Re: [Patch v2] selftests/mm: check content to see whether mremap corrupt data

[David Hildenbrand <david@redhat.com>]

On 01.09.25 10:11, wang lian wrote:
> 
>> I'm confused, don't we have that exact check later in the function?
> 
>> Your v1 might have been better, unless I am missing something.
> 
> Hi David,
> 
> Perhaps you missed this in the v1 feedback:
> https://lore.kernel.org/linux-mm/E0C570E7-C4CD-4E41-9590-DDB64757CA2C@nvidia.com/ ?

We have:

	/* smap does not show THPs after mremap, use kpageflags instead */
	thp_size = 0;
	for (i = 0; i < pagesize * 4; i++) {
		if (pte_mapped[i] != (char)i)
			ksft_exit_fail_msg("%ld byte corrupted\n", i);

		if (i % pagesize == 0 &&
		    !is_backed_by_folio(&pte_mapped[i], 0, pagemap_fd, kpageflags_fd))
			thp_size++;
	}

Sure, it's after the split, but if mremap would have corrupted the pages, surely
it would still be corrupt after the mremap+split.

-- 
Cheers

David / dhildenb