From: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx> Subject: kselftest/vm: revert "tools/testing/selftests/vm/userfaultfd.c: use swap() to make code cleaner" 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. Link: https://lkml.kernel.org/r/20220202003340.87195-1-skhan@xxxxxxxxxxxxxxxxxxx Fixes: 2c769ed7137a ("tools/testing/selftests/vm/userfaultfd.c: use swap() to make code cleaner") Signed-off-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx> Cc: Shuah Khan <shuah@xxxxxxxxxx> Cc: Minghao Chi <chi.minghao@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- tools/testing/selftests/vm/userfaultfd.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) --- a/tools/testing/selftests/vm/userfaultfd.c~kselftest-vm-revert-tools-testing-selftests-vm-userfaultfdc-use-swap-to-make-code-cleaner +++ a/tools/testing/selftests/vm/userfaultfd.c @@ -1417,6 +1417,7 @@ static void userfaultfd_pagemap_test(uns 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); - - swap(area_src_alias, area_dst_alias); + tmp_area = area_src; + area_src = area_dst; + area_dst = tmp_area; + + tmp_area = area_src_alias; + area_src_alias = area_dst_alias; + area_dst_alias = tmp_area; uffd_stats_report(uffd_stats, nr_cpus); } _