On Thu, Oct 27, 2016 at 3:56 PM, Junio C Hamano <gitster@xxxxxxxxx> wrote: > > I also thought O_NOATIME shouldn't be an effective fcntl(2) thing, > for the reasons you stated above, when I was studying the area > because of the discussion on these patches. I was surprised to see > that http://man7.org/linux/man-pages/man2/fcntl.2.html contradicts > by saying F_SETFL can take O_NOATIME. > > Perhaps it deserves a bugreport? It's not a bug per se. You can indeed change O_NOATIME with F_SETFL. And it actually does matter, since atime is normally changed by mmap(), read() and write() calls. So F_SETFL O_NOATIME actually does make sense, but it doesn't cover the atime update done by open() itself. That said, now that I think about it, I should double-check: maybe open() doesn't actually set atime at all, and we *could* do NOATIME with SETFL after all. The exact [acm]time semantics are damn subtle. Linus