diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 1df0d9d..83051fa 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1491,6 +1491,12 @@
 	struct mutex chunk_mutex;
 	struct mutex volume_mutex;
 
+	/*
+	 * this is taken to make sure we don't set block groups ro after
+	 * the free space cache has been allocated on them
+	 */
+	struct mutex ro_block_group_mutex;
+
 	/* this is used during read/modify/write to make sure
 	 * no two ios are trying to mod the same stripe at the same
 	 * time
@@ -3407,6 +3413,8 @@
 			 u64 bytenr, u64 num_bytes, u64 parent,
 			 u64 root_objectid, u64 owner, u64 offset, int no_quota);
 
+int btrfs_start_dirty_block_groups(struct btrfs_trans_handle *trans,
+				   struct btrfs_root *root);
 int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
 				    struct btrfs_root *root);
 int btrfs_setup_space_cache(struct btrfs_trans_handle *trans,
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 568cc4e..b5e3d5f 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2572,6 +2572,7 @@
 	mutex_init(&fs_info->transaction_kthread_mutex);
 	mutex_init(&fs_info->cleaner_mutex);
 	mutex_init(&fs_info->volume_mutex);
+	mutex_init(&fs_info->ro_block_group_mutex);
 	init_rwsem(&fs_info->commit_root_sem);
 	init_rwsem(&fs_info->cleanup_work_sem);
 	init_rwsem(&fs_info->subvol_sem);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 40c9513..02c2b29 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3298,7 +3298,7 @@
 		if (ret)
 			goto out_put;
 
-		ret = btrfs_truncate_free_space_cache(root, trans, inode);
+		ret = btrfs_truncate_free_space_cache(root, trans, NULL, inode);
 		if (ret)
 			goto out_put;
 	}
@@ -3382,6 +3382,146 @@
 	return 0;
 }
 
