initrd/initramfs problem

Ed Martini
2005-03-17T00:50:06Z

What fails is when CONFIG_BLK_DEV_INITRD and CONFIG_INITRAMFS_SOURCE are
both set. I realize (now) that I don't need initrd at all, and
initramfs works fine by itself, as you have tested. It seems that the
kernel may need some exclusion between these two mechanisms while the
difference is sorted out.

I'm not totally up on Kconfig files, but maybe something like this in
drivers/block/Kconfig:

config INITRAMFS_SOURCE
string "Initramfs source file(s)"
default ""
depends on BLK_DEV_INITRD=n

Regarding the documenation it would have been helpful to me if
Documentation/initrd.txt had a reference to
Documentation/early-userspace/README. I'm not sure who maintains that
directory, or I'd send a suggestion. tldp.org?

THX
Ed Martini

Original context:
http://www.linux-mips.org/archives/linux-mips/2005-03/index.html

Ralf Baechle wrote:

>On Tue, Mar 15, 2005 at 02:37:45PM -0800, Ed Martini wrote:
>
>
>>Also, unless you move the location of .init.ramfs, it gets freed twice,
>>leading to a panic.
>>
>>
>
>Interesting one. When I tested the code recently it did work for me and
>it shouldn't have changed since. The way this is supposed to work is
>by setting the page_count to 1 by using set_page_count and unmarking the
>page as reserved, so after that point a free_page should actually succeed -
>even if done twice as you've observed, first in populate_rootfs then
>once more in free_initmem.
>
>It seems a frighteningly bad idea though since it relies on no memory
>from the initrd range being allocated between the two calls - or it would
>end being freed by force, in use or not. On startup Linux tends to
>allocate memory starting from high address towards low addresses which
>must be why we usually get away with this one.
>
>
>
>>From the documentation alone it's impossible to figure out how to build
>>your initramfs. In various places the docs refer to the initial
>>executable as /linuxrc, /kinit, /init, and possibly others. If you read
>>init/main.c you see that for an initramfs, your initial process will be
>>started from /init.
>>
>>
>
>I guess I read the code so I didn't notice the lacking qualities of the
>documentation ...
>
> Ralf
>
>