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

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

 #include <linux/slab.h>
 #include <asm/unaligned.h>
 #include <linux/buffer_head.h>

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

 static int exfat_mirror_bh(struct super_block *sb, sector_t sec,
 		struct buffer_head *bh)
 {
 	struct buffer_head *c_bh;
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 	sector_t sec2;
 	int err = 0;

 	if (sbi->FAT2_start_sector != sbi->FAT1_start_sector) {
 		sec2 = sec - sbi->FAT1_start_sector + sbi->FAT2_start_sector;
 		c_bh = sb_getblk(sb, sec2);
 		if (!c_bh)
 			return -ENOMEM;
 		memcpy(c_bh->b_data, bh->b_data, sb->s_blocksize);
 		set_buffer_uptodate(c_bh);
 		mark_buffer_dirty(c_bh);
 		if (sb->s_flags & SB_SYNCHRONOUS)
 			err = sync_dirty_buffer(c_bh);
 		brelse(c_bh);
 	}

 	return err;
 }

 static int __exfat_ent_get(struct super_block *sb, unsigned int loc,
 		unsigned int *content)
 {
 	unsigned int off;
 	sector_t sec;
 	struct buffer_head *bh;

 	sec = FAT_ENT_OFFSET_SECTOR(sb, loc);
 	off = FAT_ENT_OFFSET_BYTE_IN_SECTOR(sb, loc);

 	bh = sb_bread(sb, sec);
 	if (!bh)
 		return -EIO;

 	*content = le32_to_cpu(*(__le32 *)(&bh->b_data[off]));

 	/* remap reserved clusters to simplify code */
 	if (*content > EXFAT_BAD_CLUSTER)
 		*content = EXFAT_EOF_CLUSTER;

 	brelse(bh);
 	return 0;
 }

 int exfat_ent_set(struct super_block *sb, unsigned int loc,
 		unsigned int content)
 {
 	unsigned int off;
 	sector_t sec;
 	__le32 *fat_entry;
 	struct buffer_head *bh;

 	sec = FAT_ENT_OFFSET_SECTOR(sb, loc);
 	off = FAT_ENT_OFFSET_BYTE_IN_SECTOR(sb, loc);

 	bh = sb_bread(sb, sec);
 	if (!bh)
 		return -EIO;

 	fat_entry = (__le32 *)&(bh->b_data[off]);
 	*fat_entry = cpu_to_le32(content);
 	exfat_update_bh(bh, sb->s_flags & SB_SYNCHRONOUS);
 	exfat_mirror_bh(sb, sec, bh);
 	brelse(bh);
 	return 0;
 }

 static inline bool is_valid_cluster(struct exfat_sb_info *sbi,
 		unsigned int clus)
 {
 	if (clus < EXFAT_FIRST_CLUSTER || sbi->num_clusters <= clus)
 		return false;
 	return true;
 }

 int exfat_ent_get(struct super_block *sb, unsigned int loc,
 		unsigned int *content)
 {
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 	int err;

 	if (!is_valid_cluster(sbi, loc)) {
 		exfat_fs_error(sb, "invalid access to FAT (entry 0x%08x)",
 			loc);
 		return -EIO;
 	}

 	err = __exfat_ent_get(sb, loc, content);
 	if (err) {
 		exfat_fs_error(sb,
 			"failed to access to FAT (entry 0x%08x, err:%d)",
 			loc, err);
 		return err;
 	}

 	if (*content == EXFAT_FREE_CLUSTER) {
 		exfat_fs_error(sb,
 			"invalid access to FAT free cluster (entry 0x%08x)",
 			loc);
 		return -EIO;
 	}

 	if (*content == EXFAT_BAD_CLUSTER) {
 		exfat_fs_error(sb,
 			"invalid access to FAT bad cluster (entry 0x%08x)",
 			loc);
 		return -EIO;
 	}

 	if (*content != EXFAT_EOF_CLUSTER && !is_valid_cluster(sbi, *content)) {
 		exfat_fs_error(sb,
 			"invalid access to FAT (entry 0x%08x) bogus content (0x%08x)",
 			loc, *content);
 		return -EIO;
 	}

 	return 0;
 }

 int exfat_chain_cont_cluster(struct super_block *sb, unsigned int chain,
 		unsigned int len)
 {
 	if (!len)
 		return 0;

 	while (len > 1) {
 		if (exfat_ent_set(sb, chain, chain + 1))
 			return -EIO;
 		chain++;
 		len--;
 	}

 	if (exfat_ent_set(sb, chain, EXFAT_EOF_CLUSTER))
 		return -EIO;
 	return 0;
 }

 /* This function must be called with bitmap_lock held */
 static int __exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain)
 {
 	struct super_block *sb = inode->i_sb;
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 	int cur_cmap_i, next_cmap_i;
 	unsigned int num_clusters = 0;
 	unsigned int clu;

