nilfs2: fix duplicate call to nilfs_segctor_cancel_freev

Andreas Beckmann gave me a report that nilfs logged the following
warnings when it got a disk full:

  nilfs_sufile_do_cancel_free: segment 0 must be clean
  nilfs_sufile_do_cancel_free: segment 1 must be clean

These arise from a duplicate call to nilfs_segctor_cancel_freev in an
error path of log writer.  This will fix the issue.
Reported-by: Andreas Beckmann <debian@abeckmann.de>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

fs/nilfs2/segment.c

@@ -1510,6 +1510,12 @@ static int nilfs_segctor_collect(struct nilfs_sc_info *sci,
 		if (mode != SC_LSEG_SR || sci->sc_stage.scnt < NILFS_ST_CPFILE)
 			break;
 
+		nilfs_clear_logs(&sci->sc_segbufs);
+
+		err = nilfs_segctor_extend_segments(sci, nilfs, nadd);
+		if (unlikely(err))
+			return err;
+
 		if (sci->sc_stage.flags & NILFS_CF_SUFREED) {
 			err = nilfs_sufile_cancel_freev(nilfs->ns_sufile,
 							sci->sc_freesegs,
@@ -1517,12 +1523,6 @@ static int nilfs_segctor_collect(struct nilfs_sc_info *sci,
 							NULL);
 			WARN_ON(err); /* do not happen */
 		}
-		nilfs_clear_logs(&sci->sc_segbufs);
-
-		err = nilfs_segctor_extend_segments(sci, nilfs, nadd);
-		if (unlikely(err))
-			return err;
-
 		nadd = min_t(int, nadd << 1, SC_MAX_SEGDELTA);
 		sci->sc_stage = prev_stage;
 	}