// 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[128];
	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), "%s-%d", shrinker->name, 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;
}

int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
{
	struct dentry *entry;
	char buf[128];
	const char *new, *old;
	va_list ap;
	int ret = 0;

	va_start(ap, fmt);
	new = kvasprintf_const(GFP_KERNEL, fmt, ap);
	va_end(ap);

	if (!new)
		return -ENOMEM;

	down_write(&shrinker_rwsem);

	old = shrinker->name;
	shrinker->name = new;

	if (shrinker->debugfs_entry) {
		snprintf(buf, sizeof(buf), "%s-%d", shrinker->name,
			 shrinker->debugfs_id);

		entry = debugfs_rename(shrinker_debugfs_root,
				       shrinker->debugfs_entry,
				       shrinker_debugfs_root, buf);
		if (IS_ERR(entry))
			ret = PTR_ERR(entry);
		else
			shrinker->debugfs_entry = entry;
	}

	up_write(&shrinker_rwsem);

	kfree_const(old);

	return ret;
}
EXPORT_SYMBOL(shrinker_debugfs_rename);

void shrinker_debugfs_remove(struct shrinker *shrinker)
{
	lockdep_assert_held(&shrinker_rwsem);

	kfree_const(shrinker->name);

	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);