 	/* invalid cluster number */
 	if (p_chain->dir == EXFAT_FREE_CLUSTER ||
 	    p_chain->dir == EXFAT_EOF_CLUSTER ||
 	    p_chain->dir < EXFAT_FIRST_CLUSTER)
 		return 0;

 	/* no cluster to truncate */
 	if (p_chain->size == 0)
 		return 0;

 	/* check cluster validation */
 	if (!is_valid_cluster(sbi, p_chain->dir)) {
 		exfat_err(sb, "invalid start cluster (%u)", p_chain->dir);
 		return -EIO;
 	}

 	clu = p_chain->dir;

 	cur_cmap_i = next_cmap_i =
 		BITMAP_OFFSET_SECTOR_INDEX(sb, CLUSTER_TO_BITMAP_ENT(clu));

 	if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
 		unsigned int last_cluster = p_chain->dir + p_chain->size - 1;
 		do {
 			bool sync = false;

 			if (clu < last_cluster)
 				next_cmap_i =
 				  BITMAP_OFFSET_SECTOR_INDEX(sb, CLUSTER_TO_BITMAP_ENT(clu+1));

 			/* flush bitmap only if index would be changed or for last cluster */
 			if (clu == last_cluster || cur_cmap_i != next_cmap_i) {
 				sync = true;
 				cur_cmap_i = next_cmap_i;
 			}

 			exfat_clear_bitmap(inode, clu, (sync && IS_DIRSYNC(inode)));
 			clu++;
 			num_clusters++;
 		} while (num_clusters < p_chain->size);
 	} else {
 		do {
 			bool sync = false;
 			unsigned int n_clu = clu;
 			int err = exfat_get_next_cluster(sb, &n_clu);

 			if (err || n_clu == EXFAT_EOF_CLUSTER)
 				sync = true;
 			else
 				next_cmap_i =
 				  BITMAP_OFFSET_SECTOR_INDEX(sb, CLUSTER_TO_BITMAP_ENT(n_clu));

 			if (cur_cmap_i != next_cmap_i) {
 				sync = true;
 				cur_cmap_i = next_cmap_i;
 			}

 			exfat_clear_bitmap(inode, clu, (sync && IS_DIRSYNC(inode)));
 			clu = n_clu;
 			num_clusters++;

 			if (err)
 				goto dec_used_clus;
 		} while (clu != EXFAT_EOF_CLUSTER);
 	}

 dec_used_clus:
 	sbi->used_clusters -= num_clusters;
 	return 0;
 }

 int exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain)
 {
 	int ret = 0;

 	mutex_lock(&EXFAT_SB(inode->i_sb)->bitmap_lock);
 	ret = __exfat_free_cluster(inode, p_chain);
 	mutex_unlock(&EXFAT_SB(inode->i_sb)->bitmap_lock);

 	return ret;
 }

 int exfat_find_last_cluster(struct super_block *sb, struct exfat_chain *p_chain,
 		unsigned int *ret_clu)
 {
 	unsigned int clu, next;
 	unsigned int count = 0;

 	next = p_chain->dir;
 	if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
 		*ret_clu = next + p_chain->size - 1;
 		return 0;
 	}

 	do {
 		count++;
 		clu = next;
 		if (exfat_ent_get(sb, clu, &next))
 			return -EIO;
 	} while (next != EXFAT_EOF_CLUSTER);

 	if (p_chain->size != count) {
 		exfat_fs_error(sb,
 			"bogus directory size (clus : ondisk(%d) != counted(%d))",
 			p_chain->size, count);
 		return -EIO;
 	}

