6 files changed, 226 insertions, 49 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 51ff3f8dbab9..089f6da09411 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1298,8 +1298,8 @@ struct btrfs_block_group_cache {
 	 */
 	struct list_head cluster_list;
 
-	/* For delayed block group creation */
-	struct list_head new_bg_list;
+	/* For delayed block group creation or deletion of empty block groups */
+	struct list_head bg_list;
 };
 
 /* delayed seq elem */
@@ -1568,6 +1568,7 @@ struct btrfs_fs_info {
 	int do_barriers;
 	int closing;
 	int log_root_recovering;
+	int open;
 
 	u64 total_pinned;
 
@@ -1717,6 +1718,9 @@ struct btrfs_fs_info {
 
 	/* Used to reclaim the metadata space in the background. */
 	struct work_struct async_reclaim_work;
+
+	spinlock_t unused_bgs_lock;
+	struct list_head unused_bgs;
 };
 
 struct btrfs_subvolume_writers {
@@ -3344,6 +3348,7 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
 			   u64 size);
 int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root, u64 group_start);
+void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info);
 void btrfs_create_pending_block_groups(struct btrfs_trans_handle *trans,
 				       struct btrfs_root *root);
 u64 btrfs_get_alloc_profile(struct btrfs_root *root, int data);
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 48794f951427..4780e6623c7b 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1769,6 +1769,7 @@ static int cleaner_kthread(void *arg)
 		}
 
 		btrfs_run_delayed_iputs(root);
+		btrfs_delete_unused_bgs(root->fs_info);
 		again = btrfs_clean_one_deleted_snapshot(root);
 		mutex_unlock(&root->fs_info->cleaner_mutex);
 
@@ -2230,6 +2231,7 @@ int open_ctree(struct super_block *sb,
 	spin_lock_init(&fs_info->super_lock);
 	spin_lock_init(&fs_info->qgroup_op_lock);
 	spin_lock_init(&fs_info->buffer_lock);
+	spin_lock_init(&fs_info->unused_bgs_lock);
 	rwlock_init(&fs_info->tree_mod_log_lock);
 	mutex_init(&fs_info->reloc_mutex);
 	mutex_init(&fs_info->delalloc_root_mutex);
@@ -2239,6 +2241,7 @@ int open_ctree(struct super_block *sb,
 	INIT_LIST_HEAD(&fs_info->dirty_cowonly_roots);
 	INIT_LIST_HEAD(&fs_info->space_info);
 	INIT_LIST_HEAD(&fs_info->tree_mod_seq_list);
+	INIT_LIST_HEAD(&fs_info->unused_bgs);
 	btrfs_mapping_init(&fs_info->mapping_tree);
 	btrfs_init_block_rsv(&fs_info->global_block_rsv,
 			     BTRFS_BLOCK_RSV_GLOBAL);
@@ -2977,6 +2980,8 @@ retry_root_backup:
 		fs_info->update_uuid_tree_gen = 1;
 	}
 
+	fs_info->open = 1;
+
 	return 0;
 
 fail_qgroup:
@@ -3688,6 +3693,7 @@ void close_ctree(struct btrfs_root *root)
 	invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
 	btrfs_stop_all_workers(fs_info);
 
+	fs_info->open = 0;
 	free_root_pointers(fs_info, 1);
 
 	iput(fs_info->btree_inode);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index b30ddb49cfab..28a27d5f02d3 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5433,6 +5433,20 @@ static int update_block_group(struct btrfs_root *root,
 			spin_unlock(&cache->space_info->lock);
 		} else {
 			old_val -= num_bytes;
+
+			/*
+			 * No longer have used bytes in this block group, queue
+			 * it for deletion.
+			 */
+			if (old_val == 0) {
+				spin_lock(&info->unused_bgs_lock);
+				if (list_empty(&cache->bg_list)) {
+					btrfs_get_block_group(cache);
+					list_add_tail(&cache->bg_list,
+						      &info->unused_bgs);
+				}
+				spin_unlock(&info->unused_bgs_lock);
+			}
 			btrfs_set_block_group_used(&cache->item, old_val);
 			cache->pinned += num_bytes;
 			cache->space_info->bytes_pinned += num_bytes;
@@ -8855,6 +8869,16 @@ int btrfs_free_block_groups(struct btrfs_fs_info *info)
 	}
 	up_write(&info->commit_root_sem);
 
