On Tuesday October 28, kay.sievers@xxxxxxxx wrote: > > But in different places. > > Debian has /etc/udev/rules > > openSUSE has /lib/udev/rules > > > > I love standards. There are so many to choose from. :-) > > They are all valid and needed. You should install in > /lib/udev/rules.d/ if the rule is not supposed to be edited by the > user. Clearer now. Thanks. > > I notice that 'md' > > devices don't seem to disappear. Maybe that is because /sys/block/mdX > > never disappears (last time I tried it was too racy). > > It stays because the md kernel device lifetime rules are kind of > broken regarding hotplug setups. Similar issue why md needs all the > static nodes in /dev too to create a device. > > > Would there be any way to get udev to delete devices when > > /sys/block/mdX/md/array_state > > becomes 'clear' (presumably on a CHANGE event) ?? > > What would be the reason to leave the kernel block device around? > Can't you just remove it like any other subsytem in the kernel does. > That would just remove the node, all links and update userspace to > reflect the change. I tried some time ago. It was hard. md devices magic appear when you tried to open the device-special file. I need some sort of locking to prevent that creation while I'm destroying the old device. But when I was trying this (quite some months ago) the locking around do_open was fairly difficult to follow. I don't remember the exact issues, but I gave up. What would happen was that when the md device disappear, udev would try to open it (I think) and make it reappear again. Sometimes with an oops. I think I avoided some of that by sending the DELETE event well before the device was actually deleted ... or something. But it was still far from perfect. Maybe I should try again. > > There is currently no "change" event that could tell to remove a > device node in /dev while we still have a kernel device around. And > you would need to convince me that this is really needed, and why md > is so special here. :) md is a bit 'special', but not quite unique. I think 'loop' now works the same way as md in terms of devices magically appearing on open. Maybe I can see how it was made to work for that case. Thanks Kay, NeilBrown -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
