selftests/filesystems: create get_unique_mnt_id() helper

Add helper to utils.c and use it in mount-notify and statmount tests.

Linking with utils.c drags in a dependecy with libcap, so add it to the
Makefile of the tests.

Reviewed-by: John Hubbard <[email protected]>
Signed-off-by: Amir Goldstein <[email protected]>
Link: https://lore.kernel.org/[email protected]
Reviewed-by: Christian Brauner <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>

1 files changed, 22 insertions, 0 deletions

diff --git a/tools/testing/selftests/filesystems/utils.c b/tools/testing/selftests/filesystems/utils.c
index e553c89c5b19..5a114af822af 100644
--- a/tools/testing/selftests/filesystems/utils.c
+++ b/tools/testing/selftests/filesystems/utils.c
@@ -19,6 +19,8 @@
 #include <sys/wait.h>
 #include <sys/xattr.h>
 
+#include "../kselftest.h"
+#include "wrappers.h"
 #include "utils.h"
 
 #define MAX_USERNS_LEVEL 32
@@ -499,3 +501,23 @@ out:
 	cap_free(caps);
 	return fret;
 }
+
+uint64_t get_unique_mnt_id(const char *path)
+{
+	struct statx sx;
+	int ret;
+
+	ret = statx(AT_FDCWD, path, 0, STATX_MNT_ID_UNIQUE, &sx);
+	if (ret == -1) {
+		ksft_print_msg("retrieving unique mount ID for %s: %s\n", path,
+			 strerror(errno));
+		return 0;
+	}
+
+	if (!(sx.stx_mask & STATX_MNT_ID_UNIQUE)) {
+		ksft_print_msg("no unique mount ID available for %s\n", path);
+		return 0;
+	}
+
+	return sx.stx_mnt_id;
+}