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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=4292; i=yeoreum.yun@arm.com; h=from:subject:message-id; bh=MuRaI8x6GXzrvwzPsbKH9WYnwNTgr9phZb/ghgk7nkI=; b=owEB7QES/pANAwAKAW3Vw9FaxTEzAcsmYgBqtXXaIiT9BwKaFmYL+IRymkn1pS2cgMwCN8AJR jX5E9q/5yKJAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCarV12gAKCRBt1cPRWsUx M9CCC/4uKyIQhnU8tD0YMdkYRstxqpebMFuqAgDJCdJplKeWGziBfSV2btEkq3l6IaJ7C3bVHnb 3pDEFPHgL2O0ZT7QVQfq1qgfFJ+mf6/TiHidHnFWNwr+S77h7ltwAi3V8qzxk/x1mD2shDGGbsv anYESYv4f82duEtnyksxxPfYr3596oLcHCJXnSt6tUJsOcxpuOx3Vz+4HVbw03hNErKtMFZaAJu SQyqC338rRMCsFE1Evz/UI2geKUtW+V0UeednqsNO32cH0B7O0a6Q0Dw6tayJoMDRkrDKwUaHk7 2TcYBZqJ4Cr5jDyWUpfhgtU2vRigVuZtxfjomXTgTsMBogNAz4AQsDj385YN7FJOBjODTovX3AE WnAZ5UlSSdVRQuI8RuIDkrJeYD2xTmpmNehRhJNaFI+fFa6/7y+nyCM9BhcvlpBWrzqwlBmwLnd i12uy3RllTdMYX57SEYZAR1OyuxUu39IpgcEiiqjSJtqf4BOzdFYMkKQa/RRb2kmiU1Sw= X-Developer-Key: i=yeoreum.yun@arm.com; a=openpgp; fpr=2D83E092DD0533B85875A49D6DD5C3D15AC53133 X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: BC620100009 X-Rspam-User: X-Stat-Signature: 9h8yojstscjb5jhqhckypxahyho7sce5 X-HE-Tag: 1790277090-725566 X-HE-Meta: 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 GeYSys6I sgz9gL89kjdBIp949yCXr/HnvC7hVhB+pU33VLflsjw0W82GWwHAqwyVrkNLK+U4PZKf3WOwvvmAu96eNenCfInMC5sjJOWFrSJqAeekpcWLWrgGxgvEIutkT2ZRuK/e08dpmyKhKEAKR4Y3pgWAlZrf/AoBEdd+GPlXtoR9Y8PptpZhBXxX2k8uCnX/AcFgiBeoEKYXq9gua5Qrl2UinUNhHAu10dPNVOXTkP+xzV4M3qkScilsv7pltaFM9YaPWzs5cxk5PX/dDApl9+duWeI6pJfmDWpFeNVzrm4crEZH9B4J5ZWucZgdq6R5ImhnHlD9gyDuvj+bu6gUEGbpGfXumtD3Wmvrcg/q+ 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 v8: - add intermediate patch for __check_pmd_huge(). - add r-b, a-b tags. - Link to v7: https://lore.kernel.org/r/20260921-fix_split-v7-0-d25ec991159f@arm.com 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 (4): kselftest: mm: prevent random failure of huge page split for khugepaged kselftest: mm: replace usage of /proc/self/smaps for __check_pmd_huge() kselftest: mm: integrate huge page checks 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 | 127 ++++++++++++--------- tools/testing/selftests/mm/vm_util.h | 1 - 6 files changed, 102 insertions(+), 89 deletions(-) --- base-commit: fff9c87241bb46aa09ed3a91d6002cba966d7776 change-id: 20260820-fix_split-f44939ec44b8 Best regards, -- Sincerely, Yeoreum Yun