fs/exfat/balloc.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *  Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
  */

 #include <linux/blkdev.h>
 #include <linux/slab.h>
 #include <linux/buffer_head.h>

 #include "exfat_raw.h"
 #include "exfat_fs.h"

 static const unsigned char free_bit[] = {
 	0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2,/*  0 ~  19*/
 	0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 5, 0, 1, 0, 2, 0, 1, 0, 3,/* 20 ~  39*/
 	0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2,/* 40 ~  59*/
 	0, 1, 0, 6, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4,/* 60 ~  79*/
 	0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 5, 0, 1, 0, 2,/* 80 ~  99*/
 	0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3,/*100 ~ 119*/
 	0, 1, 0, 2, 0, 1, 0, 7, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2,/*120 ~ 139*/
 	0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 5,/*140 ~ 159*/
 	0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2,/*160 ~ 179*/
 	0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 6, 0, 1, 0, 2, 0, 1, 0, 3,/*180 ~ 199*/
 	0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2,/*200 ~ 219*/
 	0, 1, 0, 5, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4,/*220 ~ 239*/
 	0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0                /*240 ~ 254*/
 };

 static const unsigned char used_bit[] = {
 	0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, 2, 2, 3,/*  0 ~  19*/
 	2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 1, 2, 2, 3, 2, 3, 3, 4,/* 20 ~  39*/
 	2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5,/* 40 ~  59*/
 	4, 5, 5, 6, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,/* 60 ~  79*/
 	2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 2, 3, 3, 4,/* 80 ~  99*/
 	3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6,/*100 ~ 119*/
 	4, 5, 5, 6, 5, 6, 6, 7, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4,/*120 ~ 139*/
 	3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,/*140 ~ 159*/
 	2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5,/*160 ~ 179*/
 	4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 2, 3, 3, 4, 3, 4, 4, 5,/*180 ~ 199*/
 	3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6,/*200 ~ 219*/
 	5, 6, 6, 7, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,/*220 ~ 239*/
 	4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8             /*240 ~ 255*/
 };

 /*
  *  Allocation Bitmap Management Functions
  */
 static int exfat_allocate_bitmap(struct super_block *sb,
 		struct exfat_dentry *ep)
 {
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 	long long map_size;
 	unsigned int i, need_map_size;
 	sector_t sector;

 	sbi->map_clu = le32_to_cpu(ep->dentry.bitmap.start_clu);
 	map_size = le64_to_cpu(ep->dentry.bitmap.size);
 	need_map_size = ((EXFAT_DATA_CLUSTER_COUNT(sbi) - 1) / BITS_PER_BYTE)
 		+ 1;
 	if (need_map_size != map_size) {
 		exfat_err(sb, "bogus allocation bitmap size(need : %u, cur : %lld)",
 			  need_map_size, map_size);
 		/*
 		 * Only allowed when bogus allocation
 		 * bitmap size is large
 		 */
 		if (need_map_size > map_size)
 			return -EIO;
 	}
 	sbi->map_sectors = ((need_map_size - 1) >>
 			(sb->s_blocksize_bits)) + 1;
 	sbi->vol_amap = kmalloc_array(sbi->map_sectors,
 				sizeof(struct buffer_head *), GFP_KERNEL);
 	if (!sbi->vol_amap)
 		return -ENOMEM;

 	sector = exfat_cluster_to_sector(sbi, sbi->map_clu);
 	for (i = 0; i < sbi->map_sectors; i++) {
 		sbi->vol_amap[i] = sb_bread(sb, sector + i);
 		if (!sbi->vol_amap[i]) {
 			/* release all buffers and free vol_amap */
 			int j = 0;

 			while (j < i)
 				brelse(sbi->vol_amap[j++]);

 			kfree(sbi->vol_amap);
 			sbi->vol_amap = NULL;
 			return -EIO;
 		}
 	}

 	return 0;
 }

 int exfat_load_bitmap(struct super_block *sb)
 {
 	unsigned int i, type;
 	struct exfat_chain clu;
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);

