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BACKPORT: FROMGIT: userfaultfd/selftests: drop VERIFY check in locking_thread

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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 <peterx@redhat.com>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
(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 <lokeshgidra@google.com>
Bug: 160737021
Bug: 169683130
Change-Id: Iee4e4fa10db0b2a01cb4804087275d2714e477b4
This commit is contained in:
Peter Xu 2021-03-18 17:01:53 +11:00 • committed by Michael Bestas
commit 30cd89e371
1 changed files with 1 additions and 51 deletions
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52
tools/testing/selftests/vm/userfaultfd.c
View file

@ -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);
}