Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4292 insertions, 0 deletions

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
new file mode 100644
index 000000000..b27795e13
--- /dev/null
+++ b/fs/btrfs/free-space-cache.c
@@ -0,0 +1,4292 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2008 Red Hat.  All rights reserved.
+ */
+
+#include <linux/pagemap.h>
+#include <linux/sched.h>
+#include <linux/sched/signal.h>
+#include <linux/slab.h>
+#include <linux/math64.h>
+#include <linux/ratelimit.h>
+#include <linux/error-injection.h>
+#include <linux/sched/mm.h>
+#include "misc.h"
+#include "ctree.h"
+#include "free-space-cache.h"
+#include "transaction.h"
+#include "disk-io.h"
+#include "extent_io.h"
+#include "volumes.h"
+#include "space-info.h"
+#include "delalloc-space.h"
+#include "block-group.h"
+#include "discard.h"
+#include "subpage.h"
+#include "inode-item.h"
+
+#define BITS_PER_BITMAP		(PAGE_SIZE * 8UL)
+#define MAX_CACHE_BYTES_PER_GIG	SZ_64K
+#define FORCE_EXTENT_THRESHOLD	SZ_1M
+
+struct btrfs_trim_range {
+	u64 start;
+	u64 bytes;
+	struct list_head list;
+};
+
+static int link_free_space(struct btrfs_free_space_ctl *ctl,
+			   struct btrfs_free_space *info);
+static void unlink_free_space(struct btrfs_free_space_ctl *ctl,
+			      struct btrfs_free_space *info, bool update_stat);
+static int search_bitmap(struct btrfs_free_space_ctl *ctl,
+			 struct btrfs_free_space *bitmap_info, u64 *offset,
+			 u64 *bytes, bool for_alloc);
+static void free_bitmap(struct btrfs_free_space_ctl *ctl,
+			struct btrfs_free_space *bitmap_info);
+static void bitmap_clear_bits(struct btrfs_free_space_ctl *ctl,
+			      struct btrfs_free_space *info, u64 offset,
+			      u64 bytes, bool update_stats);
+
+static void __btrfs_remove_free_space_cache(struct btrfs_free_space_ctl *ctl)
+{
+	struct btrfs_free_space *info;
+	struct rb_node *node;
+
+	while ((node = rb_last(&ctl->free_space_offset)) != NULL) {
+		info = rb_entry(node, struct btrfs_free_space, offset_index);
+		if (!info->bitmap) {
+			unlink_free_space(ctl, info, true);
+			kmem_cache_free(btrfs_free_space_cachep, info);
+		} else {
+			free_bitmap(ctl, info);
+		}
+
+		cond_resched_lock(&ctl->tree_lock);
+	}
+}
+
+static struct inode *__lookup_free_space_inode(struct btrfs_root *root,
+					       struct btrfs_path *path,
+					       u64 offset)
+{
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	struct btrfs_key key;
+	struct btrfs_key location;
+	struct btrfs_disk_key disk_key;
+	struct btrfs_free_space_header *header;
+	struct extent_buffer *leaf;
+	struct inode *inode = NULL;
+	unsigned nofs_flag;
+	int ret;
+
+	key.objectid = BTRFS_FREE_SPACE_OBJECTID;
+	key.offset = offset;
+	key.type = 0;
+
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		return ERR_PTR(ret);
+	if (ret > 0) {
+		btrfs_release_path(path);
+		return ERR_PTR(-ENOENT);
+	}
+
+	leaf = path->nodes[0];
+	header = btrfs_item_ptr(leaf, path->slots[0],
+				struct btrfs_free_space_header);
+	btrfs_free_space_key(leaf, header, &disk_key);
+	btrfs_disk_key_to_cpu(&location, &disk_key);
+	btrfs_release_path(path);
+
+	/*
+	 * We are often under a trans handle at this point, so we need to make
+	 * sure NOFS is set to keep us from deadlocking.
+	 */
+	nofs_flag = memalloc_nofs_save();
+	inode = btrfs_iget_path(fs_info->sb, location.objectid, root, path);
+	btrfs_release_path(path);
+	memalloc_nofs_restore(nofs_flag);
+	if (IS_ERR(inode))
+		return inode;
+
+	mapping_set_gfp_mask(inode->i_mapping,
+			mapping_gfp_constraint(inode->i_mapping,
+			~(__GFP_FS | __GFP_HIGHMEM)));
+
+	return inode;
+}
+
+struct inode *lookup_free_space_inode(struct btrfs_block_group *block_group,
+		struct btrfs_path *path)
+{
+	struct btrfs_fs_info *fs_info = block_group->fs_info;
+	struct inode *inode = NULL;
+	u32 flags = BTRFS_INODE_NODATASUM | BTRFS_INODE_NODATACOW;
+
+	spin_lock(&block_group->lock);
+	if (block_group->inode)
+		inode = igrab(block_group->inode);
+	spin_unlock(&block_group->lock);
+	if (inode)
+		return inode;
+
+	inode = __lookup_free_space_inode(fs_info->tree_root, path,
+					  block_group->start);
+	if (IS_ERR(inode))
+		return inode;
+
+	spin_lock(&block_group->lock);
+	if (!((BTRFS_I(inode)->flags & flags) == flags)) {
+		btrfs_info(fs_info, "Old style space inode found, converting.");
+		BTRFS_I(inode)->flags |= BTRFS_INODE_NODATASUM |
+			BTRFS_INODE_NODATACOW;
+		block_group->disk_cache_state = BTRFS_DC_CLEAR;
+	}
+
+	if (!test_and_set_bit(BLOCK_GROUP_FLAG_IREF, &block_group->runtime_flags))
+		block_group->inode = igrab(inode);
+	spin_unlock(&block_group->lock);
+
+	return inode;
+}
+
+static int __create_free_space_inode(struct btrfs_root *root,
+				     struct btrfs_trans_handle *trans,
+				     struct btrfs_path *path,
+				     u64 ino, u64 offset)
+{
+	struct btrfs_key key;
+	struct btrfs_disk_key disk_key;
+	struct btrfs_free_space_header *header;
+	struct btrfs_inode_item *inode_item;
+	struct extent_buffer *leaf;
+	/* We inline CRCs for the free disk space cache */
+	const u64 flags = BTRFS_INODE_NOCOMPRESS | BTRFS_INODE_PREALLOC |
+			  BTRFS_INODE_NODATASUM | BTRFS_INODE_NODATACOW;
+	int ret;
+
+	ret = btrfs_insert_empty_inode(trans, root, path, ino);
+	if (ret)
+		return ret;
+
+	leaf = path->nodes[0];
+	inode_item = btrfs_item_ptr(leaf, path->slots[0],
+				    struct btrfs_inode_item);
+	btrfs_item_key(leaf, &disk_key, path->slots[0]);
+	memzero_extent_buffer(leaf, (unsigned long)inode_item,
+			     sizeof(*inode_item));
+	btrfs_set_inode_generation(leaf, inode_item, trans->transid);
+	btrfs_set_inode_size(leaf, inode_item, 0);
+	btrfs_set_inode_nbytes(leaf, inode_item, 0);
+	btrfs_set_inode_uid(leaf, inode_item, 0);
+	btrfs_set_inode_gid(leaf, inode_item, 0);
+	btrfs_set_inode_mode(leaf, inode_item, S_IFREG | 0600);
+	btrfs_set_inode_flags(leaf, inode_item, flags);
+	btrfs_set_inode_nlink(leaf, inode_item, 1);
+	btrfs_set_inode_transid(leaf, inode_item, trans->transid);
+	btrfs_set_inode_block_group(leaf, inode_item, offset);
+	btrfs_mark_buffer_dirty(leaf);
+	btrfs_release_path(path);
+
+	key.objectid = BTRFS_FREE_SPACE_OBJECTID;
+	key.offset = offset;
+	key.type = 0;
+	ret = btrfs_insert_empty_item(trans, root, path, &key,
+				      sizeof(struct btrfs_free_space_header));
+	if (ret < 0) {
+		btrfs_release_path(path);
+		return ret;
+	}
+
+	leaf = path->nodes[0];
+	header = btrfs_item_ptr(leaf, path->slots[0],
+				struct btrfs_free_space_header);
+	memzero_extent_buffer(leaf, (unsigned long)header, sizeof(*header));
+	btrfs_set_free_space_key(leaf, header, &disk_key);
+	btrfs_mark_buffer_dirty(leaf);
+	btrfs_release_path(path);
+
+	return 0;
+}
+
+int create_free_space_inode(struct btrfs_trans_handle *trans,
+			    struct btrfs_block_group *block_group,
+			    struct btrfs_path *path)
+{
+	int ret;
+	u64 ino;
+
+	ret = btrfs_get_free_objectid(trans->fs_info->tree_root, &ino);
+	if (ret < 0)
+		return ret;
+
+	return __create_free_space_inode(trans->fs_info->tree_root, trans, path,
+					 ino, block_group->start);
+}
+
+/*
+ * inode is an optional sink: if it is NULL, btrfs_remove_free_space_inode
+ * handles lookup, otherwise it takes ownership and iputs the inode.
+ * Don't reuse an inode pointer after passing it into this function.
+ */
+int btrfs_remove_free_space_inode(struct btrfs_trans_handle *trans,
+				  struct inode *inode,
+				  struct btrfs_block_group *block_group)
+{
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	int ret = 0;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	if (!inode)
+		inode = lookup_free_space_inode(block_group, path);
+	if (IS_ERR(inode)) {
+		if (PTR_ERR(inode) != -ENOENT)
+			ret = PTR_ERR(inode);
+		goto out;
+	}
+	ret = btrfs_orphan_add(trans, BTRFS_I(inode));
+	if (ret) {
+		btrfs_add_delayed_iput(inode);
+		goto out;
+	}
+	clear_nlink(inode);
+	/* One for the block groups ref */
+	spin_lock(&block_group->lock);
+	if (test_and_clear_bit(BLOCK_GROUP_FLAG_IREF, &block_group->runtime_flags)) {
+		block_group->inode = NULL;
+		spin_unlock(&block_group->lock);
+		iput(inode);
+	} else {
+		spin_unlock(&block_group->lock);
+	}
+	/* One for the lookup ref */
+	btrfs_add_delayed_iput(inode);
+
+	key.objectid = BTRFS_FREE_SPACE_OBJECTID;
+	key.type = 0;
+	key.offset = block_group->start;
+	ret = btrfs_search_slot(trans, trans->fs_info->tree_root, &key, path,
+				-1, 1);
+	if (ret) {
+		if (ret > 0)
+			ret = 0;
+		goto out;
+	}
+	ret = btrfs_del_item(trans, trans->fs_info->tree_root, path);
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+int btrfs_check_trunc_cache_free_space(struct btrfs_fs_info *fs_info,
+				       struct btrfs_block_rsv *rsv)
+{
+	u64 needed_bytes;
+	int ret;
+
+	/* 1 for slack space, 1 for updating the inode */
+	needed_bytes = btrfs_calc_insert_metadata_size(fs_info, 1) +
+		btrfs_calc_metadata_size(fs_info, 1);
+
+	spin_lock(&rsv->lock);
+	if (rsv->reserved < needed_bytes)
+		ret = -ENOSPC;
+	else
+		ret = 0;
+	spin_unlock(&rsv->lock);
+	return ret;
+}
+
+int btrfs_truncate_free_space_cache(struct btrfs_trans_handle *trans,
+				    struct btrfs_block_group *block_group,
+				    struct inode *vfs_inode)
+{
+	struct btrfs_truncate_control control = {
+		.inode = BTRFS_I(vfs_inode),
+		.new_size = 0,
+		.ino = btrfs_ino(BTRFS_I(vfs_inode)),
+		.min_type = BTRFS_EXTENT_DATA_KEY,
+		.clear_extent_range = true,
+	};
+	struct btrfs_inode *inode = BTRFS_I(vfs_inode);
+	struct btrfs_root *root = inode->root;
+	struct extent_state *cached_state = NULL;
+	int ret = 0;
+	bool locked = false;
+
+	if (block_group) {
+		struct btrfs_path *path = btrfs_alloc_path();
+
+		if (!path) {
+			ret = -ENOMEM;
+			goto fail;
+		}
+		locked = true;
+		mutex_lock(&trans->transaction->cache_write_mutex);
+		if (!list_empty(&block_group->io_list)) {
+			list_del_init(&block_group->io_list);
+
+			btrfs_wait_cache_io(trans, block_group, path);
+			btrfs_put_block_group(block_group);
+		}
+
+		/*
+		 * now that we've truncated the cache away, its no longer
+		 * setup or written
+		 */
+		spin_lock(&block_group->lock);
+		block_group->disk_cache_state = BTRFS_DC_CLEAR;
+		spin_unlock(&block_group->lock);
+		btrfs_free_path(path);
+	}
+
+	btrfs_i_size_write(inode, 0);
+	truncate_pagecache(vfs_inode, 0);
+
+	lock_extent(&inode->io_tree, 0, (u64)-1, &cached_state);
+	btrfs_drop_extent_map_range(inode, 0, (u64)-1, false);
+
+	/*
+	 * We skip the throttling logic for free space cache inodes, so we don't
+	 * need to check for -EAGAIN.
+	 */
+	ret = btrfs_truncate_inode_items(trans, root, &control);
+
+	inode_sub_bytes(&inode->vfs_inode, control.sub_bytes);
+	btrfs_inode_safe_disk_i_size_write(inode, control.last_size);
+
+	unlock_extent(&inode->io_tree, 0, (u64)-1, &cached_state);
+	if (ret)
+		goto fail;
+
+	ret = btrfs_update_inode(trans, root, inode);
+
+fail:
+	if (locked)
+		mutex_unlock(&trans->transaction->cache_write_mutex);
+	if (ret)
+		btrfs_abort_transaction(trans, ret);
+
+	return ret;
+}
+
+static void readahead_cache(struct inode *inode)
+{
+	struct file_ra_state ra;
+	unsigned long last_index;
+
+	file_ra_state_init(&ra, inode->i_mapping);
+	last_index = (i_size_read(inode) - 1) >> PAGE_SHIFT;
+
+	page_cache_sync_readahead(inode->i_mapping, &ra, NULL, 0, last_index);
+}
+
+static int io_ctl_init(struct btrfs_io_ctl *io_ctl, struct inode *inode,
+		       int write)
+{
+	int num_pages;
+
+	num_pages = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
+
+	/* Make sure we can fit our crcs and generation into the first page */
+	if (write && (num_pages * sizeof(u32) + sizeof(u64)) > PAGE_SIZE)
+		return -ENOSPC;
+
+	memset(io_ctl, 0, sizeof(struct btrfs_io_ctl));
+
+	io_ctl->pages = kcalloc(num_pages, sizeof(struct page *), GFP_NOFS);
+	if (!io_ctl->pages)
+		return -ENOMEM;
+
+	io_ctl->num_pages = num_pages;
+	io_ctl->fs_info = btrfs_sb(inode->i_sb);
+	io_ctl->inode = inode;
+
+	return 0;
+}
+ALLOW_ERROR_INJECTION(io_ctl_init, ERRNO);
+
+static void io_ctl_free(struct btrfs_io_ctl *io_ctl)
+{
+	kfree(io_ctl->pages);
+	io_ctl->pages = NULL;
+}
+
+static void io_ctl_unmap_page(struct btrfs_io_ctl *io_ctl)
+{
+	if (io_ctl->cur) {
+		io_ctl->cur = NULL;
+		io_ctl->orig = NULL;
+	}
+}
+
+static void io_ctl_map_page(struct btrfs_io_ctl *io_ctl, int clear)
+{
+	ASSERT(io_ctl->index < io_ctl->num_pages);
+	io_ctl->page = io_ctl->pages[io_ctl->index++];
+	io_ctl->cur = page_address(io_ctl->page);
+	io_ctl->orig = io_ctl->cur;
+	io_ctl->size = PAGE_SIZE;
+	if (clear)
+		clear_page(io_ctl->cur);
+}
+
+static void io_ctl_drop_pages(struct btrfs_io_ctl *io_ctl)
+{
+	int i;
+
+	io_ctl_unmap_page(io_ctl);
+
+	for (i = 0; i < io_ctl->num_pages; i++) {
+		if (io_ctl->pages[i]) {
+			btrfs_page_clear_checked(io_ctl->fs_info,
+					io_ctl->pages[i],
+					page_offset(io_ctl->pages[i]),
+					PAGE_SIZE);
+			unlock_page(io_ctl->pages[i]);
+			put_page(io_ctl->pages[i]);
+		}
+	}
+}
+
+static int io_ctl_prepare_pages(struct btrfs_io_ctl *io_ctl, bool uptodate)
+{
+	struct page *page;
+	struct inode *inode = io_ctl->inode;
+	gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
+	int i;
+
+	for (i = 0; i < io_ctl->num_pages; i++) {
+		int ret;
+
+		page = find_or_create_page(inode->i_mapping, i, mask);
+		if (!page) {
+			io_ctl_drop_pages(io_ctl);
+			return -ENOMEM;
+		}
+
+		ret = set_page_extent_mapped(page);
+		if (ret < 0) {
+			unlock_page(page);
+			put_page(page);
+			io_ctl_drop_pages(io_ctl);
+			return ret;
+		}
+
+		io_ctl->pages[i] = page;
+		if (uptodate && !PageUptodate(page)) {
+			btrfs_read_folio(NULL, page_folio(page));
+			lock_page(page);
+			if (page->mapping != inode->i_mapping) {
+				btrfs_err(BTRFS_I(inode)->root->fs_info,
+					  "free space cache page truncated");
+				io_ctl_drop_pages(io_ctl);
+				return -EIO;
+			}
+			if (!PageUptodate(page)) {
+				btrfs_err(BTRFS_I(inode)->root->fs_info,
+					   "error reading free space cache");
+				io_ctl_drop_pages(io_ctl);
+				return -EIO;
+			}
+		}
+	}
+
+	for (i = 0; i < io_ctl->num_pages; i++)
+		clear_page_dirty_for_io(io_ctl->pages[i]);
+
+	return 0;
+}
+
+static void io_ctl_set_generation(struct btrfs_io_ctl *io_ctl, u64 generation)
+{
+	io_ctl_map_page(io_ctl, 1);
+
+	/*
+	 * Skip the csum areas.  If we don't check crcs then we just have a
+	 * 64bit chunk at the front of the first page.