 	exfat_chain_set(&clu, sbi->root_dir, 0, ALLOC_FAT_CHAIN);
 	while (clu.dir != EXFAT_EOF_CLUSTER) {
 		for (i = 0; i < sbi->dentries_per_clu; i++) {
 			struct exfat_dentry *ep;
 			struct buffer_head *bh;

 			ep = exfat_get_dentry(sb, &clu, i, &bh, NULL);
 			if (!ep)
 				return -EIO;

 			type = exfat_get_entry_type(ep);
 			if (type == TYPE_UNUSED)
 				break;
 			if (type != TYPE_BITMAP)
 				continue;
 			if (ep->dentry.bitmap.flags == 0x0) {
 				int err;

 				err = exfat_allocate_bitmap(sb, ep);
 				brelse(bh);
 				return err;
 			}
 			brelse(bh);
 		}

 		if (exfat_get_next_cluster(sb, &clu.dir))
 			return -EIO;
 	}

 	return -EINVAL;
 }

 void exfat_free_bitmap(struct exfat_sb_info *sbi)
 {
 	int i;

 	for (i = 0; i < sbi->map_sectors; i++)
 		__brelse(sbi->vol_amap[i]);

 	kfree(sbi->vol_amap);
 }

 /*
  * If the value of "clu" is 0, it means cluster 2 which is the first cluster of
  * the cluster heap.
  */
 int exfat_set_bitmap(struct inode *inode, unsigned int clu)
 {
 	int i, b;
 	unsigned int ent_idx;
 	struct super_block *sb = inode->i_sb;
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);

 	WARN_ON(clu < EXFAT_FIRST_CLUSTER);
 	ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
 	i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
 	b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);

 	set_bit_le(b, sbi->vol_amap[i]->b_data);
 	exfat_update_bh(sbi->vol_amap[i], IS_DIRSYNC(inode));
 	return 0;
 }

 /*
  * If the value of "clu" is 0, it means cluster 2 which is the first cluster of
  * the cluster heap.
  */
 void exfat_clear_bitmap(struct inode *inode, unsigned int clu)
 {
 	int i, b;
 	unsigned int ent_idx;
 	struct super_block *sb = inode->i_sb;
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 	struct exfat_mount_options *opts = &sbi->options;

 	WARN_ON(clu < EXFAT_FIRST_CLUSTER);
 	ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
 	i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
 	b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);

 	clear_bit_le(b, sbi->vol_amap[i]->b_data);
 	exfat_update_bh(sbi->vol_amap[i], IS_DIRSYNC(inode));

 	if (opts->discard) {
 		int ret_discard;

 		ret_discard = sb_issue_discard(sb,
 			exfat_cluster_to_sector(sbi, clu +
 						EXFAT_RESERVED_CLUSTERS),
 			(1 << sbi->sect_per_clus_bits), GFP_NOFS, 0);

 		if (ret_discard == -EOPNOTSUPP) {
 			exfat_err(sb, "discard not supported by device, disabling");
 			opts->discard = 0;
 		}
 	}
 }

 /*
  * If the value of "clu" is 0, it means cluster 2 which is the first cluster of
  * the cluster heap.
  */
 unsigned int exfat_find_free_bitmap(struct super_block *sb, unsigned int clu)
 {
 	unsigned int i, map_i, map_b, ent_idx;
 	unsigned int clu_base, clu_free;
 	unsigned char k, clu_mask;
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);

 	WARN_ON(clu < EXFAT_FIRST_CLUSTER);
 	ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
 	clu_base = BITMAP_ENT_TO_CLUSTER(ent_idx & ~(BITS_PER_BYTE_MASK));
 	clu_mask = IGNORED_BITS_REMAINED(clu, clu_base);

 	map_i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
 	map_b = BITMAP_OFFSET_BYTE_IN_SECTOR(sb, ent_idx);

