bcachefs: Rip out freelists from btree key cache

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_key_cache_types.h

@@ -2,33 +2,19 @@
 #ifndef _BCACHEFS_BTREE_KEY_CACHE_TYPES_H
 #define _BCACHEFS_BTREE_KEY_CACHE_TYPES_H
 
-struct btree_key_cache_freelist {
-	struct bkey_cached	*objs[16];
-	unsigned		nr;
-};
-
 struct btree_key_cache {
-	struct mutex		lock;
 	struct rhashtable	table;
 	bool			table_init_done;
 
-	struct list_head	freed_pcpu;
-	size_t			nr_freed_pcpu;
-	struct list_head	freed_nonpcpu;
-	size_t			nr_freed_nonpcpu;
-
 	struct shrinker		*shrink;
 	unsigned		shrink_iter;
-	struct btree_key_cache_freelist __percpu *pcpu_freed;
 
-	atomic_long_t		nr_freed;
 	atomic_long_t		nr_keys;
 	atomic_long_t		nr_dirty;
 
 	/* shrinker stats */
 	unsigned long		requested_to_free;
 	unsigned long		freed;
-	unsigned long		moved_to_freelist;
 	unsigned long		skipped_dirty;
 	unsigned long		skipped_accessed;
 	unsigned long		skipped_lock_fail;

fs/bcachefs/btree_types.h

@@ -386,17 +386,17 @@ struct bkey_cached {
 	struct btree_bkey_cached_common c;
 
 	unsigned long		flags;
-	unsigned long		btree_trans_barrier_seq;
 	u16			u64s;
 	struct bkey_cached_key	key;
 
 	struct rhash_head	hash;
-	struct list_head	list;
 
 	struct journal_entry_pin journal;
 	u64			seq;
 
 	struct bkey_i		*k;
+
+	struct rcu_head		rcu;
 };
 
 static inline struct bpos btree_node_pos(struct btree_bkey_cached_common *b)