+/*
+ * transaction commit does final block group cache writeback during a
+ * critical section where nothing is allowed to change the FS.  This is
+ * required in order for the cache to actually match the block group,
+ * but can introduce a lot of latency into the commit.
+ *
+ * So, btrfs_start_dirty_block_groups is here to kick off block group
+ * cache IO.  There's a chance we'll have to redo some of it if the
+ * block group changes again during the commit, but it greatly reduces
+ * the commit latency by getting rid of the easy block groups while
+ * we're still allowing others to join the commit.
+ */
+int btrfs_start_dirty_block_groups(struct btrfs_trans_handle *trans,
+				   struct btrfs_root *root)
+{
+	struct btrfs_block_group_cache *cache;
+	struct btrfs_transaction *cur_trans = trans->transaction;
+	int ret = 0;
+	int should_put;
+	struct btrfs_path *path = NULL;
+	LIST_HEAD(dirty);
+	struct list_head *io = &cur_trans->io_bgs;
+	int num_started = 0;
+	int loops = 0;
+
+	spin_lock(&cur_trans->dirty_bgs_lock);
+	if (!list_empty(&cur_trans->dirty_bgs)) {
+		list_splice_init(&cur_trans->dirty_bgs, &dirty);
+	}
+	spin_unlock(&cur_trans->dirty_bgs_lock);
+
+again:
+	if (list_empty(&dirty)) {
+		btrfs_free_path(path);
+		return 0;
+	}
+
+	/*
+	 * make sure all the block groups on our dirty list actually
+	 * exist
+	 */
+	btrfs_create_pending_block_groups(trans, root);
+
+	if (!path) {
+		path = btrfs_alloc_path();
+		if (!path)
+			return -ENOMEM;
+	}
+
+	while (!list_empty(&dirty)) {
+		cache = list_first_entry(&dirty,
+					 struct btrfs_block_group_cache,
+					 dirty_list);
+
+		/*
+		 * cache_write_mutex is here only to save us from balance
+		 * deleting this block group while we are writing out the
+		 * cache
+		 */
+		mutex_lock(&trans->transaction->cache_write_mutex);
+
+		/*
+		 * this can happen if something re-dirties a block
+		 * group that is already under IO.  Just wait for it to
+		 * finish and then do it all again
+		 */
+		if (!list_empty(&cache->io_list)) {
+			list_del_init(&cache->io_list);
+			btrfs_wait_cache_io(root, trans, cache,
+					    &cache->io_ctl, path,
+					    cache->key.objectid);
+			btrfs_put_block_group(cache);
+		}
+
+
+		/*
+		 * btrfs_wait_cache_io uses the cache->dirty_list to decide
+		 * if it should update the cache_state.  Don't delete
+		 * until after we wait.
+		 *
+		 * Since we're not running in the commit critical section
+		 * we need the dirty_bgs_lock to protect from update_block_group
+		 */
+		spin_lock(&cur_trans->dirty_bgs_lock);
+		list_del_init(&cache->dirty_list);
+		spin_unlock(&cur_trans->dirty_bgs_lock);
+
+		should_put = 1;
+
+		cache_save_setup(cache, trans, path);
+
+		if (cache->disk_cache_state == BTRFS_DC_SETUP) {
+			cache->io_ctl.inode = NULL;
+			ret = btrfs_write_out_cache(root, trans, cache, path);
+			if (ret == 0 && cache->io_ctl.inode) {
+				num_started++;
+				should_put = 0;
+
+				/*
+				 * the cache_write_mutex is protecting
+				 * the io_list
+				 */
+				list_add_tail(&cache->io_list, io);
+			} else {
+				/*
+				 * if we failed to write the cache, the
+				 * generation will be bad and life goes on
+				 */
+				ret = 0;
+			}
+		}
+		if (!ret)
+			ret = write_one_cache_group(trans, root, path, cache);
+		mutex_unlock(&trans->transaction->cache_write_mutex);
+
+		/* if its not on the io list, we need to put the block group */
+		if (should_put)
+			btrfs_put_block_group(cache);
+
+		if (ret)
+			break;
+	}
+
+	/*
+	 * go through delayed refs for all the stuff we've just kicked off
+	 * and then loop back (just once)
+	 */
+	ret = btrfs_run_delayed_refs(trans, root, 0);
+	if (!ret && loops == 0) {
+		loops++;
+		spin_lock(&cur_trans->dirty_bgs_lock);
+		list_splice_init(&cur_trans->dirty_bgs, &dirty);
+		spin_unlock(&cur_trans->dirty_bgs_lock);
+		goto again;
+	}
+
+	btrfs_free_path(path);
+	return ret;
+}
+
 int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
 				   struct btrfs_root *root)
 {
@@ -3390,12 +3530,8 @@
 	int ret = 0;
 	int should_put;
 	struct btrfs_path *path;
-	LIST_HEAD(io);
+	struct list_head *io = &cur_trans->io_bgs;
 	int num_started = 0;
-	int num_waited = 0;
-
-	if (list_empty(&cur_trans->dirty_bgs))
-		return 0;
 
 	path = btrfs_alloc_path();
 	if (!path)
@@ -3423,14 +3559,16 @@
 					    &cache->io_ctl, path,
 					    cache->key.objectid);
 			btrfs_put_block_group(cache);
-			num_waited++;
 		}
 
+		/*
+		 * don't remove from the dirty list until after we've waited
+		 * on any pending IO
+		 */
 		list_del_init(&cache->dirty_list);
 		should_put = 1;
 
-		if (cache->disk_cache_state == BTRFS_DC_CLEAR)
-			cache_save_setup(cache, trans, path);
+		cache_save_setup(cache, trans, path);
 
 		if (!ret)
 			ret = btrfs_run_delayed_refs(trans, root, (unsigned long) -1);
@@ -3441,7 +3579,7 @@
 			if (ret == 0 && cache->io_ctl.inode) {
 				num_started++;
 				should_put = 0;
-				list_add_tail(&cache->io_list, &io);
+				list_add_tail(&cache->io_list, io);
 			} else {
 				/*
 				 * if we failed to write the cache, the
@@ -3458,11 +3596,10 @@
 			btrfs_put_block_group(cache);
 	}
 
-	while (!list_empty(&io)) {
-		cache = list_first_entry(&io, struct btrfs_block_group_cache,
+	while (!list_empty(io)) {
+		cache = list_first_entry(io, struct btrfs_block_group_cache,
 					 io_list);
 		list_del_init(&cache->io_list);
-		num_waited++;
 		btrfs_wait_cache_io(root, trans, cache,
 				    &cache->io_ctl, path, cache->key.objectid);
 		btrfs_put_block_group(cache);
@@ -5459,15 +5596,6 @@
 		if (!alloc && cache->cached == BTRFS_CACHE_NO)
 			cache_block_group(cache, 1);
 
