Merge branch 'allocator-fixes' into for-linus-4.4

Signed-off-by: NChris Mason <clm@fb.com>

fs/btrfs/backref.c

@@ -362,6 +362,12 @@ static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
 		goto out;
 	}
 
+	if (btrfs_test_is_dummy_root(root)) {
+		srcu_read_unlock(&fs_info->subvol_srcu, index);
+		ret = -ENOENT;
+		goto out;
+	}
+
 	if (path->search_commit_root)
 		root_level = btrfs_header_level(root->commit_root);
 	else if (time_seq == (u64)-1)

fs/btrfs/ctree.h

@@ -1154,6 +1154,10 @@ struct btrfs_space_info {
 				   delalloc/allocations */
 	u64 bytes_readonly;	/* total bytes that are read only */
 
+	u64 max_extent_size;	/* This will hold the maximum extent size of
+				   the space info if we had an ENOSPC in the
+				   allocator. */
+
 	unsigned int full:1;	/* indicates that we cannot allocate any more
 				   chunks for this space */
 	unsigned int chunk_alloc:1;	/* set if we are allocating a chunk */
@@ -1228,6 +1232,9 @@ struct btrfs_free_cluster {
 	/* first extent starting offset */
 	u64 window_start;
 
+	/* We did a full search and couldn't create a cluster */
+	bool fragmented;
+
 	struct btrfs_block_group_cache *block_group;
 	/*
 	 * when a cluster is allocated from a block group, we put the
@@ -2148,6 +2155,8 @@ struct btrfs_ioctl_defrag_range_args {
 #define BTRFS_MOUNT_CHECK_INTEGRITY_INCLUDING_EXTENT_DATA (1 << 21)
 #define BTRFS_MOUNT_PANIC_ON_FATAL_ERROR	(1 << 22)
 #define BTRFS_MOUNT_RESCAN_UUID_TREE	(1 << 23)
+#define BTRFS_MOUNT_FRAGMENT_DATA	(1 << 24)
+#define BTRFS_MOUNT_FRAGMENT_METADATA	(1 << 25)
 
 #define BTRFS_DEFAULT_COMMIT_INTERVAL	(30)
 #define BTRFS_DEFAULT_MAX_INLINE	(8192)
@@ -2172,6 +2181,18 @@ struct btrfs_ioctl_defrag_range_args {
 	btrfs_clear_opt(root->fs_info->mount_opt, opt);			\
 }
 
+#ifdef CONFIG_BTRFS_DEBUG
+static inline int
+btrfs_should_fragment_free_space(struct btrfs_root *root,
+				 struct btrfs_block_group_cache *block_group)
+{
+	return (btrfs_test_opt(root, FRAGMENT_METADATA) &&
+		block_group->flags & BTRFS_BLOCK_GROUP_METADATA) ||
+	       (btrfs_test_opt(root, FRAGMENT_DATA) &&
+		block_group->flags &  BTRFS_BLOCK_GROUP_DATA);
+}
+#endif
+
 /*
  * Requests for changes that need to be done during transaction commit.
  *

fs/btrfs/disk-io.c

@@ -4327,25 +4327,6 @@ static int btrfs_destroy_pinned_extent(struct btrfs_root *root,
 	return 0;
 }
 
-static void btrfs_free_pending_ordered(struct btrfs_transaction *cur_trans,
-				       struct btrfs_fs_info *fs_info)
-{
-	struct btrfs_ordered_extent *ordered;
-
-	spin_lock(&fs_info->trans_lock);
-	while (!list_empty(&cur_trans->pending_ordered)) {
-		ordered = list_first_entry(&cur_trans->pending_ordered,
-					   struct btrfs_ordered_extent,
-					   trans_list);
-		list_del_init(&ordered->trans_list);
-		spin_unlock(&fs_info->trans_lock);
-
-		btrfs_put_ordered_extent(ordered);
-		spin_lock(&fs_info->trans_lock);
-	}
-	spin_unlock(&fs_info->trans_lock);
-}
-
 void btrfs_cleanup_one_transaction(struct btrfs_transaction *cur_trans,
 				   struct btrfs_root *root)
 {
@@ -4357,7 +4338,6 @@ void btrfs_cleanup_one_transaction(struct btrfs_transaction *cur_trans,
 	cur_trans->state = TRANS_STATE_UNBLOCKED;
 	wake_up(&root->fs_info->transaction_wait);
 
-	btrfs_free_pending_ordered(cur_trans, root->fs_info);
 	btrfs_destroy_delayed_inodes(root);
 	btrfs_assert_delayed_root_empty(root);
 

fs/btrfs/extent-tree.c

@@ -332,6 +332,27 @@ static void put_caching_control(struct btrfs_caching_control *ctl)
 		kfree(ctl);
 }
 
+#ifdef CONFIG_BTRFS_DEBUG
+static void fragment_free_space(struct btrfs_root *root,
+				struct btrfs_block_group_cache *block_group)
+{
+	u64 start = block_group->key.objectid;
+	u64 len = block_group->key.offset;
+	u64 chunk = block_group->flags & BTRFS_BLOCK_GROUP_METADATA ?
+		root->nodesize : root->sectorsize;
+	u64 step = chunk << 1;
+
+	while (len > chunk) {
+		btrfs_remove_free_space(block_group, start, chunk);
+		start += step;
+		if (len < step)
+			len = 0;
+		else
+			len -= step;
+	}
+}
+#endif
+
 /*
  * this is only called by cache_block_group, since we could have freed extents
  * we need to check the pinned_extents for any extents that can't be used yet
@@ -388,6 +409,7 @@ static noinline void caching_thread(struct btrfs_work *work)
 	u64 last = 0;
 	u32 nritems;
 	int ret = -ENOMEM;
+	bool wakeup = true;
 
 	caching_ctl = container_of(work, struct btrfs_caching_control, work);
 	block_group = caching_ctl->block_group;
@@ -400,6 +422,15 @@ static noinline void caching_thread(struct btrfs_work *work)
 
 	last = max_t(u64, block_group->key.objectid, BTRFS_SUPER_INFO_OFFSET);
 
+#ifdef CONFIG_BTRFS_DEBUG
+	/*
+	 * If we're fragmenting we don't want to make anybody think we can
+	 * allocate from this block group until we've had a chance to fragment
+	 * the free space.
+	 */
+	if (btrfs_should_fragment_free_space(extent_root, block_group))
+		wakeup = false;
+#endif
 	/*
 	 * We don't want to deadlock with somebody trying to allocate a new
 	 * extent for the extent root while also trying to search the extent
@@ -441,7 +472,8 @@ static noinline void caching_thread(struct btrfs_work *work)
 
 			if (need_resched() ||
 			    rwsem_is_contended(&fs_info->commit_root_sem)) {
-				caching_ctl->progress = last;
+				if (wakeup)
+					caching_ctl->progress = last;
 				btrfs_release_path(path);
 				up_read(&fs_info->commit_root_sem);
 				mutex_unlock(&caching_ctl->mutex);
@@ -464,7 +496,8 @@ static noinline void caching_thread(struct btrfs_work *work)
 			key.offset = 0;
 			key.type = BTRFS_EXTENT_ITEM_KEY;
 
