Add syscall wrapper for renameat2

Signed-off-by: Bryant G. Duffy-Ly <bduffyly@versity.com>

tests/.gitignore

@@ -1,5 +1,6 @@
 src/*.d
 src/createmany
+src/dumb_renameat2
 src/dumb_setxattr
 src/handle_cat
 src/bulk_create_paths

tests/Makefile

@@ -3,6 +3,7 @@ SHELL := /usr/bin/bash
 
 # each binary command is built from a single .c file
 BIN := src/createmany			\
+	src/dumb_renameat2		\
 	src/dumb_setxattr		\
 	src/handle_cat			\
 	src/bulk_create_paths		\

tests/src/dumb_renameat2.c

@@ -0,0 +1,93 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <fcntl.h>
+
+#ifndef RENAMEAT2_EXIST
+#include <unistd.h>
+#include <sys/syscall.h>
+
+#if !defined(SYS_renameat2) && defined(__x86_64__)
+#define SYS_renameat2 316			/* from arch/x86/entry/syscalls/syscall_64.tbl */
+#endif
+
+static int renameat2(int olddfd, const char *old_dir,
+		     int newdfd, const char *new_dir,
+		     unsigned int flags)
+{
+#ifdef SYS_renameat2
+	return syscall(SYS_renameat2, olddfd, old_dir, newdfd, new_dir, flags);
+#else
+	errno = ENOSYS;
+	return -1;
+#endif
+}
+#endif
+
+#ifndef RENAME_NOREPLACE
+#define RENAME_NOREPLACE	(1 << 0)	/* Don't overwrite newpath of rename */
+#endif
+#ifndef RENAME_EXCHANGE
+#define RENAME_EXCHANGE		(1 << 1)	/* Exchange oldpath and newpath */
+#endif
+#ifndef RENAME_WHITEOUT
+#define RENAME_WHITEOUT		(1 << 2)	/* Whiteout oldpath */
+#endif
+
+static void exit_usage(char **argv)
+{
+	fprintf(stderr,
+		"usage: %s [-n|-x|-w] old_path new_path\n"
+		"  -n  noreplace\n"
+		"  -x  exchange\n"
+		"  -w  whiteout\n", argv[0]);
+
+		exit(1);
+}
+
+int main(int argc, char **argv)
+{
+	const char *old_path = NULL;
+	const char *new_path = NULL;
+	unsigned int flags = 0;
+	int ret;
+	int c;
+
+	for (c = 1; c < argc; c++) {
+		if (argv[c][0] == '-') {
+			switch (argv[c][1]) {
+				case 'n':
+					flags |= RENAME_NOREPLACE;
+					break;
+				case 'x':
+					flags |= RENAME_EXCHANGE;
+					break;
+				case 'w':
+					flags |= RENAME_WHITEOUT;
+					break;
+				default:
+					exit_usage(argv);
+			}
+		} else if (!old_path) {
+			old_path = argv[c];
+		} else if (!new_path) {
+			new_path = argv[c];
+		} else {
+			exit_usage(argv);
+		}
+	}
+
+	if (!old_path || !new_path) {
+		printf("specify the correct directory path\n");
+		errno = ENOENT;
+		return 1;
+	}
+
+	ret = renameat2(AT_FDCWD, old_path, AT_FDCWD, new_path, flags);
+	if (ret == -1) {
+		perror("Error");
+		return 1;
+	}
+
+	return 0;
+}