+	 */
+	io_ctl->cur += (sizeof(u32) * io_ctl->num_pages);
+	io_ctl->size -= sizeof(u64) + (sizeof(u32) * io_ctl->num_pages);
+
+	put_unaligned_le64(generation, io_ctl->cur);
+	io_ctl->cur += sizeof(u64);
+}
+
+static int io_ctl_check_generation(struct btrfs_io_ctl *io_ctl, u64 generation)
+{
+	u64 cache_gen;
+
+	/*
+	 * Skip the crc area.  If we don't check crcs then we just have a 64bit
+	 * chunk at the front of the first page.
+	 */
+	io_ctl->cur += sizeof(u32) * io_ctl->num_pages;
+	io_ctl->size -= sizeof(u64) + (sizeof(u32) * io_ctl->num_pages);
+
+	cache_gen = get_unaligned_le64(io_ctl->cur);
+	if (cache_gen != generation) {
+		btrfs_err_rl(io_ctl->fs_info,
+			"space cache generation (%llu) does not match inode (%llu)",
+				cache_gen, generation);
+		io_ctl_unmap_page(io_ctl);
+		return -EIO;
+	}
+	io_ctl->cur += sizeof(u64);
+	return 0;
+}
+
+static void io_ctl_set_crc(struct btrfs_io_ctl *io_ctl, int index)
+{
+	u32 *tmp;
+	u32 crc = ~(u32)0;
+	unsigned offset = 0;
+
+	if (index == 0)
+		offset = sizeof(u32) * io_ctl->num_pages;
+
+	crc = btrfs_crc32c(crc, io_ctl->orig + offset, PAGE_SIZE - offset);
+	btrfs_crc32c_final(crc, (u8 *)&crc);
+	io_ctl_unmap_page(io_ctl);
+	tmp = page_address(io_ctl->pages[0]);
+	tmp += index;
+	*tmp = crc;
+}
+
+static int io_ctl_check_crc(struct btrfs_io_ctl *io_ctl, int index)
+{
+	u32 *tmp, val;
+	u32 crc = ~(u32)0;
+	unsigned offset = 0;
+
+	if (index == 0)
+		offset = sizeof(u32) * io_ctl->num_pages;
+
+	tmp = page_address(io_ctl->pages[0]);
+	tmp += index;
+	val = *tmp;
+
+	io_ctl_map_page(io_ctl, 0);
+	crc = btrfs_crc32c(crc, io_ctl->orig + offset, PAGE_SIZE - offset);
+	btrfs_crc32c_final(crc, (u8 *)&crc);
+	if (val != crc) {
+		btrfs_err_rl(io_ctl->fs_info,
+			"csum mismatch on free space cache");
+		io_ctl_unmap_page(io_ctl);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int io_ctl_add_entry(struct btrfs_io_ctl *io_ctl, u64 offset, u64 bytes,
+			    void *bitmap)
+{
+	struct btrfs_free_space_entry *entry;
+
+	if (!io_ctl->cur)
+		return -ENOSPC;
+
+	entry = io_ctl->cur;
+	put_unaligned_le64(offset, &entry->offset);
+	put_unaligned_le64(bytes, &entry->bytes);
+	entry->type = (bitmap) ? BTRFS_FREE_SPACE_BITMAP :
+		BTRFS_FREE_SPACE_EXTENT;
+	io_ctl->cur += sizeof(struct btrfs_free_space_entry);
+	io_ctl->size -= sizeof(struct btrfs_free_space_entry);
+
+	if (io_ctl->size >= sizeof(struct btrfs_free_space_entry))
+		return 0;
+
+	io_ctl_set_crc(io_ctl, io_ctl->index - 1);
+
+	/* No more pages to map */
+	if (io_ctl->index >= io_ctl->num_pages)
+		return 0;
+
+	/* map the next page */
+	io_ctl_map_page(io_ctl, 1);
+	return 0;
+}
+
+static int io_ctl_add_bitmap(struct btrfs_io_ctl *io_ctl, void *bitmap)
+{
+	if (!io_ctl->cur)
+		return -ENOSPC;
+
+	/*
+	 * If we aren't at the start of the current page, unmap this one and
+	 * map the next one if there is any left.
+	 */
+	if (io_ctl->cur != io_ctl->orig) {
+		io_ctl_set_crc(io_ctl, io_ctl->index - 1);
+		if (io_ctl->index >= io_ctl->num_pages)
+			return -ENOSPC;
+		io_ctl_map_page(io_ctl, 0);
+	}
+
+	copy_page(io_ctl->cur, bitmap);
+	io_ctl_set_crc(io_ctl, io_ctl->index - 1);
+	if (io_ctl->index < io_ctl->num_pages)
+		io_ctl_map_page(io_ctl, 0);
+	return 0;
+}
+
+static void io_ctl_zero_remaining_pages(struct btrfs_io_ctl *io_ctl)
+{
+	/*
+	 * If we're not on the boundary we know we've modified the page and we
+	 * need to crc the page.
+	 */
+	if (io_ctl->cur != io_ctl->orig)
+		io_ctl_set_crc(io_ctl, io_ctl->index - 1);
+	else
+		io_ctl_unmap_page(io_ctl);
+
+	while (io_ctl->index < io_ctl->num_pages) {
+		io_ctl_map_page(io_ctl, 1);
+		io_ctl_set_crc(io_ctl, io_ctl->index - 1);
+	}
+}
+
+static int io_ctl_read_entry(struct btrfs_io_ctl *io_ctl,
+			    struct btrfs_free_space *entry, u8 *type)
+{
+	struct btrfs_free_space_entry *e;
+	int ret;
+
+	if (!io_ctl->cur) {
+		ret = io_ctl_check_crc(io_ctl, io_ctl->index);
+		if (ret)
+			return ret;
+	}
+
+	e = io_ctl->cur;
+	entry->offset = get_unaligned_le64(&e->offset);
+	entry->bytes = get_unaligned_le64(&e->bytes);
+	*type = e->type;
+	io_ctl->cur += sizeof(struct btrfs_free_space_entry);
+	io_ctl->size -= sizeof(struct btrfs_free_space_entry);
+
+	if (io_ctl->size >= sizeof(struct btrfs_free_space_entry))
+		return 0;
+
+	io_ctl_unmap_page(io_ctl);
+
+	return 0;
+}
+
+static int io_ctl_read_bitmap(struct btrfs_io_ctl *io_ctl,
+			      struct btrfs_free_space *entry)
+{
+	int ret;
+
+	ret = io_ctl_check_crc(io_ctl, io_ctl->index);
+	if (ret)
+		return ret;
+
+	copy_page(entry->bitmap, io_ctl->cur);
+	io_ctl_unmap_page(io_ctl);
+
+	return 0;
+}
+
+static void recalculate_thresholds(struct btrfs_free_space_ctl *ctl)
+{
+	struct btrfs_block_group *block_group = ctl->block_group;
+	u64 max_bytes;
+	u64 bitmap_bytes;
+	u64 extent_bytes;
+	u64 size = block_group->length;
+	u64 bytes_per_bg = BITS_PER_BITMAP * ctl->unit;
+	u64 max_bitmaps = div64_u64(size + bytes_per_bg - 1, bytes_per_bg);
+
+	max_bitmaps = max_t(u64, max_bitmaps, 1);
+
+	if (ctl->total_bitmaps > max_bitmaps)
+		btrfs_err(block_group->fs_info,
+"invalid free space control: bg start=%llu len=%llu total_bitmaps=%u unit=%u max_bitmaps=%llu bytes_per_bg=%llu",
+			  block_group->start, block_group->length,
+			  ctl->total_bitmaps, ctl->unit, max_bitmaps,
+			  bytes_per_bg);
+	ASSERT(ctl->total_bitmaps <= max_bitmaps);
+
+	/*
+	 * We are trying to keep the total amount of memory used per 1GiB of
+	 * space to be MAX_CACHE_BYTES_PER_GIG.  However, with a reclamation
+	 * mechanism of pulling extents >= FORCE_EXTENT_THRESHOLD out of
+	 * bitmaps, we may end up using more memory than this.
+	 */
+	if (size < SZ_1G)
+		max_bytes = MAX_CACHE_BYTES_PER_GIG;
+	else
+		max_bytes = MAX_CACHE_BYTES_PER_GIG * div_u64(size, SZ_1G);
+
+	bitmap_bytes = ctl->total_bitmaps * ctl->unit;
+
+	/*
+	 * we want the extent entry threshold to always be at most 1/2 the max
+	 * bytes we can have, or whatever is less than that.
+	 */
+	extent_bytes = max_bytes - bitmap_bytes;
+	extent_bytes = min_t(u64, extent_bytes, max_bytes >> 1);
+
+	ctl->extents_thresh =
+		div_u64(extent_bytes, sizeof(struct btrfs_free_space));
+}
+
+static int __load_free_space_cache(struct btrfs_root *root, struct inode *inode,
+				   struct btrfs_free_space_ctl *ctl,
+				   struct btrfs_path *path, u64 offset)
+{
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	struct btrfs_free_space_header *header;
+	struct extent_buffer *leaf;
+	struct btrfs_io_ctl io_ctl;
+	struct btrfs_key key;
+	struct btrfs_free_space *e, *n;
+	LIST_HEAD(bitmaps);
+	u64 num_entries;
+	u64 num_bitmaps;
+	u64 generation;
+	u8 type;
+	int ret = 0;
+
+	/* Nothing in the space cache, goodbye */
+	if (!i_size_read(inode))
+		return 0;
+
+	key.objectid = BTRFS_FREE_SPACE_OBJECTID;
+	key.offset = offset;
+	key.type = 0;
+
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		return 0;
+	else if (ret > 0) {
+		btrfs_release_path(path);
+		return 0;
+	}
+
+	ret = -1;
+
+	leaf = path->nodes[0];
+	header = btrfs_item_ptr(leaf, path->slots[0],
+				struct btrfs_free_space_header);
+	num_entries = btrfs_free_space_entries(leaf, header);
+	num_bitmaps = btrfs_free_space_bitmaps(leaf, header);
+	generation = btrfs_free_space_generation(leaf, header);
+	btrfs_release_path(path);
+
+	if (!BTRFS_I(inode)->generation) {
+		btrfs_info(fs_info,
+			   "the free space cache file (%llu) is invalid, skip it",
+			   offset);
+		return 0;
+	}
+
+	if (BTRFS_I(inode)->generation != generation) {
+		btrfs_err(fs_info,
+			  "free space inode generation (%llu) did not match free space cache generation (%llu)",
+			  BTRFS_I(inode)->generation, generation);
+		return 0;
+	}
+
+	if (!num_entries)
+		return 0;
+
+	ret = io_ctl_init(&io_ctl, inode, 0);
+	if (ret)
+		return ret;
+
+	readahead_cache(inode);
+
+	ret = io_ctl_prepare_pages(&io_ctl, true);
+	if (ret)
+		goto out;
+
+	ret = io_ctl_check_crc(&io_ctl, 0);
+	if (ret)
+		goto free_cache;
+
+	ret = io_ctl_check_generation(&io_ctl, generation);
+	if (ret)
+		goto free_cache;
+
+	while (num_entries) {
+		e = kmem_cache_zalloc(btrfs_free_space_cachep,
+				      GFP_NOFS);
+		if (!e) {
+			ret = -ENOMEM;
+			goto free_cache;
+		}
+
+		ret = io_ctl_read_entry(&io_ctl, e, &type);
+		if (ret) {
+			kmem_cache_free(btrfs_free_space_cachep, e);
+			goto free_cache;
+		}
+
+		if (!e->bytes) {
+			ret = -1;
+			kmem_cache_free(btrfs_free_space_cachep, e);
+			goto free_cache;
+		}
+
+		if (type == BTRFS_FREE_SPACE_EXTENT) {
+			spin_lock(&ctl->tree_lock);
+			ret = link_free_space(ctl, e);
+			spin_unlock(&ctl->tree_lock);
+			if (ret) {
+				btrfs_err(fs_info,
+					"Duplicate entries in free space cache, dumping");
+				kmem_cache_free(btrfs_free_space_cachep, e);
+				goto free_cache;
+			}
+		} else {
+			ASSERT(num_bitmaps);
+			num_bitmaps--;
+			e->bitmap = kmem_cache_zalloc(
+					btrfs_free_space_bitmap_cachep, GFP_NOFS);
+			if (!e->bitmap) {
+				ret = -ENOMEM;
+				kmem_cache_free(
+					btrfs_free_space_cachep, e);
+				goto free_cache;
+			}
+			spin_lock(&ctl->tree_lock);
+			ret = link_free_space(ctl, e);
+			if (ret) {
+				spin_unlock(&ctl->tree_lock);
+				btrfs_err(fs_info,
+					"Duplicate entries in free space cache, dumping");
+				kmem_cache_free(btrfs_free_space_cachep, e);
+				goto free_cache;
+			}
+			ctl->total_bitmaps++;
+			recalculate_thresholds(ctl);
+			spin_unlock(&ctl->tree_lock);
+			list_add_tail(&e->list, &bitmaps);
+		}
+
+		num_entries--;
+	}
+
+	io_ctl_unmap_page(&io_ctl);
+
+	/*
+	 * We add the bitmaps at the end of the entries in order that
+	 * the bitmap entries are added to the cache.
+	 */
+	list_for_each_entry_safe(e, n, &bitmaps, list) {
+		list_del_init(&e->list);
+		ret = io_ctl_read_bitmap(&io_ctl, e);
+		if (ret)
+			goto free_cache;
+	}
+
+	io_ctl_drop_pages(&io_ctl);
+	ret = 1;
+out:
+	io_ctl_free(&io_ctl);
+	return ret;
+free_cache:
+	io_ctl_drop_pages(&io_ctl);
+
+	spin_lock(&ctl->tree_lock);
+	__btrfs_remove_free_space_cache(ctl);
+	spin_unlock(&ctl->tree_lock);
+	goto out;
+}
+
+static int copy_free_space_cache(struct btrfs_block_group *block_group,
+				 struct btrfs_free_space_ctl *ctl)
+{
+	struct btrfs_free_space *info;
+	struct rb_node *n;
+	int ret = 0;
+
+	while (!ret && (n = rb_first(&ctl->free_space_offset)) != NULL) {
+		info = rb_entry(n, struct btrfs_free_space, offset_index);
+		if (!info->bitmap) {
+			unlink_free_space(ctl, info, true);
+			ret = btrfs_add_free_space(block_group, info->offset,
+						   info->bytes);
+			kmem_cache_free(btrfs_free_space_cachep, info);
+		} else {
+			u64 offset = info->offset;
+			u64 bytes = ctl->unit;
+
+			while (search_bitmap(ctl, info, &offset, &bytes,
+					     false) == 0) {
+				ret = btrfs_add_free_space(block_group, offset,
+							   bytes);
+				if (ret)
+					break;
+				bitmap_clear_bits(ctl, info, offset, bytes, true);
+				offset = info->offset;
+				bytes = ctl->unit;
+			}
+			free_bitmap(ctl, info);
+		}
+		cond_resched();
+	}
+	return ret;
+}
+
+static struct lock_class_key btrfs_free_space_inode_key;
+
+int load_free_space_cache(struct btrfs_block_group *block_group)
+{
+	struct btrfs_fs_info *fs_info = block_group->fs_info;
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_free_space_ctl tmp_ctl = {};
+	struct inode *inode;
+	struct btrfs_path *path;
+	int ret = 0;
+	bool matched;
+	u64 used = block_group->used;
+
+	/*
+	 * Because we could potentially discard our loaded free space, we want
+	 * to load everything into a temporary structure first, and then if it's
+	 * valid copy it all into the actual free space ctl.
+	 */
+	btrfs_init_free_space_ctl(block_group, &tmp_ctl);
+
+	/*
+	 * If this block group has been marked to be cleared for one reason or
+	 * another then we can't trust the on disk cache, so just return.
+	 */
+	spin_lock(&block_group->lock);
+	if (block_group->disk_cache_state != BTRFS_DC_WRITTEN) {
+		spin_unlock(&block_group->lock);
+		return 0;
+	}
+	spin_unlock(&block_group->lock);
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return 0;
+	path->search_commit_root = 1;
+	path->skip_locking = 1;
+
+	/*
+	 * We must pass a path with search_commit_root set to btrfs_iget in
+	 * order to avoid a deadlock when allocating extents for the tree root.
+	 *
+	 * When we are COWing an extent buffer from the tree root, when looking
+	 * for a free extent, at extent-tree.c:find_free_extent(), we can find
+	 * block group without its free space cache loaded. When we find one
+	 * we must load its space cache which requires reading its free space
+	 * cache's inode item from the root tree. If this inode item is located
+	 * in the same leaf that we started COWing before, then we end up in
+	 * deadlock on the extent buffer (trying to read lock it when we
+	 * previously write locked it).
+	 *
+	 * It's safe to read the inode item using the commit root because
+	 * block groups, once loaded, stay in memory forever (until they are
+	 * removed) as well as their space caches once loaded. New block groups
+	 * once created get their ->cached field set to BTRFS_CACHE_FINISHED so
+	 * we will never try to read their inode item while the fs is mounted.
+	 */
+	inode = lookup_free_space_inode(block_group, path);
+	if (IS_ERR(inode)) {
+		btrfs_free_path(path);
+		return 0;
+	}
+
+	/* We may have converted the inode and made the cache invalid. */
+	spin_lock(&block_group->lock);
+	if (block_group->disk_cache_state != BTRFS_DC_WRITTEN) {
+		spin_unlock(&block_group->lock);
+		btrfs_free_path(path);
+		goto out;
+	}
+	spin_unlock(&block_group->lock);
+
+	/*
+	 * Reinitialize the class of struct inode's mapping->invalidate_lock for
+	 * free space inodes to prevent false positives related to locks for normal
+	 * inodes.
