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    SubjectRe: ext4_fiemap gives 0 extents for files smaller than a block (patch included)
    Leonard Michlmayr wrote:
    > Thank you for your reply.
    >
    >>> @@ -3700,7 +3701,8 @@
    >>> start_blk = start >> inode->i_sb->s_blocksize_bits;
    >>> - len_blks = len >> inode->i_sb->s_blocksize_bits;
    >>> + end_blk = (start + len - 1) >> inode->i_sb->s_blocksize_bits;
    >>> + len_blks = end_blk - start_blk + 1;
    >> I don't think this is quite correct either. For example, if blocksize
    >> is 1024
    >> and start is 1023 (start_blk = 0) and len is 2 (end = 1024, end_blk =
    >> 1) then
    >> len_blks = 2 which is too much.
    >
    > I think that len_blks = 2 is the correct value, because the requested
    > region extends into 2 blocks (namely 0 and 1). If both blocks are in two
    > separate extents, then ext4_ext_walk_space should report 2 extents. (If
    > it's the same extent, only 1 will be reported anyways)
    >
    >> I think the right calculation here is:
    >>
    >> end_blk = (start + len + inode->i_sb->s_blocksize - 1) >>
    >> inode->i_sb->s_blocksize_bits;
    >> len_blks = end_blk - start_blk;
    >>
    >
    > This is exactly the same (provided that len > 0). You can convince
    > yourself easily that ((blocksize + x) >> blocksize_bits == x >>
    > blocksize_bits + 1) for any positive x, because the lower bits of
    > blocksize are all 0. (Your calculation would handle the case len == 0
    > right, if that was allowed.)
    >
    > Regards
    > Leonard

    I was wondering if there is any update on the status of this patch.
    Thanks !

    Warm Regards,
    Surbhi.




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