On Thu, Jan 15, 2015 at 09:56:05AM +0100, Alexander Larsson wrote: > This is a bit of a weird request, but I'm working on an app sandboxing > system where each container gets /usr read-only bind mounted from a > hardlinked tree. When i update the /usr tree I write the new tree to a > different directory, which avoids affecting any currently running apps > against the old one. > > However, after updating I'd like to clean out the old version if it is > not in use. I had a plan for this: > 1) Move the old usr to a "has been deleted" location > 2) Try to remove a file inside the user (say ".ref") which the app when > running has bind-mounted somewhere > 3) if the remove returned EBUSY, then the usr is in use. > > However, with the recent changes to the semantics in this area this > doesn't work. The remove always succeeds even if the file is mounted in > some other namespace. > > I realize that this is better semantics in general, but that was a quite > useful hack. Is there any other similar way i can detect that something > is in use in "any other namespace". Presumably you want something more efficient than scaning /proc/$PID in the host OS ? eg you read /proc/$PID/mounts for each process, then iterate stating /proc/$PID/root/<mount> to lookup the st_dev+st_inode of the mount location to see if the one you care about still exists in any process ? Not really going to scale nicely with large numbers of $PIDs, so perhaps you could short circuit by keeping track of your container pid leaders ? Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