+	 */
+	lockdep_set_class(&(&inode->i_data)->invalidate_lock,
+			  &btrfs_free_space_inode_key);
+
+	ret = __load_free_space_cache(fs_info->tree_root, inode, &tmp_ctl,
+				      path, block_group->start);
+	btrfs_free_path(path);
+	if (ret <= 0)
+		goto out;
+
+	matched = (tmp_ctl.free_space == (block_group->length - used -
+					  block_group->bytes_super));
+
+	if (matched) {
+		ret = copy_free_space_cache(block_group, &tmp_ctl);
+		/*
+		 * ret == 1 means we successfully loaded the free space cache,
+		 * so we need to re-set it here.
+		 */
+		if (ret == 0)
+			ret = 1;
+	} else {
+		/*
+		 * We need to call the _locked variant so we don't try to update
+		 * the discard counters.
+		 */
+		spin_lock(&tmp_ctl.tree_lock);
+		__btrfs_remove_free_space_cache(&tmp_ctl);
+		spin_unlock(&tmp_ctl.tree_lock);
+		btrfs_warn(fs_info,
+			   "block group %llu has wrong amount of free space",
+			   block_group->start);
+		ret = -1;
+	}
+out:
+	if (ret < 0) {
+		/* This cache is bogus, make sure it gets cleared */
+		spin_lock(&block_group->lock);
+		block_group->disk_cache_state = BTRFS_DC_CLEAR;
+		spin_unlock(&block_group->lock);
+		ret = 0;
+
+		btrfs_warn(fs_info,
+			   "failed to load free space cache for block group %llu, rebuilding it now",
+			   block_group->start);
+	}
+
+	spin_lock(&ctl->tree_lock);
+	btrfs_discard_update_discardable(block_group);
+	spin_unlock(&ctl->tree_lock);
+	iput(inode);
+	return ret;
+}
+
+static noinline_for_stack
+int write_cache_extent_entries(struct btrfs_io_ctl *io_ctl,
+			      struct btrfs_free_space_ctl *ctl,
+			      struct btrfs_block_group *block_group,
+			      int *entries, int *bitmaps,
+			      struct list_head *bitmap_list)
+{
+	int ret;
+	struct btrfs_free_cluster *cluster = NULL;
+	struct btrfs_free_cluster *cluster_locked = NULL;
+	struct rb_node *node = rb_first(&ctl->free_space_offset);
+	struct btrfs_trim_range *trim_entry;
+
+	/* Get the cluster for this block_group if it exists */
+	if (block_group && !list_empty(&block_group->cluster_list)) {
+		cluster = list_entry(block_group->cluster_list.next,
+				     struct btrfs_free_cluster,
+				     block_group_list);
+	}
+
+	if (!node && cluster) {
+		cluster_locked = cluster;
+		spin_lock(&cluster_locked->lock);
+		node = rb_first(&cluster->root);
+		cluster = NULL;
+	}
+
+	/* Write out the extent entries */
+	while (node) {
+		struct btrfs_free_space *e;
+
+		e = rb_entry(node, struct btrfs_free_space, offset_index);
+		*entries += 1;
+
+		ret = io_ctl_add_entry(io_ctl, e->offset, e->bytes,
+				       e->bitmap);
+		if (ret)
+			goto fail;
+
+		if (e->bitmap) {
+			list_add_tail(&e->list, bitmap_list);
+			*bitmaps += 1;
+		}
+		node = rb_next(node);
+		if (!node && cluster) {
+			node = rb_first(&cluster->root);
+			cluster_locked = cluster;
+			spin_lock(&cluster_locked->lock);
+			cluster = NULL;
+		}
+	}
+	if (cluster_locked) {
+		spin_unlock(&cluster_locked->lock);
+		cluster_locked = NULL;
+	}
+
+	/*
+	 * Make sure we don't miss any range that was removed from our rbtree
+	 * because trimming is running. Otherwise after a umount+mount (or crash
+	 * after committing the transaction) we would leak free space and get
+	 * an inconsistent free space cache report from fsck.
+	 */
+	list_for_each_entry(trim_entry, &ctl->trimming_ranges, list) {
+		ret = io_ctl_add_entry(io_ctl, trim_entry->start,
+				       trim_entry->bytes, NULL);
+		if (ret)
+			goto fail;
+		*entries += 1;
+	}
+
+	return 0;
+fail:
+	if (cluster_locked)
+		spin_unlock(&cluster_locked->lock);
+	return -ENOSPC;
+}
+
+static noinline_for_stack int
+update_cache_item(struct btrfs_trans_handle *trans,
+		  struct btrfs_root *root,
+		  struct inode *inode,
+		  struct btrfs_path *path, u64 offset,
+		  int entries, int bitmaps)
+{
+	struct btrfs_key key;
+	struct btrfs_free_space_header *header;
+	struct extent_buffer *leaf;
+	int ret;
+
+	key.objectid = BTRFS_FREE_SPACE_OBJECTID;
+	key.offset = offset;
+	key.type = 0;
+
+	ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
+	if (ret < 0) {
+		clear_extent_bit(&BTRFS_I(inode)->io_tree, 0, inode->i_size - 1,
+				 EXTENT_DELALLOC, NULL);
+		goto fail;
+	}
+	leaf = path->nodes[0];
+	if (ret > 0) {
+		struct btrfs_key found_key;
+		ASSERT(path->slots[0]);
+		path->slots[0]--;
+		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+		if (found_key.objectid != BTRFS_FREE_SPACE_OBJECTID ||
+		    found_key.offset != offset) {
+			clear_extent_bit(&BTRFS_I(inode)->io_tree, 0,
+					 inode->i_size - 1, EXTENT_DELALLOC,
+					 NULL);
+			btrfs_release_path(path);
+			goto fail;
+		}
+	}
+
+	BTRFS_I(inode)->generation = trans->transid;
+	header = btrfs_item_ptr(leaf, path->slots[0],
+				struct btrfs_free_space_header);
+	btrfs_set_free_space_entries(leaf, header, entries);
+	btrfs_set_free_space_bitmaps(leaf, header, bitmaps);
+	btrfs_set_free_space_generation(leaf, header, trans->transid);
+	btrfs_mark_buffer_dirty(leaf);
+	btrfs_release_path(path);
+
+	return 0;
+
+fail:
+	return -1;
+}
+
+static noinline_for_stack int write_pinned_extent_entries(
+			    struct btrfs_trans_handle *trans,
+			    struct btrfs_block_group *block_group,
+			    struct btrfs_io_ctl *io_ctl,
+			    int *entries)
+{
+	u64 start, extent_start, extent_end, len;
+	struct extent_io_tree *unpin = NULL;
+	int ret;
+
+	if (!block_group)
+		return 0;
+
+	/*
+	 * We want to add any pinned extents to our free space cache
+	 * so we don't leak the space
+	 *
+	 * We shouldn't have switched the pinned extents yet so this is the
+	 * right one
+	 */
+	unpin = &trans->transaction->pinned_extents;
+
+	start = block_group->start;
+
+	while (start < block_group->start + block_group->length) {
+		ret = find_first_extent_bit(unpin, start,
+					    &extent_start, &extent_end,
+					    EXTENT_DIRTY, NULL);
+		if (ret)
+			return 0;
+
+		/* This pinned extent is out of our range */
+		if (extent_start >= block_group->start + block_group->length)
+			return 0;
+
+		extent_start = max(extent_start, start);
+		extent_end = min(block_group->start + block_group->length,
+				 extent_end + 1);
+		len = extent_end - extent_start;
+
+		*entries += 1;
+		ret = io_ctl_add_entry(io_ctl, extent_start, len, NULL);
+		if (ret)
+			return -ENOSPC;
+
+		start = extent_end;
+	}
+
+	return 0;
+}
+
+static noinline_for_stack int
+write_bitmap_entries(struct btrfs_io_ctl *io_ctl, struct list_head *bitmap_list)
+{
+	struct btrfs_free_space *entry, *next;
+	int ret;
+
+	/* Write out the bitmaps */
+	list_for_each_entry_safe(entry, next, bitmap_list, list) {
+		ret = io_ctl_add_bitmap(io_ctl, entry->bitmap);
+		if (ret)
+			return -ENOSPC;
+		list_del_init(&entry->list);
+	}
+
+	return 0;
+}
+
+static int flush_dirty_cache(struct inode *inode)
+{
+	int ret;
+
+	ret = btrfs_wait_ordered_range(inode, 0, (u64)-1);
+	if (ret)
+		clear_extent_bit(&BTRFS_I(inode)->io_tree, 0, inode->i_size - 1,
+				 EXTENT_DELALLOC, NULL);
+
+	return ret;
+}
+
+static void noinline_for_stack
+cleanup_bitmap_list(struct list_head *bitmap_list)
+{
+	struct btrfs_free_space *entry, *next;
+
+	list_for_each_entry_safe(entry, next, bitmap_list, list)
+		list_del_init(&entry->list);
+}
+
+static void noinline_for_stack
+cleanup_write_cache_enospc(struct inode *inode,
+			   struct btrfs_io_ctl *io_ctl,
+			   struct extent_state **cached_state)
+{
+	io_ctl_drop_pages(io_ctl);
+	unlock_extent(&BTRFS_I(inode)->io_tree, 0, i_size_read(inode) - 1,
+		      cached_state);
+}
+
+static int __btrfs_wait_cache_io(struct btrfs_root *root,
+				 struct btrfs_trans_handle *trans,
+				 struct btrfs_block_group *block_group,
+				 struct btrfs_io_ctl *io_ctl,
+				 struct btrfs_path *path, u64 offset)
+{
+	int ret;
+	struct inode *inode = io_ctl->inode;
+
+	if (!inode)
+		return 0;
+
+	/* Flush the dirty pages in the cache file. */
+	ret = flush_dirty_cache(inode);
+	if (ret)
+		goto out;
+
+	/* Update the cache item to tell everyone this cache file is valid. */
+	ret = update_cache_item(trans, root, inode, path, offset,
+				io_ctl->entries, io_ctl->bitmaps);
+out:
+	if (ret) {
+		invalidate_inode_pages2(inode->i_mapping);
+		BTRFS_I(inode)->generation = 0;
+		if (block_group)
+			btrfs_debug(root->fs_info,
+	  "failed to write free space cache for block group %llu error %d",
+				  block_group->start, ret);
+	}
+	btrfs_update_inode(trans, root, BTRFS_I(inode));
+
+	if (block_group) {
+		/* the dirty list is protected by the dirty_bgs_lock */
+		spin_lock(&trans->transaction->dirty_bgs_lock);
+
+		/* the disk_cache_state is protected by the block group lock */
+		spin_lock(&block_group->lock);
+
+		/*
+		 * only mark this as written if we didn't get put back on
+		 * the dirty list while waiting for IO.   Otherwise our
+		 * cache state won't be right, and we won't get written again
+		 */
+		if (!ret && list_empty(&block_group->dirty_list))
+			block_group->disk_cache_state = BTRFS_DC_WRITTEN;
+		else if (ret)
+			block_group->disk_cache_state = BTRFS_DC_ERROR;
+
+		spin_unlock(&block_group->lock);
+		spin_unlock(&trans->transaction->dirty_bgs_lock);
+		io_ctl->inode = NULL;
+		iput(inode);
+	}
+
+	return ret;
+
+}
+
+int btrfs_wait_cache_io(struct btrfs_trans_handle *trans,
+			struct btrfs_block_group *block_group,
+			struct btrfs_path *path)
+{
+	return __btrfs_wait_cache_io(block_group->fs_info->tree_root, trans,
+				     block_group, &block_group->io_ctl,
+				     path, block_group->start);
+}
+
+/**
+ * Write out cached info to an inode
+ *
+ * @root:        root the inode belongs to
+ * @inode:       freespace inode we are writing out
+ * @ctl:         free space cache we are going to write out
+ * @block_group: block_group for this cache if it belongs to a block_group
+ * @io_ctl:      holds context for the io
+ * @trans:       the trans handle
+ *
+ * This function writes out a free space cache struct to disk for quick recovery
+ * on mount.  This will return 0 if it was successful in writing the cache out,
+ * or an errno if it was not.
+ */
+static int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
+				   struct btrfs_free_space_ctl *ctl,
+				   struct btrfs_block_group *block_group,
+				   struct btrfs_io_ctl *io_ctl,
+				   struct btrfs_trans_handle *trans)
+{
+	struct extent_state *cached_state = NULL;
+	LIST_HEAD(bitmap_list);
+	int entries = 0;
+	int bitmaps = 0;
+	int ret;
+	int must_iput = 0;
+
+	if (!i_size_read(inode))
+		return -EIO;
+
+	WARN_ON(io_ctl->pages);
+	ret = io_ctl_init(io_ctl, inode, 1);
+	if (ret)
+		return ret;
+
+	if (block_group && (block_group->flags & BTRFS_BLOCK_GROUP_DATA)) {
+		down_write(&block_group->data_rwsem);
+		spin_lock(&block_group->lock);
+		if (block_group->delalloc_bytes) {
+			block_group->disk_cache_state = BTRFS_DC_WRITTEN;
+			spin_unlock(&block_group->lock);
+			up_write(&block_group->data_rwsem);
+			BTRFS_I(inode)->generation = 0;
+			ret = 0;
+			must_iput = 1;
+			goto out;
+		}
+		spin_unlock(&block_group->lock);
+	}
+
+	/* Lock all pages first so we can lock the extent safely. */
+	ret = io_ctl_prepare_pages(io_ctl, false);
+	if (ret)
+		goto out_unlock;
+
+	lock_extent(&BTRFS_I(inode)->io_tree, 0, i_size_read(inode) - 1,
+		    &cached_state);
+
+	io_ctl_set_generation(io_ctl, trans->transid);
+
+	mutex_lock(&ctl->cache_writeout_mutex);
+	/* Write out the extent entries in the free space cache */
+	spin_lock(&ctl->tree_lock);
+	ret = write_cache_extent_entries(io_ctl, ctl,
+					 block_group, &entries, &bitmaps,
+					 &bitmap_list);
+	if (ret)
+		goto out_nospc_locked;
+
+	/*
+	 * Some spaces that are freed in the current transaction are pinned,
+	 * they will be added into free space cache after the transaction is
+	 * committed, we shouldn't lose them.
+	 *
+	 * If this changes while we are working we'll get added back to
+	 * the dirty list and redo it.  No locking needed
+	 */
+	ret = write_pinned_extent_entries(trans, block_group, io_ctl, &entries);
+	if (ret)
+		goto out_nospc_locked;
+
+	/*
+	 * At last, we write out all the bitmaps and keep cache_writeout_mutex
+	 * locked while doing it because a concurrent trim can be manipulating
+	 * or freeing the bitmap.
+	 */
+	ret = write_bitmap_entries(io_ctl, &bitmap_list);
+	spin_unlock(&ctl->tree_lock);
+	mutex_unlock(&ctl->cache_writeout_mutex);
+	if (ret)
+		goto out_nospc;
+
+	/* Zero out the rest of the pages just to make sure */
+	io_ctl_zero_remaining_pages(io_ctl);
+
+	/* Everything is written out, now we dirty the pages in the file. */
+	ret = btrfs_dirty_pages(BTRFS_I(inode), io_ctl->pages,
+				io_ctl->num_pages, 0, i_size_read(inode),
+				&cached_state, false);
+	if (ret)
+		goto out_nospc;
+
+	if (block_group && (block_group->flags & BTRFS_BLOCK_GROUP_DATA))
+		up_write(&block_group->data_rwsem);
+	/*
+	 * Release the pages and unlock the extent, we will flush
+	 * them out later
+	 */
+	io_ctl_drop_pages(io_ctl);
+	io_ctl_free(io_ctl);
+
+	unlock_extent(&BTRFS_I(inode)->io_tree, 0, i_size_read(inode) - 1,
+		      &cached_state);
+
+	/*
+	 * at this point the pages are under IO and we're happy,
+	 * The caller is responsible for waiting on them and updating
+	 * the cache and the inode
+	 */
+	io_ctl->entries = entries;
+	io_ctl->bitmaps = bitmaps;
+
+	ret = btrfs_fdatawrite_range(inode, 0, (u64)-1);
+	if (ret)
+		goto out;
+
+	return 0;
+
+out_nospc_locked:
+	cleanup_bitmap_list(&bitmap_list);
+	spin_unlock(&ctl->tree_lock);
+	mutex_unlock(&ctl->cache_writeout_mutex);
+
+out_nospc:
+	cleanup_write_cache_enospc(inode, io_ctl, &cached_state);
+
+out_unlock:
+	if (block_group && (block_group->flags & BTRFS_BLOCK_GROUP_DATA))
+		up_write(&block_group->data_rwsem);
+
+out:
+	io_ctl->inode = NULL;
+	io_ctl_free(io_ctl);
+	if (ret) {
+		invalidate_inode_pages2(inode->i_mapping);
+		BTRFS_I(inode)->generation = 0;
+	}
+	btrfs_update_inode(trans, root, BTRFS_I(inode));
+	if (must_iput)
+		iput(inode);
+	return ret;
+}
+
+int btrfs_write_out_cache(struct btrfs_trans_handle *trans,
+			  struct btrfs_block_group *block_group,
+			  struct btrfs_path *path)
+{
+	struct btrfs_fs_info *fs_info = trans->fs_info;
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct inode *inode;
+	int ret = 0;
+
+	spin_lock(&block_group->lock);
+	if (block_group->disk_cache_state < BTRFS_DC_SETUP) {
+		spin_unlock(&block_group->lock);
+		return 0;
+	}
+	spin_unlock(&block_group->lock);
+
+	inode = lookup_free_space_inode(block_group, path);
+	if (IS_ERR(inode))
+		return 0;
+
+	ret = __btrfs_write_out_cache(fs_info->tree_root, inode, ctl,
+				block_group, &block_group->io_ctl, trans);
+	if (ret) {
+		btrfs_debug(fs_info,
+	  "failed to write free space cache for block group %llu error %d",
+			  block_group->start, ret);
+		spin_lock(&block_group->lock);
+		block_group->disk_cache_state = BTRFS_DC_ERROR;
+		spin_unlock(&block_group->lock);
+
+		block_group->io_ctl.inode = NULL;
+		iput(inode);
+	}
+
+	/*
+	 * if ret == 0 the caller is expected to call btrfs_wait_cache_io
+	 * to wait for IO and put the inode
+	 */
+
+	return ret;
+}
+
+static inline unsigned long offset_to_bit(u64 bitmap_start, u32 unit,
+					  u64 offset)
+{
+	ASSERT(offset >= bitmap_start);
+	offset -= bitmap_start;
+	return (unsigned long)(div_u64(offset, unit));
+}
+
+static inline unsigned long bytes_to_bits(u64 bytes, u32 unit)
+{
+	return (unsigned long)(div_u64(bytes, unit));
+}
+
+static inline u64 offset_to_bitmap(struct btrfs_free_space_ctl *ctl,
+				   u64 offset)
+{
+	u64 bitmap_start;
+	u64 bytes_per_bitmap;
+
+	bytes_per_bitmap = BITS_PER_BITMAP * ctl->unit;
+	bitmap_start = offset - ctl->start;
+	bitmap_start = div64_u64(bitmap_start, bytes_per_bitmap);
+	bitmap_start *= bytes_per_bitmap;
+	bitmap_start += ctl->start;
+
+	return bitmap_start;
+}
+
+static int tree_insert_offset(struct rb_root *root, u64 offset,
+			      struct rb_node *node, int bitmap)
+{
+	struct rb_node **p = &root->rb_node;
+	struct rb_node *parent = NULL;
+	struct btrfs_free_space *info;
+
+	while (*p) {
+		parent = *p;
+		info = rb_entry(parent, struct btrfs_free_space, offset_index);
+
+		if (offset < info->offset) {
+			p = &(*p)->rb_left;
+		} else if (offset > info->offset) {
+			p = &(*p)->rb_right;
+		} else {
+			/*
+			 * we could have a bitmap entry and an extent entry
+			 * share the same offset.  If this is the case, we want
+			 * the extent entry to always be found first if we do a
+			 * linear search through the tree, since we want to have
+			 * the quickest allocation time, and allocating from an
+			 * extent is faster than allocating from a bitmap.  So
+			 * if we're inserting a bitmap and we find an entry at
+			 * this offset, we want to go right, or after this entry
+			 * logically.  If we are inserting an extent and we've
+			 * found a bitmap, we want to go left, or before
+			 * logically.