 	for (i = EXFAT_FIRST_CLUSTER; i < sbi->num_clusters;
 	     i += BITS_PER_BYTE) {
 		k = *(sbi->vol_amap[map_i]->b_data + map_b);
 		if (clu_mask > 0) {
 			k |= clu_mask;
 			clu_mask = 0;
 		}
 		if (k < 0xFF) {
 			clu_free = clu_base + free_bit[k];
 			if (clu_free < sbi->num_clusters)
 				return clu_free;
 		}
 		clu_base += BITS_PER_BYTE;

 		if (++map_b >= sb->s_blocksize ||
 		    clu_base >= sbi->num_clusters) {
 			if (++map_i >= sbi->map_sectors) {
 				clu_base = EXFAT_FIRST_CLUSTER;
 				map_i = 0;
 			}
 			map_b = 0;
 		}
 	}

 	return EXFAT_EOF_CLUSTER;
 }

 int exfat_count_used_clusters(struct super_block *sb, unsigned int *ret_count)
 {
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 	unsigned int count = 0;
 	unsigned int i, map_i = 0, map_b = 0;
 	unsigned int total_clus = EXFAT_DATA_CLUSTER_COUNT(sbi);
 	unsigned int last_mask = total_clus & BITS_PER_BYTE_MASK;
 	unsigned char clu_bits;
 	const unsigned char last_bit_mask[] = {0, 0b00000001, 0b00000011,
 		0b00000111, 0b00001111, 0b00011111, 0b00111111, 0b01111111};

 	total_clus &= ~last_mask;
 	for (i = 0; i < total_clus; i += BITS_PER_BYTE) {
 		clu_bits = *(sbi->vol_amap[map_i]->b_data + map_b);
 		count += used_bit[clu_bits];
 		if (++map_b >= (unsigned int)sb->s_blocksize) {
 			map_i++;
 			map_b = 0;
 		}
 	}

 	if (last_mask) {
 		clu_bits = *(sbi->vol_amap[map_i]->b_data + map_b);
 		clu_bits &= last_bit_mask[last_mask];
 		count += used_bit[clu_bits];
 	}

 	*ret_count = count;
 	return 0;
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
	*/

	#include <linux/blkdev.h>
	#include <linux/slab.h>
	#include <linux/buffer_head.h>

	#include "exfat_raw.h"
	#include "exfat_fs.h"

	static const unsigned char free_bit[] = {
	0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2,/* 0 ~ 19*/
	0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 5, 0, 1, 0, 2, 0, 1, 0, 3,/* 20 ~ 39*/
	0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2,/* 40 ~ 59*/
	0, 1, 0, 6, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4,/* 60 ~ 79*/
	0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 5, 0, 1, 0, 2,/* 80 ~ 99*/
	0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3,/100 ~ 119/
	0, 1, 0, 2, 0, 1, 0, 7, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2,/120 ~ 139/
	0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 5,/140 ~ 159/
	0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2,/160 ~ 179/
	0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 6, 0, 1, 0, 2, 0, 1, 0, 3,/180 ~ 199/
	0, 1, 0, 2, 0, 1, 0, 4, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2,/200 ~ 219/
	0, 1, 0, 5, 0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0, 4,/220 ~ 239/
	0, 1, 0, 2, 0, 1, 0, 3, 0, 1, 0, 2, 0, 1, 0 /240 ~ 254/
	};

	static const unsigned char used_bit[] = {
	0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, 2, 2, 3,/* 0 ~ 19*/
	2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 1, 2, 2, 3, 2, 3, 3, 4,/* 20 ~ 39*/
	2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5,/* 40 ~ 59*/
	4, 5, 5, 6, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,/* 60 ~ 79*/
	2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 2, 3, 3, 4,/* 80 ~ 99*/
	3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6,/100 ~ 119/
	4, 5, 5, 6, 5, 6, 6, 7, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4,/120 ~ 139/
	3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,/140 ~ 159/
	2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5,/160 ~ 179/
	4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 2, 3, 3, 4, 3, 4, 4, 5,/180 ~ 199/
	3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6,/200 ~ 219/
	5, 6, 6, 7, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,/220 ~ 239/
	4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8 /240 ~ 255/
	};

