1 files changed, 605 insertions, 494 deletions

diff --git a/fs/btrfs/free-space-tree.c b/fs/btrfs/free-space-tree.c
index a5e34de06c2f..1ad2ad384b9e 100644
--- a/fs/btrfs/free-space-tree.c
+++ b/fs/btrfs/free-space-tree.c
@@ -1,47 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (C) 2015 Facebook.  All rights reserved.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public
- * License v2 as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public
- * License along with this program; if not, write to the
- * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
- * Boston, MA 021110-1307, USA.
  */
 
 #include <linux/kernel.h>
 #include <linux/sched/mm.h>
+#include "messages.h"
 #include "ctree.h"
 #include "disk-io.h"
 #include "locking.h"
 #include "free-space-tree.h"
 #include "transaction.h"
+#include "block-group.h"
+#include "fs.h"
+#include "accessors.h"
+#include "extent-tree.h"
+#include "root-tree.h"
 
 static int __add_block_group_free_space(struct btrfs_trans_handle *trans,
-					struct btrfs_fs_info *fs_info,
-					struct btrfs_block_group_cache *block_group,
+					struct btrfs_block_group *block_group,
 					struct btrfs_path *path);
 
-void set_free_space_tree_thresholds(struct btrfs_block_group_cache *cache)
+static struct btrfs_root *btrfs_free_space_root(
+				struct btrfs_block_group *block_group)
+{
+	struct btrfs_key key = {
+		.objectid = BTRFS_FREE_SPACE_TREE_OBJECTID,
+		.type = BTRFS_ROOT_ITEM_KEY,
+		.offset = 0,
+	};
+
+	if (btrfs_fs_incompat(block_group->fs_info, EXTENT_TREE_V2))
+		key.offset = block_group->global_root_id;
+	return btrfs_global_root(block_group->fs_info, &key);
+}
+
+void btrfs_set_free_space_tree_thresholds(struct btrfs_block_group *cache)
 {
 	u32 bitmap_range;
 	size_t bitmap_size;
 	u64 num_bitmaps, total_bitmap_size;
 
+	if (WARN_ON(cache->length == 0))
+		btrfs_warn(cache->fs_info, "block group %llu length is zero",
+			   cache->start);
+
 	/*
 	 * We convert to bitmaps when the disk space required for using extents
 	 * exceeds that required for using bitmaps.
 	 */
 	bitmap_range = cache->fs_info->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;
-	num_bitmaps = div_u64(cache->key.offset + bitmap_range - 1,
-			      bitmap_range);
+	num_bitmaps = div_u64(cache->length + bitmap_range - 1, bitmap_range);
 	bitmap_size = sizeof(struct btrfs_item) + BTRFS_FREE_SPACE_BITMAP_SIZE;
 	total_bitmap_size = num_bitmaps * bitmap_size;
 	cache->bitmap_high_thresh = div_u64(total_bitmap_size,
@@ -58,58 +67,54 @@ void set_free_space_tree_thresholds(struct btrfs_block_group_cache *cache)
 }
 
 static int add_new_free_space_info(struct btrfs_trans_handle *trans,
-				   struct btrfs_fs_info *fs_info,
-				   struct btrfs_block_group_cache *block_group,
+				   struct btrfs_block_group *block_group,
 				   struct btrfs_path *path)
 {
-	struct btrfs_root *root = fs_info->free_space_root;
+	struct btrfs_root *root = btrfs_free_space_root(block_group);
 	struct btrfs_free_space_info *info;
 	struct btrfs_key key;
 	struct extent_buffer *leaf;
 	int ret;
 
-	key.objectid = block_group->key.objectid;
+	key.objectid = block_group->start;
 	key.type = BTRFS_FREE_SPACE_INFO_KEY;
-	key.offset = block_group->key.offset;
+	key.offset = block_group->length;
 
 	ret = btrfs_insert_empty_item(trans, root, path, &key, sizeof(*info));
 	if (ret)
-		goto out;
+		return ret;
 
 	leaf = path->nodes[0];
 	info = btrfs_item_ptr(leaf, path->slots[0],
 			      struct btrfs_free_space_info);
 	btrfs_set_free_space_extent_count(leaf, info, 0);
 	btrfs_set_free_space_flags(leaf, info, 0);
-	btrfs_mark_buffer_dirty(leaf);
-
-	ret = 0;
-out:
 	btrfs_release_path(path);
-	return ret;
+	return 0;
 }
 
-struct btrfs_free_space_info *
-search_free_space_info(struct btrfs_trans_handle *trans,
-		       struct btrfs_fs_info *fs_info,
-		       struct btrfs_block_group_cache *block_group,
-		       struct btrfs_path *path, int cow)
+EXPORT_FOR_TESTS
+struct btrfs_free_space_info *btrfs_search_free_space_info(
+		struct btrfs_trans_handle *trans,
+		struct btrfs_block_group *block_group,
+		struct btrfs_path *path, int cow)
 {
-	struct btrfs_root *root = fs_info->free_space_root;
+	struct btrfs_fs_info *fs_info = block_group->fs_info;
+	struct btrfs_root *root = btrfs_free_space_root(block_group);
 	struct btrfs_key key;
 	int ret;
 
-	key.objectid = block_group->key.objectid;
+	key.objectid = block_group->start;
 	key.type = BTRFS_FREE_SPACE_INFO_KEY;
-	key.offset = block_group->key.offset;
+	key.offset = block_group->length;
 
 	ret = btrfs_search_slot(trans, root, &key, path, 0, cow);
 	if (ret < 0)
 		return ERR_PTR(ret);
 	if (ret != 0) {
 		btrfs_warn(fs_info, "missing free space info for %llu",
-			   block_group->key.objectid);
-		ASSERT(0);
+			   block_group->start);
+		DEBUG_WARN();
 		return ERR_PTR(-ENOENT);
 	}
 
@@ -132,13 +137,13 @@ static int btrfs_search_prev_slot(struct btrfs_trans_handle *trans,
 	if (ret < 0)
 		return ret;
 
-	if (ret == 0) {
-		ASSERT(0);
+	if (unlikely(ret == 0)) {
+		DEBUG_WARN();
 		return -EIO;
 	}
 
-	if (p->slots[0] == 0) {
-		ASSERT(0);
+	if (unlikely(p->slots[0] == 0)) {
+		DEBUG_WARN("no previous slot found");
 		return -EIO;
 	}
 	p->slots[0]--;
@@ -146,40 +151,62 @@ static int btrfs_search_prev_slot(struct btrfs_trans_handle *trans,
 	return 0;
 }
 
-static inline u32 free_space_bitmap_size(u64 size, u32 sectorsize)
+static inline u32 free_space_bitmap_size(const struct btrfs_fs_info *fs_info,
+					 u64 size)
 {
-	return DIV_ROUND_UP((u32)div_u64(size, sectorsize), BITS_PER_BYTE);
+	return DIV_ROUND_UP(size >> fs_info->sectorsize_bits, BITS_PER_BYTE);
 }
 
-static u8 *alloc_bitmap(u32 bitmap_size)
+static unsigned long *alloc_bitmap(u32 bitmap_size)
 {
-	u8 *ret;
+	unsigned long *ret;
 	unsigned int nofs_flag;
+	u32 bitmap_rounded_size = round_up(bitmap_size, sizeof(unsigned long));
 
 	/*
 	 * GFP_NOFS doesn't work with kvmalloc(), but we really can't recurse
-	 * into the filesystem as the free space bitmap can be modified in the
-	 * critical section of a transaction commit.
-	 *
-	 * TODO: push the memalloc_nofs_{save,restore}() to the caller where we
-	 * know that recursion is unsafe.
+	 * into the filesystem here. All callers hold a transaction handle
+	 * open, so if a GFP_KERNEL allocation recurses into the filesystem
+	 * and triggers a transaction commit, we would deadlock.
 	 */
 	nofs_flag = memalloc_nofs_save();
-	ret = kvzalloc(bitmap_size, GFP_KERNEL);
+	ret = kvzalloc(bitmap_rounded_size, GFP_KERNEL);
 	memalloc_nofs_restore(nofs_flag);
 	return ret;
 }
 
-int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
-				  struct btrfs_fs_info *fs_info,
-				  struct btrfs_block_group_cache *block_group,
-				  struct btrfs_path *path)
+static void le_bitmap_set(unsigned long *map, unsigned int start, int len)
+{
+	u8 *p = ((u8 *)map) + BIT_BYTE(start);
+	const unsigned int size = start + len;
+	int bits_to_set = BITS_PER_BYTE - (start % BITS_PER_BYTE);
+	u8 mask_to_set = BITMAP_FIRST_BYTE_MASK(start);
+
+	while (len - bits_to_set >= 0) {
+		*p |= mask_to_set;
+		len -= bits_to_set;
+		bits_to_set = BITS_PER_BYTE;
+		mask_to_set = ~0;
+		p++;
+	}
+	if (len) {
+		mask_to_set &= BITMAP_LAST_BYTE_MASK(size);
+		*p |= mask_to_set;
+	}
+}
+
+EXPORT_FOR_TESTS
+int btrfs_convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
+					struct btrfs_block_group *block_group,
+					struct btrfs_path *path)
 {
-	struct btrfs_root *root = fs_info->free_space_root;
+	struct btrfs_fs_info *fs_info = trans->fs_info;
+	struct btrfs_root *root = btrfs_free_space_root(block_group);
 	struct btrfs_free_space_info *info;
 	struct btrfs_key key, found_key;
 	struct extent_buffer *leaf;
-	u8 *bitmap, *bitmap_cursor;
+	unsigned long *bitmap;
+	char *bitmap_cursor;
 	u64 start, end;
 	u64 bitmap_range, i;
 	u32 bitmap_size, flags, expected_extent_count;
@@ -187,16 +214,13 @@ int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
 	int done = 0, nr;
 	int ret;
 
