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From: Kevin Hilman <khilman@baylibre.com>
Newsgroups: linux.debian.bugs.dist,linux.debian.kernel
Subject: Bug#892407: initramfs-tools: scripts/local: ignore /dev/ram*
Date: Fri, 09 Mar 2018 20:30:02 +0100
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On Thu, Mar 8, 2018 at 6:37 PM, Ben Hutchings <ben@decadent.org.uk> wrote:
> On Thu, 2018-03-08 at 17:08 -0800, Kevin Hilman wrote:
>> I'm not sure exactly what you're referring to, so I guess that means no.
>
> Aren't you using LAVA in conjunction with kernelci?  That's where I've
> seen this odd usage of "root=/dev/ram0" before.

Yes, this came up in the contect of kernelCI.

>> I'm just trying to avoid an unnecessary delay when "root=/dev/ram*" is
>> (mistakenly) used on the command-line when passing in the debian
>> ramdisk.  If that happens, it eventually falls through to the
>> initramfs shell, but not before trying 30 times (with a "sleep 1"
>> between each) to find another ramdisk on /dev/ramX
>
> I'm pretty sure "break" does what you need.

Well, break does what you describe, but not exactly what I need.  I'm
trying to workaround the (mis)use of root=/dev/ramX on the
commandline.  If I could add stuff to the kernel command-line, I would
instead just remove the "root=/dev/ramX" rather than add
"break=premount", but I'm trying to solve the problem for LAVA labs
that we don't control, so we cannot change all the device-types out
there and remove "root=/dev/ram0".

So, back to the patch at hand...

Is there ever a usecase for the debian initrd.img to switch_root to
another initrd/ramdisk?

If so, then my proposed patch is invalid.  If not, then it's a nice
optimization and fixup for (mis)use of root=/dev/ram in conjuction
with an existing initrd/ramdisk.

Kevin