mm: shrinkers: provide shrinkers with names

Currently shrinkers are anonymous objects.  For debugging purposes they
can be identified by count/scan function names, but it's not always
useful: e.g.  for superblock's shrinkers it's nice to have at least an
idea of to which superblock the shrinker belongs.

This commit adds names to shrinkers.  register_shrinker() and
prealloc_shrinker() functions are extended to take a format and arguments
to master a name.

In some cases it's not possible to determine a good name at the time when
a shrinker is allocated.  For such cases shrinker_debugfs_rename() is
provided.

The expected format is:
    <subsystem>-<shrinker_type>[:<instance>]-<id>
For some shrinkers an instance can be encoded as (MAJOR:MINOR) pair.

After this change the shrinker debugfs directory looks like:
  $ cd /sys/kernel/debug/shrinker/
  $ ls
    dquota-cache-16     sb-devpts-28     sb-proc-47       sb-tmpfs-42
    mm-shadow-18        sb-devtmpfs-5    sb-proc-48       sb-tmpfs-43
    mm-zspool:zram0-34  sb-hugetlbfs-17  sb-pstore-31     sb-tmpfs-44
    rcu-kfree-0         sb-hugetlbfs-33  sb-rootfs-2      sb-tmpfs-49
    sb-aio-20           sb-iomem-12      sb-securityfs-6  sb-tracefs-13
    sb-anon_inodefs-15  sb-mqueue-21     sb-selinuxfs-22  sb-xfs:vda1-36
    sb-bdev-3           sb-nsfs-4        sb-sockfs-8      sb-zsmalloc-19
    sb-bpf-32           sb-pipefs-14     sb-sysfs-26      thp-deferred_split-10
    sb-btrfs:vda2-24    sb-proc-25       sb-tmpfs-1       thp-zero-9
    sb-cgroup2-30       sb-proc-39       sb-tmpfs-27      xfs-buf:vda1-37
    sb-configfs-23      sb-proc-41       sb-tmpfs-29      xfs-inodegc:vda1-38
    sb-dax-11           sb-proc-45       sb-tmpfs-35
    sb-debugfs-7        sb-proc-46       sb-tmpfs-40

[[email protected]: fix build warnings]
  Link: https://lkml.kernel.org/r/Yr+ZTnLb9lJk6fJO@castle
  Reported-by: kernel test robot <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Roman Gushchin <[email protected]>
Cc: Christophe JAILLET <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Hillf Danton <[email protected]>
Cc: Kent Overstreet <[email protected]>
Cc: Muchun Song <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: rgushchin

arch/x86/kvm/mmu/mmu.c

@@ -6317,7 +6317,7 @@ int kvm_mmu_vendor_module_init(void)
 	if (percpu_counter_init(&kvm_total_used_mmu_pages, 0, GFP_KERNEL))
 		goto out;
 
-	ret = register_shrinker(&mmu_shrinker);
+	ret = register_shrinker(&mmu_shrinker, "x86-mmu");
 	if (ret)
 		goto out;
 

drivers/android/binder_alloc.c

@@ -1084,7 +1084,7 @@ int binder_alloc_shrinker_init(void)
 	int ret = list_lru_init(&binder_alloc_lru);
 
 	if (ret == 0) {
-		ret = register_shrinker(&binder_shrinker);
+		ret = register_shrinker(&binder_shrinker, "android-binder");
 		if (ret)
 			list_lru_destroy(&binder_alloc_lru);
 	}

drivers/gpu/drm/i915/gem/i915_gem_shrinker.c

@@ -426,7 +426,8 @@ void i915_gem_driver_register__shrinker(struct drm_i915_private *i915)
 	i915->mm.shrinker.count_objects = i915_gem_shrinker_count;
 	i915->mm.shrinker.seeks = DEFAULT_SEEKS;
 	i915->mm.shrinker.batch = 4096;
-	drm_WARN_ON(&i915->drm, register_shrinker(&i915->mm.shrinker));
+	drm_WARN_ON(&i915->drm, register_shrinker(&i915->mm.shrinker,
+						  "drm-i915_gem"));
 
