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Date:   Mon, 23 May 2022 15:06:22 -0700
From:   Roman Gushchin <roman.gushchin@linux.dev>
To:     Muchun Song <songmuchun@bytedance.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        Dave Chinner <dchinner@redhat.com>,
        linux-kernel@vger.kernel.org,
        Kent Overstreet <kent.overstreet@gmail.com>,
        Hillf Danton <hdanton@sina.com>,
        Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Subject: Re: [PATCH v3 3/6] mm: shrinkers: provide shrinkers with names
Message-ID: <YowFXoh9awP3LuBf@carbon>
References: <20220509183820.573666-1-roman.gushchin@linux.dev>
 <20220509183820.573666-4-roman.gushchin@linux.dev>
 <YooZqOc7MBX0m/oJ@FVFYT0MHHV2J.usts.net>
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In-Reply-To: <YooZqOc7MBX0m/oJ@FVFYT0MHHV2J.usts.net>
Precedence: bulk

On Sun, May 22, 2022 at 07:08:24PM +0800, Muchun Song wrote:
> On Mon, May 09, 2022 at 11:38:17AM -0700, Roman Gushchin wrote:
> > 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.
> > 
> > After this change the shrinker debugfs directory looks like:
> >   $ cd /sys/kernel/debug/shrinker/
> >   $ ls
> >     dqcache-16          sb-hugetlbfs-17  sb-rootfs-2      sb-tmpfs-50
> >     kfree_rcu-0         sb-hugetlbfs-33  sb-securityfs-6  sb-tracefs-13
> >     sb-aio-20           sb-iomem-12      sb-selinuxfs-22  sb-xfs:vda1-36
> >     sb-anon_inodefs-15  sb-mqueue-21     sb-sockfs-8      sb-zsmalloc-19
> >     sb-bdev-3           sb-nsfs-4        sb-sysfs-26      shadow-18
> >     sb-bpf-32           sb-pipefs-14     sb-tmpfs-1       thp_deferred_split-10
> >     sb-btrfs:vda2-24    sb-proc-25       sb-tmpfs-27      thp_zero-9
> >     sb-cgroup2-30       sb-proc-39       sb-tmpfs-29      xfs_buf-37
> >     sb-configfs-23      sb-proc-41       sb-tmpfs-35      xfs_inodegc-38
> >     sb-dax-11           sb-proc-45       sb-tmpfs-40      zspool-34
> >     sb-debugfs-7        sb-proc-46       sb-tmpfs-42
> >     sb-devpts-28        sb-proc-47       sb-tmpfs-43
> >     sb-devtmpfs-5       sb-pstore-31     sb-tmpfs-44
> > 
> > Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
> > ---
> >  arch/x86/kvm/mmu/mmu.c                        |  2 +-
> >  drivers/android/binder_alloc.c                |  2 +-
> >  drivers/gpu/drm/i915/gem/i915_gem_shrinker.c  |  3 +-
> >  drivers/gpu/drm/msm/msm_gem_shrinker.c        |  2 +-
> >  .../gpu/drm/panfrost/panfrost_gem_shrinker.c  |  2 +-
> >  drivers/gpu/drm/ttm/ttm_pool.c                |  2 +-
> >  drivers/md/bcache/btree.c                     |  2 +-
> >  drivers/md/dm-bufio.c                         |  2 +-
> >  drivers/md/dm-zoned-metadata.c                |  2 +-
> >  drivers/md/raid5.c                            |  2 +-
> >  drivers/misc/vmw_balloon.c                    |  2 +-
> >  drivers/virtio/virtio_balloon.c               |  2 +-
> >  drivers/xen/xenbus/xenbus_probe_backend.c     |  2 +-
> >  fs/btrfs/super.c                              |  2 +
> >  fs/erofs/utils.c                              |  2 +-
> >  fs/ext4/extents_status.c                      |  3 +-
> >  fs/f2fs/super.c                               |  2 +-
> >  fs/gfs2/glock.c                               |  2 +-
> >  fs/gfs2/main.c                                |  2 +-
> >  fs/jbd2/journal.c                             |  2 +-
> >  fs/mbcache.c                                  |  2 +-
> >  fs/nfs/nfs42xattr.c                           |  7 ++-
