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 108F3C433EF for ; Wed, 13 Jul 2022 18:28:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236401AbiGMS2c (ORCPT ); Wed, 13 Jul 2022 14:28:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33508 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236674AbiGMS23 (ORCPT ); Wed, 13 Jul 2022 14:28:29 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 279B92ED6E for ; Wed, 13 Jul 2022 11:28:28 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A7C0C61B10 for ; Wed, 13 Jul 2022 18:28:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A0B7DC34114; Wed, 13 Jul 2022 18:28:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1657736907; bh=024PDpb4vG1SYLNLpOleR7LwxDGQZrTQ/VrYxAkAb0k=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=G3npnU8cqSfirbehcrUP6HCEGPXzejeR2SCQcPzvl8EotN/2EOD+zWIixJd349A4v lmpeoYDy+bJJ/hLhemdkuUZaVenRqR8xZ/TUxEvOnTZP4HXQODAxx6M2ePAxW8Z1or lZySa4PCfm7OL8ICm+RUOqPHLlLO8F11Fe6LfpPI= Date: Wed, 13 Jul 2022 20:28:24 +0200 From: Greg KH To: matt.hsiao@hpe.com Cc: linux-kernel@vger.kernel.org, arnd@arndb.de, jerry.hoemann@hpe.com, scott.norton@hpe.com, camille.lu@hpe.com, geoffrey.ndu@hpe.com, gustavo.knuppe@hpe.com Subject: Re: [PATCH v2 1/1] misc: hpilo: switch .{read,write} ops to .{read,write}_iter Message-ID: References: <20220713175452.4221-1-matt.hsiao@hpe.com> <20220713175452.4221-2-matt.hsiao@hpe.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220713175452.4221-2-matt.hsiao@hpe.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 14, 2022 at 01:54:52AM +0800, matt.hsiao@hpe.com wrote: > From: Matt Hsiao > > Commit 4d03e3cc59828c82ee89 ("fs: don't allow kernel reads and writes > without iter ops") requested exclusive .{read,write}_iter ops for > kernel_{read,write}. To support dependent drivers to access hpilo by > kernel_{read,write}, switch .{read,write} ops to their iter variants. > > Signed-off-by: Matt Hsiao So this fixes a bug? What commit does this fix? Should it go to stable branches? If so, which ones? But my main question is I have no idea what the changelog means here. What is a "dependent driver"? What does "exclusive" mean here? What is a iter variant? > --- > drivers/misc/hpilo.c | 31 ++++++++++++++++++------------- > 1 file changed, 18 insertions(+), 13 deletions(-) > > diff --git a/drivers/misc/hpilo.c b/drivers/misc/hpilo.c > index 8d00df9243c4..5d431a56b7eb 100644 > --- a/drivers/misc/hpilo.c > +++ b/drivers/misc/hpilo.c > @@ -23,6 +23,7 @@ > #include > #include > #include > +#include > #include "hpilo.h" > > static struct class *ilo_class; > @@ -435,14 +436,14 @@ static void ilo_set_reset(struct ilo_hwinfo *hw) > } > } > > -static ssize_t ilo_read(struct file *fp, char __user *buf, > - size_t len, loff_t *off) > +static ssize_t ilo_read_iter(struct kiocb *iocb, struct iov_iter *to) > { > - int err, found, cnt, pkt_id, pkt_len; > - struct ccb_data *data = fp->private_data; > + int err = 0, found, cnt, pkt_id, pkt_len; > + struct ccb_data *data = iocb->ki_filp->private_data; > struct ccb *driver_ccb = &data->driver_ccb; > struct ilo_hwinfo *hw = data->ilo_hw; > void *pkt; > + size_t len = iov_iter_count(to), copied; > > if (is_channel_reset(driver_ccb)) { > /* > @@ -477,7 +478,9 @@ static ssize_t ilo_read(struct file *fp, char __user *buf, > if (pkt_len < len) > len = pkt_len; > > - err = copy_to_user(buf, pkt, len); > + copied = copy_to_iter(pkt, len, to); > + if (unlikely(copied != len)) Why unlikely? If you can prove it is needed in benchmarks, great, otherwise never add likely/unlikely as they are almost always wrong and the compiler and cpu can do it better. > + err = -EFAULT; > > /* return the received packet to the queue */ > ilo_pkt_enqueue(hw, driver_ccb, RECVQ, pkt_id, desc_mem_sz(1)); > @@ -485,14 +488,14 @@ static ssize_t ilo_read(struct file *fp, char __user *buf, > return err ? -EFAULT : len; > } > > -static ssize_t ilo_write(struct file *fp, const char __user *buf, > - size_t len, loff_t *off) > +static ssize_t ilo_write_iter(struct kiocb *iocb, struct iov_iter *from) > { > - int err, pkt_id, pkt_len; > - struct ccb_data *data = fp->private_data; > + int err = 0, pkt_id, pkt_len; > + struct ccb_data *data = iocb->ki_filp->private_data; > struct ccb *driver_ccb = &data->driver_ccb; > struct ilo_hwinfo *hw = data->ilo_hw; > void *pkt; > + size_t len = iov_iter_count(from), copied; > > if (is_channel_reset(driver_ccb)) > return -ENODEV; > @@ -506,9 +509,11 @@ static ssize_t ilo_write(struct file *fp, const char __user *buf, > len = pkt_len; > > /* on failure, set the len to 0 to return empty packet to the device */ > - err = copy_from_user(pkt, buf, len); > - if (err) > + copied = copy_from_iter(pkt, len, from); > + if (unlikely(copied != len)) { Same here. thanks, greg k-h