From nobody Wed Jan 7 03:30:56 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 10C55E784B6 for ; Mon, 2 Oct 2023 14:30:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237796AbjJBOaz (ORCPT ); Mon, 2 Oct 2023 10:30:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37390 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237779AbjJBOaq (ORCPT ); Mon, 2 Oct 2023 10:30:46 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 382BCB0 for ; Mon, 2 Oct 2023 07:30:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1696257002; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Tnnd1i96YoBpg2Wk1+SUJX4WepSITGLgtW2LVCbh8ow=; b=gdxffqR5WYhgRxe/ZADdLcraC3CbWZeOZUdt8MfBQM7Gd+1makCMtW+CtEKPY3yxgK3iXc RpxEaNA7Q0G0Gqxmz8v455aPxEJlexwNM2v3giSWL4GiS6hj2fM1Zuamd1k3OQ7yjX4OD7 1FMN2ToaymwixrqypLYGjPphpvIcY/U= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-596-SD06yepTPyaOIWqDKjRAKw-1; Mon, 02 Oct 2023 10:29:56 -0400 X-MC-Unique: SD06yepTPyaOIWqDKjRAKw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 805873826D2C; Mon, 2 Oct 2023 14:29:55 +0000 (UTC) Received: from t14s.fritz.box (unknown [10.39.194.19]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5F47B1005B90; Mon, 2 Oct 2023 14:29:54 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, David Hildenbrand , Andrew Morton , Mike Kravetz , Muchun Song , Suren Baghdasaryan Subject: [PATCH v1 3/3] memory: move exclusivity detection in do_wp_page() into wp_can_reuse_anon_folio() Date: Mon, 2 Oct 2023 16:29:49 +0200 Message-ID: <20231002142949.235104-4-david@redhat.com> In-Reply-To: <20231002142949.235104-1-david@redhat.com> References: <20231002142949.235104-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Let's clean up do_wp_page() a bit, removing two labels and making it a easier to read. wp_can_reuse_anon_folio() now only operates on the whole folio. Move the SetPageAnonExclusive() out into do_wp_page(). No need to do this under page lock -- the page table lock is sufficient. Signed-off-by: David Hildenbrand --- mm/memory.c | 88 +++++++++++++++++++++++++++-------------------------- 1 file changed, 45 insertions(+), 43 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 1f0e3317cbdd..512f6f05620e 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3358,6 +3358,44 @@ static vm_fault_t wp_page_shared(struct vm_fault *vm= f, struct folio *folio) return ret; } =20 +static bool wp_can_reuse_anon_folio(struct folio *folio, + struct vm_area_struct *vma) +{ + /* + * We have to verify under folio lock: these early checks are + * just an optimization to avoid locking the folio and freeing + * the swapcache if there is little hope that we can reuse. + * + * KSM doesn't necessarily raise the folio refcount. + */ + if (folio_test_ksm(folio) || folio_ref_count(folio) > 3) + return false; + if (!folio_test_lru(folio)) + /* + * We cannot easily detect+handle references from + * remote LRU caches or references to LRU folios. + */ + lru_add_drain(); + if (folio_ref_count(folio) > 1 + folio_test_swapcache(folio)) + return false; + if (!folio_trylock(folio)) + return false; + if (folio_test_swapcache(folio)) + folio_free_swap(folio); + if (folio_test_ksm(folio) || folio_ref_count(folio) !=3D 1) { + folio_unlock(folio); + return false; + } + /* + * Ok, we've got the only folio reference from our mapping + * and the folio is locked, it's dark out, and we're wearing + * sunglasses. Hit it. + */ + folio_move_anon_rmap(folio, vma); + folio_unlock(folio); + return true; +} + /* * This routine handles present pages, when * * users try to write to a shared page (FAULT_FLAG_WRITE) @@ -3444,49 +3482,14 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) /* * Private mapping: create an exclusive anonymous page copy if reuse * is impossible. We might miss VM_WRITE for FOLL_FORCE handling. + * + * If we encounter a page that is marked exclusive, we must reuse + * the page without further checks. */ - if (folio && folio_test_anon(folio)) { - /* - * If the page is exclusive to this process we must reuse the - * page without further checks. - */ - if (PageAnonExclusive(vmf->page)) - goto reuse; - - /* - * We have to verify under folio lock: these early checks are - * just an optimization to avoid locking the folio and freeing - * the swapcache if there is little hope that we can reuse. - * - * KSM doesn't necessarily raise the folio refcount. - */ - if (folio_test_ksm(folio) || folio_ref_count(folio) > 3) - goto copy; - if (!folio_test_lru(folio)) - /* - * We cannot easily detect+handle references from - * remote LRU caches or references to LRU folios. - */ - lru_add_drain(); - if (folio_ref_count(folio) > 1 + folio_test_swapcache(folio)) - goto copy; - if (!folio_trylock(folio)) - goto copy; - if (folio_test_swapcache(folio)) - folio_free_swap(folio); - if (folio_test_ksm(folio) || folio_ref_count(folio) !=3D 1) { - folio_unlock(folio); - goto copy; - } - /* - * Ok, we've got the only folio reference from our mapping - * and the folio is locked, it's dark out, and we're wearing - * sunglasses. Hit it. - */ - folio_move_anon_rmap(folio, vma); - SetPageAnonExclusive(vmf->page); - folio_unlock(folio); -reuse: + if (folio && folio_test_anon(folio) && + (PageAnonExclusive(vmf->page) || wp_can_reuse_anon_folio(folio, vma))= ) { + if (!PageAnonExclusive(vmf->page)) + SetPageAnonExclusive(vmf->page); if (unlikely(unshare)) { pte_unmap_unlock(vmf->pte, vmf->ptl); return 0; @@ -3494,7 +3497,6 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) wp_page_reuse(vmf); return 0; } -copy: /* * Ok, we need to copy. Oh, well.. */ --=20 2.41.0