Re: [libvirt] [PATCH v2 5/8] LXC: Creating devices for container on host side

On Fri, May 10, 2013 at 05:58:14PM +0800, Gao feng wrote: > user namespace doesn't allow to create devices in > uninit userns. We should create devices on host side. > > Signed-off-by: Gao feng <gaofeng(a)cn.fujitsu.com&gt; > --- > src/lxc/lxc_container.c | 47 +++++++---------------------- > src/lxc/lxc_controller.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 87 insertions(+), 37 deletions(-) > diff --git a/src/lxc/lxc_controller.c b/src/lxc/lxc_controller.c > index e9b90bf..2072e9a 100644 > --- a/src/lxc/lxc_controller.c > +++ b/src/lxc/lxc_controller.c > @@ -1103,6 +1103,73 @@ cleanup: > } > > > +static int virLXCControllerPopulateDevices(virLXCControllerPtr ctrl) > +{ > + size_t i; > + int ret = -1; > + char *ptmx = NULL; > + char *path = NULL; > + const struct { > + int maj; > + int min; > + mode_t mode; > + const char *path; > + } devs[] = { > + { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_NULL, 0666, "/dev/null" }, > + { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_ZERO, 0666, "/dev/zero" }, > + { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_FULL, 0666, "/dev/full" }, > + { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_RANDOM, 0666, "/dev/random" }, > + { LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_URANDOM, 0666, "/dev/urandom" }, > + }; > + > + /* Populate /dev/ with a few important bits */ > + for (i = 0 ; i < ARRAY_CARDINALITY(devs) ; i++) { > + if (virAsprintf(&path, "/proc/%llu/root/%s", > + (unsigned long long)ctrl->initpid, > + devs[i].path) < 0) { > + virReportOOMError(); > + goto out; > + } > + > + dev_t dev = makedev(devs[i].maj, devs[i].min); > + if (mknod(path, S_IFCHR, dev) < 0 || > + chmod(path, devs[i].mode)) { > + virReportSystemError(errno, > + _("Failed to make device %s"), > + devs[i].path); > + goto out; > + } > + } > + > + if (virAsprintf(&ptmx, "/proc/%llu/root/dev/pts/ptmx", > + (unsigned long long)ctrl->initpid) < 0) { > + virReportOOMError(); It is really non-obvious that this code is not being run until the container has started. IMHO rather than playing games with the /proc/$PID/root/dev link, you should make the lxc_controller.c code responsible for mounting the /dev tmpfs somewhere, and populate it before any of the lxc_container code even runs. Then the lxc_container code can simply MS_MOVE the pre-populate /dev to the right place when it starts.