linux-kernel - [PATCH -next] cgroup: switch to css_is

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Message-Id: <20251202025747.1658159-1-chenridong@huaweicloud.com>
Date: Tue,  2 Dec 2025 02:57:47 +0000
From: Chen Ridong <chenridong@...weicloud.com>
To: viro@...iv.linux.org.uk,
	brauner@...nel.org,
	jack@...e.cz,
	hannes@...xchg.org,
	mhocko@...nel.org,
	roman.gushchin@...ux.dev,
	shakeel.butt@...ux.dev,
	muchun.song@...ux.dev,
	tj@...nel.org,
	mkoutny@...e.com,
	akpm@...ux-foundation.org,
	vbabka@...e.cz,
	surenb@...gle.com,
	jackmanb@...gle.com,
	ziy@...dia.com
Cc: linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	cgroups@...r.kernel.org,
	linux-mm@...ck.org,
	lujialin4@...wei.com,
	chenridong@...wei.com
Subject: [PATCH -next] cgroup: switch to css_is_online() helper

From: Chen Ridong <chenridong@...wei.com>

Use the new css_is_online() helper that has been introduced to check css
online state, instead of testing the CSS_ONLINE flag directly. This
improves readability and centralizes the state check logic.

No functional changes intended.

Signed-off-by: Chen Ridong <chenridong@...wei.com>
---
 fs/fs-writeback.c          | 2 +-
 include/linux/memcontrol.h | 2 +-
 kernel/cgroup/cgroup.c     | 4 ++--
 mm/memcontrol.c            | 2 +-
 mm/page_owner.c            | 2 +-
 5 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 6800886c4d10..5dd6e89a6d29 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -981,7 +981,7 @@ void wbc_account_cgroup_owner(struct writeback_control *wbc, struct folio *folio
 
 	css = mem_cgroup_css_from_folio(folio);
 	/* dead cgroups shouldn't contribute to inode ownership arbitration */
-	if (!(css->flags & CSS_ONLINE))
+	if (!css_is_online(css))
 		return;
 
 	id = css->id;
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 0651865a4564..6a48398a1f4e 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -893,7 +893,7 @@ static inline bool mem_cgroup_online(struct mem_cgroup *memcg)
 {
 	if (mem_cgroup_disabled())
 		return true;
-	return !!(memcg->css.flags & CSS_ONLINE);
+	return css_is_online(&memcg->css);
 }
 
 void mem_cgroup_update_lru_size(struct lruvec *lruvec, enum lru_list lru,
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 1e4033d05c29..ad0a35721dff 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4939,7 +4939,7 @@ bool css_has_online_children(struct cgroup_subsys_state *css)
 
 	rcu_read_lock();
 	css_for_each_child(child, css) {
-		if (child->flags & CSS_ONLINE) {
+		if (css_is_online(child)) {
 			ret = true;
 			break;
 		}
@@ -5744,7 +5744,7 @@ static void offline_css(struct cgroup_subsys_state *css)
 
 	lockdep_assert_held(&cgroup_mutex);
 
-	if (!(css->flags & CSS_ONLINE))
+	if (!css_is_online(css))
 		return;
 
 	if (ss->css_offline)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index be810c1fbfc3..e2e49f4ec9e0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -281,7 +281,7 @@ ino_t page_cgroup_ino(struct page *page)
 	/* page_folio() is racy here, but the entire function is racy anyway */
 	memcg = folio_memcg_check(page_folio(page));
 
-	while (memcg && !(memcg->css.flags & CSS_ONLINE))
+	while (memcg && !css_is_online(&memcg->css))
 		memcg = parent_mem_cgroup(memcg);
 	if (memcg)
 		ino = cgroup_ino(memcg->css.cgroup);
diff --git a/mm/page_owner.c b/mm/page_owner.c
index a70245684206..27d19f01009c 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -530,7 +530,7 @@ static inline int print_page_owner_memcg(char *kbuf, size_t count, int ret,
 	if (!memcg)
 		goto out_unlock;
 
-	online = (memcg->css.flags & CSS_ONLINE);
+	online = css_is_online(&memcg->css);
 	cgroup_name(memcg->css.cgroup, name, sizeof(name));
 	ret += scnprintf(kbuf + ret, count - ret,
 			"Charged %sto %smemcg %s\n",
-- 
2.34.1