+			 */
+			if (bitmap) {
+				if (info->bitmap) {
+					WARN_ON_ONCE(1);
+					return -EEXIST;
+				}
+				p = &(*p)->rb_right;
+			} else {
+				if (!info->bitmap) {
+					WARN_ON_ONCE(1);
+					return -EEXIST;
+				}
+				p = &(*p)->rb_left;
+			}
+		}
+	}
+
+	rb_link_node(node, parent, p);
+	rb_insert_color(node, root);
+
+	return 0;
+}
+
+/*
+ * This is a little subtle.  We *only* have ->max_extent_size set if we actually
+ * searched through the bitmap and figured out the largest ->max_extent_size,
+ * otherwise it's 0.  In the case that it's 0 we don't want to tell the
+ * allocator the wrong thing, we want to use the actual real max_extent_size
+ * we've found already if it's larger, or we want to use ->bytes.
+ *
+ * This matters because find_free_space() will skip entries who's ->bytes is
+ * less than the required bytes.  So if we didn't search down this bitmap, we
+ * may pick some previous entry that has a smaller ->max_extent_size than we
+ * have.  For example, assume we have two entries, one that has
+ * ->max_extent_size set to 4K and ->bytes set to 1M.  A second entry hasn't set
+ * ->max_extent_size yet, has ->bytes set to 8K and it's contiguous.  We will
+ *  call into find_free_space(), and return with max_extent_size == 4K, because
+ *  that first bitmap entry had ->max_extent_size set, but the second one did
+ *  not.  If instead we returned 8K we'd come in searching for 8K, and find the
+ *  8K contiguous range.
+ *
+ *  Consider the other case, we have 2 8K chunks in that second entry and still
+ *  don't have ->max_extent_size set.  We'll return 16K, and the next time the
+ *  allocator comes in it'll fully search our second bitmap, and this time it'll
+ *  get an uptodate value of 8K as the maximum chunk size.  Then we'll get the
+ *  right allocation the next loop through.
+ */
+static inline u64 get_max_extent_size(const struct btrfs_free_space *entry)
+{
+	if (entry->bitmap && entry->max_extent_size)
+		return entry->max_extent_size;
+	return entry->bytes;
+}
+
+/*
+ * We want the largest entry to be leftmost, so this is inverted from what you'd
+ * normally expect.
+ */
+static bool entry_less(struct rb_node *node, const struct rb_node *parent)
+{
+	const struct btrfs_free_space *entry, *exist;
+
+	entry = rb_entry(node, struct btrfs_free_space, bytes_index);
+	exist = rb_entry(parent, struct btrfs_free_space, bytes_index);
+	return get_max_extent_size(exist) < get_max_extent_size(entry);
+}
+
+/*
+ * searches the tree for the given offset.
+ *
+ * fuzzy - If this is set, then we are trying to make an allocation, and we just
+ * want a section that has at least bytes size and comes at or after the given
+ * offset.
+ */
+static struct btrfs_free_space *
+tree_search_offset(struct btrfs_free_space_ctl *ctl,
+		   u64 offset, int bitmap_only, int fuzzy)
+{
+	struct rb_node *n = ctl->free_space_offset.rb_node;
+	struct btrfs_free_space *entry = NULL, *prev = NULL;
+
+	/* find entry that is closest to the 'offset' */
+	while (n) {
+		entry = rb_entry(n, struct btrfs_free_space, offset_index);
+		prev = entry;
+
+		if (offset < entry->offset)
+			n = n->rb_left;
+		else if (offset > entry->offset)
+			n = n->rb_right;
+		else
+			break;
+
+		entry = NULL;
+	}
+
+	if (bitmap_only) {
+		if (!entry)
+			return NULL;
+		if (entry->bitmap)
+			return entry;
+
+		/*
+		 * bitmap entry and extent entry may share same offset,
+		 * in that case, bitmap entry comes after extent entry.
+		 */
+		n = rb_next(n);
+		if (!n)
+			return NULL;
+		entry = rb_entry(n, struct btrfs_free_space, offset_index);
+		if (entry->offset != offset)
+			return NULL;
+
+		WARN_ON(!entry->bitmap);
+		return entry;
+	} else if (entry) {
+		if (entry->bitmap) {
+			/*
+			 * if previous extent entry covers the offset,
+			 * we should return it instead of the bitmap entry
+			 */
+			n = rb_prev(&entry->offset_index);
+			if (n) {
+				prev = rb_entry(n, struct btrfs_free_space,
+						offset_index);
+				if (!prev->bitmap &&
+				    prev->offset + prev->bytes > offset)
+					entry = prev;
+			}
+		}
+		return entry;
+	}
+
+	if (!prev)
+		return NULL;
+
+	/* find last entry before the 'offset' */
+	entry = prev;
+	if (entry->offset > offset) {
+		n = rb_prev(&entry->offset_index);
+		if (n) {
+			entry = rb_entry(n, struct btrfs_free_space,
+					offset_index);
+			ASSERT(entry->offset <= offset);
+		} else {
+			if (fuzzy)
+				return entry;
+			else
+				return NULL;
+		}
+	}
+
+	if (entry->bitmap) {
+		n = rb_prev(&entry->offset_index);
+		if (n) {
+			prev = rb_entry(n, struct btrfs_free_space,
+					offset_index);
+			if (!prev->bitmap &&
+			    prev->offset + prev->bytes > offset)
+				return prev;
+		}
+		if (entry->offset + BITS_PER_BITMAP * ctl->unit > offset)
+			return entry;
+	} else if (entry->offset + entry->bytes > offset)
+		return entry;
+
+	if (!fuzzy)
+		return NULL;
+
+	while (1) {
+		n = rb_next(&entry->offset_index);
+		if (!n)
+			return NULL;
+		entry = rb_entry(n, struct btrfs_free_space, offset_index);
+		if (entry->bitmap) {
+			if (entry->offset + BITS_PER_BITMAP *
+			    ctl->unit > offset)
+				break;
+		} else {
+			if (entry->offset + entry->bytes > offset)
+				break;
+		}
+	}
+	return entry;
+}
+
+static inline void unlink_free_space(struct btrfs_free_space_ctl *ctl,
+				     struct btrfs_free_space *info,
+				     bool update_stat)
+{
+	rb_erase(&info->offset_index, &ctl->free_space_offset);
+	rb_erase_cached(&info->bytes_index, &ctl->free_space_bytes);
+	ctl->free_extents--;
+
+	if (!info->bitmap && !btrfs_free_space_trimmed(info)) {
+		ctl->discardable_extents[BTRFS_STAT_CURR]--;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] -= info->bytes;
+	}
+
+	if (update_stat)
+		ctl->free_space -= info->bytes;
+}
+
+static int link_free_space(struct btrfs_free_space_ctl *ctl,
+			   struct btrfs_free_space *info)
+{
+	int ret = 0;
+
+	ASSERT(info->bytes || info->bitmap);
+	ret = tree_insert_offset(&ctl->free_space_offset, info->offset,
+				 &info->offset_index, (info->bitmap != NULL));
+	if (ret)
+		return ret;
+
+	rb_add_cached(&info->bytes_index, &ctl->free_space_bytes, entry_less);
+
+	if (!info->bitmap && !btrfs_free_space_trimmed(info)) {
+		ctl->discardable_extents[BTRFS_STAT_CURR]++;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] += info->bytes;
+	}
+
+	ctl->free_space += info->bytes;
+	ctl->free_extents++;
+	return ret;
+}
+
+static void relink_bitmap_entry(struct btrfs_free_space_ctl *ctl,
+				struct btrfs_free_space *info)
+{
+	ASSERT(info->bitmap);
+
+	/*
+	 * If our entry is empty it's because we're on a cluster and we don't
+	 * want to re-link it into our ctl bytes index.
+	 */
+	if (RB_EMPTY_NODE(&info->bytes_index))
+		return;
+
+	rb_erase_cached(&info->bytes_index, &ctl->free_space_bytes);
+	rb_add_cached(&info->bytes_index, &ctl->free_space_bytes, entry_less);
+}
+
+static inline void bitmap_clear_bits(struct btrfs_free_space_ctl *ctl,
+				     struct btrfs_free_space *info,
+				     u64 offset, u64 bytes, bool update_stat)
+{
+	unsigned long start, count, end;
+	int extent_delta = -1;
+
+	start = offset_to_bit(info->offset, ctl->unit, offset);
+	count = bytes_to_bits(bytes, ctl->unit);
+	end = start + count;
+	ASSERT(end <= BITS_PER_BITMAP);
+
+	bitmap_clear(info->bitmap, start, count);
+
+	info->bytes -= bytes;
+	if (info->max_extent_size > ctl->unit)
+		info->max_extent_size = 0;
+
+	relink_bitmap_entry(ctl, info);
+
+	if (start && test_bit(start - 1, info->bitmap))
+		extent_delta++;
+
+	if (end < BITS_PER_BITMAP && test_bit(end, info->bitmap))
+		extent_delta++;
+
+	info->bitmap_extents += extent_delta;
+	if (!btrfs_free_space_trimmed(info)) {
+		ctl->discardable_extents[BTRFS_STAT_CURR] += extent_delta;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] -= bytes;
+	}
+
+	if (update_stat)
+		ctl->free_space -= bytes;
+}
+
+static void bitmap_set_bits(struct btrfs_free_space_ctl *ctl,
+			    struct btrfs_free_space *info, u64 offset,
+			    u64 bytes)
+{
+	unsigned long start, count, end;
+	int extent_delta = 1;
+
+	start = offset_to_bit(info->offset, ctl->unit, offset);
+	count = bytes_to_bits(bytes, ctl->unit);
+	end = start + count;
+	ASSERT(end <= BITS_PER_BITMAP);
+
+	bitmap_set(info->bitmap, start, count);
+
+	/*
+	 * We set some bytes, we have no idea what the max extent size is
+	 * anymore.
+	 */
+	info->max_extent_size = 0;
+	info->bytes += bytes;
+	ctl->free_space += bytes;
+
+	relink_bitmap_entry(ctl, info);
+
+	if (start && test_bit(start - 1, info->bitmap))
+		extent_delta--;
+
+	if (end < BITS_PER_BITMAP && test_bit(end, info->bitmap))
+		extent_delta--;
+
+	info->bitmap_extents += extent_delta;
+	if (!btrfs_free_space_trimmed(info)) {
+		ctl->discardable_extents[BTRFS_STAT_CURR] += extent_delta;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] += bytes;
+	}
+}
+
+/*
+ * If we can not find suitable extent, we will use bytes to record
+ * the size of the max extent.
+ */
+static int search_bitmap(struct btrfs_free_space_ctl *ctl,
+			 struct btrfs_free_space *bitmap_info, u64 *offset,
+			 u64 *bytes, bool for_alloc)
+{
+	unsigned long found_bits = 0;
+	unsigned long max_bits = 0;
+	unsigned long bits, i;
+	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;
+		if (extent_bits >= bits) {
+			found_bits = extent_bits;
+			break;
+		} else if (extent_bits > max_bits) {
+			max_bits = extent_bits;
+		}
+		i = next_zero;
+	}
+
+	if (found_bits) {
+		*offset = (u64)(i * ctl->unit) + bitmap_info->offset;
+		*bytes = (u64)(found_bits) * ctl->unit;
+		return 0;
+	}
+
+	*bytes = (u64)(max_bits) * ctl->unit;
+	bitmap_info->max_extent_size = *bytes;
+	relink_bitmap_entry(ctl, bitmap_info);
+	return -1;
+}
+
+/* Cache the size of the max extent in bytes */
+static struct btrfs_free_space *
+find_free_space(struct btrfs_free_space_ctl *ctl, u64 *offset, u64 *bytes,
+		unsigned long align, u64 *max_extent_size, bool use_bytes_index)
+{
+	struct btrfs_free_space *entry;
+	struct rb_node *node;
+	u64 tmp;
+	u64 align_off;
+	int ret;
+
+	if (!ctl->free_space_offset.rb_node)
+		goto out;
+again:
+	if (use_bytes_index) {
+		node = rb_first_cached(&ctl->free_space_bytes);
+	} else {
+		entry = tree_search_offset(ctl, offset_to_bitmap(ctl, *offset),
+					   0, 1);
+		if (!entry)
+			goto out;
+		node = &entry->offset_index;
+	}
+
+	for (; node; node = rb_next(node)) {
+		if (use_bytes_index)
+			entry = rb_entry(node, struct btrfs_free_space,
+					 bytes_index);
+		else
+			entry = rb_entry(node, struct btrfs_free_space,
+					 offset_index);
+
+		/*
+		 * If we are using the bytes index then all subsequent entries
+		 * in this tree are going to be < bytes, so simply set the max
+		 * extent size and exit the loop.
+		 *
+		 * If we're using the offset index then we need to keep going
+		 * through the rest of the tree.
+		 */
+		if (entry->bytes < *bytes) {
+			*max_extent_size = max(get_max_extent_size(entry),
+					       *max_extent_size);
+			if (use_bytes_index)
+				break;
+			continue;
+		}
+
+		/* make sure the space returned is big enough
+		 * to match our requested alignment
+		 */
+		if (*bytes >= align) {
+			tmp = entry->offset - ctl->start + align - 1;
+			tmp = div64_u64(tmp, align);
+			tmp = tmp * align + ctl->start;
+			align_off = tmp - entry->offset;
+		} else {
+			align_off = 0;
+			tmp = entry->offset;
+		}
+
+		/*
+		 * We don't break here if we're using the bytes index because we
+		 * may have another entry that has the correct alignment that is
+		 * the right size, so we don't want to miss that possibility.
+		 * At worst this adds another loop through the logic, but if we
+		 * broke here we could prematurely ENOSPC.
+		 */
+		if (entry->bytes < *bytes + align_off) {
+			*max_extent_size = max(get_max_extent_size(entry),
+					       *max_extent_size);
+			continue;
+		}
+
+		if (entry->bitmap) {
+			struct rb_node *old_next = rb_next(node);
+			u64 size = *bytes;
+
+			ret = search_bitmap(ctl, entry, &tmp, &size, true);
+			if (!ret) {
+				*offset = tmp;
+				*bytes = size;
+				return entry;
+			} else {
+				*max_extent_size =
+					max(get_max_extent_size(entry),
+					    *max_extent_size);
+			}
+
+			/*
+			 * The bitmap may have gotten re-arranged in the space
+			 * index here because the max_extent_size may have been
+			 * updated.  Start from the beginning again if this
+			 * happened.
+			 */
+			if (use_bytes_index && old_next != rb_next(node))
+				goto again;
+			continue;
+		}
+
+		*offset = tmp;
+		*bytes = entry->bytes - align_off;
+		return entry;
+	}
+out:
+	return NULL;
+}
+
+static void add_new_bitmap(struct btrfs_free_space_ctl *ctl,
+			   struct btrfs_free_space *info, u64 offset)
+{
+	info->offset = offset_to_bitmap(ctl, offset);
+	info->bytes = 0;
+	info->bitmap_extents = 0;
+	INIT_LIST_HEAD(&info->list);
+	link_free_space(ctl, info);
+	ctl->total_bitmaps++;
+	recalculate_thresholds(ctl);
+}
+
+static void free_bitmap(struct btrfs_free_space_ctl *ctl,
+			struct btrfs_free_space *bitmap_info)
+{
+	/*
+	 * Normally when this is called, the bitmap is completely empty. However,
+	 * if we are blowing up the free space cache for one reason or another
+	 * via __btrfs_remove_free_space_cache(), then it may not be freed and
+	 * we may leave stats on the table.
