f2fs: fix to trigger fsck if dirent.name_len is zero

While traversing dirents in f2fs_fill_dentries(), if bitmap is valid,
filename length should not be zero, otherwise, directory structure
consistency could be corrupted, in this case, let's print related
info and set SBI_NEED_FSCK to trigger fsck for repairing.

Signed-off-by: Chao Yu <[e-mail]>
Signed-off-by: Jaegeuk Kim <[e-mail]>

fs/f2fs/dir.c

···
 		if (de->name_len == 0) {
 			bit_pos++;
 			ctx->pos = start_pos + bit_pos;
+			printk_ratelimited(
+				"%s, invalid namelen(0), ino:%u, run fsck to fix.",
+				KERN_WARNING, le32_to_cpu(de->ino));
+			set_sbi_flag(sbi, SBI_NEED_FSCK);
 			continue;
 		}