 	*ret_clu = clu;
 	return 0;
 }

 int exfat_zeroed_cluster(struct inode *dir, unsigned int clu)
 {
 	struct super_block *sb = dir->i_sb;
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
 	int nr_bhs = MAX_BUF_PER_PAGE;
 	sector_t blknr, last_blknr;
 	int err, i, n;

 	blknr = exfat_cluster_to_sector(sbi, clu);
 	last_blknr = blknr + sbi->sect_per_clus;

 	if (last_blknr > sbi->num_sectors && sbi->num_sectors > 0) {
 		exfat_fs_error_ratelimit(sb,
 			"%s: out of range(sect:%llu len:%u)",
 			__func__, (unsigned long long)blknr,
 			sbi->sect_per_clus);
 		return -EIO;
 	}

 	/* Zeroing the unused blocks on this cluster */
 	while (blknr < last_blknr) {
 		for (n = 0; n < nr_bhs && blknr < last_blknr; n++, blknr++) {
 			bhs[n] = sb_getblk(sb, blknr);
 			if (!bhs[n]) {
 				err = -ENOMEM;
 				goto release_bhs;
 			}
 			memset(bhs[n]->b_data, 0, sb->s_blocksize);
 		}

 		err = exfat_update_bhs(bhs, n, IS_DIRSYNC(dir));
 		if (err)
 			goto release_bhs;

 		for (i = 0; i < n; i++)
 			brelse(bhs[i]);
 	}
 	return 0;

 release_bhs:
 	exfat_err(sb, "failed zeroed sect %llu\n", (unsigned long long)blknr);
 	for (i = 0; i < n; i++)
 		bforget(bhs[i]);
 	return err;
 }

 int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,
 		struct exfat_chain *p_chain, bool sync_bmap)
 {
 	int ret = -ENOSPC;
 	unsigned int num_clusters = 0, total_cnt;
 	unsigned int hint_clu, new_clu, last_clu = EXFAT_EOF_CLUSTER;
 	struct super_block *sb = inode->i_sb;
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);

 	total_cnt = EXFAT_DATA_CLUSTER_COUNT(sbi);

 	if (unlikely(total_cnt < sbi->used_clusters)) {
 		exfat_fs_error_ratelimit(sb,
 			"%s: invalid used clusters(t:%u,u:%u)\n",
 			__func__, total_cnt, sbi->used_clusters);
 		return -EIO;
 	}

 	if (num_alloc > total_cnt - sbi->used_clusters)
 		return -ENOSPC;

 	mutex_lock(&sbi->bitmap_lock);

 	hint_clu = p_chain->dir;
 	/* find new cluster */
 	if (hint_clu == EXFAT_EOF_CLUSTER) {
 		if (sbi->clu_srch_ptr < EXFAT_FIRST_CLUSTER) {
 			exfat_err(sb, "sbi->clu_srch_ptr is invalid (%u)\n",
 				  sbi->clu_srch_ptr);
 			sbi->clu_srch_ptr = EXFAT_FIRST_CLUSTER;
 		}

 		hint_clu = exfat_find_free_bitmap(sb, sbi->clu_srch_ptr);
 		if (hint_clu == EXFAT_EOF_CLUSTER) {
 			ret = -ENOSPC;
 			goto unlock;
 		}
 	}

 	/* check cluster validation */
 	if (!is_valid_cluster(sbi, hint_clu)) {
 		exfat_err(sb, "hint_cluster is invalid (%u)",
 			hint_clu);
 		hint_clu = EXFAT_FIRST_CLUSTER;
 		if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
 			if (exfat_chain_cont_cluster(sb, p_chain->dir,
 					num_clusters)) {
 				ret = -EIO;
 				goto unlock;
 			}
 			p_chain->flags = ALLOC_FAT_CHAIN;
 		}
 	}

 	p_chain->dir = EXFAT_EOF_CLUSTER;

 	while ((new_clu = exfat_find_free_bitmap(sb, hint_clu)) !=
 	       EXFAT_EOF_CLUSTER) {
 		if (new_clu != hint_clu &&
 		    p_chain->flags == ALLOC_NO_FAT_CHAIN) {
 			if (exfat_chain_cont_cluster(sb, p_chain->dir,
 					num_clusters)) {
 				ret = -EIO;
 				goto free_cluster;
 			}
 			p_chain->flags = ALLOC_FAT_CHAIN;
 		}

 		/* update allocation bitmap */
 		if (exfat_set_bitmap(inode, new_clu, sync_bmap)) {
 			ret = -EIO;
 			goto free_cluster;
 		}

 		num_clusters++;

