On Fri, May 11, 2012 at 10:04:24PM -0400, Stefan Berger wrote:
On 05/11/2012 12:48 PM, Daniel P. Berrange wrote:
From: "Daniel P. Berrange"<berrange@redhat.com>
Both /proc and /sys may have sub-mounts in them from the host OS. We must explicitly unmount them all before mounting the new instance over that location. If we don't then /proc/mounts will show the sub-mounts as existing, even though nothing will be able to access them, due to the over-mount.
Signed-off-by: Daniel P. Berrange<berrange@redhat.com> --- src/lxc/lxc_container.c | 61 ++++++++++++++++++++++++++++++++++++----------- 1 file changed, 47 insertions(+), 14 deletions(-)
@@ -1054,13 +1057,36 @@ static int lxcContainerUnmountOldFS(void) qsort(mounts, nmounts, sizeof(mounts[0]), lxcContainerChildMountSort);
+ *mountsret = mounts; + *nmountsret = nmounts; + ret = 0; + +cleanup: + endmntent(procmnt); + return ret; +} + +static int lxcContainerUnmountSubtree(const char *prefix, + bool isOldRootFS) +{ + char **mounts = NULL; + size_t nmounts = 0; + size_t i; + int saveErrno; + const char *failedUmount = NULL; + int ret = -1; + + VIR_DEBUG("Unmount subtreee from %s", prefix); + + if (lxcContainerGetSubtree(prefix,&mounts,&nmounts)< 0) + return -1; for (i = 0 ; i< nmounts ; i++) { VIR_DEBUG("Umount %s", mounts[i]); if (umount(mounts[i])< 0) { char ebuf[1024]; failedUmount = mounts[i]; saveErrno = errno; - VIR_WARN("Failed to unmount '%s', trying to detach root '%s': %s", + VIR_WARN("Failed to unmount '%s', trying to detach subtree '%s': %s", failedUmount, mounts[nmounts-1], virStrerror(errno, ebuf, sizeof(ebuf))); break;
This may be an existing issue - should the code not try to continue unmounting rather than break'ing follwing error above? Would leaving the loop here leave stale mounts behind?
In this scenario, if we fail to unmount any path, then code later will check 'failedUmount' and unmount2(MNT_DETACH) the entire root filesystem. So any mounts are lazily cleaned up by the kernel & inaccessible to the container. That said, we probably could continue trying to unmount other dirs, just to avoid wasting kernel memory from the detached mount tree. 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 :|