[PATCH] kselftest/vm: Revert "tools/testing/selftests/vm/userfaultfd.c: use swap() to make code cleaner"

[Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>]

With this change, userfaultfd fails to build with undefined reference
swap() error:

userfaultfd.c: In function ‘userfaultfd_stress’:
userfaultfd.c:1530:17: warning: implicit declaration of function ‘swap’; did you mean ‘swab’? [-Wimplicit-function-declaration]
 1530 |                 swap(area_src, area_dst);
      |                 ^~~~
      |                 swab
/usr/bin/ld: /tmp/ccDGOAdV.o: in function `userfaultfd_stress':
userfaultfd.c:(.text+0x549e): undefined reference to `swap'
/usr/bin/ld: userfaultfd.c:(.text+0x54bc): undefined reference to `swap'
collect2: error: ld returned 1 exit status

Revert the commit to fix the problem.

Fixes: 2c769ed7137a ("tools/testing/selftests/vm/userfaultfd.c: use swap() to make code cleaner")
Signed-off-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
---
 tools/testing/selftests/vm/userfaultfd.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index d3fd24f9fae8..2f49c9af1b58 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -1417,6 +1417,7 @@ static void userfaultfd_pagemap_test(unsigned int test_pgsize)
 static int userfaultfd_stress(void)
 {
 	void *area;
+	char *tmp_area;
 	unsigned long nr;
 	struct uffdio_register uffdio_register;
 	struct uffd_stats uffd_stats[nr_cpus];
@@ -1527,9 +1528,13 @@ static int userfaultfd_stress(void)
 					    count_verify[nr], nr);
 
 		/* prepare next bounce */
-		swap(area_src, area_dst);
+		tmp_area = area_src;
+		area_src = area_dst;
+		area_dst = tmp_area;
 
-		swap(area_src_alias, area_dst_alias);
+		tmp_area = area_src_alias;
+		area_src_alias = area_dst_alias;
+		area_dst_alias = tmp_area;
 
 		uffd_stats_report(uffd_stats, nr_cpus);
 	}
-- 
2.32.0