vmw_balloon: dynamically allocate the vmw-balloon shrinker

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the vmw-balloon 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 vmballoon.

And we can simply exit vmballoon_init() when registering the shrinker
fails. So the shrinker_registered indication is redundant, just remove it.

Link: https://lkml.kernel.org/r/20230911094444.68966-28-zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Nadav Amit <namit@vmware.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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: 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: 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: 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: 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/misc/vmw_balloon.c

@@ -380,16 +380,7 @@ struct vmballoon {
 	/**
 	 * @shrinker: shrinker interface that is used to avoid over-inflation.
 	 */
-	struct shrinker shrinker;
+	struct shrinker *shrinker;
-
-	/**
-	 * @shrinker_registered: whether the shrinker was registered.
-	 *
-	 * The shrinker interface does not handle gracefully the removal of
-	 * shrinker that was not registered before. This indication allows to
-	 * simplify the unregistration process.
-	 */
-	bool shrinker_registered;
 };
 
 static struct vmballoon balloon;
@@ -1568,29 +1559,27 @@ static unsigned long vmballoon_shrinker_count(struct shrinker *shrinker,
 
 static void vmballoon_unregister_shrinker(struct vmballoon *b)
 {
-	if (b->shrinker_registered)
+	shrinker_free(b->shrinker);
-		unregister_shrinker(&b->shrinker);
+	b->shrinker = NULL;
-	b->shrinker_registered = false;
 }
 
 static int vmballoon_register_shrinker(struct vmballoon *b)
 {
-	int r;
-
 	/* Do nothing if the shrinker is not enabled */
 	if (!vmwballoon_shrinker_enable)
 		return 0;
 
-	b->shrinker.scan_objects = vmballoon_shrinker_scan;
+	b->shrinker = shrinker_alloc(0, "vmw-balloon");
-	b->shrinker.count_objects = vmballoon_shrinker_count;
+	if (!b->shrinker)
-	b->shrinker.seeks = DEFAULT_SEEKS;
+		return -ENOMEM;
 
-	r = register_shrinker(&b->shrinker, "vmw-balloon");
+	b->shrinker->scan_objects = vmballoon_shrinker_scan;
+	b->shrinker->count_objects = vmballoon_shrinker_count;
+	b->shrinker->private_data = b;
 
-	if (r == 0)
+	shrinker_register(b->shrinker);
-		b->shrinker_registered = true;
 
-	return r;
+	return 0;
 }
 
 /*
@@ -1883,7 +1872,7 @@ static int __init vmballoon_init(void)
 
 	error = vmballoon_register_shrinker(&balloon);
 	if (error)
-		goto fail;
+		return error;
 
 	/*
 	 * Initialization of compaction must be done after the call to
@@ -1905,9 +1894,6 @@ static int __init vmballoon_init(void)
 	vmballoon_debugfs_init(&balloon);
 
 	return 0;
-fail:
-	vmballoon_unregister_shrinker(&balloon);
-	return error;
 }
 
 /*