f2fs: fix to update mtime correctly

If we change system time to the past, get_mtime() will return a
overflowed time, and SIT_I(sbi)->max_mtime will be udpated
incorrectly, this patch fixes the two issues.

Signed-off-by: Chao Yu <[email protected]>
Signed-off-by: Jaegeuk Kim <[email protected]>
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index f0f9593..6dbdf2c 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -1822,8 +1822,9 @@ static void update_sit_entry(struct f2fs_sb_info *sbi, block_t blkaddr, int del)
 				(new_vblocks > sbi->blocks_per_seg)));
 
 	se->valid_blocks = new_vblocks;
-	se->mtime = get_mtime(sbi);
-	SIT_I(sbi)->max_mtime = se->mtime;
+	se->mtime = get_mtime(sbi, false);
+	if (se->mtime > SIT_I(sbi)->max_mtime)
+		SIT_I(sbi)->max_mtime = se->mtime;
 
 	/* Update valid block bitmap */
 	if (del > 0) {
@@ -3884,7 +3885,7 @@ static void init_min_max_mtime(struct f2fs_sb_info *sbi)
 		if (sit_i->min_mtime > mtime)
 			sit_i->min_mtime = mtime;
 	}
-	sit_i->max_mtime = get_mtime(sbi);
+	sit_i->max_mtime = get_mtime(sbi, false);
 	up_write(&sit_i->sentry_lock);
 }