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Re: [Libvir] [RFC] 3 of 4 Linux Container support



On Thu, Mar 20, 2008 at 12:11:39PM -0400, Daniel Veillard wrote:
> On Wed, Mar 19, 2008 at 11:14:59PM -0700, Dave Leskovec wrote:
> > This patch adds the lxc_driver source files.
> [...]
> > +static int lxcCheckContainerSupport( void )
> > +{
> > +    int rc = 0;
> > +    int flags = CLONE_NEWPID|CLONE_NEWNS|CLONE_NEWUTS|CLONE_NEWUSER|
> > +        CLONE_NEWIPC|SIGCHLD;
> > +    int cpid;
> > +    char *childStack;
> > +    char *stack;
> > +    int childStatus;
> > +
> > +    stack = malloc(getpagesize() * 4);
> > +    if(!stack) {
> > +        DEBUG0("Unable to allocate stack");
> > +        rc = -1;
> > +        goto check_complete;
> > +    }
> > +
> > +    childStack = stack + (getpagesize() * 4);
> > +
> > +    cpid = clone(lxcDummyChild, childStack, flags, NULL);
> > +    if ((0 > cpid) && (EINVAL == errno)) {
> > +        DEBUG0("clone call returned EINVAL, container support is not enabled");
> > +        rc = -1;
> 
>   haha, I would have expected a checking of /proc or something similar.
> That test could still fail, say if the kernel started to disagree on
> stack of only 4 pages for example. 

If there was insufficient mem it would return ENOMEM. The EINVAL errors are all
related to invalid flags, so this is a reasonable check.

Dan.
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