The buffer head pointer passed to journal_wait_on_commit_record() could
be NULL if the previous journal_submit_commit_record() failed or journal
has already aborted.

Looking at the jbd2 debug messages, before the oops happened, the jbd2
is aborted due to trying to access the next log block beyond the end
of device. This might be caused by using a corrupted image.

We need to check the error returns from journal_submit_commit_record()
and avoid calling journal_wait_on_commit_record() in the failure case.

This addresses Kernel Bugzilla #9849
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>