> >  fs/nfs/super.c                                |  2 +-
> >  fs/nfsd/filecache.c                           |  2 +-
> >  fs/nfsd/nfscache.c                            |  2 +-
> >  fs/quota/dquot.c                              |  2 +-
> >  fs/super.c                                    |  6 +-
> >  fs/ubifs/super.c                              |  2 +-
> >  fs/xfs/xfs_buf.c                              |  2 +-
> >  fs/xfs/xfs_icache.c                           |  2 +-
> >  fs/xfs/xfs_qm.c                               |  2 +-
> >  include/linux/shrinker.h                      | 12 +++-
> >  kernel/rcu/tree.c                             |  2 +-
> >  mm/huge_memory.c                              |  4 +-
> >  mm/shrinker_debug.c                           | 45 +++++++++++++-
> >  mm/vmscan.c                                   | 58 ++++++++++++++++++-
> >  mm/workingset.c                               |  2 +-
> >  mm/zsmalloc.c                                 |  2 +-
> >  net/sunrpc/auth.c                             |  2 +-
> >  39 files changed, 154 insertions(+), 46 deletions(-)
> > 
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index c623019929a7..8cfabdd63406 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -6283,7 +6283,7 @@ 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, "mmu");
> >  	if (ret)
> >  		goto out;
> >  
> > diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
> > index 2ac1008a5f39..951343c41ba8 100644
> > --- a/drivers/android/binder_alloc.c
> > +++ b/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, "binder");
> >  		if (ret)
> >  			list_lru_destroy(&binder_alloc_lru);
> >  	}
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
> > index 6a6ff98a8746..85524ef92ea4 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
> > +++ b/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));
> > diff --git a/drivers/gpu/drm/msm/msm_gem_shrinker.c b/drivers/gpu/drm/msm/msm_gem_shrinker.c
> > index 086dacf2f26a..2d3cf4f13dfd 100644
> > --- a/drivers/gpu/drm/msm/msm_gem_shrinker.c
> > +++ b/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));
> > diff --git a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c b/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> > index 77e7cb6d1ae3..0d028266ee9e 100644
> > --- a/drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c
> > +++ b/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"));
> >  }
> >  
> >  /**
> > diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
> > index 1bba0a0ed3f9..b8b41d242197 100644
> > --- a/drivers/gpu/drm/ttm/ttm_pool.c
> > +++ b/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");
> >  }
> >  
> >  /**
> > diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
> > index ad9f16689419..c1f734ab86b3 100644
> > --- a/drivers/md/bcache/btree.c
> > +++ b/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, "btree"))
> >  		pr_warn("bcache: %s: could not register shrinker\n",
> >  				__func__);
> >  
> > diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
> > index 5ffa1dcf84cf..bcc95898c341 100644
> > --- a/drivers/md/dm-bufio.c
> > +++ b/drivers/md/dm-bufio.c
> > @@ -1806,7 +1806,7 @@ 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, "dm_bufio");
> >  	if (r)
> >  		goto bad;
> >  
> > diff --git a/drivers/md/dm-zoned-metadata.c b/drivers/md/dm-zoned-metadata.c
> > index d1ea66114d14..05f2fd12066b 100644
> > --- a/drivers/md/dm-zoned-metadata.c
