Ocfs2: Teach 'coherency=full' O_DIRECT writes to correctly up_read i_alloc_sem.

Due to newly-introduced 'coherency=full' O_DIRECT writes also takes the EX
rw_lock like buffered writes did(rw_level == 1), it turns out messing the
usage of 'level' in ocfs2_dio_end_io() up, which caused i_alloc_sem being
failed to get up_read'd correctly.

This patch tries to teach ocfs2_dio_end_io to understand well on all locking
stuffs by explicitly introducing a new bit for i_alloc_sem in iocb's private
data, just like what we did for rw_lock.

Signed-off-by: Tristan Ye <tristan.ye@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index f1e962c..0d7c554 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -573,11 +573,14 @@
 	/* this io's submitter should not have unlocked this before we could */
 	BUG_ON(!ocfs2_iocb_is_rw_locked(iocb));
 
+	if (ocfs2_iocb_is_sem_locked(iocb)) {
+		up_read(&inode->i_alloc_sem);
+		ocfs2_iocb_clear_sem_locked(iocb);
+	}
+
 	ocfs2_iocb_clear_rw_locked(iocb);
 
 	level = ocfs2_iocb_rw_locked_level(iocb);
-	if (!level)
-		up_read(&inode->i_alloc_sem);
 	ocfs2_rw_unlock(inode, level);
 
 	if (is_async)