Re: dracut is too "clever" at identifying modules to exclude.

[Neil Brown <neilb-IBi9RG/b67k@public.gmane.org>]

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Harald Hoyer <harald-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> writes:

> On 12.10.2015 05:02, Neil Brown wrote:
>> 
>> If I have booted a kernel with md/raid built in (no modules) and
>> I use dracut to build the initramfs for a different kernel which
>> has the md code compiled as separate modules, then it does not include
>> the required md modules in the initramfs.
>> 
>> As a particular instance this happen when the root filesystem is on
>> RAID0.  The 'raid0.ko' module is not included and boot fails.
>> 
>> https://bugzilla.opensuse.org/show_bug.cgi?id=935993
>> 
>> This only happens when 'host-only' is selected (which is the default for
>> openSUSE).
>> 
>> the modules.d/90mdraid/module-setup.sh code calls
>> 
>>     instmods =drivers/md
>> 
>> instmods calls
>>    module_is_host_only "raid0"
>> and this incorrectly fails.
>> 
>> If raid0.ko didn't have any alias this would succeed, but it does.
>> 
>> $ modinfo -F alias raid0
>> md-level-0
>> md-raid0
>> md-personality-2
>
> Huh? Is the module not loaded?

No, because the running kernel has "md/raid built in (no modules)".

Thanks,
NeilBrown

>
>> 
>> However these aliases don't appear in any modalias file in /sys/devices,
>> in /proc/crypto, or in /proc/modules.
>> 
>> Maybe you could parse /proc/mdstat..
>> 
>> if [ -f /proc/mdstat ]; then
>>   while read _d _c _a _m _x; do
>>    if [ "$_c" = ':' -a "$_a" = 'active' ]; then
>>       host_modalias["md-$_m"]=1
>>    fi
>>   done < /proc/mdstat
>> fi
>> 
>> but it all seems rather fragile.  There are probably other modules that
>> might miss out accidentally. dm?
>> 
>> Do we really need the host_modalias stuff?
>> 
>> Thanks,
>> NeilBrown
>> 

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