md/raid5: dynamically allocate the md-raid5 shrinker

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the md-raid5 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 r5conf.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Qi Zheng <[e-mail]>
Reviewed-by: Muchun Song <[e-mail]>
Reviewed-by: Song Liu <[e-mail]>
Cc: Abhinav Kumar <[e-mail]>
Cc: Alasdair Kergon <[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: Mike Snitzer <[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: 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/raid5.c

···
 
 	log_exit(conf);
 
-	unregister_shrinker(&conf->shrinker);
+	shrinker_free(conf->shrinker);
 	free_thread_groups(conf);
 	shrink_stripes(conf);
 	raid5_free_percpu(conf);
···
 static unsigned long raid5_cache_scan(struct shrinker *shrink,
 				      struct shrink_control *sc)
 {
-	struct r5conf *conf = container_of(shrink, struct r5conf, shrinker);
+	struct r5conf *conf = shrink->private_data;
 	unsigned long ret = SHRINK_STOP;
 
 	if (mutex_trylock(&conf->cache_size_mutex)) {
···
 static unsigned long raid5_cache_count(struct shrinker *shrink,
 				       struct shrink_control *sc)
 {
-	struct r5conf *conf = container_of(shrink, struct r5conf, shrinker);
+	struct r5conf *conf = shrink->private_data;
 
 	if (conf->max_nr_stripes < conf->min_nr_stripes)
 		/* unlikely, but not impossible */
···
 	 * it reduces the queue depth and so can hurt throughput.
 	 * So set it rather large, scaled by number of devices.
 	 */
-	conf->shrinker.seeks = DEFAULT_SEEKS * conf->raid_disks * 4;
-	conf->shrinker.scan_objects = raid5_cache_scan;
-	conf->shrinker.count_objects = raid5_cache_count;
-	conf->shrinker.batch = 128;
-	conf->shrinker.flags = 0;
-	ret = register_shrinker(&conf->shrinker, "md-raid5:%s", mdname(mddev));
-	if (ret) {
-		pr_warn("md/raid:%s: couldn't register shrinker.\n",
+	conf->shrinker = shrinker_alloc(0, "md-raid5:%s", mdname(mddev));
+	if (!conf->shrinker) {
+		ret = -ENOMEM;
+		pr_warn("md/raid:%s: couldn't allocate shrinker.\n",
 			mdname(mddev));
 		goto abort;
 	}
+
+	conf->shrinker->seeks = DEFAULT_SEEKS * conf->raid_disks * 4;
+	conf->shrinker->scan_objects = raid5_cache_scan;
+	conf->shrinker->count_objects = raid5_cache_count;
+	conf->shrinker->batch = 128;
+	conf->shrinker->private_data = conf;
+
+	shrinker_register(conf->shrinker);
 
 	sprintf(pers_name, "raid%d", mddev->new_level);
 	rcu_assign_pointer(conf->thread,

drivers/md/raid5.h

···
 	wait_queue_head_t	wait_for_stripe;
 	wait_queue_head_t	wait_for_overlap;
 	unsigned long		cache_state;
-	struct shrinker		shrinker;
+	struct shrinker		*shrinker;
 	int			pool_size; /* number of disks in stripeheads in pool */
 	spinlock_t		device_lock;
 	struct disk_info	*disks;