 	i915->mm.oom_notifier.notifier_call = i915_gem_shrinker_oom;
 	drm_WARN_ON(&i915->drm, register_oom_notifier(&i915->mm.oom_notifier));

drivers/gpu/drm/msm/msm_gem_shrinker.c

@@ -221,7 +221,7 @@ void msm_gem_shrinker_init(struct drm_device *dev)
 	priv->shrinker.count_objects = msm_gem_shrinker_count;
 	priv->shrinker.scan_objects = msm_gem_shrinker_scan;
 	priv->shrinker.seeks = DEFAULT_SEEKS;
-	WARN_ON(register_shrinker(&priv->shrinker));
+	WARN_ON(register_shrinker(&priv->shrinker, "drm-msm_gem"));
 
 	priv->vmap_notifier.notifier_call = msm_gem_shrinker_vmap;
 	WARN_ON(register_vmap_purge_notifier(&priv->vmap_notifier));

drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c

@@ -103,7 +103,7 @@ void panfrost_gem_shrinker_init(struct drm_device *dev)
 	pfdev->shrinker.count_objects = panfrost_gem_shrinker_count;
 	pfdev->shrinker.scan_objects = panfrost_gem_shrinker_scan;
 	pfdev->shrinker.seeks = DEFAULT_SEEKS;
-	WARN_ON(register_shrinker(&pfdev->shrinker));
+	WARN_ON(register_shrinker(&pfdev->shrinker, "drm-panfrost"));
 }
 
 /**

drivers/gpu/drm/ttm/ttm_pool.c

@@ -722,7 +722,7 @@ int ttm_pool_mgr_init(unsigned long num_pages)
 	mm_shrinker.count_objects = ttm_pool_shrinker_count;
 	mm_shrinker.scan_objects = ttm_pool_shrinker_scan;
 	mm_shrinker.seeks = 1;
-	return register_shrinker(&mm_shrinker);
+	return register_shrinker(&mm_shrinker, "drm-ttm_pool");
 }
 
 /**

drivers/md/bcache/btree.c

@@ -812,7 +812,7 @@ int bch_btree_cache_alloc(struct cache_set *c)
 	c->shrink.seeks = 4;
 	c->shrink.batch = c->btree_pages * 2;
 
-	if (register_shrinker(&c->shrink))
+	if (register_shrinker(&c->shrink, "md-bcache:%pU", c->set_uuid))
 		pr_warn("bcache: %s: could not register shrinker\n",
 				__func__);
 

drivers/md/dm-bufio.c

@@ -1806,7 +1806,8 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
 	c->shrinker.scan_objects = dm_bufio_shrink_scan;
 	c->shrinker.seeks = 1;
 	c->shrinker.batch = 0;
-	r = register_shrinker(&c->shrinker);
+	r = register_shrinker(&c->shrinker, "md-%s:(%u:%u)", slab_name,
+			      MAJOR(bdev->bd_dev), MINOR(bdev->bd_dev));
 	if (r)
 		goto bad;
 

drivers/md/dm-zoned-metadata.c

@@ -2944,7 +2944,9 @@ int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev,
 	zmd->mblk_shrinker.seeks = DEFAULT_SEEKS;
 
 	/* Metadata cache shrinker */
-	ret = register_shrinker(&zmd->mblk_shrinker);
+	ret = register_shrinker(&zmd->mblk_shrinker, "md-meta:(%u:%u)",
+				MAJOR(dev->bdev->bd_dev),
+				MINOR(dev->bdev->bd_dev));
 	if (ret) {
 		dmz_zmd_err(zmd, "Register metadata cache shrinker failed");
 		goto err;

drivers/md/raid5.c

@@ -7414,7 +7414,7 @@ static struct r5conf *setup_conf(struct mddev *mddev)
 	conf->shrinker.count_objects = raid5_cache_count;
 	conf->shrinker.batch = 128;
 	conf->shrinker.flags = 0;
-	ret = register_shrinker(&conf->shrinker);
+	ret = register_shrinker(&conf->shrinker, "md-raid5:%s", mdname(mddev));
 	if (ret) {
 		pr_warn("md/raid:%s: couldn't register shrinker.\n",
 			mdname(mddev));