diff --git a/fs/exfat/balloc.c b/fs/exfat/balloc.c
index a987919..761c79c 100644
--- a/fs/exfat/balloc.c
+++ b/fs/exfat/balloc.c
@@ -166,7 +166,7 @@
  * 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)
+void exfat_clear_bitmap(struct inode *inode, unsigned int clu, bool sync)
 {
 	int i, b;
 	unsigned int ent_idx;
@@ -180,7 +180,7 @@
 	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));
+	exfat_update_bh(sbi->vol_amap[i], sync);
 
 	if (opts->discard) {
 		int ret_discard;
diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index b8f0e829..764bc64 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -408,7 +408,7 @@
 int exfat_load_bitmap(struct super_block *sb);
 void exfat_free_bitmap(struct exfat_sb_info *sbi);
 int exfat_set_bitmap(struct inode *inode, unsigned int clu);
-void exfat_clear_bitmap(struct inode *inode, unsigned int clu);
+void exfat_clear_bitmap(struct inode *inode, unsigned int clu, bool sync);
 unsigned int exfat_find_free_bitmap(struct super_block *sb, unsigned int clu);
 int exfat_count_used_clusters(struct super_block *sb, unsigned int *ret_count);
 
diff --git a/fs/exfat/exfat_raw.h b/fs/exfat/exfat_raw.h
index 6aec628..7f39b1c 100644
--- a/fs/exfat/exfat_raw.h
+++ b/fs/exfat/exfat_raw.h
@@ -77,6 +77,10 @@
 
 #define EXFAT_FILE_NAME_LEN		15
 
+#define EXFAT_MIN_SECT_SIZE_BITS		9
+#define EXFAT_MAX_SECT_SIZE_BITS		12
+#define EXFAT_MAX_SECT_PER_CLUS_BITS(x)		(25 - (x)->sect_size_bits)
+
 /* EXFAT: Main and Backup Boot Sector (512 bytes) */
 struct boot_sector {
 	__u8	jmp_boot[BOOTSEC_JUMP_BOOT_LEN];
diff --git a/fs/exfat/fatent.c b/fs/exfat/fatent.c
index c3c9afe..7b2e8af 100644
--- a/fs/exfat/fatent.c
+++ b/fs/exfat/fatent.c
@@ -157,6 +157,7 @@
 	unsigned int clu;
 	struct super_block *sb = inode->i_sb;
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+	int cur_cmap_i, next_cmap_i;
 
 	/* invalid cluster number */
 	if (p_chain->dir == EXFAT_FREE_CLUSTER ||
@@ -176,21 +177,51 @@
 
 	clu = p_chain->dir;
 
-	if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
-		do {
-			exfat_clear_bitmap(inode, clu);
-			clu++;
+	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 {
-			exfat_clear_bitmap(inode, clu);
+			bool sync = false;
+			unsigned int n_clu = clu;
+			int err = exfat_get_next_cluster(sb, &n_clu);
 
-			if (exfat_get_next_cluster(sb, &clu))
-				goto dec_used_clus;
+			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);
 	}
 
diff --git a/fs/exfat/super.c b/fs/exfat/super.c
index 87be5bf..c6d8d2e 100644
--- a/fs/exfat/super.c
+++ b/fs/exfat/super.c
@@ -381,8 +381,7 @@
 {
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 
-	if (!is_power_of_2(logical_sect) ||
-	    logical_sect < 512 || logical_sect > 4096) {
+	if (!is_power_of_2(logical_sect)) {
 		exfat_err(sb, "bogus logical sector size %u", logical_sect);
 		return -EIO;
 	}
@@ -451,6 +450,25 @@
 		return -EINVAL;
 	}
 
+	/*
+	 * sect_size_bits could be at least 9 and at most 12.
+	 */
+	if (p_boot->sect_size_bits < EXFAT_MIN_SECT_SIZE_BITS ||
+	    p_boot->sect_size_bits > EXFAT_MAX_SECT_SIZE_BITS) {
+		exfat_err(sb, "bogus sector size bits : %u\n",
+				p_boot->sect_size_bits);
+		return -EINVAL;
+	}
+
+	/*
+	 * sect_per_clus_bits could be at least 0 and at most 25 - sect_size_bits.
+	 */
+	if (p_boot->sect_per_clus_bits > EXFAT_MAX_SECT_PER_CLUS_BITS(p_boot)) {
+		exfat_err(sb, "bogus sectors bits per cluster : %u\n",
+				p_boot->sect_per_clus_bits);
+		return -EINVAL;
+	}
+
 	sbi->sect_per_clus = 1 << p_boot->sect_per_clus_bits;
 	sbi->sect_per_clus_bits = p_boot->sect_per_clus_bits;
 	sbi->cluster_size_bits = p_boot->sect_per_clus_bits +
@@ -477,16 +495,19 @@
 	sbi->used_clusters = EXFAT_CLUSTERS_UNTRACKED;
 
 	/* check consistencies */
-	if (sbi->num_FAT_sectors << p_boot->sect_size_bits <
-	    sbi->num_clusters * 4) {
+	if ((u64)sbi->num_FAT_sectors << p_boot->sect_size_bits <
+	    (u64)sbi->num_clusters * 4) {
 		exfat_err(sb, "bogus fat length");
 		return -EINVAL;
 	}
+
 	if (sbi->data_start_sector <
-	    sbi->FAT1_start_sector + sbi->num_FAT_sectors * p_boot->num_fats) {
+	    (u64)sbi->FAT1_start_sector +
+	    (u64)sbi->num_FAT_sectors * p_boot->num_fats) {
 		exfat_err(sb, "bogus data start sector");
 		return -EINVAL;
 	}
+
 	if (sbi->vol_flags & VOLUME_DIRTY)
 		exfat_warn(sb, "Volume was not properly unmounted. Some data may be corrupt. Please run fsck.");
 	if (sbi->vol_flags & MEDIA_FAILURE)