+	 */
+	if (bitmap_info->bytes && !btrfs_free_space_trimmed(bitmap_info)) {
+		ctl->discardable_extents[BTRFS_STAT_CURR] -=
+			bitmap_info->bitmap_extents;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] -= bitmap_info->bytes;
+
+	}
+	unlink_free_space(ctl, bitmap_info, true);
+	kmem_cache_free(btrfs_free_space_bitmap_cachep, bitmap_info->bitmap);
+	kmem_cache_free(btrfs_free_space_cachep, bitmap_info);
+	ctl->total_bitmaps--;
+	recalculate_thresholds(ctl);
+}
+
+static noinline int remove_from_bitmap(struct btrfs_free_space_ctl *ctl,
+			      struct btrfs_free_space *bitmap_info,
+			      u64 *offset, u64 *bytes)
+{
+	u64 end;
+	u64 search_start, search_bytes;
+	int ret;
+
+again:
+	end = bitmap_info->offset + (u64)(BITS_PER_BITMAP * ctl->unit) - 1;
+
+	/*
+	 * We need to search for bits in this bitmap.  We could only cover some
+	 * of the extent in this bitmap thanks to how we add space, so we need
+	 * to search for as much as it as we can and clear that amount, and then
+	 * go searching for the next bit.
+	 */
+	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,
+			    false);
+	if (ret < 0 || search_start != *offset)
+		return -EINVAL;
+
+	/* We may have found more bits than what we need */
+	search_bytes = min(search_bytes, *bytes);
+
+	/* Cannot clear past the end of the bitmap */
+	search_bytes = min(search_bytes, end - search_start + 1);
+
+	bitmap_clear_bits(ctl, bitmap_info, search_start, search_bytes, true);
+	*offset += search_bytes;
+	*bytes -= search_bytes;
+
+	if (*bytes) {
+		struct rb_node *next = rb_next(&bitmap_info->offset_index);
+		if (!bitmap_info->bytes)
+			free_bitmap(ctl, bitmap_info);
+
+		/*
+		 * no entry after this bitmap, but we still have bytes to
+		 * remove, so something has gone wrong.
+		 */
+		if (!next)
+			return -EINVAL;
+
+		bitmap_info = rb_entry(next, struct btrfs_free_space,
+				       offset_index);
+
+		/*
+		 * if the next entry isn't a bitmap we need to return to let the
+		 * extent stuff do its work.
+		 */
+		if (!bitmap_info->bitmap)
+			return -EAGAIN;
+
+		/*
+		 * Ok the next item is a bitmap, but it may not actually hold
+		 * the information for the rest of this free space stuff, so
+		 * look for it, and if we don't find it return so we can try
+		 * everything over again.
+		 */
+		search_start = *offset;
+		search_bytes = ctl->unit;
+		ret = search_bitmap(ctl, bitmap_info, &search_start,
+				    &search_bytes, false);
+		if (ret < 0 || search_start != *offset)
+			return -EAGAIN;
+
+		goto again;
+	} else if (!bitmap_info->bytes)
+		free_bitmap(ctl, bitmap_info);
+
+	return 0;
+}
+
+static u64 add_bytes_to_bitmap(struct btrfs_free_space_ctl *ctl,
+			       struct btrfs_free_space *info, u64 offset,
+			       u64 bytes, enum btrfs_trim_state trim_state)
+{
+	u64 bytes_to_set = 0;
+	u64 end;
+
+	/*
+	 * This is a tradeoff to make bitmap trim state minimal.  We mark the
+	 * whole bitmap untrimmed if at any point we add untrimmed regions.
+	 */
+	if (trim_state == BTRFS_TRIM_STATE_UNTRIMMED) {
+		if (btrfs_free_space_trimmed(info)) {
+			ctl->discardable_extents[BTRFS_STAT_CURR] +=
+				info->bitmap_extents;
+			ctl->discardable_bytes[BTRFS_STAT_CURR] += info->bytes;
+		}
+		info->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+	}
+
+	end = info->offset + (u64)(BITS_PER_BITMAP * ctl->unit);
+
+	bytes_to_set = min(end - offset, bytes);
+
+	bitmap_set_bits(ctl, info, offset, bytes_to_set);
+
+	return bytes_to_set;
+
+}
+
+static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
+		      struct btrfs_free_space *info)
+{
+	struct btrfs_block_group *block_group = ctl->block_group;
+	struct btrfs_fs_info *fs_info = block_group->fs_info;
+	bool forced = false;
+
+#ifdef CONFIG_BTRFS_DEBUG
+	if (btrfs_should_fragment_free_space(block_group))
+		forced = true;
+#endif
+
+	/* This is a way to reclaim large regions from the bitmaps. */
+	if (!forced && info->bytes >= FORCE_EXTENT_THRESHOLD)
+		return false;
+
+	/*
+	 * 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 (!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
+		 * to reserve them to larger extents, however if we have plenty
+		 * of cache left then go ahead an dadd them, no sense in adding
+		 * the overhead of a bitmap if we don't have to.
+		 */
+		if (info->bytes <= fs_info->sectorsize * 8) {
+			if (ctl->free_extents * 3 <= ctl->extents_thresh)
+				return false;
+		} else {
+			return false;
+		}
+	}
+
+	/*
+	 * The original block groups from mkfs can be really small, like 8
+	 * megabytes, so don't bother with a bitmap for those entries.  However
+	 * some block groups can be smaller than what a bitmap would cover but
+	 * are still large enough that they could overflow the 32k memory limit,
+	 * so allow those block groups to still be allowed to have a bitmap
+	 * entry.
+	 */
+	if (((BITS_PER_BITMAP * ctl->unit) >> 1) > block_group->length)
+		return false;
+
+	return true;
+}
+
+static const struct btrfs_free_space_op free_space_op = {
+	.use_bitmap		= use_bitmap,
+};
+
+static int insert_into_bitmap(struct btrfs_free_space_ctl *ctl,
+			      struct btrfs_free_space *info)
+{
+	struct btrfs_free_space *bitmap_info;
+	struct btrfs_block_group *block_group = NULL;
+	int added = 0;
+	u64 bytes, offset, bytes_added;
+	enum btrfs_trim_state trim_state;
+	int ret;
+
+	bytes = info->bytes;
+	offset = info->offset;
+	trim_state = info->trim_state;
+
+	if (!ctl->op->use_bitmap(ctl, info))
+		return 0;
+
+	if (ctl->op == &free_space_op)
+		block_group = ctl->block_group;
+again:
+	/*
+	 * Since we link bitmaps right into the cluster we need to see if we
+	 * have a cluster here, and if so and it has our bitmap we need to add
+	 * the free space to that bitmap.
+	 */
+	if (block_group && !list_empty(&block_group->cluster_list)) {
+		struct btrfs_free_cluster *cluster;
+		struct rb_node *node;
+		struct btrfs_free_space *entry;
+
+		cluster = list_entry(block_group->cluster_list.next,
+				     struct btrfs_free_cluster,
+				     block_group_list);
+		spin_lock(&cluster->lock);
+		node = rb_first(&cluster->root);
+		if (!node) {
+			spin_unlock(&cluster->lock);
+			goto no_cluster_bitmap;
+		}
+
+		entry = rb_entry(node, struct btrfs_free_space, offset_index);
+		if (!entry->bitmap) {
+			spin_unlock(&cluster->lock);
+			goto no_cluster_bitmap;
+		}
+
+		if (entry->offset == offset_to_bitmap(ctl, offset)) {
+			bytes_added = add_bytes_to_bitmap(ctl, entry, offset,
+							  bytes, trim_state);
+			bytes -= bytes_added;
+			offset += bytes_added;
+		}
+		spin_unlock(&cluster->lock);
+		if (!bytes) {
+			ret = 1;
+			goto out;
+		}
+	}
+
+no_cluster_bitmap:
+	bitmap_info = tree_search_offset(ctl, offset_to_bitmap(ctl, offset),
+					 1, 0);
+	if (!bitmap_info) {
+		ASSERT(added == 0);
+		goto new_bitmap;
+	}
+
+	bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes,
+					  trim_state);
+	bytes -= bytes_added;
+	offset += bytes_added;
+	added = 0;
+
+	if (!bytes) {
+		ret = 1;
+		goto out;
+	} else
+		goto again;
+
+new_bitmap:
+	if (info && info->bitmap) {
+		add_new_bitmap(ctl, info, offset);
+		added = 1;
+		info = NULL;
+		goto again;
+	} else {
+		spin_unlock(&ctl->tree_lock);
+
+		/* no pre-allocated info, allocate a new one */
+		if (!info) {
+			info = kmem_cache_zalloc(btrfs_free_space_cachep,
+						 GFP_NOFS);
+			if (!info) {
+				spin_lock(&ctl->tree_lock);
+				ret = -ENOMEM;
+				goto out;
+			}
+		}
+
+		/* allocate the bitmap */
+		info->bitmap = kmem_cache_zalloc(btrfs_free_space_bitmap_cachep,
+						 GFP_NOFS);
+		info->trim_state = BTRFS_TRIM_STATE_TRIMMED;
+		spin_lock(&ctl->tree_lock);
+		if (!info->bitmap) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		goto again;
+	}
+
+out:
+	if (info) {
+		if (info->bitmap)
+			kmem_cache_free(btrfs_free_space_bitmap_cachep,
+					info->bitmap);
+		kmem_cache_free(btrfs_free_space_cachep, info);
+	}
+
+	return ret;
+}
+
+/*
+ * Free space merging rules:
+ *  1) Merge trimmed areas together
+ *  2) Let untrimmed areas coalesce with trimmed areas
+ *  3) Always pull neighboring regions from bitmaps
+ *
+ * The above rules are for when we merge free space based on btrfs_trim_state.
+ * Rules 2 and 3 are subtle because they are suboptimal, but are done for the
+ * same reason: to promote larger extent regions which makes life easier for
+ * find_free_extent().  Rule 2 enables coalescing based on the common path
+ * being returning free space from btrfs_finish_extent_commit().  So when free
+ * space is trimmed, it will prevent aggregating trimmed new region and
+ * untrimmed regions in the rb_tree.  Rule 3 is purely to obtain larger extents
+ * and provide find_free_extent() with the largest extents possible hoping for
+ * the reuse path.
+ */
+static bool try_merge_free_space(struct btrfs_free_space_ctl *ctl,
+			  struct btrfs_free_space *info, bool update_stat)
+{
+	struct btrfs_free_space *left_info = NULL;
+	struct btrfs_free_space *right_info;
+	bool merged = false;
+	u64 offset = info->offset;
+	u64 bytes = info->bytes;
+	const bool is_trimmed = btrfs_free_space_trimmed(info);
+
+	/*
+	 * first we want to see if there is free space adjacent to the range we
+	 * are adding, if there is remove that struct and add a new one to
+	 * cover the entire range
+	 */
+	right_info = tree_search_offset(ctl, offset + bytes, 0, 0);
+	if (right_info && rb_prev(&right_info->offset_index))
+		left_info = rb_entry(rb_prev(&right_info->offset_index),
+				     struct btrfs_free_space, offset_index);
+	else if (!right_info)
+		left_info = tree_search_offset(ctl, offset - 1, 0, 0);
+
+	/* See try_merge_free_space() comment. */
+	if (right_info && !right_info->bitmap &&
+	    (!is_trimmed || btrfs_free_space_trimmed(right_info))) {
+		unlink_free_space(ctl, right_info, update_stat);
+		info->bytes += right_info->bytes;
+		kmem_cache_free(btrfs_free_space_cachep, right_info);
+		merged = true;
+	}
+
+	/* See try_merge_free_space() comment. */
+	if (left_info && !left_info->bitmap &&
+	    left_info->offset + left_info->bytes == offset &&
+	    (!is_trimmed || btrfs_free_space_trimmed(left_info))) {
+		unlink_free_space(ctl, left_info, update_stat);
+		info->offset = left_info->offset;
+		info->bytes += left_info->bytes;
+		kmem_cache_free(btrfs_free_space_cachep, left_info);
+		merged = true;
+	}
+
+	return merged;
+}
+
+static bool steal_from_bitmap_to_end(struct btrfs_free_space_ctl *ctl,
+				     struct btrfs_free_space *info,
+				     bool update_stat)
+{
+	struct btrfs_free_space *bitmap;
+	unsigned long i;
+	unsigned long j;
+	const u64 end = info->offset + info->bytes;
+	const u64 bitmap_offset = offset_to_bitmap(ctl, end);
+	u64 bytes;
+
+	bitmap = tree_search_offset(ctl, bitmap_offset, 1, 0);
+	if (!bitmap)
+		return false;
+
+	i = offset_to_bit(bitmap->offset, ctl->unit, end);
+	j = find_next_zero_bit(bitmap->bitmap, BITS_PER_BITMAP, i);
+	if (j == i)
+		return false;
+	bytes = (j - i) * ctl->unit;
+	info->bytes += bytes;
+
+	/* See try_merge_free_space() comment. */
+	if (!btrfs_free_space_trimmed(bitmap))
+		info->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+
+	bitmap_clear_bits(ctl, bitmap, end, bytes, update_stat);
+
+	if (!bitmap->bytes)
+		free_bitmap(ctl, bitmap);
+
+	return true;
+}
+
+static bool steal_from_bitmap_to_front(struct btrfs_free_space_ctl *ctl,
+				       struct btrfs_free_space *info,
+				       bool update_stat)
+{
+	struct btrfs_free_space *bitmap;
+	u64 bitmap_offset;
+	unsigned long i;
+	unsigned long j;
+	unsigned long prev_j;
+	u64 bytes;
+
+	bitmap_offset = offset_to_bitmap(ctl, info->offset);
+	/* If we're on a boundary, try the previous logical bitmap. */
+	if (bitmap_offset == info->offset) {
+		if (info->offset == 0)
+			return false;
+		bitmap_offset = offset_to_bitmap(ctl, info->offset - 1);
+	}
+
+	bitmap = tree_search_offset(ctl, bitmap_offset, 1, 0);
+	if (!bitmap)
+		return false;
+
+	i = offset_to_bit(bitmap->offset, ctl->unit, info->offset) - 1;
+	j = 0;
+	prev_j = (unsigned long)-1;
+	for_each_clear_bit_from(j, bitmap->bitmap, BITS_PER_BITMAP) {
+		if (j > i)
+			break;
+		prev_j = j;
+	}
+	if (prev_j == i)
+		return false;
+
+	if (prev_j == (unsigned long)-1)
+		bytes = (i + 1) * ctl->unit;
+	else
+		bytes = (i - prev_j) * ctl->unit;
+
+	info->offset -= bytes;
+	info->bytes += bytes;
+
+	/* See try_merge_free_space() comment. */
+	if (!btrfs_free_space_trimmed(bitmap))
+		info->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+
+	bitmap_clear_bits(ctl, bitmap, info->offset, bytes, update_stat);
+
+	if (!bitmap->bytes)
+		free_bitmap(ctl, bitmap);
+
+	return true;
+}
+
+/*
+ * We prefer always to allocate from extent entries, both for clustered and
+ * non-clustered allocation requests. So when attempting to add a new extent
+ * entry, try to see if there's adjacent free space in bitmap entries, and if
+ * there is, migrate that space from the bitmaps to the extent.
+ * Like this we get better chances of satisfying space allocation requests
+ * because we attempt to satisfy them based on a single cache entry, and never
+ * on 2 or more entries - even if the entries represent a contiguous free space
+ * region (e.g. 1 extent entry + 1 bitmap entry starting where the extent entry
+ * ends).
+ */
+static void steal_from_bitmap(struct btrfs_free_space_ctl *ctl,
+			      struct btrfs_free_space *info,
+			      bool update_stat)
+{
+	/*
+	 * Only work with disconnected entries, as we can change their offset,
+	 * and must be extent entries.
+	 */
+	ASSERT(!info->bitmap);
+	ASSERT(RB_EMPTY_NODE(&info->offset_index));
+
+	if (ctl->total_bitmaps > 0) {
+		bool stole_end;
+		bool stole_front = false;
+
+		stole_end = steal_from_bitmap_to_end(ctl, info, update_stat);
+		if (ctl->total_bitmaps > 0)
+			stole_front = steal_from_bitmap_to_front(ctl, info,
+								 update_stat);
+
+		if (stole_end || stole_front)
+			try_merge_free_space(ctl, info, update_stat);
+	}
+}
+
+int __btrfs_add_free_space(struct btrfs_block_group *block_group,
+			   u64 offset, u64 bytes,
+			   enum btrfs_trim_state trim_state)
+{
+	struct btrfs_fs_info *fs_info = block_group->fs_info;
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_free_space *info;
+	int ret = 0;
+	u64 filter_bytes = bytes;
+
+	ASSERT(!btrfs_is_zoned(fs_info));
+
+	info = kmem_cache_zalloc(btrfs_free_space_cachep, GFP_NOFS);
+	if (!info)
+		return -ENOMEM;
+
+	info->offset = offset;
+	info->bytes = bytes;
+	info->trim_state = trim_state;
+	RB_CLEAR_NODE(&info->offset_index);
+	RB_CLEAR_NODE(&info->bytes_index);
+
+	spin_lock(&ctl->tree_lock);
+
+	if (try_merge_free_space(ctl, info, true))
+		goto link;
+
+	/*
+	 * There was no extent directly to the left or right of this new
+	 * extent then we know we're going to have to allocate a new extent, so
+	 * before we do that see if we need to drop this into a bitmap
+	 */
+	ret = insert_into_bitmap(ctl, info);
+	if (ret < 0) {
+		goto out;
+	} else if (ret) {
+		ret = 0;
+		goto out;
+	}
+link:
+	/*
+	 * Only steal free space from adjacent bitmaps if we're sure we're not
+	 * going to add the new free space to existing bitmap entries - because
+	 * that would mean unnecessary work that would be reverted. Therefore
+	 * attempt to steal space from bitmaps if we're adding an extent entry.
