Re: [PATCH v5 09/10] userfaultfd/selftests: reinitialize test context in each test

Peter Xu
2021-05-18T20:57:25Z

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On Tue, Apr 27, 2021 at 03:52:43PM -0700, Axel Rasmussen wrote:
> Currently, the context (fds, mmap-ed areas, etc.) are global. Each test
> mutates this state in some way, in some cases really "clobbering it"
> (e.g., the events test mremap-ing area_dst over the top of area_src, or
> the minor faults tests overwriting the count_verify values in the test
> areas). We run the tests in a particular order, each test is careful to
> make the right assumptions about its starting state, etc.
>
> But, this is fragile. It's better for a test's success or failure to not
> depend on what some other prior test case did to the global state.
>
> To that end, clear and reinitialize the test context at the start of
> each test case, so whatever prior test cases did doesn't affect future
> tests.
>
> This is particularly relevant to this series because the events test's
> mremap of area_dst screws up assumptions the minor fault test was
> relying on. This wasn't a problem for hugetlb, as we don't mremap in
> that case.
>
> Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>

Hi, Andrew,

There's a conflict on the uffd test case with v5.13-rc1-mmots-2021-05-13-17-23
between this patch and the uffd pagemap series, so I think we may need to queue
another fixup patch (to be squashed into this patch of Axel's) which is
attached.

Thanks,

--
Peter Xu

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From 745402175cc5670475df8e6c6bd03b6268f4175d Mon Sep 17 00:00:00 2001
From: Peter Xu <peterx@redhat.com>
Date: Tue, 18 May 2021 16:50:36 -0400
Subject: [PATCH] fixup! userfaultfd/selftests: reinitialize test context in
each test

Signed-off-by: Peter Xu <peterx@redhat.com>
---
tools/testing/selftests/vm/userfaultfd.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index c4150b4fbd17..f78816130c7f 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -1326,7 +1326,7 @@ static void userfaultfd_pagemap_test(unsigned int test_pgsize)
/* Flush so it doesn't flush twice in parent/child later */
fflush(stdout);

- uffd_test_ops->release_pages(area_dst);
+ uffd_test_ctx_init(0);

if (test_pgsize > page_size) {
/* This is a thp test */
@@ -1338,9 +1338,6 @@ static void userfaultfd_pagemap_test(unsigned int test_pgsize)
err("madvise(MADV_NOHUGEPAGE) failed");
}

- if (userfaultfd_open(0))
- err("userfaultfd_open");
-
uffdio_register.range.start = (unsigned long) area_dst;
uffdio_register.range.len = nr_pages * page_size;
uffdio_register.mode = UFFDIO_REGISTER_MODE_WP;
@@ -1383,7 +1380,6 @@ static void userfaultfd_pagemap_test(unsigned int test_pgsize)
pagemap_check_wp(value, false);

close(pagemap_fd);
- close(uffd);
printf("done\n");
}

--
2.31.1