ocfs2: fix brelse warning if ocfs2_direct_IO_get_blocks failed

In ocfs2_direct_IO_write, if ocfs2_direct_IO_get_blocks failed, the di_bh will be used again in unlikely branch, and this will hit a warning "VFS: brelse: Trying to free free buffer" when jbd2 do checkpoint. Fix this issue by setting di_bh to NULL after brelse.

---
 fs/ocfs2/aops.c | 1 +
 1 file changed, 1 insertion(+)

index 38e5a9f..cf4be6a 100644
@@ -731,6 +731,7 @@ static ssize_t ocfs2_direct_IO_write(struct kiocb *iocb,
 
 		ocfs2_inode_unlock(inode, 1);
 		brelse(di_bh);
+		di_bh = NULL;
 	}
 
 	written = __blockdev_direct_IO(WRITE, iocb, inode, inode->i_sb->s_bdev,

1.8.4.3