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Howlett , ryan.roberts@arm.com, Vlastimil Babka , 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, Usama Arif Subject: [RESEND v7 16/29] mm: handle soft-dirty and uffd-wp on PMD swap entries Date: Mon, 14 Sep 2026 05:28:06 -0700 Message-ID: <20260914122950.3283997-17-usama.arif@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260914122950.3283997-1-usama.arif@linux.dev> References: <20260914122950.3283997-1-usama.arif@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: s5yofp8yee133dwnuiqpeqxrp4tnd9ya X-Rspamd-Queue-Id: E6D19A0009 X-Rspamd-Server: rspam07 X-HE-Tag: 1789389102-868863 X-HE-Meta: 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 bBRiQf/j 3EwoTwu+9JOM/hFx6hGxQTjfN+zWkwqYpybJzYEG564j11sKWOeaAk8KaegP5GaFkl3g10WCqbstEFa9Qz02rXFPqBOa8S4h+9YKTjst0A3cX1txpketgTwSOsg3xGQbrJ5D1RT4PSdtF9/v4A060wEHSPq5EYkVxirN189brEsfXc0NhjKfERfcWzV9Y8REzpMrng4toHYVWKXNRUM/jRqMR4Sn/ypjntRXR6K0tnelRrXs= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Soft-dirty and uffd-wp live in the PMD, not in the swap entry, so every path that manipulates them for a PMD migration entry has to do the same for a PMD swap entry. Otherwise clearing soft-dirty skips a swapped-out THP, UFFDIO_WRITEPROTECT does not arm it, and mremap does not mark the destination. change_huge_pmd() needs nothing beyond dropping its thp_migration_supported() gate: a PMD swap entry encodes no write permission, so it falls into the default arm of change_non_present_huge_pmd() and picks up only the uffd-wp update. Signed-off-by: Usama Arif --- fs/proc/task_mmu.c | 4 ++-- mm/huge_memory.c | 11 +++++++++-- 2 files changed, 11 insertions(+), 4 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index aa3f4d54a8580..ad0d4c7f0988b 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1654,7 +1654,7 @@ static void clear_soft_dirty_pmd(struct vm_area_struct *vma, pmd = pmd_clear_soft_dirty(pmd); set_pmd_at(vma->vm_mm, addr, pmdp, pmd); - } else if (pmd_is_migration_entry(pmd)) { + } else if (pmd_is_migration_entry(pmd) || pmd_is_swap_entry(pmd)) { pmd = pmd_swp_clear_soft_dirty(pmd); set_pmd_at(vma->vm_mm, addr, pmdp, pmd); } @@ -2480,7 +2480,7 @@ static void make_uffd_wp_pmd(struct vm_area_struct *vma, old = pmdp_invalidate_ad(vma, addr, pmdp); pmd = pmd_mkuffd(old); set_pmd_at(vma->vm_mm, addr, pmdp, pmd); - } else if (pmd_is_migration_entry(pmd)) { + } else if (pmd_is_migration_entry(pmd) || pmd_is_swap_entry(pmd)) { pmd = pmd_swp_mkuffd(pmd); set_pmd_at(vma->vm_mm, addr, pmdp, pmd); } diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 6dfe8ef6dd371..d3d0fec9a5ff3 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2660,7 +2660,8 @@ static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl, static pmd_t move_soft_dirty_pmd(pmd_t pmd) { if (pgtable_supports_soft_dirty()) { - if (unlikely(pmd_is_migration_entry(pmd))) + if (unlikely(pmd_is_migration_entry(pmd) || + pmd_is_swap_entry(pmd))) pmd = pmd_swp_mksoft_dirty(pmd); else if (pmd_present(pmd)) pmd = pmd_mksoft_dirty(pmd); @@ -2752,6 +2753,12 @@ static void change_non_present_huge_pmd(struct mm_struct *mm, pmd_t newpmd; VM_WARN_ON(!pmd_is_valid_softleaf(*pmd)); + + /* + * Note that a PMD swap entry falls into the default branch below: it + * does not encode write permission in the entry type, so only the + * uffd_wp flag update at the end applies to it. + */ if (softleaf_is_migration_write(entry)) { const struct folio *folio = softleaf_to_folio(entry); @@ -2812,7 +2819,7 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, if (!ptl) return 0; - if (thp_migration_supported() && pmd_is_valid_softleaf(*pmd)) { + if (pmd_is_valid_softleaf(*pmd)) { change_non_present_huge_pmd(mm, addr, pmd, uffd_prot, uffd_prot_resolve); goto unlock; -- 2.53.0-Meta