On Sun, Apr 29, 2012 at 02:57:11PM -0400, Theodore Ts'o wrote: > > It would be useful if there was a way to be able to determine, > conclusively, whether a partciular block is in device, and how (i.e., > whether some process has the block open, or it is mounted, or it is > being used as part of a device mapper, or md setup, etc.). > > That way when users complain that trying to open a particular device in > exclusive mode returns EBUSY, there's an easy way to figure out why this > might be the case. The lsof program works for the first method, but it > doesn't help for the other cases; and using /proc/mounts doesn't help if > the block device is mounted in some other namespace; you could try to > look at /proc/*/mounts for every single process, but that's exquisitely > painful, and only works for block devices used by mounted file systems. > > So the question is, what's the best way of doing this? Adding a new > flags field after the block device name in /proc/partitions would be the > simplest, but that might break some userspace programs that aren't > expecting it. There's the holders directory in sysfs, i.e., > /sys/dev/block/8:5/holders/*, but that only seems to only record usage > by device mapper. > > Should we extend the holders directory in the block device directory in > sysfs? Add a new directory to record when a file system might be > mounted? Add a new /proc file? Don't we already have a way to do all of this through sysfs today? How does gnome/kde handle this when you try to eject a device with an active mount that is busy? It pops up a dialog telling you why this can't be ejected, and which device it is. I think everything you want is already there, if not, perhaps dm just needs to add a few more sysfs links to tie it all together. And no, no more /proc files for filesystem stuff like this, that way lies madness. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
