From: Shakeel Butt <shakeel.butt@linux.dev>
Date: Fri, 7 Nov 2025 23:40:41 +0000 (-0800)
Subject: mm: memcg: dump memcg protection info on oom or alloc failures
X-Git-Tag: v6.19-rc1~112^2~130
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bc8e51c05ad50a5a0b02114d3cc94d151a332595;p=thirdparty%2Fkernel%2Flinux.git

mm: memcg: dump memcg protection info on oom or alloc failures

Currently kernel dumps memory state on oom and allocation failures.  One
of the question usually raised on those dumps is why the kernel has not
reclaimed the reclaimable memory instead of triggering oom.  One potential
reason is the usage of memory protection provided by memcg.  So, let's
also dump the memory protected by the memcg in such reports to ease the
debugging.

Link: https://lkml.kernel.org/r/20251107234041.3632644-1-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 8c0f15e5978fa..966f7c1a0128f 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1764,6 +1764,7 @@ static inline void count_objcg_events(struct obj_cgroup *objcg,
 
 bool mem_cgroup_node_allowed(struct mem_cgroup *memcg, int nid);
 
+void mem_cgroup_show_protected_memory(struct mem_cgroup *memcg);
 #else
 static inline bool mem_cgroup_kmem_disabled(void)
 {
@@ -1830,6 +1831,10 @@ static inline bool mem_cgroup_node_allowed(struct mem_cgroup *memcg, int nid)
 {
 	return true;
 }
+
+static inline void mem_cgroup_show_protected_memory(struct mem_cgroup *memcg)
+{
+}
 #endif /* CONFIG_MEMCG */
 
 #if defined(CONFIG_MEMCG) && defined(CONFIG_ZSWAP)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 025da46d9959f..bfc986da3289a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5635,3 +5635,16 @@ bool mem_cgroup_node_allowed(struct mem_cgroup *memcg, int nid)
 {
 	return memcg ? cpuset_node_allowed(memcg->css.cgroup, nid) : true;
 }
+
+void mem_cgroup_show_protected_memory(struct mem_cgroup *memcg)
+{
+	if (mem_cgroup_disabled() || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
+		return;
+
+	if (!memcg)
+		memcg = root_mem_cgroup;
+
+	pr_warn("Memory cgroup min protection %lukB -- low protection %lukB",
+		K(atomic_long_read(&memcg->memory.children_min_usage)*PAGE_SIZE),
+		K(atomic_long_read(&memcg->memory.children_low_usage)*PAGE_SIZE));
+}
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index c145b0feecc1f..5eb11fbba7043 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -472,6 +472,7 @@ static void dump_header(struct oom_control *oc)
 		if (should_dump_unreclaim_slab())
 			dump_unreclaimable_slab();
 	}
+	mem_cgroup_show_protected_memory(oc->memcg);
 	if (sysctl_oom_dump_tasks)
 		dump_tasks(oc);
 }
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e4efda1158b25..26be5734253f3 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3977,6 +3977,7 @@ static void warn_alloc_show_mem(gfp_t gfp_mask, nodemask_t *nodemask)
 		filter &= ~SHOW_MEM_FILTER_NODES;
 
 	__show_mem(filter, nodemask, gfp_zone(gfp_mask));
+	mem_cgroup_show_protected_memory(NULL);
 }
 
 void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)