From nobody Thu Feb 12 12:32:17 2026 Received: from mail-oa1-f47.google.com (mail-oa1-f47.google.com [209.85.160.47]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 10A441411F4 for ; Thu, 13 Jun 2024 08:39:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.160.47 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718267962; cv=none; b=r0KWyaq2B9gcBwBk+V/K3+O9+a6Y34GYZF/yvL0P+puRUjTWXSKtqtksLyKcCxt7i+6pfbkR54cuceVdswGMFn6q/QxKhkLOPk9xPUEUU5GB7qMGEowb20j4rYnhCHOoT/+r1U0oeeftVaJH9VXByYlBBW9TrptJRCTDEsZFnII= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718267962; c=relaxed/simple; bh=Ies1FaPAxygACj79wFDDkxn5MYHI5m4VB59yj4jorvs=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=lHh27aLgmfvtduP0Q1fcV2EC02jjN8uRwhK0jc3aVgQFDGFiR+2rrXwBg8hlnP4ouUOfScuTM7ekEfOlEDRzbwSMglZBCAVgXOq9JCiwCBJA4PO2/FycS2v0hy/8pgoyD3jAJA41pJecwjgclsetrm/7vzX55TagL53ivwZprGU= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com; spf=pass smtp.mailfrom=bytedance.com; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b=QjzNFv81; arc=none smtp.client-ip=209.85.160.47 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bytedance.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b="QjzNFv81" Received: by mail-oa1-f47.google.com with SMTP id 586e51a60fabf-24c5ec50da1so132973fac.3 for ; Thu, 13 Jun 2024 01:39:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; t=1718267959; x=1718872759; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=ChynU9z5JOCMqbjVxFHZ6Asc4dZFXj2+q+uZdr+9n9E=; b=QjzNFv81TGb5zvA8Trxlh6PDmFGBHrboPDVzpKVwokmJC+4cXbv4NosTevGHmN5wei KiPJ3cle0f6pDcYIeDbGX8vu9H/xdONb7z4VQkmIMeTCxf765BKl1DcZOIMLXL7oUerd vuAKPWYZJZckbIadKywbNXZN3m7b67j3NAPO7Zk6nIoQE3L/oEfAGU14f3QJwVWdwNuL kDiU/oZLd0UZVsh4KfcIz1dV9wbdAdYW3QRLQrr6SUe4Bx1rcUw10BUGbC28W0ArE1NK 53pbWQ7uyQS+hYycFg9RAwLQgN4buWVOqj7Ur35PErVr0Ix7yhOQoMsmDQD5P7LRPo0u 3dNQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1718267959; x=1718872759; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=ChynU9z5JOCMqbjVxFHZ6Asc4dZFXj2+q+uZdr+9n9E=; b=xBHLD7xioDm6Stpj+XBzXFz6AR31+eahRx3S5GykWaYudZC9/WT7HKCOuZnAviT+dB ruA0dBW8ZUDe77YfdAriwhGufNLr2c3EJo9bb7zXac6lUaIXXiZhsJ++VPWq0UL5gQ01 aHuGeSTopxHZRQU/6Ikrjs01ta46B2WpMjYaIedCAk44Z1SJPGuoaCOvIUpOx/Vz4bUS ESx3ya5dzm0AWQvjXBToFguqvcud45qYG12BTsnWGkMr8ya4+L0E0wV2ak4nG/O8VQbh SsZ8AxOtKBEkylK5RBOefYKwqbaKE4Y3JhJWowe4eQ14PaccJ3SrMLV0gllSoVbwcIcb yaeg== X-Forwarded-Encrypted: i=1; AJvYcCX2Zsl24dTX407lkDfaiLA+z4OLH3pHulsfXKfdsctP/0PSUokq83cfWFaSNPUmyGnulMQLxeqxlH6VVQQ=@vger.kernel.org X-Gm-Message-State: AOJu0Yxlp48gH+sqWOFgEPwcC8Oe6AECCkfWVTQUCJiU2lboX7X5sKr4 oqdztS0QpxUAGdSYyWo090KIh5uxm3xBToGEb3eQI3BePXlrCEoYqQ4mOiLwT0U= X-Google-Smtp-Source: AGHT+IG5fRqFeCgKiHECkAvdVDXYqyUQDwS7LLbxLF7n/kGnf0XhUcBBmoT8lkZTDQg4z6Muj8MdhA== X-Received: by 2002:a05:6870:7193:b0:254:a5dd:3772 with SMTP id 586e51a60fabf-25514ef5f91mr4375320fac.4.1718267958799; Thu, 13 Jun 2024 01:39:18 -0700 (PDT) Received: from C02DW0BEMD6R.bytedance.net ([203.208.167.150]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-705ccb980bdsm820856b3a.211.2024.06.13.01.39.