image: open_image_at -- Add O_OPT flag

This allows us to distinguish the situation where image
to be opened is missing but optional, thus no error message
should be printed.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

image.c

@@ -184,16 +184,21 @@ struct cr_fdset *cr_glob_fdset_open(int mode)
 
 int open_image_at(int dfd, int type, unsigned long flags, ...)
 {
+	bool optional = !!(flags & O_OPT);
 	char path[PATH_MAX];
 	va_list args;
 	int ret;
 
+	flags &= ~O_OPT;
+
 	va_start(args, flags);
 	vsnprintf(path, PATH_MAX, fdset_template[type].fmt, args);
 	va_end(args);
 
 	ret = openat(dfd, path, flags, CR_FD_PERM);
 	if (ret < 0) {
+		if (optional && errno == ENOENT)
+			return -ENOENT;
 		pr_perror("Unable to open %s", path);
 		goto err;
 	}

include/image.h

@@ -68,6 +68,7 @@ extern bool ns_per_id;
 #define O_DUMP	(O_RDWR | O_CREAT | O_TRUNC)
 #define O_SHOW	(O_RDONLY)
 #define O_RSTR	(O_RDONLY)
+#define O_OPT	(O_PATH)
 
 extern int open_image_dir(char *dir);
 extern void close_image_dir(void);