> > +++ b/drivers/md/dm-zoned-metadata.c
> > @@ -2944,7 +2944,7 @@ 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");
> >  	if (ret) {
> >  		dmz_zmd_err(zmd, "Register metadata cache shrinker failed");
> >  		goto err;
> > diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> > index 59f91e392a2a..34ddebd3aff7 100644
> > --- a/drivers/md/raid5.c
> > +++ b/drivers/md/raid5.c
> > @@ -7383,7 +7383,7 @@ static struct r5conf *setup_conf(struct mddev *mddev)
> >  	conf->shrinker.count_objects = raid5_cache_count;
> >  	conf->shrinker.batch = 128;
> >  	conf->shrinker.flags = 0;
> > -	if (register_shrinker(&conf->shrinker)) {
> > +	if (register_shrinker(&conf->shrinker, "md-%s", mdname(mddev))) {
> >  		pr_warn("md/raid:%s: couldn't register shrinker.\n",
> >  			mdname(mddev));
> >  		goto abort;
> > diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
> > index f1d8ba6d4857..6c9ddf1187dd 100644
> > --- a/drivers/misc/vmw_balloon.c
> > +++ b/drivers/misc/vmw_balloon.c
> > @@ -1587,7 +1587,7 @@ static int vmballoon_register_shrinker(struct vmballoon *b)
> >  	b->shrinker.count_objects = vmballoon_shrinker_count;
> >  	b->shrinker.seeks = DEFAULT_SEEKS;
> >  
> > -	r = register_shrinker(&b->shrinker);
> > +	r = register_shrinker(&b->shrinker, "vmw_balloon");
> >  
> >  	if (r == 0)
> >  		b->shrinker_registered = true;
> > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> > index f4c34a2a6b8e..093e06e19d0e 100644
> > --- a/drivers/virtio/virtio_balloon.c
> > +++ b/drivers/virtio/virtio_balloon.c
> > @@ -875,7 +875,7 @@ static int virtio_balloon_register_shrinker(struct virtio_balloon *vb)
> >  	vb->shrinker.count_objects = virtio_balloon_shrinker_count;
> >  	vb->shrinker.seeks = DEFAULT_SEEKS;
> >  
> > -	return register_shrinker(&vb->shrinker);
> > +	return register_shrinker(&vb->shrinker, "virtio_valloon");
> >  }
> >  
> >  static int virtballoon_probe(struct virtio_device *vdev)
> > diff --git a/drivers/xen/xenbus/xenbus_probe_backend.c b/drivers/xen/xenbus/xenbus_probe_backend.c
> > index 5abded97e1a7..a6c5e344017d 100644
> > --- a/drivers/xen/xenbus/xenbus_probe_backend.c
> > +++ b/drivers/xen/xenbus/xenbus_probe_backend.c
> > @@ -305,7 +305,7 @@ static int __init xenbus_probe_backend_init(void)
> >  
> >  	register_xenstore_notifier(&xenstore_notifier);
> >  
> > -	if (register_shrinker(&backend_memory_shrinker))
> > +	if (register_shrinker(&backend_memory_shrinker, "xen_backend"))
> >  		pr_warn("shrinker registration failed\n");
> >  
> >  	return 0;
> > diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> > index 206f44005c52..062dbd8071e2 100644
> > --- a/fs/btrfs/super.c
> > +++ b/fs/btrfs/super.c
> > @@ -1790,6 +1790,8 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
> >  			error = -EBUSY;
> >  	} else {
> >  		snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
> > +		shrinker_debugfs_rename(&s->s_shrink, "sb-%s:%s", fs_type->name,
> > +					s->s_id);
> >  		btrfs_sb(s)->bdev_holder = fs_type;
> >  		if (!strstr(crc32c_impl(), "generic"))
> >  			set_bit(BTRFS_FS_CSUM_IMPL_FAST, &fs_info->flags);
> > diff --git a/fs/erofs/utils.c b/fs/erofs/utils.c
> > index ec9a1d780dc1..67eb64fadd4f 100644
> > --- a/fs/erofs/utils.c
> > +++ b/fs/erofs/utils.c
> > @@ -282,7 +282,7 @@ static struct shrinker erofs_shrinker_info = {
> >  
> >  int __init erofs_init_shrinker(void)
> >  {
> > -	return register_shrinker(&erofs_shrinker_info);
> > +	return register_shrinker(&erofs_shrinker_info, "erofs");