-			caching_ctl->progress = last;
+			if (wakeup)
+				caching_ctl->progress = last;
 			btrfs_release_path(path);
 			goto next;
 		}
@@ -491,7 +524,8 @@ static noinline void caching_thread(struct btrfs_work *work)
 
 			if (total_found > (1024 * 1024 * 2)) {
 				total_found = 0;
-				wake_up(&caching_ctl->wait);
+				if (wakeup)
+					wake_up(&caching_ctl->wait);
 			}
 		}
 		path->slots[0]++;
@@ -501,13 +535,27 @@ static noinline void caching_thread(struct btrfs_work *work)
 	total_found += add_new_free_space(block_group, fs_info, last,
 					  block_group->key.objectid +
 					  block_group->key.offset);
-	caching_ctl->progress = (u64)-1;
-
 	spin_lock(&block_group->lock);
 	block_group->caching_ctl = NULL;
 	block_group->cached = BTRFS_CACHE_FINISHED;
 	spin_unlock(&block_group->lock);
 
+#ifdef CONFIG_BTRFS_DEBUG
+	if (btrfs_should_fragment_free_space(extent_root, block_group)) {
+		u64 bytes_used;
+
+		spin_lock(&block_group->space_info->lock);
+		spin_lock(&block_group->lock);
+		bytes_used = block_group->key.offset -
+			btrfs_block_group_used(&block_group->item);
+		block_group->space_info->bytes_used += bytes_used >> 1;
+		spin_unlock(&block_group->lock);
+		spin_unlock(&block_group->space_info->lock);
+		fragment_free_space(extent_root, block_group);
+	}
+#endif
+
+	caching_ctl->progress = (u64)-1;
 err:
 	btrfs_free_path(path);
 	up_read(&fs_info->commit_root_sem);
@@ -607,6 +655,22 @@ static int cache_block_group(struct btrfs_block_group_cache *cache,
 			}
 		}
 		spin_unlock(&cache->lock);
+#ifdef CONFIG_BTRFS_DEBUG
+		if (ret == 1 &&
+		    btrfs_should_fragment_free_space(fs_info->extent_root,
+						     cache)) {
+			u64 bytes_used;
+
+			spin_lock(&cache->space_info->lock);
+			spin_lock(&cache->lock);
+			bytes_used = cache->key.offset -
+				btrfs_block_group_used(&cache->item);
+			cache->space_info->bytes_used += bytes_used >> 1;
+			spin_unlock(&cache->lock);
+			spin_unlock(&cache->space_info->lock);
+			fragment_free_space(fs_info->extent_root, cache);
+		}
+#endif
 		mutex_unlock(&caching_ctl->mutex);
 
 		wake_up(&caching_ctl->wait);
@@ -3343,6 +3407,15 @@ static int cache_save_setup(struct btrfs_block_group_cache *block_group,
 	}
 	spin_unlock(&block_group->lock);
 
+	/*
+	 * We hit an ENOSPC when setting up the cache in this transaction, just
+	 * skip doing the setup, we've already cleared the cache so we're safe.
+	 */
+	if (test_bit(BTRFS_TRANS_CACHE_ENOSPC, &trans->transaction->flags)) {
+		ret = -ENOSPC;
+		goto out_put;
+	}
+
 	/*
 	 * Try to preallocate enough space based on how big the block group is.
 	 * Keep in mind this has to include any pinned space which could end up
@@ -3363,8 +3436,18 @@ static int cache_save_setup(struct btrfs_block_group_cache *block_group,
 	ret = btrfs_prealloc_file_range_trans(inode, trans, 0, 0, num_pages,
 					      num_pages, num_pages,
 					      &alloc_hint);
+	/*
+	 * Our cache requires contiguous chunks so that we don't modify a bunch
+	 * of metadata or split extents when writing the cache out, which means
+	 * we can enospc if we are heavily fragmented in addition to just normal
+	 * out of space conditions.  So if we hit this just skip setting up any
+	 * other block groups for this transaction, maybe we'll unpin enough
+	 * space the next time around.
+	 */
 	if (!ret)
 		dcs = BTRFS_DC_SETUP;
+	else if (ret == -ENOSPC)
+		set_bit(BTRFS_TRANS_CACHE_ENOSPC, &trans->transaction->flags);
 	btrfs_free_reserved_data_space(inode, 0, num_pages);
 
 out_put:
@@ -3751,6 +3834,7 @@ static int update_space_info(struct btrfs_fs_info *info, u64 flags,
 	found->bytes_readonly = 0;
 	found->bytes_may_use = 0;
 	found->full = 0;
+	found->max_extent_size = 0;
 	found->force_alloc = CHUNK_ALLOC_NO_FORCE;
 	found->chunk_alloc = 0;
 	found->flush = 0;
@@ -4003,7 +4087,8 @@ int btrfs_alloc_data_chunk_ondemand(struct inode *inode, u64 bytes)
 			if (IS_ERR(trans))
 				return PTR_ERR(trans);
 			if (have_pinned_space >= 0 ||
-			    trans->transaction->have_free_bgs ||
+			    test_bit(BTRFS_TRANS_HAVE_FREE_BGS,
+				     &trans->transaction->flags) ||
 			    need_commit > 0) {
 				ret = btrfs_commit_transaction(trans, root);
 				if (ret)
@@ -6112,6 +6197,34 @@ void btrfs_prepare_extent_commit(struct btrfs_trans_handle *trans,
 	update_global_block_rsv(fs_info);
 }
 
