From nobody Sun Feb 8 05:08:14 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 91C7D1B2186 for ; Tue, 7 Oct 2025 06:31:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759818669; cv=none; b=MKmqVI5KzHSWtSA1E964sg6DPs80e0pZsfKU1GFflpRG1v+d/0ksSPHTNA1grWOwE24TgghETFr/b6/rb3XRpanxnrCgqp9Q4uPY4FuM82hRVyMDmU/ANiPs3ca0J0rUgJm0LXJNi7sS5lgKUJuqgLidNl4pbnM6GgZOaXfFk7c= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759818669; c=relaxed/simple; bh=86mtmsHV9KCOVXlETPaFOszfsui00cGAhiUOBYDW93g=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=FOtbzAXBUONNhYckzZIeheeOT/oUVZEVx0oibp+ojA1HXK05FHksLg1ocQ9vPN8/oE8mNnvlUw5ZlE5+C0e7hkFlYxR/3ESwNFuCBlQ4baOLKZ9rPM1swwIWLCLWEjoO4SwbxVQkh5uGT09H9AjqLQnMoAjm/mualT8MmqG3my8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E0FF714BF; Mon, 6 Oct 2025 23:30:58 -0700 (PDT) Received: from ergosum.cambridge.arm.com (ergosum.cambridge.arm.com [10.1.196.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id D75343F59E; Mon, 6 Oct 2025 23:31:05 -0700 (PDT) From: Anshuman Khandual To: linux-mm@kvack.org Cc: Anshuman Khandual , Andrew Morton , David Hildenbrand , linux-kernel@vger.kernel.org Subject: [PATCH] mm: Replace READ_ONCE() with standard page table accessors Date: Tue, 7 Oct 2025 07:31:00 +0100 Message-Id: <20251007063100.2396936-1-anshuman.khandual@arm.com> X-Mailer: git-send-email 2.30.2 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" Replace all READ_ONCE() with a standard page table accessors i.e pxdp_get() that defaults into READ_ONCE() in cases where platform does not override. Cc: Andrew Morton Cc: David Hildenbrand Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Anshuman Khandual Acked-by: David Hildenbrand Reviewed-by: Dev Jain Reviewed-by: Lance Yang Reviewed-by: Wei Yang --- mm/gup.c | 10 +++++----- mm/hmm.c | 2 +- mm/memory.c | 4 ++-- mm/mprotect.c | 2 +- mm/sparse-vmemmap.c | 2 +- mm/vmscan.c | 2 +- 6 files changed, 11 insertions(+), 11 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index 0bc4d140fc07..37e2af5ed96d 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -964,7 +964,7 @@ static struct page *follow_pud_mask(struct vm_area_stru= ct *vma, struct mm_struct *mm =3D vma->vm_mm; =20 pudp =3D pud_offset(p4dp, address); - pud =3D READ_ONCE(*pudp); + pud =3D pudp_get(pudp); if (!pud_present(pud)) return no_page_table(vma, flags, address); if (pud_leaf(pud)) { @@ -989,7 +989,7 @@ static struct page *follow_p4d_mask(struct vm_area_stru= ct *vma, p4d_t *p4dp, p4d; =20 p4dp =3D p4d_offset(pgdp, address); - p4d =3D READ_ONCE(*p4dp); + p4d =3D p4dp_get(p4dp); BUILD_BUG_ON(p4d_leaf(p4d)); =20 if (!p4d_present(p4d) || p4d_bad(p4d)) @@ -3080,7 +3080,7 @@ static int gup_fast_pud_range(p4d_t *p4dp, p4d_t p4d,= unsigned long addr, =20 pudp =3D pud_offset_lockless(p4dp, p4d, addr); do { - pud_t pud =3D READ_ONCE(*pudp); + pud_t pud =3D pudp_get(pudp); =20 next =3D pud_addr_end(addr, end); if (unlikely(!pud_present(pud))) @@ -3106,7 +3106,7 @@ static int gup_fast_p4d_range(pgd_t *pgdp, pgd_t pgd,= unsigned long addr, =20 p4dp =3D p4d_offset_lockless(pgdp, pgd, addr); do { - p4d_t p4d =3D READ_ONCE(*p4dp); + p4d_t p4d =3D p4dp_get(p4dp); =20 next =3D p4d_addr_end(addr, end); if (!p4d_present(p4d)) @@ -3128,7 +3128,7 @@ static void gup_fast_pgd_range(unsigned long addr, un= signed long end, =20 pgdp =3D pgd_offset(current->mm, addr); do { - pgd_t pgd =3D READ_ONCE(*pgdp); + pgd_t pgd =3D pgdp_get(pgdp); =20 next =3D pgd_addr_end(addr, end); if (pgd_none(pgd)) diff --git a/mm/hmm.c b/mm/hmm.c index d545e2494994..126c3f42e525 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -431,7 +431,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long = start, unsigned long end, /* Normally we don't want to split the huge page */ walk->action =3D ACTION_CONTINUE; =20 - pud =3D READ_ONCE(*pudp); + pud =3D pudp_get(pudp); if (!pud_present(pud)) { spin_unlock(ptl); return hmm_vma_walk_hole(start, end, -1, walk); diff --git a/mm/memory.c b/mm/memory.c index 0ba4f6b71847..50f841ee6e84 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -6549,12 +6549,12 @@ int follow_pfnmap_start(struct follow_pfnmap_args *= args) goto out; =20 p4dp =3D p4d_offset(pgdp, address); - p4d =3D READ_ONCE(*p4dp); + p4d =3D p4dp_get(p4dp); if (p4d_none(p4d) || unlikely(p4d_bad(p4d))) goto out; =20 pudp =3D pud_offset(p4dp, address); - pud =3D READ_ONCE(*pudp); + pud =3D pudp_get(pudp); if (pud_none(pud)) goto out; if (pud_leaf(pud)) { diff --git a/mm/mprotect.c b/mm/mprotect.c index 113b48985834..988c366137d5 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -599,7 +599,7 @@ static inline long change_pud_range(struct mmu_gather *= tlb, break; } =20 - pud =3D READ_ONCE(*pudp); + pud =3D pudp_get(pudp); if (pud_none(pud)) continue; =20 diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c index dbd8daccade2..37522d6cb398 100644 --- a/mm/sparse-vmemmap.c +++ b/mm/sparse-vmemmap.c @@ -439,7 +439,7 @@ int __meminit vmemmap_populate_hugepages(unsigned long = start, unsigned long end, return -ENOMEM; =20 pmd =3D pmd_offset(pud, addr); - if (pmd_none(READ_ONCE(*pmd))) { + if (pmd_none(pmdp_get(pmd))) { void *p; =20 p =3D vmemmap_alloc_block_buf(PMD_SIZE, node, altmap); diff --git a/mm/vmscan.c b/mm/vmscan.c index 674999999cd0..14c2722b955b 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3772,7 +3772,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long s= tart, unsigned long end, pud =3D pud_offset(p4d, start & P4D_MASK); restart: for (i =3D pud_index(start), addr =3D start; addr !=3D end; i++, addr =3D= next) { - pud_t val =3D READ_ONCE(pud[i]); + pud_t val =3D pudp_get(pud + i); =20 next =3D pud_addr_end(addr, end); =20 --=20 2.30.2