> >  }
> >  
> >  void erofs_exit_shrinker(void)
> > diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
> > index 9a3a8996aacf..a7aa79d580e5 100644
> > --- a/fs/ext4/extents_status.c
> > +++ b/fs/ext4/extents_status.c
> > @@ -1650,11 +1650,10 @@ int ext4_es_register_shrinker(struct ext4_sb_info *sbi)
> >  	err = percpu_counter_init(&sbi->s_es_stats.es_stats_shk_cnt, 0, GFP_KERNEL);
> >  	if (err)
> >  		goto err3;
> > -
> >  	sbi->s_es_shrinker.scan_objects = ext4_es_scan;
> >  	sbi->s_es_shrinker.count_objects = ext4_es_count;
> >  	sbi->s_es_shrinker.seeks = DEFAULT_SEEKS;
> > -	err = register_shrinker(&sbi->s_es_shrinker);
> > +	err = register_shrinker(&sbi->s_es_shrinker, "ext4_es");
> >  	if (err)
> >  		goto err4;
> >  
> > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > index 4368f90571bd..2fc40a1635f3 100644
> > --- a/fs/f2fs/super.c
> > +++ b/fs/f2fs/super.c
> > @@ -4579,7 +4579,7 @@ static int __init init_f2fs_fs(void)
> >  	err = f2fs_init_sysfs();
> >  	if (err)
> >  		goto free_garbage_collection_cache;
> > -	err = register_shrinker(&f2fs_shrinker_info);
> > +	err = register_shrinker(&f2fs_shrinker_info, "f2fs");
> >  	if (err)
> >  		goto free_sysfs;
> >  	err = register_filesystem(&f2fs_fs_type);
> > diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
> > index 26169cedcefc..791c23d9f7e7 100644
> > --- a/fs/gfs2/glock.c
> > +++ b/fs/gfs2/glock.c
> > @@ -2549,7 +2549,7 @@ int __init gfs2_glock_init(void)
> >  		return -ENOMEM;
> >  	}
> >  
> > -	ret = register_shrinker(&glock_shrinker);
> > +	ret = register_shrinker(&glock_shrinker, "gfs2_glock");
> >  	if (ret) {
> >  		destroy_workqueue(gfs2_delete_workqueue);
> >  		destroy_workqueue(glock_workqueue);
> > diff --git a/fs/gfs2/main.c b/fs/gfs2/main.c
> > index 28d0eb23e18e..dde981b78488 100644
> > --- a/fs/gfs2/main.c
> > +++ b/fs/gfs2/main.c
> > @@ -150,7 +150,7 @@ static int __init init_gfs2_fs(void)
> >  	if (!gfs2_trans_cachep)
> >  		goto fail_cachep8;
> >  
> > -	error = register_shrinker(&gfs2_qd_shrinker);
> > +	error = register_shrinker(&gfs2_qd_shrinker, "gfs2_qd");
> >  	if (error)
> >  		goto fail_shrinker;
> >  
> > diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> > index c0cbeeaec2d1..e7786445ecc1 100644
> > --- a/fs/jbd2/journal.c
> > +++ b/fs/jbd2/journal.c
> > @@ -1418,7 +1418,7 @@ static journal_t *journal_init_common(struct block_device *bdev,
> >  	if (percpu_counter_init(&journal->j_checkpoint_jh_count, 0, GFP_KERNEL))
> >  		goto err_cleanup;
> >  
> > -	if (register_shrinker(&journal->j_shrinker)) {
> > +	if (register_shrinker(&journal->j_shrinker, "jbd2_journal")) {
> >  		percpu_counter_destroy(&journal->j_checkpoint_jh_count);
> >  		goto err_cleanup;
> >  	}
> > diff --git a/fs/mbcache.c b/fs/mbcache.c
> > index 97c54d3a2227..379dc5b0b6ad 100644
> > --- a/fs/mbcache.c
> > +++ b/fs/mbcache.c
> > @@ -367,7 +367,7 @@ struct mb_cache *mb_cache_create(int bucket_bits)
> >  	cache->c_shrink.count_objects = mb_cache_count;
> >  	cache->c_shrink.scan_objects = mb_cache_scan;
> >  	cache->c_shrink.seeks = DEFAULT_SEEKS;
> > -	if (register_shrinker(&cache->c_shrink)) {
> > +	if (register_shrinker(&cache->c_shrink, "mb_cache")) {
> >  		kfree(cache->c_hash);
> >  		kfree(cache);
> >  		goto err_out;
> > diff --git a/fs/nfs/nfs42xattr.c b/fs/nfs/nfs42xattr.c
> > index e7b34f7e0614..147b8a2f2dc6 100644
> > --- a/fs/nfs/nfs42xattr.c
> > +++ b/fs/nfs/nfs42xattr.c
> > @@ -1017,15 +1017,16 @@ int __init nfs4_xattr_cache_init(void)
