mm: vmscan: prepare for reparenting traditional LRU folios

To resolve the dying memcg issue, we need to reparent LRU folios of child
memcg to its parent memcg.  For traditional LRU list, each lruvec of every
memcg comprises four LRU lists.  Due to the symmetry of the LRU lists, it
is feasible to transfer the LRU lists from a memcg to its parent memcg
during the reparenting process.

This commit implements the specific function, which will be used during
the reparenting process.

Link: https://lore.kernel.org/a92d217a9fc82bd0c401210204a095caaf615b1c.1772711148.git.zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Muchun Song <muchun.song@linux.dev>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Allen Pais <apais@linux.microsoft.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Chen Ridong <chenridong@huawei.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Imran Khan <imran.f.khan@oracle.com>
Cc: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <Liam.Howlett@oracle.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Usama Arif <usamaarif642@gmail.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yosry Ahmed <yosry@kernel.org>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/include/linux/swap.h b/include/linux/swap.h
index ea08e2afa2b4..d653fe050b8f 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -546,6 +546,8 @@ static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
 
 	return READ_ONCE(memcg->swappiness);
 }
+
+void lru_reparent_memcg(struct mem_cgroup *memcg, struct mem_cgroup *parent, int nid);
 #else
 static inline int mem_cgroup_swappiness(struct mem_cgroup *mem)
 {
@@ -610,5 +612,24 @@ static inline bool mem_cgroup_swap_full(struct folio *folio)
 }
 #endif
 
+/* for_each_managed_zone_pgdat - helper macro to iterate over all managed zones in a pgdat up to
+ * and including the specified highidx
+ * @zone: The current zone in the iterator
+ * @pgdat: The pgdat which node_zones are being iterated
+ * @idx: The index variable
+ * @highidx: The index of the highest zone to return
+ *
+ * This macro iterates through all managed zones up to and including the specified highidx.
+ * The zone iterator enters an invalid state after macro call and must be reinitialized
+ * before it can be used again.
+ */
+#define for_each_managed_zone_pgdat(zone, pgdat, idx, highidx)	\
+	for ((idx) = 0, (zone) = (pgdat)->node_zones;		\
+	    (idx) <= (highidx);					\
+	    (idx)++, (zone)++)					\
+		if (!managed_zone(zone))			\
+			continue;				\
+		else
+
 #endif /* __KERNEL__*/
 #endif /* _LINUX_SWAP_H */