In gc_data_segment in fs/f2fs/gc.c in the Linux kernel before 5.16.3, special files are not considered, leading to a move_data_page NULL pointer dereference.
https://bugzilla.kernel.org/show_bug.cgi?id=215231
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.16.3
https://lore.kernel.org/linux-f2fs-devel/20211206144421.3735-3-chao%40kernel.org/T/