-	bitmap_size = free_space_bitmap_size(block_group->key.offset,
-					     fs_info->sectorsize);
+	bitmap_size = free_space_bitmap_size(fs_info, block_group->length);
 	bitmap = alloc_bitmap(bitmap_size);
-	if (!bitmap) {
-		ret = -ENOMEM;
-		goto out;
-	}
+	if (unlikely(!bitmap))
+		return 0;
 
-	start = block_group->key.objectid;
-	end = block_group->key.objectid + block_group->key.offset;
+	start = block_group->start;
+	end = block_group->start + block_group->length;
 
 	key.objectid = end - 1;
 	key.type = (u8)-1;
@@ -204,8 +228,10 @@ int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
 
 	while (!done) {
 		ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
-		if (ret)
+		if (unlikely(ret)) {
+			btrfs_abort_transaction(trans, ret);
 			goto out;
+		}
 
 		leaf = path->nodes[0];
 		nr = 0;
@@ -214,8 +240,8 @@ int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
 			btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
 
 			if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
-				ASSERT(found_key.objectid == block_group->key.objectid);
-				ASSERT(found_key.offset == block_group->key.offset);
+				ASSERT(found_key.objectid == block_group->start);
+				ASSERT(found_key.offset == block_group->length);
 				done = 1;
 				break;
 			} else if (found_key.type == BTRFS_FREE_SPACE_EXTENT_KEY) {
@@ -240,35 +266,39 @@ int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
 		}
 
 		ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
-		if (ret)
+		if (unlikely(ret)) {
+			btrfs_abort_transaction(trans, ret);
 			goto out;
+		}
 		btrfs_release_path(path);
 	}
 
-	info = search_free_space_info(trans, fs_info, block_group, path, 1);
+	info = btrfs_search_free_space_info(trans, block_group, path, 1);
 	if (IS_ERR(info)) {
 		ret = PTR_ERR(info);
+		btrfs_abort_transaction(trans, ret);
 		goto out;
 	}
 	leaf = path->nodes[0];
 	flags = btrfs_free_space_flags(leaf, info);
 	flags |= BTRFS_FREE_SPACE_USING_BITMAPS;
+	block_group->using_free_space_bitmaps = true;
+	block_group->using_free_space_bitmaps_cached = true;
 	btrfs_set_free_space_flags(leaf, info, flags);
 	expected_extent_count = btrfs_free_space_extent_count(leaf, info);
-	btrfs_mark_buffer_dirty(leaf);
 	btrfs_release_path(path);
 
-	if (extent_count != expected_extent_count) {
+	if (unlikely(extent_count != expected_extent_count)) {
 		btrfs_err(fs_info,
 			  "incorrect extent count for %llu; counted %u, expected %u",
-			  block_group->key.objectid, extent_count,
+			  block_group->start, extent_count,
 			  expected_extent_count);
-		ASSERT(0);
 		ret = -EIO;
+		btrfs_abort_transaction(trans, ret);
 		goto out;
 	}
 
-	bitmap_cursor = bitmap;
+	bitmap_cursor = (char *)bitmap;
 	bitmap_range = fs_info->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;
 	i = start;
 	while (i < end) {
@@ -277,8 +307,7 @@ int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
 		u32 data_size;
 
 		extent_size = min(end - i, bitmap_range);
-		data_size = free_space_bitmap_size(extent_size,
-						   fs_info->sectorsize);
+		data_size = free_space_bitmap_size(fs_info, extent_size);
 
 		key.objectid = i;
 		key.type = BTRFS_FREE_SPACE_BITMAP_KEY;
@@ -286,14 +315,15 @@ int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
 
 		ret = btrfs_insert_empty_item(trans, root, path, &key,
 					      data_size);
-		if (ret)
+		if (unlikely(ret)) {
+			btrfs_abort_transaction(trans, ret);
 			goto out;
+		}
 
 		leaf = path->nodes[0];
 		ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
 		write_extent_buffer(leaf, bitmap_cursor, ptr,
 				    data_size);
-		btrfs_mark_buffer_dirty(leaf);
 		btrfs_release_path(path);
 
 		i += extent_size;
@@ -303,41 +333,34 @@ int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
 	ret = 0;
 out:
 	kvfree(bitmap);
-	if (ret)
-		btrfs_abort_transaction(trans, ret);
 	return ret;
 }
 
-int convert_free_space_to_extents(struct btrfs_trans_handle *trans,
-				  struct btrfs_fs_info *fs_info,
-				  struct btrfs_block_group_cache *block_group,
-				  struct btrfs_path *path)
+EXPORT_FOR_TESTS
+int btrfs_convert_free_space_to_extents(struct btrfs_trans_handle *trans,
+					struct btrfs_block_group *block_group,
+					struct btrfs_path *path)
 {
-	struct btrfs_root *root = fs_info->free_space_root;
+	struct btrfs_fs_info *fs_info = trans->fs_info;
+	struct btrfs_root *root = btrfs_free_space_root(block_group);
 	struct btrfs_free_space_info *info;
 	struct btrfs_key key, found_key;
 	struct extent_buffer *leaf;
-	u8 *bitmap;
+	unsigned long *bitmap;
 	u64 start, end;
-	/* Initialize to silence GCC. */
-	u64 extent_start = 0;
-	u64 offset;
 	u32 bitmap_size, flags, expected_extent_count;
-	int prev_bit = 0, bit, bitnr;
+	unsigned long nrbits, start_bit, end_bit;
 	u32 extent_count = 0;
 	int done = 0, nr;
 	int ret;
 
-	bitmap_size = free_space_bitmap_size(block_group->key.offset,
-					     fs_info->sectorsize);
+	bitmap_size = free_space_bitmap_size(fs_info, block_group->length);
 	bitmap = alloc_bitmap(bitmap_size);
-	if (!bitmap) {
-		ret = -ENOMEM;
-		goto out;
-	}
+	if (unlikely(!bitmap))
+		return 0;
 
-	start = block_group->key.objectid;
-	end = block_group->key.objectid + block_group->key.offset;
+	start = block_group->start;
+	end = block_group->start + block_group->length;
 
 	key.objectid = end - 1;
 	key.type = (u8)-1;
@@ -345,8 +368,10 @@ int convert_free_space_to_extents(struct btrfs_trans_handle *trans,
 
 	while (!done) {
 		ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
-		if (ret)
+		if (unlikely(ret)) {
+			btrfs_abort_transaction(trans, ret);
 			goto out;
+		}
 
 		leaf = path->nodes[0];
 		nr = 0;
@@ -355,13 +380,13 @@ int convert_free_space_to_extents(struct btrfs_trans_handle *trans,
 			btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
 
 			if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
-				ASSERT(found_key.objectid == block_group->key.objectid);
-				ASSERT(found_key.offset == block_group->key.offset);
+				ASSERT(found_key.objectid == block_group->start);
+				ASSERT(found_key.offset == block_group->length);
 				done = 1;
 				break;
 			} else if (found_key.type == BTRFS_FREE_SPACE_BITMAP_KEY) {
 				unsigned long ptr;
-				u8 *bitmap_cursor;
+				char *bitmap_cursor;
 				u32 bitmap_pos, data_size;
 
 				ASSERT(found_key.objectid >= start);
@@ -371,96 +396,85 @@ int convert_free_space_to_extents(struct btrfs_trans_handle *trans,
 				bitmap_pos = div_u64(found_key.objectid - start,
 						     fs_info->sectorsize *
 						     BITS_PER_BYTE);
-				bitmap_cursor = bitmap + bitmap_pos;
-				data_size = free_space_bitmap_size(found_key.offset,
-								   fs_info->sectorsize);
+				bitmap_cursor = ((char *)bitmap) + bitmap_pos;
+				data_size = free_space_bitmap_size(fs_info,
+								found_key.offset);
 
-				ptr = btrfs_item_ptr_offset(leaf, path->slots[0] - 1);
+				path->slots[0]--;
+				ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
 				read_extent_buffer(leaf, bitmap_cursor, ptr,
 						   data_size);
 
 				nr++;
-				path->slots[0]--;
 			} else {
 				ASSERT(0);
 			}
 		}
 
 		ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
-		if (ret)
+		if (unlikely(ret)) {
+			btrfs_abort_transaction(trans, ret);
 			goto out;
+		}
 		btrfs_release_path(path);
 	}
 
