From mboxrd@z Thu Jan 1 00:00:00 1970 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 C6BACC43334 for ; Mon, 13 Jun 2022 07:55:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237307AbiFMHz0 convert rfc822-to-8bit (ORCPT ); Mon, 13 Jun 2022 03:55:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37008 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239562AbiFMHxh (ORCPT ); Mon, 13 Jun 2022 03:53:37 -0400 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.85.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 61BF11DA76 for ; Mon, 13 Jun 2022 00:53:25 -0700 (PDT) Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-196-fmC_hegiM8eHASEyRoy8hA-1; Mon, 13 Jun 2022 08:53:21 +0100 X-MC-Unique: fmC_hegiM8eHASEyRoy8hA-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.36; Mon, 13 Jun 2022 08:53:19 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.036; Mon, 13 Jun 2022 08:53:19 +0100 From: David Laight To: 'Joe Damato' , Alexander Viro , "linux-kernel@vger.kernel.org" Subject: RE: [RFC,iov_iter v2 3/8] iov_iter: add copyin_iovec helper Thread-Topic: [RFC,iov_iter v2 3/8] iov_iter: add copyin_iovec helper Thread-Index: AQHYfjsvbNyOWJFJ/E+wgYg8ABCKpa1M98Iw Date: Mon, 13 Jun 2022 07:53:19 +0000 Message-ID: <8f6771a01fe74cde86641e780d31a2ce@AcuMS.aculab.com> References: <1655024280-23827-1-git-send-email-jdamato@fastly.com> <1655024280-23827-4-git-send-email-jdamato@fastly.com> In-Reply-To: <1655024280-23827-4-git-send-email-jdamato@fastly.com> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Joe Damato > Sent: 12 June 2022 09:58 > > copyin_iovec is a helper which wraps copyin and selects the right copy > method based on the iter_copy_type. A pretty bad description. > Signed-off-by: Joe Damato > --- > lib/iov_iter.c | 19 ++++++++++++++----- > 1 file changed, 14 insertions(+), 5 deletions(-) > > diff --git a/lib/iov_iter.c b/lib/iov_iter.c > index d32d7e5..6720cb2 100644 > --- a/lib/iov_iter.c > +++ b/lib/iov_iter.c > @@ -168,6 +168,15 @@ static int copyin(void *to, const void __user *from, size_t n) > return n; > } > > +static int copyin_iovec(void *to, const void __user *from, size_t n, > + struct iov_iter *i) > +{ > + if (unlikely(iov_iter_copy_is_nt(i))) > + return __copy_from_user_nocache(to, from, n); > + else > + return copyin(to, from, n); > +} Isn't this extra conditional going to have a measurable impact on all the normal copy paths? The additional costs of all the 'iovec' types is bad enough already. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)