+/*
+ * Returns the free cluster for the given space info and sets empty_cluster to
+ * what it should be based on the mount options.
+ */
+static struct btrfs_free_cluster *
+fetch_cluster_info(struct btrfs_root *root, struct btrfs_space_info *space_info,
+		   u64 *empty_cluster)
+{
+	struct btrfs_free_cluster *ret = NULL;
+	bool ssd = btrfs_test_opt(root, SSD);
+
+	*empty_cluster = 0;
+	if (btrfs_mixed_space_info(space_info))
+		return ret;
+
+	if (ssd)
+		*empty_cluster = 2 * 1024 * 1024;
+	if (space_info->flags & BTRFS_BLOCK_GROUP_METADATA) {
+		ret = &root->fs_info->meta_alloc_cluster;
+		if (!ssd)
+			*empty_cluster = 64 * 1024;
+	} else if ((space_info->flags & BTRFS_BLOCK_GROUP_DATA) && ssd) {
+		ret = &root->fs_info->data_alloc_cluster;
+	}
+
+	return ret;
+}
+
 static int unpin_extent_range(struct btrfs_root *root, u64 start, u64 end,
 			      const bool return_free_space)
 {
@@ -6119,7 +6232,10 @@ static int unpin_extent_range(struct btrfs_root *root, u64 start, u64 end,
 	struct btrfs_block_group_cache *cache = NULL;
 	struct btrfs_space_info *space_info;
 	struct btrfs_block_rsv *global_rsv = &fs_info->global_block_rsv;
+	struct btrfs_free_cluster *cluster = NULL;
 	u64 len;
+	u64 total_unpinned = 0;
+	u64 empty_cluster = 0;
 	bool readonly;
 
 	while (start <= end) {
@@ -6128,8 +6244,14 @@ static int unpin_extent_range(struct btrfs_root *root, u64 start, u64 end,
 		    start >= cache->key.objectid + cache->key.offset) {
 			if (cache)
 				btrfs_put_block_group(cache);
+			total_unpinned = 0;
 			cache = btrfs_lookup_block_group(fs_info, start);
 			BUG_ON(!cache); /* Logic error */
+
+			cluster = fetch_cluster_info(root,
+						     cache->space_info,
+						     &empty_cluster);
+			empty_cluster <<= 1;
 		}
 
 		len = cache->key.objectid + cache->key.offset - start;
@@ -6142,12 +6264,27 @@ static int unpin_extent_range(struct btrfs_root *root, u64 start, u64 end,
 		}
 
 		start += len;
+		total_unpinned += len;
 		space_info = cache->space_info;
 
+		/*
+		 * If this space cluster has been marked as fragmented and we've
+		 * unpinned enough in this block group to potentially allow a
+		 * cluster to be created inside of it go ahead and clear the
+		 * fragmented check.
+		 */
+		if (cluster && cluster->fragmented &&
+		    total_unpinned > empty_cluster) {
+			spin_lock(&cluster->lock);
+			cluster->fragmented = 0;
+			spin_unlock(&cluster->lock);
+		}
+
 		spin_lock(&space_info->lock);
 		spin_lock(&cache->lock);
 		cache->pinned -= len;
 		space_info->bytes_pinned -= len;
+		space_info->max_extent_size = 0;
 		percpu_counter_add(&space_info->total_bytes_pinned, -len);
 		if (cache->ro) {
 			space_info->bytes_readonly += len;
@@ -6880,7 +7017,7 @@ static noinline int find_free_extent(struct btrfs_root *orig_root,
 	struct btrfs_block_group_cache *block_group = NULL;
 	u64 search_start = 0;
 	u64 max_extent_size = 0;
-	int empty_cluster = 2 * 1024 * 1024;
+	u64 empty_cluster = 0;
 	struct btrfs_space_info *space_info;
 	int loop = 0;
 	int index = __get_raid_index(flags);
@@ -6890,6 +7027,7 @@ static noinline int find_free_extent(struct btrfs_root *orig_root,
 	bool failed_alloc = false;
 	bool use_cluster = true;
 	bool have_caching_bg = false;
+	bool full_search = false;
 
 	WARN_ON(num_bytes < root->sectorsize);
 	ins->type = BTRFS_EXTENT_ITEM_KEY;
@@ -6905,36 +7043,47 @@ static noinline int find_free_extent(struct btrfs_root *orig_root,
 	}
 
 	/*
-	 * If the space info is for both data and metadata it means we have a
-	 * small filesystem and we can't use the clustering stuff.
+	 * If our free space is heavily fragmented we may not be able to make
+	 * big contiguous allocations, so instead of doing the expensive search
+	 * for free space, simply return ENOSPC with our max_extent_size so we
+	 * can go ahead and search for a more manageable chunk.
+	 *
+	 * If our max_extent_size is large enough for our allocation simply
+	 * disable clustering since we will likely not be able to find enough
+	 * space to create a cluster and induce latency trying.
 	 */
-	if (btrfs_mixed_space_info(space_info))
-		use_cluster = false;
-
-	if (flags & BTRFS_BLOCK_GROUP_METADATA && use_cluster) {
-		last_ptr = &root->fs_info->meta_alloc_cluster;
-		if (!btrfs_test_opt(root, SSD))
-			empty_cluster = 64 * 1024;
-	}
-
-	if ((flags & BTRFS_BLOCK_GROUP_DATA) && use_cluster &&
-	    btrfs_test_opt(root, SSD)) {
-		last_ptr = &root->fs_info->data_alloc_cluster;
+	if (unlikely(space_info->max_extent_size)) {
+		spin_lock(&space_info->lock);
+		if (space_info->max_extent_size &&
+		    num_bytes > space_info->max_extent_size) {
+			ins->offset = space_info->max_extent_size;
+			spin_unlock(&space_info->lock);
+			return -ENOSPC;
+		} else if (space_info->max_extent_size) {
+			use_cluster = false;
+		}
+		spin_unlock(&space_info->lock);
 	}
 
+	last_ptr = fetch_cluster_info(orig_root, space_info, &empty_cluster);
 	if (last_ptr) {
 		spin_lock(&last_ptr->lock);
 		if (last_ptr->block_group)
 			hint_byte = last_ptr->window_start;
+		if (last_ptr->fragmented) {
+			/*
+			 * We still set window_start so we can keep track of the
+			 * last place we found an allocation to try and save
+			 * some time.
+			 */
+			hint_byte = last_ptr->window_start;
+			use_cluster = false;
+		}
 		spin_unlock(&last_ptr->lock);
 	}
 
 	search_start = max(search_start, first_logical_byte(root, 0));
 	search_start = max(search_start, hint_byte);
-
-	if (!last_ptr)
-		empty_cluster = 0;
-
 	if (search_start == hint_byte) {
 		block_group = btrfs_lookup_block_group(root->fs_info,
 						       search_start);
@@ -6969,6 +7118,8 @@ static noinline int find_free_extent(struct btrfs_root *orig_root,
 	}
 search:
 	have_caching_bg = false;
+	if (index == 0 || index == __get_raid_index(flags))
+		full_search = true;
 	down_read(&space_info->groups_sem);
 	list_for_each_entry(block_group, &space_info->block_groups[index],
 			    list) {
@@ -7002,6 +7153,7 @@ static noinline int find_free_extent(struct btrfs_root *orig_root,
 have_block_group:
 		cached = block_group_cache_done(block_group);
 		if (unlikely(!cached)) {
+			have_caching_bg = true;
 			ret = cache_block_group(block_group, 0);
 			BUG_ON(ret < 0);
 			ret = 0;
@@ -7016,7 +7168,7 @@ static noinline int find_free_extent(struct btrfs_root *orig_root,
 		 * Ok we want to try and use the cluster allocator, so
 		 * lets look there
 		 */
-		if (last_ptr) {
+		if (last_ptr && use_cluster) {
 			struct btrfs_block_group_cache *used_block_group;
 			unsigned long aligned_cluster;
 			/*
@@ -7142,6 +7294,16 @@ static noinline int find_free_extent(struct btrfs_root *orig_root,
 		}
 