-	info = search_free_space_info(trans, fs_info, block_group, path, 1);
+	info = btrfs_search_free_space_info(trans, block_group, path, 1);
 	if (IS_ERR(info)) {
 		ret = PTR_ERR(info);
+		btrfs_abort_transaction(trans, ret);
 		goto out;
 	}
 	leaf = path->nodes[0];
 	flags = btrfs_free_space_flags(leaf, info);
 	flags &= ~BTRFS_FREE_SPACE_USING_BITMAPS;
+	block_group->using_free_space_bitmaps = false;
+	block_group->using_free_space_bitmaps_cached = true;
 	btrfs_set_free_space_flags(leaf, info, flags);
 	expected_extent_count = btrfs_free_space_extent_count(leaf, info);
-	btrfs_mark_buffer_dirty(leaf);
 	btrfs_release_path(path);
 
-	offset = start;
-	bitnr = 0;
-	while (offset < end) {
-		bit = !!le_test_bit(bitnr, bitmap);
-		if (prev_bit == 0 && bit == 1) {
-			extent_start = offset;
-		} else if (prev_bit == 1 && bit == 0) {
-			key.objectid = extent_start;
-			key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
-			key.offset = offset - extent_start;
-
-			ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
-			if (ret)
-				goto out;
-			btrfs_release_path(path);
+	nrbits = block_group->length >> fs_info->sectorsize_bits;
+	start_bit = find_next_bit_le(bitmap, nrbits, 0);
 
-			extent_count++;
-		}
-		prev_bit = bit;
-		offset += fs_info->sectorsize;
-		bitnr++;
-	}
-	if (prev_bit == 1) {
-		key.objectid = extent_start;
+	while (start_bit < nrbits) {
+		end_bit = find_next_zero_bit_le(bitmap, nrbits, start_bit);
+		ASSERT(start_bit < end_bit);
+
+		key.objectid = start + start_bit * fs_info->sectorsize;
 		key.type = BTRFS_FREE_SPACE_EXTENT_KEY;
-		key.offset = end - extent_start;
+		key.offset = (end_bit - start_bit) * fs_info->sectorsize;
 
 		ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
-		if (ret)
+		if (unlikely(ret)) {
+			btrfs_abort_transaction(trans, ret);
 			goto out;
+		}
 		btrfs_release_path(path);
 
 		extent_count++;
+
+		start_bit = find_next_bit_le(bitmap, nrbits, end_bit);
 	}
 
-	if (extent_count != expected_extent_count) {
+	if (unlikely(extent_count != expected_extent_count)) {
 		btrfs_err(fs_info,
 			  "incorrect extent count for %llu; counted %u, expected %u",
-			  block_group->key.objectid, extent_count,
+			  block_group->start, extent_count,
 			  expected_extent_count);
-		ASSERT(0);
 		ret = -EIO;
+		btrfs_abort_transaction(trans, ret);
 		goto out;
 	}
 
 	ret = 0;
 out:
 	kvfree(bitmap);
-	if (ret)
-		btrfs_abort_transaction(trans, ret);
 	return ret;
 }
 
 static int update_free_space_extent_count(struct btrfs_trans_handle *trans,
-					  struct btrfs_fs_info *fs_info,
-					  struct btrfs_block_group_cache *block_group,
+					  struct btrfs_block_group *block_group,
 					  struct btrfs_path *path,
 					  int new_extents)
 {
@@ -472,35 +486,31 @@ static int update_free_space_extent_count(struct btrfs_trans_handle *trans,
 	if (new_extents == 0)
 		return 0;
 
-	info = search_free_space_info(trans, fs_info, block_group, path, 1);
-	if (IS_ERR(info)) {
-		ret = PTR_ERR(info);
-		goto out;
-	}
+	info = btrfs_search_free_space_info(trans, block_group, path, 1);
+	if (IS_ERR(info))
+		return PTR_ERR(info);
+
 	flags = btrfs_free_space_flags(path->nodes[0], info);
 	extent_count = btrfs_free_space_extent_count(path->nodes[0], info);
 
 	extent_count += new_extents;
 	btrfs_set_free_space_extent_count(path->nodes[0], info, extent_count);
-	btrfs_mark_buffer_dirty(path->nodes[0]);
 	btrfs_release_path(path);
 
 	if (!(flags & BTRFS_FREE_SPACE_USING_BITMAPS) &&
 	    extent_count > block_group->bitmap_high_thresh) {
-		ret = convert_free_space_to_bitmaps(trans, fs_info, block_group,
-						    path);
+		ret = btrfs_convert_free_space_to_bitmaps(trans, block_group, path);
 	} else if ((flags & BTRFS_FREE_SPACE_USING_BITMAPS) &&
 		   extent_count < block_group->bitmap_low_thresh) {
-		ret = convert_free_space_to_extents(trans, fs_info, block_group,
-						    path);
+		ret = btrfs_convert_free_space_to_extents(trans, block_group, path);
 	}
 
-out:
 	return ret;
 }
 
-int free_space_test_bit(struct btrfs_block_group_cache *block_group,
-			struct btrfs_path *path, u64 offset)
+EXPORT_FOR_TESTS
+bool btrfs_free_space_test_bit(struct btrfs_block_group *block_group,
+			       struct btrfs_path *path, u64 offset)
 {
 	struct extent_buffer *leaf;
 	struct btrfs_key key;
@@ -518,12 +528,13 @@ int free_space_test_bit(struct btrfs_block_group_cache *block_group,
 	ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
 	i = div_u64(offset - found_start,
 		    block_group->fs_info->sectorsize);
-	return !!extent_buffer_test_bit(leaf, ptr, i);
+	return extent_buffer_test_bit(leaf, ptr, i);
 }
 
-static void free_space_set_bits(struct btrfs_block_group_cache *block_group,
-				struct btrfs_path *path, u64 *start, u64 *size,
-				int bit)
+static void free_space_modify_bits(struct btrfs_trans_handle *trans,
+				   struct btrfs_block_group *block_group,
+				   struct btrfs_path *path, u64 *start, u64 *size,
+				   bool set_bits)
 {
 	struct btrfs_fs_info *fs_info = block_group->fs_info;
 	struct extent_buffer *leaf;
@@ -545,13 +556,13 @@ static void free_space_set_bits(struct btrfs_block_group_cache *block_group,
 		end = found_end;
 
 	ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
-	first = div_u64(*start - found_start, fs_info->sectorsize);
-	last = div_u64(end - found_start, fs_info->sectorsize);
-	if (bit)
+	first = (*start - found_start) >> fs_info->sectorsize_bits;
+	last = (end - found_start) >> fs_info->sectorsize_bits;
+	if (set_bits)
 		extent_buffer_bitmap_set(leaf, ptr, first, last - first);
 	else
 		extent_buffer_bitmap_clear(leaf, ptr, first, last - first);
-	btrfs_mark_buffer_dirty(leaf);
+	btrfs_mark_buffer_dirty(trans, leaf);
 
 	*size -= end - *start;
 	*start = end;
@@ -589,16 +600,16 @@ static int free_space_next_bitmap(struct btrfs_trans_handle *trans,
  * the bitmap.
  */
 static int modify_free_space_bitmap(struct btrfs_trans_handle *trans,
-				    struct btrfs_fs_info *fs_info,
-				    struct btrfs_block_group_cache *block_group,
+				    struct btrfs_block_group *block_group,
 				    struct btrfs_path *path,
-				    u64 start, u64 size, int remove)
+				    u64 start, u64 size, bool remove)
 {
-	struct btrfs_root *root = fs_info->free_space_root;
+	struct btrfs_root *root = btrfs_free_space_root(block_group);
 	struct btrfs_key key;
 	u64 end = start + size;
 	u64 cur_start, cur_size;
-	int prev_bit, next_bit;
+	bool prev_bit_set = false;
+	bool next_bit_set = false;
 	int new_extents;
 	int ret;
 
@@ -606,7 +617,7 @@ static int modify_free_space_bitmap(struct btrfs_trans_handle *trans,
 	 * Read the bit for the block immediately before the extent of space if
 	 * that block is within the block group.
 	 */
-	if (start > block_group->key.objectid) {
+	if (start > block_group->start) {
 		u64 prev_block = start - block_group->fs_info->sectorsize;
 
 		key.objectid = prev_block;
@@ -615,16 +626,16 @@ static int modify_free_space_bitmap(struct btrfs_trans_handle *trans,
 
 		ret = btrfs_search_prev_slot(trans, root, &key, path, 0, 1);
 		if (ret)
-			goto out;
+			return ret;
 
-		prev_bit = free_space_test_bit(block_group, path, prev_block);
+		prev_bit_set = btrfs_free_space_test_bit(block_group, path, prev_block);
 
 		/* The previous block may have been in the previous bitmap. */
 		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 		if (start >= key.objectid + key.offset) {
 			ret = free_space_next_bitmap(trans, root, path);
 			if (ret)
-				goto out;
+				return ret;
 		}
 	} else {
 		key.objectid = start;
@@ -633,9 +644,7 @@ static int modify_free_space_bitmap(struct btrfs_trans_handle *trans,
 
 		ret = btrfs_search_prev_slot(trans, root, &key, path, 0, 1);
 		if (ret)
-			goto out;
-
-		prev_bit = -1;
+			return ret;
 	}
 
