restorer: Check error from exe link restore

Kenrel API is stable enough not to ignore it.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
files: Print more info about unsupported fd to dump

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
service: set CHECK type on check response

Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
vm: don't overwrite vma->shmid for private mappings

shmid contains a file id for file mappings. It's required to determine,
which VMA-s are cowed. The parent maps a VMA and saves premmaped
address. Then  child trys to determing, which VMA-s must be inhereted
from parent, for that it compares addresses, flags and file id.

We don't want to transfer vma_area-s in restorer, so when a VMA entry is
copied in restorer memory, the premmaped address is save in shmid.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
mm: fix expression to determine which vma-s can be shared

Currently only addresses are compared. It's obviously not enough.

* First of all the parent vma must be private.
* Both vma-s must have the identical set of MAP_GROWSDOWN and MAP_FILES
  flags.
* Both vma-s must be linked to the same file.

https://bugzilla.openvz.org/show_bug.cgi?id=2824
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>