Switch btrfs_name_hash() to crc32c

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>

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index 75f8818..8213bba 100644 (file)
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -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 \

diff --git a/fs/btrfs/hash.c b/fs/btrfs/hash.c
deleted file mode 100644 (file)
index 21037cf..0000000
--- a/fs/btrfs/hash.c
+++ /dev/null
@@ -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;
-}

diff --git a/fs/btrfs/hash.h b/fs/btrfs/hash.h
index 868ee17..2a020b2 100644 (file)
--- a/fs/btrfs/hash.h
+++ b/fs/btrfs/hash.h
@@ -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