diff --git a/fs/exfat/fatent.c b/fs/exfat/fatent.c
new file mode 100644
index 000000000000..aa688ae4db41
--- /dev/null
+++ b/fs/exfat/fatent.c
@@ -0,0 +1,472 @@
+// 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_ent_get(struct super_block *sb, unsigned int loc,
+		unsigned int *content)
+{
+	unsigned int off, _content;
+	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 >= CLUSTER_32(0xFFFFFFF8))
+		_content = EXFAT_EOF_CLUSTER;
+
+	*content = CLUSTER_32(_content);
+	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(sb, bh, sb->s_flags & SB_SYNCHRONOUS);
+	exfat_mirror_bh(sb, sec, bh);
+	brelse(bh);
+	return 0;
+}
+
+static inline bool is_reserved_cluster(unsigned int clus)
+{
+	if (clus == EXFAT_FREE_CLUSTER || clus == EXFAT_EOF_CLUSTER ||
+	    clus == EXFAT_BAD_CLUSTER)
+		return true;
+	return false;
+}
+
+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 (!is_reserved_cluster(*content) &&
+			!is_valid_cluster(sbi, *content)) {
+		exfat_fs_error(sb,
+			"invalid access to FAT (entry 0x%08x) bogus content (0x%08x)",
+			loc, *content);
+		return -EIO;
+	}
+
+	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;
+	}
+	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;
+}
+
+int exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain)
+{
+	unsigned int num_clusters = 0;
+	unsigned int clu;
+	struct super_block *sb = inode->i_sb;
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+
+	/* 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 (p_chain->dir < 2 && p_chain->dir >= sbi->num_clusters) {
+		exfat_msg(sb, KERN_ERR, "invalid start cluster (%u)",
+				p_chain->dir);
+		return -EIO;
+	}
+
+	set_bit(EXFAT_SB_DIRTY, &sbi->s_state);
+	clu = p_chain->dir;
+
+	if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
+		do {
+			exfat_clear_bitmap(inode, clu);
+			clu++;
+
+			num_clusters++;
+		} while (num_clusters < p_chain->size);
+	} else {
+		do {
+			exfat_clear_bitmap(inode, clu);
+
+			if (exfat_get_next_cluster(sb, &clu))
+				goto dec_used_clus;
+
+			num_clusters++;
+		} while (clu != EXFAT_EOF_CLUSTER);
+	}
+
+dec_used_clus:
+	sbi->used_clusters -= num_clusters;
+	return 0;
+}
+
+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;
+}
+
+static inline int exfat_sync_bhs(struct buffer_head **bhs, int nr_bhs)
+{
+	int i, err = 0;
+
+	for (i = 0; i < nr_bhs; i++)
+		write_dirty_buffer(bhs[i], 0);
+
+	for (i = 0; i < nr_bhs; i++) {
+		wait_on_buffer(bhs[i]);
+		if (!err && !buffer_uptodate(bhs[i]))
+			err = -EIO;
+	}
+	return err;
+}
+
+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 */
+	n = 0;
+	while (blknr < last_blknr) {
+		bhs[n] = sb_getblk(sb, blknr);
+		if (!bhs[n]) {
+			err = -ENOMEM;
+			goto release_bhs;
+		}
+		memset(bhs[n]->b_data, 0, sb->s_blocksize);
+		exfat_update_bh(sb, bhs[n], 0);
+
+		n++;
+		blknr++;
+
+		if (n == nr_bhs) {
+			if (IS_DIRSYNC(dir)) {
+				err = exfat_sync_bhs(bhs, n);
+				if (err)
+					goto release_bhs;
+			}
+
+			for (i = 0; i < n; i++)
+				brelse(bhs[i]);
+			n = 0;
+		}
+	}
+
+	if (IS_DIRSYNC(dir)) {
+		err = exfat_sync_bhs(bhs, n);
+		if (err)
+			goto release_bhs;
+	}
+
+	for (i = 0; i < n; i++)
+		brelse(bhs[i]);
+
+	return 0;
+
+release_bhs:
+	exfat_msg(sb, KERN_ERR, "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)
+{
+	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;
+
+	hint_clu = p_chain->dir;
+	/* find new cluster */
+	if (hint_clu == EXFAT_EOF_CLUSTER) {
+		if (sbi->clu_srch_ptr < EXFAT_FIRST_CLUSTER) {
+			exfat_msg(sb, KERN_ERR,
+				"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)
+			return -ENOSPC;
+	}
+
+	/* check cluster validation */
+	if (hint_clu < EXFAT_FIRST_CLUSTER && hint_clu >= sbi->num_clusters) {
+		exfat_msg(sb, KERN_ERR, "hint_cluster is invalid (%u)\n",
+			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))
+				return -EIO;
+			p_chain->flags = ALLOC_FAT_CHAIN;
+		}
+	}
+
+	set_bit(EXFAT_SB_DIRTY, &sbi->s_state);
+
+	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)) {
+			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;
+			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);
+	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;
+}
+
+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;
+}