	/*
	* Allocation Bitmap Management Functions
	*/
	static int exfat_allocate_bitmap(struct super_block *sb,
	struct exfat_dentry *ep)
	{
	struct exfat_sb_info *sbi = EXFAT_SB(sb);
	long long map_size;
	unsigned int i, need_map_size;
	sector_t sector;

	sbi->map_clu = le32_to_cpu(ep->dentry.bitmap.start_clu);
	map_size = le64_to_cpu(ep->dentry.bitmap.size);
	need_map_size = ((EXFAT_DATA_CLUSTER_COUNT(sbi) - 1) / BITS_PER_BYTE)
	+ 1;
	if (need_map_size != map_size) {
	exfat_err(sb, "bogus allocation bitmap size(need : %u, cur : %lld)",
	need_map_size, map_size);
	/*
	* Only allowed when bogus allocation
	* bitmap size is large
	*/
	if (need_map_size > map_size)
	return -EIO;
	}
	sbi->map_sectors = ((need_map_size - 1) >>
	(sb->s_blocksize_bits)) + 1;
	sbi->vol_amap = kmalloc_array(sbi->map_sectors,
	sizeof(struct buffer_head *), GFP_KERNEL);
	if (!sbi->vol_amap)
	return -ENOMEM;

	sector = exfat_cluster_to_sector(sbi, sbi->map_clu);
	for (i = 0; i < sbi->map_sectors; i++) {
	sbi->vol_amap[i] = sb_bread(sb, sector + i);
	if (!sbi->vol_amap[i]) {
	/* release all buffers and free vol_amap */
	int j = 0;

	while (j < i)
	brelse(sbi->vol_amap[j++]);

	kfree(sbi->vol_amap);
	sbi->vol_amap = NULL;
	return -EIO;
	}
	}

	return 0;
	}

	int exfat_load_bitmap(struct super_block *sb)
	{
	unsigned int i, type;
	struct exfat_chain clu;
	struct exfat_sb_info *sbi = EXFAT_SB(sb);

	exfat_chain_set(&clu, sbi->root_dir, 0, ALLOC_FAT_CHAIN);
	while (clu.dir != EXFAT_EOF_CLUSTER) {
	for (i = 0; i < sbi->dentries_per_clu; i++) {
	struct exfat_dentry *ep;
	struct buffer_head *bh;

	ep = exfat_get_dentry(sb, &clu, i, &bh, NULL);
	if (!ep)
	return -EIO;

	type = exfat_get_entry_type(ep);
	if (type == TYPE_UNUSED)
	break;
	if (type != TYPE_BITMAP)
	continue;
	if (ep->dentry.bitmap.flags == 0x0) {
	int err;

	err = exfat_allocate_bitmap(sb, ep);
	brelse(bh);
	return err;
	}
	brelse(bh);
	}

	if (exfat_get_next_cluster(sb, &clu.dir))
	return -EIO;
	}

	return -EINVAL;
	}

	void exfat_free_bitmap(struct exfat_sb_info *sbi)
	{
	int i;

	for (i = 0; i < sbi->map_sectors; i++)
	__brelse(sbi->vol_amap[i]);

	kfree(sbi->vol_amap);
	}

	/*
	* If the value of "clu" is 0, it means cluster 2 which is the first cluster of
	* the cluster heap.
	*/
	int exfat_set_bitmap(struct inode *inode, unsigned int clu)
	{
	int i, b;
	unsigned int ent_idx;
	struct super_block *sb = inode->i_sb;
	struct exfat_sb_info *sbi = EXFAT_SB(sb);

	WARN_ON(clu < EXFAT_FIRST_CLUSTER);
	ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
	i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
	b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);

	set_bit_le(b, sbi->vol_amap[i]->b_data);
	exfat_update_bh(sbi->vol_amap[i], IS_DIRSYNC(inode));
	return 0;
	}

