[PATCH 08/29] md/raid5: dynamically allocate the md-raid5 shrinker

[Qi Zheng]

From: Qi Zheng <zhengqi.arch at bytedance.com>

In preparation for implementing lockless slab shrink,
we need to dynamically allocate the md-raid5 shrinker,
so that it can be freed asynchronously using kfree_rcu().
Then it doesn't need to wait for RCU read-side critical
section when releasing the struct r5conf.

Signed-off-by: Qi Zheng <zhengqi.arch at bytedance.com>
---
 drivers/md/raid5.c | 28 +++++++++++++++++-----------
 drivers/md/raid5.h |  2 +-
 2 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index f4eea1bbbeaf..4866cad1ad62 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -7391,7 +7391,7 @@ static void free_conf(struct r5conf *conf)
 
 	log_exit(conf);
 
-	unregister_shrinker(&conf->shrinker);
+	unregister_and_free_shrinker(conf->shrinker);
 	free_thread_groups(conf);
 	shrink_stripes(conf);
 	raid5_free_percpu(conf);
@@ -7439,7 +7439,7 @@ static int raid5_alloc_percpu(struct r5conf *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)) {
@@ -7460,7 +7460,7 @@ static unsigned long raid5_cache_scan(struct shrinker *shrink,
 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 */
@@ -7695,16 +7695,21 @@ static struct r5conf *setup_conf(struct mddev *mddev)
 	 * 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));
+	conf->shrinker = shrinker_alloc_and_init(raid5_cache_count,
+						 raid5_cache_scan, 128,
+						 DEFAULT_SEEKS * conf->raid_disks * 4,
+						 0, conf);
+	if (!conf->shrinker) {
+		pr_warn("md/raid:%s: couldn't allocate shrinker.\n",
+			mdname(mddev));
+		goto abort;
+	}
+
+	ret = register_shrinker(conf->shrinker, "md-raid5:%s", mdname(mddev));
 	if (ret) {
 		pr_warn("md/raid:%s: couldn't register shrinker.\n",
 			mdname(mddev));
-		goto abort;
+		goto abort_shrinker;
 	}
 
 	sprintf(pers_name, "raid%d", mddev->new_level);
@@ -7717,7 +7722,8 @@ static struct r5conf *setup_conf(struct mddev *mddev)
 	}
 
 	return conf;
-
+abort_shrinker:
+	shrinker_free(conf->shrinker);
  abort:
 	if (conf)
 		free_conf(conf);
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 6a92fafb0748..806f84681599 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -670,7 +670,7 @@ struct r5conf {
 	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;
-- 
2.30.2