[PATCH,RFC] ext3: Add support for non-native signed/unsigned htree hash algorithms

Theodore Ts'o
2008-10-21T05:19:25Z

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@mit.edu>
Cc: akpm@linux-foundation.org
Cc: linux-kernel@vger.kernel.org
---
fs/ext3/hash.c | 42 +++++++++++++++++++++++++++++++++---------
fs/ext3/namei.c | 7 +++++++
fs/ext3/super.c | 15 +++++++++++++++
include/linux/ext3_fs.h | 28 +++++++++++++++++++++++++++-
include/linux/ext3_fs_sb.h | 1 +
5 files changed, 83 insertions(+), 10 deletions(-)

diff --git a/fs/ext3/hash.c b/fs/ext3/hash.c
index c30e149..855eacb 100644
--- a/fs/ext3/hash.c
+++ b/fs/ext3/hash.c
@@ -35,11 +35,20 @@ static void TEA_transform(__u32 buf[4], __u32 const in[])

/* The old legacy hash */
-static __u32 dx_hack_hash (const char *name, int len)
+static __u32 dx_hack_hash (const char *name, int len, int unsigned_flag)
{
- __u32 hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
+ __u32 hash, hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
+ const unsigned char *ucp = (const unsigned char *) name;
+ const signed char *scp = (const signed char *) name;
+ int c;
+
while (len--) {
- __u32 hash = hash1 + (hash0 ^ (*name++ * 7152373));
+ if (unsigned_flag)
+ c = (int) *ucp++;
+ else
+ c = (int) *scp++;
+
+ hash = hash1 + (hash0 ^ (c * 7152373));

if (hash & 0x80000000) hash -= 0x7fffffff;
hash1 = hash0;
@@ -48,10 +57,13 @@ static __u32 dx_hack_hash (const char *name, int len)
return (hash0 << 1);
}

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

pad = (__u32)len | ((__u32)len << 8);
pad |= pad << 16;
@@ -62,7 +74,12 @@ static void str2hashbuf(const char *msg, int len, __u32 *buf, int num)
for (i=0; i < len; i++) {
if ((i % 4) == 0)
val = pad;
- val = msg[i] + (val << 8);
+ if (unsigned_flag)
+ c = (int) ucp[i];
+ else
+ c = (int) scp[i];
+
+ val = c + (val << 8);
if ((i % 4) == 3) {
*buf++ = val;
val = pad;
@@ -95,6 +112,7 @@ int ext3fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
const char *p;
int i;
__u32 in[8], buf[4];
+ int unsigned_flag = 0;

/* Initialize the default seed for the hash checksum functions */
buf[0] = 0x67452301;
@@ -113,13 +131,17 @@ int ext3fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
}

switch (hinfo->hash_version) {
+ case DX_HASH_LEGACY_UNSIGNED:
+ unsigned_flag++;
case DX_HASH_LEGACY:
- hash = dx_hack_hash(name, len);
+ hash = dx_hack_hash(name, len, unsigned_flag);
break;
+ case DX_HASH_HALF_MD4_UNSIGNED:
+ unsigned_flag++;
case DX_HASH_HALF_MD4:
p = name;
while (len > 0) {
- str2hashbuf(p, len, in, 8);
+ str2hashbuf(p, len, in, 8, unsigned_flag);
half_md4_transform(buf, in);
len -= 32;
p += 32;
@@ -127,10 +149,12 @@ int ext3fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
minor_hash = buf[2];
hash = buf[1];
break;
+ case DX_HASH_TEA_UNSIGNED:
+ unsigned_flag++;
case DX_HASH_TEA:
p = name;
while (len > 0) {
- str2hashbuf(p, len, in, 4);
+ str2hashbuf(p, len, in, 4, unsigned_flag);
TEA_transform(buf, in);
len -= 16;
p += 16;
diff --git a/fs/ext3/namei.c b/fs/ext3/namei.c
index de13e91..a688a47 100644
--- a/fs/ext3/namei.c
+++ b/fs/ext3/namei.c
@@ -369,6 +369,8 @@ dx_probe(struct dentry *dentry, struct inode *dir,
goto fail;
}
hinfo->hash_version = root->info.hash_version;
+ if (hinfo->hash_version <= DX_HASH_TEA)
+ hinfo->hash_version += EXT3_SB(dir->i_sb)->s_hash_unsigned;
hinfo->seed = EXT3_SB(dir->i_sb)->s_hash_seed;
if (dentry)
ext3fs_dirhash(dentry->d_name.name, dentry->d_name.len, hinfo);
@@ -637,6 +639,9 @@ int ext3_htree_fill_tree(struct file *dir_file, __u32 start_hash,
dir = dir_file->f_path.dentry->d_inode;
if (!(EXT3_I(dir)->i_flags & EXT3_INDEX_FL)) {
hinfo.hash_version = EXT3_SB(dir->i_sb)->s_def_hash_version;
+ if (hinfo.hash_version <= DX_HASH_TEA)
+ hinfo.hash_version +=
+ EXT3_SB(dir->i_sb)->s_hash_unsigned;
hinfo.seed = EXT3_SB(dir->i_sb)->s_hash_seed;
count = htree_dirblock_to_tree(dir_file, dir, 0, &hinfo,
start_hash, start_minor_hash);
@@ -1415,6 +1420,8 @@ static int make_indexed_dir(handle_t *handle, struct dentry *dentry,

