMORY_RECLAIM_SWAPPINESS_MAX,
@@ -7847,8 +7858,6 @@ int user_proactive_reclaim(char *buf,
return 0;
}

-#endif
-
/**
* check_move_unevictable_folios - Move evictable folios to appropriate zone
* lru list