image: Introduce files.img and file_entry

There are two goals of this merge. First is to reduce the amount
of image files we generate and scan on restore. The latter is
more importaint, as even if we have no weird stuff like signalfd,
we still try to open this file. So after the merge we try to
open ~15 image files (out of ~30) less %) which is nice.

The 2nd goal is to simplify the C/R support for SCM messages.
This becomes possible with the fact, that all files we have can
be distinguished by their ID only, w/o type. This, in turn,
makes image layout for SCMs much simpler.

Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

criu/cr-restore.c

@@ -278,6 +278,9 @@ static struct collect_image_info *cinfos[] = {
 	&sk_queues_cinfo,
 };
 
+static struct collect_image_info *cinfos_files[] = {
+};
+
 /* These images are requered to restore namespaces */
 static struct collect_image_info *before_ns_cinfos[] = {
 	&tty_info_cinfo, /* Restore devpts content */
@@ -320,6 +323,10 @@ static int root_prepare_shared(void)
 	if (collect_images(cinfos, ARRAY_SIZE(cinfos)))
 		return -1;
 
+	if (!files_collected() &&
+			collect_images(cinfos_files, ARRAY_SIZE(cinfos_files)))
+		return -1;
+
 	for_each_pstree_item(pi) {
 		if (pi->pid->state == TASK_HELPER)
 			continue;

criu/files.c

@@ -1664,8 +1664,30 @@ int open_transport_socket(void)
 	return 0;
 }
 
+static int collect_one_file(void *o, ProtobufCMessage *base, struct cr_img *i)
+{
+	int ret = 0;
+	FileEntry *fe;
+
+	fe = pb_msg(base, FileEntry);
+	switch (fe->type) {
+	default:
+		pr_err("Unknown file type %d\n", fe->type);
+		return -1;
+	}
+
+	return ret;
+}
+
+struct collect_image_info files_cinfo = {
+	.fd_type = CR_FD_FILES,
+	.pb_type = PB_FILE,
+	.priv_size = 0,
+	.collect = collect_one_file,
+};
+
 int prepare_files(void)
 {
 	init_fdesc_hash();
-	return 0;
+	return collect_image(&files_cinfo);
 }

criu/image-desc.c

@@ -99,6 +99,7 @@ struct cr_fd_desc_tmpl imgset_template[CR_FD_MAX] = {
 	FD_ENTRY(USERNS,	"userns-%d"),
 	FD_ENTRY(NETNF_CT,	"netns-ct-%d"),
 	FD_ENTRY(NETNF_EXP,	"netns-exp-%d"),
+	FD_ENTRY(FILES,		"files"),
 
 	[CR_FD_STATS] = {
 		.fmt	= "stats-%s",

criu/include/files.h

@@ -162,6 +162,9 @@ extern int restore_fs(struct pstree_item *);
 extern int prepare_fs_pid(struct pstree_item *);
 extern int set_fd_flags(int fd, int flags);
 
+extern struct collect_image_info files_cinfo;
+#define files_collected() (files_cinfo.flags & COLLECT_HAPPENED)
+
 extern int close_old_fds(void);
 #ifndef AT_EMPTY_PATH
 #define AT_EMPTY_PATH 0x1000

criu/include/image-desc.h

@@ -54,6 +54,7 @@ enum {
 	CR_FD_FDINFO,
 
 	_CR_FD_GLOB_FROM,
+	CR_FD_FILES,
 	CR_FD_SK_QUEUES,
 	CR_FD_REG_FILES,
 	CR_FD_EXT_FILES,

criu/include/magic.h

@@ -93,6 +93,7 @@
 #define SECCOMP_MAGIC		0x64413049 /* Kostomuksha */
 #define BINFMT_MISC_MAGIC	0x67343323 /* Apatity */
 #define AUTOFS_MAGIC		0x49353943 /* Sochi */
+#define FILES_MAGIC		0x56303138 /* Toropets */
 
 #define IFADDR_MAGIC		RAW_IMAGE_MAGIC
 #define ROUTE_MAGIC		RAW_IMAGE_MAGIC

criu/include/protobuf-desc.h

@@ -60,6 +60,7 @@ enum {
 	PB_TTY_DATA,
 	PB_AUTOFS,
 	PB_GHOST_CHUNK,
+	PB_FILE,
 
 	/* PB_AUTOGEN_STOP */
 

images/fdinfo.proto

@@ -27,3 +27,8 @@ message fdinfo_entry {
 	required fd_types	type	= 3;
 	required uint32		fd	= 4;
 }
+
+message file_entry {
+	required fd_types		type	= 1;
+	required uint32			id	= 2;
+}

lib/py/images/images.py

@@ -506,6 +506,7 @@ handlers = {
 	'USERNS'		: entry_handler(userns_entry),
 	'SECCOMP'		: entry_handler(seccomp_entry),
 	'AUTOFS'		: entry_handler(autofs_entry),
+	'FILES'                 : entry_handler(file_entry),
 	}
 
 def __rhandler(f):