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authorOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>2008-11-06 12:53:49 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2008-11-06 15:41:20 -0800
commitd3dfa8228f87ab9960ab8b4718013d68e3c25a43 (patch)
tree236784875a5c735688e644fe8412649e5fdbfcd7
parent52e9d9f4b32a3bec91feb76c84e37b7dcffe5040 (diff)
downloadlinux-2.6.38-lt-ux500-d3dfa8228f87ab9960ab8b4718013d68e3c25a43.tar.gz
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>
-rw-r--r--fs/fat/fat.h1
-rw-r--r--fs/fat/inode.c18
2 files changed, 7 insertions, 12 deletions
diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index a2a570f8171..2b8e94c3eef 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
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 079d9d5e0d3..f58cd48d98b 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -26,6 +26,7 @@
#include <linux/uio.h>
#include <linux/writeback.h>
#include <linux/log2.h>
+#include <linux/hash.h>
#include <asm/unaligned.h>
#include "fat.h"
@@ -247,25 +248,21 @@ static void fat_hash_init(struct super_block *sb)
INIT_HLIST_HEAD(&sbi->inode_hashtable[i]);
}
-static inline unsigned long fat_hash(struct super_block *sb, loff_t i_pos)
+static inline unsigned long fat_hash(loff_t i_pos)
{
- unsigned long tmp = (unsigned long)i_pos | (unsigned long) sb;
- tmp = tmp + (tmp >> FAT_HASH_BITS) + (tmp >> FAT_HASH_BITS * 2);
- return tmp & FAT_HASH_MASK;
+ return hash_32(i_pos, FAT_HASH_BITS);
}
void fat_attach(struct inode *inode, loff_t i_pos)
{
- struct super_block *sb = inode->i_sb;
- struct msdos_sb_info *sbi = MSDOS_SB(sb);
+ struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+ struct hlist_head *head = sbi->inode_hashtable + fat_hash(i_pos);
spin_lock(&sbi->inode_hash_lock);
MSDOS_I(inode)->i_pos = i_pos;
- hlist_add_head(&MSDOS_I(inode)->i_fat_hash,
- sbi->inode_hashtable + fat_hash(sb, i_pos));
+ hlist_add_head(&MSDOS_I(inode)->i_fat_hash, head);
spin_unlock(&sbi->inode_hash_lock);
}
-
EXPORT_SYMBOL_GPL(fat_attach);
void fat_detach(struct inode *inode)
@@ -276,13 +273,12 @@ void fat_detach(struct inode *inode)
hlist_del_init(&MSDOS_I(inode)->i_fat_hash);
spin_unlock(&sbi->inode_hash_lock);
}
-
EXPORT_SYMBOL_GPL(fat_detach);
struct inode *fat_iget(struct super_block *sb, loff_t i_pos)
{
struct msdos_sb_info *sbi = MSDOS_SB(sb);
- struct hlist_head *head = sbi->inode_hashtable + fat_hash(sb, i_pos);
+ struct hlist_head *head = sbi->inode_hashtable + fat_hash(i_pos);
struct hlist_node *_p;
struct msdos_inode_info *i;
struct inode *inode = NULL;