On Mon, Jul 25, 2011 at 12:12, Zdenek Kabelac <zkabelac@xxxxxxxxxx> wrote: > Dne 25.7.2011 02:18, Kay Sievers napsal(a): >> On Fri, 2011-07-22 at 16:22 +0200, Zdenek Kabelac wrote: >> >>> For now udev recieves 3 event for removal of DM logical volumes. (1 for >>> bdi and 2 for same block kobject). Reason is dm device generates its >>> own kobject event with approriate env parameter and block layer sends >>> another KOBJ_REMOVE event on its own unconditionaly for the same >>> kobject. As for now only the kobject cleanup checks that the REMOVE >>> event has been already sent and avoids duplicate REMOVE event. >> >>> The patch for kobject_uevent_env() which has been testing for duplicate >>> REMOVE event did not passed into the mainline (yet?): >> >> No, it's wasn't merged. Subsystems should really not send their own >> 'add' or 'remove' events. These are properties of the driver core. >> >>> I'm proposing alternative way around to always use kobject cleanup >>> routine for sending REMOVE event if it was not send by the module - so >>> it makes the code few lines shorter. >> >> The events the core creates are only sent out at release() not at del(), >> so we would delay 'remove' events when we keep the device pinned but >> it's not valid anymore. We can not do that today, we would need to move >> the core-created 'remove' events to del(). >> >> For device-mapper, I would prefer to add a '.dev_uevent' callback to the >> 'block' class let this callback check 'struct block_device_operations' >> for a possibly specified '.uevent' callback and call it. >> >> Then have 'dm_blk_dops' add '.uevent' and let the core call into the dm >> code to the needed properties to the 'remove' event, instead of sending >> its own, and see the duplication. > > Sounds like complex solution I don't think so, It's clean, ~30 lines long, and technically correct, I expect. > maybe it would be easier to just register some > environment variable on dm code side - like kobject_add_env() - so it would > take envs from this internal kobject list and after sending uevent it would > implicitly clear this list. So we would keep allocated per-event-type variables in the kobject, to send when 'remove' is finally called? The callbacks are just much simpler , I guess. > So in dm case dm-uevent would just register env(cookie) for KOBJ_REMOVE and > would left kobject_uevent() on block layer ? > > Also I'm aware that remove event would be delayed by leaving it on > kobject_cleanup(), but since you mentioned 'del()' as a better place - why not > move this implicit uvent call there. It's probably not wrong to do that, but I don't remember now why we added it to release() that time. > since most kernel driver writers > probably do not want to be bothered with uvents? I guess, most drivers use devices not raw kobjects, which send events on their own, and don't need anything here. Kay -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
