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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: [PATCH v9 19/32] mm: handle soft-dirty and uffd-wp on PMD swap entries Date: Thu, 5 Nov 2026 10:39:03 -0800 Message-ID: <20261105183940.2236717-20-usama.arif@linux.dev> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261105183940.2236717-1-usama.arif@linux.dev> References: <20261105183940.2236717-1-usama.arif@linux.dev> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: 7pwsepib7nnsawfnbu48a4gofscc8daz X-Rspamd-Server: rspam01 X-Rspam-User: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: E710A120004 X-HE-Tag: 1793904103-47698 X-HE-Meta: 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 jSppwE9e w6Mx+bGc5deWutZhRgukKhBCTAsDpkFL/4+7+wDtKk/wT6NhsECUtsAl6DnC4xxakwV80ApcIta83gNLnSCUgfWStBlvG2lgeuZtarQ7uYA1/UfKgMo+jdeWoFfO8HSw9lYV5Ym4oDOG+Kr2Re4KZogggJ617BifoQaFG+fSBCgwV7DikiJc1LuzofL+StFglLDLD2zfOi1oLaoFbWi98hDhDvYRIgpmtQsd0kSCdZhKyQtE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 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 bfe9d6af76d5a..aa0c8c1be9b0d 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1663,7 +1663,7 @@ 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); } @@ -2491,7 +2491,7 @@ 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 acb540235e5a9..101ec72944cbf 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2626,7 +2626,8 @@ 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); @@ -2718,6 +2719,12 @@ 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); @@ -2778,7 +2785,7 @@ 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