 unclustered_alloc:
+		/*
+		 * We are doing an unclustered alloc, set the fragmented flag so
+		 * we don't bother trying to setup a cluster again until we get
+		 * more space.
+		 */
+		if (unlikely(last_ptr)) {
+			spin_lock(&last_ptr->lock);
+			last_ptr->fragmented = 1;
+			spin_unlock(&last_ptr->lock);
+		}
 		spin_lock(&block_group->free_space_ctl->tree_lock);
 		if (cached &&
 		    block_group->free_space_ctl->free_space <
@@ -7174,8 +7336,6 @@ static noinline int find_free_extent(struct btrfs_root *orig_root,
 			failed_alloc = true;
 			goto have_block_group;
 		} else if (!offset) {
-			if (!cached)
-				have_caching_bg = true;
 			goto loop;
 		}
 checks:
@@ -7232,7 +7392,20 @@ static noinline int find_free_extent(struct btrfs_root *orig_root,
 	 */
 	if (!ins->objectid && loop < LOOP_NO_EMPTY_SIZE) {
 		index = 0;
-		loop++;
+		if (loop == LOOP_CACHING_NOWAIT) {
+			/*
+			 * We want to skip the LOOP_CACHING_WAIT step if we
+			 * don't have any unached bgs and we've alrelady done a
+			 * full search through.
+			 */
+			if (have_caching_bg || !full_search)
+				loop = LOOP_CACHING_WAIT;
+			else
+				loop = LOOP_ALLOC_CHUNK;
+		} else {
+			loop++;
+		}
+
 		if (loop == LOOP_ALLOC_CHUNK) {
 			struct btrfs_trans_handle *trans;
 			int exist = 0;
@@ -7250,6 +7423,15 @@ static noinline int find_free_extent(struct btrfs_root *orig_root,
 
 			ret = do_chunk_alloc(trans, root, flags,
 					     CHUNK_ALLOC_FORCE);
+
+			/*
+			 * If we can't allocate a new chunk we've already looped
+			 * through at least once, move on to the NO_EMPTY_SIZE
+			 * case.
+			 */
+			if (ret == -ENOSPC)
+				loop = LOOP_NO_EMPTY_SIZE;
+
 			/*
 			 * Do not bail out on ENOSPC since we
 			 * can do more things.
@@ -7266,6 +7448,15 @@ static noinline int find_free_extent(struct btrfs_root *orig_root,
 		}
 
 		if (loop == LOOP_NO_EMPTY_SIZE) {
+			/*
+			 * Don't loop again if we already have no empty_size and
+			 * no empty_cluster.
+			 */
+			if (empty_size == 0 &&
+			    empty_cluster == 0) {
+				ret = -ENOSPC;
+				goto out;
+			}
 			empty_size = 0;
 			empty_cluster = 0;
 		}
@@ -7274,11 +7465,20 @@ static noinline int find_free_extent(struct btrfs_root *orig_root,
 	} else if (!ins->objectid) {
 		ret = -ENOSPC;
 	} else if (ins->objectid) {
+		if (!use_cluster && last_ptr) {
+			spin_lock(&last_ptr->lock);
+			last_ptr->window_start = ins->objectid;
+			spin_unlock(&last_ptr->lock);
+		}
 		ret = 0;
 	}
 out:
-	if (ret == -ENOSPC)
+	if (ret == -ENOSPC) {
+		spin_lock(&space_info->lock);
+		space_info->max_extent_size = max_extent_size;
+		spin_unlock(&space_info->lock);
 		ins->offset = max_extent_size;
+	}
 	return ret;
 }
 
@@ -7327,7 +7527,7 @@ int btrfs_reserve_extent(struct btrfs_root *root,
 			 u64 empty_size, u64 hint_byte,
 			 struct btrfs_key *ins, int is_data, int delalloc)
 {
-	bool final_tried = false;
+	bool final_tried = num_bytes == min_alloc_size;
 	u64 flags;
 	int ret;
 
@@ -8929,7 +9129,7 @@ int btrfs_inc_block_group_ro(struct btrfs_root *root,
 	 * back off and let this transaction commit
 	 */
 	mutex_lock(&root->fs_info->ro_block_group_mutex);
-	if (trans->transaction->dirty_bg_run) {
+	if (test_bit(BTRFS_TRANS_DIRTY_BG_RUN, &trans->transaction->flags)) {
 		u64 transid = trans->transid;
 
 		mutex_unlock(&root->fs_info->ro_block_group_mutex);
@@ -9679,6 +9879,14 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
 
 	free_excluded_extents(root, cache);
 
+#ifdef CONFIG_BTRFS_DEBUG
+	if (btrfs_should_fragment_free_space(root, cache)) {
+		u64 new_bytes_used = size - bytes_used;
+
+		bytes_used += new_bytes_used >> 1;
+		fragment_free_space(root, cache);
+	}
+#endif
 	/*
 	 * Call to ensure the corresponding space_info object is created and
 	 * assigned to our block group, but don't update its counters just yet.

fs/btrfs/free-space-cache.c

@@ -1730,7 +1730,7 @@ static void bitmap_set_bits(struct btrfs_free_space_ctl *ctl,
  */
 static int search_bitmap(struct btrfs_free_space_ctl *ctl,
 			 struct btrfs_free_space *bitmap_info, u64 *offset,
-			 u64 *bytes)
+			 u64 *bytes, bool for_alloc)
 {
 	unsigned long found_bits = 0;
 	unsigned long max_bits = 0;
@@ -1738,11 +1738,26 @@ static int search_bitmap(struct btrfs_free_space_ctl *ctl,
 	unsigned long next_zero;
 	unsigned long extent_bits;
 
+	/*
+	 * Skip searching the bitmap if we don't have a contiguous section that
+	 * is large enough for this allocation.
+	 */
+	if (for_alloc &&
+	    bitmap_info->max_extent_size &&
+	    bitmap_info->max_extent_size < *bytes) {
+		*bytes = bitmap_info->max_extent_size;
+		return -1;
+	}
+
 	i = offset_to_bit(bitmap_info->offset, ctl->unit,
 			  max_t(u64, *offset, bitmap_info->offset));
 	bits = bytes_to_bits(*bytes, ctl->unit);
 
 	for_each_set_bit_from(i, bitmap_info->bitmap, BITS_PER_BITMAP) {
+		if (for_alloc && bits == 1) {
+			found_bits = 1;
+			break;
+		}
 		next_zero = find_next_zero_bit(bitmap_info->bitmap,
 					       BITS_PER_BITMAP, i);
 		extent_bits = next_zero - i;
@@ -1762,6 +1777,7 @@ static int search_bitmap(struct btrfs_free_space_ctl *ctl,
 	}
 
