Bug#489850: multipath-tools-boot: fails to boot from a slow devices

[Janusz Dziemidowicz]

2008/7/25 Guido Günther <agx at sigxcpu.org>:
> On Fri, Jul 25, 2008 at 04:03:01AM +0200, Janusz Dziemidowicz wrote:
> [..snip..]
>> Unfortunately it does not work. /dev/mapper/wwid entry is not created.
>> When I launch this manually from within initrd shell with -v2 I get:
>> : failed to get sysfs information
> Hmmm.weird - seems there's s.th. in multipath's sysfs code broken - I'll
> check that once I have access to a MP system myself again. What about:

Maybe those would help:
http://git.kernel.org/gitweb.cgi?p=linux/storage/multipath-tools/.git;a=commit;h=88f88d11ecee7d753e9b43d67001d58c56789eb1
http://git.kernel.org/gitweb.cgi?p=linux/storage/multipath-tools/.git;a=commit;h=3aaecad682efef27ce6196c6d29db4cb93c9f2fb
Didn't check it myself, will try next time I have some MP server for tests.

> ACTION=="add", SUBSYSTEM=="block", RUN+="/sbin/multipath -v0 %N"

No, this does not work, udev manual says about %N:
"The name of a created temporary device node to provide access to the
device from a external program before the real node is created."
So this sounds for me rather dangerous to use, not sure what is this
temporary device and if multipath accepts it (I don't see why it
shouldn't, but it also should accept major:minor...).

> This should hopefully do the trick. As a last resort:
>
> ACTION=="add", SUBSYSTEM=="block", RUN+="/sbin/multipath -v0 /dev/%k"
>
> should work too. Could you try that?

This works (although I see that the cleanest solution would be to use
major:minor).

If I understand correctly, you want to get rid of
/usr/share/initramfs-tools/scripts/local-top/multipath completely.
I've tried to do that (with the /dev/%k trick) and it isn't so simple.
There is a problem with loading dm-multipath module, it is not loaded
automatically when needed, so /sbin/multipath fails if it was not
loaded before udev event handlers from RUN were called. One solution
was to add dm-multipath to /etc/initramfs-tools/modules, but I don't
think it is the nicest way.

-- 
Janusz Dziemidowicz
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