 	/*
@@ -645,70 +654,63 @@ static int modify_free_space_bitmap(struct btrfs_trans_handle *trans,
 	cur_start = start;
 	cur_size = size;
 	while (1) {
-		free_space_set_bits(block_group, path, &cur_start, &cur_size,
-				    !remove);
+		free_space_modify_bits(trans, block_group, path, &cur_start,
+				       &cur_size, !remove);
 		if (cur_size == 0)
 			break;
 		ret = free_space_next_bitmap(trans, root, path);
 		if (ret)
-			goto out;
+			return ret;
 	}
 
 	/*
 	 * Read the bit for the block immediately after the extent of space if
 	 * that block is within the block group.
 	 */
-	if (end < block_group->key.objectid + block_group->key.offset) {
+	if (end < block_group->start + block_group->length) {
 		/* The next block may be in the next bitmap. */
 		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 		if (end >= key.objectid + key.offset) {
 			ret = free_space_next_bitmap(trans, root, path);
 			if (ret)
-				goto out;
+				return ret;
 		}
 
-		next_bit = free_space_test_bit(block_group, path, end);
-	} else {
-		next_bit = -1;
+		next_bit_set = btrfs_free_space_test_bit(block_group, path, end);
 	}
 
 	if (remove) {
 		new_extents = -1;
-		if (prev_bit == 1) {
+		if (prev_bit_set) {
 			/* Leftover on the left. */
 			new_extents++;
 		}
-		if (next_bit == 1) {
+		if (next_bit_set) {
 			/* Leftover on the right. */
 			new_extents++;
 		}
 	} else {
 		new_extents = 1;
-		if (prev_bit == 1) {
+		if (prev_bit_set) {
 			/* Merging with neighbor on the left. */
 			new_extents--;
 		}
-		if (next_bit == 1) {
+		if (next_bit_set) {
 			/* Merging with neighbor on the right. */
 			new_extents--;
 		}
 	}
 
 	btrfs_release_path(path);
-	ret = update_free_space_extent_count(trans, fs_info, block_group, path,
-					     new_extents);
-
-out:
-	return ret;
+	return update_free_space_extent_count(trans, block_group, path, new_extents);
 }
 
 static int remove_free_space_extent(struct btrfs_trans_handle *trans,
-				    struct btrfs_fs_info *fs_info,
-				    struct btrfs_block_group_cache *block_group,
+				    struct btrfs_block_group *block_group,
 				    struct btrfs_path *path,
 				    u64 start, u64 size)
 {
-	struct btrfs_root *root = fs_info->free_space_root;
+	struct btrfs_root *root = btrfs_free_space_root(block_group);
 	struct btrfs_key key;
 	u64 found_start, found_end;
 	u64 end = start + size;
@@ -721,7 +723,7 @@ static int remove_free_space_extent(struct btrfs_trans_handle *trans,
 
 	ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 	if (ret)
-		goto out;
+		return ret;
 
 	btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 
@@ -753,7 +755,7 @@ static int remove_free_space_extent(struct btrfs_trans_handle *trans,
 	/* Delete the existing key (cases 1-4). */
 	ret = btrfs_del_item(trans, root, path);
 	if (ret)
-		goto out;
+		return ret;
 
 	/* Add a key for leftovers at the beginning (cases 3 and 4). */
 	if (start > found_start) {
@@ -764,7 +766,7 @@ static int remove_free_space_extent(struct btrfs_trans_handle *trans,
 		btrfs_release_path(path);
 		ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
 		if (ret)
-			goto out;
+			return ret;
 		new_extents++;
 	}
 
@@ -777,93 +779,98 @@ static int remove_free_space_extent(struct btrfs_trans_handle *trans,
 		btrfs_release_path(path);
 		ret = btrfs_insert_empty_item(trans, root, path, &key, 0);
 		if (ret)
-			goto out;
+			return ret;
 		new_extents++;
 	}
 
 	btrfs_release_path(path);
-	ret = update_free_space_extent_count(trans, fs_info, block_group, path,
-					     new_extents);
-
-out:
-	return ret;
+	return update_free_space_extent_count(trans, block_group, path, new_extents);
 }
 
-int __remove_from_free_space_tree(struct btrfs_trans_handle *trans,
-				  struct btrfs_fs_info *fs_info,
-				  struct btrfs_block_group_cache *block_group,
-				  struct btrfs_path *path, u64 start, u64 size)
+static int using_bitmaps(struct btrfs_block_group *bg, struct btrfs_path *path)
 {
 	struct btrfs_free_space_info *info;
 	u32 flags;
-	int ret;
 
-	if (block_group->needs_free_space) {
-		ret = __add_block_group_free_space(trans, fs_info, block_group,
-						   path);
-		if (ret)
-			return ret;
-	}
+	if (bg->using_free_space_bitmaps_cached)
+		return bg->using_free_space_bitmaps;
 
-	info = search_free_space_info(NULL, fs_info, block_group, path, 0);
+	info = btrfs_search_free_space_info(NULL, bg, path, 0);
 	if (IS_ERR(info))
 		return PTR_ERR(info);
 	flags = btrfs_free_space_flags(path->nodes[0], info);
 	btrfs_release_path(path);
 
-	if (flags & BTRFS_FREE_SPACE_USING_BITMAPS) {
-		return modify_free_space_bitmap(trans, fs_info, block_group,
-						path, start, size, 1);
-	} else {
-		return remove_free_space_extent(trans, fs_info, block_group,
-						path, start, size);
-	}
+	bg->using_free_space_bitmaps = (flags & BTRFS_FREE_SPACE_USING_BITMAPS);
+	bg->using_free_space_bitmaps_cached = true;
+
+	return bg->using_free_space_bitmaps;
+}
+
+EXPORT_FOR_TESTS
+int __btrfs_remove_from_free_space_tree(struct btrfs_trans_handle *trans,
+					struct btrfs_block_group *block_group,
+					struct btrfs_path *path, u64 start, u64 size)
+{
+	int ret;
+
+	ret = __add_block_group_free_space(trans, block_group, path);
+	if (ret)
+		return ret;
+
+	ret = using_bitmaps(block_group, path);
+	if (ret < 0)
+		return ret;
+
+	if (ret)
+		return modify_free_space_bitmap(trans, block_group, path,
+						start, size, true);
+
+	return remove_free_space_extent(trans, block_group, path, start, size);
 }
 
-int remove_from_free_space_tree(struct btrfs_trans_handle *trans,
-				struct btrfs_fs_info *fs_info,
-				u64 start, u64 size)
+int btrfs_remove_from_free_space_tree(struct btrfs_trans_handle *trans,
+				      u64 start, u64 size)
 {
-	struct btrfs_block_group_cache *block_group;
-	struct btrfs_path *path;
+	struct btrfs_block_group *block_group;
+	BTRFS_PATH_AUTO_FREE(path);
 	int ret;
 
-	if (!btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE))
+	if (!btrfs_fs_compat_ro(trans->fs_info, FREE_SPACE_TREE))
 		return 0;
 
 	path = btrfs_alloc_path();
-	if (!path) {
+	if (unlikely(!path)) {
 		ret = -ENOMEM;
-		goto out;
+		btrfs_abort_transaction(trans, ret);
+		return ret;
 	}
 
-	block_group = btrfs_lookup_block_group(fs_info, start);
-	if (!block_group) {
-		ASSERT(0);
+	block_group = btrfs_lookup_block_group(trans->fs_info, start);
+	if (unlikely(!block_group)) {
+		DEBUG_WARN("no block group found for start=%llu", start);
 		ret = -ENOENT;
-		goto out;
+		btrfs_abort_transaction(trans, ret);
+		return ret;
 	}
 
 	mutex_lock(&block_group->free_space_lock);
-	ret = __remove_from_free_space_tree(trans, fs_info, block_group, path,
-					    start, size);
+	ret = __btrfs_remove_from_free_space_tree(trans, block_group, path, start, size);
 	mutex_unlock(&block_group->free_space_lock);
-
-	btrfs_put_block_group(block_group);
-out:
-	btrfs_free_path(path);
 	if (ret)
 		btrfs_abort_transaction(trans, ret);
+
+	btrfs_put_block_group(block_group);
+
 	return ret;
 }
 
 static int add_free_space_extent(struct btrfs_trans_handle *trans,
-				 struct btrfs_fs_info *fs_info,
-				 struct btrfs_block_group_cache *block_group,
+				 struct btrfs_block_group *block_group,
 				 struct btrfs_path *path,
 				 u64 start, u64 size)
 {
-	struct btrfs_root *root = fs_info->free_space_root;
+	struct btrfs_root *root = btrfs_free_space_root(block_group);
 	struct btrfs_key key, new_key;
 	u64 found_start, found_end;
 	u64 end = start + size;
@@ -893,7 +900,7 @@ static int add_free_space_extent(struct btrfs_trans_handle *trans,
 	new_key.offset = size;
 
