bcachefs: Enable automatic shrinking for rhashtables

Since the key cache shrinker walks the rhashtable, a mostly empty
rhashtable leads to really nasty reclaim performance issues.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_cache.c

@@ -91,10 +91,11 @@ static int bch2_btree_cache_cmp_fn(struct rhashtable_compare_arg *arg,
 }
 
 static const struct rhashtable_params bch_btree_cache_params = {
-	.head_offset	= offsetof(struct btree, hash),
-	.key_offset	= offsetof(struct btree, hash_val),
-	.key_len	= sizeof(u64),
-	.obj_cmpfn	= bch2_btree_cache_cmp_fn,
+	.head_offset		= offsetof(struct btree, hash),
+	.key_offset		= offsetof(struct btree, hash_val),
+	.key_len		= sizeof(u64),
+	.obj_cmpfn		= bch2_btree_cache_cmp_fn,
+	.automatic_shrinking	= true,
 };
 
 static int btree_node_data_alloc(struct bch_fs *c, struct btree *b, gfp_t gfp)

fs/bcachefs/btree_key_cache.c

@@ -32,10 +32,11 @@ static int bch2_btree_key_cache_cmp_fn(struct rhashtable_compare_arg *arg,
 }
 
 static const struct rhashtable_params bch2_btree_key_cache_params = {
-	.head_offset	= offsetof(struct bkey_cached, hash),
-	.key_offset	= offsetof(struct bkey_cached, key),
-	.key_len	= sizeof(struct bkey_cached_key),
-	.obj_cmpfn	= bch2_btree_key_cache_cmp_fn,
+	.head_offset		= offsetof(struct bkey_cached, hash),
+	.key_offset		= offsetof(struct bkey_cached, key),
+	.key_len		= sizeof(struct bkey_cached_key),
+	.obj_cmpfn		= bch2_btree_key_cache_cmp_fn,
+	.automatic_shrinking	= true,
 };
 
 __flatten

fs/bcachefs/io_read.c

@@ -84,9 +84,10 @@ struct promote_op {
 };
 
 static const struct rhashtable_params bch_promote_params = {
-	.head_offset	= offsetof(struct promote_op, hash),
-	.key_offset	= offsetof(struct promote_op, pos),
-	.key_len	= sizeof(struct bpos),
+	.head_offset		= offsetof(struct promote_op, hash),
+	.key_offset		= offsetof(struct promote_op, pos),
+	.key_len		= sizeof(struct bpos),
+	.automatic_shrinking	= true,
 };
 
 static inline int should_promote(struct bch_fs *c, struct bkey_s_c k,

fs/bcachefs/movinggc.c

@@ -35,9 +35,10 @@ struct buckets_in_flight {
 };
 
 static const struct rhashtable_params bch_move_bucket_params = {
-	.head_offset	= offsetof(struct move_bucket_in_flight, hash),
-	.key_offset	= offsetof(struct move_bucket_in_flight, bucket.k),
-	.key_len	= sizeof(struct move_bucket_key),
+	.head_offset		= offsetof(struct move_bucket_in_flight, hash),
+	.key_offset		= offsetof(struct move_bucket_in_flight, bucket.k),
+	.key_len		= sizeof(struct move_bucket_key),
+	.automatic_shrinking	= true,
 };
 
 static struct move_bucket_in_flight *