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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Kevin Brodsky Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Yeoreum Yun X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4056; i=yeoreum.yun@arm.com; h=from:subject:message-id; bh=eEcKOlvZviz+OS9o/BwOzLKaVMvfJZjmjmnn1tcF9Dk=; b=owEB7QES/pANAwAKAW3Vw9FaxTEzAcsmYgBqsQmISXAW5/OuRPdd3iSJezNDNx8zKcSXlaZRY c1lFqUQpAuJAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCarEJiAAKCRBt1cPRWsUx M/pUC/4qHK7/4NifLumv1mggmsHkyq908VAh96FDwf0nywEkR8pjtcGnIf/fI2YGpxVdKtBX21L IpYF3NZsWt0nkk3Jgjr5HWuMtLJCkIJS14L6QUWdr5dRbOpSRMHny/zYlAhu2QYQk7XW4vJu9Fz LbuGyQG7Xy/41PPJAROx5cwaZbRuSj21onU4bA8HNvR4yVpU5nSSrIxshpLh6gvn37pAFaxh9q+ 1EvqLZRGrDpRRytPx1/Z3fwdAMpgkylG5vvdw0QrSYTlaMn0XYBMOkwxZ8IPbKFydq10LRd3n3X ORDsDjBBTcS5QgLiZaMIgNlv8zi0c62s+mUpIdL20LCdXgulKh1HlnW4tq3eohjnCI9jBwuooWK jL5b1SN9aOMHi0b524cXyrGyx8SfSCxkvPyazjszWXxxpiUoY6/8kELI53Y99d/sIOMsj8Yev/b TRWmuUI1HFUPvwZbhcJINU9BD9ariMxFN0VQjL1Rbbos3vi+6YOtk0Pxf2P1pBXQhPLTw= X-Developer-Key: i=yeoreum.yun@arm.com; a=openpgp; fpr=2D83E092DD0533B85875A49D6DD5C3D15AC53133 X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: C66AB180004 X-Stat-Signature: c87y873yciaqnzmp5s77k1k1ispiy1t6 X-HE-Tag: 1789987214-392736 X-HE-Meta: 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 vTe+yI6i kNtZQ7Cl2OyKGpzXFWxjU5ZWLDMevYO7Ldx+V2GiaIQ4NAM+hmZf41+iFzaX6c0WeOR5mLzbWgQxdOumrLFlj8oVhZPELOCfQtf6dCtvuKVap2dih2eCPv9P7rFqVzdG1KXGtXPiqsHa+vceeyCWdcWvQXwBxb5dHEmKZhkQNIQHYMBbclWyvbJDD92HZwjo01dfYdCstuAgJtn9LCfwIZYxp4QF0W3XvXLYLH4+kfD4Q7SgtBGOedmzwaHRMP0bA44XbsbCwNGADqwSEtaJRw5YRw8DDzDxpXQAfgHc98di4Vvpua09TxD33TkoPC/86pGcOUmQwAPBNO3djqYi2/FdiLWfro66rxFnu Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: split_huge_page_test can fail for the following reasons: 1. During the test, khugepaged may collapse previously split pages again, causing intermittent failures. 2. Since glibc commit 321e1fc73f (“malloc: Enable 2MB THP by default on AArch64”), glibc may call madvise(MADV_HUGEPAGE) for sufficiently large allocations made by memalign(). The underlying VMA may start at a different address from the aligned address returned by memalign(). Moreover, a subsequent madvise(MADV_HUGEPAGE) call does not split the VMA because it already has the same advice. This causes the test to fail because the check_huge_xxx() helpers incorrectly require the address returned by memalign() to match the VMA start address reported in /proc/self/smaps. Address these issues by applying MADV_NOHUGEPAGE after faulting in the huge page, preventing khugepaged from collapsing it again, and instead of relying on /proc/self/smaps, use /proc/self/pagemap and /proc/kpageflags to detect huge-page mappings and large folios: 1. If hpage_size == pmd_pagesize, check PAGE_IS_HUGE instead of using check_large_folios(), since only the mapping type matters. This identifies PMD-mapped huge pages. 2. Otherwise, use check_large_folios() to detect large folios. This covers mTHP cases. 3. Check the folio flags according to the type of huge page. Since check_huge_shmem() was required to distinguish shmem huge pages because /proc/self/smaps reports them using a dedicated “ShmemPmdMapped” entry, as opposed to “FilePmdMapped” for file-backed huge pages. Now that /proc/self/smaps is no longer used to detect huge pages and /proc/kpageflags is used instead, it is sufficient to distinguish between file-backed and anonymous pages since the ShmemPmdMapped is also kind of file-backed. Therefore, remove check_huge_shmem() and use check_huge_file() instead. This patch based on mm-unstable --- Changes in v7: - change khugepaged's check_huge() callback. - Link to v6: https://lore.kernel.org/r/20260914-fix_split-v6-0-16ed7123800b@arm.com Changes in v6: - drop alloc_isolated_mem() patch. - remove check_huge_shmem(). - Link to v5: https://lore.kernel.org/r/20260907-fix_split-v5-0-822b810458bc@arm.com Changes in v5: - rename madv_nohuge() to disable_khugepaged(). - Link to v4: https://lore.kernel.org/r/20260902-fix_split-v4-0-85f03905f7b1@arm.com Changes in v4: - reparse commit message. - introduce alloc_isolated_mem(). - make madv_nohuge() helper according to suggestion. - Link to v3: https://lore.kernel.org/r/20260828-fix_split-v3-0-374022586a4b@arm.com Changes in v3: - change message in case of failure of madvise() with MADV_NOHUGEPAGE. - fix collapse_single_mthp (mthp_khugepaged:anon) test case failure. - Link to v2: https://lore.kernel.org/all/20260826-fix_split-v2-0-71153c7f579a@arm.com/ Changes in v2: - rebase to mm-unstable. - add message in case of failure of madvise() with MADV_NOHUGEPAGE. - fix wrong setup expected_huge in check_huge_shmem(). - Link to v1: https://lore.kernel.org/r/20260820-fix_split-v1-0-ab430c58c7cf@arm.com --- Yeoreum Yun (3): kselftest: mm: prevent random failure of huge page split for khugepaged kselftest: mm: replace usage of /proc/self/smaps for check_huge_xxx() helper kselftest: mm: remove check_huge_shmem() tools/testing/selftests/mm/folio_split_race_test.c | 2 +- tools/testing/selftests/mm/khugepaged.c | 38 +----- tools/testing/selftests/mm/split_huge_page_test.c | 19 +++ tools/testing/selftests/mm/uffd-common.c | 4 +- tools/testing/selftests/mm/vm_util.c | 134 ++++++++++++--------- tools/testing/selftests/mm/vm_util.h | 1 - 6 files changed, 108 insertions(+), 90 deletions(-) --- base-commit: 8d61431ed2607386b427752505379536eb634ce8 change-id: 20260820-fix_split-f44939ec44b8 Best regards, -- Sincerely, Yeoreum Yun