 	/* Search for a neighbor on the left. */
-	if (start == block_group->key.objectid)
+	if (start == block_group->start)
 		goto right;
 	key.objectid = start - 1;
 	key.type = (u8)-1;
@@ -901,7 +908,7 @@ static int add_free_space_extent(struct btrfs_trans_handle *trans,
 
 	ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 	if (ret)
-		goto out;
+		return ret;
 
 	btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 
@@ -913,8 +920,8 @@ static int add_free_space_extent(struct btrfs_trans_handle *trans,
 
 	found_start = key.objectid;
 	found_end = key.objectid + key.offset;
-	ASSERT(found_start >= block_group->key.objectid &&
-	       found_end > block_group->key.objectid);
+	ASSERT(found_start >= block_group->start &&
+	       found_end > block_group->start);
 	ASSERT(found_start < start && found_end <= start);
 
 	/*
@@ -924,7 +931,7 @@ static int add_free_space_extent(struct btrfs_trans_handle *trans,
 	if (found_end == start) {
 		ret = btrfs_del_item(trans, root, path);
 		if (ret)
-			goto out;
+			return ret;
 		new_key.objectid = found_start;
 		new_key.offset += key.offset;
 		new_extents--;
@@ -933,7 +940,7 @@ static int add_free_space_extent(struct btrfs_trans_handle *trans,
 
 right:
 	/* Search for a neighbor on the right. */
-	if (end == block_group->key.objectid + block_group->key.offset)
+	if (end == block_group->start + block_group->length)
 		goto insert;
 	key.objectid = end;
 	key.type = (u8)-1;
@@ -941,7 +948,7 @@ right:
 
 	ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
 	if (ret)
-		goto out;
+		return ret;
 
 	btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 
@@ -953,8 +960,8 @@ right:
 
 	found_start = key.objectid;
 	found_end = key.objectid + key.offset;
-	ASSERT(found_start >= block_group->key.objectid &&
-	       found_end > block_group->key.objectid);
+	ASSERT(found_start >= block_group->start &&
+	       found_end > block_group->start);
 	ASSERT((found_start < start && found_end <= start) ||
 	       (found_start >= end && found_end > end));
 
@@ -965,7 +972,7 @@ right:
 	if (found_start == end) {
 		ret = btrfs_del_item(trans, root, path);
 		if (ret)
-			goto out;
+			return ret;
 		new_key.offset += key.offset;
 		new_extents--;
 	}
@@ -975,81 +982,67 @@ insert:
 	/* Insert the new key (cases 1-4). */
 	ret = btrfs_insert_empty_item(trans, root, path, &new_key, 0);
 	if (ret)
-		goto out;
+		return ret;
 
 	btrfs_release_path(path);
-	ret = update_free_space_extent_count(trans, fs_info, block_group, path,
-					     new_extents);
-
-out:
-	return ret;
+	return update_free_space_extent_count(trans, block_group, path, new_extents);
 }
 
-int __add_to_free_space_tree(struct btrfs_trans_handle *trans,
-			     struct btrfs_fs_info *fs_info,
-			     struct btrfs_block_group_cache *block_group,
-			     struct btrfs_path *path, u64 start, u64 size)
+EXPORT_FOR_TESTS
+int __btrfs_add_to_free_space_tree(struct btrfs_trans_handle *trans,
+				   struct btrfs_block_group *block_group,
+				   struct btrfs_path *path, u64 start, u64 size)
 {
-	struct btrfs_free_space_info *info;
-	u32 flags;
 	int ret;
 
-	if (block_group->needs_free_space) {
-		ret = __add_block_group_free_space(trans, fs_info, block_group,
-						   path);
-		if (ret)
-			return ret;
-	}
+	ret = __add_block_group_free_space(trans, block_group, path);
+	if (ret)
+		return ret;
 
-	info = search_free_space_info(NULL, fs_info, block_group, path, 0);
-	if (IS_ERR(info))
-		return PTR_ERR(info);
-	flags = btrfs_free_space_flags(path->nodes[0], info);
-	btrfs_release_path(path);
+	ret = using_bitmaps(block_group, path);
+	if (ret < 0)
+		return ret;
 
-	if (flags & BTRFS_FREE_SPACE_USING_BITMAPS) {
-		return modify_free_space_bitmap(trans, fs_info, block_group,
-						path, start, size, 0);
-	} else {
-		return add_free_space_extent(trans, fs_info, block_group, path,
-					     start, size);
-	}
+	if (ret)
+		return modify_free_space_bitmap(trans, block_group, path,
+						start, size, false);
+
+	return add_free_space_extent(trans, block_group, path, start, size);
 }
 
-int add_to_free_space_tree(struct btrfs_trans_handle *trans,
-			   struct btrfs_fs_info *fs_info,
-			   u64 start, u64 size)
+int btrfs_add_to_free_space_tree(struct btrfs_trans_handle *trans,
+				 u64 start, u64 size)
 {
-	struct btrfs_block_group_cache *block_group;
-	struct btrfs_path *path;
+	struct btrfs_block_group *block_group;
+	BTRFS_PATH_AUTO_FREE(path);
 	int ret;
 
-	if (!btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE))
+	if (!btrfs_fs_compat_ro(trans->fs_info, FREE_SPACE_TREE))
 		return 0;
 
 	path = btrfs_alloc_path();
-	if (!path) {
+	if (unlikely(!path)) {
 		ret = -ENOMEM;
-		goto out;
+		btrfs_abort_transaction(trans, ret);
+		return ret;
 	}
 
-	block_group = btrfs_lookup_block_group(fs_info, start);
-	if (!block_group) {
-		ASSERT(0);
+	block_group = btrfs_lookup_block_group(trans->fs_info, start);
+	if (unlikely(!block_group)) {
+		DEBUG_WARN("no block group found for start=%llu", start);
 		ret = -ENOENT;
-		goto out;
+		btrfs_abort_transaction(trans, ret);
+		return ret;
 	}
 
 	mutex_lock(&block_group->free_space_lock);
-	ret = __add_to_free_space_tree(trans, fs_info, block_group, path, start,
-				       size);
+	ret = __btrfs_add_to_free_space_tree(trans, block_group, path, start, size);
 	mutex_unlock(&block_group->free_space_lock);
-
-	btrfs_put_block_group(block_group);
-out:
-	btrfs_free_path(path);
 	if (ret)
 		btrfs_abort_transaction(trans, ret);
+
+	btrfs_put_block_group(block_group);
+
 	return ret;
 }
 
@@ -1059,11 +1052,11 @@ out:
  * through the normal add/remove hooks.
  */
 static int populate_free_space_tree(struct btrfs_trans_handle *trans,
-				    struct btrfs_fs_info *fs_info,
-				    struct btrfs_block_group_cache *block_group)
+				    struct btrfs_block_group *block_group)
 {
-	struct btrfs_root *extent_root = fs_info->extent_root;
-	struct btrfs_path *path, *path2;
+	struct btrfs_root *extent_root;
+	BTRFS_PATH_AUTO_FREE(path);
+	BTRFS_PATH_AUTO_FREE(path2);
 	struct btrfs_key key;
 	u64 start, end;
 	int ret;
@@ -1071,17 +1064,16 @@ static int populate_free_space_tree(struct btrfs_trans_handle *trans,
 	path = btrfs_alloc_path();
 	if (!path)
 		return -ENOMEM;
-	path->reada = 1;
 
 	path2 = btrfs_alloc_path();
-	if (!path2) {
-		btrfs_free_path(path);
+	if (!path2)
 		return -ENOMEM;
-	}
 
-	ret = add_new_free_space_info(trans, fs_info, block_group, path2);
+	path->reada = READA_FORWARD;
+
+	ret = add_new_free_space_info(trans, block_group, path2);
 	if (ret)
-		goto out;
+		return ret;
 
 	mutex_lock(&block_group->free_space_lock);
 
@@ -1092,18 +1084,30 @@ static int populate_free_space_tree(struct btrfs_trans_handle *trans,
 	 * BLOCK_GROUP_ITEM, so an extent may precede the block group that it's
 	 * contained in.
 	 */
-	key.objectid = block_group->key.objectid;
+	key.objectid = block_group->start;
 	key.type = BTRFS_EXTENT_ITEM_KEY;
 	key.offset = 0;
 
