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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=3902; i=yeoreum.yun@arm.com; h=from:subject:message-id; bh=LxmCXA3B9Y6uXrZwwE08LbuQHc/4/4X46xSVGb8t8X0=; b=owEB7QES/pANAwAKAW3Vw9FaxTEzAcsmYgBqp6KE6oDgS3nL0RCwPvgtF3ebGpW3grQBMtuz8 /kV3r9amu2JAbMEAAEKAB0WIQQtg+CS3QUzuFh1pJ1t1cPRWsUxMwUCaqeihAAKCRBt1cPRWsUx MwTcDACuCkl+GS9Z6IJhWqt/uoF9a1l8VbBSsChbNS6udnHWgneWZ5DoQLXamd+6WoPxxZijjY4 faYkEFObwG9Hs9TTusECQ7fYCjpjckMBQq0HJLP1K9LpvV7zGj+AhHH+Ga1xVAaL+qT4rC/eGOc Hu9yCPmdeO9VJlcxJZp1reKM0DLvjs9GQTVXduRgnN8KBpdfLqvBEZaFk6sucmCZEZ7AKcszLYf wMlmhqsQQV9SMRLb8St+zC7w5aQx+scbmXCZk1+l2Q6FBej91mKEyNxCpbNw99+UTYXJoNQ7Woy Nlw/PdQXF2bXB3koHGxnd3ndhPWbMX35X6b8lWjjhtA/F+832UHc3ZnEELUXz1LoBtKdJ5yRUBk 8XXMmWx9OYEqqUck0mqHHLF86fQ5X5caD/3ZVEx2KjL8t+qXcDWqJjo2LCILUAbABcLFLbcakst mdqSaMUzYKcFk5Qe5BU+2bX2c6W1NJbCwkRA0rUHd6Dm2Bf0Go0RJI536LrGfDj73usGg= X-Developer-Key: i=yeoreum.yun@arm.com; a=openpgp; fpr=2D83E092DD0533B85875A49D6DD5C3D15AC53133 X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 9FCE1C0008 X-Stat-Signature: m4njwdjcmd1bjd9ejeek14d183xxj1w7 X-Rspam-User: X-HE-Tag: 1789371018-307979 X-HE-Meta: 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 ptJiOiMK 83E+MzCy3CZGCPJGqt9ytj6q8ndlQTYv/1MLlBgSsLhPxqxBRFKG7HikvEwg4wwZEGBZ5A2W6U/QpkcSlhm/7oodGaCZzrmrv+cHD+obeqIMLx8otTeO3zUs09/4pw1/RENS+/gPhQ1WBjgHUREDKmY1BXEDMQD9Yb6bM0pKwzENACEEW6co1vBBUghb/8/TBIvr79mOy5uDh7po8b/cuYPg8YmNsfCNKBmlCDJo+YrNcM5k1BJDtWtDmKVML8YT2RQ0Q/NQSZ5sDeBw6T8Jwk8KNIlgymSWH6E2YD/Dbz+GtzKJz76VMTigaPkJkBRHI+X6GvCbeZJWntOEVr4gqSdIG5PvFeFEhbIxN 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 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 | 5 +- 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, 104 insertions(+), 61 deletions(-) --- base-commit: 6b41451631cabf9ea3b384c2a099088e1598f963 change-id: 20260820-fix_split-f44939ec44b8 Best regards, -- Sincerely, Yeoreum Yun