f2fs: show mounted time

Let's show mounted time.

Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/debug.c

@@ -301,6 +301,9 @@ static int stat_show(struct seq_file *s, void *v)
 			   si->ssa_area_segs, si->main_area_segs);
 		seq_printf(s, "(OverProv:%d Resv:%d)]\n\n",
 			   si->overp_segs, si->rsvd_segs);
+		seq_printf(s, "Current Time Sec: %llu / Mounted Time Sec: %llu\n\n",
+					ktime_get_boottime_seconds(),
+					SIT_I(si->sbi)->mounted_time);
 		if (test_opt(si->sbi, DISCARD))
 			seq_printf(s, "Utilization: %u%% (%u valid blocks, %u discard blocks)\n",
 				si->utilization, si->valid_count, si->discard_blks);