From nobody Mon Feb 9 13:37:01 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 D31E6EB64D7 for ; Mon, 26 Jun 2023 17:15:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230070AbjFZRPm (ORCPT ); Mon, 26 Jun 2023 13:15:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51288 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231343AbjFZRPC (ORCPT ); Mon, 26 Jun 2023 13:15:02 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id B03FF10EF; Mon, 26 Jun 2023 10:14:56 -0700 (PDT) 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 864C1150C; Mon, 26 Jun 2023 10:15:40 -0700 (PDT) Received: from e125769.cambridge.arm.com (e125769.cambridge.arm.com [10.1.196.26]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 9D3913F663; Mon, 26 Jun 2023 10:14:53 -0700 (PDT) From: Ryan Roberts To: Andrew Morton , "Matthew Wilcox (Oracle)" , "Kirill A. Shutemov" , Yin Fengwei , David Hildenbrand , Yu Zhao , Catalin Marinas , Will Deacon , Geert Uytterhoeven , Christian Borntraeger , Sven Schnelle , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" Cc: Ryan Roberts , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-s390@vger.kernel.org Subject: [PATCH v1 05/10] mm: Implement folio_remove_rmap_range() Date: Mon, 26 Jun 2023 18:14:25 +0100 Message-Id: <20230626171430.3167004-6-ryan.roberts@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230626171430.3167004-1-ryan.roberts@arm.com> References: <20230626171430.3167004-1-ryan.roberts@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Like page_remove_rmap() but batch-removes the rmap for a range of pages belonging to a folio, for effciency savings. All pages are accounted as small pages. Signed-off-by: Ryan Roberts --- include/linux/rmap.h | 2 ++ mm/rmap.c | 62 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 64 insertions(+) diff --git a/include/linux/rmap.h b/include/linux/rmap.h index 15433a3d0cbf..50f50e4cb0f8 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -204,6 +204,8 @@ void folio_add_file_rmap_range(struct folio *, struct p= age *, unsigned int nr, struct vm_area_struct *, bool compound); void page_remove_rmap(struct page *, struct vm_area_struct *, bool compound); +void folio_remove_rmap_range(struct folio *folio, struct page *page, + int nr, struct vm_area_struct *vma); =20 void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long address, rmap_t flags); diff --git a/mm/rmap.c b/mm/rmap.c index 4050bcea7ae7..ac1d93d43f2b 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1434,6 +1434,68 @@ void page_add_file_rmap(struct page *page, struct vm= _area_struct *vma, folio_add_file_rmap_range(folio, page, nr_pages, vma, compound); } =20 +/* + * folio_remove_rmap_range - take down pte mappings from a range of pages + * belonging to a folio. All pages are accounted as small pages. + * @folio: folio that all pages belong to + * @page: first page in range to remove mapping from + * @nr: number of pages in range to remove mapping from + * @vma: the vm area from which the mapping is removed + * + * The caller needs to hold the pte lock. + */ +void folio_remove_rmap_range(struct folio *folio, struct page *page, + int nr, struct vm_area_struct *vma) +{ + atomic_t *mapped =3D &folio->_nr_pages_mapped; + int nr_unmapped =3D 0; + int nr_mapped; + bool last; + enum node_stat_item idx; + + VM_BUG_ON_FOLIO(folio_test_hugetlb(folio), folio); + + if (!folio_test_large(folio)) { + /* Is this the page's last map to be removed? */ + last =3D atomic_add_negative(-1, &page->_mapcount); + nr_unmapped =3D last; + } else { + for (; nr !=3D 0; nr--, page++) { + /* Is this the page's last map to be removed? */ + last =3D atomic_add_negative(-1, &page->_mapcount); + if (last) { + /* Page still mapped if folio mapped entirely */ + nr_mapped =3D atomic_dec_return_relaxed(mapped); + if (nr_mapped < COMPOUND_MAPPED) + nr_unmapped++; + } + } + } + + if (nr_unmapped) { + idx =3D folio_test_anon(folio) ? NR_ANON_MAPPED : NR_FILE_MAPPED; + __lruvec_stat_mod_folio(folio, idx, -nr_unmapped); + + /* + * Queue anon THP for deferred split if we have just unmapped at + * least 1 page, while at least 1 page remains mapped. + */ + if (folio_test_large(folio) && folio_test_anon(folio)) + if (nr_mapped) + deferred_split_folio(folio); + } + + /* + * It would be tidy to reset folio_test_anon mapping when fully + * unmapped, but that might overwrite a racing page_add_anon_rmap + * which increments mapcount after us but sets mapping before us: + * so leave the reset to free_pages_prepare, and remember that + * it's only reliable while mapped. + */ + + munlock_vma_folio(folio, vma, false); +} + /** * page_remove_rmap - take down pte mapping from a page * @page: page to remove mapping from --=20 2.25.1