retry blockdev mount

block devices are hotplugged to guest vm. It needs sometime for the
guest kernel to initialize. If we proceed too soon to mount, mount can
fail with ENOENT. Retry a bit in such case.

Signed-off-by: Peng Tao <bergwolf@gmail.com>

Author: bergwolf

src/container.c

@@ -134,7 +134,7 @@ static int container_setup_volume(struct hyper_container *container)
 			if (!strcmp(vol->fstype, "xfs"))
 				options = "nouuid";
 
-			if (mount(dev, path, vol->fstype, 0, options) < 0) {
+			if (hyper_mount_blockdev(dev, path, vol->fstype, options) < 0) {
 				perror("mount volume device failed");
 				return -1;
 			}
@@ -588,7 +588,7 @@ static int hyper_setup_container_rootfs(void *data)
 		if (!strncmp(container->fstype, "xfs", strlen("xfs")))
 			options = "nouuid";
 
-		if (mount(dev, root, container->fstype, 0, options) < 0) {
+		if (hyper_mount_blockdev(dev, root, container->fstype, options) < 0) {
 			perror("mount device failed");
 			goto fail;
 		}

src/util.c

@@ -913,3 +913,21 @@ int hyper_eventfd_send(int fd, int64_t type)
 
 	return 0;
 }
+
+/* block device might not be present when we call mount. Sleep a bit in such case */
+int hyper_mount_blockdev(const char *dev, const char *root, const char *fstype, const char *options)
+{
+	int i, retry = 5;
+
+	for (i = 0; i < retry; i++) {
+		if (mount(dev, root, fstype, 0, options) < 0) {
+			if (errno != ENOENT)
+				return -1;
+			usleep(20000);
+			continue;
+		}
+		return 0;
+	}
+
+	return -1;
+}

src/util.h

@@ -50,4 +50,5 @@ ssize_t nonblock_read(int fd, void *buf, size_t count);
 int hyper_mount_nfs(char *server, char *mountpoint);
 int64_t hyper_eventfd_recv(int fd);
 int hyper_eventfd_send(int fd, int64_t type);
+int hyper_mount_blockdev(const char *dev, const char *root, const char *fstype, const char *options);
 #endif