[CRIU] [PATCH 1/2] kdat: Add check for inotify() INOTIFY_IOC_SETNEXTWD cmd

[Kirill Tkhai]

This is a new ioctl, which allows to request next descriptor
allocated by inotify_add_watch().

https://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs.git/commit/?h=for_next&id=e1603b6effe177210701d3d7132d1b68e7bd2c93

The patch checks this cmd is supported by kernel.

Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 criu/include/fsnotify.h |    4 ++++
 criu/include/kerndat.h  |    1 +
 criu/kerndat.c          |   28 ++++++++++++++++++++++++++++
 3 files changed, 33 insertions(+)

diff --git a/criu/include/fsnotify.h b/criu/include/fsnotify.h
index 7bf5af455..935dd60f4 100644
--- a/criu/include/fsnotify.h
+++ b/criu/include/fsnotify.h
@@ -8,6 +8,10 @@
 
 #define KERNEL_FS_EVENT_ON_CHILD 0x08000000
 
+#ifndef INOTIFY_IOC_SETNEXTWD
+#define INOTIFY_IOC_SETNEXTWD  _IOW('I', 0, __s32)
+#endif
+
 extern int is_inotify_link(char *link);
 extern int is_fanotify_link(char *link);
 extern const struct fdtype_ops inotify_dump_ops;
diff --git a/criu/include/kerndat.h b/criu/include/kerndat.h
index 9e7af14a3..db03eb86f 100644
--- a/criu/include/kerndat.h
+++ b/criu/include/kerndat.h
@@ -73,6 +73,7 @@ struct kerndat_s {
 	unsigned long files_stat_max_files;
 	bool has_pid_for_children_ns;
 	bool x86_has_ptrace_fpu_xsave_bug;
+	bool has_inotify_setnextwd;
 };
 
 extern struct kerndat_s kdat;
diff --git a/criu/kerndat.c b/criu/kerndat.c
index cea2e3348..d0d06e3a0 100644
--- a/criu/kerndat.c
+++ b/criu/kerndat.c
@@ -12,6 +12,8 @@
 #include <sys/socket.h>
 #include <arpa/inet.h>  /* for sockaddr_in and inet_ntoa() */
 #include <sys/prctl.h>
+#include <sys/inotify.h>
+
 
 #include "common/config.h"
 #include "int.h"
@@ -32,6 +34,7 @@
 #include <compel/plugins/std/syscall-codes.h>
 #include <compel/compel.h>
 #include "netfilter.h"
+#include "fsnotify.h"
 #include "linux/userfaultfd.h"
 #include "prctl.h"
 #include "uffd.h"
@@ -792,6 +795,29 @@ int kerndat_has_pid_for_children_ns(void)
 	return 0;
 }
 
+int kerndat_has_inotify_setnextwd(void)
+{
+	int ret = 0;
+	int fd;
+
+	fd = inotify_init();
+	if (fd < 0) {
+		pr_perror("Can't create inotify");
+		return -1;
+	}
+
+	if (ioctl(fd, INOTIFY_IOC_SETNEXTWD, 0x10)) {
+		if (errno != ENOTTY) {
+			pr_perror("Can't call ioctl");
+			ret = -1;
+		}
+	} else
+		kdat.has_inotify_setnextwd = true;
+
+	close(fd);
+	return ret;
+}
+
 int __attribute__((weak)) kdat_x86_has_ptrace_fpu_xsave_bug(void)
 {
 	return 0;
@@ -1077,6 +1103,8 @@ int kerndat_init(void)
 		ret = kerndat_has_pid_for_children_ns();
 	if (!ret)
 		ret = kerndat_x86_has_ptrace_fpu_xsave_bug();
+	if (!ret)
+		ret = kerndat_has_inotify_setnextwd();
 
 	kerndat_lsm();
 	kerndat_mmap_min_addr();