+	 */
+	steal_from_bitmap(ctl, info, true);
+
+	filter_bytes = max(filter_bytes, info->bytes);
+
+	ret = link_free_space(ctl, info);
+	if (ret)
+		kmem_cache_free(btrfs_free_space_cachep, info);
+out:
+	btrfs_discard_update_discardable(block_group);
+	spin_unlock(&ctl->tree_lock);
+
+	if (ret) {
+		btrfs_crit(fs_info, "unable to add free space :%d", ret);
+		ASSERT(ret != -EEXIST);
+	}
+
+	if (trim_state != BTRFS_TRIM_STATE_TRIMMED) {
+		btrfs_discard_check_filter(block_group, filter_bytes);
+		btrfs_discard_queue_work(&fs_info->discard_ctl, block_group);
+	}
+
+	return ret;
+}
+
+static int __btrfs_add_free_space_zoned(struct btrfs_block_group *block_group,
+					u64 bytenr, u64 size, bool used)
+{
+	struct btrfs_space_info *sinfo = block_group->space_info;
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	u64 offset = bytenr - block_group->start;
+	u64 to_free, to_unusable;
+	int bg_reclaim_threshold = 0;
+	bool initial = (size == block_group->length);
+	u64 reclaimable_unusable;
+
+	WARN_ON(!initial && offset + size > block_group->zone_capacity);
+
+	if (!initial)
+		bg_reclaim_threshold = READ_ONCE(sinfo->bg_reclaim_threshold);
+
+	spin_lock(&ctl->tree_lock);
+	if (!used)
+		to_free = size;
+	else if (initial)
+		to_free = block_group->zone_capacity;
+	else if (offset >= block_group->alloc_offset)
+		to_free = size;
+	else if (offset + size <= block_group->alloc_offset)
+		to_free = 0;
+	else
+		to_free = offset + size - block_group->alloc_offset;
+	to_unusable = size - to_free;
+
+	ctl->free_space += to_free;
+	/*
+	 * If the block group is read-only, we should account freed space into
+	 * bytes_readonly.
+	 */
+	if (!block_group->ro)
+		block_group->zone_unusable += to_unusable;
+	spin_unlock(&ctl->tree_lock);
+	if (!used) {
+		spin_lock(&block_group->lock);
+		block_group->alloc_offset -= size;
+		spin_unlock(&block_group->lock);
+	}
+
+	reclaimable_unusable = block_group->zone_unusable -
+			       (block_group->length - block_group->zone_capacity);
+	/* All the region is now unusable. Mark it as unused and reclaim */
+	if (block_group->zone_unusable == block_group->length) {
+		btrfs_mark_bg_unused(block_group);
+	} else if (bg_reclaim_threshold &&
+		   reclaimable_unusable >=
+		   div_factor_fine(block_group->zone_capacity,
+				   bg_reclaim_threshold)) {
+		btrfs_mark_bg_to_reclaim(block_group);
+	}
+
+	return 0;
+}
+
+int btrfs_add_free_space(struct btrfs_block_group *block_group,
+			 u64 bytenr, u64 size)
+{
+	enum btrfs_trim_state trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+
+	if (btrfs_is_zoned(block_group->fs_info))
+		return __btrfs_add_free_space_zoned(block_group, bytenr, size,
+						    true);
+
+	if (btrfs_test_opt(block_group->fs_info, DISCARD_SYNC))
+		trim_state = BTRFS_TRIM_STATE_TRIMMED;
+
+	return __btrfs_add_free_space(block_group, bytenr, size, trim_state);
+}
+
+int btrfs_add_free_space_unused(struct btrfs_block_group *block_group,
+				u64 bytenr, u64 size)
+{
+	if (btrfs_is_zoned(block_group->fs_info))
+		return __btrfs_add_free_space_zoned(block_group, bytenr, size,
+						    false);
+
+	return btrfs_add_free_space(block_group, bytenr, size);
+}
+
+/*
+ * This is a subtle distinction because when adding free space back in general,
+ * we want it to be added as untrimmed for async. But in the case where we add
+ * it on loading of a block group, we want to consider it trimmed.
+ */
+int btrfs_add_free_space_async_trimmed(struct btrfs_block_group *block_group,
+				       u64 bytenr, u64 size)
+{
+	enum btrfs_trim_state trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+
+	if (btrfs_is_zoned(block_group->fs_info))
+		return __btrfs_add_free_space_zoned(block_group, bytenr, size,
+						    true);
+
+	if (btrfs_test_opt(block_group->fs_info, DISCARD_SYNC) ||
+	    btrfs_test_opt(block_group->fs_info, DISCARD_ASYNC))
+		trim_state = BTRFS_TRIM_STATE_TRIMMED;
+
+	return __btrfs_add_free_space(block_group, bytenr, size, trim_state);
+}
+
+int btrfs_remove_free_space(struct btrfs_block_group *block_group,
+			    u64 offset, u64 bytes)
+{
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_free_space *info;
+	int ret;
+	bool re_search = false;
+
+	if (btrfs_is_zoned(block_group->fs_info)) {
+		/*
+		 * This can happen with conventional zones when replaying log.
+		 * Since the allocation info of tree-log nodes are not recorded
+		 * to the extent-tree, calculate_alloc_pointer() failed to
+		 * advance the allocation pointer after last allocated tree log
+		 * node blocks.
+		 *
+		 * This function is called from
+		 * btrfs_pin_extent_for_log_replay() when replaying the log.
+		 * Advance the pointer not to overwrite the tree-log nodes.
+		 */
+		if (block_group->start + block_group->alloc_offset <
+		    offset + bytes) {
+			block_group->alloc_offset =
+				offset + bytes - block_group->start;
+		}
+		return 0;
+	}
+
+	spin_lock(&ctl->tree_lock);
+
+again:
+	ret = 0;
+	if (!bytes)
+		goto out_lock;
+
+	info = tree_search_offset(ctl, offset, 0, 0);
+	if (!info) {
+		/*
+		 * oops didn't find an extent that matched the space we wanted
+		 * to remove, look for a bitmap instead
+		 */
+		info = tree_search_offset(ctl, offset_to_bitmap(ctl, offset),
+					  1, 0);
+		if (!info) {
+			/*
+			 * If we found a partial bit of our free space in a
+			 * bitmap but then couldn't find the other part this may
+			 * be a problem, so WARN about it.
+			 */
+			WARN_ON(re_search);
+			goto out_lock;
+		}
+	}
+
+	re_search = false;
+	if (!info->bitmap) {
+		unlink_free_space(ctl, info, true);
+		if (offset == info->offset) {
+			u64 to_free = min(bytes, info->bytes);
+
+			info->bytes -= to_free;
+			info->offset += to_free;
+			if (info->bytes) {
+				ret = link_free_space(ctl, info);
+				WARN_ON(ret);
+			} else {
+				kmem_cache_free(btrfs_free_space_cachep, info);
+			}
+
+			offset += to_free;
+			bytes -= to_free;
+			goto again;
+		} else {
+			u64 old_end = info->bytes + info->offset;
+
+			info->bytes = offset - info->offset;
+			ret = link_free_space(ctl, info);
+			WARN_ON(ret);
+			if (ret)
+				goto out_lock;
+
+			/* Not enough bytes in this entry to satisfy us */
+			if (old_end < offset + bytes) {
+				bytes -= old_end - offset;
+				offset = old_end;
+				goto again;
+			} else if (old_end == offset + bytes) {
+				/* all done */
+				goto out_lock;
+			}
+			spin_unlock(&ctl->tree_lock);
+
+			ret = __btrfs_add_free_space(block_group,
+						     offset + bytes,
+						     old_end - (offset + bytes),
+						     info->trim_state);
+			WARN_ON(ret);
+			goto out;
+		}
+	}
+
+	ret = remove_from_bitmap(ctl, info, &offset, &bytes);
+	if (ret == -EAGAIN) {
+		re_search = true;
+		goto again;
+	}
+out_lock:
+	btrfs_discard_update_discardable(block_group);
+	spin_unlock(&ctl->tree_lock);
+out:
+	return ret;
+}
+
+void btrfs_dump_free_space(struct btrfs_block_group *block_group,
+			   u64 bytes)
+{
+	struct btrfs_fs_info *fs_info = block_group->fs_info;
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_free_space *info;
+	struct rb_node *n;
+	int count = 0;
+
+	/*
+	 * Zoned btrfs does not use free space tree and cluster. Just print
+	 * out the free space after the allocation offset.
+	 */
+	if (btrfs_is_zoned(fs_info)) {
+		btrfs_info(fs_info, "free space %llu active %d",
+			   block_group->zone_capacity - block_group->alloc_offset,
+			   test_bit(BLOCK_GROUP_FLAG_ZONE_IS_ACTIVE,
+				    &block_group->runtime_flags));
+		return;
+	}
+
+	spin_lock(&ctl->tree_lock);
+	for (n = rb_first(&ctl->free_space_offset); n; n = rb_next(n)) {
+		info = rb_entry(n, struct btrfs_free_space, offset_index);
+		if (info->bytes >= bytes && !block_group->ro)
+			count++;
+		btrfs_crit(fs_info, "entry offset %llu, bytes %llu, bitmap %s",
+			   info->offset, info->bytes,
+		       (info->bitmap) ? "yes" : "no");
+	}
+	spin_unlock(&ctl->tree_lock);
+	btrfs_info(fs_info, "block group has cluster?: %s",
+	       list_empty(&block_group->cluster_list) ? "no" : "yes");
+	btrfs_info(fs_info,
+		   "%d blocks of free space at or bigger than bytes is", count);
+}
+
+void btrfs_init_free_space_ctl(struct btrfs_block_group *block_group,
+			       struct btrfs_free_space_ctl *ctl)
+{
+	struct btrfs_fs_info *fs_info = block_group->fs_info;
+
+	spin_lock_init(&ctl->tree_lock);
+	ctl->unit = fs_info->sectorsize;
+	ctl->start = block_group->start;
+	ctl->block_group = block_group;
+	ctl->op = &free_space_op;
+	ctl->free_space_bytes = RB_ROOT_CACHED;
+	INIT_LIST_HEAD(&ctl->trimming_ranges);
+	mutex_init(&ctl->cache_writeout_mutex);
+
+	/*
+	 * we only want to have 32k of ram per block group for keeping
+	 * track of free space, and if we pass 1/2 of that we want to
+	 * start converting things over to using bitmaps
+	 */
+	ctl->extents_thresh = (SZ_32K / 2) / sizeof(struct btrfs_free_space);
+}
+
+/*
+ * for a given cluster, put all of its extents back into the free
+ * space cache.  If the block group passed doesn't match the block group
+ * pointed to by the cluster, someone else raced in and freed the
+ * cluster already.  In that case, we just return without changing anything
+ */
+static void __btrfs_return_cluster_to_free_space(
+			     struct btrfs_block_group *block_group,
+			     struct btrfs_free_cluster *cluster)
+{
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_free_space *entry;
+	struct rb_node *node;
+
+	spin_lock(&cluster->lock);
+	if (cluster->block_group != block_group) {
+		spin_unlock(&cluster->lock);
+		return;
+	}
+
+	cluster->block_group = NULL;
+	cluster->window_start = 0;
+	list_del_init(&cluster->block_group_list);
+
+	node = rb_first(&cluster->root);
+	while (node) {
+		bool bitmap;
+
+		entry = rb_entry(node, struct btrfs_free_space, offset_index);
+		node = rb_next(&entry->offset_index);
+		rb_erase(&entry->offset_index, &cluster->root);
+		RB_CLEAR_NODE(&entry->offset_index);
+
+		bitmap = (entry->bitmap != NULL);
+		if (!bitmap) {
+			/* Merging treats extents as if they were new */
+			if (!btrfs_free_space_trimmed(entry)) {
+				ctl->discardable_extents[BTRFS_STAT_CURR]--;
+				ctl->discardable_bytes[BTRFS_STAT_CURR] -=
+					entry->bytes;
+			}
+
+			try_merge_free_space(ctl, entry, false);
+			steal_from_bitmap(ctl, entry, false);
+
+			/* As we insert directly, update these statistics */
+			if (!btrfs_free_space_trimmed(entry)) {
+				ctl->discardable_extents[BTRFS_STAT_CURR]++;
+				ctl->discardable_bytes[BTRFS_STAT_CURR] +=
+					entry->bytes;
+			}
+		}
+		tree_insert_offset(&ctl->free_space_offset,
+				   entry->offset, &entry->offset_index, bitmap);
+		rb_add_cached(&entry->bytes_index, &ctl->free_space_bytes,
+			      entry_less);
+	}
+	cluster->root = RB_ROOT;
+	spin_unlock(&cluster->lock);
+	btrfs_put_block_group(block_group);
+}
+
+void btrfs_remove_free_space_cache(struct btrfs_block_group *block_group)
+{
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_free_cluster *cluster;
+	struct list_head *head;
+
+	spin_lock(&ctl->tree_lock);
+	while ((head = block_group->cluster_list.next) !=
+	       &block_group->cluster_list) {
+		cluster = list_entry(head, struct btrfs_free_cluster,
+				     block_group_list);
+
+		WARN_ON(cluster->block_group != block_group);
+		__btrfs_return_cluster_to_free_space(block_group, cluster);
+
+		cond_resched_lock(&ctl->tree_lock);
+	}
+	__btrfs_remove_free_space_cache(ctl);
+	btrfs_discard_update_discardable(block_group);
+	spin_unlock(&ctl->tree_lock);
+
+}
+
+/**
+ * btrfs_is_free_space_trimmed - see if everything is trimmed
+ * @block_group: block_group of interest
+ *
+ * Walk @block_group's free space rb_tree to determine if everything is trimmed.
+ */
+bool btrfs_is_free_space_trimmed(struct btrfs_block_group *block_group)
+{
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_free_space *info;
+	struct rb_node *node;
+	bool ret = true;
+
+	spin_lock(&ctl->tree_lock);
+	node = rb_first(&ctl->free_space_offset);
+
+	while (node) {
+		info = rb_entry(node, struct btrfs_free_space, offset_index);
+
+		if (!btrfs_free_space_trimmed(info)) {
+			ret = false;
+			break;
+		}
+
+		node = rb_next(node);
+	}
+
+	spin_unlock(&ctl->tree_lock);
+	return ret;
+}
+
+u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
+			       u64 offset, u64 bytes, u64 empty_size,
+			       u64 *max_extent_size)
+{
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_discard_ctl *discard_ctl =
+					&block_group->fs_info->discard_ctl;
+	struct btrfs_free_space *entry = NULL;
+	u64 bytes_search = bytes + empty_size;
+	u64 ret = 0;
+	u64 align_gap = 0;
+	u64 align_gap_len = 0;
+	enum btrfs_trim_state align_gap_trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+	bool use_bytes_index = (offset == block_group->start);
+
+	ASSERT(!btrfs_is_zoned(block_group->fs_info));
+
+	spin_lock(&ctl->tree_lock);
+	entry = find_free_space(ctl, &offset, &bytes_search,
+				block_group->full_stripe_len, max_extent_size,
+				use_bytes_index);
+	if (!entry)
+		goto out;
+
+	ret = offset;
+	if (entry->bitmap) {
+		bitmap_clear_bits(ctl, entry, offset, bytes, true);
+
+		if (!btrfs_free_space_trimmed(entry))
+			atomic64_add(bytes, &discard_ctl->discard_bytes_saved);
+
+		if (!entry->bytes)
+			free_bitmap(ctl, entry);
+	} else {
+		unlink_free_space(ctl, entry, true);
+		align_gap_len = offset - entry->offset;
+		align_gap = entry->offset;
+		align_gap_trim_state = entry->trim_state;
+
+		if (!btrfs_free_space_trimmed(entry))
+			atomic64_add(bytes, &discard_ctl->discard_bytes_saved);
+
+		entry->offset = offset + bytes;
+		WARN_ON(entry->bytes < bytes + align_gap_len);
+
+		entry->bytes -= bytes + align_gap_len;
+		if (!entry->bytes)
+			kmem_cache_free(btrfs_free_space_cachep, entry);
+		else
+			link_free_space(ctl, entry);
+	}
+out:
+	btrfs_discard_update_discardable(block_group);
+	spin_unlock(&ctl->tree_lock);
+
+	if (align_gap_len)
+		__btrfs_add_free_space(block_group, align_gap, align_gap_len,
+				       align_gap_trim_state);
+	return ret;
+}
+
+/*
+ * given a cluster, put all of its extents back into the free space
+ * cache.  If a block group is passed, this function will only free
+ * a cluster that belongs to the passed block group.
+ *
+ * Otherwise, it'll get a reference on the block group pointed to by the
+ * cluster and remove the cluster from it.
