On Mon, Sep 19, 2011 at 11:38:27AM -0500, Serge E. Hallyn wrote: > It'd be worth asking Ram about that. It's possible he was being overly > cautious as this was new ground, but it seems likely there was a good > reason for it. > > Heck, rather than guessing, cc:ing Ram. Ram, can you explain the need > for all three parts of that check at pivot_root(): > > + if (IS_MNT_SHARED(old_nd.mnt) || > + IS_MNT_SHARED(new_nd.mnt->mnt_parent) || > + IS_MNT_SHARED(user_nd.mnt->mnt_parent)) > > ?
digging through my long lost memory..... hmm..ok here is my recollection. Pivot root involves two move-mount operations. We had decided to not allow moving a mount that is currently below a shared mount. The reason being; it will lead to unmount of all the trees under their corresponding peer mounts. Since pivot_root involves two atomic move-mount operations, and since moving mounts below shared mounts is a invalid operation, the pivot_root operation below shared mounts becomes a invalid operation. RP > > thanks, > -serge > > Quoting Marios Titas (redneb8...@gmail.com): > > It seems that the kernel commit > > 2144440327fa01b2f3f65e355120a78211685702 from 2005 is the culprit. > > It's the commit that implemented mount --move in presense of shared > > mounts. It added a check in fs/namespace.c that makes pivot_root fail > > when the old root is marked as a shared mount. I don't understand the > > reason for that. > > > > > > On Mon, Sep 19, 2011 at 09:35, Serge Hallyn <serge.hal...@canonical.com> > > wrote: > > > Quoting Marios Titas (redneb8...@gmail.com): > > >> Hi list, > > >> > > >> I just ran into this problem: If you do > > >> # mount --make-shared / > > >> to mark / as a shared mount then lxc-start fails when you have > > >> specified a lxc.rootfs in the configuration file. The error that > > >> lxc-start gives is the following: > > >> Invalid argument - pivot_root syscall failed > > >> Is this the normal behavior or is this a kernel bug? > > > > > > It is normal behavior. Perhaps lxc should fall back to chroot when > > > pivot_root fails. > > > > > > -serge > > > ------------------------------------------------------------------------------ All the data continuously generated in your IT infrastructure contains a definitive record of customers, application performance, security threats, fraudulent activity and more. Splunk takes this data and makes sense of it. Business sense. IT sense. Common sense. http://p.sf.net/sfu/splunk-d2d-oct _______________________________________________ Lxc-users mailing list Lxc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/lxc-users
