linux-kernel - [PATCH 5/8] mm/damon: use cgroup ID instead of private memcg ID

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Message-ID: <20251225232116.294540-6-shakeel.butt@linux.dev>
Date: Thu, 25 Dec 2025 15:21:13 -0800
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Muchun Song <muchun.song@...ux.dev>,
	SeongJae Park <sj@...nel.org>,
	Meta kernel team <kernel-team@...a.com>,
	linux-mm@...ck.org,
	cgroups@...r.kernel.org,
	damon@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH 5/8] 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.

Signed-off-by: Shakeel Butt <shakeel.butt@...ux.dev>
---
 include/linux/damon.h    | 4 ++--
 mm/damon/core.c          | 7 ++-----
 mm/damon/ops-common.c    | 2 +-
 mm/damon/sysfs-schemes.c | 8 ++++----
 4 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index a67292a2f09d..650e7ecfa32b 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 2d3e8006db50..23c44811ff7f 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -2065,16 +2065,13 @@ 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 a218d9922234..dd81db95f901 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 e198234f0763..79aa917ab3c0 100644
--- a/mm/damon/sysfs-schemes.c
+++ b/mm/damon/sysfs-schemes.c
@@ -2492,7 +2492,7 @@ 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;
@@ -2507,11 +2507,11 @@ 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;
 		}
-- 
2.47.3