[CRIU] [PATCH] scripts: set CRIU_IMAGE_DIR when running scripts

[Tycho Andersen]

On Tue, Aug 12, 2014 at 07:46:52PM +0400, Pavel Emelyanov wrote:
> On 08/12/2014 07:07 PM, Tycho Andersen wrote:
> > Hi Pavel,
> > 
> > On Tue, Aug 12, 2014 at 06:31:45PM +0400, Pavel Emelyanov wrote:
> >> On 08/12/2014 06:22 PM, Tycho Andersen wrote:
> >>> When doing a restore for LXC, we store some other metadata (which bridge a veth
> >>> was on) in the image directory so that the restore script can correctly unlock
> >>> a network device and attach it to the right interface. This patch is needed so
> >>> that the script can find this metadata.
> >>>
> >>> Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
> >>> ---
> >>>  util.c | 7 +++++++
> >>>  1 file changed, 7 insertions(+)
> >>>
> >>> diff --git a/util.c b/util.c
> >>> index a180ea5..4ff8768 100644
> >>> --- a/util.c
> >>> +++ b/util.c
> >>> @@ -460,6 +460,7 @@ int run_scripts(char *action)
> >>>  {
> >>>  	struct script *script;
> >>>  	int ret = 0;
> >>> +	char image_dir[PATH_MAX];
> >>
> >> Odd enough, but we have a magic constant PSFDS that says "how much 
> >> would the path to /proc/self/fd/%d occupy on the stack" :)
> >>
> >>>  
> >>>  	pr_debug("Running %s scripts\n", action);
> >>>  
> >>> @@ -468,6 +469,12 @@ int run_scripts(char *action)
> >>>  		return -1;
> >>>  	}
> >>>  
> >>> +	sprintf(image_dir, "/proc/%ld/fd/%d", (long) getpid(), get_service_fd(IMG_FD_OFF));
> >>
> >> Maybe /proc/self/fd/%d would be nicer? This would allow using the
> >> PSFDS above :)
> > 
> > I this, but it seems that the fds are declared O_CLOEXEC or something?
> > It doesn't look like open_image_dir does that, though, so I'm not sure
> > what is going on. They weren't available in the script, in any case.
> 
> Ah, no. It's me being stupid. The path you push into script will be used
> by this script, so open("/proc/self/fd/100") in script will open script's
> fd, not criu's one :)

Right, but presumably system() is implemented via fork(), which would
inherit the fds? I guess maybe not, since it doesn't work :)

Tycho