jbd2: don't abort if flushing file data failed

In ordered mode, the current jbd2 aborts the journal if a file data buffer
has an error.  But this behavior is unintended, and we found that it has
been adopted accidentally.

This patch undoes it and just calls printk() instead of aborting the
journal.  Unlike a similar patch for ext3/jbd, file data buffers are
written via generic_writepages().  But we also need to set AS_EIO
into their mappings because wait_on_page_writeback_range() clears
AS_EIO before a user process sees it.

Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>