diff --git a/fs/fat/dir.c b/fs/fat/dir.c
index 895049b2ac9cb65fd58af857e719bc7d8d03115e..204d8614406f9cd18efe2f660ebb1142e66d01f5 100644
--- a/fs/fat/dir.c
+++ b/fs/fat/dir.c
@@ -263,7 +263,6 @@ int fat_search_long(struct inode *inode, const unsigned char *name,
 			unsigned char id;
 			unsigned char slot;
 			unsigned char slots;
-			unsigned char sum;
 			unsigned char alias_checksum;
 
 			if (!unicode) {
@@ -317,9 +316,7 @@ int fat_search_long(struct inode *inode, const unsigned char *name,
 				goto parse_long;
 			if (IS_FREE(de->name) || (de->attr & ATTR_VOLUME))
 				continue;
-			for (sum = 0, i = 0; i < 11; i++)
-				sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + de->name[i];
-			if (sum != alias_checksum)
+			if (fat_checksum(de->name) != alias_checksum)
 				nr_slots = 0;
 		}
 
@@ -479,7 +476,6 @@ static int fat_readdirx(struct inode *inode, struct file *filp, void *dirent,
 		unsigned char id;
 		unsigned char slot;
 		unsigned char slots;
-		unsigned char sum;
 		unsigned char alias_checksum;
 
 		if (!unicode) {
@@ -534,9 +530,7 @@ static int fat_readdirx(struct inode *inode, struct file *filp, void *dirent,
 			goto ParseLong;
 		if (IS_FREE(de->name) || (de->attr & ATTR_VOLUME))
 			goto RecEnd;
-		for (sum = 0, i = 0; i < 11; i++)
-			sum = (((sum&1)<<7)|((sum&0xfe)>>1)) + de->name[i];
-		if (sum != alias_checksum)
+		if (fat_checksum(de->name) != alias_checksum)
 			long_slots = 0;
 	}
 
diff --git a/fs/vfat/namei.c b/fs/vfat/namei.c
index 1c6f6b57ef1cfcd29f7931ef41a11f23632e41b7..467346b123d9ed8c4ca567e062255af7ba85741b 100644
--- a/fs/vfat/namei.c
+++ b/fs/vfat/namei.c
@@ -621,8 +621,7 @@ static int vfat_build_slots(struct inode *dir, const unsigned char *name,
 	}
 
 	/* build the entry of long file name */
-	for (cksum = i = 0; i < 11; i++)
-		cksum = (((cksum&1)<<7)|((cksum&0xfe)>>1)) + msdos_name[i];
+	cksum = fat_checksum(msdos_name);
 
 	*nr_slots = usize / 13;
 	for (ps = slots, i = *nr_slots; i > 0; i--, ps++) {
diff --git a/include/linux/msdos_fs.h b/include/linux/msdos_fs.h
index 9a3d2725798439e2a745bca4f564f89228e77ae3..941da5c016a01e1434d3291fe1ec466c16adbb45 100644
--- a/include/linux/msdos_fs.h
+++ b/include/linux/msdos_fs.h
@@ -282,6 +282,17 @@ static inline u8 fat_attr(struct inode *inode)
 		MSDOS_I(inode)->i_attrs;
 }
 
+static inline unsigned char fat_checksum(const __u8 *name)
+{
+	unsigned char s = name[0];
+	s = (s<<7) + (s>>1) + name[1];	s = (s<<7) + (s>>1) + name[2];
+	s = (s<<7) + (s>>1) + name[3];	s = (s<<7) + (s>>1) + name[4];
+	s = (s<<7) + (s>>1) + name[5];	s = (s<<7) + (s>>1) + name[6];
+	s = (s<<7) + (s>>1) + name[7];	s = (s<<7) + (s>>1) + name[8];
+	s = (s<<7) + (s>>1) + name[9];	s = (s<<7) + (s>>1) + name[10];
+	return s;
+}
+
 static inline sector_t fat_clus_to_blknr(struct msdos_sb_info *sbi, int clus)
 {
 	return ((sector_t)clus - FAT_START_ENT) * sbi->sec_per_clus