 		/* update FAT table */
 		if (p_chain->flags == ALLOC_FAT_CHAIN) {
 			if (exfat_ent_set(sb, new_clu, EXFAT_EOF_CLUSTER)) {
 				ret = -EIO;
 				goto free_cluster;
 			}
 		}

 		if (p_chain->dir == EXFAT_EOF_CLUSTER) {
 			p_chain->dir = new_clu;
 		} else if (p_chain->flags == ALLOC_FAT_CHAIN) {
 			if (exfat_ent_set(sb, last_clu, new_clu)) {
 				ret = -EIO;
 				goto free_cluster;
 			}
 		}
 		last_clu = new_clu;

 		if (--num_alloc == 0) {
 			sbi->clu_srch_ptr = hint_clu;
 			sbi->used_clusters += num_clusters;

 			p_chain->size += num_clusters;
 			mutex_unlock(&sbi->bitmap_lock);
 			return 0;
 		}

 		hint_clu = new_clu + 1;
 		if (hint_clu >= sbi->num_clusters) {
 			hint_clu = EXFAT_FIRST_CLUSTER;

 			if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
 				if (exfat_chain_cont_cluster(sb, p_chain->dir,
 						num_clusters)) {
 					ret = -EIO;
 					goto free_cluster;
 				}
 				p_chain->flags = ALLOC_FAT_CHAIN;
 			}
 		}
 	}
 free_cluster:
 	if (num_clusters)
 		__exfat_free_cluster(inode, p_chain);
 unlock:
 	mutex_unlock(&sbi->bitmap_lock);
 	return ret;
 }

 int exfat_count_num_clusters(struct super_block *sb,
 		struct exfat_chain *p_chain, unsigned int *ret_count)
 {
 	unsigned int i, count;
 	unsigned int clu;
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);

 	if (!p_chain->dir || p_chain->dir == EXFAT_EOF_CLUSTER) {
 		*ret_count = 0;
 		return 0;
 	}

 	if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
 		*ret_count = p_chain->size;
 		return 0;
 	}

 	clu = p_chain->dir;
 	count = 0;
 	for (i = EXFAT_FIRST_CLUSTER; i < sbi->num_clusters; i++) {
 		count++;
 		if (exfat_ent_get(sb, clu, &clu))
 			return -EIO;
 		if (clu == EXFAT_EOF_CLUSTER)
 			break;
 	}

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

	#include <linux/slab.h>
	#include <asm/unaligned.h>
	#include <linux/buffer_head.h>

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

	static int exfat_mirror_bh(struct super_block *sb, sector_t sec,
	struct buffer_head *bh)
	{
	struct buffer_head *c_bh;
	struct exfat_sb_info *sbi = EXFAT_SB(sb);
	sector_t sec2;
	int err = 0;

	if (sbi->FAT2_start_sector != sbi->FAT1_start_sector) {
	sec2 = sec - sbi->FAT1_start_sector + sbi->FAT2_start_sector;
	c_bh = sb_getblk(sb, sec2);
	if (!c_bh)
	return -ENOMEM;
	memcpy(c_bh->b_data, bh->b_data, sb->s_blocksize);
	set_buffer_uptodate(c_bh);
	mark_buffer_dirty(c_bh);
	if (sb->s_flags & SB_SYNCHRONOUS)
	err = sync_dirty_buffer(c_bh);
	brelse(c_bh);
	}

	return err;
	}

	static int __exfat_ent_get(struct super_block *sb, unsigned int loc,
	unsigned int *content)
	{
	unsigned int off;
	sector_t sec;
	struct buffer_head *bh;

	sec = FAT_ENT_OFFSET_SECTOR(sb, loc);
	off = FAT_ENT_OFFSET_BYTE_IN_SECTOR(sb, loc);

	bh = sb_bread(sb, sec);
	if (!bh)
	return -EIO;

	content = le32_to_cpu((__le32 *)(&bh->b_data[off]));

