dm zoned: dynamically allocate the dm-zoned-meta shrinker

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the dm-zoned-meta shrinker, so that it can be freed
asynchronously via RCU. Then it doesn't need to wait for RCU read-side
critical section when releasing the struct dmz_metadata.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Qi Zheng <[e-mail]>
Reviewed-by: Muchun Song <[e-mail]>
Cc: Alasdair Kergon <[e-mail]>
Cc: Mike Snitzer <[e-mail]>
Cc: Abhinav Kumar <[e-mail]>
Cc: Alexander Viro <[e-mail]>
Cc: Alyssa Rosenzweig <[e-mail]>
Cc: Andreas Dilger <[e-mail]>
Cc: Andreas Gruenbacher <[e-mail]>
Cc: Anna Schumaker <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: Bob Peterson <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Carlos Llamas <[e-mail]>
Cc: Chandan Babu R <[e-mail]>
Cc: Chao Yu <[e-mail]>
Cc: Chris Mason <[e-mail]>
Cc: Christian Brauner <[e-mail]>
Cc: Christian Koenig <[e-mail]>
Cc: Chuck Lever <[e-mail]>
Cc: Coly Li <[e-mail]>
Cc: Dai Ngo <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: "Darrick J. Wong" <[e-mail]>
Cc: Dave Chinner <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: David Airlie <[e-mail]>
Cc: David Hildenbrand <[e-mail]>
Cc: David Sterba <[e-mail]>
Cc: Dmitry Baryshkov <[e-mail]>
Cc: Gao Xiang <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: Huang Rui <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jaegeuk Kim <[e-mail]>
Cc: Jani Nikula <[e-mail]>
Cc: Jan Kara <[e-mail]>
Cc: Jason Wang <[e-mail]>
Cc: Jeff Layton <[e-mail]>
Cc: Jeffle Xu <[e-mail]>
Cc: Joel Fernandes (Google) <[e-mail]>
Cc: Joonas Lahtinen <[e-mail]>
Cc: Josef Bacik <[e-mail]>
Cc: Juergen Gross <[e-mail]>
Cc: Kent Overstreet <[e-mail]>
Cc: Kirill Tkhai <[e-mail]>
Cc: Marijn Suijten <[e-mail]>
Cc: "Michael S. Tsirkin" <[e-mail]>
Cc: Minchan Kim <[e-mail]>
Cc: Muchun Song <[e-mail]>
Cc: Nadav Amit <[e-mail]>
Cc: Neil Brown <[e-mail]>
Cc: Oleksandr Tyshchenko <[e-mail]>
Cc: Olga Kornievskaia <[e-mail]>
Cc: Paul E. McKenney <[e-mail]>
Cc: Richard Weinberger <[e-mail]>
Cc: Rob Clark <[e-mail]>
Cc: Rob Herring <[e-mail]>
Cc: Rodrigo Vivi <[e-mail]>
Cc: Roman Gushchin <[e-mail]>
Cc: Sean Paul <[e-mail]>
Cc: Sergey Senozhatsky <[e-mail]>
Cc: Song Liu <[e-mail]>
Cc: Stefano Stabellini <[e-mail]>
Cc: Steven Price <[e-mail]>
Cc: "Theodore Ts'o" <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Tomeu Vizoso <[e-mail]>
Cc: Tom Talpey <[e-mail]>
Cc: Trond Myklebust <[e-mail]>
Cc: Tvrtko Ursulin <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Cc: Xuan Zhuo <[e-mail]>
Cc: Yue Hu <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

drivers/md/dm-zoned-metadata.c

···
 	struct rb_root		mblk_rbtree;
 	struct list_head	mblk_lru_list;
 	struct list_head	mblk_dirty_list;
-	struct shrinker		mblk_shrinker;
+	struct shrinker		*mblk_shrinker;
 
 	/* Zone allocation management */
 	struct mutex		map_lock;
···
 static unsigned long dmz_mblock_shrinker_count(struct shrinker *shrink,
 					       struct shrink_control *sc)
 {
-	struct dmz_metadata *zmd = container_of(shrink, struct dmz_metadata, mblk_shrinker);
+	struct dmz_metadata *zmd = shrink->private_data;
 
 	return atomic_read(&zmd->nr_mblks);
 }
···
 static unsigned long dmz_mblock_shrinker_scan(struct shrinker *shrink,
 					      struct shrink_control *sc)
 {
-	struct dmz_metadata *zmd = container_of(shrink, struct dmz_metadata, mblk_shrinker);
+	struct dmz_metadata *zmd = shrink->private_data;
 	unsigned long count;
 
 	spin_lock(&zmd->mblk_lock);
···
 	 */
 	zmd->min_nr_mblks = 2 + zmd->nr_map_blocks + zmd->zone_nr_bitmap_blocks * 16;
 	zmd->max_nr_mblks = zmd->min_nr_mblks + 512;
-	zmd->mblk_shrinker.count_objects = dmz_mblock_shrinker_count;
-	zmd->mblk_shrinker.scan_objects = dmz_mblock_shrinker_scan;
-	zmd->mblk_shrinker.seeks = DEFAULT_SEEKS;
 
 	/* Metadata cache shrinker */
-	ret = register_shrinker(&zmd->mblk_shrinker, "dm-zoned-meta:(%u:%u)",
-				MAJOR(dev->bdev->bd_dev),
-				MINOR(dev->bdev->bd_dev));
-	if (ret) {
-		dmz_zmd_err(zmd, "Register metadata cache shrinker failed");
+	zmd->mblk_shrinker = shrinker_alloc(0,  "dm-zoned-meta:(%u:%u)",
+					    MAJOR(dev->bdev->bd_dev),
+					    MINOR(dev->bdev->bd_dev));
+	if (!zmd->mblk_shrinker) {
+		ret = -ENOMEM;
+		dmz_zmd_err(zmd, "Allocate metadata cache shrinker failed");
 		goto err;
 	}
+
+	zmd->mblk_shrinker->count_objects = dmz_mblock_shrinker_count;
+	zmd->mblk_shrinker->scan_objects = dmz_mblock_shrinker_scan;
+	zmd->mblk_shrinker->private_data = zmd;
+
+	shrinker_register(zmd->mblk_shrinker);
 
 	dmz_zmd_info(zmd, "DM-Zoned metadata version %d", zmd->sb_version);
 	for (i = 0; i < zmd->nr_devs; i++)
···
  */
 void dmz_dtr_metadata(struct dmz_metadata *zmd)
 {
-	unregister_shrinker(&zmd->mblk_shrinker);
+	shrinker_free(zmd->mblk_shrinker);
 	dmz_cleanup_metadata(zmd);
 	kfree(zmd);
 }