From: Shakeel Butt <shakeel.butt@linux.dev>
Date: Thu, 25 Dec 2025 23:21:13 +0000 (-0800)
Subject: mm/damon: use cgroup ID instead of private memcg ID
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5866891a7ab1348686da70f70e925964d9227bf5;p=thirdparty%2Flinux.git

mm/damon: use cgroup ID instead of private memcg ID

DAMON was using the internal private memcg ID which is meant for tracking
kernel objects that outlive their cgroup.  Switch to using the public
cgroup ID instead.

Link: https://lkml.kernel.org/r/20251225232116.294540-6-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: SeongJae Park <sj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/include/linux/damon.h b/include/linux/damon.h
index a67292a2f09dc..650e7ecfa32b8 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -203,7 +203,7 @@ struct damos_quota_goal {
 		u64 last_psi_total;
 		struct {
 			int nid;
-			unsigned short memcg_id;
+			u64 memcg_id;
 		};
 	};
 	struct list_head list;
@@ -419,7 +419,7 @@ struct damos_filter {
 	bool matching;
 	bool allow;
 	union {
-		unsigned short memcg_id;
+		u64 memcg_id;
 		struct damon_addr_range addr_range;
 		int target_idx;
 		struct damon_size_range sz_range;
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 7f0028e23f92d..3edbff685534d 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -2094,16 +2094,13 @@ static unsigned long damos_get_node_memcg_used_bp(
 	unsigned long used_pages, numerator;
 	struct sysinfo i;
 
-	rcu_read_lock();
-	memcg = mem_cgroup_from_id(goal->memcg_id);
-	if (!memcg || !mem_cgroup_tryget(memcg)) {
-		rcu_read_unlock();
+	memcg = mem_cgroup_get_from_ino(goal->memcg_id);
+	if (!memcg) {
 		if (goal->metric == DAMOS_QUOTA_NODE_MEMCG_USED_BP)
 			return 0;
 		else	/* DAMOS_QUOTA_NODE_MEMCG_FREE_BP */
 			return 10000;
 	}
-	rcu_read_unlock();
 
 	mem_cgroup_flush_stats(memcg);
 	lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(goal->nid));
diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c
index a218d99222342..dd81db95f9011 100644
--- a/mm/damon/ops-common.c
+++ b/mm/damon/ops-common.c
@@ -274,7 +274,7 @@ bool damos_folio_filter_match(struct damos_filter *filter, struct folio *folio)
 		if (!memcg)
 			matched = false;
 		else
-			matched = filter->memcg_id == mem_cgroup_id(memcg);
+			matched = filter->memcg_id == mem_cgroup_ino(memcg);
 		rcu_read_unlock();
 		break;
 	case DAMOS_FILTER_TYPE_YOUNG:
diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
index 19bc2288cd68c..6125f259eceab 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -2494,7 +2494,7 @@ static bool damon_sysfs_memcg_path_eq(struct mem_cgroup *memcg,
 	return false;
 }
 
-static int damon_sysfs_memcg_path_to_id(char *memcg_path, unsigned short *id)
+static int damon_sysfs_memcg_path_to_id(char *memcg_path, u64 *id)
 {
 	struct mem_cgroup *memcg;
 	char *path;
@@ -2509,11 +2509,11 @@ static int damon_sysfs_memcg_path_to_id(char *memcg_path, unsigned short *id)
 
 	for (memcg = mem_cgroup_iter(NULL, NULL, NULL); memcg;
 			memcg = mem_cgroup_iter(NULL, memcg, NULL)) {
-		/* skip removed memcg */
-		if (!mem_cgroup_id(memcg))
+		/* skip offlined memcg */
+		if (!mem_cgroup_online(memcg))
 			continue;
 		if (damon_sysfs_memcg_path_eq(memcg, path, memcg_path)) {
-			*id = mem_cgroup_id(memcg);
+			*id = mem_cgroup_ino(memcg);
 			found = true;
 			break;
 		}