 	*bytes = (u64)(max_bits) * ctl->unit;
+	bitmap_info->max_extent_size = *bytes;
 	return -1;
 }
 
@@ -1813,7 +1829,7 @@ find_free_space(struct btrfs_free_space_ctl *ctl, u64 *offset, u64 *bytes,
 		if (entry->bitmap) {
 			u64 size = *bytes;
 
-			ret = search_bitmap(ctl, entry, &tmp, &size);
+			ret = search_bitmap(ctl, entry, &tmp, &size, true);
 			if (!ret) {
 				*offset = tmp;
 				*bytes = size;
@@ -1874,7 +1890,8 @@ static noinline int remove_from_bitmap(struct btrfs_free_space_ctl *ctl,
 	search_start = *offset;
 	search_bytes = ctl->unit;
 	search_bytes = min(search_bytes, end - search_start + 1);
-	ret = search_bitmap(ctl, bitmap_info, &search_start, &search_bytes);
+	ret = search_bitmap(ctl, bitmap_info, &search_start, &search_bytes,
+			    false);
 	if (ret < 0 || search_start != *offset)
 		return -EINVAL;
 
@@ -1919,7 +1936,7 @@ static noinline int remove_from_bitmap(struct btrfs_free_space_ctl *ctl,
 		search_start = *offset;
 		search_bytes = ctl->unit;
 		ret = search_bitmap(ctl, bitmap_info, &search_start,
-				    &search_bytes);
+				    &search_bytes, false);
 		if (ret < 0 || search_start != *offset)
 			return -EAGAIN;
 
@@ -1943,6 +1960,12 @@ static u64 add_bytes_to_bitmap(struct btrfs_free_space_ctl *ctl,
 
 	bitmap_set_bits(ctl, info, offset, bytes_to_set);
 
+	/*
+	 * We set some bytes, we have no idea what the max extent size is
+	 * anymore.
+	 */
+	info->max_extent_size = 0;
+
 	return bytes_to_set;
 
 }
@@ -1951,12 +1974,19 @@ static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
 		      struct btrfs_free_space *info)
 {
 	struct btrfs_block_group_cache *block_group = ctl->private;
+	bool forced = false;
+
+#ifdef CONFIG_BTRFS_DEBUG
+	if (btrfs_should_fragment_free_space(block_group->fs_info->extent_root,
+					     block_group))
+		forced = true;
+#endif
 
 	/*
 	 * If we are below the extents threshold then we can add this as an
 	 * extent, and don't have to deal with the bitmap
 	 */
-	if (ctl->free_extents < ctl->extents_thresh) {
+	if (!forced && ctl->free_extents < ctl->extents_thresh) {
 		/*
 		 * If this block group has some small extents we don't want to
 		 * use up all of our free slots in the cache with them, we want
@@ -2661,7 +2691,7 @@ static u64 btrfs_alloc_from_bitmap(struct btrfs_block_group_cache *block_group,
 	search_start = min_start;
 	search_bytes = bytes;
 
-	err = search_bitmap(ctl, entry, &search_start, &search_bytes);
+	err = search_bitmap(ctl, entry, &search_start, &search_bytes, true);
 	if (err) {
 		if (search_bytes > *max_extent_size)
 			*max_extent_size = search_bytes;
@@ -2775,6 +2805,7 @@ static int btrfs_bitmap_cluster(struct btrfs_block_group_cache *block_group,
 	unsigned long want_bits;
 	unsigned long min_bits;
 	unsigned long found_bits;
+	unsigned long max_bits = 0;
 	unsigned long start = 0;
 	unsigned long total_found = 0;
 	int ret;
@@ -2784,6 +2815,13 @@ static int btrfs_bitmap_cluster(struct btrfs_block_group_cache *block_group,
 	want_bits = bytes_to_bits(bytes, ctl->unit);
 	min_bits = bytes_to_bits(min_bytes, ctl->unit);
 
+	/*
+	 * Don't bother looking for a cluster in this bitmap if it's heavily
+	 * fragmented.
+	 */
+	if (entry->max_extent_size &&
+	    entry->max_extent_size < cont1_bytes)
+		return -ENOSPC;
 again:
 	found_bits = 0;
 	for_each_set_bit_from(i, entry->bitmap, BITS_PER_BITMAP) {
@@ -2791,13 +2829,19 @@ static int btrfs_bitmap_cluster(struct btrfs_block_group_cache *block_group,
 					       BITS_PER_BITMAP, i);
 		if (next_zero - i >= min_bits) {
 			found_bits = next_zero - i;
+			if (found_bits > max_bits)
+				max_bits = found_bits;
 			break;
 		}
+		if (next_zero - i > max_bits)
+			max_bits = next_zero - i;
 		i = next_zero;
 	}
 
-	if (!found_bits)
+	if (!found_bits) {
+		entry->max_extent_size = (u64)max_bits * ctl->unit;
 		return -ENOSPC;
+	}
 
 	if (!total_found) {
 		start = i;
@@ -3056,6 +3100,7 @@ void btrfs_init_free_cluster(struct btrfs_free_cluster *cluster)
 	spin_lock_init(&cluster->refill_lock);
 	cluster->root = RB_ROOT;
 	cluster->max_size = 0;
+	cluster->fragmented = false;
 	INIT_LIST_HEAD(&cluster->block_group_list);
 	cluster->block_group = NULL;
 }
@@ -3223,7 +3268,7 @@ static int trim_bitmaps(struct btrfs_block_group_cache *block_group,
 		}
 
 		bytes = minlen;
-		ret2 = search_bitmap(ctl, entry, &start, &bytes);
+		ret2 = search_bitmap(ctl, entry, &start, &bytes, false);
 		if (ret2 || start >= end) {
 			spin_unlock(&ctl->tree_lock);
 			mutex_unlock(&ctl->cache_writeout_mutex);
@@ -3376,7 +3421,7 @@ u64 btrfs_find_ino_for_alloc(struct btrfs_root *fs_root)
 		u64 count = 1;
 		int ret;
 
-		ret = search_bitmap(ctl, entry, &offset, &count);
+		ret = search_bitmap(ctl, entry, &offset, &count, true);
 		/* Logic error; Should be empty if it can't find anything */
 		ASSERT(!ret);
 
