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    Subject[37/45] ext4: avoid potential hang in mpage_submit_io() when blocksize < pagesize
    3.0-stable review patch.  If anyone has any objections, please let me know.

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

    From: Yongqiang Yang <xiaoqiangnk@gmail.com>

    commit 13a79a4741d37fda2fbafb953f0f301dc007928f upstream.

    If there is an unwritten but clean buffer in a page and there is a
    dirty buffer after the buffer, then mpage_submit_io does not write the
    dirty buffer out. As a result, da_writepages loops forever.

    This patch fixes the problem by checking dirty flag.

    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/inode.c | 7 +++++--
    1 file changed, 5 insertions(+), 2 deletions(-)

    --- a/fs/ext4/inode.c
    +++ b/fs/ext4/inode.c
    @@ -2126,8 +2126,11 @@ static int mpage_da_submit_io(struct mpa
    clear_buffer_unwritten(bh);
    }

    - /* skip page if block allocation undone */
    - if (buffer_delay(bh) || buffer_unwritten(bh))
    + /*
    + * skip page if block allocation undone and
    + * block is dirty
    + */
    + if (ext4_bh_delay_or_unwritten(NULL, bh))
    skip_page = 1;
    bh = bh->b_this_page;
    block_start += bh->b_size;



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