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    SubjectRe: stat64 for over 2TB file returned invalid st_blocks
    Date
    Hi,

    > > Hi all,
    > >
    > > I found a problem at stat64 on 32bit architecture.
    > >
    > > When I called stat64 for a file which is larger than 2TB, stat64
    > > returned an invalid number of blocks at st_blocks on 32bit
    > > architecture, although it returned a valid number of blocks on 64bit
    > > architecture(ia64).
    >
    > For jfs, it's a bigger problem than just stat64. When writing the inode
    > to disk, jfs calculates the number of blocks from the 32-bit value:
    > dip->di_nblocks = cpu_to_le64(PBLK2LBLK(ip->i_sb, ip->i_blocks))
    >
    > So it won't only report the wrong number of blocks, but it will actually
    > store the wrong number. :-(

    I also found another problem on generic quota code. In
    dquot_transfer(), the file usage is calculated from i_blocks via
    inode_get_bytes(). If the file is over 2TB, the change of usage is
    less than expected.

    To solve this problem, I think inode.i_blocks should be 8 byte.

    >> 2. Change the type of architecture dependent stat64.st_blocks in
    >> include/asm/asm-*/stat.h from unsigned long to unsigned long long.
    >> I tried modifying only stat64 of 32bit architecture
    >> (include/asm-i386/stat.h).
    >
    >This changes the API, but the structure does suggest that the 4-byte pad
    >should be used for the high-order bytes of st_blocks, so that's not
    >really a problem. A correct fix would replace __pad4 with
    >st_blocks_high (or something like that) and ensure that the high-order
    >word was stored there. Your proposed fix would only be correct on
    >little-endian hardware, as Jörn pointed out.

    Thank you for your advice. I'll research for glibc and consider
    how to implement.
    By the way I think, as Avi Kivity said, it's always little-endian on i386,
    is it correct?

    -- Takashi Sato

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