From nobody Fri Apr 10 17:05:36 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9237C32774 for ; Mon, 22 Aug 2022 13:39:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235235AbiHVNjP convert rfc822-to-8bit (ORCPT ); Mon, 22 Aug 2022 09:39:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51912 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234875AbiHVNjL (ORCPT ); Mon, 22 Aug 2022 09:39:11 -0400 Received: from mx1.emlix.com (mx1.emlix.com [136.243.223.33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1E357B4B6 for ; Mon, 22 Aug 2022 06:39:09 -0700 (PDT) Received: from mailer.emlix.com (p5098be52.dip0.t-ipconnect.de [80.152.190.82]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.emlix.com (Postfix) with ESMTPS id CA8BC60256; Mon, 22 Aug 2022 15:04:37 +0200 (CEST) From: Rolf Eike Beer To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/6] mm: pagewalk: make error checks more obvious Date: Mon, 22 Aug 2022 15:00:05 +0200 Message-ID: <2203731.iZASKD2KPV@devpool047> Organization: emlix GmbH In-Reply-To: <3200642.44csPzL39Z@devpool047> References: <3200642.44csPzL39Z@devpool047> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The err variable only needs to be checked when it was assigned directly before, it is not carried on to any later checks. Move the checks into the same "if" conditions where they are assigned. Also just return the error at the relevant places. While at it move these err variables to a more local scope at some places. Signed-off-by: Rolf Eike Beer --- mm/pagewalk.c | 140 +++++++++++++++++++++++++++----------------------- 1 file changed, 77 insertions(+), 63 deletions(-) diff --git a/mm/pagewalk.c b/mm/pagewalk.c index 9b3db11a4d1d..c67b2532db8f 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -24,25 +24,24 @@ static int walk_pte_range_inner(pte_t *pte, unsigned lo= ng addr, unsigned long end, struct mm_walk *walk) { const struct mm_walk_ops *ops =3D walk->ops; - int err =3D 0; =20 for (;;) { - err =3D ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk); + int err =3D ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk); if (err) - break; + return err; if (addr >=3D end - PAGE_SIZE) break; addr +=3D PAGE_SIZE; pte++; } - return err; + return 0; } =20 static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long en= d, struct mm_walk *walk) { pte_t *pte; - int err =3D 0; + int err; spinlock_t *ptl; =20 if (walk->no_vma) { @@ -62,7 +61,6 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr,= unsigned long end, static int walk_hugepd_range(hugepd_t *phpd, unsigned long addr, unsigned long end, struct mm_walk *walk, int pdshift) { - int err =3D 0; const struct mm_walk_ops *ops =3D walk->ops; int shift =3D hugepd_shift(*phpd); int page_size =3D 1 << shift; @@ -75,6 +73,7 @@ static int walk_hugepd_range(hugepd_t *phpd, unsigned lon= g addr, =20 for (;;) { pte_t *pte; + int err; =20 spin_lock(&walk->mm->page_table_lock); pte =3D hugepte_offset(*phpd, addr, pdshift); @@ -82,12 +81,12 @@ static int walk_hugepd_range(hugepd_t *phpd, unsigned l= ong addr, spin_unlock(&walk->mm->page_table_lock); =20 if (err) - break; + return err; if (addr >=3D end - page_size) break; addr +=3D page_size; } - return err; + return 0; } #else static int walk_hugepd_range(hugepd_t *phpd, unsigned long addr, @@ -103,18 +102,20 @@ static int walk_pmd_range(pud_t *pud, unsigned long a= ddr, unsigned long end, pmd_t *pmd; unsigned long next; const struct mm_walk_ops *ops =3D walk->ops; - int err =3D 0; int depth =3D real_depth(3); =20 pmd =3D pmd_offset(pud, addr); do { -again: + int err; + + again: next =3D