> >  	if (ret)
> >  		goto out2;
> >  
> > -	ret = register_shrinker(&nfs4_xattr_cache_shrinker);
> > +	ret = register_shrinker(&nfs4_xattr_cache_shrinker, "nfs_xattr_cache");
> >  	if (ret)
> >  		goto out1;
> >  
> > -	ret = register_shrinker(&nfs4_xattr_entry_shrinker);
> > +	ret = register_shrinker(&nfs4_xattr_entry_shrinker, "nfs_xattr_entry");
> >  	if (ret)
> >  		goto out;
> >  
> > -	ret = register_shrinker(&nfs4_xattr_large_entry_shrinker);
> > +	ret = register_shrinker(&nfs4_xattr_large_entry_shrinker,
> > +				"nfs_xattr_large_entry");
> >  	if (!ret)
> >  		return 0;
> >  
> > diff --git a/fs/nfs/super.c b/fs/nfs/super.c
> > index 6ab5eeb000dc..c7a2aef911f1 100644
> > --- a/fs/nfs/super.c
> > +++ b/fs/nfs/super.c
> > @@ -149,7 +149,7 @@ int __init register_nfs_fs(void)
> >  	ret = nfs_register_sysctl();
> >  	if (ret < 0)
> >  		goto error_2;
> > -	ret = register_shrinker(&acl_shrinker);
> > +	ret = register_shrinker(&acl_shrinker, "nfs_acl");
> >  	if (ret < 0)
> >  		goto error_3;
> >  #ifdef CONFIG_NFS_V4_2
> > diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
> > index 2c1b027774d4..9c2879a3c3c0 100644
> > --- a/fs/nfsd/filecache.c
> > +++ b/fs/nfsd/filecache.c
> > @@ -666,7 +666,7 @@ nfsd_file_cache_init(void)
> >  		goto out_err;
> >  	}
> >  
> > -	ret = register_shrinker(&nfsd_file_shrinker);
> > +	ret = register_shrinker(&nfsd_file_shrinker, "nfsd_filecache");
> >  	if (ret) {
> >  		pr_err("nfsd: failed to register nfsd_file_shrinker: %d\n", ret);
> >  		goto out_lru;
> > diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
> > index 0b3f12aa37ff..f1cfb06d0be5 100644
> > --- a/fs/nfsd/nfscache.c
> > +++ b/fs/nfsd/nfscache.c
> > @@ -176,7 +176,7 @@ int nfsd_reply_cache_init(struct nfsd_net *nn)
> >  	nn->nfsd_reply_cache_shrinker.scan_objects = nfsd_reply_cache_scan;
> >  	nn->nfsd_reply_cache_shrinker.count_objects = nfsd_reply_cache_count;
> >  	nn->nfsd_reply_cache_shrinker.seeks = 1;
> > -	status = register_shrinker(&nn->nfsd_reply_cache_shrinker);
> > +	status = register_shrinker(&nn->nfsd_reply_cache_shrinker, "nfsd_reply");
> >  	if (status)
> >  		goto out_stats_destroy;
> >  
> > diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
> > index a74aef99bd3d..854d2b1d0914 100644
> > --- a/fs/quota/dquot.c
> > +++ b/fs/quota/dquot.c
> > @@ -2985,7 +2985,7 @@ static int __init dquot_init(void)
> >  	pr_info("VFS: Dquot-cache hash table entries: %ld (order %ld,"
> >  		" %ld bytes)\n", nr_hash, order, (PAGE_SIZE << order));
> >  
> > -	if (register_shrinker(&dqcache_shrinker))
> > +	if (register_shrinker(&dqcache_shrinker, "dqcache"))
> >  		panic("Cannot register dquot shrinker");
> >  
> >  	return 0;
> > diff --git a/fs/super.c b/fs/super.c
> > index 60f57c7bc0a6..4fca6657f442 100644
> > --- a/fs/super.c
> > +++ b/fs/super.c
> > @@ -265,7 +265,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
> >  	s->s_shrink.count_objects = super_cache_count;
> >  	s->s_shrink.batch = 1024;
> >  	s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE;
> > -	if (prealloc_shrinker(&s->s_shrink))
> > +	if (prealloc_shrinker(&s->s_shrink, "sb-%s", type->name))
> >  		goto fail;
> >  	if (list_lru_init_memcg(&s->s_dentry_lru, &s->s_shrink))
> >  		goto fail;
> > @@ -1288,6 +1288,8 @@ int get_tree_bdev(struct fs_context *fc,
> >  	} else {
> >  		s->s_mode = mode;
> >  		snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
