On Apr 7, 2009, at 5:26 PM, NeilBrown wrote:
On Tue, April 7, 2009 10:16 pm, Doug Ledford wrote:On Apr 7, 2009, at 2:05 AM, Goswin von Brederlow wrote:Doug Ledford <dledford@xxxxxxxxxx> writes:Originally, mdadm used /var/run/mdadm/mdadm.map file to store the temporary mappings of incrementally added devices to device names.Unfortunately, this breaks incremental assembly if used early in thebooting process. Specifically, root may still be read only. Since incremental assembly is largely a udev specific feature, and udevneeds a writable /dev tmpfs mount even when root is still read only, it's safer to put our mdadm.map file in /dev/md so that we can writeto the map file no matter how early in the boot process we are attempting to use incremental assembly.What about /lib/init/rw?Never heard of it. But, if / is read-only, why wouldn't that also be read-only?because a tmpfs was mounted there. It's probably a Debian-specific thing.Why /var/run cannot be mounted from tmpfs nice and early too I don't know..I understand that some people think /var/run needs to persist across reboots to preserve ownership of directories, but they are wrong :-) /var/run should be a tmpfs mount point very early.
I disagree. At least in our case, the reason that /var/run is a real directory is not to preserve ownerships (although it does do that as well), but to preserve security context for SELinux.
I have to say that putting the map file in /dev feels very icky to me. It isn't a device, and so doesn't belong in /dev. If we go around putting things somewhere convenient rather than where they belong, we quickly end up with a mess.
If that's the case, then all of udev's library data in /dev/.udev doesn't belong there either. And as much as this may not be a device, it is in fact device specific in that it maps one device to another. It really is right along the lines of the data udev stores in .udev, so I don't see the ickyness.
So while it might be very pragmatic, I am currently dis-inclined to take the patch. Can you try asking your boot-script people to make /var/run be an early tmpfs ???
I'm betting that this stands 0 chance for F11 anyway, and I'm betting it would be a rather long, uphill fight to get them to agree to this period.
-- Doug Ledford <dledford@xxxxxxxxxx> GPG KeyID: CFBFF194 http://people.redhat.com/dledford InfiniBand Specific RPMS http://people.redhat.com/dledford/Infiniband
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