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Jun 2024 01:39:18 -0700 (PDT) From: Qi Zheng To: david@redhat.com, hughd@google.com, willy@infradead.org, mgorman@suse.de, muchun.song@linux.dev, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qi Zheng Subject: [RFC PATCH 2/3] mm: pgtable: make pte_offset_map_nolock() return pmdval Date: Thu, 13 Jun 2024 16:38:09 +0800 Message-Id: X-Mailer: git-send-email 2.24.3 (Apple Git-128) In-Reply-To: References: 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" Make pte_offset_map_nolock() return pmdval so that we can recheck the *pmd once the lock is taken. This is a preparation for freeing empty PTE pages, no functional changes are expected. Signed-off-by: Qi Zheng --- Documentation/mm/split_page_table_lock.rst | 3 ++- arch/arm/mm/fault-armv.c | 2 +- arch/powerpc/mm/pgtable.c | 2 +- include/linux/mm.h | 4 ++-- mm/filemap.c | 2 +- mm/khugepaged.c | 4 ++-- mm/memory.c | 4 ++-- mm/mremap.c | 2 +- mm/page_vma_mapped.c | 2 +- mm/pgtable-generic.c | 21 ++++++++++++--------- mm/userfaultfd.c | 4 ++-- mm/vmscan.c | 2 +- 12 files changed, 28 insertions(+), 24 deletions(-) diff --git a/Documentation/mm/split_page_table_lock.rst b/Documentation/mm/= split_page_table_lock.rst index e4f6972eb6c0..e6a47d57531c 100644 --- a/Documentation/mm/split_page_table_lock.rst +++ b/Documentation/mm/split_page_table_lock.rst @@ -18,7 +18,8 @@ There are helpers to lock/unlock a table and other access= or functions: pointer to its PTE table lock, or returns NULL if no PTE table; - pte_offset_map_nolock() maps PTE, returns pointer to PTE with pointer to its PTE table - lock (not taken), or returns NULL if no PTE table; + lock (not taken) and the value of its pmd entry, or returns NULL + if no PTE table; - pte_offset_map() maps PTE, returns pointer to PTE, or returns NULL if no PTE table; - pte_unmap() diff --git a/arch/arm/mm/fault-armv.c b/arch/arm/mm/fault-armv.c index 2286c2ea60ec..3e4ed99b9330 100644 --- a/arch/arm/mm/fault-armv.c +++ b/arch/arm/mm/fault-armv.c @@ -117,7 +117,7 @@ static int adjust_pte(struct vm_area_struct *vma, unsig= ned long address, * must use the nested version. This also means we need to * open-code the spin-locking. */ - pte =3D pte_offset_map_nolock(vma->vm_mm, pmd, address, &ptl); + pte =3D pte_offset_map_nolock(vma->vm_mm, pmd, NULL, address, &ptl); if (!pte) return 0; =20 diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c index 9e7ba9c3851f..ab0250f1b226 100644 --- a/arch/powerpc/mm/pgtable.c +++ b/arch/powerpc/mm/pgtable.c @@ -350,7 +350,7 @@ void assert_pte_locked(struct mm_struct *mm, unsigned l= ong addr) */ if (pmd_none(*pmd)) return; - pte =3D pte_offset_map_nolock(mm, pmd, addr, &ptl); + pte =3D pte_offset_map_nolock(mm, pmd, NULL, addr, &ptl); BUG_ON(!pte); assert_spin_locked(ptl); pte_unmap(pte); diff --git a/include/linux/mm.h b/include/linux/mm.h index 106bb0310352..d5550c3dc550 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2969,8 +2969,8 @@ static inline pte_t *pte_offset_map_lock(struct mm_st= ruct *mm, pmd_t *pmd, return pte; } =20 -pte_t *pte_offset_map_nolock(struct mm_struct *mm, pmd_t *pmd, - unsigned long addr, spinlock_t **ptlp); +pte_t *pte_offset_map_nolock(struct mm_struct *mm, pmd_t *pmd, pmd_t *pmdv= alp, + unsigned long addr, spinlock_t **ptlp); =20 #define pte_unmap_unlock(pte, ptl) do { \ spin_unlock(ptl); \ diff --git a/mm/filemap.c b/mm/filemap.c index 37061aafd191..7eb2e3599966 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3231,7 +3231,7 @@ static vm_fault_t filemap_fault_recheck_pte_none(stru= ct vm_fault *vmf) if (!