+	spin_lock(&info->unused_bgs_lock);
+	while (!list_empty(&info->unused_bgs)) {
+		block_group = list_first_entry(&info->unused_bgs,
+					       struct btrfs_block_group_cache,
+					       bg_list);
+		list_del_init(&block_group->bg_list);
+		btrfs_put_block_group(block_group);
+	}
+	spin_unlock(&info->unused_bgs_lock);
+
 	spin_lock(&info->block_group_cache_lock);
 	while ((n = rb_last(&info->block_group_cache_tree)) != NULL) {
 		block_group = rb_entry(n, struct btrfs_block_group_cache,
@@ -8989,7 +9013,7 @@ btrfs_create_block_group_cache(struct btrfs_root *root, u64 start, u64 size)
 	init_rwsem(&cache->data_rwsem);
 	INIT_LIST_HEAD(&cache->list);
 	INIT_LIST_HEAD(&cache->cluster_list);
-	INIT_LIST_HEAD(&cache->new_bg_list);
+	INIT_LIST_HEAD(&cache->bg_list);
 	btrfs_init_free_space_ctl(cache);
 
 	return cache;
@@ -9130,8 +9154,18 @@ int btrfs_read_block_groups(struct btrfs_root *root)
 		__link_block_group(space_info, cache);
 
 		set_avail_alloc_bits(root->fs_info, cache->flags);
-		if (btrfs_chunk_readonly(root, cache->key.objectid))
+		if (btrfs_chunk_readonly(root, cache->key.objectid)) {
 			set_block_group_ro(cache, 1);
+		} else if (btrfs_block_group_used(&cache->item) == 0) {
+			spin_lock(&info->unused_bgs_lock);
+			/* Should always be true but just in case. */
+			if (list_empty(&cache->bg_list)) {
+				btrfs_get_block_group(cache);
+				list_add_tail(&cache->bg_list,
+					      &info->unused_bgs);
+			}
+			spin_unlock(&info->unused_bgs_lock);
+		}
 	}
 
 	list_for_each_entry_rcu(space_info, &root->fs_info->space_info, list) {
@@ -9172,10 +9206,8 @@ void btrfs_create_pending_block_groups(struct btrfs_trans_handle *trans,
 	struct btrfs_key key;
 	int ret = 0;
 
-	list_for_each_entry_safe(block_group, tmp, &trans->new_bgs,
-				 new_bg_list) {
-		list_del_init(&block_group->new_bg_list);
-
+	list_for_each_entry_safe(block_group, tmp, &trans->new_bgs, bg_list) {
+		list_del_init(&block_group->bg_list);
 		if (ret)
 			continue;
 
@@ -9261,7 +9293,7 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
 
 	__link_block_group(cache->space_info, cache);
 
-	list_add_tail(&cache->new_bg_list, &trans->new_bgs);
+	list_add_tail(&cache->bg_list, &trans->new_bgs);
 
 	set_avail_alloc_bits(extent_root->fs_info, type);
 
