On Wed, Aug 31, 2011 at 01:18:33PM -0500, Serge Hallyn wrote:
> Hi,
>
> I'm seeing an issue with udev and libvirt-lxc. Libvirt-lxc creates
> /dev/ptmx as a symlink to /dev/pts/ptmx. When udev starts up, it
> checks the device type, sees ptmx is 'not right', and replaces it
> with a 'proper' ptmx.
>
> In lxc, /dev/ptmx is bind-mounted from /dev/pts/ptmx instead of being
> symlinked, so udev sees the right device type and leaves it alone.
>
> A patch like the following seems to work for me. Would there be
> any objections to this?
>
> >From 4c5035de52de7e06a0de9c5d0bab8c87a806cba7 Mon Sep 17 00:00:00 2001
> From: Ubuntu <ubuntu@domU-12-31-39-14-F0-B3.compute-1.internal>
> Date: Wed, 31 Aug 2011 18:15:54 +0000
> Subject: [PATCH 1/1] make ptmx a bind mount rather than symlink
>
> udev on some systems checks the device type of /dev/ptmx, and replaces it if
> not as expected. The symlink created by libvirt-lxc therefore gets replaced.
> By creating it as a bind mount, the device type is correct and udev leaves it
> alone.
>
> Signed-off-by: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>
> ---
> src/lxc/lxc_container.c | 20 ++++++++++----------
> 1 files changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
> index e425328..6991aec 100644
> --- a/src/lxc/lxc_container.c
> +++ b/src/lxc/lxc_container.c
> @@ -543,18 +543,18 @@ static int lxcContainerPopulateDevices(void)
> }
> }
>
> + dev_t dev = makedev(LXC_DEV_MAJ_TTY, LXC_DEV_MIN_PTMX);
> + if (mknod("/dev/ptmx", S_IFCHR, dev) < 0 ||
> + chmod("/dev/ptmx", 0666)) {
> + virReportSystemError(errno, "%s",
> + _("Failed to make device /dev/ptmx"));
> + return -1;
> + }
> +
> if (access("/dev/pts/ptmx", W_OK) == 0) {
> - if (symlink("/dev/pts/ptmx", "/dev/ptmx") < 0) {
> - virReportSystemError(errno, "%s",
> - _("Failed to create symlink /dev/ptmx to /dev/pts/ptmx"));
> - return -1;
> - }
> - } else {
> - dev_t dev = makedev(LXC_DEV_MAJ_TTY, LXC_DEV_MIN_PTMX);
> - if (mknod("/dev/ptmx", S_IFCHR, dev) < 0 ||
> - chmod("/dev/ptmx", 0666)) {
> + if (mount("/dev/pts/ptmx", "/dev/ptmx", "ptmx", MS_BIND, NULL) < 0) {
> virReportSystemError(errno, "%s",
> - _("Failed to make device /dev/ptmx"));
> + _("Failed to bind-mount /dev/ptmx to /dev/pts/ptmx"));
> return -1;
> }
> }
Hum, if we do a mount, I would expect to do an unmount somewhere.
Also the lifetime of the mount and the symlink is really different,
a recursive remove when destroying the container would lead to no
resource leak but I think that for a bind mount we absolutely have
to clean it up.
Daniel
--
Daniel Veillard | libxml Gnome XML XSLT toolkit http://xmlsoft.org/
daniel@xxxxxxxxxxxx | Rpmfind RPM search engine http://rpmfind.net/
http://veillard.com/ | virtualization library http://libvirt.org/
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