mbcache: dynamically allocate the mbcache shrinker

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the mbcache 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 mb_cache.

Link: https://lkml.kernel.org/r/20230911094444.68966-30-zhengqi.arch@bytedance.comSigned-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Abhinav Kumar <quic_abhinavk@quicinc.com>
Cc: Alasdair Kergon <agk@redhat.com>
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 Koenig <christian.koenig@amd.com>
Cc: Chuck Lever <cel@kernel.org>
Cc: Coly Li <colyli@suse.de>
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: Kent Overstreet <kent.overstreet@gmail.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: Muchun Song <muchun.song@linux.dev>
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>

fs/mbcache.c

@@ -37,7 +37,7 @@ struct mb_cache {
 	struct list_head	c_list;
 	/* Number of entries in cache */
 	unsigned long		c_entry_count;
-	struct shrinker		c_shrink;
+	struct shrinker		*c_shrink;
 	/* Work for shrinking when the cache has too many entries */
 	struct work_struct	c_shrink_work;
 };
@@ -293,8 +293,7 @@ EXPORT_SYMBOL(mb_cache_entry_touch);
 static unsigned long mb_cache_count(struct shrinker *shrink,
 				    struct shrink_control *sc)
 {
-	struct mb_cache *cache = container_of(shrink, struct mb_cache,
-					      c_shrink);
+	struct mb_cache *cache = shrink->private_data;
 
 	return cache->c_entry_count;
 }
@@ -333,8 +332,7 @@ static unsigned long mb_cache_shrink(struct mb_cache *cache,
 static unsigned long mb_cache_scan(struct shrinker *shrink,
 				   struct shrink_control *sc)
 {
-	struct mb_cache *cache = container_of(shrink, struct mb_cache,
-					      c_shrink);
+	struct mb_cache *cache = shrink->private_data;
 	return mb_cache_shrink(cache, sc->nr_to_scan);
 }
 
@@ -377,15 +375,19 @@ struct mb_cache *mb_cache_create(int bucket_bits)
 	for (i = 0; i < bucket_count; i++)
 		INIT_HLIST_BL_HEAD(&cache->c_hash[i]);
 
-	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, "mbcache-shrinker")) {
+	cache->c_shrink = shrinker_alloc(0, "mbcache-shrinker");
+	if (!cache->c_shrink) {
 		kfree(cache->c_hash);
 		kfree(cache);
 		goto err_out;
 	}
 
+	cache->c_shrink->count_objects = mb_cache_count;
+	cache->c_shrink->scan_objects = mb_cache_scan;
+	cache->c_shrink->private_data = cache;
+
+	shrinker_register(cache->c_shrink);
+
 	INIT_WORK(&cache->c_shrink_work, mb_cache_shrink_worker);
 
 	return cache;
@@ -406,7 +408,7 @@ void mb_cache_destroy(struct mb_cache *cache)
 {
 	struct mb_cache_entry *entry, *next;
 
-	unregister_shrinker(&cache->c_shrink);
+	shrinker_free(cache->c_shrink);
 
 	/*
 	 * We don't bother with any locking. Cache must not be used at this