> > +		shrinker_debugfs_rename(&s->s_shrink, "sb-%s:%s",
> > +					fc->fs_type->name, s->s_id);
> >  		sb_set_blocksize(s, block_size(bdev));
> >  		error = fill_super(s, fc);
> >  		if (error) {
> > @@ -1363,6 +1365,8 @@ struct dentry *mount_bdev(struct file_system_type *fs_type,
> >  	} else {
> >  		s->s_mode = mode;
> >  		snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
> > +		shrinker_debugfs_rename(&s->s_shrink, "sb-%s:%s",
> > +					fs_type->name, s->s_id);
> >  		sb_set_blocksize(s, block_size(bdev));
> >  		error = fill_super(s, data, flags & SB_SILENT ? 1 : 0);
> >  		if (error) {
> > diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
> > index bad67455215f..a3663d201f64 100644
> > --- a/fs/ubifs/super.c
> > +++ b/fs/ubifs/super.c
> > @@ -2430,7 +2430,7 @@ static int __init ubifs_init(void)
> >  	if (!ubifs_inode_slab)
> >  		return -ENOMEM;
> >  
> > -	err = register_shrinker(&ubifs_shrinker_info);
> > +	err = register_shrinker(&ubifs_shrinker_info, "ubifs");
> >  	if (err)
> >  		goto out_slab;
> >  
> > diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> > index e1afb9e503e1..5645e92df0c9 100644
> > --- a/fs/xfs/xfs_buf.c
> > +++ b/fs/xfs/xfs_buf.c
> > @@ -1986,7 +1986,7 @@ xfs_alloc_buftarg(
> >  	btp->bt_shrinker.scan_objects = xfs_buftarg_shrink_scan;
> >  	btp->bt_shrinker.seeks = DEFAULT_SEEKS;
> >  	btp->bt_shrinker.flags = SHRINKER_NUMA_AWARE;
> > -	if (register_shrinker(&btp->bt_shrinker))
> > +	if (register_shrinker(&btp->bt_shrinker, "xfs_buf"))
> >  		goto error_pcpu;
> >  	return btp;
> >  
> > diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> > index bffd6eb0b298..d0c4e74ff763 100644
> > --- a/fs/xfs/xfs_icache.c
> > +++ b/fs/xfs/xfs_icache.c
> > @@ -2198,5 +2198,5 @@ xfs_inodegc_register_shrinker(
> >  	shrink->flags = SHRINKER_NONSLAB;
> >  	shrink->batch = XFS_INODEGC_SHRINKER_BATCH;
> >  
> > -	return register_shrinker(shrink);
> > +	return register_shrinker(shrink, "xfs_inodegc");
> >  }
> > diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
> > index f165d1a3de1d..93ded9e81f49 100644
> > --- a/fs/xfs/xfs_qm.c
> > +++ b/fs/xfs/xfs_qm.c
> > @@ -686,7 +686,7 @@ xfs_qm_init_quotainfo(
> >  	qinf->qi_shrinker.seeks = DEFAULT_SEEKS;
> >  	qinf->qi_shrinker.flags = SHRINKER_NUMA_AWARE;
> >  
> > -	error = register_shrinker(&qinf->qi_shrinker);
> > +	error = register_shrinker(&qinf->qi_shrinker, "xfs_qm");
> >  	if (error)
> >  		goto out_free_inos;
> >  
> > diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
> > index 2ced8149c513..64416f3e0a1f 100644
> > --- a/include/linux/shrinker.h
> > +++ b/include/linux/shrinker.h
> > @@ -75,6 +75,7 @@ struct shrinker {
> >  #endif
> >  #ifdef CONFIG_SHRINKER_DEBUG
> >  	int debugfs_id;
> > +	const char *name;
> >  	struct dentry *debugfs_entry;
> >  #endif
> >  	/* objs pending delete, per node */
> > @@ -92,9 +93,9 @@ struct shrinker {
> >   */
> >  #define SHRINKER_NONSLAB	(1 << 3)
> >  
> > -extern int prealloc_shrinker(struct shrinker *shrinker);
> > +extern int prealloc_shrinker(struct shrinker *shrinker, const char *fmt, ...);
> >  extern void register_shrinker_prepared(struct shrinker *shrinker);
> > -extern int register_shrinker(struct shrinker *shrinker);
> > +extern int register_shrinker(struct shrinker *shrinker, const char *fmt, ...);
> >  extern void unregister_shrinker(struct shrinker *shrinker);
> >  extern void free_prealloced_shrinker(struct shrinker *shrinker);
> >  extern void synchronize_shrinkers(void);
