PM / Sleep: JBD and JBD2 missing set_freezable()

With the latest and greatest changes to the freezer, I started seeing
panics that were caused by jbd2 running post-process freezing and
hitting the canary BUG_ON for non-TuxOnIce I/O submission. I've traced
this back to a lack of set_freezable calls in both jbd and jbd2. Since
they're clearly meant to be frozen (there are tests for freezing()), I
submit the following patch to add the missing calls.
Signed-off-by: NNigel Cunningham <nigel@tuxonice.net>
Acked-by: NJan Kara <jack@suse.cz>
Signed-off-by: NRafael J. Wysocki <rjw@sisk.pl>

fs/jbd/journal.c

@@ -129,6 +129,8 @@ static int kjournald(void *arg)
 	setup_timer(&journal->j_commit_timer, commit_timeout,
 			(unsigned long)current);
 
+	set_freezable();
+
 	/* Record that the journal thread is running */
 	journal->j_task = current;
 	wake_up(&journal->j_wait_done_commit);

fs/jbd2/journal.c

@@ -139,6 +139,8 @@ static int kjournald2(void *arg)
 	setup_timer(&journal->j_commit_timer, commit_timeout,
 			(unsigned long)current);
 
+	set_freezable();
+
 	/* Record that the journal thread is running */
 	journal->j_task = current;
 	wake_up(&journal->j_wait_done_commit);