+ */
+void btrfs_return_cluster_to_free_space(
+			       struct btrfs_block_group *block_group,
+			       struct btrfs_free_cluster *cluster)
+{
+	struct btrfs_free_space_ctl *ctl;
+
+	/* first, get a safe pointer to the block group */
+	spin_lock(&cluster->lock);
+	if (!block_group) {
+		block_group = cluster->block_group;
+		if (!block_group) {
+			spin_unlock(&cluster->lock);
+			return;
+		}
+	} else if (cluster->block_group != block_group) {
+		/* someone else has already freed it don't redo their work */
+		spin_unlock(&cluster->lock);
+		return;
+	}
+	btrfs_get_block_group(block_group);
+	spin_unlock(&cluster->lock);
+
+	ctl = block_group->free_space_ctl;
+
+	/* now return any extents the cluster had on it */
+	spin_lock(&ctl->tree_lock);
+	__btrfs_return_cluster_to_free_space(block_group, cluster);
+	spin_unlock(&ctl->tree_lock);
+
+	btrfs_discard_queue_work(&block_group->fs_info->discard_ctl, block_group);
+
+	/* finally drop our ref */
+	btrfs_put_block_group(block_group);
+}
+
+static u64 btrfs_alloc_from_bitmap(struct btrfs_block_group *block_group,
+				   struct btrfs_free_cluster *cluster,
+				   struct btrfs_free_space *entry,
+				   u64 bytes, u64 min_start,
+				   u64 *max_extent_size)
+{
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	int err;
+	u64 search_start = cluster->window_start;
+	u64 search_bytes = bytes;
+	u64 ret = 0;
+
+	search_start = min_start;
+	search_bytes = bytes;
+
+	err = search_bitmap(ctl, entry, &search_start, &search_bytes, true);
+	if (err) {
+		*max_extent_size = max(get_max_extent_size(entry),
+				       *max_extent_size);
+		return 0;
+	}
+
+	ret = search_start;
+	bitmap_clear_bits(ctl, entry, ret, bytes, false);
+
+	return ret;
+}
+
+/*
+ * given a cluster, try to allocate 'bytes' from it, returns 0
+ * if it couldn't find anything suitably large, or a logical disk offset
+ * if things worked out
+ */
+u64 btrfs_alloc_from_cluster(struct btrfs_block_group *block_group,
+			     struct btrfs_free_cluster *cluster, u64 bytes,
+			     u64 min_start, u64 *max_extent_size)
+{
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_discard_ctl *discard_ctl =
+					&block_group->fs_info->discard_ctl;
+	struct btrfs_free_space *entry = NULL;
+	struct rb_node *node;
+	u64 ret = 0;
+
+	ASSERT(!btrfs_is_zoned(block_group->fs_info));
+
+	spin_lock(&cluster->lock);
+	if (bytes > cluster->max_size)
+		goto out;
+
+	if (cluster->block_group != block_group)
+		goto out;
+
+	node = rb_first(&cluster->root);
+	if (!node)
+		goto out;
+
+	entry = rb_entry(node, struct btrfs_free_space, offset_index);
+	while (1) {
+		if (entry->bytes < bytes)
+			*max_extent_size = max(get_max_extent_size(entry),
+					       *max_extent_size);
+
+		if (entry->bytes < bytes ||
+		    (!entry->bitmap && entry->offset < min_start)) {
+			node = rb_next(&entry->offset_index);
+			if (!node)
+				break;
+			entry = rb_entry(node, struct btrfs_free_space,
+					 offset_index);
+			continue;
+		}
+
+		if (entry->bitmap) {
+			ret = btrfs_alloc_from_bitmap(block_group,
+						      cluster, entry, bytes,
+						      cluster->window_start,
+						      max_extent_size);
+			if (ret == 0) {
+				node = rb_next(&entry->offset_index);
+				if (!node)
+					break;
+				entry = rb_entry(node, struct btrfs_free_space,
+						 offset_index);
+				continue;
+			}
+			cluster->window_start += bytes;
+		} else {
+			ret = entry->offset;
+
+			entry->offset += bytes;
+			entry->bytes -= bytes;
+		}
+
+		break;
+	}
+out:
+	spin_unlock(&cluster->lock);
+
+	if (!ret)
+		return 0;
+
+	spin_lock(&ctl->tree_lock);
+
+	if (!btrfs_free_space_trimmed(entry))
+		atomic64_add(bytes, &discard_ctl->discard_bytes_saved);
+
+	ctl->free_space -= bytes;
+	if (!entry->bitmap && !btrfs_free_space_trimmed(entry))
+		ctl->discardable_bytes[BTRFS_STAT_CURR] -= bytes;
+
+	spin_lock(&cluster->lock);
+	if (entry->bytes == 0) {
+		rb_erase(&entry->offset_index, &cluster->root);
+		ctl->free_extents--;
+		if (entry->bitmap) {
+			kmem_cache_free(btrfs_free_space_bitmap_cachep,
+					entry->bitmap);
+			ctl->total_bitmaps--;
+			recalculate_thresholds(ctl);
+		} else if (!btrfs_free_space_trimmed(entry)) {
+			ctl->discardable_extents[BTRFS_STAT_CURR]--;
+		}
+		kmem_cache_free(btrfs_free_space_cachep, entry);
+	}
+
+	spin_unlock(&cluster->lock);
+	spin_unlock(&ctl->tree_lock);
+
+	return ret;
+}
+
+static int btrfs_bitmap_cluster(struct btrfs_block_group *block_group,
+				struct btrfs_free_space *entry,
+				struct btrfs_free_cluster *cluster,
+				u64 offset, u64 bytes,
+				u64 cont1_bytes, u64 min_bytes)
+{
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	unsigned long next_zero;
+	unsigned long i;
+	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;
+
+	i = offset_to_bit(entry->offset, ctl->unit,
+			  max_t(u64, offset, entry->offset));
+	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) {
+		next_zero = find_next_zero_bit(entry->bitmap,
+					       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) {
+		entry->max_extent_size = (u64)max_bits * ctl->unit;
+		return -ENOSPC;
+	}
+
+	if (!total_found) {
+		start = i;
+		cluster->max_size = 0;
+	}
+
+	total_found += found_bits;
+
+	if (cluster->max_size < found_bits * ctl->unit)
+		cluster->max_size = found_bits * ctl->unit;
+
+	if (total_found < want_bits || cluster->max_size < cont1_bytes) {
+		i = next_zero + 1;
+		goto again;
+	}
+
+	cluster->window_start = start * ctl->unit + entry->offset;
+	rb_erase(&entry->offset_index, &ctl->free_space_offset);
+	rb_erase_cached(&entry->bytes_index, &ctl->free_space_bytes);
+
+	/*
+	 * We need to know if we're currently on the normal space index when we
+	 * manipulate the bitmap so that we know we need to remove and re-insert
+	 * it into the space_index tree.  Clear the bytes_index node here so the
+	 * bitmap manipulation helpers know not to mess with the space_index
+	 * until this bitmap entry is added back into the normal cache.
+	 */
+	RB_CLEAR_NODE(&entry->bytes_index);
+
+	ret = tree_insert_offset(&cluster->root, entry->offset,
+				 &entry->offset_index, 1);
+	ASSERT(!ret); /* -EEXIST; Logic error */
+
+	trace_btrfs_setup_cluster(block_group, cluster,
+				  total_found * ctl->unit, 1);
+	return 0;
+}
+
+/*
+ * This searches the block group for just extents to fill the cluster with.
+ * Try to find a cluster with at least bytes total bytes, at least one
+ * extent of cont1_bytes, and other clusters of at least min_bytes.
+ */
+static noinline int
+setup_cluster_no_bitmap(struct btrfs_block_group *block_group,
+			struct btrfs_free_cluster *cluster,
+			struct list_head *bitmaps, u64 offset, u64 bytes,
+			u64 cont1_bytes, u64 min_bytes)
+{
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_free_space *first = NULL;
+	struct btrfs_free_space *entry = NULL;
+	struct btrfs_free_space *last;
+	struct rb_node *node;
+	u64 window_free;
+	u64 max_extent;
+	u64 total_size = 0;
+
+	entry = tree_search_offset(ctl, offset, 0, 1);
+	if (!entry)
+		return -ENOSPC;
+
+	/*
+	 * We don't want bitmaps, so just move along until we find a normal
+	 * extent entry.
+	 */
+	while (entry->bitmap || entry->bytes < min_bytes) {
+		if (entry->bitmap && list_empty(&entry->list))
+			list_add_tail(&entry->list, bitmaps);
+		node = rb_next(&entry->offset_index);
+		if (!node)
+			return -ENOSPC;
+		entry = rb_entry(node, struct btrfs_free_space, offset_index);
+	}
+
+	window_free = entry->bytes;
+	max_extent = entry->bytes;
+	first = entry;
+	last = entry;
+
+	for (node = rb_next(&entry->offset_index); node;
+	     node = rb_next(&entry->offset_index)) {
+		entry = rb_entry(node, struct btrfs_free_space, offset_index);
+
+		if (entry->bitmap) {
+			if (list_empty(&entry->list))
+				list_add_tail(&entry->list, bitmaps);
+			continue;
+		}
+
+		if (entry->bytes < min_bytes)
+			continue;
+
+		last = entry;
+		window_free += entry->bytes;
+		if (entry->bytes > max_extent)
+			max_extent = entry->bytes;
+	}
+
+	if (window_free < bytes || max_extent < cont1_bytes)
+		return -ENOSPC;
+
+	cluster->window_start = first->offset;
+
+	node = &first->offset_index;
+
+	/*
+	 * now we've found our entries, pull them out of the free space
+	 * cache and put them into the cluster rbtree
+	 */
+	do {
+		int ret;
+
+		entry = rb_entry(node, struct btrfs_free_space, offset_index);
+		node = rb_next(&entry->offset_index);
+		if (entry->bitmap || entry->bytes < min_bytes)
+			continue;
+
+		rb_erase(&entry->offset_index, &ctl->free_space_offset);
+		rb_erase_cached(&entry->bytes_index, &ctl->free_space_bytes);
+		ret = tree_insert_offset(&cluster->root, entry->offset,
+					 &entry->offset_index, 0);
+		total_size += entry->bytes;
+		ASSERT(!ret); /* -EEXIST; Logic error */
+	} while (node && entry != last);
+
+	cluster->max_size = max_extent;
+	trace_btrfs_setup_cluster(block_group, cluster, total_size, 0);
+	return 0;
+}
+
+/*
+ * This specifically looks for bitmaps that may work in the cluster, we assume
+ * that we have already failed to find extents that will work.
+ */
+static noinline int
+setup_cluster_bitmap(struct btrfs_block_group *block_group,
+		     struct btrfs_free_cluster *cluster,
+		     struct list_head *bitmaps, u64 offset, u64 bytes,
+		     u64 cont1_bytes, u64 min_bytes)
+{
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_free_space *entry = NULL;
+	int ret = -ENOSPC;
+	u64 bitmap_offset = offset_to_bitmap(ctl, offset);
+
+	if (ctl->total_bitmaps == 0)
+		return -ENOSPC;
+
+	/*
+	 * The bitmap that covers offset won't be in the list unless offset
+	 * is just its start offset.
+	 */
+	if (!list_empty(bitmaps))
+		entry = list_first_entry(bitmaps, struct btrfs_free_space, list);
+
+	if (!entry || entry->offset != bitmap_offset) {
+		entry = tree_search_offset(ctl, bitmap_offset, 1, 0);
+		if (entry && list_empty(&entry->list))
+			list_add(&entry->list, bitmaps);
+	}
+
+	list_for_each_entry(entry, bitmaps, list) {
+		if (entry->bytes < bytes)
+			continue;
+		ret = btrfs_bitmap_cluster(block_group, entry, cluster, offset,
+					   bytes, cont1_bytes, min_bytes);
+		if (!ret)
+			return 0;
+	}
+
+	/*
+	 * The bitmaps list has all the bitmaps that record free space
+	 * starting after offset, so no more search is required.
+	 */
+	return -ENOSPC;
+}
+
+/*
+ * here we try to find a cluster of blocks in a block group.  The goal
+ * is to find at least bytes+empty_size.
+ * We might not find them all in one contiguous area.
+ *
+ * returns zero and sets up cluster if things worked out, otherwise
+ * it returns -enospc
+ */
+int btrfs_find_space_cluster(struct btrfs_block_group *block_group,
+			     struct btrfs_free_cluster *cluster,
+			     u64 offset, u64 bytes, u64 empty_size)
+{
+	struct btrfs_fs_info *fs_info = block_group->fs_info;
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_free_space *entry, *tmp;
+	LIST_HEAD(bitmaps);
+	u64 min_bytes;
+	u64 cont1_bytes;
+	int ret;
+
+	/*
+	 * Choose the minimum extent size we'll require for this
+	 * cluster.  For SSD_SPREAD, don't allow any fragmentation.
+	 * For metadata, allow allocates with smaller extents.  For
+	 * data, keep it dense.
+	 */
+	if (btrfs_test_opt(fs_info, SSD_SPREAD)) {
+		cont1_bytes = bytes + empty_size;
+		min_bytes = cont1_bytes;
+	} else if (block_group->flags & BTRFS_BLOCK_GROUP_METADATA) {
+		cont1_bytes = bytes;
+		min_bytes = fs_info->sectorsize;
+	} else {
+		cont1_bytes = max(bytes, (bytes + empty_size) >> 2);
+		min_bytes = fs_info->sectorsize;
+	}
+
+	spin_lock(&ctl->tree_lock);
+
+	/*
+	 * If we know we don't have enough space to make a cluster don't even
+	 * bother doing all the work to try and find one.
+	 */
+	if (ctl->free_space < bytes) {
+		spin_unlock(&ctl->tree_lock);
+		return -ENOSPC;
+	}
+
+	spin_lock(&cluster->lock);
+
+	/* someone already found a cluster, hooray */
+	if (cluster->block_group) {
+		ret = 0;
+		goto out;
+	}
+
+	trace_btrfs_find_cluster(block_group, offset, bytes, empty_size,
+				 min_bytes);
+
+	ret = setup_cluster_no_bitmap(block_group, cluster, &bitmaps, offset,
+				      bytes + empty_size,
+				      cont1_bytes, min_bytes);
+	if (ret)
+		ret = setup_cluster_bitmap(block_group, cluster, &bitmaps,
+					   offset, bytes + empty_size,
+					   cont1_bytes, min_bytes);
+
+	/* Clear our temporary list */
+	list_for_each_entry_safe(entry, tmp, &bitmaps, list)
+		list_del_init(&entry->list);
+
+	if (!ret) {
+		btrfs_get_block_group(block_group);
+		list_add_tail(&cluster->block_group_list,
+			      &block_group->cluster_list);
+		cluster->block_group = block_group;
+	} else {
+		trace_btrfs_failed_cluster_setup(block_group);
+	}
+out:
+	spin_unlock(&cluster->lock);
+	spin_unlock(&ctl->tree_lock);
+
+	return ret;
+}
+
+/*
+ * simple code to zero out a cluster
+ */
+void btrfs_init_free_cluster(struct btrfs_free_cluster *cluster)
+{
+	spin_lock_init(&cluster->lock);
+	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;
+}
+
+static int do_trimming(struct btrfs_block_group *block_group,
+		       u64 *total_trimmed, u64 start, u64 bytes,
+		       u64 reserved_start, u64 reserved_bytes,
+		       enum btrfs_trim_state reserved_trim_state,
+		       struct btrfs_trim_range *trim_entry)
+{
+	struct btrfs_space_info *space_info = block_group->space_info;
+	struct btrfs_fs_info *fs_info = block_group->fs_info;
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	int ret;
+	int update = 0;
+	const u64 end = start + bytes;
+	const u64 reserved_end = reserved_start + reserved_bytes;
+	enum btrfs_trim_state trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+	u64 trimmed = 0;
+
+	spin_lock(&space_info->lock);
+	spin_lock(&block_group->lock);
+	if (!block_group->ro) {
+		block_group->reserved += reserved_bytes;
+		space_info->bytes_reserved += reserved_bytes;
+		update = 1;
+	}
+	spin_unlock(&block_group->lock);
+	spin_unlock(&space_info->lock);
+
+	ret = btrfs_discard_extent(fs_info, start, bytes, &trimmed);
+	if (!ret) {
+		*total_trimmed += trimmed;
+		trim_state = BTRFS_TRIM_STATE_TRIMMED;
+	}
+
+	mutex_lock(&ctl->cache_writeout_mutex);
+	if (reserved_start < start)
+		__btrfs_add_free_space(block_group, reserved_start,
+				       start - reserved_start,
+				       reserved_trim_state);
+	if (start + bytes < reserved_start + reserved_bytes)
+		__btrfs_add_free_space(block_group, end, reserved_end - end,
+				       reserved_trim_state);
+	__btrfs_add_free_space(block_group, start, bytes, trim_state);
+	list_del(&trim_entry->list);
+	mutex_unlock(&ctl->cache_writeout_mutex);
+
+	if (update) {
+		spin_lock(&space_info->lock);
+		spin_lock(&block_group->lock);
+		if (block_group->ro)
+			space_info->bytes_readonly += reserved_bytes;
+		block_group->reserved -= reserved_bytes;
+		space_info->bytes_reserved -= reserved_bytes;
+		spin_unlock(&block_group->lock);
+		spin_unlock(&space_info->lock);
+	}
+
+	return ret;
+}
+
+/*
+ * If @async is set, then we will trim 1 region and return.
+ */
+static int trim_no_bitmap(struct btrfs_block_group *block_group,
+			  u64 *total_trimmed, u64 start, u64 end, u64 minlen,
+			  bool async)
+{
+	struct btrfs_discard_ctl *discard_ctl =
+					&block_group->fs_info->discard_ctl;
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_free_space *entry;
+	struct rb_node *node;
+	int ret = 0;
+	u64 extent_start;
+	u64 extent_bytes;
+	enum btrfs_trim_state extent_trim_state;
+	u64 bytes;
+	const u64 max_discard_size = READ_ONCE(discard_ctl->max_discard_size);
+
+	while (start < end) {
+		struct btrfs_trim_range trim_entry;
+
+		mutex_lock(&ctl->cache_writeout_mutex);
+		spin_lock(&ctl->tree_lock);
+
+		if (ctl->free_space < minlen)
+			goto out_unlock;
+
+		entry = tree_search_offset(ctl, start, 0, 1);
+		if (!entry)
+			goto out_unlock;
+
+		/* Skip bitmaps and if async, already trimmed entries */
+		while (entry->bitmap ||
+		       (async && btrfs_free_space_trimmed(entry))) {
+			node = rb_next(&entry->offset_index);
+			if (!node)
+				goto out_unlock;
+			entry = rb_entry(node, struct btrfs_free_space,
+					 offset_index);
+		}
+
+		if (entry->offset >= end)
+			goto out_unlock;
+
+		extent_start = entry->offset;
+		extent_bytes = entry->bytes;
+		extent_trim_state = entry->trim_state;
+		if (async) {
+			start = entry->offset;
+			bytes = entry->bytes;
+			if (bytes < minlen) {
+				spin_unlock(&ctl->tree_lock);
+				mutex_unlock(&ctl->cache_writeout_mutex);
+				goto next;
+			}
+			unlink_free_space(ctl, entry, true);
+			/*
+			 * Let bytes = BTRFS_MAX_DISCARD_SIZE + X.
+			 * If X < BTRFS_ASYNC_DISCARD_MIN_FILTER, we won't trim
+			 * X when we come back around.  So trim it now.
