jbd2: export jbd2_journal_[grab|put]_journal_head

Patch series "ocfs2: fix a deadlock case".

This fixes a deadlock case in ocfs2.  We firstly export jbd2 symbols
jbd2_journal_[grab|put]_journal_head as preparation and later use them
in ocfs2 insread of jbd_[lock|unlock]_bh_journal_head to fix the
deadlock.

This patch (of 2):

This exports symbols jbd2_journal_[grab|put]_journal_head, which will be
used outside modules, e.g.  ocfs2.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Joseph Qi <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Joel Becker <[email protected]>
Cc: Junxiao Bi <[email protected]>
Cc: Changwei Ge <[email protected]>
Cc: Gang He <[email protected]>
Cc: Jun Piao <[email protected]>
Cc: Andreas Dilger <[email protected]>
Cc: Gautham Ananthakrishna <[email protected]>
Cc: Saeed Mirzamohammadi <[email protected]>
Cc: "Theodore Ts'o" <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

fs/jbd2/journal.c

@@ -2972,6 +2972,7 @@ struct journal_head *jbd2_journal_grab_journal_head(struct buffer_head *bh)
 	jbd_unlock_bh_journal_head(bh);
 	return jh;
 }
+EXPORT_SYMBOL(jbd2_journal_grab_journal_head);
 
 static void __journal_remove_journal_head(struct buffer_head *bh)
 {
@@ -3024,6 +3025,7 @@ void jbd2_journal_put_journal_head(struct journal_head *jh)
 		jbd_unlock_bh_journal_head(bh);
 	}
 }
+EXPORT_SYMBOL(jbd2_journal_put_journal_head);
 
 /*
  * Initialize jbd inode head