pmd_addr_end(addr, end); if (pmd_none(*pmd) || (!walk->vma && !walk->no_vma)) { - if (ops->pte_hole) + if (ops->pte_hole) { err =3D ops->pte_hole(addr, next, depth, walk); - if (err) - break; + if (err) + return err; + } continue; } =20 @@ -124,10 +125,11 @@ static int walk_pmd_range(pud_t *pud, unsigned long a= ddr, unsigned long end, * This implies that each ->pmd_entry() handler * needs to know about pmd_trans_huge() pmds */ - if (ops->pmd_entry) + if (ops->pmd_entry) { err =3D ops->pmd_entry(pmd, addr, next, walk); - if (err) - break; + if (err) + return err; + } =20 if (walk->action =3D=3D ACTION_AGAIN) goto again; @@ -152,10 +154,10 @@ static int walk_pmd_range(pud_t *pud, unsigned long a= ddr, unsigned long end, else err =3D walk_pte_range(pmd, addr, next, walk); if (err) - break; + return err; } while (pmd++, addr =3D next, addr !=3D end); =20 - return err; + return 0; } =20 static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long en= d, @@ -164,27 +166,30 @@ static int walk_pud_range(p4d_t *p4d, unsigned long a= ddr, unsigned long end, pud_t *pud; unsigned long next; const struct mm_walk_ops *ops =3D walk->ops; - int err =3D 0; int depth =3D real_depth(2); =20 pud =3D pud_offset(p4d, addr); do { + int err; + again: next =3D pud_addr_end(addr, end); if (pud_none(*pud) || (!walk->vma && !walk->no_vma)) { - if (ops->pte_hole) + if (ops->pte_hole) { err =3D ops->pte_hole(addr, next, depth, walk); - if (err) - break; + if (err) + return err; + } continue; } =20 walk->action =3D ACTION_SUBTREE; =20 - if (ops->pud_entry) + if (ops->pud_entry) { err =3D ops->pud_entry(pud, addr, next, walk); - if (err) - break; + if (err) + return err; + } =20 if (walk->action =3D=3D ACTION_AGAIN) goto again; @@ -204,10 +209,10 @@ static int walk_pud_range(p4d_t *p4d, unsigned long a= ddr, unsigned long end, else err =3D walk_pmd_range(pud, addr, next, walk); if (err) - break; + return err; } while (pud++, addr =3D next, addr !=3D end); =20 - return err; + return 0; } =20 static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long en= d, @@ -216,33 +221,35 @@ static int walk_p4d_range(pgd_t *pgd, unsigned long a= ddr, unsigned long end, p4d_t *p4d; unsigned long next; const struct mm_walk_ops *ops =3D walk->ops; - int err =3D 0; int depth =3D real_depth(1); =20 p4d =3D p4d_offset(pgd, addr); do { + int err; + next =3D p4d_addr_end(addr, end); if (p4d_none_or_clear_bad(p4d)) { - if (ops->pte_hole) + if (ops->pte_hole) { err =3D ops->pte_hole(addr, next, depth, walk); - if (err) - break; + if (err) + return err; + } continue; } if (ops->p4d_entry) { err =3D ops->p4d_entry(p4d, addr, next, walk); if (err) - break; + return err; } if (is_hugepd(__hugepd(p4d_val(*p4d)))) err =3D walk_hugepd_range((hugepd_t *)p4d, addr, next, walk, P4D_SHIFT); else if (ops->pud_entry || ops->pmd_entry || ops->pte_entry) err =3D walk_pud_range(p4d, addr, next, walk); if (err) - break; + return err; } while (p4d++, addr =3D next, addr !=3D end); =20 - return err; + return 0; } =20 static int walk_pgd_range(unsigned long addr, unsigned long end, @@ -251,35 +258,37 @@ static int walk_pgd_range(unsigned long addr, unsigne= d long end, pgd_t *pgd; unsigned long next; const struct mm_walk_ops *ops =3D walk->ops; - int err =3D 0; =20 if (walk->pgd) pgd =3D walk->pgd + pgd_index(addr); else pgd =3D pgd_offset(walk->mm, addr); do { + int err; + next =3D pgd_addr_end(addr, end); if (pgd_none_or_clear_bad(pgd)) { - if (ops->pte_hole) + if (ops->pte_hole) { err =3D ops->pte_hole(addr, next, 0, walk); - if (err) - break; + if (err) + return err; + } continue; } if (ops->pgd_entry) { err =3D ops->pgd_entry(pgd, addr, next, walk); if (err) - break; + return err; } if (is_hugepd(__hugepd(pgd_val(*pgd)))) err =3D walk_hugepd_range((hugepd_t *)pgd, addr, next, walk, PGDIR_SHIF= T); else if (ops->p4d_entry || ops->pud_entry || ops->pmd_entry || ops->pte_= entry) err =3D walk_p4d_range(pgd, addr, next, walk); if (err) - break; + return err; } while (pgd++, addr =3D next, addr !