[lxc-devel] [PATCH] c/r: force users to provide a fresh directory for criu images

[Serge Hallyn]

Quoting Tycho Andersen (tycho.andersen at canonical.com):
> On Wed, Apr 22, 2015 at 01:16:08PM -0600, Tycho Andersen wrote:
> > CRIU can get confused if more than one c/r is done in the same directory, so we
> > should require lxcapi so that it refuses to dump to a directory with criu
> > images already in it.
> 
> Hmm, actually I'm not sure this is the best way to do this. If users
> (e.g. LXD) use some sort of mechanism to generate a temporary
> directory name we could race if the same name is tried twice in a row.

?

You mean if they use something like mkstemp and two threads get the
same name from it?  (that shouldn't happen)

> Instead, maybe it's just best to stat() for the key criu image file
> (inventory.img), and die if it's there.
> 
> Thoughts?
> 
> > This won't help if the user copies a checkpoint over another, but at least the
> > common case will be caught.
> > 
> > Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
> > ---
> >  src/lxc/lxccontainer.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/src/lxc/lxccontainer.c b/src/lxc/lxccontainer.c
> > index dbcee99..4a290f1 100644
> > --- a/src/lxc/lxccontainer.c
> > +++ b/src/lxc/lxccontainer.c
> > @@ -3687,8 +3687,13 @@ static bool do_lxcapi_checkpoint(struct lxc_container *c, char *directory, bool
> >  	if (!criu_ok(c))
> >  		return false;
> >  
> > -	if (mkdir(directory, 0700) < 0 && errno != EEXIST)
> > +	if (mkdir(directory, 0700) < 0) {
> > +		if (errno == EEXIST)
> > +			ERROR("please use a new directory for criu state");
> > +		else
> > +			SYSERROR("mkdir failed");
> >  		return false;
> > +	}
> >  
> >  	if (!dump_net_info(c, directory))
> >  		return false;
> > -- 
> > 2.1.4
> > 
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