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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 76816C4346A for ; Mon, 21 Sep 2020 14:38:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4185A2220C for ; Mon, 21 Sep 2020 14:38:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727693AbgIUOiK convert rfc822-to-8bit (ORCPT ); Mon, 21 Sep 2020 10:38:10 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([207.82.80.151]:51728 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727680AbgIUOiH (ORCPT ); Mon, 21 Sep 2020 10:38:07 -0400 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-140-oNDip4LCObWi5fVxcGZ2UA-1; Mon, 21 Sep 2020 15:38:02 +0100 X-MC-Unique: oNDip4LCObWi5fVxcGZ2UA-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Mon, 21 Sep 2020 15:38:02 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Mon, 21 Sep 2020 15:38:02 +0100 From: David Laight To: 'Christoph Hellwig' CC: "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" , "io-uring@vger.kernel.org" , Jens Axboe , "David S. Miller" , Al Viro , linux-fsdevel Subject: RE: [PATCH 4/9 next] fs/io_uring Don't use the return value from import_iovec(). Thread-Topic: [PATCH 4/9 next] fs/io_uring Don't use the return value from import_iovec(). Thread-Index: AdaLbe1b5RzSfSnfQoqJG9wxedvDFgEq0XAAAALSu0A= Date: Mon, 21 Sep 2020 14:38:02 +0000 Message-ID: <4b204a3e4db74cb2bd8c81e31f6b359b@AcuMS.aculab.com> References: <0dc67994b6b2478caa3d96a9e24d2bfb@AcuMS.aculab.com> <20200921141456.GD24515@infradead.org> In-Reply-To: <20200921141456.GD24515@infradead.org> 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-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org From: Christoph Hellwig > Sent: 21 September 2020 15:15 > > On Tue, Sep 15, 2020 at 02:55:20PM +0000, David Laight wrote: > > > > This is the only code that relies on import_iovec() returning > > iter.count on success. > > This allows a better interface to import_iovec(). > > This looks generall sane, but a comment below: > > > @@ -3123,7 +3123,7 @@ static int io_read(struct io_kiocb *req, bool force_nonblock, > > if (ret < 0) > > return ret; > > iov_count = iov_iter_count(iter); > > - io_size = ret; > > + io_size = iov_count; > > req->result = io_size; > > ret = 0; > > > > @@ -3246,7 +3246,7 @@ static int io_write(struct io_kiocb *req, bool force_nonblock, > > if (ret < 0) > > return ret; > > iov_count = iov_iter_count(iter); > > - io_size = ret; > > + io_size = iov_count; > > req->result = io_size; > > I tink the local iov_count variable can go away in both functions, > as io_size only changes after the last use of iov_count (io_read) or > not at all (io_write). Yes, the compiler will probably make that optimisation. I did a minimal change because my head hurts whenever I look at io_uring.c. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)