(vmf->flags & FAULT_FLAG_ORIG_PTE_VALID)) return 0; =20 - ptep =3D pte_offset_map_nolock(vma->vm_mm, vmf->pmd, vmf->address, + ptep =3D pte_offset_map_nolock(vma->vm_mm, vmf->pmd, NULL, vmf->address, &vmf->ptl); if (unlikely(!ptep)) return VM_FAULT_NOPAGE; diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 774a97e6e2da..2a8703ee876c 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -992,7 +992,7 @@ static int __collapse_huge_page_swapin(struct mm_struct= *mm, }; =20 if (!pte++) { - pte =3D pte_offset_map_nolock(mm, pmd, address, &ptl); + pte =3D pte_offset_map_nolock(mm, pmd, NULL, address, &ptl); if (!pte) { mmap_read_unlock(mm); result =3D SCAN_PMD_NULL; @@ -1581,7 +1581,7 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, uns= igned long addr, if (userfaultfd_armed(vma) && !(vma->vm_flags & VM_SHARED)) pml =3D pmd_lock(mm, pmd); =20 - start_pte =3D pte_offset_map_nolock(mm, pmd, haddr, &ptl); + start_pte =3D pte_offset_map_nolock(mm, pmd, NULL, haddr, &ptl); if (!start_pte) /* mmap_lock + page lock should prevent this */ goto abort; if (!pml) diff --git a/mm/memory.c b/mm/memory.c index 1bd2ffb76ec2..694c0989a1d8 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1108,7 +1108,7 @@ copy_pte_range(struct vm_area_struct *dst_vma, struct= vm_area_struct *src_vma, ret =3D -ENOMEM; goto out; } - src_pte =3D pte_offset_map_nolock(src_mm, src_pmd, addr, &src_ptl); + src_pte =3D pte_offset_map_nolock(src_mm, src_pmd, NULL, addr, &src_ptl); if (!src_pte) { pte_unmap_unlock(dst_pte, dst_ptl); /* ret =3D=3D 0 */ @@ -5486,7 +5486,7 @@ static vm_fault_t handle_pte_fault(struct vm_fault *v= mf) * it into a huge pmd: just retry later if so. */ vmf->pte =3D pte_offset_map_nolock(vmf->vma->vm_mm, vmf->pmd, - vmf->address, &vmf->ptl); + NULL, vmf->address, &vmf->ptl); if (unlikely(!vmf->pte)) return 0; vmf->orig_pte =3D ptep_get_lockless(vmf->pte); diff --git a/mm/mremap.c b/mm/mremap.c index e7ae140fc640..f672d0218a6f 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -175,7 +175,7 @@ static int move_ptes(struct vm_area_struct *vma, pmd_t = *old_pmd, err =3D -EAGAIN; goto out; } - new_pte =3D pte_offset_map_nolock(mm, new_pmd, new_addr, &new_ptl); + new_pte =3D pte_offset_map_nolock(mm, new_pmd, NULL, new_addr, &new_ptl); if (!new_pte) { pte_unmap_unlock(old_pte, old_ptl); err =3D -EAGAIN; diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c index ae5cc42aa208..507701b7bcc1 100644 --- a/mm/page_vma_mapped.c +++ b/mm/page_vma_mapped.c @@ -33,7 +33,7 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw, sp= inlock_t **ptlp) * Though, in most cases, page lock already protects this. */ pvmw->pte =3D pte_offset_map_nolock(pvmw->vma->vm_mm, pvmw->pmd, - pvmw->address, ptlp); + NULL, pvmw->address, ptlp); if (!pvmw->pte) return false; =20 diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c index 197937495a0a..b8b28715cb4f 100644 --- a/mm/pgtable-generic.c +++ b/mm/pgtable-generic.c @@ -305,7 +305,7 @@ pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr,= pmd_t *pmdvalp) return NULL; } =20 -pte_t *pte_offset_map_nolock(struct mm_struct *mm, pmd_t *pmd, +pte_t *pte_offset_map_nolock(struct mm_struct *mm, pmd_t *pmd, pmd_t *pmdv= alp, unsigned long addr, spinlock_t **ptlp) { pmd_t pmdval; @@ -314,6 +314,8 @@ pte_t *pte_offset_map_nolock(struct mm_struct *mm, pmd_= t *pmd, pte =3D __pte_offset_map(pmd, addr, &pmdval); if (likely(pte)) *ptlp =3D pte_lockptr(mm, &pmdval); + if (pmdvalp) + *pmdvalp =3D pmdval; return pte; } =20 @@ -347,14 +349,15 @@ pte_t *pte_offset_map_nolock(struct mm_struct *mm, pm= d_t *pmd, * and disconnected table. Until pte_unmap(pte) unmaps and rcu_read_unloc= k()s * afterwards. * - * pte_offset_map_nolock(mm, pmd, addr, ptlp), above, is like pte_offset_m= ap(); - * but when successful, it also outputs a pointer to the spinlock in ptlp = - as - * pte_offset_map_lock() does, but in this case without locking it. This = helps - * the caller to avoid a later pte_lockptr(mm, *pmd), which might by that = time - * act on a changed *pmd: pte_offset_map_nolock() provides the correct spi= nlock - * pointer for the page table that it returns. In principle, the caller s= hould - * recheck *pmd once the lock is taken; in practice, no callsite needs tha= t - - * either the mmap_lock for write, or pte_same() check on contents, is eno= ugh. + * pte_offset_map_nolock(mm, pmd, pmdvalp, addr, ptlp), above, is like + * pte_offset_map(); but when successful, it also outputs a pointer to the + * spinlock in ptlp - as pte_offset_map_lock() does, but in this case with= out + * locking it. This helps the caller to avoid a later pte_lockptr(mm, *pm= d), + * which might by that time act on a changed *pmd: pte_offset_map_nolock() + * provides the correct spinlock pointer for the page table that it return= s. + * In principle, the caller should recheck *pmd once the lock is taken; Bu= t in + * most cases, either the mmap_lock for write, or pte_same() check on cont= ents, + * is enough. * * Note that free_pgtables(), used after unmapping detached vmas, or when * exiting the whole mm, does not take page table lock before freeing a pa= ge diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 5e7f2801698a..9c77271d499c 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -1143,7 +1143,7 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t= *dst_pmd, pmd_t *src_pmd, src_addr, src_addr + PAGE_SIZE); mmu_notifier_invalidate_range_start(&range); retry: - dst_pte =3D pte_offset_map_nolock(mm, dst_pmd, dst_addr, &dst_ptl); + dst_pte =3D pte_offset_map_nolock(mm, dst_pmd, NULL, dst_addr, &dst_ptl); =20 /* Retry if a huge pmd materialized from under us */ if (unlikely(!dst_pte)) { @@ -1151,7 +1151,7 @@ static int move_pages_pte(struct mm_struct *mm, pmd_t= *dst_pmd, pmd_t *src_pmd, goto out; } =20 - src_pte =3D pte_offset_map_nolock(mm, src_pmd, src_addr, &src_ptl); + src_pte =3D pte_offset_map_nolock(mm, src_pmd, NULL, src_addr, &src_ptl); =20 /* * We held the mmap_lock for reading so MADV_DONTNEED diff --git a/mm/vmscan.c b/mm/vmscan.c index c0429fd6c573..56727caa907b 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3374,7 +3374,7 @@ static bool walk_pte_range(pmd_t *pmd, unsigned long = start, unsigned long end, DEFINE_MAX_SEQ(walk->lruvec); int old_gen, new_gen =3D lru_gen_from_seq(max_seq); =20 - pte =3D pte_offset_map_nolock(args->mm, pmd, start & PMD_MASK, &ptl); + pte =3D pte_offset_map_nolock(args->mm, pmd, NULL, start & PMD_MASK, &ptl= ); if (!pte) return false; if (!spin_trylock(ptl)) { --=20 2.20.1