Hi, Rob. And Stefan. First of all, this patch got to linux-next ( https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/log/?qt=author&q=Stefan+Berger ), so it seems it soon will be in mainline. On Thu, Dec 21, 2023 at 12:24 PM Rob Landley <rob@xxxxxxxxxxx> wrote: > Can you build tmpfs on a nommu system? Last I checked the plumbing expects swap, > but it's been a while... Okay, I agree, let's not remove ramfs. Still, I don't like this (already applied) patch. init= and rdinit= are two different options, and this is good. So, I think we should have two different options. Analogously they should be rootfstype= and rdrootfstype=. rootfstype= should be read by kernel when deciding how to mount real root (i. e. not initramfs or initrd) only and rdrootfstype= when deciding how to mount initramfs only. This will make everything cleaner. Also note that userspace tools read rootfstype= and assume that it always applies to real root. For example, this is Debian's rdinit: https://salsa.debian.org/kernel-team/initramfs-tools/-/blob/cf964bfb4362019fd7fba1e839e403ff950dca8e/init#L103 As you can see, this shell script parses /proc/cmdline and assumes that rootfstype= always applies to real root. So, if someone sets rootfstype= to tmpfs or ramfs, this will likely break this script. So, I think the code should look so: +if (IS_ENABLED(CONFIG_TMPFS)) { + if (!rd_root_fs_names) // We assume rd_root_fs_names is set by rdrootfstype= + is_tmpfs = true; // Use tmpfs if rdrootfstype= is not set. To get all tmpfs benefits + else if (rd_root_fs_names && !!strstr(rd_root_fs_names, "tmpfs")) + is_tmpfs = true; +} Yes, this will slightly break compatibility. I. e. this will make Linux always choose tmpfs if rdrootfstype= is not present. But I think there is nothing wrong with it. If a user cares, he will set rdrootfstype= . And early boot code will become a lot more clean and logical. Rob, do you agree? Stefan, do you agree? Then I will write a patch, with doc changes (currently I use gmail web interface, of course I will use git send-email when I sent actual patch) -- Askar Safin
