rst: Read sys.last_cap only once in kerndat

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-restore.c

@@ -59,7 +59,6 @@
 #include "cpu.h"
 #include "file-lock.h"
 #include "page-read.h"
-#include "sysctl.h"
 #include "vdso.h"
 #include "stats.h"
 #include "tun.h"
@@ -1934,17 +1933,6 @@ static int prepare_creds(int pid, struct task_restore_core_args *args)
 	int fd, ret;
 	CredsEntry *ce;
 
-	struct sysctl_req req[] = {
-		{ "kernel/cap_last_cap", &args->cap_last_cap, CTL_U32 },
-		{ },
-	};
-
-	ret = sysctl_op(req, CTL_READ);
-	if (ret < 0) {
-		pr_err("Failed to read max IPC message size\n");
-		return -1;
-	}
-
 	fd = open_image(CR_FD_CREDS, O_RSTR, pid);
 	if (fd < 0)
 		return fd;
@@ -1988,6 +1976,8 @@ static int prepare_creds(int pid, struct task_restore_core_args *args)
 
 	creds_entry__free_unpacked(ce, NULL);
 
+	args->cap_last_cap = kern_last_cap;
+
 	/* XXX -- validate creds here? */
 
 	return 0;

include/kerndat.h

@@ -17,4 +17,6 @@ extern bool kerndat_has_dirty_track;
 
 extern int tcp_max_wshare;
 extern int tcp_max_rshare;
+
+extern int kern_last_cap;
 #endif

kerndat.c

@@ -156,13 +156,31 @@ int kerndat_init(void)
 	return ret;
 }
 
+int kern_last_cap;
+
+int get_last_cap(void)
+{
+	struct sysctl_req req[] = {
+		{ "kernel/cap_last_cap", &kern_last_cap, CTL_U32 },
+		{ },
+	};
+
+	return sysctl_op(req, CTL_READ);
+}
+
 int kerndat_init_rst(void)
 {
+	int ret;
+
 	/*
 	 * Read TCP sysctls before anything else,
 	 * since the limits we're interested in are
 	 * not available inside namespaces.
 	 */
 
-	return tcp_read_sysctl_limits();
+	ret = tcp_read_sysctl_limits();
+	if (!ret)
+		ret = get_last_cap();
+
+	return ret;
 }