From patchwork Mon Nov 7 16:17:27 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 13034729 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id F3C6EC43217 for ; Mon, 7 Nov 2022 16:21:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=2nMy4zMezVWhKOS9jdNQusOmTxsMsxV9dqAeE5xkXoE=; b=OusU8L32WuKB0M 7eXvYLoMrxL1lkZHv3bRnSCWk1dmopCAdlEw2tV7bPmgavqa1krIec9s6Owithx8xdDWNT9cmMEkJ iiVOgTvmlDeyNhq1QwxmANEB2jB5qwnoZYRQ5HjlYkxnW8OSSC3hImKsEucYyOlZglFoAj0KMBMDx mzew7wJOXR1tMpngGJKaBu7VUVQNbsWzFlPQVpRlrEz+HfbxZAJtZNm+V1UmDb8aUAmM3gJx0kPRk KcvlCSSISDqnN4WVPqA18XnER33NKuo0Me/3OZYc9B0eogC7L0njNMGcW2Uwv+OuwcMCMMB9DMkBI ZwYMBoDyPDlTr2PCxBPw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1os4rD-00G7bc-RR; Mon, 07 Nov 2022 16:20:20 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1os4pQ-00G6R6-4m for linux-arm-kernel@lists.infradead.org; Mon, 07 Nov 2022 16:18:29 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1667837907; 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=cVOAyJTl2MTgo2X9FfMYjP1wgsYUPslaZQjoDmvS5eo=; b=ZrR7UarYKuLRUIFU8T1dkBHxfIIUKapZJPreUWY4izWzi/cMgX4Gsg927XkTnWyRAQUQ5N sGj2w3dOe2riJyXzu5p5On1096s7vtX/Y4KgLjnJ6BOCPIrCT2KRhqNZ9ku6uKl8NVMjsS 5iQz3/2ClfYBATc6UINfRlKk6qVQ2Z4= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-674-3Mv0bTVcNnGiSvjrzw7oMg-1; Mon, 07 Nov 2022 11:18:24 -0500 X-MC-Unique: 3Mv0bTVcNnGiSvjrzw7oMg-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 05639185A7AA; Mon, 7 Nov 2022 16:18:23 +0000 (UTC) Received: from t480s.redhat.com (unknown [10.39.195.106]) by smtp.corp.redhat.com (Postfix) with ESMTP id A60F24B3FC8; Mon, 7 Nov 2022 16:18:17 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-rdma@vger.kernel.org, linux-media@vger.kernel.org, linux-kselftest@vger.kernel.org, David Hildenbrand , Linus Torvalds , Andrew Morton , Jason Gunthorpe , John Hubbard , Peter Xu , Greg Kroah-Hartman , Andrea Arcangeli , Hugh Dickins , Nadav Amit , Vlastimil Babka , Matthew Wilcox , Mike Kravetz , Muchun Song , Lucas Stach , David Airlie , Oded Gabbay , Arnd Bergmann Subject: [PATCH RFC 06/19] mm: rework handling in do_wp_page() based on private vs. shared mappings Date: Mon, 7 Nov 2022 17:17:27 +0100 Message-Id: <20221107161740.144456-7-david@redhat.com> In-Reply-To: <20221107161740.144456-1-david@redhat.com> References: <20221107161740.144456-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221107_081828_312042_D4B1E6B9 X-CRM114-Status: GOOD ( 19.34 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org We want to extent FAULT_FLAG_UNSHARE support to anything mapped into a COW mapping (pagecache page, zeropage, PFN, ...), not just anonymous pages. Let's prepare for that by handling shared mappings first such that we can handle private mappings last. While at it, use folio-based functions instead of page-based functions where we touch the code either way. Signed-off-by: David Hildenbrand --- mm/memory.c | 38 +++++++++++++++++--------------------- 1 file changed, 17 insertions(+), 21 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 826353da7b23..41e4c697033a 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3341,7 +3341,7 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) { const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE; struct vm_area_struct *vma = vmf->vma; - struct folio *folio; + struct folio *folio = NULL; if (likely(!unshare)) { if (userfaultfd_pte_wp(vma, *vmf->pte)) { @@ -3359,13 +3359,12 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) } vmf->page = vm_normal_page(vma, vmf->address, vmf->orig_pte); - if (!vmf->page) { - if (unlikely(unshare)) { - /* No anonymous page -> nothing to do. */ - pte_unmap_unlock(vmf->pte, vmf->ptl); - return 0; - } + /* + * Shared mapping: we are guaranteed to have VM_WRITE and + * FAULT_FLAG_WRITE set at this point. + */ + if (vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) { /* * VM_MIXEDMAP !pfn_valid() case, or VM_SOFTDIRTY clear on a * VM_PFNMAP VMA. @@ -3373,20 +3372,19 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) * We should not cow pages in a shared writeable mapping. * Just mark the pages writable and/or call ops->pfn_mkwrite. */ - if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) == - (VM_WRITE|VM_SHARED)) + if (!vmf->page) return wp_pfn_shared(vmf); - - pte_unmap_unlock(vmf->pte, vmf->ptl); - return wp_page_copy(vmf); + return wp_page_shared(vmf); } + if (vmf->page) + folio = page_folio(vmf->page); + /* - * Take out anonymous pages first, anonymous shared vmas are - * not dirty accountable. + * Private mapping: create an exclusive anonymous page copy if reuse + * is impossible. We might miss VM_WRITE for FOLL_FORCE handling. */ - folio = page_folio(vmf->page); - if (folio_test_anon(folio)) { + if (folio && folio_test_anon(folio)) { /* * If the page is exclusive to this process we must reuse the * page without further checks. @@ -3437,19 +3435,17 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) /* No anonymous page -> nothing to do. */ pte_unmap_unlock(vmf->pte, vmf->ptl); return 0; - } else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) == - (VM_WRITE|VM_SHARED))) { - return wp_page_shared(vmf); } copy: /* * Ok, we need to copy. Oh, well.. */ - get_page(vmf->page); + if (folio) + folio_get(folio); pte_unmap_unlock(vmf->pte, vmf->ptl); #ifdef CONFIG_KSM - if (PageKsm(vmf->page)) + if (folio && folio_test_ksm(folio)) count_vm_event(COW_KSM); #endif return wp_page_copy(vmf);