bcachefs: Kill bch2_replicas_delta_list_marked()

This changes bch2_trans_fs_usage_apply() to handle failure (replicas
entry missing) by reverting the changes it made - meaning we can make
the main transaction commit path a bit slimmer, and perhaps also
simplify some locking in upcoming patches.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/btree_update_leaf.c

@@ -438,17 +438,6 @@ bch2_trans_commit_write_locked(struct btree_trans *trans,
 			marking = true;
 	}
 
-	if (marking) {
-		percpu_down_read(&c->mark_lock);
-	}
-
-	/* Must be called under mark_lock: */
-	if (marking && trans->fs_usage_deltas &&
-	    !bch2_replicas_delta_list_marked(c, trans->fs_usage_deltas)) {
-		ret = BTREE_INSERT_NEED_MARK_REPLICAS;
-		goto err;
-	}
-
 	/*
 	 * Don't get journal reservation until after we know insert will
 	 * succeed:
@@ -457,7 +446,7 @@ bch2_trans_commit_write_locked(struct btree_trans *trans,
 		ret = bch2_trans_journal_res_get(trans,
 				JOURNAL_RES_GET_NONBLOCK);
 		if (ret)
-			goto err;
+			return ret;
 	} else {
 		trans->journal_res.seq = c->journal.replay_journal_seq;
 	}
@@ -485,22 +474,27 @@ bch2_trans_commit_write_locked(struct btree_trans *trans,
 				i->k->k.version = MAX_VERSION;
 	}
 
+	if (marking)
+		percpu_down_read(&c->mark_lock);
+
+	if (marking && trans->fs_usage_deltas &&
+	    bch2_trans_fs_usage_apply(trans, trans->fs_usage_deltas)) {
+		percpu_up_read(&c->mark_lock);
+		return BTREE_INSERT_NEED_MARK_REPLICAS;
+	}
+
 	trans_for_each_update(trans, i)
 		if (BTREE_NODE_TYPE_HAS_MEM_TRIGGERS & (1U << i->bkey_type))
 			bch2_mark_update(trans, i->path, i->k, i->flags);
 
-	if (marking && trans->fs_usage_deltas)
-		bch2_trans_fs_usage_apply(trans, trans->fs_usage_deltas);
-
 	if (unlikely(c->gc_pos.phase))
 		bch2_trans_mark_gc(trans);
 
 	trans_for_each_update(trans, i)
 		do_btree_insert_one(trans, i);
-err:
-	if (marking) {
+
+	if (marking)
 		percpu_up_read(&c->mark_lock);
-	}
 
 	return ret;
 }

fs/bcachefs/buckets.c

@@ -1363,14 +1363,14 @@ void fs_usage_apply_warn(struct btree_trans *trans,
 	__WARN();
 }
 
-void bch2_trans_fs_usage_apply(struct btree_trans *trans,
-			       struct replicas_delta_list *deltas)
+int bch2_trans_fs_usage_apply(struct btree_trans *trans,
+			      struct replicas_delta_list *deltas)
 {
 	struct bch_fs *c = trans->c;
 	static int warned_disk_usage = 0;
 	bool warn = false;
 	unsigned disk_res_sectors = trans->disk_res ? trans->disk_res->sectors : 0;
-	struct replicas_delta *d = deltas->d;
+	struct replicas_delta *d = deltas->d, *d2;
 	struct replicas_delta *top = (void *) deltas->d + deltas->used;
 	struct bch_fs_usage *dst;
 	s64 added = 0, should_not_have_added;
@@ -1389,7 +1389,8 @@ void bch2_trans_fs_usage_apply(struct btree_trans *trans,
 			added += d->delta;
 		}
 
-		BUG_ON(__update_replicas(c, dst, &d->r, d->delta));
+		if (__update_replicas(c, dst, &d->r, d->delta))
+			goto need_mark;
 	}
 
 	dst->nr_inodes += deltas->nr_inodes;
@@ -1427,6 +1428,14 @@ void bch2_trans_fs_usage_apply(struct btree_trans *trans,
 
 	if (unlikely(warn) && !xchg(&warned_disk_usage, 1))
 		fs_usage_apply_warn(trans, disk_res_sectors, should_not_have_added);
+	return 0;
+need_mark:
+	/* revert changes: */
+	for (d2 = deltas->d; d2 != d; d2 = replicas_delta_next(d2))
+		BUG_ON(__update_replicas(c, dst, &d2->r, -d2->delta));
+
+	preempt_enable();
+	return -1;
 }
 
 /* trans_mark: */

fs/bcachefs/buckets.h

@@ -233,7 +233,7 @@ int bch2_mark_update(struct btree_trans *, struct btree_path *,
 
 int bch2_trans_mark_key(struct btree_trans *, struct bkey_s_c,
 			struct bkey_s_c, unsigned);
-void bch2_trans_fs_usage_apply(struct btree_trans *, struct replicas_delta_list *);
+int bch2_trans_fs_usage_apply(struct btree_trans *, struct replicas_delta_list *);
 
 int bch2_trans_mark_metadata_bucket(struct btree_trans *, struct bch_dev *,
 				    size_t, enum bch_data_type, unsigned);

fs/bcachefs/replicas.c

@@ -475,20 +475,6 @@ static int __bch2_mark_bkey_replicas(struct bch_fs *c, struct bkey_s_c k,
 
 /* replicas delta list: */
 
-bool bch2_replicas_delta_list_marked(struct bch_fs *c,
-				     struct replicas_delta_list *r)
-{
-	struct replicas_delta *d = r->d;
-	struct replicas_delta *top = (void *) r->d + r->used;
-
-	percpu_rwsem_assert_held(&c->mark_lock);
-
-	for (d = r->d; d != top; d = replicas_delta_next(d))
-		if (bch2_replicas_entry_idx(c, &d->r) < 0)
-			return false;
-	return true;
-}
-
 int bch2_replicas_delta_list_mark(struct bch_fs *c,
 				  struct replicas_delta_list *r)
 {

fs/bcachefs/replicas.h

@@ -48,7 +48,6 @@ replicas_delta_next(struct replicas_delta *d)
 	return (void *) d + replicas_entry_bytes(&d->r) + 8;
 }
 
-bool bch2_replicas_delta_list_marked(struct bch_fs *, struct replicas_delta_list *);
 int bch2_replicas_delta_list_mark(struct bch_fs *, struct replicas_delta_list *);
 
 void bch2_bkey_to_replicas(struct bch_replicas_entry *, struct bkey_s_c);