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([177.73.136.69]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7af827effebsm118409b3a.57.2025.11.05.10.51.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Nov 2025 10:51:46 -0800 (PST) From: Pedro Demarchi Gomes To: David Hildenbrand , Andrew Morton Cc: Xu Xin , Chengming Zhou , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Pedro Demarchi Gomes , David Hildenbrand Subject: [PATCH v4 1/3] Revert "mm/ksm: convert break_ksm() from walk_page_range_vma() to folio_walk" Date: Wed, 5 Nov 2025 15:49:10 -0300 Message-ID: <20251105184912.186329-2-pedrodemargomes@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251105184912.186329-1-pedrodemargomes@gmail.com> References: <20251105184912.186329-1-pedrodemargomes@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This reverts commit e317a8d8b4f600fc7ec9725e26417030ee594f52 and changes function break_ksm_pmd_entry() to use folios. This reverts break_ksm() to use walk_page_range_vma() instead of folio_walk_start(). Change break_ksm_pmd_entry() to call is_ksm_zero_pte() only if we know the folio is present, and also rename variable ret to found. This will make it easier to later modify break_ksm() to perform a proper range walk. Suggested-by: David Hildenbrand (Red Hat) Acked-by: David Hildenbrand (Red Hat) Signed-off-by: Pedro Demarchi Gomes --- mm/ksm.c | 64 ++++++++++++++++++++++++++++++++++++++++++-------------- 1 file changed, 48 insertions(+), 16 deletions(-) diff --git a/mm/ksm.c b/mm/ksm.c index 4f672f4f2140..9f74baf01e46 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -607,6 +607,48 @@ static inline bool ksm_test_exit(struct mm_struct *mm) return atomic_read(&mm->mm_users) =3D=3D 0; } =20 +static int break_ksm_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned lo= ng next, + struct mm_walk *walk) +{ + struct folio *folio =3D NULL; + spinlock_t *ptl; + pte_t *pte; + pte_t ptent; + int found; + + pte =3D pte_offset_map_lock(walk->mm, pmd, addr, &ptl); + if (!pte) + return 0; + ptent =3D ptep_get(pte); + if (pte_present(ptent)) { + folio =3D vm_normal_folio(walk->vma, addr, ptent); + } else if (!pte_none(ptent)) { + swp_entry_t entry =3D pte_to_swp_entry(ptent); + + /* + * As KSM pages remain KSM pages until freed, no need to wait + * here for migration to end. + */ + if (is_migration_entry(entry)) + folio =3D pfn_swap_entry_folio(entry); + } + /* return 1 if the page is an normal ksm page or KSM-placed zero page */ + found =3D (folio && folio_test_ksm(folio)) || + (pte_present(ptent) && is_ksm_zero_pte(ptent)); + pte_unmap_unlock(pte, ptl); + return found; +} + +static const struct mm_walk_ops break_ksm_ops =3D { + .pmd_entry =3D break_ksm_pmd_entry, + .walk_lock =3D PGWALK_RDLOCK, +}; + +static const struct mm_walk_ops break_ksm_lock_vma_ops =3D { + .pmd_entry =3D break_ksm_pmd_entry, + .walk_lock =3D PGWALK_WRLOCK, +}; + /* * We use break_ksm to break COW on a ksm page by triggering unsharing, * such that the ksm page will get replaced by an exclusive anonymous page. @@ -623,26 +665,16 @@ static inline bool ksm_test_exit(struct mm_struct *mm) static int break_ksm(struct vm_area_struct *vma, unsigned long addr, bool = lock_vma) { vm_fault_t ret =3D 0; - - if (lock_vma) - vma_start_write(vma); + const struct mm_walk_ops *ops =3D lock_vma ? + &break_ksm_lock_vma_ops : &break_ksm_ops; =20 do { - bool ksm_page =3D false; - struct folio_walk fw; - struct folio *folio; + int ksm_page; =20 cond_resched(); - folio =3D folio_walk_start(&fw, vma, addr, - FW_MIGRATION | FW_ZEROPAGE); - if (folio) { - /* Small folio implies FW_LEVEL_PTE. */ - if (!folio_test_large(folio) && - (folio_test_ksm(folio) || is_ksm_zero_pte(fw.pte))) - ksm_page =3D true; - folio_walk_end(&fw, vma); - } - + ksm_page =3D walk_page_range_vma(vma, addr, addr + 1, ops, NULL); + if (WARN_ON_ONCE(ksm_page < 0)) + return ksm_page; if (!ksm_page) return 0; ret =3D handle_mm_fault(vma, addr, --=20 2.43.0