diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
index 76fbf92b04d958c5d5ba23226c3651044d0e4fac..2ced8149c51371027fe7fe37480608aa9b26710e 100644
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -72,6 +72,10 @@ struct shrinker {
#ifdef CONFIG_MEMCG
/* ID in shrinker_idr */
int id;
+#endif
+#ifdef CONFIG_SHRINKER_DEBUG
+ int debugfs_id;
+ struct dentry *debugfs_entry;
#endif
/* objs pending delete, per node */
atomic_long_t *nr_deferred;
@@ -94,4 +98,17 @@ extern int register_shrinker(struct shrinker *shrinker);
extern void unregister_shrinker(struct shrinker *shrinker);
extern void free_prealloced_shrinker(struct shrinker *shrinker);
extern void synchronize_shrinkers(void);
-#endif
+
+#ifdef CONFIG_SHRINKER_DEBUG
+extern int shrinker_debugfs_add(struct shrinker *shrinker);
+extern void shrinker_debugfs_remove(struct shrinker *shrinker);
+#else /* CONFIG_SHRINKER_DEBUG */
+static inline int shrinker_debugfs_add(struct shrinker *shrinker)
+{
+ return 0;
+}
+static inline void shrinker_debugfs_remove(struct shrinker *shrinker)
+{
+}
+#endif /* CONFIG_SHRINKER_DEBUG */
+#endif /* _LINUX_SHRINKER_H */
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 2e24db4bff1921483ad1bd1e181d242e6cd55345..0b483a8da409d53f85a3000e72d3e72a99aa7acc 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -699,6 +699,15 @@ config DEBUG_OBJECTS_ENABLE_DEFAULT
help
Debug objects boot parameter default value
+config SHRINKER_DEBUG
+ default y
+ bool "Enable shrinker debugging support"
+ depends on DEBUG_FS
+ help
+ Say Y to enable the shrinker debugfs interface which provides
+ visibility into the kernel memory shrinkers subsystem.
+ Disable it to avoid an extra memory footprint.
+
config HAVE_DEBUG_KMEMLEAK
bool
diff --git a/mm/Makefile b/mm/Makefile
index 6f9ffa968a1a13e9e303d8e7fb1a038b4c477f40..9a564f836403597c16fe1bddafc5aa91d7e25d99 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -133,3 +133,4 @@ obj-$(CONFIG_PAGE_REPORTING) += page_reporting.o
obj-$(CONFIG_IO_MAPPING) += io-mapping.o
obj-$(CONFIG_HAVE_BOOTMEM_INFO_NODE) += bootmem_info.o
obj-$(CONFIG_GENERIC_IOREMAP) += ioremap.o
+obj-$(CONFIG_SHRINKER_DEBUG) += shrinker_debug.o
diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
new file mode 100644
index 0000000000000000000000000000000000000000..1a70556bd46cf46b6c3f0368af519249232165f2
--- /dev/null
+++ b/mm/shrinker_debug.c
@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/idr.h>
+#include <linux/slab.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <linux/shrinker.h>
+#include <linux/memcontrol.h>
+
+/* defined in vmscan.c */
+extern struct rw_semaphore shrinker_rwsem;
+extern struct list_head shrinker_list;
+
+static DEFINE_IDA(shrinker_debugfs_ida);
+static struct dentry *shrinker_debugfs_root;
+
+static unsigned long shrinker_count_objects(struct shrinker *shrinker,
+ struct mem_cgroup *memcg,
+ unsigned long *count_per_node)
+{
+ unsigned long nr, total = 0;
+ int nid;
+
+ for_each_node(nid) {
+ if (nid == 0 || (shrinker->flags & SHRINKER_NUMA_AWARE)) {
+ struct shrink_control sc = {
+ .gfp_mask = GFP_KERNEL,
+ .nid = nid,
+ .memcg = memcg,
+ };
+
+ nr = shrinker->count_objects(shrinker, &sc);
+ if (nr == SHRINK_EMPTY)
+ nr = 0;
+ } else {
+ nr = 0;
+ }
+
+ count_per_node[nid] = nr;
+ total += nr;
+ }
+
+ return total;
+}
+
+static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
+{
+ struct shrinker *shrinker = m->private;
+ unsigned long *count_per_node;
+ struct mem_cgroup *memcg;
+ unsigned long total;
+ bool memcg_aware;
+ int ret, nid;
+
+ count_per_node = kcalloc(nr_node_ids, sizeof(unsigned long), GFP_KERNEL);