/* Initialize as for dx_probe */
hinfo.hash_version = root->info.hash_version;
+ if (hinfo.hash_version <= DX_HASH_TEA)
+ hinfo.hash_version += EXT3_SB(dir->i_sb)->s_hash_unsigned;
hinfo.seed = EXT3_SB(dir->i_sb)->s_hash_seed;
ext3fs_dirhash(name, namelen, &hinfo);
frame = frames;
diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index f38a5af..fa706ea 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -1727,6 +1727,21 @@ static int ext3_fill_super (struct super_block *sb, void *data, int silent)
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) {
+ char c;
+
+ c = (char) 255;
+ if (((int) c) == -1) {
+ es->s_flags |= cpu_to_le32(EXT2_FLAGS_SIGNED_HASH);
+ } else {
+ es->s_flags |= cpu_to_le32(EXT2_FLAGS_UNSIGNED_HASH);
+ sbi->s_hash_unsigned = 3;
+ }
+ sb->s_dirt = 1;
+ }

if (sbi->s_blocks_per_group > blocksize * 8) {
printk (KERN_ERR
diff --git a/include/linux/ext3_fs.h b/include/linux/ext3_fs.h
index 8120fa1..57420c8 100644
--- a/include/linux/ext3_fs.h
+++ b/include/linux/ext3_fs.h
@@ -354,6 +354,13 @@ struct ext3_inode {
#define EXT3_ORPHAN_FS 0x0004 /* Orphans being recovered */

/*
+ * Misc. filesystem flags
+ */
+#define EXT2_FLAGS_SIGNED_HASH 0x0001 /* Signed dirhash in use */
+#define EXT2_FLAGS_UNSIGNED_HASH 0x0002 /* Unsigned dirhash in use */
+#define EXT2_FLAGS_TEST_FILESYS 0x0004 /* to test development code */
+
+/*
* Mount flags
*/
#define EXT3_MOUNT_CHECK 0x00001 /* Do mount-time checks */
@@ -487,7 +494,23 @@ struct ext3_super_block {
__u16 s_reserved_word_pad;
__le32 s_default_mount_opts;
__le32 s_first_meta_bg; /* First metablock block group */
- __u32 s_reserved[190]; /* Padding to the end of the block */
+ __le32 s_mkfs_time; /* When the filesystem was created */
+ __le32 s_jnl_blocks[17]; /* Backup of the journal inode */
+ /* 64bit support valid if EXT4_FEATURE_COMPAT_64BIT */
+/*150*/ __le32 s_blocks_count_hi; /* Blocks count */
+ __le32 s_r_blocks_count_hi; /* Reserved blocks count */
+ __le32 s_free_blocks_count_hi; /* Free blocks count */
+ __le16 s_min_extra_isize; /* All inodes have at least # bytes */
+ __le16 s_want_extra_isize; /* New inodes should reserve # bytes */
+ __le32 s_flags; /* Miscellaneous flags */
+ __le16 s_raid_stride; /* RAID stride */
+ __le16 s_mmp_interval; /* # seconds to wait in MMP checking */
+ __le64 s_mmp_block; /* Block for multi-mount protection */
+ __le32 s_raid_stripe_width; /* blocks on all data disks (N*stride)*/
+ __u8 s_log_groups_per_flex; /* FLEX_BG group size */
+ __u8 s_reserved_char_pad2;
+ __le16 s_reserved_pad;
+ __u32 s_reserved[162]; /* Padding to the end of the block */
};

#ifdef __KERNEL__
@@ -692,6 +715,9 @@ static inline __le16 ext3_rec_len_to_disk(unsigned len)
#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__

diff --git a/include/linux/ext3_fs_sb.h b/include/linux/ext3_fs_sb.h
index b65f028..50dc80a 100644
--- a/include/linux/ext3_fs_sb.h
+++ b/include/linux/ext3_fs_sb.h
@@ -57,6 +57,7 @@ struct ext3_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;
--
1.5.6.1.205.ge2c7.dirty