Revert "ext4: use ext4_write_inode() when fsyncing w/o a journal"

Revert "ext4: use ext4_write_inode() when fsyncing w/o a journal"

commit 8fdd60f2ae3682caf2a7258626abc21eb4711892 upstream.

This reverts commit ad211f3e94b314a910d4af03178a0b52a7d1ee0a.

As Jan Kara pointed out, this change was unsafe since it means we lose
the call to sync_mapping_buffers() in the nojournal case.  The
original point of the commit was avoid taking the inode mutex (since
it causes a lockdep warning in generic/113); but we need the mutex in
order to call sync_mapping_buffers().

The real fix to this problem was discussed here:

https://lore.kernel.org/lkml/20181025150540.259281-4-bvanassche@acm.org

The proposed patch was to fix a syzbot complaint, but the problem can
also demonstrated via "kvm-xfstests -c nojournal generic/113".
Multiple solutions were discused in the e-mail thread, but none have
landed in the kernel as of this writing.  Anyway, commit
ad211f3e94b314 is absolutely the wrong way to suppress the lockdep, so
revert it.

Fixes: ad211f3e94b314a910d4af03178a0b52a7d1ee0a ("ext4: use ext4_write_inode() when fsyncing w/o a journal")
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reported: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>