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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: C21984001C X-Rspamd-Server: rspam04 X-Rspam-User: X-Stat-Signature: ffxwxxfkjxo5bmuhdw3qxadsgp7crofe X-HE-Tag: 1756731909-918544 X-HE-Meta: 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 vTcya/3q 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 01.09.25 14:54, David Hildenbrand wrote: > On 01.09.25 14:51, Wei Yang wrote: >> On Mon, Sep 01, 2025 at 11:32:11AM +0200, David Hildenbrand wrote: >>> On 31.08.25 03:32, Zi Yan wrote: >>>> On 29 Aug 2025, at 22:31, Wei Yang wrote: >>>> >>>>> The check of is_backed_by_folio() is done on each page. >>>>> >>>>> Directly move pointer to next page instead of increase one and check if >>>>> it is page size aligned. >>>>> >>>>> Signed-off-by: Wei Yang >>>>> --- >>>>> tools/testing/selftests/mm/split_huge_page_test.c | 5 ++--- >>>>> 1 file changed, 2 insertions(+), 3 deletions(-) >>>>> >>>>> diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c >>>>> index 10ae65ea032f..7f7016ba4054 100644 >>>>> --- a/tools/testing/selftests/mm/split_huge_page_test.c >>>>> +++ b/tools/testing/selftests/mm/split_huge_page_test.c >>>>> @@ -423,9 +423,8 @@ static void split_pte_mapped_thp(void) >>>>> >>>>> /* smap does not show THPs after mremap, use kpageflags instead */ >>>>> thp_size = 0; >>>>> - for (i = 0; i < pagesize * 4; i++) >>>>> - if (i % pagesize == 0 && >>>>> - is_backed_by_folio(&pte_mapped[i], pmd_order, pagemap_fd, kpageflags_fd)) >>>>> + for (i = 0; i < pagesize * 4; i += pagesize) >>>>> + if (is_backed_by_folio(&pte_mapped[i], pmd_order, pagemap_fd, kpageflags_fd)) >>>>> thp_size++; >>>>> >>>>> if (thp_size != 4) >>>> >>>> It might be better to add >>>> >>>> if (pte_mapped[i] != (char)i) >>>> ksft_exit_fail_msg("%ld byte corrupted\n", i); >>>> >>>> instead to make sure mremap() does not change pte_mapped[] values. >>> >>> We do have a corruption check later in that function, so I think we can just >>> keep it simple here. >>> >>> So this as is LGTM >>> >>> Acked-by: David Hildenbrand >>> >>> As noted, we should just move from mremap() to mprotect() or sth like that >>> which has clearer semantics. >>> >> >> If my understanding is correct, we should >> >> mmap 4 PMD_SIZE region with RW >> madvise and fault in to allocate pmd-mapped thp >> mprotect first page of each PMD to read-only to split to pte-mapped thp >> check whether the page is backed by pmd-order folio >> >> Is this the correct way? > > Yeah, I would just mprotect(PROT_READ) the first page of each PMD. That > will trigger a PTE-mapping of the THP reliably. Zi Yan mentions that there is a reason we are using mremap in the other thread. So likely best to just keep it as is unless we can understand that it definitely can done simpler. -- Cheers David / dhildenb