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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E301BC433EF for ; Mon, 13 Dec 2021 08:31:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:In-Reply-To:References: Message-ID:Date:Subject:CC:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=oJLJtim5XMaH46azOcm110eQ4baRTXXa2q0HjXkXGdE=; b=SBdLea7c9B4xYS 3hbSrGKvJwuSf2NXkVLhwWvJKiFpqv5l2Djaw9kv8UpBlgeI3JfI9eMTcefiJMue4gj3HQwU0Yrr4 YOUMSfwPl/TjlMsfzkJgJTB5HOkPfTN8k4kso0boC11nPF+FFuraql314g3UAkEExFYdVT3FUoDm3 1g3kMuSwKUa3klgNOl71BrDMb0WDwLKcSkPLt3LOJK0KZ8gXUZ1w/KiK7J8Qcj1nXWCh1iSpFfhu/ ksShpIA9n+L58mKPbBJx7w+70eYBfp4tivd+sQvU7fX8UFcqGAUtN9VWlv/3UfyILJOyCQolT3W5C J36GMpuANQIe3xCf8pRA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mwgjP-008IT5-I6; Mon, 13 Dec 2021 08:30:47 +0000 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.85.151]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mwgjM-008IR6-MK for linux-riscv@lists.infradead.org; Mon, 13 Dec 2021 08:30:46 +0000 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-48-uEn-QkNbO3KqUuXVw7bKDg-1; Mon, 13 Dec 2021 08:30:34 +0000 X-MC-Unique: uEn-QkNbO3KqUuXVw7bKDg-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 15.0.1497.26; Mon, 13 Dec 2021 08:30:33 +0000 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.026; Mon, 13 Dec 2021 08:30:33 +0000 From: David Laight To: 'Matthew Wilcox' CC: 'Tiezhu Yang' , Dave Young , Baoquan He , Vivek Goyal , Andrew Morton , "linux-arm-kernel@lists.infradead.org" , "linux-ia64@vger.kernel.org" , "linux-mips@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-riscv@lists.infradead.org" , "linux-sh@vger.kernel.org" , "x86@kernel.org" , "linux-fsdevel@vger.kernel.org" , "kexec@lists.infradead.org" , "linux-kernel@vger.kernel.org" , Xuefeng Li Subject: RE: [PATCH v2 0/2] kdump: simplify code Thread-Topic: [PATCH v2 0/2] kdump: simplify code Thread-Index: AQHX7j/jzYqw5kMpA0qY43nH0kUm2Kwtku5wgAEsrYCAAVr28A== Date: Mon, 13 Dec 2021 08:30:33 +0000 Message-ID: References: <1639193588-7027-1-git-send-email-yangtiezhu@loongson.cn> <0c5cb37139af4f3e85cc2c5115d7d006@AcuMS.aculab.com> In-Reply-To: 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211213_003045_047131_A3F92447 X-CRM114-Status: GOOD ( 14.39 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org From: Matthew Wilcox > Sent: 12 December 2021 11:48 > > On Sat, Dec 11, 2021 at 05:53:46PM +0000, David Laight wrote: > > From: Tiezhu Yang > > > Sent: 11 December 2021 03:33 > > > > > > v2: > > > -- add copy_to_user_or_kernel() in lib/usercopy.c > > > -- define userbuf as bool type > > > > Instead of having a flag to indicate whether the buffer is user or kernel, > > would it be better to have two separate buffer pointers. > > One for a user space buffer, the other for a kernel space buffer. > > Exactly one of the buffers should always be NULL. > > No. You should be using an iov_iter instead. See > https://lore.kernel.org/all/Ya4bdB0UBJCZhUSo@casper.infradead.org/ > for a start on this. iov_iter gets horribly expensive... David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales) _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv