[patch 15/39] ext4: Add support for non-native signed/unsignedhtree hash algorithms

From: Greg KH
Date: Wed Feb 18 2009 - 16:41:09 EST

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2.6.28-stable review patch. If anyone has any objections, please let us know.

------------------

From: "Theodore Ts'o" <tytso@xxxxxxx>

(cherry picked from commit f99b25897a86fcfff9140396a97261ae65fed872)

The original ext3 hash algorithms assumed that variables of type char
were signed, as God and K&R intended. Unfortunately, this assumption
is not true on some architectures. Userspace support for marking
filesystems with non-native signed/unsigned chars was added two years
ago, but the kernel-side support was never added (until now).

Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
fs/ext4/ext4.h | 3 ++
fs/ext4/ext4_sb.h | 1
fs/ext4/hash.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++--------
fs/ext4/namei.c | 7 ++++
fs/ext4/super.c | 12 ++++++++
5 files changed, 90 insertions(+), 10 deletions(-)

--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -891,6 +891,9 @@ static inline __le16 ext4_rec_len_to_dis
#define DX_HASH_LEGACY 0
#define DX_HASH_HALF_MD4 1
#define DX_HASH_TEA 2
+#define DX_HASH_LEGACY_UNSIGNED 3
+#define DX_HASH_HALF_MD4_UNSIGNED 4
+#define DX_HASH_TEA_UNSIGNED 5

#ifdef __KERNEL__

--- a/fs/ext4/ext4_sb.h
+++ b/fs/ext4/ext4_sb.h
@@ -57,6 +57,7 @@ struct ext4_sb_info {
u32 s_next_generation;
u32 s_hash_seed[4];
int s_def_hash_version;
+ int s_hash_unsigned; /* 3 if hash should be signed, 0 if not */
struct percpu_counter s_freeblocks_counter;
struct percpu_counter s_freeinodes_counter;
struct percpu_counter s_dirs_counter;
--- a/fs/ext4/hash.c
+++ b/fs/ext4/hash.c
@@ -35,23 +35,71 @@ static void TEA_transform(__u32 buf[4],

/* The old legacy hash */
-static __u32 dx_hack_hash(const char *name, int len)
+static __u32 dx_hack_hash_unsigned(const char *name, int len)
{
- __u32 hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
+ __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
+ const unsigned char *ucp = (const unsigned char *) name;
+
+ while (len--) {
+ hash = hash1 + (hash0 ^ (((int) *ucp++) * 7152373));
+
+ if (hash & 0x80000000)
+ hash -= 0x7fffffff;
+ hash1 = hash0;
+ hash0 = hash;
+ }
+ return hash0 << 1;
+}
+
+static __u32 dx_hack_hash_signed(const char *name, int len)
+{
+ __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
+ const signed char *scp = (const signed char *) name;
+
while (len--) {
- __u32 hash = hash1 + (hash0 ^ (*name++ * 7152373));
+ hash = hash1 + (hash0 ^ (((int) *scp++) * 7152373));

- if (hash & 0x80000000) hash -= 0x7fffffff;
+ if (hash & 0x80000000)
+ hash -= 0x7fffffff;
hash1 = hash0;
hash0 = hash;
}
- return (hash0 << 1);
+ return hash0 << 1;
+}
+
+static void str2hashbuf_signed(const char *msg, int len, __u32 *buf, int num)
+{
+ __u32 pad, val;
+ int i;
+ const signed char *scp = (const signed char *) msg;
+
+ 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 = ((int) scp[i]) + (val << 8);
+ if ((i % 4) == 3) {
+ *buf++ = val;
+ val = pad;
+ num--;
+ }
+ }
+ if (--num >= 0)
+ *buf++ = val;
+ while (--num >= 0)
+ *buf++ = pad;
}

-static void str2hashbuf(const char *msg, int len, __u32 *buf, int num)
+static void str2hashbuf_unsigned(const char *msg, int len, __u32 *buf, int num)
{
__u32 pad, val;
int i;
+ const unsigned char *ucp = (const unsigned char *) msg;

pad = (__u32)len | ((__u32)len << 8);
pad |= pad << 16;
@@ -62,7 +110,7 @@ static void str2hashbuf(const char *msg,
for (i = 0; i < len; i++) {
if ((i % 4) == 0)
val = pad;
- val = msg[i] + (val << 8);
+ val = ((int) ucp[i]) + (val << 8);
if ((i % 4) == 3) {
*buf++ = val;
val = pad;
@@ -95,6 +143,8 @@ int ext4fs_dirhash(const char *name, int
const char *p;
int i;
__u32 in[8], buf[4];
+ void (*str2hashbuf)(const char *, int, __u32 *, int) =
+ str2hashbuf_signed;

