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    Subject[PATCH 01/39] ext3: Add support for non-native signed/unsigned htree hash algorithms
    Date
    From: Theodore Ts'o <tytso@mit.edu>

    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 | 77 ++++++++++++++++++++++++++++++++++++++------
    fs/ext3/namei.c | 7 ++++
    fs/ext3/super.c | 12 +++++++
    include/linux/ext3_fs.h | 28 +++++++++++++++-
    include/linux/ext3_fs_sb.h | 1 +
    5 files changed, 114 insertions(+), 11 deletions(-)

    diff --git a/fs/ext3/hash.c b/fs/ext3/hash.c
    index c30e149..7d215b4 100644
    --- a/fs/ext3/hash.c
    +++ b/fs/ext3/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(const char *msg, int len, __u32 *buf, int num)
    +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_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 ext3fs_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 ext3fs_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 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:
    + 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/ext3/namei.c b/fs/ext3/namei.c
    index 1dd2abe..287b304 100644
    --- a/fs/ext3/namei.c
    +++ b/fs/ext3/namei.c
    @@ -368,6 +368,8 @@ dx_probe(struct qstr *entry, 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 (entry)
    ext3fs_dirhash(entry->name, entry->len, hinfo);
    @@ -636,6 +638,9 @@ 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);
    @@ -1398,6 +1403,8 @@ 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 f6c94f2..541d5e4 100644
    --- a/fs/ext3/super.c
    +++ b/fs/ext3/super.c
    @@ -1744,6 +1744,18 @@ 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) {
    +#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
    diff --git a/include/linux/ext3_fs.h b/include/linux/ext3_fs.h
    index d14f029..9004794 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 */
    @@ -489,7 +496,23 @@ 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__
    @@ -694,6 +717,9 @@ 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 e024e38..a4e9216 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;
    --
    1.5.4.3


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