In a few cases, such as after open() or access() gave an error,
using pr_perror() is preferable as it gives us errno.

In some cases, use pr_err() instead of pr_msg() -- for consistency.

In cases after sys_* calls, errno is not set but is returned
and so to use pr_perror() we should assign errno manually.
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>