path: root/fs/btrfs/free-space-tree.c

/*
 * Copyright (C) 2015 Facebook.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/kernel.h>
#include <linux/vmalloc.h>
#include "ctree.h"
#include "disk-io.h"
#include "locking.h"
#include "free-space-tree.h"
#include "transaction.h"

static int __add_block_group_free_space(struct btrfs_trans_handle *trans,
					struct btrfs_fs_info *fs_info,
					struct btrfs_block_group_cache *block_group,
					struct btrfs_path *path);

void set_free_space_tree_thresholds(struct btrfs_block_group_cache *cache)
{
	u32 bitmap_range;
	size_t bitmap_size;
	u64 num_bitmaps, total_bitmap_size;

	/*
	 * We convert to bitmaps when the disk space required for using extents
	 * exceeds that required for using bitmaps.
	 */
	bitmap_range = cache->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;
	num_bitmaps = div_u64(cache->key.offset + bitmap_range - 1,
			      bitmap_range);
	bitmap_size = sizeof(struct btrfs_item) + BTRFS_FREE_SPACE_BITMAP_SIZE;
	total_bitmap_size = num_bitmaps * bitmap_size;
	cache->bitmap_high_thresh = div_u64(total_bitmap_size,
					    sizeof(struct btrfs_item));

	/*
	 * We allow for a small buffer between the high threshold and low
	 * threshold to avoid thrashing back and forth between the two formats.
	 */
	if (cache->bitmap_high_thresh > 100)
		cache->bitmap_low_thresh = cache->bitmap_high_thresh - 100;
	else
		cache->bitmap_low_thresh = 0;
}

static int add_new_free_space_info(struct btrfs_trans_handle *trans,
				   struct btrfs_fs_info *fs_info,
				   struct btrfs_block_group_cache *block_group,
				   struct btrfs_path *path)
{
	struct btrfs_root *root = fs_info->free_space_root;
	struct btrfs_free_space_info *info;
	struct btrfs_key key;
	struct extent_buffer *leaf;
	int ret;

	key.objectid = block_group->key.objectid;
	key.type = BTRFS_FREE_SPACE_INFO_KEY;
	key.offset = block_group->key.offset;

	ret = btrfs_insert_empty_item(trans, root, path, &key, sizeof(*info));
	if (ret)
		goto out;

	leaf = path->nodes[0];
	info = btrfs_item_ptr(leaf, path->slots[0],
			      struct btrfs_free_space_info);
	btrfs_set_free_space_extent_count(leaf, info, 0);
	btrfs_set_free_space_flags(leaf, info, 0);
	btrfs_mark_buffer_dirty(leaf);

	ret = 0;
out:
	btrfs_release_path(path);
	return ret;
}

struct btrfs_free_space_info *
search_free_space_info(struct btrfs_trans_handle *trans,
		       struct btrfs_fs_info *fs_info,
		       struct btrfs_block_group_cache *block_group,
		       struct btrfs_path *path, int cow)
{
	struct btrfs_root *root = fs_info->free_space_root;
	struct btrfs_key key;
	int ret;

	key.objectid = block_group->key.objectid;
	key.type = BTRFS_FREE_SPACE_INFO_KEY;
	key.offset = block_group->key.offset;

	ret = btrfs_search_slot(trans, root, &key, path, 0, cow);
	if (ret < 0)
		return ERR_PTR(ret);
	if (ret != 0) {
		btrfs_warn(fs_info, "missing free space info for %llu",
			   block_group->key.objectid);
		ASSERT(0);
		return ERR_PTR(-ENOENT);
	}

	return btrfs_item_ptr(path->nodes[0], path->slots[0],
			      struct btrfs_free_space_info);
}

/*
 * btrfs_search_slot() but we're looking for the greatest key less than the
 * passed key.
 */
static int btrfs_search_prev_slot(struct btrfs_trans_handle *trans,
				  struct btrfs_root *root,
				  struct btrfs_key *key, struct btrfs_path *p,
				  int ins_len, int cow)
{
	int ret;

	ret = btrfs_search_slot(trans, root, key, p, ins_len, cow);
	if (ret < 0)
		return ret;

	if (ret == 0) {
		ASSERT(0);
		return -EIO;
	}

	if (p->slots[0] == 0) {
		ASSERT(0);
		return -EIO;
	}
	p->slots[0]--;

	return 0;
}

static inline u32 free_space_bitmap_size(u64 size, u32 sectorsize)
{
	return DIV_ROUND_UP((u32)div_u64(size, sectorsize), BITS_PER_BYTE);
}

static u8 *alloc_bitmap(u32 bitmap_size)
{
	void *mem;

	/*
	 * The allocation size varies, observed numbers were < 4K up to 16K.
	 * Using vmalloc unconditionally would be too heavy, we'll try
	 * contiguous allocations first.
	 */
	if  (bitmap_size <= PAGE_SIZE)
		return kzalloc(bitmap_size, GFP_NOFS);

	mem = kzalloc(bitmap_size, GFP_NOFS | __GFP_NOWARN);
	if (mem)
		return mem;

	return __vmalloc(bitmap_size, GFP_NOFS | __GFP_HIGHMEM | __GFP_ZERO,
			 PAGE_KERNEL);
}

int convert_free_space_to_bitmaps(struct btrfs_trans_handle *trans,
				  struct btrfs_fs_info *fs_info,
				  struct btrfs_block_group_cache *block_group,
				  struct btrfs_path *path)
{
	struct btrfs_r