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    Subject[PATCH v2] fat: Fix non-atomic NFS i_pos read
    Date
    fat_encode_fh() can fetch an invalid i_pos value on systems
    where 64-bit accesses are not atomic. Make it use the same
    accessor as the rest of the FAT code.

    Signed-off-by: Steven J. Magnani <steve@digidescorp.com>
    Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
    ---
    diff -uprN linux-3.5-rc4/fs/fat/inode.c new/fs/fat/inode.c
    --- linux-3.5-rc4/fs/fat/inode.c 2012-06-29 11:20:12.781348652 -0500
    +++ new/fs/fat/inode.c 2012-06-29 13:18:13.712940800 -0500
    @@ -738,22 +738,21 @@ static int
    fat_encode_fh(struct inode *inode, __u32 *fh, int *lenp, struct inode *parent)
    {
    int len = *lenp;
    - u32 ipos_h, ipos_m, ipos_l;
    + struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
    + loff_t i_pos;

    if (len < 5) {
    *lenp = 5;
    return 255; /* no room */
    }

    - ipos_h = MSDOS_I(inode)->i_pos >> 8;
    - ipos_m = (MSDOS_I(inode)->i_pos & 0xf0) << 24;
    - ipos_l = (MSDOS_I(inode)->i_pos & 0x0f) << 28;
    + i_pos = fat_i_pos_read(sbi, inode);
    *lenp = 5;
    fh[0] = inode->i_ino;
    fh[1] = inode->i_generation;
    - fh[2] = ipos_h;
    - fh[3] = ipos_m | MSDOS_I(inode)->i_logstart;
    - fh[4] = ipos_l;
    + fh[2] = i_pos >> 8;
    + fh[3] = ((i_pos & 0xf0) << 24) | MSDOS_I(inode)->i_logstart;
    + fh[4] = (i_pos & 0x0f) << 28;
    if (parent)
    fh[4] |= MSDOS_I(parent)->i_logstart;
    return 3;


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