[CRIU] [PATCH] util: use F_DUPFD when we don't want to overwrite an existing descriptor

[Cyrill Gorcunov]

On Tue, May 21, 2019 at 12:13:27AM -0700, Andrei Vagin wrote:
> Right now we use fcntl(F_GETFD) to check whether a target descriptor
> is used and then we call dup2(). Actually, we can do this for one system
> call.
> 
> Cc: Cyrill Gorcunov <gorcunov at openvz.org>
> Signed-off-by: Andrei Vagin <avagin at gmail.com>
Reviewed-by: Cyrill Gorcunov <gorcunov at gmail.com>