From nobody Thu Dec 18 07:20:55 2025 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 7C5B5C2BB3F for ; Mon, 20 Nov 2023 14:16:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232947AbjKTOQQ (ORCPT ); Mon, 20 Nov 2023 09:16:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59834 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232135AbjKTOQO (ORCPT ); Mon, 20 Nov 2023 09:16:14 -0500 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 23AE8A0 for ; Mon, 20 Nov 2023 06:16:11 -0800 (PST) X-IronPort-AV: E=McAfee;i="6600,9927,10900"; a="458122911" X-IronPort-AV: E=Sophos;i="6.04,214,1695711600"; d="scan'208";a="458122911" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Nov 2023 06:16:10 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10900"; a="759795431" X-IronPort-AV: E=Sophos;i="6.04,214,1695711600"; d="scan'208";a="759795431" Received: from fdefranc-mobl3.ger.corp.intel.com (HELO fdefranc-mobl3.Hitronhub.home) ([10.213.12.244]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Nov 2023 06:16:05 -0800 From: "Fabio M. De Francesco" To: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Fabio De Francesco , Ira Weiny , "Fabio M . De Francesco" Subject: [PATCH] mm/util: Use kmap_local_page() in memcmp_pages() Date: Mon, 20 Nov 2023 15:15:27 +0100 Message-ID: <20231120141554.6612-1-fmdefrancesco@gmail.com> X-Mailer: git-send-email 2.42.0 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" From: Fabio De Francesco kmap_atomic() has been deprecated in favor of kmap_local_page(). Therefore, replace kmap_atomic() with kmap_local_page() in memcmp_pages(). kmap_atomic() is implemented like a kmap_local_page() which also disables page-faults and preemption (the latter only in !PREEMPT_RT kernels). The kernel virtual addresses returned by these two API are only valid in the context of the callers (i.e., they cannot be handed to other threads). With kmap_local_page() the mappings are per thread and CPU local like in kmap_atomic(); however, they can handle page-faults and can be called from any context (including interrupts). The tasks that call kmap_local_page() can be preempted and, when they are scheduled to run again, the kernel virtual addresses are restored and are still valid. In memcmp_pages(), the block of code between the mapping and un-mapping does not depend on the above-mentioned side effects of kmap_aatomic(), so that mere replacements of the old API with the new one is all that is required (i.e., there is no need to explicitly call pagefault_disable() and/or preempt_disable()). Cc: Ira Weiny Signed-off-by: Fabio M. De Francesco --- mm/util.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/mm/util.c b/mm/util.c index 744b4d7e3fae..5a6a9802583b 100644 --- a/mm/util.c +++ b/mm/util.c @@ -1047,11 +1047,11 @@ int __weak memcmp_pages(struct page *page1, struct = page *page2) char *addr1, *addr2; int ret; =20 - addr1 =3D kmap_atomic(page1); - addr2 =3D kmap_atomic(page2); + addr1 =3D kmap_local_page(page1); + addr2 =3D kmap_local_page(page2); ret =3D memcmp(addr1, addr2, PAGE_SIZE); - kunmap_atomic(addr2); - kunmap_atomic(addr1); + kunmap_local(addr2); + kunmap_local(addr1); return ret; } =20 --=20 2.42.0