From 30cd89e371581dea9eb81c74b65f39b671674620 Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Thu, 18 Mar 2021 17:01:53 +1100 Subject: [PATCH] BACKPORT: FROMGIT: userfaultfd/selftests: drop VERIFY check in locking_thread It tries to check against all zeros and looped for quite a few times. However after that we'll verify the same page with count_verify, while count_verify can never be zero. So it means if it's a zero page we'll detect it anyways with below code. There's yet another place we conditionally check the fault flag - just do it unconditionally. Link: https://lkml.kernel.org/r/20210310004511.51996-4-peterx@redhat.com Signed-off-by: Peter Xu Reviewed-by: Axel Rasmussen Cc: Andrea Arcangeli Cc: Nadav Amit Signed-off-by: Andrew Morton Signed-off-by: Stephen Rothwell (cherry picked from commit 9c42d387952986b4159ce304a14771a0534469b3 https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git akpm) Link: https://lore.kernel.org/patchwork/patch/1392478/ Conflicts: tools/testing/selftests/vm/userfaultfd.c (Manual rebase) Signed-off-by: Lokesh Gidra Bug: 160737021 Bug: 169683130 Change-Id: Iee4e4fa10db0b2a01cb4804087275d2714e477b4 --- tools/testing/selftests/vm/userfaultfd.c | 52 +----------------------- 1 file changed, 1 insertion(+), 51 deletions(-) diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c index 9c427d645b4c..270c0bb3d599 100644 --- a/tools/testing/selftests/vm/userfaultfd.c +++ b/tools/testing/selftests/vm/userfaultfd.c @@ -513,55 +513,6 @@ static void *locking_thread(void *arg) } else page_nr += 1; page_nr %= nr_pages; - - if (bounces & BOUNCE_VERIFY) { - count = *area_count(area_dst, page_nr); - if (!count) - fprintf(stderr, - "page_nr %lu wrong count %Lu %Lu\n", - page_nr, count, - count_verify[page_nr]), exit(1); - - - /* - * We can't use bcmp (or memcmp) because that - * returns 0 erroneously if the memory is - * changing under it (even if the end of the - * page is never changing and always - * different). - */ -#if 1 - if (!my_bcmp(area_dst + page_nr * page_size, zeropage, - page_size)) - fprintf(stderr, - "my_bcmp page_nr %lu wrong count %Lu %Lu\n", - page_nr, count, - count_verify[page_nr]), exit(1); -#else - unsigned long loops; - - loops = 0; - /* uncomment the below line to test with mutex */ - /* pthread_mutex_lock(area_mutex(area_dst, page_nr)); */ - while (!bcmp(area_dst + page_nr * page_size, zeropage, - page_size)) { - loops += 1; - if (loops > 10) - break; - } - /* uncomment below line to test with mutex */ - /* pthread_mutex_unlock(area_mutex(area_dst, page_nr)); */ - if (loops) { - fprintf(stderr, - "page_nr %lu all zero thread %lu %p %lu\n", - page_nr, cpu, area_dst + page_nr * page_size, - loops); - if (loops > 10) - exit(1); - } -#endif - } - pthread_mutex_lock(area_mutex(area_dst, page_nr)); count = *area_count(area_dst, page_nr); if (count != count_verify[page_nr]) { @@ -687,8 +638,7 @@ static int uffd_handle_page_fault(struct uffd_msg *msg) return 1; } else { /* Missing page faults */ - if (bounces & BOUNCE_VERIFY && - msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE) { + if (msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE) { fprintf(stderr, "unexpected write fault\n"); exit(1); }