[PATCH v2 28/47] bcache: dynamically allocate the md-bcache shrinker

[Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>]

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

Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
---
 drivers/md/bcache/bcache.h |  2 +-
 drivers/md/bcache/btree.c  | 27 ++++++++++++++++-----------
 drivers/md/bcache/sysfs.c  |  3 ++-
 3 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 5a79bb3c272f..c622bc50f81b 100644
--- a/drivers/md/bcache/bcache.h
+++ b/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;
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index fd121a61f17c..c176c7fc77d9 100644
--- a/drivers/md/bcache/btree.c
+++ b/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_unregister(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 -ENOMEM;
+       }
+
+       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;
 
-       if (register_shrinker(&c->shrink, "md-bcache:%pU", c->set_uuid))
-               pr_warn("bcache: %s: could not register shrinker\n",
-                               __func__);
+       shrinker_register(c->shrink);
 
        return 0;
 }
diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 0e2c1880f60b..45d8af755de6 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/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,
-- 
2.30.2