	/*
	* If the value of "clu" is 0, it means cluster 2 which is the first cluster of
	* the cluster heap.
	*/
	void exfat_clear_bitmap(struct inode *inode, unsigned int clu)
	{
	int i, b;
	unsigned int ent_idx;
	struct super_block *sb = inode->i_sb;
	struct exfat_sb_info *sbi = EXFAT_SB(sb);
	struct exfat_mount_options *opts = &sbi->options;

	WARN_ON(clu < EXFAT_FIRST_CLUSTER);
	ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
	i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
	b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);

	clear_bit_le(b, sbi->vol_amap[i]->b_data);
	exfat_update_bh(sbi->vol_amap[i], IS_DIRSYNC(inode));

	if (opts->discard) {
	int ret_discard;

	ret_discard = sb_issue_discard(sb,
	exfat_cluster_to_sector(sbi, clu +
	EXFAT_RESERVED_CLUSTERS),
	(1 << sbi->sect_per_clus_bits), GFP_NOFS, 0);

	if (ret_discard == -EOPNOTSUPP) {
	exfat_err(sb, "discard not supported by device, disabling");
	opts->discard = 0;
	}
	}
	}

	/*
	* If the value of "clu" is 0, it means cluster 2 which is the first cluster of
	* the cluster heap.
	*/
	unsigned int exfat_find_free_bitmap(struct super_block *sb, unsigned int clu)
	{
	unsigned int i, map_i, map_b, ent_idx;
	unsigned int clu_base, clu_free;
	unsigned char k, clu_mask;
	struct exfat_sb_info *sbi = EXFAT_SB(sb);

	WARN_ON(clu < EXFAT_FIRST_CLUSTER);
	ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
	clu_base = BITMAP_ENT_TO_CLUSTER(ent_idx & ~(BITS_PER_BYTE_MASK));
	clu_mask = IGNORED_BITS_REMAINED(clu, clu_base);

	map_i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
	map_b = BITMAP_OFFSET_BYTE_IN_SECTOR(sb, ent_idx);

	for (i = EXFAT_FIRST_CLUSTER; i < sbi->num_clusters;
	i += BITS_PER_BYTE) {
	k = *(sbi->vol_amap[map_i]->b_data + map_b);
	if (clu_mask > 0) {
	k \|= clu_mask;
	clu_mask = 0;
	}
	if (k < 0xFF) {
	clu_free = clu_base + free_bit[k];
	if (clu_free < sbi->num_clusters)
	return clu_free;
	}
	clu_base += BITS_PER_BYTE;

	if (++map_b >= sb->s_blocksize \|\|
	clu_base >= sbi->num_clusters) {
	if (++map_i >= sbi->map_sectors) {
	clu_base = EXFAT_FIRST_CLUSTER;
	map_i = 0;
	}
	map_b = 0;
	}
	}

	return EXFAT_EOF_CLUSTER;
	}

	int exfat_count_used_clusters(struct super_block sb, unsigned int ret_count)
	{
	struct exfat_sb_info *sbi = EXFAT_SB(sb);
	unsigned int count = 0;
	unsigned int i, map_i = 0, map_b = 0;
	unsigned int total_clus = EXFAT_DATA_CLUSTER_COUNT(sbi);
	unsigned int last_mask = total_clus & BITS_PER_BYTE_MASK;
	unsigned char clu_bits;
	const unsigned char last_bit_mask[] = {0, 0b00000001, 0b00000011,
	0b00000111, 0b00001111, 0b00011111, 0b00111111, 0b01111111};

	total_clus &= ~last_mask;
	for (i = 0; i < total_clus; i += BITS_PER_BYTE) {
	clu_bits = *(sbi->vol_amap[map_i]->b_data + map_b);
	count += used_bit[clu_bits];
	if (++map_b >= (unsigned int)sb->s_blocksize) {
	map_i++;
	map_b = 0;
	}
	}

	if (last_mask) {
	clu_bits = *(sbi->vol_amap[map_i]->b_data + map_b);
	clu_bits &= last_bit_mask[last_mask];
	count += used_bit[clu_bits];
	}

	*ret_count = count;
	return 0;
	}