[PATCH] mm/memcontrol: remove unused for_each_mem_cgroup macro and cleanup

[PATCH] mm/memcontrol: remove unused for_each_mem_cgroup macro and cleanup

[Joshua Hahn]

Commit 7e1c0d6f58207 ("memcg: switch lruvec stats to rstat") removed the
last caller of for_each_mem_cgroup back in 2021, and there have not been
any new callers since. Remove the macro.

A comment in mem_cgroup_css_online has also been out of date since 2021,
when 2bfd36374edd9 ("mm: vmscan: consolidate shrinker_maps handling
code") open-coded the for_each_mem_cgroup iterator. Update the comment.

Finally, 99430ab8b804c ("mm: introduce BPF kfuncs to access memcg
statistics and events") added a second declaration for memcg_events to
include/linux/memcontrol.h, duplicating the one in mm/memcontrol-v1.h.
Let's clean that up too.

No functional changes intended.

Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>
---
This is intended for the next release cycle. Thank you!

 mm/memcontrol-v1.h | 6 ------
 mm/memcontrol.c    | 2 +-
 2 files changed, 1 insertion(+), 7 deletions(-)

diff --git a/mm/memcontrol-v1.h b/mm/memcontrol-v1.h
index f92f81108d5ed..d3ed5b93290fb 100644
--- a/mm/memcontrol-v1.h
+++ b/mm/memcontrol-v1.h
@@ -17,14 +17,8 @@
 	     iter != NULL;				\
 	     iter = mem_cgroup_iter(root, iter, NULL))
 
-#define for_each_mem_cgroup(iter)			\
-	for (iter = mem_cgroup_iter(NULL, NULL, NULL);	\
-	     iter != NULL;				\
-	     iter = mem_cgroup_iter(NULL, iter, NULL))
-
 void drain_all_stock(struct mem_cgroup *root_memcg);
 
-unsigned long memcg_events(struct mem_cgroup *memcg, int event);
 int memory_stat_show(struct seq_file *m, void *v);
 
 struct mem_cgroup *mem_cgroup_private_id_get_online(struct mem_cgroup *memcg,
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 56cd4af082326..e171fe36b0711 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4216,7 +4216,7 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
 	/*
 	 * A memcg must be visible for expand_shrinker_info()
 	 * by the time the maps are allocated. So, we allocate maps
-	 * here, when for_each_mem_cgroup() can't skip it.
+	 * here, when mem_cgroup_iter() can't skip it.
 	 */
 	if (alloc_shrinker_info(memcg))
 		goto offline_kmem;
-- 
2.53.0-Meta

Re: [PATCH] mm/memcontrol: remove unused for_each_mem_cgroup macro and cleanup

[Shakeel Butt]

On Wed, Jun 24, 2026 at 11:36:59AM -0700, Joshua Hahn wrote:
> Commit 7e1c0d6f58207 ("memcg: switch lruvec stats to rstat") removed the
> last caller of for_each_mem_cgroup back in 2021, and there have not been
> any new callers since. Remove the macro.
> 
> A comment in mem_cgroup_css_online has also been out of date since 2021,
> when 2bfd36374edd9 ("mm: vmscan: consolidate shrinker_maps handling
> code") open-coded the for_each_mem_cgroup iterator. Update the comment.
> 
> Finally, 99430ab8b804c ("mm: introduce BPF kfuncs to access memcg
> statistics and events") added a second declaration for memcg_events to
> include/linux/memcontrol.h, duplicating the one in mm/memcontrol-v1.h.
> Let's clean that up too.
> 
> No functional changes intended.
> 
> Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>

Thanks for the cleanup.

Acked-by: Shakeel Butt <shakeel.butt@linux.dev>