> > @@ -102,6 +103,8 @@ extern void synchronize_shrinkers(void);
> >  #ifdef CONFIG_SHRINKER_DEBUG
> >  extern int shrinker_debugfs_add(struct shrinker *shrinker);
> >  extern void shrinker_debugfs_remove(struct shrinker *shrinker);
> > +extern int shrinker_debugfs_rename(struct shrinker *shrinker,
> > +				   const char *fmt, ...);
> >  #else /* CONFIG_SHRINKER_DEBUG */
> >  static inline int shrinker_debugfs_add(struct shrinker *shrinker)
> >  {
> > @@ -110,5 +113,10 @@ static inline int shrinker_debugfs_add(struct shrinker *shrinker)
> >  static inline void shrinker_debugfs_remove(struct shrinker *shrinker)
> >  {
> >  }
> > +static inline int shrinker_debugfs_rename(struct shrinker *shrinker,
> > +					  const char *fmt, ...)
> > +{
> > +	return 0;
> > +}
> >  #endif /* CONFIG_SHRINKER_DEBUG */
> >  #endif /* _LINUX_SHRINKER_H */
> > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > index 5c587e00811c..b4c66916bea9 100644
> > --- a/kernel/rcu/tree.c
> > +++ b/kernel/rcu/tree.c
> > @@ -4978,7 +4978,7 @@ static void __init kfree_rcu_batch_init(void)
> >  		INIT_DELAYED_WORK(&krcp->page_cache_work, fill_page_cache_func);
> >  		krcp->initialized = true;
> >  	}
> > -	if (register_shrinker(&kfree_rcu_shrinker))
> > +	if (register_shrinker(&kfree_rcu_shrinker, "kfree_rcu"))
> >  		pr_err("Failed to register kfree_rcu() shrinker!\n");
> >  }
> >  
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index fa6a1623976a..a40df19c0e38 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -423,10 +423,10 @@ static int __init hugepage_init(void)
> >  	if (err)
> >  		goto err_slab;
> >  
> > -	err = register_shrinker(&huge_zero_page_shrinker);
> > +	err = register_shrinker(&huge_zero_page_shrinker, "thp_zero");
> >  	if (err)
> >  		goto err_hzp_shrinker;
> > -	err = register_shrinker(&deferred_split_shrinker);
> > +	err = register_shrinker(&deferred_split_shrinker, "thp_deferred_split");
> >  	if (err)
> >  		goto err_split_shrinker;
> >  
> > diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
> > index fd1f805a581a..28b1c1ab60ef 100644
> > --- a/mm/shrinker_debug.c
> > +++ b/mm/shrinker_debug.c
> > @@ -104,7 +104,7 @@ DEFINE_SHOW_ATTRIBUTE(shrinker_debugfs_count);
> >  int shrinker_debugfs_add(struct shrinker *shrinker)
> >  {
> >  	struct dentry *entry;
> > -	char buf[16];
> > +	char buf[128];
> >  	int id;
> >  
> >  	lockdep_assert_held(&shrinker_rwsem);
> > @@ -118,7 +118,7 @@ int shrinker_debugfs_add(struct shrinker *shrinker)
> >  		return id;
> >  	shrinker->debugfs_id = id;
> >  
> > -	snprintf(buf, sizeof(buf), "%d", id);
> > +	snprintf(buf, sizeof(buf), "%s-%d", shrinker->name, id);
> >  
> >  	/* create debugfs entry */
> >  	entry = debugfs_create_dir(buf, shrinker_debugfs_root);
> > @@ -133,10 +133,51 @@ int shrinker_debugfs_add(struct shrinker *shrinker)
> >  	return 0;
> >  }
> >  
> > +int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
> > +{
> > +	struct dentry *entry;
> > +	char buf[128];
> > +	const char *old;
> > +	va_list ap;
> > +	int ret = 0;
> > +
> > +	down_write(&shrinker_rwsem);
> > +
> > +	old = shrinker->name;
> > +
> > +	va_start(ap, fmt);
> > +	shrinker->name = kvasprintf_const(GFP_KERNEL, fmt, ap);
> > +	va_end(ap);
> > +	if (!shrinker->name) {
> > +		shrinker->name = old;
> > +		ret = -ENOMEM;
> 
> Seems we could move those 6 lines out of shrinker_rwsem.  I know
> this function is not in a hot path, but it it better to improve
> it if it is easy, right?

