fat: improve fat_hash()

fat_hash() is using the algorithm known as bad. Instead of it, this
uses hash_32(). The following is the summary of test.

old hash:
	hash func (1000 times): 33489 cycles
	total inodes in hash table: 70926
	largest bucket contains: 696
	smallest bucket contains: 54

new hash:
	hash func (1000 times): 33129 cycles
	total inodes in hash table: 70926
	largest bucket contains: 315
	smallest bucket contains: 236

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 1 deletions

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index a2a570f81719..2b8e94c3eef4 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -43,7 +43,6 @@ struct fat_mount_options {
 
 #define FAT_HASH_BITS   8
 #define FAT_HASH_SIZE   (1UL << FAT_HASH_BITS)
-#define FAT_HASH_MASK   (FAT_HASH_SIZE-1)
 
 /*
  * MS-DOS file system in-core superblock data