On Fri, Jul 22, 2022 at 04:07:47PM +0200, David Hildenbrand wrote:
> On 22.07.22 16:00, David Hildenbrand wrote:
> > On 22.07.22 15:44, Peter Xu wrote:
> >> On Fri, Jul 22, 2022 at 09:17:34AM +0200, David Hildenbrand wrote:
> >>> On 21.07.22 20:33, Peter Xu wrote:
> >>>> Add two soft-diryt test cases for mprotect() on both anon or file.
> >>>
> >>> s/soft-diryt/soft-dirty/
> >>
> >> Fixed.
> >>
> >>>
> >>>>
> >>>> Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
> >>>> ---
> >>>> tools/testing/selftests/vm/soft-dirty.c | 69 ++++++++++++++++++++++++-
> >>>> 1 file changed, 68 insertions(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/tools/testing/selftests/vm/soft-dirty.c b/tools/testing/selftests/vm/soft-dirty.c
> >>>> index 08ab62a4a9d0..7d93906aa43f 100644
> >>>> --- a/tools/testing/selftests/vm/soft-dirty.c
> >>>> +++ b/tools/testing/selftests/vm/soft-dirty.c
> >>>> @@ -121,13 +121,78 @@ static void test_hugepage(int pagemap_fd, int pagesize)
> >>>> free(map);
> >>>> }
> >>>>
> >>>> +static void test_mprotect(int pagemap_fd, int pagesize, bool anon)
> >>>> +{
> >>>> + const char *type[] = {"file", "anon"};
> >>>> + const char *fname = "./soft-dirty-test-file";
> >>>> + int test_fd;
> >>>> + char *map;
> >>>
> >>> Instead of fname, unlink, open, close, unlink you can use a tmpfile
> >>>
> >>> FILE *file;
> >>>
> >>> file = tmpfile();
> >>> if (!file) {
> >>> ksft_test_result_fail("tmpfile() failed\n");
> >>> return;
> >>> }
> >>> test_fd = fileno(file);
> >>
> >> Note that tmpfile() should by default fetch from /tmp which is very
> >> possibly a tmpfs afaict. It's tricky in this special test case since I
> >> don't think tmpfs can trigger this bug (shmem doesn't define page_mkwrite).
> >>
> >
> > I don't think we need that? SOFTDIRTY tracking enabled should be
> > sufficient, or what am I missing?
> >
>
> I think you're right that it doesn't work with tmpfile. I do wonder why,
> because I'd have thought that it's sufficient for
> vma_wants_writenotify() to return "1" due to the
> vma_soft_dirty_enabled() check.
I can't say I know the whole rational of this, but I think it's below that
will start to return 0 already before the soft-dirty check:
if (pgprot_val(vm_page_prot) !=
pgprot_val(vm_pgprot_modify(vm_page_prot, vm_flags)))
return 0;
in vma_wants_writenotify().
--
Peter Xu