@@ -3532,6 +3577,7 @@ int test_add_free_space_entry(struct btrfs_block_group_cache *cache,
 		spin_lock(&ctl->tree_lock);
 		info->offset = offset;
 		info->bytes = bytes;
+		info->max_extent_size = 0;
 		ret = link_free_space(ctl, info);
 		spin_unlock(&ctl->tree_lock);
 		if (ret)
@@ -3559,6 +3605,7 @@ int test_add_free_space_entry(struct btrfs_block_group_cache *cache,
 	}
 
 	bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes);
+
 	bytes -= bytes_added;
 	offset += bytes_added;
 	spin_unlock(&ctl->tree_lock);
@@ -3602,7 +3649,7 @@ int test_check_exists(struct btrfs_block_group_cache *cache,
 
 		bit_off = offset;
 		bit_bytes = ctl->unit;
-		ret = search_bitmap(ctl, info, &bit_off, &bit_bytes);
+		ret = search_bitmap(ctl, info, &bit_off, &bit_bytes, false);
 		if (!ret) {
 			if (bit_off == offset) {
 				ret = 1;

fs/btrfs/free-space-cache.h

@@ -23,6 +23,7 @@ struct btrfs_free_space {
 	struct rb_node offset_index;
 	u64 offset;
 	u64 bytes;
+	u64 max_extent_size;
 	unsigned long *bitmap;
 	struct list_head list;
 };

fs/btrfs/inode.c

@@ -9745,6 +9745,7 @@ static int __btrfs_prealloc_file_range(struct inode *inode, int mode,
 	u64 cur_offset = start;
 	u64 i_size;
 	u64 cur_bytes;
+	u64 last_alloc = (u64)-1;
 	int ret = 0;
 	bool own_trans = true;
 
@@ -9761,6 +9762,13 @@ static int __btrfs_prealloc_file_range(struct inode *inode, int mode,
 
 		cur_bytes = min(num_bytes, 256ULL * 1024 * 1024);
 		cur_bytes = max(cur_bytes, min_size);
+		/*
+		 * If we are severely fragmented we could end up with really
+		 * small allocations, so if the allocator is returning small
+		 * chunks lets make its job easier by only searching for those
+		 * sized chunks.
+		 */
+		cur_bytes = min(cur_bytes, last_alloc);
 		ret = btrfs_reserve_extent(root, cur_bytes, min_size, 0,
 					   *alloc_hint, &ins, 1, 0);
 		if (ret) {
@@ -9769,6 +9777,7 @@ static int __btrfs_prealloc_file_range(struct inode *inode, int mode,
 			break;
 		}
 
+		last_alloc = ins.offset;
 		ret = insert_reserved_file_extent(trans, inode,
 						  cur_offset, ins.objectid,
 						  ins.offset, ins.offset,

fs/btrfs/ordered-data.c

@@ -490,15 +490,16 @@ void btrfs_wait_logged_extents(struct btrfs_trans_handle *trans,
 
 	spin_lock_irq(&log->log_extents_lock[index]);
 	while (!list_empty(&log->logged_list[index])) {
+		struct inode *inode;
 		ordered = list_first_entry(&log->logged_list[index],
 					   struct btrfs_ordered_extent,
 					   log_list);
 		list_del_init(&ordered->log_list);
+		inode = ordered->inode;
 		spin_unlock_irq(&log->log_extents_lock[index]);
 
 		if (!test_bit(BTRFS_ORDERED_IO_DONE, &ordered->flags) &&
 		    !test_bit(BTRFS_ORDERED_DIRECT, &ordered->flags)) {
-			struct inode *inode = ordered->inode;
 			u64 start = ordered->file_offset;
 			u64 end = ordered->file_offset + ordered->len - 1;
 
@@ -509,20 +510,25 @@ void btrfs_wait_logged_extents(struct btrfs_trans_handle *trans,
 						   &ordered->flags));
 
 		/*
-		 * If our ordered extent completed it means it updated the
-		 * fs/subvol and csum trees already, so no need to make the
-		 * current transaction's commit wait for it, as we end up
-		 * holding memory unnecessarily and delaying the inode's iput
-		 * until the transaction commit (we schedule an iput for the
-		 * inode when the ordered extent's refcount drops to 0), which
-		 * prevents it from being evictable until the transaction
-		 * commits.
+		 * In order to keep us from losing our ordered extent
+		 * information when committing the transaction we have to make
+		 * sure that any logged extents are completed when we go to
+		 * commit the transaction.  To do this we simply increase the
+		 * current transactions pending_ordered counter and decrement it
+		 * when the ordered extent completes.
 		 */
-		if (test_bit(BTRFS_ORDERED_COMPLETE, &ordered->flags))
-			btrfs_put_ordered_extent(ordered);
-		else
-			list_add_tail(&ordered->trans_list, &trans->ordered);
-
+		if (!test_bit(BTRFS_ORDERED_COMPLETE, &ordered->flags)) {
+			struct btrfs_ordered_inode_tree *tree;
+
+			tree = &BTRFS_I(inode)->ordered_tree;
+			spin_lock_irq(&tree->lock);
+			if (!test_bit(BTRFS_ORDERED_COMPLETE, &ordered->flags)) {
+				set_bit(BTRFS_ORDERED_PENDING, &ordered->flags);
+				atomic_inc(&trans->transaction->pending_ordered);
+			}
+			spin_unlock_irq(&tree->lock);
+		}
+		btrfs_put_ordered_extent(ordered);
 		spin_lock_irq(&log->log_extents_lock[index]);
 	}
 	spin_unlock_irq(&log->log_extents_lock[index]);
@@ -584,6 +590,7 @@ void btrfs_remove_ordered_extent(struct inode *inode,
 	struct btrfs_ordered_inode_tree *tree;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct rb_node *node;
+	bool dec_pending_ordered = false;
 
 	tree = &BTRFS_I(inode)->ordered_tree;
 	spin_lock_irq(&tree->lock);
@@ -593,8 +600,37 @@ void btrfs_remove_ordered_extent(struct inode *inode,
 	if (tree->last == node)
 		tree->last = NULL;
 	set_bit(BTRFS_ORDERED_COMPLETE, &entry->flags);
+	if (test_and_clear_bit(BTRFS_ORDERED_PENDING, &entry->flags))
+		dec_pending_ordered = true;
 	spin_unlock_irq(&tree->lock);
 
