ext4: Add support for non-native signed/unsigned htree hash algorithms

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>

5 files changed, 90 insertions, 10 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index b0537c827024..8370ffd2d62f 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -891,6 +891,9 @@ static inline __le16 ext4_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/fs/ext4/ext4_sb.h b/fs/ext4/ext4_sb.h
index b21f16713db0..ad7ea09baa72 100644
--- 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;
diff --git a/fs/ext4/hash.c b/fs/ext4/hash.c
index 556ca8eba3db..ac8f168c8ab4 100644
--- a/fs/ext4/hash.c
+++ b/fs/ext4/hash.c
@@ -35,23 +35,71 @@ 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_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, int len, __u32 *buf, int num)
         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 len, struct dx_hash_info *hinfo)
         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 len, struct dx_hash_info *hinfo)
         }
 
         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 len, struct dx_hash_info *hinfo)
                 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;
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 9fd2a5e1be4d..315858db8078 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -372,6 +372,8 @@ dx_probe(const struct qstr *d_name, struct inode *dir,
                 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 *dir_file, __u32 start_hash,
         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 *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 += 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;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 04158ad74dbb..08fc86a358d3 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2118,6 +2118,18 @@ static int ext4_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) {
+#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