=3D end); =20 - return err; + return 0; } =20 #ifdef CONFIG_HUGETLB_PAGE @@ -300,9 +309,10 @@ static int walk_hugetlb_range(unsigned long addr, unsi= gned long end, unsigned long sz =3D huge_page_size(h); pte_t *pte; const struct mm_walk_ops *ops =3D walk->ops; - int err =3D 0; =20 do { + int err; + next =3D hugetlb_entry_end(h, addr, end); pte =3D huge_pte_offset(walk->mm, addr & hmask, sz); =20 @@ -312,10 +322,10 @@ static int walk_hugetlb_range(unsigned long addr, uns= igned long end, err =3D ops->pte_hole(addr, next, -1, walk); =20 if (err) - break; + return err; } while (addr =3D next, addr !=3D end); =20 - return err; + return 0; } =20 #else /* CONFIG_HUGETLB_PAGE */ @@ -351,10 +361,13 @@ static int walk_page_test(unsigned long start, unsign= ed long end, * vma(VM_PFNMAP). */ if (vma->vm_flags & VM_PFNMAP) { - int err =3D 1; - if (ops->pte_hole) - err =3D ops->pte_hole(start, end, -1, walk); - return err ? err : 1; + if (ops->pte_hole) { + int err =3D ops->pte_hole(start, end, -1, walk); + + return err ? err : 1; + } + + return 1; } return 0; } @@ -428,7 +441,6 @@ int walk_page_range(struct mm_struct *mm, unsigned long= start, unsigned long end, const struct mm_walk_ops *ops, void *private) { - int err =3D 0; unsigned long next; struct vm_area_struct *vma; struct mm_walk walk =3D { @@ -447,6 +459,8 @@ int walk_page_range(struct mm_struct *mm, unsigned long= start, =20 vma =3D find_vma(walk.mm, start); do { + int err; + if (!vma) { /* after the last vma */ walk.vma =3D NULL; next =3D end; @@ -465,18 +479,18 @@ int walk_page_range(struct mm_struct *mm, unsigned lo= ng start, * controlling the pagewalk, so should never * be passed to the callers. */ - err =3D 0; continue; } if (err < 0) - break; + return err; } - if (walk.vma || walk.ops->pte_hole) + if (walk.vma || walk.ops->pte_hole) { err =3D __walk_page_range(start, next, &walk); - if (err) - break; + if (err) + return err; + } } while (start =3D next, start < end); - return err; + return 0; } =20 /* @@ -571,11 +585,12 @@ int walk_page_mapping(struct address_space *mapping, = pgoff_t first_index, struct vm_area_struct *vma; pgoff_t vba, vea, cba, cea; unsigned long start_addr, end_addr; - int err =3D 0; =20 lockdep_assert_held(&mapping->i_mmap_rwsem); vma_interval_tree_foreach(vma, &mapping->i_mmap, first_index, first_index + nr - 1) { + int err; + /* Clip to the vma */ vba =3D vma->vm_pgoff; vea =3D vba + vma_pages(vma); @@ -593,16 +608,15 @@ int walk_page_mapping(struct address_space *mapping, = pgoff_t first_index, walk.mm =3D vma->vm_mm; =20 err =3D walk_page_test(vma->vm_start, vma->vm_end, &walk); - if (err > 0) { - err =3D 0; - break; - } else if (err < 0) - break; + if (err > 0) + return 0; + else if (err < 0) + return err; =20 err =3D __walk_page_range(start_addr, end_addr, &walk); if (err) - break; + return err; } =20 - return err; + return 0; } --=20 2.37.2 --=20 Rolf Eike Beer, emlix GmbH, http://www.emlix.com Fon +49 551 30664-0, Fax +49 551 30664-11 Gothaer Platz 3, 37083 G=C3=B6ttingen, Germany Sitz der Gesellschaft: G=C3=B6ttingen, Amtsgericht G=C3=B6ttingen HR B 3160 Gesch=C3=A4ftsf=C3=BChrung: Heike Jordan, Dr. Uwe Kracke =E2=80=93 Ust-IdNr= .: DE 205 198 055 emlix - smart embedded open source