-		spin_lock(&trans->transaction->dirty_bgs_lock);
-		if (list_empty(&cache->dirty_list)) {
-			list_add_tail(&cache->dirty_list,
-				      &trans->transaction->dirty_bgs);
-				trans->transaction->num_dirty_bgs++;
-			btrfs_get_block_group(cache);
-		}
-		spin_unlock(&trans->transaction->dirty_bgs_lock);
-
 		byte_in_group = bytenr - cache->key.objectid;
 		WARN_ON(byte_in_group > cache->key.offset);
 
@@ -5516,6 +5644,16 @@
 				spin_unlock(&info->unused_bgs_lock);
 			}
 		}
+
+		spin_lock(&trans->transaction->dirty_bgs_lock);
+		if (list_empty(&cache->dirty_list)) {
+			list_add_tail(&cache->dirty_list,
+				      &trans->transaction->dirty_bgs);
+				trans->transaction->num_dirty_bgs++;
+			btrfs_get_block_group(cache);
+		}
+		spin_unlock(&trans->transaction->dirty_bgs_lock);
+
 		btrfs_put_block_group(cache);
 		total -= num_bytes;
 		bytenr += num_bytes;
@@ -8602,10 +8740,30 @@
 
 	BUG_ON(cache->ro);
 
+again:
 	trans = btrfs_join_transaction(root);
 	if (IS_ERR(trans))
 		return PTR_ERR(trans);
 
+	/*
+	 * we're not allowed to set block groups readonly after the dirty
+	 * block groups cache has started writing.  If it already started,
+	 * back off and let this transaction commit
+	 */
+	mutex_lock(&root->fs_info->ro_block_group_mutex);
+	if (trans->transaction->dirty_bg_run) {
+		u64 transid = trans->transid;
+
+		mutex_unlock(&root->fs_info->ro_block_group_mutex);
+		btrfs_end_transaction(trans, root);
+
+		ret = btrfs_wait_for_commit(root, transid);
+		if (ret)
+			return ret;
+		goto again;
+	}
+
+
 	ret = set_block_group_ro(cache, 0);
 	if (!ret)
 		goto out;
@@ -8620,6 +8778,7 @@
 		alloc_flags = update_block_group_flags(root, cache->flags);
 		check_system_chunk(trans, root, alloc_flags);
 	}
+	mutex_unlock(&root->fs_info->ro_block_group_mutex);
 
 	btrfs_end_transaction(trans, root);
 	return ret;
@@ -9425,7 +9584,38 @@
 		goto out;
 	}
 
+	/*
+	 * get the inode first so any iput calls done for the io_list
+	 * aren't the final iput (no unlinks allowed now)
+	 */
 	inode = lookup_free_space_inode(tree_root, block_group, path);
+
+	mutex_lock(&trans->transaction->cache_write_mutex);
+	/*
+	 * make sure our free spache cache IO is done before remove the
+	 * free space inode
+	 */
+	spin_lock(&trans->transaction->dirty_bgs_lock);
+	if (!list_empty(&block_group->io_list)) {
+		list_del_init(&block_group->io_list);
+
+		WARN_ON(!IS_ERR(inode) && inode != block_group->io_ctl.inode);
+
+		spin_unlock(&trans->transaction->dirty_bgs_lock);
+		btrfs_wait_cache_io(root, trans, block_group,
+				    &block_group->io_ctl, path,
+				    block_group->key.objectid);
+		btrfs_put_block_group(block_group);
+		spin_lock(&trans->transaction->dirty_bgs_lock);
+	}
+
+	if (!list_empty(&block_group->dirty_list)) {
+		list_del_init(&block_group->dirty_list);
+		btrfs_put_block_group(block_group);
+	}
+	spin_unlock(&trans->transaction->dirty_bgs_lock);
+	mutex_unlock(&trans->transaction->cache_write_mutex);
+
 	if (!IS_ERR(inode)) {
 		ret = btrfs_orphan_add(trans, inode);
 		if (ret) {
@@ -9518,11 +9708,12 @@
 
 	spin_lock(&trans->transaction->dirty_bgs_lock);
 	if (!list_empty(&block_group->dirty_list)) {
-		list_del_init(&block_group->dirty_list);
-		btrfs_put_block_group(block_group);
+		WARN_ON(1);
+	}
+	if (!list_empty(&block_group->io_list)) {
+		WARN_ON(1);
 	}
 	spin_unlock(&trans->transaction->dirty_bgs_lock);
-
 	btrfs_remove_free_space_cache(block_group);
 
