diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 030012e1710c6f2fe919575f5deeb012f71d8fd5..72df63b0c79985deef815741b198ca78f84069cf 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1928,12 +1928,24 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
 	if (file->private_data)
 		btrfs_ioctl_trans_end(file);
 
+	/*
+	 * We use start here because we will need to wait on the IO to complete
+	 * in btrfs_sync_log, which could require joining a transaction (for
+	 * example checking cross references in the nocow path).  If we use join
+	 * here we could get into a situation where we're waiting on IO to
+	 * happen that is blocked on a transaction trying to commit.  With start
+	 * we inc the extwriter counter, so we wait for all extwriters to exit
+	 * before we start blocking join'ers.  This comment is to keep somebody
+	 * from thinking they are super smart and changing this to
+	 * btrfs_join_transaction *cough*Josef*cough*.
+	 */
 	trans = btrfs_start_transaction(root, 0);
 	if (IS_ERR(trans)) {
 		ret = PTR_ERR(trans);
 		mutex_unlock(&inode->i_mutex);
 		goto out;
 	}
+	trans->sync = true;
 
 	ret = btrfs_log_dentry_safe(trans, root, dentry);
 	if (ret < 0) {
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index da2ac4c6d78be306152e201401e5e07143e26b62..b16352ce0f73a7fe6662c9d078dda14585d68e0a 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -474,6 +474,7 @@ start_transaction(struct btrfs_root *root, u64 num_items, unsigned int type,
 	h->type = type;
 	h->allocating_chunk = false;
 	h->reloc_reserved = false;
+	h->sync = false;
 	INIT_LIST_HEAD(&h->qgroup_ref_list);
 	INIT_LIST_HEAD(&h->new_bgs);
 
@@ -713,7 +714,7 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 		btrfs_create_pending_block_groups(trans, root);
 
 	trans->delayed_ref_updates = 0;
-	if (btrfs_should_throttle_delayed_refs(trans, root)) {
+	if (!trans->sync && btrfs_should_throttle_delayed_refs(trans, root)) {
 		cur = max_t(unsigned long, cur, 1);
 		trans->delayed_ref_updates = 0;
 		btrfs_run_delayed_refs(trans, root, cur);
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index d05b6013fea88192aa63efa1bb73868b7f8dc69a..6ac037e9f9f0557524b7ed29b6b72a768f7a23cf 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -93,6 +93,7 @@ struct btrfs_trans_handle {
 	short adding_csums;
 	bool allocating_chunk;
 	bool reloc_reserved;
+	bool sync;
 	unsigned int type;
 	/*
 	 * this root is only needed to validate that the root passed to