[CRIU] [PATCH 0/4] sk-unix: Handle bindmounted dgram sockets

[Cyrill Gorcunov]

On Tue, Aug 08, 2017 at 03:12:20PM +0300, Pavel Emelyanov wrote:
> On 08/08/2017 02:25 PM, Cyrill Gorcunov wrote:
> > We've discovered a situation where socket is bindmounted inside
> > container (mysql daemon uses /dev/log bindmounted) so restore
> > procedure may fail because sockets are opened later than mount
> > engine is trying to bindmount.
> 
> The socket is bint-mount-ed, and the mountpoint is restored before the attempt
> to open (bind/connect to?) the socket, so why does the latter fail?

Because socket doesn't exist yet at the moment we're calling mount().
Thus we've to create socket first.

> 
> > For this sake we detect such situstion on dump and use fdstore
> > engine to open a socket needed before mount call.
> 
> Is this a special case of a more generic problem called "overmounted files"?

Not really. The files have to present on the FS so mount on regular
files wont fail.