[CRIU] [PATCH 0/1] report fd/path if dump_one_reg_file()->lookup_nsid_by_mnt_id() fails

[Tycho Andersen]

On Tue, Apr 21, 2015 at 10:05:45PM +0300, Pavel Emelyanov wrote:
> On 04/21/2015 08:14 PM, Oleg Nesterov wrote:
> > On 04/21, Pavel Emelyanov wrote:
> >>
> >> This is just to make sure I properly track what's going on with mount.c :)
> > 
> > A bit off-topic, but let me remind about another problem before I forgot...
> > 
> > 	# unshare -m
> > 	# perl -e 'sleep'
> > 
> > Now "criu dump -t `pidof perl`" fails with
> > 
> > 	Error (files-reg.c:821): Unable to look up the 22 mount
> > 	Error (cr-dump.c:1580): Dump files (pid: 10822) failed with -1
> > 
> > So there are 2 problems:
> > 
> > 	1. The error message is confusing and doesn't help to understand
> > 	   whats going on.
> > 
> > 	   "Fixed" by this patch.
> 
> Thank you :)
> 
> > 	2. Well, it would be nice to handle this case too.
> 
> But what's the case? Why the 22nd mount isn't looked-up?

It's something like the process still has an fd open on a mount
namespace which it doesn't see any more (because of unshare()).
Usually happens with stdin/stdout/stderr, because they are opened when
the program starts, and then unshare() is called but they still point
to the parent ns.

Tycho

> > 	   Left as an exercise for criu developers.
> 
> -- Pavel
>