bcache: dynamically allocate the md-bcache shrinker

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

Link: https://lkml.kernel.org/r/20230911094444.68966-27-zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Acked-by: Muchun Song <songmuchun@bytedance.com>
Cc: Coly Li <colyli@suse.de>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Abhinav Kumar <quic_abhinavk@quicinc.com>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Anna Schumaker <anna@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Carlos Llamas <cmllamas@google.com>
Cc: Chandan Babu R <chandan.babu@oracle.com>
Cc: Chao Yu <chao@kernel.org>
Cc: Chris Mason <clm@fb.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christian Koenig <christian.koenig@amd.com>
Cc: Chuck Lever <cel@kernel.org>
Cc: Dai Ngo <Dai.Ngo@oracle.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Airlie <airlied@gmail.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Sterba <dsterba@suse.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Gao Xiang <hsiangkao@linux.alibaba.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Huang Rui <ray.huang@amd.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Jeffle Xu <jefflexu@linux.alibaba.com>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kirill Tkhai <tkhai@ya.ru>
Cc: Marijn Suijten <marijn.suijten@somainline.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Mike Snitzer <snitzer@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Cc: Olga Kornievskaia <kolga@netapp.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Richard Weinberger <richard@nod.at>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Sean Paul <sean@poorly.run>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Song Liu <song@kernel.org>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: Yue Hu <huyue2@coolpad.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/md/bcache/bcache.h

@@ -541,7 +541,7 @@ struct cache_set {
 	struct bio_set		bio_split;
 
 	/* For the btree cache */
-	struct shrinker		shrink;
+	struct shrinker		*shrink;
 
 	/* For the btree cache and anything allocation related */
 	struct mutex		bucket_lock;

drivers/md/bcache/btree.c

@@ -667,7 +667,7 @@ static int mca_reap(struct btree *b, unsigned int min_order, bool flush)
 static unsigned long bch_mca_scan(struct shrinker *shrink,
 				  struct shrink_control *sc)
 {
-	struct cache_set *c = container_of(shrink, struct cache_set, shrink);
+	struct cache_set *c = shrink->private_data;
 	struct btree *b, *t;
 	unsigned long i, nr = sc->nr_to_scan;
 	unsigned long freed = 0;
@@ -734,7 +734,7 @@ static unsigned long bch_mca_scan(struct shrinker *shrink,
 static unsigned long bch_mca_count(struct shrinker *shrink,
 				   struct shrink_control *sc)
 {
-	struct cache_set *c = container_of(shrink, struct cache_set, shrink);
+	struct cache_set *c = shrink->private_data;
 
 	if (c->shrinker_disabled)
 		return 0;
@@ -752,8 +752,8 @@ void bch_btree_cache_free(struct cache_set *c)
 
 	closure_init_stack(&cl);
 
-	if (c->shrink.list.next)
-		unregister_shrinker(&c->shrink);
+	if (c->shrink)
+		shrinker_free(c->shrink);
 
 	mutex_lock(&c->bucket_lock);
 
@@ -828,14 +828,19 @@ int bch_btree_cache_alloc(struct cache_set *c)
 		c->verify_data = NULL;
 #endif
 
-	c->shrink.count_objects = bch_mca_count;
-	c->shrink.scan_objects = bch_mca_scan;
-	c->shrink.seeks = 4;
-	c->shrink.batch = c->btree_pages * 2;
+	c->shrink = shrinker_alloc(0, "md-bcache:%pU", c->set_uuid);
+	if (!c->shrink) {
+		pr_warn("bcache: %s: could not allocate shrinker\n", __func__);
+		return 0;
+	}
 
-	if (register_shrinker(&c->shrink, "md-bcache:%pU", c->set_uuid))
-		pr_warn("bcache: %s: could not register shrinker\n",
-				__func__);
+	c->shrink->count_objects = bch_mca_count;
+	c->shrink->scan_objects = bch_mca_scan;
+	c->shrink->seeks = 4;
+	c->shrink->batch = c->btree_pages * 2;
+	c->shrink->private_data = c;
+
+	shrinker_register(c->shrink);
 
 	return 0;
 }

drivers/md/bcache/sysfs.c

@@ -866,7 +866,8 @@ STORE(__bch_cache_set)
 
 		sc.gfp_mask = GFP_KERNEL;
 		sc.nr_to_scan = strtoul_or_return(buf);
-		c->shrink.scan_objects(&c->shrink, &sc);
+		if (c->shrink)
+			c->shrink->scan_objects(c->shrink, &sc);
 	}
 
 	sysfs_strtoul_clamp(congested_read_threshold_us,