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    Subject[45/53] ext4: handle EOF correctly in ext4_bio_write_page()
    3.1-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Yongqiang Yang <xiaoqiangnk@gmail.com>

    commit 5a0dc7365c240795bf190766eba7a27600be3b3e upstream.

    We need to zero out part of a page which beyond EOF before setting uptodate,
    otherwise, mapread or write will see non-zero data beyond EOF.

    Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
    Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    fs/ext4/page-io.c | 12 ++++++++++++
    1 file changed, 12 insertions(+)

    --- a/fs/ext4/page-io.c
    +++ b/fs/ext4/page-io.c
    @@ -401,6 +401,18 @@ int ext4_bio_write_page(struct ext4_io_s

    block_end = block_start + blocksize;
    if (block_start >= len) {
    + /*
    + * Comments copied from block_write_full_page_endio:
    + *
    + * The page straddles i_size. It must be zeroed out on
    + * each and every writepage invocation because it may
    + * be mmapped. "A file is mapped in multiples of the
    + * page size. For a file that is not a multiple of
    + * the page size, the remaining memory is zeroed when
    + * mapped, and writes to that region are not written
    + * out to the file."
    + */
    + zero_user_segment(page, block_start, block_end);
    clear_buffer_dirty(bh);
    set_buffer_uptodate(bh);
    continue;



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