[CRIU] [PATCH v3 3/8] stats: add a helper to get stats of parent pre-dump

[Pavel Tikhomirov]

From: ptikhomirov <ptikhomirov at virtuozzo.com>

will be used in the next patch

https://jira.sw.ru/browse/PSBM-67502

note: actually we need only one value from stats entry but I still
prefer general helper as we still need to read and allocate memory
for the whole structure

v2: fix get_parent_stats to have static typing
v3: simplify get_parent_stats to return a StatsEntry pointer instead of
doing it through arguments

Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
 criu/include/stats.h |  4 ++++
 criu/stats.c         | 31 +++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/criu/include/stats.h b/criu/include/stats.h
index 81775c856..14acdd59f 100644
--- a/criu/include/stats.h
+++ b/criu/include/stats.h
@@ -1,6 +1,8 @@
 #ifndef __CR_STATS_H__
 #define __CR_STATS_H__
 
+#include "images/stats.pb-c.h"
+
 enum {
 	TIME_FREEZING,
 	TIME_FROZEN,
@@ -23,6 +25,8 @@ extern void timing_start(int t);
 extern void timing_stop(int t);
 extern int timing_uptime(int t);
 
+extern StatsEntry *get_parent_stats(void);
+
 enum {
 	CNT_PAGES_SCANNED,
 	CNT_PAGES_SKIPPED_PARENT,
diff --git a/criu/stats.c b/criu/stats.c
index 2944474cd..4823e48de 100644
--- a/criu/stats.c
+++ b/criu/stats.c
@@ -213,6 +213,37 @@ void write_stats(int what)
 		display_stats(what, &stats);
 }
 
+__maybe_unused StatsEntry *get_parent_stats(void)
+{
+	struct cr_img *img;
+	StatsEntry *se;
+	int dir;
+
+	dir = openat(get_service_fd(IMG_FD_OFF), CR_PARENT_LINK, O_RDONLY);
+	if (dir == -1) {
+		pr_perror("Failed to open parent directory");
+		return NULL;
+	}
+
+	img = open_image_at(dir, CR_FD_STATS, O_RSTR, "dump");
+	if (!img) {
+		pr_perror("Failed to open parent dump stats");
+		close(dir);
+		return NULL;
+	}
+
+	if (pb_read_one(img, &se, PB_STATS) < 0) {
+		pr_perror("Failed to read parent dump stats");
+		close_image(img);
+		close(dir);
+		return NULL;
+	}
+
+	close_image(img);
+	close(dir);
+	return se;
+}
+
 int init_stats(int what)
 {
 	if (what == DUMP_STATS) {
-- 
2.14.3