Thanks for the response, Josh. Sorry I didn't send in my version info with the initial message. On Mon, Jul 16, 2012 at 6:43 PM, Josh Durgin <josh.durgin@xxxxxxxxxxx> wrote: > On 07/16/2012 12:59 PM, Travis Rhoden wrote: >> >> Hi folks, >> >> I've made this mistake a couple of times now (completely my fault, >> when will I learn?), and am wondering if a bit of protection can be >> put in place against user errors. > > > Yeah, we've been working on advisory locking. The first step is > just adding an option to lock via the rbd command line tool, so you > could script lock/map and unmap/unlock. > > This is described a little more in this thread: > > http://comments.gmane.org/gmane.comp.file-systems.ceph.devel/7094 I had in fact seen this. Looks like the advisory locking is targeted for 0.49. That's great! Thanks for reminding me of it. I'll look forward to it. > > >> I mapped a device "rbd map", then formatted and and mounted the device >> ("mkfs.extf /dev/rbd0..., mount /dev/rbd0..."). Then sometime later, >> I want to remove the RBD device. Stupidly, I do the "rbd unmap" >> command before I unmount the device. The kernel doesn't really care >> for this. Or more accurately, I can't remap that same RBD because I >> run into: >> >> kernel: [2248653.941688] sysfs: cannot create duplicate filename >> '/devices/virtual/block/rbd0' >> .... >> kernel: [2248653.941833] kobject_add_internal failed for rbd0 with >> -EEXIST, don't try to register things with the same name in the same >> directory. >> >> At this point, the "rbd map" command hangs indefinitely (producing the >> logs from above). Ctrl-C does exit out, though. But if I try to fix >> my mistake by doing the unmount now, I get the error: >> >> umount: device is busy. >> >> So really I get stuck. I can't unmount without the device, and I >> can't remap the device to the old block device. I have to reboot to >> clean up and move on. > > > A similar issue was fixed in 3.4 (see > http://tracker.newdream.net/issues/1907). > What kernel are you using? 3.2 had a nasty possibility of preventing > further operations if mapping hung while trying to connect to the > monitors. I am using the stock Ubuntu 12.04 kernel, which is in fact 3.2 Good point. So, the only way for me to get the updates you mentioned is to upgrade to a 3.4 kernel, correct? > > >> I imagine other bad things can happen with the block device goes away >> out from under the mount point. Any way the "rbd unmap" command can >> detect when the device is in use or mounted and inform the user? > > > Before actually unmapping the device, rbd unmap could check if it was > present in mtab. If it's being used as a raw block device and not > mounted or you created and used your own device node this wouldn't > help, but it would be better than nothing. That would be awesome. Every little bit helps. > > Josh -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
