From 81fced01665d93a452486fa7f747ae1c9d1295d53211a1dcf6ca9e0fb891bb4e Mon Sep 17 00:00:00 2001
From: Ludwig Nussel <lnussel@suse.com>
Date: Wed, 2 Jun 2021 13:04:49 +0000
Subject: [PATCH] Accepting request 896791 from home:haasn:branches:Base:System

- add fallback for filesystems without renameat2

This change makes it succeed successfully on my system, which has a ZFS rootfs
(so no renameat2).

OBS-URL: https://build.opensuse.org/request/show/896791
OBS-URL: https://build.opensuse.org/package/show/Base:System/compat-usrmerge?expand=0&rev=11
---
 compat-usrmerge.changes |  5 +++++
 xmv.c                   | 30 +++++++++++++++++++++++++++---
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/compat-usrmerge.changes b/compat-usrmerge.changes
index 6a2d438..eb5757f 100644
--- a/compat-usrmerge.changes
+++ b/compat-usrmerge.changes
@@ -1,3 +1,8 @@
+-------------------------------------------------------------------
+Tue Jun  1 23:27:08 UTC 2021 - Niklas Haas <obs@haasn.xyz>
+
+- add fallback for filesystems without renameat2
+
 -------------------------------------------------------------------
 Thu Mar 25 09:50:48 UTC 2021 - Ludwig Nussel <lnussel@suse.de>
 
diff --git a/xmv.c b/xmv.c
index f7c31a4..d29bae5 100644
--- a/xmv.c
+++ b/xmv.c
@@ -66,10 +66,34 @@ int main(int argc, char** argv)
 	if (argc-optind < 2)
 		help(argv[0], 1);
 
-	r = syscall (SYS_renameat2, AT_FDCWD, argv[optind], AT_FDCWD, argv[optind+1], RENAME_EXCHANGE);
+	const char *source = argv[optind], *target = argv[optind+1];
+	r = syscall (SYS_renameat2, AT_FDCWD, source, AT_FDCWD, target, RENAME_EXCHANGE);
 	if (r < 0) {
-		perror("renameat2");
-		return 1;
+		if (errno != EINVAL) {
+			perror("renameat2");
+			return 1;
+		}
+
+		/* Fallback for systems without renameat2 support */
+		char *tmp;
+		r = asprintf(&tmp, "%s.XXXXXX", target);
+		if (r < 0) {
+			perror("asprintf");
+			return 1;
+		}
+		mktemp(tmp);
+
+		r = renameat(AT_FDCWD, target, AT_FDCWD, tmp);
+		if (!r)
+			r = renameat(AT_FDCWD, source, AT_FDCWD, target);
+		if (!r)
+			r = renameat(AT_FDCWD, tmp, AT_FDCWD, source);
+		free(tmp);
+
+		if (r < 0) {
+			perror("renameat");
+			return 1;
+		}
 	}
 
 	return 0;