/* Initialize the default seed for the hash checksum functions */
buf[0] = 0x67452301;
@@ -113,13 +163,18 @@ int ext4fs_dirhash(const char *name, int
}

switch (hinfo->hash_version) {
+ case DX_HASH_LEGACY_UNSIGNED:
+ hash = dx_hack_hash_unsigned(name, len);
+ break;
case DX_HASH_LEGACY:
- hash = dx_hack_hash(name, len);
+ hash = dx_hack_hash_signed(name, len);
break;
+ case DX_HASH_HALF_MD4_UNSIGNED:
+ str2hashbuf = str2hashbuf_unsigned;
case DX_HASH_HALF_MD4:
p = name;
while (len > 0) {
- str2hashbuf(p, len, in, 8);
+ (*str2hashbuf)(p, len, in, 8);
half_md4_transform(buf, in);
len -= 32;
p += 32;
@@ -127,10 +182,12 @@ int ext4fs_dirhash(const char *name, int
minor_hash = buf[2];
hash = buf[1];
break;
+ case DX_HASH_TEA_UNSIGNED:
+ str2hashbuf = str2hashbuf_unsigned;
case DX_HASH_TEA:
p = name;
while (len > 0) {
- str2hashbuf(p, len, in, 4);
+ (*str2hashbuf)(p, len, in, 4);
TEA_transform(buf, in);
len -= 16;
p += 16;
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -372,6 +372,8 @@ dx_probe(const struct qstr *d_name, stru
goto fail;
}
hinfo->hash_version = root->info.hash_version;
+ if (hinfo->hash_version <= DX_HASH_TEA)
+ hinfo->hash_version += EXT4_SB(dir->i_sb)->s_hash_unsigned;
hinfo->seed = EXT4_SB(dir->i_sb)->s_hash_seed;
if (d_name)
ext4fs_dirhash(d_name->name, d_name->len, hinfo);
@@ -641,6 +643,9 @@ int ext4_htree_fill_tree(struct file *di
dir = dir_file->f_path.dentry->d_inode;
if (!(EXT4_I(dir)->i_flags & EXT4_INDEX_FL)) {
hinfo.hash_version = EXT4_SB(dir->i_sb)->s_def_hash_version;
+ if (hinfo.hash_version <= DX_HASH_TEA)
+ hinfo.hash_version +=
+ EXT4_SB(dir->i_sb)->s_hash_unsigned;
hinfo.seed = EXT4_SB(dir->i_sb)->s_hash_seed;
count = htree_dirblock_to_tree(dir_file, dir, 0, &hinfo,
start_hash, start_minor_hash);
@@ -1408,6 +1413,8 @@ static int make_indexed_dir(handle_t *ha

/* Initialize as for dx_probe */
hinfo.hash_version = root->info.hash_version;
+ if (hinfo.hash_version <= DX_HASH_TEA)
+ hinfo.hash_version += EXT4_SB(dir->i_sb)->s_hash_unsigned;
hinfo.seed = EXT4_SB(dir->i_sb)->s_hash_seed;
ext4fs_dirhash(name, namelen, &hinfo);
frame = frames;
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2118,6 +2118,18 @@ static int ext4_fill_super(struct super_
for (i = 0; i < 4; i++)
sbi->s_hash_seed[i] = le32_to_cpu(es->s_hash_seed[i]);
sbi->s_def_hash_version = es->s_def_hash_version;
+ i = le32_to_cpu(es->s_flags);
+ if (i & EXT2_FLAGS_UNSIGNED_HASH)
+ sbi->s_hash_unsigned = 3;
+ else if ((i & EXT2_FLAGS_SIGNED_HASH) == 0) {
+#ifdef __CHAR_UNSIGNED__
+ es->s_flags |= cpu_to_le32(EXT2_FLAGS_UNSIGNED_HASH);
+ sbi->s_hash_unsigned = 3;
+#else
+ es->s_flags |= cpu_to_le32(EXT2_FLAGS_SIGNED_HASH);
+#endif
+ sb->s_dirt = 1;
+ }

if (sbi->s_blocks_per_group > blocksize * 8) {
printk(KERN_ERR

--
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Next message: Greg KH: "[patch 16/39] ext4: tone down ext4_da_writepages warnings"
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Next in thread: Greg KH: "[patch 16/39] ext4: tone down ext4_da_writepages warnings"
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