	/* remap reserved clusters to simplify code */
	if (*content > EXFAT_BAD_CLUSTER)
	*content = EXFAT_EOF_CLUSTER;

	brelse(bh);
	return 0;
	}

	int exfat_ent_set(struct super_block *sb, unsigned int loc,
	unsigned int content)
	{
	unsigned int off;
	sector_t sec;
	__le32 *fat_entry;
	struct buffer_head *bh;

	sec = FAT_ENT_OFFSET_SECTOR(sb, loc);
	off = FAT_ENT_OFFSET_BYTE_IN_SECTOR(sb, loc);

	bh = sb_bread(sb, sec);
	if (!bh)
	return -EIO;

	fat_entry = (__le32 *)&(bh->b_data[off]);
	*fat_entry = cpu_to_le32(content);
	exfat_update_bh(bh, sb->s_flags & SB_SYNCHRONOUS);
	exfat_mirror_bh(sb, sec, bh);
	brelse(bh);
	return 0;
	}

	static inline bool is_valid_cluster(struct exfat_sb_info *sbi,
	unsigned int clus)
	{
	if (clus < EXFAT_FIRST_CLUSTER \|\| sbi->num_clusters <= clus)
	return false;
	return true;
	}

	int exfat_ent_get(struct super_block *sb, unsigned int loc,
	unsigned int *content)
	{
	struct exfat_sb_info *sbi = EXFAT_SB(sb);
	int err;

	if (!is_valid_cluster(sbi, loc)) {
	exfat_fs_error(sb, "invalid access to FAT (entry 0x%08x)",
	loc);
	return -EIO;
	}

	err = __exfat_ent_get(sb, loc, content);
	if (err) {
	exfat_fs_error(sb,
	"failed to access to FAT (entry 0x%08x, err:%d)",
	loc, err);
	return err;
	}

	if (*content == EXFAT_FREE_CLUSTER) {
	exfat_fs_error(sb,
	"invalid access to FAT free cluster (entry 0x%08x)",
	loc);
	return -EIO;
	}

	if (*content == EXFAT_BAD_CLUSTER) {
	exfat_fs_error(sb,
	"invalid access to FAT bad cluster (entry 0x%08x)",
	loc);
	return -EIO;
	}

	if (content != EXFAT_EOF_CLUSTER && !is_valid_cluster(sbi, content)) {
	exfat_fs_error(sb,
	"invalid access to FAT (entry 0x%08x) bogus content (0x%08x)",
	loc, *content);
	return -EIO;
	}

	return 0;
	}

	int exfat_chain_cont_cluster(struct super_block *sb, unsigned int chain,
	unsigned int len)
	{
	if (!len)
	return 0;

	while (len > 1) {
	if (exfat_ent_set(sb, chain, chain + 1))
	return -EIO;
	chain++;
	len--;
	}

	if (exfat_ent_set(sb, chain, EXFAT_EOF_CLUSTER))
	return -EIO;
	return 0;
	}

	/* This function must be called with bitmap_lock held */
	static int __exfat_free_cluster(struct inode inode, struct exfat_chain p_chain)
	{
	struct super_block *sb = inode->i_sb;
	struct exfat_sb_info *sbi = EXFAT_SB(sb);
	int cur_cmap_i, next_cmap_i;
	unsigned int num_clusters = 0;
	unsigned int clu;

	/* invalid cluster number */
	if (p_chain->dir == EXFAT_FREE_CLUSTER \|\|
	p_chain->dir == EXFAT_EOF_CLUSTER \|\|
	p_chain->dir < EXFAT_FIRST_CLUSTER)
	return 0;

	/* no cluster to truncate */
	if (p_chain->size == 0)
	return 0;

	/* check cluster validation */
	if (!is_valid_cluster(sbi, p_chain->dir)) {
	exfat_err(sb, "invalid start cluster (%u)", p_chain->dir);
	return -EIO;
	}

	clu = p_chain->dir;

	cur_cmap_i = next_cmap_i =
	BITMAP_OFFSET_SECTOR_INDEX(sb, CLUSTER_TO_BITMAP_ENT(clu));

	if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
	unsigned int last_cluster = p_chain->dir + p_chain->size - 1;
	do {
	bool sync = false;

	if (clu < last_cluster)
	next_cmap_i =
	BITMAP_OFFSET_SECTOR_INDEX(sb, CLUSTER_TO_BITMAP_ENT(clu+1));

