On 7/19/22 07:26, Roberto Sassu wrote:
>> P.P.S. If you want to run a command other than /init out of initramfs or initrd,
>> use the rdinit=/run/this option. Note the root= overmount mechanism is
>> completely different code and uses the init=/run/this argument instead, which
>> means nothing to initramfs. Again, specifying root= says we are NOT staying in
>> initramfs.
>
> Sorry, it was some time ago. I have to go back and see why we needed
> a separate option.
Did I mention that init/do_mounts.c already has:
__setup("rootfstype=", fs_names_setup);
static char * __initdata root_fs_names;
static int __init fs_names_setup(char *str)
{
root_fs_names = str;
return 1;
}
void __init init_rootfs(void)
{
if (IS_ENABLED(CONFIG_TMPFS) && !saved_root_name[0] &&
(!root_fs_names || strstr(root_fs_names, "tmpfs")))
is_tmpfs = true;
}
I thought I'd dealt with this back in commit 6e19eded3684? Hmmm, looks like it
might need something like:
diff --git a/init/do_mounts.c b/init/do_mounts.c
index 7058e14ad5f7..4b4e1ffa20e1 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -665,7 +665,7 @@ struct file_system_type rootfs_fs_type = {
void __init init_rootfs(void)
{
- if (IS_ENABLED(CONFIG_TMPFS) && !saved_root_name[0] &&
- (!root_fs_names || strstr(root_fs_names, "tmpfs")))
+ if (IS_ENABLED(CONFIG_TMPFS) && (!root_fs_names ? !saved_root_name[0] :
+ strstr(root_fs_names, "tmpfs"))
is_tmpfs = true;
}
> Maybe omitting root= was impacting on mounting
> the real root filesystem. Will get that information.
I know some old bootloaders hardwire in the command line so people can't
_remove_ the root=.
The reason I didn't just make rootfs always be tmpfs when CONFIG_TMPFS is
enabled is:
A) It uses very slightly more resources, and the common case is overmounting an
empty rootfs. (And then hiding it from /proc/mounts so people don't ask too many
questions.)
B) Some embedded systems use more than 50% of the system's memory for initramfs
contents, which the tmpfs defaults won't allow (fills up at 50%), and I'm not
sure I ever hooked up I don't think I ever hooked up rootflags= ala
root_mount_data to the initramfs mount? (If so, setting size= through that
should work...)
> Intuitively, given that root= is consumed for example by dracut, it seems
> a safer choice to have an option to explicitly choose the desired filesystem.
Sounds like a dracut issue. Have you used dracut in a system running from initramfs?
Lots of systems running from initramfs already DON'T have a root=, so you're
saying dracut being broken when there is no root= is something to work around
rather than fix in dracut, even though it's been easy to create a system without
a root= for a decade and a half already...
> Roberto
Rob
