criu/0035-sysvshm-add-dump-restore-sysv-shm-in-host-ipc-ns.patch

From 852b4db35a06ed382e287d88cd055fdf20fc031f Mon Sep 17 00:00:00 2001
From: "fu.lin" <fu.lin10@huawei.com>
Date: Sat, 26 Jun 2021 15:18:15 +0800
Subject: [PATCH 35/72] sysvshm: add dump/restore sysv-shm in host ipc ns

In original criu design, SysVIPC memory segment, which belongs
to host ipcns, shouldn't be dumped because criu requires the
whole ipcns to be dumped. During the restoring ipcns, the new
shared memory will be created, and fill the original page data
in it.

This patch makes the shared-memory in host ipcns restore possible.
Idea:
  The SysVIPC memory won't disappear after the task exit. The basic
information can be got from `/proc/sysvipc/shm` as long as the
system doesn't reboot. Compared with restoring the whole ipcns,
the processes of the shared memory creating and page data filling
are ignored.

Reference:
- https://www.criu.org/What_cannot_be_checkpointed

Conflict:NA
Reference:https://gitee.com/src-openeuler/criu/pulls/21
Signed-off-by: fu.lin <fu.lin10@huawei.com>
---
 criu/cr-dump.c    |  8 ++++----
 criu/cr-restore.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 4 deletions(-)

diff --git a/criu/cr-dump.c b/criu/cr-dump.c
index b7e0214..e7b5787 100644
--- a/criu/cr-dump.c
+++ b/criu/cr-dump.c
@@ -463,11 +463,11 @@ static int dump_filemap(struct vma_area *vma_area, int fd)
 
 static int check_sysvipc_map_dump(pid_t pid, VmaEntry *vma)
 {
-	if (root_ns_mask & CLONE_NEWIPC)
-		return 0;
+	if (!(root_ns_mask & CLONE_NEWIPC))
+		pr_info("Task %d with SysVIPC shmem map @%" PRIx64 " doesn't live in IPC ns\n",
+			pid, vma->start);
 
-	pr_err("Task %d with SysVIPC shmem map @%" PRIx64 " doesn't live in IPC ns\n", pid, vma->start);
-	return -1;
+	return 0;
 }
 
 static int get_task_auxv(pid_t pid, MmEntry *mm)
diff --git a/criu/cr-restore.c b/criu/cr-restore.c
index 09f135b..152bace 100644
--- a/criu/cr-restore.c
+++ b/criu/cr-restore.c
@@ -1818,6 +1818,46 @@ static int create_children_and_session(void)
 	return 0;
 }
 
+static int prepare_rootns_sysv_shm(unsigned long clone_flags)
+{
+	int retval = 0;
+	char *line = NULL;
+	size_t len = 0;
+	FILE *fp;
+	key_t key;
+	int shmid;
+	mode_t	mode;
+	size_t size;
+
+	/* This is completed by `prepare_namespace()` */
+	if (!!(clone_flags & CLONE_NEWIPC))
+		return 0;
+
+	pr_info("Restoring SYSV shm in host namespace\n");
+
+	fp = fopen("/proc/sysvipc/shm", "r");
+	if (fp == NULL) {
+		pr_err("Can't open '/proc/sysvipc/shm', errno(%d): %s\n", errno, strerror(errno));
+		return -1;
+	}
+
+	while (getline(&line, &len, fp) != -1) {
+		if (sscanf(line, "%d %d %o %lu", &key, &shmid, &mode, &size) != 4)
+			continue;
+
+		pr_debug("sscanf key: %d shmid: %d mode %o size %lu\n",
+				key, shmid, mode, size);
+
+		retval = collect_sysv_shmem(shmid, size);
+		if (retval != 0)
+			goto out;
+	}
+
+out:
+	fclose(fp);
+	return retval;
+}
+
 static int restore_task_with_children(void *_arg)
 {
 	struct cr_clone_arg *ca = _arg;
@@ -1924,6 +1964,9 @@ static int restore_task_with_children(void *_arg)
 		if (prepare_namespace(current, ca->clone_flags))
 			goto err;
 
+		if (prepare_rootns_sysv_shm(ca->clone_flags))
+			goto err;
+
 		if (restore_finish_ns_stage(CR_STATE_PREPARE_NAMESPACES, CR_STATE_FORKING) < 0)
 			goto err;
 
-- 
2.34.1