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Sun, 04 Oct 2026 03:08:55 +0000 X-Mizu-Trace-ID: 5eb3b10a722064f6 X-Migadu-Flow: FLOW_OUT From: Lance Yang To: usama.arif@linux.dev Cc: akpm@linux-foundation.org, david@kernel.org, chrisl@kernel.org, kasong@tencent.com, ljs@kernel.org, ziy@nvidia.com, linux-mm@kvack.org, ying.huang@linux.alibaba.com, baoquan.he@linux.dev, willy@infradead.org, youngjun.park@lge.com, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, alex@ghiti.fr, kas@kernel.org, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, nico.pache@linux.dev, liam@infradead.org, ryan.roberts@arm.com, vbabka@kernel.org, lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, yosry@kernel.org, qi.zheng@linux.dev, luizcap@redhat.com, kernel-team@meta.com Subject: Re: [PATCH v8 00/30] mm: PMD-level swap entries for anonymous THPs Date: Sun, 4 Oct 2026 11:08:44 +0800 Message-ID: <20261004030844.90483-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20261002095503.3585565-1-usama.arif@linux.dev> References: <20261002095503.3585565-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: gkgyya6fr9frctarncg4w1udu59szdk5 X-Rspamd-Queue-Id: 818E8C0002 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1791083337-118713 X-HE-Meta: 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 pj8qRCY2 1ORMzBJ4sCsD3PQCYezi6sHOjSVch8WFcXN9Y459vGfNCVUybUgvoKcxaMsXa8dewHEHRljdq37RrhJuKwy1UFbB+BpP3QGYxtI9fMxxRXV712mCbh2R/JlQna3nSw1a9+xWo4EdX8XX7chmXvI0UOy8Vng3lkDClYALKhATZ7SV8+ZgJleA4Ohngb1F1AAWMwjf3Ujk6NzI5RBtAckLyks8dogqEH2Wx0/pwP81XxdLDu4h7eSAw2Hl6MrodcjboeEHv Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hey Usama, Staring at the swap-entry bits across architectures, and RISC-V looks a bit off in that regard ... With Svrsw60t59b and CONFIG_MEM_SOFT_DIRTY=y, setting swap soft-dirty also sets _PAGE_EXEC. A migration PMD then looks present ... so the fault handler skips the migration wait :( And yeah, this is a pre-existing bug. I've sent a separate fix for it. https://lore.kernel.org/linux-mm/20261004030312.90163-1-lance.yang@linux.dev/ BTW, could we also add more checks to pmd_leaf_soft_dirty_tests() so we catch this kind of issue early? Setting a swap flag shouldn't make a non-present PMD present, IIUC. ---8<--- diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c index 863111c6d4eb..80686e2baaa1 100644 --- a/mm/debug_vm_pgtable.c +++ b/mm/debug_vm_pgtable.c @@ -762,7 +762,9 @@ static void __init pmd_leaf_soft_dirty_tests(struct pgtable_debug_args *args) WARN_ON(!pmd_is_huge(pmd)); WARN_ON(!pmd_is_valid_softleaf(pmd)); - WARN_ON(!pmd_swp_soft_dirty(pmd_swp_mksoft_dirty(pmd))); + pmd = pmd_swp_mksoft_dirty(pmd); + WARN_ON(!pmd_swp_soft_dirty(pmd)); + WARN_ON(pmd_present(pmd)); WARN_ON(pmd_swp_soft_dirty(pmd_swp_clear_soft_dirty(pmd))); } #else /* !CONFIG_TRANSPARENT_HUGEPAGE */ -- [...] Cheers, Lance