bcachefs: Switch replicas to mark_lock

Prep work for upcoming disk accounting changes
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bcachefs.h

@@ -528,8 +528,8 @@ struct bch_fs {
 
 	struct bch_dev __rcu	*devs[BCH_SB_MEMBERS_MAX];
 
-	struct bch_replicas_cpu __rcu *replicas;
-	struct bch_replicas_cpu __rcu *replicas_gc;
+	struct bch_replicas_cpu replicas;
+	struct bch_replicas_cpu replicas_gc;
 	struct mutex		replicas_gc_lock;
 
 	struct bch_disk_groups_cpu __rcu *disk_groups;

fs/bcachefs/recovery.c

@@ -131,8 +131,7 @@ int bch2_fs_recovery(struct bch_fs *c)
 	int ret;
 
 	mutex_lock(&c->sb_lock);
-	if (!rcu_dereference_protected(c->replicas,
-			lockdep_is_held(&c->sb_lock))->nr) {
+	if (!c->replicas.entries) {
 		bch_info(c, "building replicas info");
 		set_bit(BCH_FS_REBUILD_REPLICAS, &c->flags);
 	}

fs/bcachefs/replicas_types.h

@@ -2,10 +2,9 @@
 #define _BCACHEFS_REPLICAS_TYPES_H
 
 struct bch_replicas_cpu {
-	struct rcu_head		rcu;
 	unsigned		nr;
 	unsigned		entry_size;
-	struct bch_replicas_entry entries[];
+	struct bch_replicas_entry *entries;
 };
 
 #endif /* _BCACHEFS_REPLICAS_TYPES_H */

fs/bcachefs/super.c

@@ -383,7 +383,8 @@ static void bch2_fs_free(struct bch_fs *c)
 	mempool_exit(&c->btree_reserve_pool);
 	mempool_exit(&c->fill_iter);
 	percpu_ref_exit(&c->writes);
-	kfree(rcu_dereference_protected(c->replicas, 1));
+	kfree(c->replicas.entries);
+	kfree(c->replicas_gc.entries);
 	kfree(rcu_dereference_protected(c->disk_groups, 1));
 
 	if (c->copygc_wq)
@@ -565,6 +566,9 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
 
 	bch2_fs_btree_cache_init_early(&c->btree_cache);
 
+	if (percpu_init_rwsem(&c->mark_lock))
+		goto err;
+
 	mutex_lock(&c->sb_lock);
 
 	if (bch2_sb_to_fs(c, sb)) {
@@ -608,7 +612,6 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
 			    offsetof(struct btree_write_bio, wbio.bio)),
 			BIOSET_NEED_BVECS) ||
 	    !(c->usage[0] = alloc_percpu(struct bch_fs_usage)) ||
-	    percpu_init_rwsem(&c->mark_lock) ||
 	    mempool_init_kvpmalloc_pool(&c->btree_bounce_pool, 1,
 					btree_bytes(c)) ||
 	    mempool_init_kmalloc_pool(&c->btree_iters_pool, 1,