디렉토리 엔트리와 링크 간략 설명
https://velog.io/@kyoung99u/UNIX-File-System
[Btrfs] COW 과정
https://btrfs.readthedocs.io/en/latest/dev/dev-btrfs-design.html
https://www.semanticscholar.org/paper/Effects-of-Recursive-Update-in-Copy-on-Write-File-[…]en-Wang/2d85b9f691838dd8ca80857d05c9176bb49f95c7/figure/0
중간에 나왔던 질문