 	spin_lock(&block_group->space_info->lock);
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 83532a2..253cb74 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -226,9 +226,37 @@
 
 int btrfs_truncate_free_space_cache(struct btrfs_root *root,
 				    struct btrfs_trans_handle *trans,
+				    struct btrfs_block_group_cache *block_group,
 				    struct inode *inode)
 {
 	int ret = 0;
+	struct btrfs_path *path = btrfs_alloc_path();
+
+	if (!path) {
+		ret = -ENOMEM;
+		goto fail;
+	}
+
+	if (block_group) {
+		mutex_lock(&trans->transaction->cache_write_mutex);
+		if (!list_empty(&block_group->io_list)) {
+			list_del_init(&block_group->io_list);
+
+			btrfs_wait_cache_io(root, trans, block_group,
+					    &block_group->io_ctl, path,
+					    block_group->key.objectid);
+			btrfs_put_block_group(block_group);
+		}
+
+		/*
+		 * now that we've truncated the cache away, its no longer
+		 * setup or written
+		 */
+		spin_lock(&block_group->lock);
+		block_group->disk_cache_state = BTRFS_DC_CLEAR;
+		spin_unlock(&block_group->lock);
+	}
+	btrfs_free_path(path);
 
 	btrfs_i_size_write(inode, 0);
 	truncate_pagecache(inode, 0);
@@ -242,11 +270,17 @@
 	ret = btrfs_truncate_inode_items(trans, root, inode,
 					 0, BTRFS_EXTENT_DATA_KEY);
 	if (ret) {
+		mutex_unlock(&trans->transaction->cache_write_mutex);
 		btrfs_abort_transaction(trans, root, ret);
 		return ret;
 	}
 
 	ret = btrfs_update_inode(trans, root, inode);
+
+	if (block_group)
+		mutex_unlock(&trans->transaction->cache_write_mutex);
+
+fail:
 	if (ret)
 		btrfs_abort_transaction(trans, root, ret);
 
@@ -876,6 +910,7 @@
 {
 	int ret;
 	struct btrfs_free_cluster *cluster = NULL;
+	struct btrfs_free_cluster *cluster_locked = NULL;
 	struct rb_node *node = rb_first(&ctl->free_space_offset);
 	struct btrfs_trim_range *trim_entry;
 
@@ -887,6 +922,8 @@
 	}
 
 	if (!node && cluster) {
+		cluster_locked = cluster;
+		spin_lock(&cluster_locked->lock);
 		node = rb_first(&cluster->root);
 		cluster = NULL;
 	}
@@ -910,9 +947,15 @@
 		node = rb_next(node);
 		if (!node && cluster) {
 			node = rb_first(&cluster->root);
+			cluster_locked = cluster;
+			spin_lock(&cluster_locked->lock);
 			cluster = NULL;
 		}
 	}
+	if (cluster_locked) {
+		spin_unlock(&cluster_locked->lock);
+		cluster_locked = NULL;
+	}
 
 	/*
 	 * Make sure we don't miss any range that was removed from our rbtree
@@ -930,6 +973,8 @@
 
 	return 0;
 fail:
+	if (cluster_locked)
+		spin_unlock(&cluster_locked->lock);
 	return -ENOSPC;
 }
 
@@ -1101,6 +1146,9 @@
 	int ret;
 	struct inode *inode = io_ctl->inode;
 
+	if (!inode)
+		return 0;
+
 	root = root->fs_info->tree_root;
 
 	/* Flush the dirty pages in the cache file. */
@@ -1127,11 +1175,16 @@
 	btrfs_update_inode(trans, root, inode);
 
 	if (block_group) {
+		/* the dirty list is protected by the dirty_bgs_lock */
+		spin_lock(&trans->transaction->dirty_bgs_lock);
+
+		/* the disk_cache_state is protected by the block group lock */
 		spin_lock(&block_group->lock);
 
