ocfs2: direct write will call ocfs2_rw_unlock() twice when doing aio+dio

ocfs2_file_write_iter() is usng the wrong return value ('written').  This
will cause ocfs2_rw_unlock() be called both in write_iter & end_io,
triggering a BUG_ON.

This issue was introduced by commit 7da839c4 ("ocfs2: use
__generic_file_write_iter()").

Orabug: 21612107
Fixes: 7da839c4 ("ocfs2: use __generic_file_write_iter()")
Signed-off-by: Ryan Ding <ryan.ding@oracle.com>
Reviewed-by: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ocfs2/file.c

@@ -2378,6 +2378,20 @@ static ssize_t ocfs2_file_write_iter(struct kiocb *iocb,
 	/* buffered aio wouldn't have proper lock coverage today */
 	BUG_ON(written == -EIOCBQUEUED && !(iocb->ki_flags & IOCB_DIRECT));
 
+	/*
+	 * deep in g_f_a_w_n()->ocfs2_direct_IO we pass in a ocfs2_dio_end_io
+	 * function pointer which is called when o_direct io completes so that
+	 * it can unlock our rw lock.
+	 * Unfortunately there are error cases which call end_io and others
+	 * that don't.  so we don't have to unlock the rw_lock if either an
+	 * async dio is going to do it in the future or an end_io after an
+	 * error has already done it.
+	 */
+	if ((written == -EIOCBQUEUED) || (!ocfs2_iocb_is_rw_locked(iocb))) {
+		rw_level = -1;
+		unaligned_dio = 0;
+	}
+
 	if (unlikely(written <= 0))
 		goto no_sync;
 
@@ -2402,20 +2416,6 @@ static ssize_t ocfs2_file_write_iter(struct kiocb *iocb,
 	}
 
 no_sync:
-	/*
-	 * deep in g_f_a_w_n()->ocfs2_direct_IO we pass in a ocfs2_dio_end_io
-	 * function pointer which is called when o_direct io completes so that
-	 * it can unlock our rw lock.
-	 * Unfortunately there are error cases which call end_io and others
-	 * that don't.  so we don't have to unlock the rw_lock if either an
-	 * async dio is going to do it in the future or an end_io after an
-	 * error has already done it.
-	 */
-	if ((ret == -EIOCBQUEUED) || (!ocfs2_iocb_is_rw_locked(iocb))) {
-		rw_level = -1;
-		unaligned_dio = 0;
-	}
-
 	if (unaligned_dio) {
 		ocfs2_iocb_clear_unaligned_aio(iocb);
 		mutex_unlock(&OCFS2_I(inode)->ip_unaligned_aio);