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

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2015 Facebook.  All rights reserved.
 */

#include <linux/kernel.h>
#include <linux/sched/mm.h>
#include "messages.h"
#include "ctree.h"
#include "disk-io.h"
#include "locking.h"
#include "free-space-tree.h"
#include "transaction.h"
#include "block-group.h"
#include "fs.h"
#include "accessors.h"
#include "extent-tree.h"
#include "root-tree.h"

static int __add_block_group_free_space(struct btrfs_trans_handle *trans,
					struct btrfs_block_group *block_group,
					struct btrfs_path *path);

static struct btrfs_root *btrfs_free_space_root(
				struct btrfs_block_group *block_group)
{
	struct btrfs_key key = {
		.objectid = BTRFS_FREE_SPACE_TREE_OBJECTID,
		.type = BTRFS_ROOT_ITEM_KEY,
		.offset = 0,
	};

	if (btrfs_fs_incompat(block_group->fs_info, EXTENT_TREE_V2))
		key.offset = block_group->global_root_id;
	return btrfs_global_root(block_group->fs_info, &key);
}

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

	if (WARN_ON(cache->length == 0))
		btrfs_warn(cache->fs_info, "block group %llu length is zero",
			   cache->start);

	/*
	 * We convert to bitmaps when the disk space required for using extents
	 * exceeds that required for using bitmaps.
	 */
	bitmap_range = cache->fs_info->sectorsize * BTRFS_FREE_SPACE_BITMAP_BITS;
	num_bitmaps = div_u64(cache->length + bitmap_range - 1, bitmap_range);
	bitmap_size = sizeof(struct btrfs_item) + BTRFS_FREE_SPACE_BITMAP_SIZE;
	total_bitmap_size = num_bitmaps * bitmap_size;
	cache->bitmap_high_thresh = div_u64(total_bitmap_size,
					    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_block_group *block_group,
				   struct btrfs_path *path)
{
	struct btrfs_root *root = btrfs_free_space_root(block_group);
	struct btrfs_free_space_info *info;
	struct btrfs_key key;
	struct extent_buffer *leaf;
	int ret;

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

	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;
}

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

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

	ret = btrfs_search_slot(trans, root, &key, path, 0, cow);
	if (ret < 0)
		return ERR_PTR(ret);
	if (ret != 0) {
		btrfs_warn(fs_info, "missing free space info for %llu",
			   block_group->start);
		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(const struct btrfs_fs_info *fs_info,
					 u64 size)
{
	return DIV_ROUND_UP(size >> fs_info->sectorsize_bits, BITS_PER_BYTE);
}

static unsigned long *alloc_bitmap(u32 bitmap_size)
{
	unsigned long *ret;
	unsigned int nofs_flag;
	u32 bitmap_rounded_size = round_up(bitmap_size, sizeof(unsigned long));

	/*
	 * GFP_NOFS doesn't work with kvmalloc(), but we really can't recurse
	 * into the filesystem as the free space bitmap can be modified in the
	 * critical section of a transaction commit.
	 *
	 * TODO: push the memalloc_nofs_{save,restore}() to the caller where we
	 * know that recursion is unsafe.
	 */
	nofs_flag = memalloc_nofs_save();
	ret = kvzalloc(bitmap_rounded_size, GFP_KERNEL);
	memalloc_nofs_restore(nofs_flag);
	return ret;
}

static void le_bitmap_set(unsigned long *map, unsigned int start, int len)
{
	u8 *p = ((u8 *)map) + BIT_BYTE(start);
	const unsigned int size = start + len;
	int bits_to_set = BITS_PER_BYTE - (start % BITS_PER_BYTE);
	u8 mask_to_set = BITMAP_FIRST_BYTE_MASK(start);

	while (len - bits_to_set >= 0) {
		*p |= mask_to_set;
		len -= bits_to_set;
		bits_to_set = BITS_PER_BYTE;
		mask_to_set = ~0;
		p++;
	}