fdstore: Unlimit fdstore queue on start

We use fdstore intensively for example when handling
bindmounted sockets and ghost dgram sockets. The system
limit for per-socket queue may not be enough if someone
generate lots of ghost sockets (150 and more as been
detected on default fedora 27).

To make it operatable lets unlimit fdstore queue size
on startup.
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/fdstore.c

@@ -20,6 +20,8 @@ static struct fdstore_desc {
 
 int fdstore_init(void)
 {
+	/* In kernel a bufsize has type int and a value is doubled. */
+	uint32_t buf[2] = { INT_MAX / 2, INT_MAX / 2 };
 	struct sockaddr_un addr;
 	unsigned int addrlen;
 	struct stat st;
@@ -44,6 +46,13 @@ int fdstore_init(void)
 		return -1;
 	}
 
+	if (setsockopt(sk, SOL_SOCKET, SO_SNDBUFFORCE, &buf[0], sizeof(buf[0])) < 0 ||
+	    setsockopt(sk, SOL_SOCKET, SO_RCVBUFFORCE, &buf[1], sizeof(buf[1])) < 0) {
+		pr_perror("Unable to set SO_SNDBUFFORCE/SO_RCVBUFFORCE");
+		close(sk);
+		return -1;
+	}
+
 	addr.sun_family = AF_UNIX;
 	addrlen = snprintf(addr.sun_path, sizeof(addr.sun_path), "X/criu-fdstore-%"PRIx64, st.st_ino);
 	addrlen += sizeof(addr.sun_family);
@@ -79,11 +88,13 @@ int fdstore_init(void)
 int fdstore_add(int fd)
 {
 	int sk = get_service_fd(FDSTORE_SK_OFF);
-	int id;
+	int id, ret;
 
 	mutex_lock(&desc->lock);
 
-	if (send_fd(sk, NULL, 0, fd)) {
+	ret = send_fd(sk, NULL, 0, fd);
+	if (ret) {
+		pr_perror("Can't send fd %d into store\n", fd);
 		mutex_unlock(&desc->lock);
 		return -1;
 	}