bcachefs: Handle btree node rewrites before going RW

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

fs/bcachefs/bcachefs.h

@@ -780,6 +780,9 @@ struct bch_fs {
 	struct workqueue_struct	*btree_interior_update_worker;
 	struct work_struct	btree_interior_update_work;
 
+	struct list_head	pending_node_rewrites;
+	struct mutex		pending_node_rewrites_lock;
+
 	/* btree_io.c: */
 	spinlock_t		btree_write_error_lock;
 	struct btree_write_stats {

fs/bcachefs/btree_update_interior.c

@@ -1998,6 +1998,7 @@ int bch2_btree_node_rewrite(struct btree_trans *trans,
 struct async_btree_rewrite {
 	struct bch_fs		*c;
 	struct work_struct	work;
+	struct list_head	list;
 	enum btree_id		btree_id;
 	unsigned		level;
 	struct bpos		pos;
@@ -2057,15 +2058,10 @@ void async_btree_node_rewrite_work(struct work_struct *work)
 void bch2_btree_node_rewrite_async(struct bch_fs *c, struct btree *b)
 {
 	struct async_btree_rewrite *a;
-
-	if (!bch2_write_ref_tryget(c, BCH_WRITE_REF_node_rewrite)) {
-		bch_err(c, "%s: error getting c->writes ref", __func__);
-		return;
-	}
+	int ret;
 
 	a = kmalloc(sizeof(*a), GFP_NOFS);
 	if (!a) {
-		bch2_write_ref_put(c, BCH_WRITE_REF_node_rewrite);
 		bch_err(c, "%s: error allocating memory", __func__);
 		return;
 	}
@@ -2075,11 +2071,63 @@ void bch2_btree_node_rewrite_async(struct bch_fs *c, struct btree *b)
 	a->level	= b->c.level;
 	a->pos		= b->key.k.p;
 	a->seq		= b->data->keys.seq;
-
 	INIT_WORK(&a->work, async_btree_node_rewrite_work);
+
+	if (unlikely(!test_bit(BCH_FS_MAY_GO_RW, &c->flags))) {
+		mutex_lock(&c->pending_node_rewrites_lock);
+		list_add(&a->list, &c->pending_node_rewrites);
+		mutex_unlock(&c->pending_node_rewrites_lock);
+		return;
+	}
+
+	if (!bch2_write_ref_tryget(c, BCH_WRITE_REF_node_rewrite)) {
+		if (test_bit(BCH_FS_STARTED, &c->flags)) {
+			bch_err(c, "%s: error getting c->writes ref", __func__);
+			kfree(a);
+			return;
+		}
+
+		ret = bch2_fs_read_write_early(c);
+		if (ret) {
+			bch_err(c, "%s: error going read-write: %s",
+				__func__, bch2_err_str(ret));
+			kfree(a);
+			return;
+		}
+
+		bch2_write_ref_get(c, BCH_WRITE_REF_node_rewrite);
+	}
+
 	queue_work(c->btree_interior_update_worker, &a->work);
 }
 
+void bch2_do_pending_node_rewrites(struct bch_fs *c)
+{
+	struct async_btree_rewrite *a, *n;
+
+	mutex_lock(&c->pending_node_rewrites_lock);
+	list_for_each_entry_safe(a, n, &c->pending_node_rewrites, list) {
+		list_del(&a->list);
+
+		bch2_write_ref_get(c, BCH_WRITE_REF_node_rewrite);
+		queue_work(c->btree_interior_update_worker, &a->work);
+	}
+	mutex_unlock(&c->pending_node_rewrites_lock);
+}
+
+void bch2_free_pending_node_rewrites(struct bch_fs *c)
+{
+	struct async_btree_rewrite *a, *n;
+
+	mutex_lock(&c->pending_node_rewrites_lock);
+	list_for_each_entry_safe(a, n, &c->pending_node_rewrites, list) {
+		list_del(&a->list);
+
+		kfree(a);
+	}
+	mutex_unlock(&c->pending_node_rewrites_lock);
+}
+
 static int __bch2_btree_node_update_key(struct btree_trans *trans,
 					struct btree_iter *iter,
 					struct btree *b, struct btree *new_hash,
@@ -2417,6 +2465,9 @@ int bch2_fs_btree_interior_update_init(struct bch_fs *c)
 	mutex_init(&c->btree_interior_update_lock);
 	INIT_WORK(&c->btree_interior_update_work, btree_interior_update_work);
 
+	INIT_LIST_HEAD(&c->pending_node_rewrites);
+	mutex_init(&c->pending_node_rewrites_lock);
+
 	c->btree_interior_update_worker =
 		alloc_workqueue("btree_update", WQ_UNBOUND|WQ_MEM_RECLAIM, 1);
 	if (!c->btree_interior_update_worker)

fs/bcachefs/btree_update_interior.h

@@ -318,6 +318,9 @@ void bch2_journal_entries_to_btree_roots(struct bch_fs *, struct jset *);
 struct jset_entry *bch2_btree_roots_to_journal_entries(struct bch_fs *,
 					struct jset_entry *, struct jset_entry *);
 
+void bch2_do_pending_node_rewrites(struct bch_fs *);
+void bch2_free_pending_node_rewrites(struct bch_fs *);
+
 void bch2_fs_btree_interior_update_exit(struct bch_fs *);
 int bch2_fs_btree_interior_update_init(struct bch_fs *);
 

fs/bcachefs/super.c

@@ -418,6 +418,7 @@ static int __bch2_fs_read_write(struct bch_fs *c, bool early)
 	bch2_do_discards(c);
 	bch2_do_invalidates(c);
 	bch2_do_stripe_deletes(c);
+	bch2_do_pending_node_rewrites(c);
 	return 0;
 err:
 	__bch2_fs_read_only(c);
@@ -446,6 +447,7 @@ static void __bch2_fs_free(struct bch_fs *c)
 	for (i = 0; i < BCH_TIME_STAT_NR; i++)
 		bch2_time_stats_exit(&c->times[i]);
 
+	bch2_free_pending_node_rewrites(c);
 	bch2_fs_counters_exit(c);
 	bch2_fs_snapshots_exit(c);
 	bch2_fs_quota_exit(c);