+			 */
+			if (max_discard_size &&
+			    bytes >= (max_discard_size +
+				      BTRFS_ASYNC_DISCARD_MIN_FILTER)) {
+				bytes = max_discard_size;
+				extent_bytes = max_discard_size;
+				entry->offset += max_discard_size;
+				entry->bytes -= max_discard_size;
+				link_free_space(ctl, entry);
+			} else {
+				kmem_cache_free(btrfs_free_space_cachep, entry);
+			}
+		} else {
+			start = max(start, extent_start);
+			bytes = min(extent_start + extent_bytes, end) - start;
+			if (bytes < minlen) {
+				spin_unlock(&ctl->tree_lock);
+				mutex_unlock(&ctl->cache_writeout_mutex);
+				goto next;
+			}
+
+			unlink_free_space(ctl, entry, true);
+			kmem_cache_free(btrfs_free_space_cachep, entry);
+		}
+
+		spin_unlock(&ctl->tree_lock);
+		trim_entry.start = extent_start;
+		trim_entry.bytes = extent_bytes;
+		list_add_tail(&trim_entry.list, &ctl->trimming_ranges);
+		mutex_unlock(&ctl->cache_writeout_mutex);
+
+		ret = do_trimming(block_group, total_trimmed, start, bytes,
+				  extent_start, extent_bytes, extent_trim_state,
+				  &trim_entry);
+		if (ret) {
+			block_group->discard_cursor = start + bytes;
+			break;
+		}
+next:
+		start += bytes;
+		block_group->discard_cursor = start;
+		if (async && *total_trimmed)
+			break;
+
+		if (fatal_signal_pending(current)) {
+			ret = -ERESTARTSYS;
+			break;
+		}
+
+		cond_resched();
+	}
+
+	return ret;
+
+out_unlock:
+	block_group->discard_cursor = btrfs_block_group_end(block_group);
+	spin_unlock(&ctl->tree_lock);
+	mutex_unlock(&ctl->cache_writeout_mutex);
+
+	return ret;
+}
+
+/*
+ * If we break out of trimming a bitmap prematurely, we should reset the
+ * trimming bit.  In a rather contrieved case, it's possible to race here so
+ * reset the state to BTRFS_TRIM_STATE_UNTRIMMED.
+ *
+ * start = start of bitmap
+ * end = near end of bitmap
+ *
+ * Thread 1:			Thread 2:
+ * trim_bitmaps(start)
+ *				trim_bitmaps(end)
+ *				end_trimming_bitmap()
+ * reset_trimming_bitmap()
+ */
+static void reset_trimming_bitmap(struct btrfs_free_space_ctl *ctl, u64 offset)
+{
+	struct btrfs_free_space *entry;
+
+	spin_lock(&ctl->tree_lock);
+	entry = tree_search_offset(ctl, offset, 1, 0);
+	if (entry) {
+		if (btrfs_free_space_trimmed(entry)) {
+			ctl->discardable_extents[BTRFS_STAT_CURR] +=
+				entry->bitmap_extents;
+			ctl->discardable_bytes[BTRFS_STAT_CURR] += entry->bytes;
+		}
+		entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+	}
+
+	spin_unlock(&ctl->tree_lock);
+}
+
+static void end_trimming_bitmap(struct btrfs_free_space_ctl *ctl,
+				struct btrfs_free_space *entry)
+{
+	if (btrfs_free_space_trimming_bitmap(entry)) {
+		entry->trim_state = BTRFS_TRIM_STATE_TRIMMED;
+		ctl->discardable_extents[BTRFS_STAT_CURR] -=
+			entry->bitmap_extents;
+		ctl->discardable_bytes[BTRFS_STAT_CURR] -= entry->bytes;
+	}
+}
+
+/*
+ * If @async is set, then we will trim 1 region and return.
+ */
+static int trim_bitmaps(struct btrfs_block_group *block_group,
+			u64 *total_trimmed, u64 start, u64 end, u64 minlen,
+			u64 maxlen, bool async)
+{
+	struct btrfs_discard_ctl *discard_ctl =
+					&block_group->fs_info->discard_ctl;
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	struct btrfs_free_space *entry;
+	int ret = 0;
+	int ret2;
+	u64 bytes;
+	u64 offset = offset_to_bitmap(ctl, start);
+	const u64 max_discard_size = READ_ONCE(discard_ctl->max_discard_size);
+
+	while (offset < end) {
+		bool next_bitmap = false;
+		struct btrfs_trim_range trim_entry;
+
+		mutex_lock(&ctl->cache_writeout_mutex);
+		spin_lock(&ctl->tree_lock);
+
+		if (ctl->free_space < minlen) {
+			block_group->discard_cursor =
+				btrfs_block_group_end(block_group);
+			spin_unlock(&ctl->tree_lock);
+			mutex_unlock(&ctl->cache_writeout_mutex);
+			break;
+		}
+
+		entry = tree_search_offset(ctl, offset, 1, 0);
+		/*
+		 * Bitmaps are marked trimmed lossily now to prevent constant
+		 * discarding of the same bitmap (the reason why we are bound
+		 * by the filters).  So, retrim the block group bitmaps when we
+		 * are preparing to punt to the unused_bgs list.  This uses
+		 * @minlen to determine if we are in BTRFS_DISCARD_INDEX_UNUSED
+		 * which is the only discard index which sets minlen to 0.
+		 */
+		if (!entry || (async && minlen && start == offset &&
+			       btrfs_free_space_trimmed(entry))) {
+			spin_unlock(&ctl->tree_lock);
+			mutex_unlock(&ctl->cache_writeout_mutex);
+			next_bitmap = true;
+			goto next;
+		}
+
+		/*
+		 * Async discard bitmap trimming begins at by setting the start
+		 * to be key.objectid and the offset_to_bitmap() aligns to the
+		 * start of the bitmap.  This lets us know we are fully
+		 * scanning the bitmap rather than only some portion of it.
+		 */
+		if (start == offset)
+			entry->trim_state = BTRFS_TRIM_STATE_TRIMMING;
+
+		bytes = minlen;
+		ret2 = search_bitmap(ctl, entry, &start, &bytes, false);
+		if (ret2 || start >= end) {
+			/*
+			 * We lossily consider a bitmap trimmed if we only skip
+			 * over regions <= BTRFS_ASYNC_DISCARD_MIN_FILTER.
+			 */
+			if (ret2 && minlen <= BTRFS_ASYNC_DISCARD_MIN_FILTER)
+				end_trimming_bitmap(ctl, entry);
+			else
+				entry->trim_state = BTRFS_TRIM_STATE_UNTRIMMED;
+			spin_unlock(&ctl->tree_lock);
+			mutex_unlock(&ctl->cache_writeout_mutex);
+			next_bitmap = true;
+			goto next;
+		}
+
+		/*
+		 * We already trimmed a region, but are using the locking above
+		 * to reset the trim_state.
+		 */
+		if (async && *total_trimmed) {
+			spin_unlock(&ctl->tree_lock);
+			mutex_unlock(&ctl->cache_writeout_mutex);
+			goto out;
+		}
+
+		bytes = min(bytes, end - start);
+		if (bytes < minlen || (async && maxlen && bytes > maxlen)) {
+			spin_unlock(&ctl->tree_lock);
+			mutex_unlock(&ctl->cache_writeout_mutex);
+			goto next;
+		}
+
+		/*
+		 * Let bytes = BTRFS_MAX_DISCARD_SIZE + X.
+		 * If X < @minlen, we won't trim X when we come back around.
+		 * So trim it now.  We differ here from trimming extents as we
+		 * don't keep individual state per bit.
+		 */
+		if (async &&
+		    max_discard_size &&
+		    bytes > (max_discard_size + minlen))
+			bytes = max_discard_size;
+
+		bitmap_clear_bits(ctl, entry, start, bytes, true);
+		if (entry->bytes == 0)
+			free_bitmap(ctl, entry);
+
+		spin_unlock(&ctl->tree_lock);
+		trim_entry.start = start;
+		trim_entry.bytes = bytes;
+		list_add_tail(&trim_entry.list, &ctl->trimming_ranges);
+		mutex_unlock(&ctl->cache_writeout_mutex);
+
+		ret = do_trimming(block_group, total_trimmed, start, bytes,
+				  start, bytes, 0, &trim_entry);
+		if (ret) {
+			reset_trimming_bitmap(ctl, offset);
+			block_group->discard_cursor =
+				btrfs_block_group_end(block_group);
+			break;
+		}
+next:
+		if (next_bitmap) {
+			offset += BITS_PER_BITMAP * ctl->unit;
+			start = offset;
+		} else {
+			start += bytes;
+		}
+		block_group->discard_cursor = start;
+
+		if (fatal_signal_pending(current)) {
+			if (start != offset)
+				reset_trimming_bitmap(ctl, offset);
+			ret = -ERESTARTSYS;
+			break;
+		}
+
+		cond_resched();
+	}
+
+	if (offset >= end)
+		block_group->discard_cursor = end;
+
+out:
+	return ret;
+}
+
+int btrfs_trim_block_group(struct btrfs_block_group *block_group,
+			   u64 *trimmed, u64 start, u64 end, u64 minlen)
+{
+	struct btrfs_free_space_ctl *ctl = block_group->free_space_ctl;
+	int ret;
+	u64 rem = 0;
+
+	ASSERT(!btrfs_is_zoned(block_group->fs_info));
+
+	*trimmed = 0;
+
+	spin_lock(&block_group->lock);
+	if (test_bit(BLOCK_GROUP_FLAG_REMOVED, &block_group->runtime_flags)) {
+		spin_unlock(&block_group->lock);
+		return 0;
+	}
+	btrfs_freeze_block_group(block_group);
+	spin_unlock(&block_group->lock);
+
+	ret = trim_no_bitmap(block_group, trimmed, start, end, minlen, false);
+	if (ret)
+		goto out;
+
+	ret = trim_bitmaps(block_group, trimmed, start, end, minlen, 0, false);
+	div64_u64_rem(end, BITS_PER_BITMAP * ctl->unit, &rem);
+	/* If we ended in the middle of a bitmap, reset the trimming flag */
+	if (rem)
+		reset_trimming_bitmap(ctl, offset_to_bitmap(ctl, end));
+out:
+	btrfs_unfreeze_block_group(block_group);
+	return ret;
+}
+
+int btrfs_trim_block_group_extents(struct btrfs_block_group *block_group,
+				   u64 *trimmed, u64 start, u64 end, u64 minlen,
+				   bool async)
+{
+	int ret;
+
+	*trimmed = 0;
+
+	spin_lock(&block_group->lock);
+	if (test_bit(BLOCK_GROUP_FLAG_REMOVED, &block_group->runtime_flags)) {
+		spin_unlock(&block_group->lock);
+		return 0;
+	}
+	btrfs_freeze_block_group(block_group);
+	spin_unlock(&block_group->lock);
+
+	ret = trim_no_bitmap(block_group, trimmed, start, end, minlen, async);
+	btrfs_unfreeze_block_group(block_group);
+
+	return ret;
+}
+
+int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *block_group,
+				   u64 *trimmed, u64 start, u64 end, u64 minlen,
+				   u64 maxlen, bool async)
+{
+	int ret;
+
+	*trimmed = 0;
+
+	spin_lock(&block_group->lock);
+	if (test_bit(BLOCK_GROUP_FLAG_REMOVED, &block_group->runtime_flags)) {
+		spin_unlock(&block_group->lock);
+		return 0;
+	}
+	btrfs_freeze_block_group(block_group);
+	spin_unlock(&block_group->lock);
+
+	ret = trim_bitmaps(block_group, trimmed, start, end, minlen, maxlen,
+			   async);
+
+	btrfs_unfreeze_block_group(block_group);
+
+	return ret;
+}
+
+bool btrfs_free_space_cache_v1_active(struct btrfs_fs_info *fs_info)
+{
+	return btrfs_super_cache_generation(fs_info->super_copy);
+}
+
+static int cleanup_free_space_cache_v1(struct btrfs_fs_info *fs_info,
+				       struct btrfs_trans_handle *trans)
+{
+	struct btrfs_block_group *block_group;
+	struct rb_node *node;
+	int ret = 0;
+
+	btrfs_info(fs_info, "cleaning free space cache v1");
+
+	node = rb_first_cached(&fs_info->block_group_cache_tree);
+	while (node) {
+		block_group = rb_entry(node, struct btrfs_block_group, cache_node);
+		ret = btrfs_remove_free_space_inode(trans, NULL, block_group);
+		if (ret)
+			goto out;
+		node = rb_next(node);
+	}
+out:
+	return ret;
+}
+
+int btrfs_set_free_space_cache_v1_active(struct btrfs_fs_info *fs_info, bool active)
+{
+	struct btrfs_trans_handle *trans;
+	int ret;
+
+	/*
+	 * update_super_roots will appropriately set or unset
+	 * super_copy->cache_generation based on SPACE_CACHE and
+	 * BTRFS_FS_CLEANUP_SPACE_CACHE_V1. For this reason, we need a
+	 * transaction commit whether we are enabling space cache v1 and don't
+	 * have any other work to do, or are disabling it and removing free
+	 * space inodes.
+	 */
+	trans = btrfs_start_transaction(fs_info->tree_root, 0);
+	if (IS_ERR(trans))
+		return PTR_ERR(trans);
+
+	if (!active) {
+		set_bit(BTRFS_FS_CLEANUP_SPACE_CACHE_V1, &fs_info->flags);
+		ret = cleanup_free_space_cache_v1(fs_info, trans);
+		if (ret) {
+			btrfs_abort_transaction(trans, ret);
+			btrfs_end_transaction(trans);
+			goto out;
+		}
+	}
+
+	ret = btrfs_commit_transaction(trans);
+out:
+	clear_bit(BTRFS_FS_CLEANUP_SPACE_CACHE_V1, &fs_info->flags);
+
+	return ret;
+}
+
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+/*
+ * Use this if you need to make a bitmap or extent entry specifically, it
+ * doesn't do any of the merging that add_free_space does, this acts a lot like
+ * how the free space cache loading stuff works, so you can get really weird
+ * configurations.
+ */
+int test_add_free_space_entry(struct btrfs_block_group *cache,
+			      u64 offset, u64 bytes, bool bitmap)
+{
+	struct btrfs_free_space_ctl *ctl = cache->free_space_ctl;
+	struct btrfs_free_space *info = NULL, *bitmap_info;
+	void *map = NULL;
+	enum btrfs_trim_state trim_state = BTRFS_TRIM_STATE_TRIMMED;
+	u64 bytes_added;
+	int ret;
+
+again:
+	if (!info) {
+		info = kmem_cache_zalloc(btrfs_free_space_cachep, GFP_NOFS);
+		if (!info)
+			return -ENOMEM;
+	}
+
+	if (!bitmap) {
+		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)
+			kmem_cache_free(btrfs_free_space_cachep, info);
+		return ret;
+	}
+
+	if (!map) {
+		map = kmem_cache_zalloc(btrfs_free_space_bitmap_cachep, GFP_NOFS);
+		if (!map) {
+			kmem_cache_free(btrfs_free_space_cachep, info);
+			return -ENOMEM;
+		}
+	}
+
+	spin_lock(&ctl->tree_lock);
+	bitmap_info = tree_search_offset(ctl, offset_to_bitmap(ctl, offset),
+					 1, 0);
+	if (!bitmap_info) {
+		info->bitmap = map;
+		map = NULL;
+		add_new_bitmap(ctl, info, offset);
+		bitmap_info = info;
+		info = NULL;
+	}
+
+	bytes_added = add_bytes_to_bitmap(ctl, bitmap_info, offset, bytes,
+					  trim_state);
+
+	bytes -= bytes_added;
+	offset += bytes_added;
+	spin_unlock(&ctl->tree_lock);
+
+	if (bytes)
+		goto again;
+
+	if (info)
+		kmem_cache_free(btrfs_free_space_cachep, info);
+	if (map)
+		kmem_cache_free(btrfs_free_space_bitmap_cachep, map);
+	return 0;
+}
+
+/*
+ * Checks to see if the given range is in the free space cache.  This is really
+ * just used to check the absence of space, so if there is free space in the
+ * range at all we will return 1.
+ */
+int test_check_exists(struct btrfs_block_group *cache,
+		      u64 offset, u64 bytes)
+{
+	struct btrfs_free_space_ctl *ctl = cache->free_space_ctl;
+	struct btrfs_free_space *info;
+	int ret = 0;
+
+	spin_lock(&ctl->tree_lock);
+	info = tree_search_offset(ctl, offset, 0, 0);
+	if (!info) {
+		info = tree_search_offset(ctl, offset_to_bitmap(ctl, offset),
+					  1, 0);
+		if (!info)
+			goto out;
+	}
+
+have_info:
+	if (info->bitmap) {
+		u64 bit_off, bit_bytes;
+		struct rb_node *n;
+		struct btrfs_free_space *tmp;
+
+		bit_off = offset;
+		bit_bytes = ctl->unit;
+		ret = search_bitmap(ctl, info, &bit_off, &bit_bytes, false);
+		if (!ret) {
+			if (bit_off == offset) {
+				ret = 1;
+				goto out;
+			} else if (bit_off > offset &&
+				   offset + bytes > bit_off) {
+				ret = 1;
+				goto out;
+			}
+		}
+
+		n = rb_prev(&info->offset_index);
+		while (n) {
+			tmp = rb_entry(n, struct btrfs_free_space,
+				       offset_index);
+			if (tmp->offset + tmp->bytes < offset)
+				break;
+			if (offset + bytes < tmp->offset) {
+				n = rb_prev(&tmp->offset_index);
+				continue;
+			}
+			info = tmp;
+			goto have_info;
+		}
+
+		n = rb_next(&info->offset_index);
+		while (n) {
+			tmp = rb_entry(n, struct btrfs_free_space,
+				       offset_index);
+			if (offset + bytes < tmp->offset)
+				break;
+			if (tmp->offset + tmp->bytes < offset) {
+				n = rb_next(&tmp->offset_index);
+				continue;
+			}
+			info = tmp;
+			goto have_info;
+		}
+
+		ret = 0;
+		goto out;
+	}
+
+	if (info->offset == offset) {
+		ret = 1;
+		goto out;
+	}
+
+	if (offset > info->offset && offset < info->offset + info->bytes)
+		ret = 1;
+out:
+	spin_unlock(&ctl->tree_lock);
+	return ret;
+}
+#endif /* CONFIG_BTRFS_FS_RUN_SANITY_TESTS */