[CRIU] [RFC PATCH 12/12] lazy-pages: request userfaultfd events during API handshake

[Pavel Emelyanov]

On 01/09/2017 11:23 AM, Mike Rapoport wrote:
> Signed-off-by: Mike Rapoport <rppt at linux.vnet.ibm.com>
> ---
>  criu/uffd.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/criu/uffd.c b/criu/uffd.c
> index 934c182..6e7179f 100644
> --- a/criu/uffd.c
> +++ b/criu/uffd.c
> @@ -45,6 +45,10 @@
>  
>  #define LAZY_PAGES_SOCK_NAME	"lazy-pages.socket"
>  
> +#define NEED_UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK |	    \
> +				UFFD_FEATURE_EVENT_REMAP |	    \
> +				UFFD_FEATURE_EVENT_MADVDONTNEED)
> +
>  static mutex_t *lazy_sock_mutex;
>  
>  struct lazy_iovec {
> @@ -222,7 +226,7 @@ int setup_uffd(int pid, struct task_restore_args *task_args)
>  	 * Check if the UFFD_API is the one which is expected
>  	 */
>  	uffdio_api.api = UFFD_API;
> -	uffdio_api.features = 0;
> +	uffdio_api.features = kdat.uffd_features & NEED_UFFD_API_FEATURES;
>  	if (ioctl(task_args->uffd, UFFDIO_API, &uffdio_api)) {

I don't remember exactly how this works ... shouldn't we read the supported
features back and check for all of them being there?

>  		pr_err("Checking for UFFDIO_API failed.\n");
>  		goto err;
>