@@ -9430,6 +9462,101 @@ out:
 	return ret;
 }
 
+/*
+ * Process the unused_bgs list and remove any that don't have any allocated
+ * space inside of them.
+ */
+void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_block_group_cache *block_group;
+	struct btrfs_space_info *space_info;
+	struct btrfs_root *root = fs_info->extent_root;
+	struct btrfs_trans_handle *trans;
+	int ret = 0;
+
+	if (!fs_info->open)
+		return;
+
+	spin_lock(&fs_info->unused_bgs_lock);
+	while (!list_empty(&fs_info->unused_bgs)) {
+		u64 start, end;
+
+		block_group = list_first_entry(&fs_info->unused_bgs,
+					       struct btrfs_block_group_cache,
+					       bg_list);
+		space_info = block_group->space_info;
+		list_del_init(&block_group->bg_list);
+		if (ret || btrfs_mixed_space_info(space_info)) {
+			btrfs_put_block_group(block_group);
+			continue;
+		}
+		spin_unlock(&fs_info->unused_bgs_lock);
+
+		/* Don't want to race with allocators so take the groups_sem */
+		down_write(&space_info->groups_sem);
+		spin_lock(&block_group->lock);
+		if (block_group->reserved ||
+		    btrfs_block_group_used(&block_group->item) ||
+		    block_group->ro) {
+			/*
+			 * We want to bail if we made new allocations or have
+			 * outstanding allocations in this block group.  We do
+			 * the ro check in case balance is currently acting on
+			 * this block group.
+			 */
+			spin_unlock(&block_group->lock);
+			up_write(&space_info->groups_sem);
+			goto next;
+		}
+		spin_unlock(&block_group->lock);
+
+		/* We don't want to force the issue, only flip if it's ok. */
+		ret = set_block_group_ro(block_group, 0);
+		up_write(&space_info->groups_sem);
+		if (ret < 0) {
+			ret = 0;
+			goto next;
+		}
+
+		/*
+		 * Want to do this before we do anything else so we can recover
+		 * properly if we fail to join the transaction.
+		 */
+		trans = btrfs_join_transaction(root);
+		if (IS_ERR(trans)) {
+			btrfs_set_block_group_rw(root, block_group);
+			ret = PTR_ERR(trans);
+			goto next;
+		}
+
+		/*
+		 * We could have pending pinned extents for this block group,
+		 * just delete them, we don't care about them anymore.
+		 */
+		start = block_group->key.objectid;
+		end = start + block_group->key.offset - 1;
+		clear_extent_bits(&fs_info->freed_extents[0], start, end,
+				  EXTENT_DIRTY, GFP_NOFS);
+		clear_extent_bits(&fs_info->freed_extents[1], start, end,
+				  EXTENT_DIRTY, GFP_NOFS);
+
+		/* Reset pinned so btrfs_put_block_group doesn't complain */
+		block_group->pinned = 0;
+
+		/*
+		 * Btrfs_remove_chunk will abort the transaction if things go
+		 * horribly wrong.
+		 */
+		ret = btrfs_remove_chunk(trans, root,
+					 block_group->key.objectid);
+		btrfs_end_transaction(trans, root);
+next:
+		btrfs_put_block_group(block_group);
+		spin_lock(&fs_info->unused_bgs_lock);
+	}
+	spin_unlock(&fs_info->unused_bgs_lock);
+}
+
 int btrfs_init_space_info(struct btrfs_fs_info *fs_info)
 {
 	struct btrfs_space_info *space_info;
diff --git a/fs/btrfs/tests/free-space-tests.c b/fs/btrfs/tests/free-space-tests.c
index d78ae10d0446..2299bfde39ee 100644
--- a/fs/btrfs/tests/free-space-tests.c
+++ b/fs/btrfs/tests/free-space-tests.c
@@ -45,7 +45,7 @@ static struct btrfs_block_group_cache *init_test_block_group(void)
 	spin_lock_init(&cache->lock);
 	INIT_LIST_HEAD(&cache->list);
 	INIT_LIST_HEAD(&cache->cluster_list);
-	INIT_LIST_HEAD(&cache->new_bg_list);
+	INIT_LIST_HEAD(&cache->bg_list);
 
 	btrfs_init_free_space_ctl(cache);
 
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 63e632746d8a..f27c0f7c387e 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2568,58 +2568,49 @@ static int btrfs_del_sys_chunk(struct btrfs_root *root, u64 chunk_objectid, u64
 	return ret;
 }
 
-static int btrfs_relocate_chunk(struct btrfs_root *root,
-			 u64 chunk_tree, u64 chunk_objectid,
-			 u64 chunk_offset)
+int btrfs_remove_chunk(struct btrfs_trans_handle *trans,
+		       struct btrfs_root *root, u64 chunk_offset)
 {
 	struct extent_map_tree *em_tree;
-	struct btrfs_root *extent_root;
-	struct btrfs_trans_handle *trans;
-	struct btrfs_device *device;
 	struct extent_map *em;
+	struct btrfs_root *extent_root = root->fs_info->extent_root;
 	struct map_lookup *map;
 	u64 dev_extent_len = 0;
-	int ret;
-	int i;
+	u64 chunk_objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
+	u64 chunk_tree = root->fs_info->chunk_root->objectid;
+	int i, ret = 0;
 
+	/* Just in case */
 	root = root->fs_info->chunk_root;
-	extent_root = root->fs_info->extent_root;
 	em_tree = &root->fs_info->mapping_tree.map_tree;
 
-	ret = btrfs_can_relocate(extent_root, chunk_offset);
-	if (ret)
-		return -ENOSPC;
-
-	/* step one, relocate all the extents inside this chunk */
-	ret = btrfs_relocate_block_group(extent_root, chunk_offset);
-	if (ret)
-		return ret;
-
-	trans = btrfs_start_transaction(root, 0);
-	if (IS_ERR(trans)) {
-		ret = PTR_ERR(trans);
-		btrfs_std_error(root->fs_info, ret);
-		return ret;
-	}
-
-	/*
-	 * step two, delete the device extents and the
-	 * chunk tree entries
-	 */
 	read_lock(&em_tree->lock);
 	em = lookup_extent_mapping(em_tree, chunk_offset, 1);
 	read_unlock(&em_tree->lock);
 