 		/*
 		 * only mark this as written if we didn't get put back on
-		 * the dirty list while waiting for IO.
+		 * the dirty list while waiting for IO.   Otherwise our
+		 * cache state won't be right, and we won't get written again
 		 */
 		if (!ret && list_empty(&block_group->dirty_list))
 			block_group->disk_cache_state = BTRFS_DC_WRITTEN;
@@ -1139,6 +1192,7 @@
 			block_group->disk_cache_state = BTRFS_DC_ERROR;
 
 		spin_unlock(&block_group->lock);
+		spin_unlock(&trans->transaction->dirty_bgs_lock);
 		io_ctl->inode = NULL;
 		iput(inode);
 	}
@@ -1207,9 +1261,11 @@
 
 	mutex_lock(&ctl->cache_writeout_mutex);
 	/* Write out the extent entries in the free space cache */
+	spin_lock(&ctl->tree_lock);
 	ret = write_cache_extent_entries(io_ctl, ctl,
 					 block_group, &entries, &bitmaps,
 					 &bitmap_list);
+	spin_unlock(&ctl->tree_lock);
 	if (ret) {
 		mutex_unlock(&ctl->cache_writeout_mutex);
 		goto out_nospc;
@@ -1219,6 +1275,9 @@
 	 * Some spaces that are freed in the current transaction are pinned,
 	 * they will be added into free space cache after the transaction is
 	 * committed, we shouldn't lose them.
+	 *
+	 * If this changes while we are working we'll get added back to
+	 * the dirty list and redo it.  No locking needed
 	 */
 	ret = write_pinned_extent_entries(root, block_group, io_ctl, &entries);
 	if (ret) {
@@ -1231,7 +1290,9 @@
 	 * locked while doing it because a concurrent trim can be manipulating
 	 * or freeing the bitmap.
 	 */
+	spin_lock(&ctl->tree_lock);
 	ret = write_bitmap_entries(io_ctl, &bitmap_list);
+	spin_unlock(&ctl->tree_lock);
 	mutex_unlock(&ctl->cache_writeout_mutex);
 	if (ret)
 		goto out_nospc;
@@ -1307,12 +1368,6 @@
 		spin_unlock(&block_group->lock);
 		return 0;
 	}
-
-	if (block_group->delalloc_bytes) {
-		block_group->disk_cache_state = BTRFS_DC_WRITTEN;
-		spin_unlock(&block_group->lock);
-		return 0;
-	}
 	spin_unlock(&block_group->lock);
 
 	inode = lookup_free_space_inode(root, block_group, path);
diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index c433986..a16a029 100644
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -62,6 +62,7 @@
 				       struct btrfs_block_rsv *rsv);
 int btrfs_truncate_free_space_cache(struct btrfs_root *root,
 				    struct btrfs_trans_handle *trans,
+				    struct btrfs_block_group_cache *block_group,
 				    struct inode *inode);
 int load_free_space_cache(struct btrfs_fs_info *fs_info,
 			  struct btrfs_block_group_cache *block_group);
diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index 74faea3a..f6a596d 100644
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -456,7 +456,7 @@
 	}
 
 	if (i_size_read(inode) > 0) {
-		ret = btrfs_truncate_free_space_cache(root, trans, inode);
+		ret = btrfs_truncate_free_space_cache(root, trans, NULL, inode);
 		if (ret) {
 			if (ret != -ENOSPC)
 				btrfs_abort_transaction(trans, root, ret);
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index d830853..840a4eb 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3430,7 +3430,9 @@
 }
 
 static int delete_block_group_cache(struct btrfs_fs_info *fs_info,
-				    struct inode *inode, u64 ino)
+				    struct btrfs_block_group_cache *block_group,
+				    struct inode *inode,
+				    u64 ino)
 {
 	struct btrfs_key key;
 	struct btrfs_root *root = fs_info->tree_root;
@@ -3463,7 +3465,7 @@
 		goto out;
 	}
 
-	ret = btrfs_truncate_free_space_cache(root, trans, inode);
+	ret = btrfs_truncate_free_space_cache(root, trans, block_group, inode);
 
 	btrfs_end_transaction(trans, root);
 	btrfs_btree_balance_dirty(root);
@@ -3509,6 +3511,7 @@
 	 */
 	if (ref_root == BTRFS_ROOT_TREE_OBJECTID) {
 		ret = delete_block_group_cache(rc->extent_root->fs_info,
+					       rc->block_group,
 					       NULL, ref_objectid);
 		if (ret != -ENOENT)
 			return ret;
@@ -4223,7 +4226,7 @@
 	btrfs_free_path(path);
 
 	if (!IS_ERR(inode))
-		ret = delete_block_group_cache(fs_info, inode, 0);
+		ret = delete_block_group_cache(fs_info, rc->block_group, inode, 0);
 	else
 		ret = PTR_ERR(inode);
 
