From nobody Mon Apr 6 14:55:30 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 8BA56C433FE for ; Tue, 8 Nov 2022 17:48:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234643AbiKHRsJ (ORCPT ); Tue, 8 Nov 2022 12:48:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44352 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234639AbiKHRsG (ORCPT ); Tue, 8 Nov 2022 12:48:06 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CD9C1554F2 for ; Tue, 8 Nov 2022 09:47:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1667929625; 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=6YPbVJPY8MtPnMTid4uTdi1CU5/wNXrXzoHJaI5QF0k=; b=WGbV1U2aDxfQ1lc1pr50AmTwCrCIAULruAnB9rz2fY54yekU4F2zf772pV/T196a/XQGzG yTEDOL8KMkSKtkBO7aGPLeLM+QEByu3wLopnwbvkjRWur7Ww6oXWnGQ6Xs/+QB5t+IePgk JgBYU8OdOgwTNbuAllRcoUVfemFNM/0= Received: from mimecast-mx02.redhat.com (mx3-rdu2.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-589-5U-PXS9XOe-k_dUPBm89IA-1; Tue, 08 Nov 2022 12:47:02 -0500 X-MC-Unique: 5U-PXS9XOe-k_dUPBm89IA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8FB033806738; Tue, 8 Nov 2022 17:47:01 +0000 (UTC) Received: from t480s.fritz.box (unknown [10.39.194.18]) by smtp.corp.redhat.com (Postfix) with ESMTP id B5E20C15BB5; Tue, 8 Nov 2022 17:46:57 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, David Hildenbrand , Linus Torvalds , Andrew Morton , Mel Gorman , Dave Chinner , Nadav Amit , Peter Xu , Andrea Arcangeli , Hugh Dickins , Vlastimil Babka , Michael Ellerman , Nicholas Piggin , Mike Rapoport , Anshuman Khandual Subject: [PATCH v2 1/7] mm/mprotect: allow clean exclusive anon pages to be writable Date: Tue, 8 Nov 2022 18:46:46 +0100 Message-Id: <20221108174652.198904-2-david@redhat.com> In-Reply-To: <20221108174652.198904-1-david@redhat.com> References: <20221108174652.198904-1-david@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Nadav Amit Anonymous pages might have the dirty bit clear, but this should not prevent mprotect from making them writable if they are exclusive. Therefore, skip the test whether the page is dirty in this case. Note that there are already other ways to get a writable PTE mapping an anonymous page that is clean: for example, via MADV_FREE. In an ideal world, we'd have a different indication from the FS whether writenotify is still required. Signed-off-by: Nadav Amit [ return directly; update description ] Signed-off-by: David Hildenbrand --- mm/mprotect.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/mm/mprotect.c b/mm/mprotect.c index 8d770855b591..86a28c0e190f 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -46,7 +46,7 @@ static inline bool can_change_pte_writable(struct vm_area= _struct *vma, =20 VM_BUG_ON(!(vma->vm_flags & VM_WRITE) || pte_write(pte)); =20 - if (pte_protnone(pte) || !pte_dirty(pte)) + if (pte_protnone(pte)) return false; =20 /* Do we need write faults for softdirty tracking? */ @@ -65,11 +65,10 @@ static inline bool can_change_pte_writable(struct vm_ar= ea_struct *vma, * the PT lock. */ page =3D vm_normal_page(vma, addr, pte); - if (!page || !PageAnon(page) || !PageAnonExclusive(page)) - return false; + return page && PageAnon(page) && PageAnonExclusive(page); } =20 - return true; + return pte_dirty(pte); } =20 static unsigned long change_pte_range(struct mmu_gather *tlb, --=20 2.38.1