Not sure if it worth it, but ok, it's indeed easy.

> 
> > +	} else 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;
> > +
> > +		kfree_const(old);
> > +	}
> > +
> > +	up_write(&shrinker_rwsem);
> > +
> > +	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;
> >  
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index 024f7056b98c..42bae0fd0442 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -613,7 +613,7 @@ static unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru,
> >  /*
> >   * Add a shrinker callback to be called from the vm.
> >   */
> > -int prealloc_shrinker(struct shrinker *shrinker)
> > +static int __prealloc_shrinker(struct shrinker *shrinker)
> >  {
> >  	unsigned int size;
> >  	int err;
> > @@ -637,8 +637,36 @@ int prealloc_shrinker(struct shrinker *shrinker)
> >  	return 0;
> >  }
> >  
> > +#ifdef CONFIG_SHRINKER_DEBUG
> > +int prealloc_shrinker(struct shrinker *shrinker, const char *fmt, ...)
> > +{
> > +	va_list ap;
> > +	int err;
> > +
> > +	va_start(ap, fmt);
> > +	shrinker->name = kvasprintf_const(GFP_KERNEL, fmt, ap);
> > +	va_end(ap);
> > +	if (!shrinker->name)
> > +		return -ENOMEM;
> > +
> > +	err = __prealloc_shrinker(shrinker);
> > +	if (err)
> > +		kfree_const(shrinker->name);
> > +
> > +	return err;
> > +}
> > +#else
> > +int prealloc_shrinker(struct shrinker *shrinker, const char *fmt, ...)
> > +{
> > +	return __prealloc_shrinker(shrinker);
> > +}
> > +#endif
> > +
> >  void free_prealloced_shrinker(struct shrinker *shrinker)
> >  {
> > +#ifdef CONFIG_SHRINKER_DEBUG
> > +	kfree_const(shrinker->name);
> > +#endif
> >  	if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
> >  		down_write(&shrinker_rwsem);
> >  		unregister_memcg_shrinker(shrinker);
> > @@ -659,15 +687,39 @@ void register_shrinker_prepared(struct shrinker *shrinker)
> >  	up_write(&shrinker_rwsem);
> >  }
> >  
> > -int register_shrinker(struct shrinker *shrinker)
> > +static int __register_shrinker(struct shrinker *shrinker)
> >  {
> > -	int err = prealloc_shrinker(shrinker);
> > +	int err = __prealloc_shrinker(shrinker);
> >  
> >  	if (err)
> >  		return err;
> >  	register_shrinker_prepared(shrinker);
> >  	return 0;
> >  }
> > +
> > +#ifdef CONFIG_SHRINKER_DEBUG
> > +int register_shrinker(struct shrinker *shrinker, const char *fmt, ...)
> > +{
> > +	va_list ap;
> > +	int err;
> > +
> > +	va_start(ap, fmt);
> > +	shrinker->name = kvasprintf_const(GFP_KERNEL, fmt, ap);
> > +	va_end(ap);
> > +	if (!shrinker->name)
> > +		return -ENOMEM;
> > +
> 
> How about moving those initialization of name into shrinker_debugfs_add()?
> Then maybe we could hide handling to "name" from vmscan.c.

shrinker_debugfs_add() can be delayed up to the moment when debugfs is
initialized. Some shrinkers are registered earlier. So it's not (easily)
possible.

Thanks!