-	BUG_ON(!em || em->start > chunk_offset ||
-	       em->start + em->len < chunk_offset);
+	if (!em || em->start > chunk_offset ||
+	    em->start + em->len < chunk_offset) {
+		/*
+		 * This is a logic error, but we don't want to just rely on the
+		 * user having built with ASSERT enabled, so if ASSERT doens't
+		 * do anything we still error out.
+		 */
+		ASSERT(0);
+		if (em)
+			free_extent_map(em);
+		return -EINVAL;
+	}
 	map = (struct map_lookup *)em->bdev;
 
 	for (i = 0; i < map->num_stripes; i++) {
-		device = map->stripes[i].dev;
+		struct btrfs_device *device = map->stripes[i].dev;
 		ret = btrfs_free_dev_extent(trans, device,
 					    map->stripes[i].physical,
 					    &dev_extent_len);
-		BUG_ON(ret);
+		if (ret) {
+			btrfs_abort_transaction(trans, root, ret);
+			goto out;
+		}
 
 		if (device->bytes_used > 0) {
 			lock_chunks(root);
@@ -2634,23 +2625,34 @@ static int btrfs_relocate_chunk(struct btrfs_root *root,
 
 		if (map->stripes[i].dev) {
 			ret = btrfs_update_device(trans, map->stripes[i].dev);
-			BUG_ON(ret);
+			if (ret) {
+				btrfs_abort_transaction(trans, root, ret);
+				goto out;
+			}
 		}
 	}
 	ret = btrfs_free_chunk(trans, root, chunk_tree, chunk_objectid,
 			       chunk_offset);
-
-	BUG_ON(ret);
+	if (ret) {
+		btrfs_abort_transaction(trans, root, ret);
+		goto out;
+	}
 
 	trace_btrfs_chunk_free(root, map, chunk_offset, em->len);
 
 	if (map->type & BTRFS_BLOCK_GROUP_SYSTEM) {
 		ret = btrfs_del_sys_chunk(root, chunk_objectid, chunk_offset);
-		BUG_ON(ret);
+		if (ret) {
+			btrfs_abort_transaction(trans, root, ret);
+			goto out;
+		}
 	}
 
 	ret = btrfs_remove_block_group(trans, extent_root, chunk_offset);
-	BUG_ON(ret);
+	if (ret) {
+		btrfs_abort_transaction(trans, extent_root, ret);
+		goto out;
+	}
 
 	write_lock(&em_tree->lock);
 	remove_extent_mapping(em_tree, em);
@@ -2658,11 +2660,46 @@ static int btrfs_relocate_chunk(struct btrfs_root *root,
 
 	/* once for the tree */
 	free_extent_map(em);
+out:
 	/* once for us */
 	free_extent_map(em);
+	return ret;
+}
+
+static int btrfs_relocate_chunk(struct btrfs_root *root,
+			 u64 chunk_tree, u64 chunk_objectid,
+			 u64 chunk_offset)
+{
+	struct btrfs_root *extent_root;
+	struct btrfs_trans_handle *trans;
+	int ret;
+
+	root = root->fs_info->chunk_root;
+	extent_root = root->fs_info->extent_root;
+
+	ret = btrfs_can_relocate(extent_root, chunk_offset);
+	if (ret)
+		return -ENOSPC;
+
+	/* step one, relocate all the extents inside this chunk */
+	ret = btrfs_relocate_block_group(extent_root, chunk_offset);
+	if (ret)
+		return ret;
 
+	trans = btrfs_start_transaction(root, 0);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		btrfs_std_error(root->fs_info, ret);
+		return ret;
+	}
+
+	/*
+	 * step two, delete the device extents and the
+	 * chunk tree entries
+	 */
+	ret = btrfs_remove_chunk(trans, root, chunk_offset);
 	btrfs_end_transaction(trans, root);
-	return 0;
+	return ret;
 }
 
 static int btrfs_relocate_sys_chunks(struct btrfs_root *root)
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 91998bc0b4c4..08980fa23039 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -463,6 +463,8 @@ unsigned long btrfs_full_stripe_len(struct btrfs_root *root,
 int btrfs_finish_chunk_alloc(struct btrfs_trans_handle *trans,
 				struct btrfs_root *extent_root,
 				u64 chunk_offset, u64 chunk_size);
+int btrfs_remove_chunk(struct btrfs_trans_handle *trans,
+		       struct btrfs_root *root, u64 chunk_offset);
 
 static inline int btrfs_dev_stats_dirty(struct btrfs_device *dev)
 {