+	/*
+	 * The current running transaction is waiting on us, we need to let it
+	 * know that we're complete and wake it up.
+	 */
+	if (dec_pending_ordered) {
+		struct btrfs_transaction *trans;
+
+		/*
+		 * The checks for trans are just a formality, it should be set,
+		 * but if it isn't we don't want to deref/assert under the spin
+		 * lock, so be nice and check if trans is set, but ASSERT() so
+		 * if it isn't set a developer will notice.
+		 */
+		spin_lock(&root->fs_info->trans_lock);
+		trans = root->fs_info->running_transaction;
+		if (trans)
+			atomic_inc(&trans->use_count);
+		spin_unlock(&root->fs_info->trans_lock);
+
+		ASSERT(trans);
+		if (trans) {
+			if (atomic_dec_and_test(&trans->pending_ordered))
+				wake_up(&trans->pending_wait);
+			btrfs_put_transaction(trans);
+		}
+	}
+
 	spin_lock(&root->ordered_extent_lock);
 	list_del_init(&entry->root_extent_list);
 	root->nr_ordered_extents--;

fs/btrfs/ordered-data.h

@@ -73,6 +73,8 @@ struct btrfs_ordered_sum {
 
 #define BTRFS_ORDERED_LOGGED 10 /* Set when we've waited on this ordered extent
 				 * in the logging code. */
+#define BTRFS_ORDERED_PENDING 11 /* We are waiting for this ordered extent to
+				  * complete in the current transaction. */
 struct btrfs_ordered_extent {
 	/* logical offset in the file */
 	u64 file_offset;

fs/btrfs/super.c

@@ -303,6 +303,9 @@ enum {
 	Opt_commit_interval, Opt_barrier, Opt_nodefrag, Opt_nodiscard,
 	Opt_noenospc_debug, Opt_noflushoncommit, Opt_acl, Opt_datacow,
 	Opt_datasum, Opt_treelog, Opt_noinode_cache,
+#ifdef CONFIG_BTRFS_DEBUG
+	Opt_fragment_data, Opt_fragment_metadata, Opt_fragment_all,
+#endif
 	Opt_err,
 };
 
@@ -355,6 +358,11 @@ static match_table_t tokens = {
 	{Opt_rescan_uuid_tree, "rescan_uuid_tree"},
 	{Opt_fatal_errors, "fatal_errors=%s"},
 	{Opt_commit_interval, "commit=%d"},
+#ifdef CONFIG_BTRFS_DEBUG
+	{Opt_fragment_data, "fragment=data"},
+	{Opt_fragment_metadata, "fragment=metadata"},
+	{Opt_fragment_all, "fragment=all"},
+#endif
 	{Opt_err, NULL},
 };
 
@@ -721,6 +729,22 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
 				info->commit_interval = BTRFS_DEFAULT_COMMIT_INTERVAL;
 			}
 			break;
+#ifdef CONFIG_BTRFS_DEBUG
+		case Opt_fragment_all:
+			btrfs_info(root->fs_info, "fragmenting all space");
+			btrfs_set_opt(info->mount_opt, FRAGMENT_DATA);
+			btrfs_set_opt(info->mount_opt, FRAGMENT_METADATA);
+			break;
+		case Opt_fragment_metadata:
+			btrfs_info(root->fs_info, "fragmenting metadata");
+			btrfs_set_opt(info->mount_opt,
+				      FRAGMENT_METADATA);
+			break;
+		case Opt_fragment_data:
+			btrfs_info(root->fs_info, "fragmenting data");
+			btrfs_set_opt(info->mount_opt, FRAGMENT_DATA);
+			break;
+#endif
 		case Opt_err:
 			btrfs_info(root->fs_info, "unrecognized mount option '%s'", p);
 			ret = -EINVAL;
@@ -1172,6 +1196,12 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 		seq_puts(seq, ",fatal_errors=panic");
 	if (info->commit_interval != BTRFS_DEFAULT_COMMIT_INTERVAL)
 		seq_printf(seq, ",commit=%d", info->commit_interval);
+#ifdef CONFIG_BTRFS_DEBUG
+	if (btrfs_test_opt(root, FRAGMENT_DATA))
+		seq_puts(seq, ",fragment=data");
+	if (btrfs_test_opt(root, FRAGMENT_METADATA))
+		seq_puts(seq, ",fragment=metadata");
+#endif
 	seq_printf(seq, ",subvolid=%llu",
 		  BTRFS_I(d_inode(dentry))->root->root_key.objectid);
 	seq_puts(seq, ",subvol=");

fs/btrfs/tests/free-space-tests.c

@@ -19,6 +19,7 @@
 #include <linux/slab.h>
 #include "btrfs-tests.h"
 #include "../ctree.h"
+#include "../disk-io.h"
 #include "../free-space-cache.h"
 
 #define BITS_PER_BITMAP		(PAGE_CACHE_SIZE * 8)
@@ -35,6 +36,12 @@ static struct btrfs_block_group_cache *init_test_block_group(void)
 		kfree(cache);
 		return NULL;
 	}
+	cache->fs_info = btrfs_alloc_dummy_fs_info();
+	if (!cache->fs_info) {
+		kfree(cache->free_space_ctl);
+		kfree(cache);
+		return NULL;
+	}
 
 	cache->key.objectid = 0;
 	cache->key.offset = 1024 * 1024 * 1024;
@@ -879,7 +886,8 @@ test_steal_space_from_bitmap_to_extent(struct btrfs_block_group_cache *cache)
 int btrfs_test_free_space_cache(void)
 {
 	struct btrfs_block_group_cache *cache;
-	int ret;
+	struct btrfs_root *root = NULL;
+	int ret = -ENOMEM;
 
 	test_msg("Running btrfs free space cache tests\n");
 
@@ -889,6 +897,17 @@ int btrfs_test_free_space_cache(void)
 		return 0;
 	}
 
+	root = btrfs_alloc_dummy_root();
+	if (!root)
+		goto out;
+
+	root->fs_info = btrfs_alloc_dummy_fs_info();
+	if (!root->fs_info)
+		goto out;
+
+	root->fs_info->extent_root = root;
+	cache->fs_info = root->fs_info;
+
 	ret = test_extents(cache);
 	if (ret)
 		goto out;
@@ -904,6 +923,7 @@ int btrfs_test_free_space_cache(void)
 	__btrfs_remove_free_space_cache(cache->free_space_ctl);
 	kfree(cache->free_space_ctl);
 	kfree(cache);
+	btrfs_free_dummy_root(root);
 	test_msg("Free space cache tests finished\n");
 	return ret;
 }

fs/btrfs/transaction.c

@@ -232,15 +232,16 @@ static noinline int join_transaction(struct btrfs_root *root, unsigned int type)
 	extwriter_counter_init(cur_trans, type);
 	init_waitqueue_head(&cur_trans->writer_wait);
 	init_waitqueue_head(&cur_trans->commit_wait);
+	init_waitqueue_head(&cur_trans->pending_wait);
 	cur_trans->state = TRANS_STATE_RUNNING;
 	/*
 	 * One for this trans handle, one so it will live on until we
 	 * commit the transaction.
 	 */
 	atomic_set(&cur_trans->use_count, 2);
-	cur_trans->have_free_bgs = 0;
+	atomic_set(&cur_trans->pending_ordered, 0);
+	cur_trans->flags = 0;
 	cur_trans->start_time = get_seconds();
-	cur_trans->dirty_bg_run = 0;
 
 	memset(&cur_trans->delayed_refs, 0, sizeof(cur_trans->delayed_refs));
 
