[CRIU] irmap: Can't stat /no-such-path: No such file or directory

[Pavel Emelyanov]

On 09/05/2015 06:17 AM, Tycho Andersen wrote:
> Hi all,
> 
> With newer versions of ubuntu (host and guest), I'm seeing the error
> listed in the subject. The full log is:

This path was put there deliberately to make sure irmap resolver
doesn't break on non-existing paths :)

> http://paste.ubuntu.com/12279228/
> 
> It seems to me like we shouldn't be trying to stat no-such-path, but
> that seems like the symptom of a larger problem which is that we can't
> otherwise resolve the handle.
> 
> I resolved the inode using debugfs, and it says it's /var/log in the
> container, which is not one of our heuristic paths we check:
> 
> # debugfs -R 'ncheck 525799' /dev/vda1
> debugfs 1.42.12 (29-Aug-2014)
> Inode Pathname
> 525799  /var/lib/lxd/containers/unpriv/rootfs/var/log
> 
> If I add this path (and several others, see the attached patch) to the
> list of irmap hints, it works fine. Obviously this isn't sustainable
> though; is there some nicer solution to this?

Well, right now we don't have any :( The problem here is that *notify
objects are assigned on inode and kernel can drop all the path information
from it. So once we meet an *notified inode we _try_ to ask kernel for
path and, if it fails, have no other ways to resolve it back.

> Thanks,
> 
> Tycho
> 
> 
> 
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