4 ms·

That's a problem for programs that do recursive fs descent (e.g. find, tar) because they use st_dev and st_ino alone for remembering what directories they've be

• the_mitsuhiko 1y ago
  You are not wrong, but the issues with tar are well known. Linus himself had this to say [1]: > Well, the fact that it hits snapshots, shows that the real problem is just "tar does stupid things that it shouldn't do". > Yes, inode numbers used to be special, and there's history behind it. But we should basically try very hard to walk away from that broken history. > An inode number just isn't a unique descriptor any more. We're not living in the 1970s, and filesystems have changed. You might still get away with it most of the time today, but it's causing more and more issues. [1]: https://lkml.iu.edu/hypermail/linux/kernel/2401.3/04127.html https://lkml.iu.edu/hypermail/linux/kernel/2401.3/04127.html
  • amiga386 1y ago
    That sounds like blaming userspace. If it's not the 1970s anymore, then update the POSIX standard with a solution that works for all OSes (including the BSDs) and can be relied upon. Definitely don't suggest a Linux-only solution for a Linux-only problem.
    • dwattttt 1y ago
      Have you checked what POSIX has to say about inode numbers? It may say less than you think.
      • amiga386 1y ago
        https://pubs.opengroup.org/onlinepubs/009696799/basedefs/sys/stat.h.html https://pubs.opengroup.org/onlinepubs/009696799/basedefs/sys... > The st_ino and st_dev fields taken together uniquely identify the file within the system. It says exactly what it ought to say.
        • dwattttt 1y ago
          Issue 8 (2024, https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/sys_stat.h.html https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/sy...) relaxed the language there. st_ino and st_dev still uniquely identify a file, but it now notes that the duration it identifies it for is not indefinite. As an example, it offers that the identity of a file that's deleted could be reused.
          • amiga386 1y ago
            It says pretty much what I said at the start of the thread (https://news.ycombinator.com/item?id=44157026 https://news.ycombinator.com/item?id=44157026), and yet this is what Linux is having problems complying with: > A file identity is uniquely determined by the combination of st_dev and st_ino. At any given time in a system, distinct files shall have distinct file identities; hard links to the same file shall have the same file identity. Over time, these file identities can be reused for different files. For example, the st_ino value can be reused after the last link to a file is unlinked and the space occupied by the file has been freed, and the st_dev value associated with a file system can be reused if that file system is detached ("unmounted") and another is attached ("mounted"). I still think POSIX says exactly what it needs to say, and Linux ought to either comply with it, or lead the standardisation process on what should be done instead. Don't say "tar is old". Tar's problems with Linux are the same problems that find, zip, rsync, cp and all other fs walking programs have. If memorising st_dev and st_ino are no good, tell us what cross-platform approach should be taken instead.
  • account42 1y ago
    Sounds like Linus is advocating for ... breaking userspace. We are truly living in the end times.