@@ -266,7 +267,6 @@ static noinline int join_transaction(struct btrfs_root *root, unsigned int type)
 	INIT_LIST_HEAD(&cur_trans->pending_snapshots);
 	INIT_LIST_HEAD(&cur_trans->pending_chunks);
 	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);
 	INIT_LIST_HEAD(&cur_trans->dropped_roots);
@@ -549,7 +549,6 @@ start_transaction(struct btrfs_root *root, unsigned int num_items,
 	h->can_flush_pending_bgs = true;
 	INIT_LIST_HEAD(&h->qgroup_ref_list);
 	INIT_LIST_HEAD(&h->new_bgs);
-	INIT_LIST_HEAD(&h->ordered);
 
 	smp_mb();
 	if (cur_trans->state >= TRANS_STATE_BLOCKED &&
@@ -780,12 +779,6 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 	if (!list_empty(&trans->new_bgs))
 		btrfs_create_pending_block_groups(trans, root);
 
-	if (!list_empty(&trans->ordered)) {
-		spin_lock(&info->trans_lock);
-		list_splice_init(&trans->ordered, &cur_trans->pending_ordered);
-		spin_unlock(&info->trans_lock);
-	}
-
 	trans->delayed_ref_updates = 0;
 	if (!trans->sync) {
 		must_run_delayed_refs =
@@ -1776,25 +1769,10 @@ static inline void btrfs_wait_delalloc_flush(struct btrfs_fs_info *fs_info)
 }
 
 static inline void
-btrfs_wait_pending_ordered(struct btrfs_transaction *cur_trans,
-			   struct btrfs_fs_info *fs_info)
+btrfs_wait_pending_ordered(struct btrfs_transaction *cur_trans)
 {
-	struct btrfs_ordered_extent *ordered;
-
-	spin_lock(&fs_info->trans_lock);
-	while (!list_empty(&cur_trans->pending_ordered)) {
-		ordered = list_first_entry(&cur_trans->pending_ordered,
-					   struct btrfs_ordered_extent,
-					   trans_list);
-		list_del_init(&ordered->trans_list);
-		spin_unlock(&fs_info->trans_lock);
-
-		wait_event(ordered->wait, test_bit(BTRFS_ORDERED_COMPLETE,
-						   &ordered->flags));
-		btrfs_put_ordered_extent(ordered);
-		spin_lock(&fs_info->trans_lock);
-	}
-	spin_unlock(&fs_info->trans_lock);
+	wait_event(cur_trans->pending_wait,
+		   atomic_read(&cur_trans->pending_ordered) == 0);
 }
 
 int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
@@ -1842,7 +1820,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 		return ret;
 	}
 
-	if (!cur_trans->dirty_bg_run) {
+	if (!test_bit(BTRFS_TRANS_DIRTY_BG_RUN, &cur_trans->flags)) {
 		int run_it = 0;
 
 		/* this mutex is also taken before trying to set
@@ -1851,18 +1829,17 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 		 * 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
+		 * finds BTRFS_TRANS_DIRTY_BG_RUN set.
 		 *
-		 * The dirty_bg_run flag is also used to make sure only
-		 * one process starts all the block group IO.  It wouldn't
+		 * The BTRFS_TRANS_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) {
+		if (!test_and_set_bit(BTRFS_TRANS_DIRTY_BG_RUN,
+				      &cur_trans->flags))
 			run_it = 1;
-			cur_trans->dirty_bg_run = 1;
-		}
 		mutex_unlock(&root->fs_info->ro_block_group_mutex);
 
 		if (run_it)
@@ -1874,7 +1851,6 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 	}
 
 	spin_lock(&root->fs_info->trans_lock);
-	list_splice_init(&trans->ordered, &cur_trans->pending_ordered);
 	if (cur_trans->state >= TRANS_STATE_COMMIT_START) {
 		spin_unlock(&root->fs_info->trans_lock);
 		atomic_inc(&cur_trans->use_count);
@@ -1933,7 +1909,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 
 	btrfs_wait_delalloc_flush(root->fs_info);
 
-	btrfs_wait_pending_ordered(cur_trans, root->fs_info);
+	btrfs_wait_pending_ordered(cur_trans);
 
 	btrfs_scrub_pause(root);
 	/*
@@ -2133,7 +2109,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 
 	btrfs_finish_extent_commit(trans, root);
 
-	if (cur_trans->have_free_bgs)
+	if (test_bit(BTRFS_TRANS_HAVE_FREE_BGS, &cur_trans->flags))
 		btrfs_clear_space_info_full(root->fs_info);
 
 	root->fs_info->last_trans_committed = cur_trans->transid;

fs/btrfs/transaction.h

@@ -32,6 +32,10 @@ enum btrfs_trans_state {
 	TRANS_STATE_MAX			= 6,
 };
 
+#define BTRFS_TRANS_HAVE_FREE_BGS	0
+#define BTRFS_TRANS_DIRTY_BG_RUN	1
+#define BTRFS_TRANS_CACHE_ENOSPC	2
+
 struct btrfs_transaction {
 	u64 transid;
 	/*
@@ -46,11 +50,9 @@ struct btrfs_transaction {
 	 */
 	atomic_t num_writers;
 	atomic_t use_count;
+	atomic_t pending_ordered;
 
-	/*
-	 * true if there is free bgs operations in this transaction
-	 */
-	int have_free_bgs;
+	unsigned long flags;
 
 	/* Be protected by fs_info->trans_lock when we want to change it. */
 	enum btrfs_trans_state state;
@@ -59,9 +61,9 @@ struct btrfs_transaction {
 	unsigned long start_time;
 	wait_queue_head_t writer_wait;
 	wait_queue_head_t commit_wait;
+	wait_queue_head_t pending_wait;
 	struct list_head pending_snapshots;
 	struct list_head pending_chunks;
-	struct list_head pending_ordered;
 	struct list_head switch_commits;
 	struct list_head dirty_bgs;
 	struct list_head io_bgs;
@@ -80,7 +82,6 @@ struct btrfs_transaction {
 	spinlock_t dropped_roots_lock;
 	struct btrfs_delayed_ref_root delayed_refs;
 	int aborted;
-	int dirty_bg_run;
 };
 
 #define __TRANS_FREEZABLE	(1U << 0)
@@ -128,7 +129,6 @@ struct btrfs_trans_handle {
 	 */
 	struct btrfs_root *root;
 	struct seq_list delayed_ref_elem;
-	struct list_head ordered;
 	struct list_head qgroup_ref_list;
 	struct list_head new_bgs;
 };

fs/btrfs/volumes.c

@@ -1462,7 +1462,7 @@ static int btrfs_free_dev_extent(struct btrfs_trans_handle *trans,
 		btrfs_std_error(root->fs_info, ret,
 			    "Failed to remove dev extent item");
 	} else {
-		trans->transaction->have_free_bgs = 1;
+		set_bit(BTRFS_TRANS_HAVE_FREE_BGS, &trans->transaction->flags);
 	}
 out:
 	btrfs_free_path(path);