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Switch btrfs_name_hash() to crc32c

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Date: Tue, 19 Aug 2008 19:21:57 +0100
Using a 64-bit hash as the readdir cookie is just asking for trouble.
And gets it, when we try to export the file system by NFS.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
David Woodhouse 2008-08-19 19:21:57 +01:00 committed by Chris Mason
parent 76fcef19c4
commit 615f996fb8
3 changed files with 7 additions and 114 deletions
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2
fs/btrfs/Makefile
View file

@ -3,7 +3,7 @@ ifneq ($(KERNELRELEASE),)
obj-m := btrfs.o
btrfs-y := super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
hash.o file-item.o inode-item.o inode-map.o disk-io.o \
file-item.o inode-item.o inode-map.o disk-io.o \
transaction.o bit-radix.o inode.o file.o tree-defrag.o \
extent_map.o sysfs.o struct-funcs.o xattr.o ordered-data.o \
extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \

112
fs/btrfs/hash.c
View file

@ -1,112 +0,0 @@
/*
* Copyright (C) 2007 Oracle. All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License v2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*/
/*
* Original copy from:
* linux/fs/ext3/hash.c
*
* Copyright (C) 2002 by Theodore Ts'o
*
* This file is released under the GPL v2.
*
* This file may be redistributed under the terms of the GNU Public
* License.
*/
#include <linux/types.h>
#include "hash.h"
#define DELTA 0x9E3779B9
static void TEA_transform(__u32 buf[2], __u32 const in[])
{
__u32 sum = 0;
__u32 b0 = buf[0], b1 = buf[1];
__u32 a = in[0], b = in[1], c = in[2], d = in[3];
int n = 16;
do {
sum += DELTA;
b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
} while(--n);
buf[0] += b0;
buf[1] += b1;
}
static void str2hashbuf(const char *msg, int len, __u32 *buf, int num)
{
__u32 pad, val;
int i;
pad = (__u32)len | ((__u32)len << 8);
pad |= pad << 16;
val = pad;
if (len > num*4)
len = num * 4;
for (i=0; i < len; i++) {
if ((i % 4) == 0)
val = pad;
val = msg[i] + (val << 8);
if ((i % 4) == 3) {
*buf++ = val;
val = pad;
num--;
}
}
if (--num >= 0)
*buf++ = val;
while (--num >= 0)
*buf++ = pad;
}
u64 btrfs_name_hash(const char *name, int len)
{
__u32 hash;
__u32 minor_hash = 0;
const char *p;
__u32 in[8], buf[4];
u64 hash_result;
if (len == 1 && *name == '.') {
return 1;
} else if (len == 2 && name[0] == '.' && name[1] == '.') {
return 2;
}
/* Initialize the default seed for the hash checksum functions */
buf[0] = 0x67452301;
buf[1] = 0xefcdab89;
buf[2] = 0x98badcfe;
buf[3] = 0x10325476;
p = name;
while (len > 0) {
str2hashbuf(p, len, in, 4);
TEA_transform(buf, in);
len -= 16;
p += 16;
}
hash = buf[0];
minor_hash = buf[1];
hash_result = buf[0];
hash_result <<= 32;
hash_result |= buf[1];
return hash_result;
}

7
fs/btrfs/hash.h
View file

@ -18,5 +18,10 @@
#ifndef __HASH__
#define __HASH__
u64 btrfs_name_hash(const char *name, int len);
#include "crc32c.h"
static inline u64 btrfs_name_hash(const char *name, int len)
{
return btrfs_crc32c((u32)~1, name, len);
}
#endif