+ if (!count_per_node)
+ return -ENOMEM;
+
+ ret = down_read_killable(&shrinker_rwsem);
+ if (ret) {
+ kfree(count_per_node);
+ return ret;
+ }
+ rcu_read_lock();
+
+ memcg_aware = shrinker->flags & SHRINKER_MEMCG_AWARE;
+
+ memcg = mem_cgroup_iter(NULL, NULL, NULL);
+ do {
+ if (memcg && !mem_cgroup_online(memcg))
+ continue;
+
+ total = shrinker_count_objects(shrinker,
+ memcg_aware ? memcg : NULL,
+ count_per_node);
+ if (total) {
+ seq_printf(m, "%lu", mem_cgroup_ino(memcg));
+ for_each_node(nid)
+ seq_printf(m, " %lu", count_per_node[nid]);
+ seq_putc(m, '\n');
+ }
+
+ if (!memcg_aware) {
+ mem_cgroup_iter_break(NULL, memcg);
+ break;
+ }
+
+ if (signal_pending(current)) {
+ mem_cgroup_iter_break(NULL, memcg);
+ ret = -EINTR;
+ break;
+ }
+ } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
+
+ rcu_read_unlock();
+ up_read(&shrinker_rwsem);
+
+ kfree(count_per_node);
+ return ret;
+}
+DEFINE_SHOW_ATTRIBUTE(shrinker_debugfs_count);
+
+int shrinker_debugfs_add(struct shrinker *shrinker)
+{
+ struct dentry *entry;
+ char buf[16];
+ int id;
+
+ lockdep_assert_held(&shrinker_rwsem);
+
+ /* debugfs isn't initialized yet, add debugfs entries later. */
+ if (!shrinker_debugfs_root)
+ return 0;
+
+ id = ida_alloc(&shrinker_debugfs_ida, GFP_KERNEL);
+ if (id < 0)
+ return id;
+ shrinker->debugfs_id = id;
+
+ snprintf(buf, sizeof(buf), "%d", id);
+
+ /* create debugfs entry */
+ entry = debugfs_create_dir(buf, shrinker_debugfs_root);
+ if (IS_ERR(entry)) {
+ ida_free(&shrinker_debugfs_ida, id);
+ return PTR_ERR(entry);
+ }
+ shrinker->debugfs_entry = entry;
+
+ debugfs_create_file("count", 0220, entry, shrinker,
+ &shrinker_debugfs_count_fops);
+ return 0;
+}
+
+void shrinker_debugfs_remove(struct shrinker *shrinker)
+{
+ lockdep_assert_held(&shrinker_rwsem);
+
+ if (!shrinker->debugfs_entry)
+ return;
+
+ debugfs_remove_recursive(shrinker->debugfs_entry);
+ ida_free(&shrinker_debugfs_ida, shrinker->debugfs_id);
+}
+
+static int __init shrinker_debugfs_init(void)
+{
+ struct shrinker *shrinker;
+ struct dentry *dentry;
+ int ret = 0;
+
+ dentry = debugfs_create_dir("shrinker", NULL);
+ if (IS_ERR(dentry))
+ return PTR_ERR(dentry);
+ shrinker_debugfs_root = dentry;
+
+ /* Create debugfs entries for shrinkers registered at boot */
+ down_write(&shrinker_rwsem);
+ list_for_each_entry(shrinker, &shrinker_list, list)
+ if (!shrinker->debugfs_entry) {
+ ret = shrinker_debugfs_add(shrinker);
+ if (ret)
+ break;
+ }
+ up_write(&shrinker_rwsem);
+
+ return ret;
+}
+late_initcall(shrinker_debugfs_init);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index f7d9a683e3a7d38fe1ffd0265b9f7d7acad938b4..35dedff79eb4cf6b2443da9f7a1008312f773535 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -190,8 +190,8 @@ static void set_task_reclaim_state(struct task_struct *task,
task->reclaim_state = rs;
}
-static LIST_HEAD(shrinker_list);
-static DECLARE_RWSEM(shrinker_rwsem);
+LIST_HEAD(shrinker_list);
+DECLARE_RWSEM(shrinker_rwsem);
#ifdef CONFIG_MEMCG
static int shrinker_nr_max;
@@ -650,6 +650,7 @@ void register_shrinker_prepared(struct shrinker *shrinker)
down_write(&shrinker_rwsem);
list_add_tail(&shrinker->list, &shrinker_list);
shrinker->flags |= SHRINKER_REGISTERED;
+ shrinker_debugfs_add(shrinker);
up_write(&shrinker_rwsem);
}
@@ -677,6 +678,7 @@ void unregister_shrinker(struct shrinker *shrinker)
shrinker->flags &= ~SHRINKER_REGISTERED;
if (shrinker->flags & SHRINKER_MEMCG_AWARE)
unregister_memcg_shrinker(shrinker);
+ shrinker_debugfs_remove(shrinker);
up_write(&shrinker_rwsem);
kfree(shrinker->nr_deferred);