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 234d606..5628e25 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -222,6 +222,7 @@
 	atomic_set(&cur_trans->use_count, 2);
 	cur_trans->have_free_bgs = 0;
 	cur_trans->start_time = get_seconds();
+	cur_trans->dirty_bg_run = 0;
 
 	cur_trans->delayed_refs.href_root = RB_ROOT;
 	atomic_set(&cur_trans->delayed_refs.num_entries, 0);
@@ -251,6 +252,8 @@
 	INIT_LIST_HEAD(&cur_trans->switch_commits);
 	INIT_LIST_HEAD(&cur_trans->pending_ordered);
 	INIT_LIST_HEAD(&cur_trans->dirty_bgs);
+	INIT_LIST_HEAD(&cur_trans->io_bgs);
+	mutex_init(&cur_trans->cache_write_mutex);
 	cur_trans->num_dirty_bgs = 0;
 	spin_lock_init(&cur_trans->dirty_bgs_lock);
 	list_add_tail(&cur_trans->list, &fs_info->trans_list);
@@ -1059,6 +1062,7 @@
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;
 	struct list_head *dirty_bgs = &trans->transaction->dirty_bgs;
+	struct list_head *io_bgs = &trans->transaction->io_bgs;
 	struct list_head *next;
 	struct extent_buffer *eb;
 	int ret;
@@ -1112,7 +1116,7 @@
 			return ret;
 	}
 
-	while (!list_empty(dirty_bgs)) {
+	while (!list_empty(dirty_bgs) || !list_empty(io_bgs)) {
 		ret = btrfs_write_dirty_block_groups(trans, root);
 		if (ret)
 			return ret;
@@ -1812,6 +1816,37 @@
 		return ret;
 	}
 
+	if (!cur_trans->dirty_bg_run) {
+		int run_it = 0;
+
+		/* this mutex is also taken before trying to set
+		 * block groups readonly.  We need to make sure
+		 * that nobody has set a block group readonly
+		 * after a extents from that block group have been
+		 * allocated for cache files.  btrfs_set_block_group_ro
+		 * will wait for the transaction to commit if it
+		 * finds dirty_bg_run = 1
+		 *
+		 * The dirty_bg_run flag is also used to make sure only
+		 * one process starts all the block group IO.  It wouldn't
+		 * hurt to have more than one go through, but there's no
+		 * real advantage to it either.
+		 */
+		mutex_lock(&root->fs_info->ro_block_group_mutex);
+		if (!cur_trans->dirty_bg_run) {
+			run_it = 1;
+			cur_trans->dirty_bg_run = 1;
+		}
+		mutex_unlock(&root->fs_info->ro_block_group_mutex);
+
+		if (run_it)
+			ret = btrfs_start_dirty_block_groups(trans, root);
+	}
+	if (ret) {
+		btrfs_end_transaction(trans, root);
+		return ret;
+	}
+
 	spin_lock(&root->fs_info->trans_lock);
 	list_splice(&trans->ordered, &cur_trans->pending_ordered);
 	if (cur_trans->state >= TRANS_STATE_COMMIT_START) {
@@ -2005,6 +2040,7 @@
 
 	assert_qgroups_uptodate(trans);
 	ASSERT(list_empty(&cur_trans->dirty_bgs));
+	ASSERT(list_empty(&cur_trans->io_bgs));
 	update_super_roots(root);
 
 	btrfs_set_super_log_root(root->fs_info->super_copy, 0);
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index 4cb0ae2..0b24755 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -64,10 +64,19 @@
 	struct list_head pending_ordered;
 	struct list_head switch_commits;
 	struct list_head dirty_bgs;
+	struct list_head io_bgs;
 	u64 num_dirty_bgs;
+
+	/*
+	 * we need to make sure block group deletion doesn't race with
+	 * free space cache writeout.  This mutex keeps them from stomping
+	 * on each other
+	 */
+	struct mutex cache_write_mutex;
 	spinlock_t dirty_bgs_lock;
 	struct btrfs_delayed_ref_root delayed_refs;
 	int aborted;
+	int dirty_bg_run;
 };
 
 #define __TRANS_FREEZABLE	(1U << 0)