[dm-devel] Fwd: 2.6.25-rc1 patch prevents booting on LVM-based devices

[Chuck Lever]

Begin forwarded message:
> From: Chuck Lever <chuck.lever at oracle.com>
> Date: February 20, 2008 10:50:01 AM EST
> To: dm-devel at redhat.com
> Subject: 2.6.25-rc1 patch prevents booting on LVM-based devices
>
> Hello-
>
> I've got a Fedora 8 x86 test system that uses LVM volumes for all  
> it's file systems except /boot.  After commit bdc80787, 2.6.24+  
> doesn't boot on this system -- the LVM volume scan during start-up  
> can no longer find any physical volumes on the system.
>
> I'm not sure whether this is an LVM issue, or something else is  
> breaking during system init which prevents the LVM scan from  
> working.  I need some help troubleshooting the problem.

Interestingly, if I build a non-tickless kernel, the problem goes away.

> bdc80787 is:
>
> commit bdc807871d58285737d50dc6163d0feb72cb0dc2
> Author: H. Peter Anvin <hpa at zytor.com>
> Date:   Fri Feb 8 04:21:26 2008 -0800
>
>     avoid overflows in kernel/time.c
>
>     When the conversion factor between jiffies and milli- or  
> microseconds is
>     not a single multiply or divide, as for the case of HZ == 300,  
> we currently
>     do a multiply followed by a divide.  The intervening result,  
> however, is
>     subject to overflows, especially since the fraction is not  
> simplified (for
>     HZ == 300, we multiply by 300 and divide by 1000).
>
>     This is exposed to the user when passing a large timeout to poll 
> (), for
>     example.
>
>     This patch replaces the multiply-divide with a reciprocal  
> multiplication on
>     32-bit platforms.  When the input is an unsigned long, there is  
> no portable
>     way to do this on 64-bit platforms there is no portable way to  
> do this
>     since it requires a 128-bit intermediate result (which gcc does  
> support on
>     64-bit platforms but may generate libgcc calls, e.g.  on 64-bit  
> s390), but
>     since the output is a 32-bit integer in the cases affected,  
> just simplify
>     the multiply-divide (*3/10 instead of *300/1000).
>
> and so on...
>
> --
> Chuck Lever
> chuck[dot]lever[at]oracle[dot]com
>
>
>

--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com