+	extent_root = btrfs_extent_root(trans->fs_info, key.objectid);
 	ret = btrfs_search_slot_for_read(extent_root, &key, path, 1, 0);
 	if (ret < 0)
 		goto out_locked;
-	ASSERT(ret == 0);
-
-	start = block_group->key.objectid;
-	end = block_group->key.objectid + block_group->key.offset;
-	while (1) {
+	/*
+	 * If ret is 1 (no key found), it means this is an empty block group,
+	 * without any extents allocated from it and there's no block group
+	 * item (key BTRFS_BLOCK_GROUP_ITEM_KEY) located in the extent tree
+	 * because we are using the block group tree feature (so block group
+	 * items are stored in the block group tree) or this is a new block
+	 * group created in the current transaction and its block group item
+	 * was not yet inserted in the extent tree (that happens in
+	 * btrfs_create_pending_block_groups() -> insert_block_group_item()).
+	 * It also means there are no extents allocated for block groups with a
+	 * start offset beyond this block group's end offset (this is the last,
+	 * highest, block group).
+	 */
+	start = block_group->start;
+	end = block_group->start + block_group->length;
+	while (ret == 0) {
 		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
 
 		if (key.type == BTRFS_EXTENT_ITEM_KEY ||
@@ -1112,33 +1116,31 @@ static int populate_free_space_tree(struct btrfs_trans_handle *trans,
 				break;
 
 			if (start < key.objectid) {
-				ret = __add_to_free_space_tree(trans, fs_info,
-							       block_group,
-							       path2, start,
-							       key.objectid -
-							       start);
+				ret = __btrfs_add_to_free_space_tree(trans,
+								     block_group,
+								     path2, start,
+								     key.objectid -
+								     start);
 				if (ret)
 					goto out_locked;
 			}
 			start = key.objectid;
 			if (key.type == BTRFS_METADATA_ITEM_KEY)
-				start += fs_info->nodesize;
+				start += trans->fs_info->nodesize;
 			else
 				start += key.offset;
 		} else if (key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
-			if (key.objectid != block_group->key.objectid)
+			if (key.objectid != block_group->start)
 				break;
 		}
 
 		ret = btrfs_next_item(extent_root, path);
 		if (ret < 0)
 			goto out_locked;
-		if (ret)
-			break;
 	}
 	if (start < end) {
-		ret = __add_to_free_space_tree(trans, fs_info, block_group,
-					       path2, start, end - start);
+		ret = __btrfs_add_to_free_space_tree(trans, block_group, path2,
+						     start, end - start);
 		if (ret)
 			goto out_locked;
 	}
@@ -1146,9 +1148,7 @@ static int populate_free_space_tree(struct btrfs_trans_handle *trans,
 	ret = 0;
 out_locked:
 	mutex_unlock(&block_group->free_space_lock);
-out:
-	btrfs_free_path(path2);
-	btrfs_free_path(path);
+
 	return ret;
 }
 
@@ -1157,7 +1157,7 @@ int btrfs_create_free_space_tree(struct btrfs_fs_info *fs_info)
 	struct btrfs_trans_handle *trans;
 	struct btrfs_root *tree_root = fs_info->tree_root;
 	struct btrfs_root *free_space_root;
-	struct btrfs_block_group_cache *block_group;
+	struct btrfs_block_group *block_group;
 	struct rb_node *node;
 	int ret;
 
@@ -1166,42 +1166,60 @@ int btrfs_create_free_space_tree(struct btrfs_fs_info *fs_info)
 		return PTR_ERR(trans);
 
 	set_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
-	free_space_root = btrfs_create_tree(trans, fs_info,
+	set_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags);
+	free_space_root = btrfs_create_tree(trans,
 					    BTRFS_FREE_SPACE_TREE_OBJECTID);
 	if (IS_ERR(free_space_root)) {
 		ret = PTR_ERR(free_space_root);
-		goto abort;
+		btrfs_abort_transaction(trans, ret);
+		btrfs_end_transaction(trans);
+		goto out_clear;
+	}
+	ret = btrfs_global_root_insert(free_space_root);
+	if (unlikely(ret)) {
+		btrfs_put_root(free_space_root);
+		btrfs_abort_transaction(trans, ret);
+		btrfs_end_transaction(trans);
+		goto out_clear;
 	}
-	fs_info->free_space_root = free_space_root;
 
-	node = rb_first(&fs_info->block_group_cache_tree);
+	node = rb_first_cached(&fs_info->block_group_cache_tree);
 	while (node) {
-		block_group = rb_entry(node, struct btrfs_block_group_cache,
+		block_group = rb_entry(node, struct btrfs_block_group,
 				       cache_node);
-		ret = populate_free_space_tree(trans, fs_info, block_group);
-		if (ret)
-			goto abort;
+		ret = populate_free_space_tree(trans, block_group);
+		if (unlikely(ret)) {
+			btrfs_abort_transaction(trans, ret);
+			btrfs_end_transaction(trans);
+			goto out_clear;
+		}
 		node = rb_next(node);
 	}
 
 	btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE);
 	btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID);
 	clear_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
+	ret = btrfs_commit_transaction(trans);
 
-	return btrfs_commit_transaction(trans);
+	/*
+	 * Now that we've committed the transaction any reading of our commit
+	 * root will be safe, so we can cache from the free space tree now.
+	 */
+	clear_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags);
+	return ret;
 
-abort:
+out_clear:
 	clear_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
-	btrfs_abort_transaction(trans, ret);
-	btrfs_end_transaction(trans);
+	clear_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags);
 	return ret;
 }
 
 static int clear_free_space_tree(struct btrfs_trans_handle *trans,
 				 struct btrfs_root *root)
 {
-	struct btrfs_path *path;
+	BTRFS_PATH_AUTO_FREE(path);
 	struct btrfs_key key;
+	struct rb_node *node;
 	int nr;
 	int ret;
 
@@ -1209,8 +1227,6 @@ static int clear_free_space_tree(struct btrfs_trans_handle *trans,
 	if (!path)
 		return -ENOMEM;
 
-	path->leave_spinning = 1;
-
 	key.objectid = 0;
 	key.type = 0;
 	key.offset = 0;
@@ -1218,7 +1234,7 @@ static int clear_free_space_tree(struct btrfs_trans_handle *trans,
 	while (1) {
 		ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 		if (ret < 0)
-			goto out;
+			return ret;
 
 		nr = btrfs_header_nritems(path->nodes[0]);
 		if (!nr)
@@ -1227,22 +1243,34 @@ static int clear_free_space_tree(struct btrfs_trans_handle *trans,
 		path->slots[0] = 0;
 		ret = btrfs_del_items(trans, root, path, 0, nr);
 		if (ret)
-			goto out;
+			return ret;
 
 		btrfs_release_path(path);
 	}
 
-	ret = 0;
-out:
-	btrfs_free_path(path);
-	return ret;
+	node = rb_first_cached(&trans->fs_info->block_group_cache_tree);
+	while (node) {
+		struct btrfs_block_group *bg;
+
+		bg = rb_entry(node, struct btrfs_block_group, cache_node);
+		clear_bit(BLOCK_GROUP_FLAG_FREE_SPACE_ADDED, &bg->runtime_flags);
+		node = rb_next(node);
+		cond_resched();
+	}
+
+	return 0;
 }
 
-int btrfs_clear_free_space_tree(struct btrfs_fs_info *fs_info)
+int btrfs_delete_free_space_tree(struct btrfs_fs_info *fs_info)
 {
 	struct btrfs_trans_handle *trans;
 	struct btrfs_root *tree_root = fs_info->tree_root;
-	struct btrfs_root *free_space_root = fs_info->free_space_root;
+	struct btrfs_key key = {
+		.objectid = BTRFS_FREE_SPACE_TREE_OBJECTID,
+		.type = BTRFS_ROOT_ITEM_KEY,
+		.offset = 0,
+	};
+	struct btrfs_root *free_space_root = btrfs_global_root(fs_info, &key);
 	int ret;
 
 	trans = btrfs_start_transaction(tree_root, 0);
@@ -1251,116 +1279,207 @@ int btrfs_clear_free_space_tree(struct btrfs_fs_info *fs_info)
 
 	btrfs_clear_fs_compat_ro(fs_info, FREE_SPACE_TREE);
 	btrfs_clear_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID);
-	fs_info->free_space_root = NULL;
 
 	ret = clear_free_space_tree(trans, free_space_root);
-	if (ret)
-		goto abort;
+	if (unlikely(ret)) {
+		btrfs_abort_transaction(trans, ret);
+		btrfs_end_transaction(trans);
+		return ret;
+	}
 
-	ret = btrfs_del_root(trans, tree_root, &free_space_root->root_key);
-	if (ret)
-		goto abort;
+	ret = btrfs_del_root(trans, &free_space_root->root_key);
+	if (unlikely(ret)) {
+		btrfs_abort_transaction(trans, ret);
+		btrfs_end_transaction(trans);
+		return ret;
+	}
 
+	btrfs_global_root_delete(free_space_root);
+
+	spin_lock(&fs_info->trans_lock);
 	list_del(&free_space_root->dirty_list);
+	spin_unlock(&fs_info->trans_lock);
 
 	btrfs_tree_lock(free_space_root->node);
-	clean_tree_block(fs_info, free_space_root->node);
+	btrfs_clear_buffer_dirty(trans, free_space_root->node);
 	btrfs_tree_unlock(free_space_root->node);
-	btrfs_free_tree_block(trans, free_space_root, free_space_root->node,
-			      0, 1);
-
-	free_extent_buffer(free_space_root->node);
-	free_extent_buffer(free_space_root->commit_root);
-	kfree(free_space_root);
+	ret = btrfs_free_tree_block(trans, btrfs_root_id(free_space_root),
+				    free_space_root->node, 0, 1);
+	btrfs_put_root(free_space_root);
+	if (unlikely(ret < 0)) {
+		btrfs_abort_transaction(trans, ret);
+		btrfs_end_transaction(trans);
+		return ret;
+	}
 
 	return btrfs_commit_transaction(trans);
-
-abort:
-	btrfs_abort_transaction(trans, ret);
-	btrfs_end_transaction(trans);
-	return ret;
 }
 