	/* flush bitmap only if index would be changed or for last cluster */
	if (clu == last_cluster \|\| cur_cmap_i != next_cmap_i) {
	sync = true;
	cur_cmap_i = next_cmap_i;
	}

	exfat_clear_bitmap(inode, clu, (sync && IS_DIRSYNC(inode)));
	clu++;
	num_clusters++;
	} while (num_clusters < p_chain->size);
	} else {
	do {
	bool sync = false;
	unsigned int n_clu = clu;
	int err = exfat_get_next_cluster(sb, &n_clu);

	if (err \|\| n_clu == EXFAT_EOF_CLUSTER)
	sync = true;
	else
	next_cmap_i =
	BITMAP_OFFSET_SECTOR_INDEX(sb, CLUSTER_TO_BITMAP_ENT(n_clu));

	if (cur_cmap_i != next_cmap_i) {
	sync = true;
	cur_cmap_i = next_cmap_i;
	}

	exfat_clear_bitmap(inode, clu, (sync && IS_DIRSYNC(inode)));
	clu = n_clu;
	num_clusters++;

	if (err)
	goto dec_used_clus;
	} while (clu != EXFAT_EOF_CLUSTER);
	}

	dec_used_clus:
	sbi->used_clusters -= num_clusters;
	return 0;
	}

	int exfat_free_cluster(struct inode inode, struct exfat_chain p_chain)
	{
	int ret = 0;

	mutex_lock(&EXFAT_SB(inode->i_sb)->bitmap_lock);
	ret = __exfat_free_cluster(inode, p_chain);
	mutex_unlock(&EXFAT_SB(inode->i_sb)->bitmap_lock);

	return ret;
	}

	int exfat_find_last_cluster(struct super_block sb, struct exfat_chain p_chain,
	unsigned int *ret_clu)
	{
	unsigned int clu, next;
	unsigned int count = 0;

	next = p_chain->dir;
	if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
	*ret_clu = next + p_chain->size - 1;
	return 0;
	}

	do {
	count++;
	clu = next;
	if (exfat_ent_get(sb, clu, &next))
	return -EIO;
	} while (next != EXFAT_EOF_CLUSTER);

	if (p_chain->size != count) {
	exfat_fs_error(sb,
	"bogus directory size (clus : ondisk(%d) != counted(%d))",
	p_chain->size, count);
	return -EIO;
	}

	*ret_clu = clu;
	return 0;
	}

	int exfat_zeroed_cluster(struct inode *dir, unsigned int clu)
	{
	struct super_block *sb = dir->i_sb;
	struct exfat_sb_info *sbi = EXFAT_SB(sb);
	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
	int nr_bhs = MAX_BUF_PER_PAGE;
	sector_t blknr, last_blknr;
	int err, i, n;

	blknr = exfat_cluster_to_sector(sbi, clu);
	last_blknr = blknr + sbi->sect_per_clus;

	if (last_blknr > sbi->num_sectors && sbi->num_sectors > 0) {
	exfat_fs_error_ratelimit(sb,
	"%s: out of range(sect:%llu len:%u)",
	__func__, (unsigned long long)blknr,
	sbi->sect_per_clus);
	return -EIO;
	}

	/* Zeroing the unused blocks on this cluster */
	while (blknr < last_blknr) {
	for (n = 0; n < nr_bhs && blknr < last_blknr; n++, blknr++) {
	bhs[n] = sb_getblk(sb, blknr);
	if (!bhs[n]) {
	err = -ENOMEM;
	goto release_bhs;
	}
	memset(bhs[n]->b_data, 0, sb->s_blocksize);
	}

	err = exfat_update_bhs(bhs, n, IS_DIRSYNC(dir));
	if (err)
	goto release_bhs;

	for (i = 0; i < n; i++)
	brelse(bhs[i]);
	}
	return 0;

	release_bhs:
	exfat_err(sb, "failed zeroed sect %llu\n", (unsigned long long)blknr);
	for (i = 0; i < n; i++)
	bforget(bhs[i]);
	return err;
	}

	int exfat_alloc_cluster(struct inode *inode, unsigned int num_alloc,
	struct exfat_chain *p_chain, bool sync_bmap)
	{
	int ret = -ENOSPC;
	unsigned int num_clusters = 0, total_cnt;
	unsigned int hint_clu, new_clu, last_clu = EXFAT_EOF_CLUSTER;
	struct super_block *sb = inode->i_sb;
	struct exfat_sb_info *sbi = EXFAT_SB(sb);

	total_cnt = EXFAT_DATA_CLUSTER_COUNT(sbi);

	if (unlikely(total_cnt < sbi->used_clusters)) {
	exfat_fs_error_ratelimit(sb,
	"%s: invalid used clusters(t:%u,u:%u)\n",
	__func__, total_cnt, sbi->used_clusters);
	return -EIO;
	}

