[CRIU] [PATCH] cr-service: add lazy-pages RPC feature check

[Adrian Reber]

From: Adrian Reber <areber at redhat.com>

Extend the RPC feature check functionality to also test for lazy-pages
support. This does not check for certain UFFD features (yet). Right now
it only checks if kerndat_uffd() returns a least one UFFD feature.

Signed-off-by: Adrian Reber <areber at redhat.com>
---
 criu/cr-service.c | 39 ++++++++++++++++++++++++++-------------
 images/rpc.proto  |  1 +
 2 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/criu/cr-service.c b/criu/cr-service.c
index ff5a7a8..3e15e5f 100644
--- a/criu/cr-service.c
+++ b/criu/cr-service.c
@@ -829,15 +829,12 @@ static int handle_feature_check(int sk, CriuReq * msg)
 	/* enable setting of an optional message */
 	feat.has_mem_track = 1;
 	feat.mem_track = false;
+	feat.has_lazy_pages = 1;
+	feat.lazy_pages = false;
 
-	/*
-	 * Check if the requested feature check can be answered.
-	 *
-	 * This function is right now hard-coded to memory
-	 * tracking detection and needs other/better logic to
-	 * handle multiple feature checks.
-	 */
-	if (msg->features->has_mem_track != 1) {
+	/* Check if the requested feature check can be answered. */
+	if ((msg->features->has_mem_track != 1) ||
+	    (msg->features->has_lazy_pages != 1)) {
 		pr_warn("Feature checking for unknown feature.\n");
 		goto out;
 	}
@@ -850,6 +847,9 @@ static int handle_feature_check(int sk, CriuReq * msg)
 	 */
 	success = true;
 
+#define HAS_MEM_TRACK (1<<0)
+#define HAS_LAZY_PAGES (1<<1)
+
 	pid = fork();
 	if (pid < 0) {
 		pr_perror("Can't fork");
@@ -857,23 +857,36 @@ static int handle_feature_check(int sk, CriuReq * msg)
 	}
 
 	if (pid == 0) {
-		int ret = 1;
+		int rc = -1;
+		int ret = 0;
 
 		setproctitle("feature-check --rpc");
 
-		kerndat_get_dirty_track();
+		if ((msg->features->has_mem_track == 1) &&
+		    (msg->features->mem_track == true))
+			kerndat_get_dirty_track();
 
 		if (kdat.has_dirty_track)
-			ret = 0;
+			ret |= HAS_MEM_TRACK;
+
+		if ((msg->features->has_lazy_pages == 1) &&
+		    (msg->features->lazy_pages == true))
+			rc = kerndat_uffd(true);
+
+		if ((rc != -1) && kdat.uffd_features)
+			ret |= HAS_LAZY_PAGES;
 
 		exit(ret);
 	}
 
 	wait(&status);
-	if (!WIFEXITED(status) || WEXITSTATUS(status))
+	if (!WIFEXITED(status))
 		goto out;
 
-	feat.mem_track = true;
+	if (WEXITSTATUS(status) == (HAS_MEM_TRACK & 0xff))
+		feat.mem_track = true;
+	if (WEXITSTATUS(status) == (HAS_LAZY_PAGES & 0xff))
+		feat.lazy_pages = true;
 out:
 	resp.features = &feat;
 	resp.type = msg->type;
diff --git a/images/rpc.proto b/images/rpc.proto
index f924b73..f894ae1 100644
--- a/images/rpc.proto
+++ b/images/rpc.proto
@@ -148,6 +148,7 @@ enum criu_req_type {
  */
 message criu_features {
 	optional bool			mem_track	= 1;
+	optional bool			lazy_pages	= 2;
 }
 
 /*
-- 
2.9.3