-static int __add_block_group_free_space(struct btrfs_trans_handle *trans,
-					struct btrfs_fs_info *fs_info,
-					struct btrfs_block_group_cache *block_group,
-					struct btrfs_path *path)
+int btrfs_rebuild_free_space_tree(struct btrfs_fs_info *fs_info)
 {
-	u64 start, end;
+	struct btrfs_trans_handle *trans;
+	struct btrfs_key key = {
+		.objectid = BTRFS_FREE_SPACE_TREE_OBJECTID,
+		.type = BTRFS_ROOT_ITEM_KEY,
+		.offset = 0,
+	};
+	struct btrfs_root *free_space_root = btrfs_global_root(fs_info, &key);
+	struct rb_node *node;
 	int ret;
 
-	start = block_group->key.objectid;
-	end = block_group->key.objectid + block_group->key.offset;
+	trans = btrfs_start_transaction(free_space_root, 1);
+	if (IS_ERR(trans))
+		return PTR_ERR(trans);
 
-	block_group->needs_free_space = 0;
+	set_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
+	set_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags);
 
-	ret = add_new_free_space_info(trans, fs_info, block_group, path);
-	if (ret)
+	ret = clear_free_space_tree(trans, free_space_root);
+	if (unlikely(ret)) {
+		btrfs_abort_transaction(trans, ret);
+		btrfs_end_transaction(trans);
 		return ret;
+	}
+
+	node = rb_first_cached(&fs_info->block_group_cache_tree);
+	while (node) {
+		struct btrfs_block_group *block_group;
 
-	return __add_to_free_space_tree(trans, fs_info, block_group, path,
-					block_group->key.objectid,
-					block_group->key.offset);
+		block_group = rb_entry(node, struct btrfs_block_group,
+				       cache_node);
+
+		if (test_bit(BLOCK_GROUP_FLAG_FREE_SPACE_ADDED,
+			     &block_group->runtime_flags))
+			goto next;
+
+		ret = populate_free_space_tree(trans, block_group);
+		if (unlikely(ret)) {
+			btrfs_abort_transaction(trans, ret);
+			btrfs_end_transaction(trans);
+			return ret;
+		}
+next:
+		if (btrfs_should_end_transaction(trans)) {
+			btrfs_end_transaction(trans);
+			trans = btrfs_start_transaction(free_space_root, 1);
+			if (IS_ERR(trans))
+				return PTR_ERR(trans);
+		}
+		node = rb_next(node);
+	}
+
+	btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE);
+	btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID);
+	clear_bit(BTRFS_FS_CREATING_FREE_SPACE_TREE, &fs_info->flags);
+
+	ret = btrfs_commit_transaction(trans);
+	clear_bit(BTRFS_FS_FREE_SPACE_TREE_UNTRUSTED, &fs_info->flags);
+	return ret;
 }
 
-int add_block_group_free_space(struct btrfs_trans_handle *trans,
-			       struct btrfs_fs_info *fs_info,
-			       struct btrfs_block_group_cache *block_group)
+static int __add_block_group_free_space(struct btrfs_trans_handle *trans,
+					struct btrfs_block_group *block_group,
+					struct btrfs_path *path)
 {
-	struct btrfs_path *path = NULL;
-	int ret = 0;
+	bool own_path = false;
+	int ret;
 
-	if (!btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE))
+	if (!test_and_clear_bit(BLOCK_GROUP_FLAG_NEEDS_FREE_SPACE,
+				&block_group->runtime_flags))
 		return 0;
 
-	mutex_lock(&block_group->free_space_lock);
-	if (!block_group->needs_free_space)
-		goto out;
+	/*
+	 * While rebuilding the free space tree we may allocate new metadata
+	 * block groups while modifying the free space tree.
+	 *
+	 * Because during the rebuild (at btrfs_rebuild_free_space_tree()) we
+	 * can use multiple transactions, every time btrfs_end_transaction() is
+	 * called at btrfs_rebuild_free_space_tree() we finish the creation of
+	 * new block groups by calling btrfs_create_pending_block_groups(), and
+	 * that in turn calls us, through add_block_group_free_space(), to add
+	 * a free space info item and a free space extent item for the block
+	 * group.
+	 *
+	 * Then later btrfs_rebuild_free_space_tree() may find such new block
+	 * groups and processes them with populate_free_space_tree(), which can
+	 * fail with EEXIST since there are already items for the block group in
+	 * the free space tree. Notice that we say "may find" because a new
+	 * block group may be added to the block groups rbtree in a node before
+	 * or after the block group currently being processed by the rebuild
+	 * process. So signal the rebuild process to skip such new block groups
+	 * if it finds them.
+	 */
+	set_bit(BLOCK_GROUP_FLAG_FREE_SPACE_ADDED, &block_group->runtime_flags);
 
-	path = btrfs_alloc_path();
 	if (!path) {
-		ret = -ENOMEM;
+		path = btrfs_alloc_path();
+		if (unlikely(!path)) {
+			btrfs_abort_transaction(trans, -ENOMEM);
+			return -ENOMEM;
+		}
+		own_path = true;
+	}
+
+	ret = add_new_free_space_info(trans, block_group, path);
+	if (unlikely(ret)) {
+		btrfs_abort_transaction(trans, ret);
 		goto out;
 	}
 
-	ret = __add_block_group_free_space(trans, fs_info, block_group, path);
+	ret = __btrfs_add_to_free_space_tree(trans, block_group, path,
+					     block_group->start, block_group->length);
+	if (ret)
+		btrfs_abort_transaction(trans, ret);
 
 out:
-	btrfs_free_path(path);
+	if (own_path)
+		btrfs_free_path(path);
+
+	return ret;
+}
+
+int btrfs_add_block_group_free_space(struct btrfs_trans_handle *trans,
+				     struct btrfs_block_group *block_group)
+{
+	int ret;
+
+	if (!btrfs_fs_compat_ro(trans->fs_info, FREE_SPACE_TREE))
+		return 0;
+
+	mutex_lock(&block_group->free_space_lock);
+	ret = __add_block_group_free_space(trans, block_group, NULL);
 	mutex_unlock(&block_group->free_space_lock);
-	if (ret)
-		btrfs_abort_transaction(trans, ret);
 	return ret;
 }
 
-int remove_block_group_free_space(struct btrfs_trans_handle *trans,
-				  struct btrfs_fs_info *fs_info,
-				  struct btrfs_block_group_cache *block_group)
+int btrfs_remove_block_group_free_space(struct btrfs_trans_handle *trans,
+					struct btrfs_block_group *block_group)
 {
-	struct btrfs_root *root = fs_info->free_space_root;
-	struct btrfs_path *path;
+	struct btrfs_root *root = btrfs_free_space_root(block_group);
+	BTRFS_PATH_AUTO_FREE(path);
 	struct btrfs_key key, found_key;
 	struct extent_buffer *leaf;
 	u64 start, end;
 	int done = 0, nr;
 	int ret;
 
-	if (!btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE))
+	if (!btrfs_fs_compat_ro(trans->fs_info, FREE_SPACE_TREE))
 		return 0;
 
-	if (block_group->needs_free_space) {
+	if (test_bit(BLOCK_GROUP_FLAG_NEEDS_FREE_SPACE, &block_group->runtime_flags)) {
 		/* We never added this block group to the free space tree. */
 		return 0;
 	}
 
 	path = btrfs_alloc_path();
-	if (!path) {
+	if (unlikely(!path)) {
 		ret = -ENOMEM;
-		goto out;
+		btrfs_abort_transaction(trans, ret);
+		return ret;
 	}
 
-	start = block_group->key.objectid;
-	end = block_group->key.objectid + block_group->key.offset;
+	start = block_group->start;
+	end = block_group->start + block_group->length;
 
 	key.objectid = end - 1;
 	key.type = (u8)-1;
@@ -1368,8 +1487,10 @@ int remove_block_group_free_space(struct btrfs_trans_handle *trans,
 
 	while (!done) {
 		ret = btrfs_search_prev_slot(trans, root, &key, path, -1, 1);
-		if (ret)
-			goto out;
+		if (unlikely(ret)) {
+			btrfs_abort_transaction(trans, ret);
+			return ret;
+		}
 
 		leaf = path->nodes[0];
 		nr = 0;
@@ -1378,8 +1499,8 @@ int remove_block_group_free_space(struct btrfs_trans_handle *trans,
 			btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0] - 1);
 
 			if (found_key.type == BTRFS_FREE_SPACE_INFO_KEY) {
-				ASSERT(found_key.objectid == block_group->key.objectid);
-				ASSERT(found_key.offset == block_group->key.offset);
+				ASSERT(found_key.objectid == block_group->start);
+				ASSERT(found_key.offset == block_group->length);
 				done = 1;
 				nr++;
 				path->slots[0]--;
@@ -1397,16 +1518,15 @@ int remove_block_group_free_space(struct btrfs_trans_handle *trans,
 		}
 
 		ret = btrfs_del_items(trans, root, path, path->slots[0], nr);
-		if (ret)
-			goto out;
+		if (unlikely(ret)) {
+			btrfs_abort_transaction(trans, ret);
+			return ret;
+		}
 		btrfs_release_path(path);
 	}
 
 	ret = 0;
-out:
-	btrfs_free_path(path);
-	if (ret)
-		btrfs_abort_transaction(trans, ret);
+
 	return ret;
 }
 