	if (num_alloc > total_cnt - sbi->used_clusters)
	return -ENOSPC;

	mutex_lock(&sbi->bitmap_lock);

	hint_clu = p_chain->dir;
	/* find new cluster */
	if (hint_clu == EXFAT_EOF_CLUSTER) {
	if (sbi->clu_srch_ptr < EXFAT_FIRST_CLUSTER) {
	exfat_err(sb, "sbi->clu_srch_ptr is invalid (%u)\n",
	sbi->clu_srch_ptr);
	sbi->clu_srch_ptr = EXFAT_FIRST_CLUSTER;
	}

	hint_clu = exfat_find_free_bitmap(sb, sbi->clu_srch_ptr);
	if (hint_clu == EXFAT_EOF_CLUSTER) {
	ret = -ENOSPC;
	goto unlock;
	}
	}

	/* check cluster validation */
	if (!is_valid_cluster(sbi, hint_clu)) {
	exfat_err(sb, "hint_cluster is invalid (%u)",
	hint_clu);
	hint_clu = EXFAT_FIRST_CLUSTER;
	if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
	if (exfat_chain_cont_cluster(sb, p_chain->dir,
	num_clusters)) {
	ret = -EIO;
	goto unlock;
	}
	p_chain->flags = ALLOC_FAT_CHAIN;
	}
	}

	p_chain->dir = EXFAT_EOF_CLUSTER;

	while ((new_clu = exfat_find_free_bitmap(sb, hint_clu)) !=
	EXFAT_EOF_CLUSTER) {
	if (new_clu != hint_clu &&
	p_chain->flags == ALLOC_NO_FAT_CHAIN) {
	if (exfat_chain_cont_cluster(sb, p_chain->dir,
	num_clusters)) {
	ret = -EIO;
	goto free_cluster;
	}
	p_chain->flags = ALLOC_FAT_CHAIN;
	}

	/* update allocation bitmap */
	if (exfat_set_bitmap(inode, new_clu, sync_bmap)) {
	ret = -EIO;
	goto free_cluster;
	}

	num_clusters++;

	/* update FAT table */
	if (p_chain->flags == ALLOC_FAT_CHAIN) {
	if (exfat_ent_set(sb, new_clu, EXFAT_EOF_CLUSTER)) {
	ret = -EIO;
	goto free_cluster;
	}
	}

	if (p_chain->dir == EXFAT_EOF_CLUSTER) {
	p_chain->dir = new_clu;
	} else if (p_chain->flags == ALLOC_FAT_CHAIN) {
	if (exfat_ent_set(sb, last_clu, new_clu)) {
	ret = -EIO;
	goto free_cluster;
	}
	}
	last_clu = new_clu;

	if (--num_alloc == 0) {
	sbi->clu_srch_ptr = hint_clu;
	sbi->used_clusters += num_clusters;

	p_chain->size += num_clusters;
	mutex_unlock(&sbi->bitmap_lock);
	return 0;
	}

	hint_clu = new_clu + 1;
	if (hint_clu >= sbi->num_clusters) {
	hint_clu = EXFAT_FIRST_CLUSTER;

	if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
	if (exfat_chain_cont_cluster(sb, p_chain->dir,
	num_clusters)) {
	ret = -EIO;
	goto free_cluster;
	}
	p_chain->flags = ALLOC_FAT_CHAIN;
	}
	}
	}
	free_cluster:
	if (num_clusters)
	__exfat_free_cluster(inode, p_chain);
	unlock:
	mutex_unlock(&sbi->bitmap_lock);
	return ret;
	}

	int exfat_count_num_clusters(struct super_block *sb,
	struct exfat_chain p_chain, unsigned int ret_count)
	{
	unsigned int i, count;
	unsigned int clu;
	struct exfat_sb_info *sbi = EXFAT_SB(sb);

	if (!p_chain->dir \|\| p_chain->dir == EXFAT_EOF_CLUSTER) {
	*ret_count = 0;
	return 0;
	}

	if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
	*ret_count = p_chain->size;
	return 0;
	}

	clu = p_chain->dir;
	count = 0;
	for (i = EXFAT_FIRST_CLUSTER; i < sbi->num_clusters; i++) {
	count++;
	if (exfat_ent_get(sb, clu, &clu))
	return -EIO;
	if (clu == EXFAT_EOF_CLUSTER)
	break;
	}

	*ret_count = count;
	return 0;
	}