@@ -1414,11 +1534,11 @@ static int load_free_space_bitmaps(struct btrfs_caching_control *caching_ctl,
 				   struct btrfs_path *path,
 				   u32 expected_extent_count)
 {
-	struct btrfs_block_group_cache *block_group;
+	struct btrfs_block_group *block_group;
 	struct btrfs_fs_info *fs_info;
 	struct btrfs_root *root;
 	struct btrfs_key key;
-	int prev_bit = 0, bit;
+	bool prev_bit_set = false;
 	/* Initialize to silence GCC. */
 	u64 extent_start = 0;
 	u64 end, offset;
@@ -1428,14 +1548,14 @@ static int load_free_space_bitmaps(struct btrfs_caching_control *caching_ctl,
 
 	block_group = caching_ctl->block_group;
 	fs_info = block_group->fs_info;
-	root = fs_info->free_space_root;
+	root = btrfs_free_space_root(block_group);
 
-	end = block_group->key.objectid + block_group->key.offset;
+	end = block_group->start + block_group->length;
 
 	while (1) {
 		ret = btrfs_next_item(root, path);
 		if (ret < 0)
-			goto out;
+			return ret;
 		if (ret)
 			break;
 
@@ -1447,56 +1567,57 @@ static int load_free_space_bitmaps(struct btrfs_caching_control *caching_ctl,
 		ASSERT(key.type == BTRFS_FREE_SPACE_BITMAP_KEY);
 		ASSERT(key.objectid < end && key.objectid + key.offset <= end);
 
-		caching_ctl->progress = key.objectid;
-
 		offset = key.objectid;
 		while (offset < key.objectid + key.offset) {
-			bit = free_space_test_bit(block_group, path, offset);
-			if (prev_bit == 0 && bit == 1) {
+			bool bit_set;
+
+			bit_set = btrfs_free_space_test_bit(block_group, path, offset);
+			if (!prev_bit_set && bit_set) {
 				extent_start = offset;
-			} else if (prev_bit == 1 && bit == 0) {
-				total_found += add_new_free_space(block_group,
-								  fs_info,
-								  extent_start,
-								  offset);
+			} else if (prev_bit_set && !bit_set) {
+				u64 space_added;
+
+				ret = btrfs_add_new_free_space(block_group,
+							       extent_start,
+							       offset,
+							       &space_added);
+				if (ret)
+					return ret;
+				total_found += space_added;
 				if (total_found > CACHING_CTL_WAKE_UP) {
 					total_found = 0;
 					wake_up(&caching_ctl->wait);
 				}
 				extent_count++;
 			}
-			prev_bit = bit;
+			prev_bit_set = bit_set;
 			offset += fs_info->sectorsize;
 		}
 	}
-	if (prev_bit == 1) {
-		total_found += add_new_free_space(block_group, fs_info,
-						  extent_start, end);
+	if (prev_bit_set) {
+		ret = btrfs_add_new_free_space(block_group, extent_start, end, NULL);
+		if (ret)
+			return ret;
 		extent_count++;
 	}
 
-	if (extent_count != expected_extent_count) {
+	if (unlikely(extent_count != expected_extent_count)) {
 		btrfs_err(fs_info,
 			  "incorrect extent count for %llu; counted %u, expected %u",
-			  block_group->key.objectid, extent_count,
+			  block_group->start, extent_count,
 			  expected_extent_count);
-		ASSERT(0);
-		ret = -EIO;
-		goto out;
+		DEBUG_WARN();
+		return -EIO;
 	}
 
-	caching_ctl->progress = (u64)-1;
-
-	ret = 0;
-out:
-	return ret;
+	return 0;
 }
 
 static int load_free_space_extents(struct btrfs_caching_control *caching_ctl,
 				   struct btrfs_path *path,
 				   u32 expected_extent_count)
 {
-	struct btrfs_block_group_cache *block_group;
+	struct btrfs_block_group *block_group;
 	struct btrfs_fs_info *fs_info;
 	struct btrfs_root *root;
 	struct btrfs_key key;
@@ -1507,14 +1628,16 @@ static int load_free_space_extents(struct btrfs_caching_control *caching_ctl,
 
 	block_group = caching_ctl->block_group;
 	fs_info = block_group->fs_info;
-	root = fs_info->free_space_root;
+	root = btrfs_free_space_root(block_group);
 
-	end = block_group->key.objectid + block_group->key.offset;
+	end = block_group->start + block_group->length;
 
 	while (1) {
+		u64 space_added;
+
 		ret = btrfs_next_item(root, path);
 		if (ret < 0)
-			goto out;
+			return ret;
 		if (ret)
 			break;
 
@@ -1526,11 +1649,12 @@ static int load_free_space_extents(struct btrfs_caching_control *caching_ctl,
 		ASSERT(key.type == BTRFS_FREE_SPACE_EXTENT_KEY);
 		ASSERT(key.objectid < end && key.objectid + key.offset <= end);
 
-		caching_ctl->progress = key.objectid;
-
-		total_found += add_new_free_space(block_group, fs_info,
-						  key.objectid,
-						  key.objectid + key.offset);
+		ret = btrfs_add_new_free_space(block_group, key.objectid,
+					       key.objectid + key.offset,
+					       &space_added);
+		if (ret)
+			return ret;
+		total_found += space_added;
 		if (total_found > CACHING_CTL_WAKE_UP) {
 			total_found = 0;
 			wake_up(&caching_ctl->wait);
@@ -1538,34 +1662,26 @@ static int load_free_space_extents(struct btrfs_caching_control *caching_ctl,
 		extent_count++;
 	}
 
-	if (extent_count != expected_extent_count) {
+	if (unlikely(extent_count != expected_extent_count)) {
 		btrfs_err(fs_info,
 			  "incorrect extent count for %llu; counted %u, expected %u",
-			  block_group->key.objectid, extent_count,
+			  block_group->start, extent_count,
 			  expected_extent_count);
-		ASSERT(0);
-		ret = -EIO;
-		goto out;
+		DEBUG_WARN();
+		return -EIO;
 	}
 
-	caching_ctl->progress = (u64)-1;
-
-	ret = 0;
-out:
-	return ret;
+	return 0;
 }
 
-int load_free_space_tree(struct btrfs_caching_control *caching_ctl)
+int btrfs_load_free_space_tree(struct btrfs_caching_control *caching_ctl)
 {
-	struct btrfs_block_group_cache *block_group;
-	struct btrfs_fs_info *fs_info;
+	struct btrfs_block_group *block_group;
 	struct btrfs_free_space_info *info;
-	struct btrfs_path *path;
+	BTRFS_PATH_AUTO_FREE(path);
 	u32 extent_count, flags;
-	int ret;
 
 	block_group = caching_ctl->block_group;
-	fs_info = block_group->fs_info;
 
 	path = btrfs_alloc_path();
 	if (!path)
@@ -1575,15 +1691,14 @@ int load_free_space_tree(struct btrfs_caching_control *caching_ctl)
 	 * Just like caching_thread() doesn't want to deadlock on the extent
 	 * tree, we don't want to deadlock on the free space tree.
 	 */
-	path->skip_locking = 1;
-	path->search_commit_root = 1;
-	path->reada = 1;
+	path->skip_locking = true;
+	path->search_commit_root = true;
+	path->reada = READA_FORWARD;
+
+	info = btrfs_search_free_space_info(NULL, block_group, path, 0);
+	if (IS_ERR(info))
+		return PTR_ERR(info);
 
-	info = search_free_space_info(NULL, fs_info, block_group, path, 0);
-	if (IS_ERR(info)) {
-		ret = PTR_ERR(info);
-		goto out;
-	}
 	extent_count = btrfs_free_space_extent_count(path->nodes[0], info);
 	flags = btrfs_free_space_flags(path->nodes[0], info);
 
@@ -1593,11 +1708,7 @@ int load_free_space_tree(struct btrfs_caching_control *caching_ctl)
 	 * there.
 	 */
 	if (flags & BTRFS_FREE_SPACE_USING_BITMAPS)
-		ret = load_free_space_bitmaps(caching_ctl, path, extent_count);
+		return load_free_space_bitmaps(caching_ctl, path, extent_count);
 	else
-		ret = load_free_space_extents(caching_ctl, path, extent_count);
-
-out:
-	btrfs_free_path(path);
-	return ret;
+		return load_free_space_extents(caching_ctl, path, extent_count);
 }