From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=68fk=DU=lists.ozlabs.org=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@kernel.org>
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 8867AC433DF
	for <linuxppc-dev@archiver.kernel.org>; Tue, 13 Oct 2020 20:04:45 +0000 (UTC)
Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by mail.kernel.org (Postfix) with ESMTPS id A443A20BED
	for <linuxppc-dev@archiver.kernel.org>; Tue, 13 Oct 2020 20:04:44 +0000 (UTC)
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A443A20BED
Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zeniv.linux.org.uk
Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org
Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3])
	by lists.ozlabs.org (Postfix) with ESMTP id 4C9mjQ1r2GzDqfY
	for <linuxppc-dev@archiver.kernel.org>; Wed, 14 Oct 2020 07:04:42 +1100 (AEDT)
Authentication-Results: lists.ozlabs.org; spf=none (no SPF record)
 smtp.mailfrom=ftp.linux.org.uk (client-ip=2002:c35c:fd02::1;
 helo=zeniv.linux.org.uk; envelope-from=viro@ftp.linux.org.uk;
 receiver=<UNKNOWN>)
Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none)
 header.from=zeniv.linux.org.uk
Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [IPv6:2002:c35c:fd02::1])
 (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)
 key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256)
 (No client certificate requested)
 by lists.ozlabs.org (Postfix) with ESMTPS id 4C9mg76mGDzDqZl;
 Wed, 14 Oct 2020 07:02:40 +1100 (AEDT)
Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat
 Linux)) id 1kSQUX-00H96b-NT; Tue, 13 Oct 2020 20:01:49 +0000
Date: Tue, 13 Oct 2020 21:01:49 +0100
From: Al Viro <viro@zeniv.linux.org.uk>
To: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH RFC PKS/PMEM 33/58] fs/cramfs: Utilize new kmap_thread()
Message-ID: <20201013200149.GI3576660@ZenIV.linux.org.uk>
References: <20201009195033.3208459-1-ira.weiny@intel.com>
 <20201009195033.3208459-34-ira.weiny@intel.com>
 <CAPcyv4gL3jfw4d+SJGPqAD3Dp4F_K=X3domuN4ndAA1FQDGcPg@mail.gmail.com>
 <20201013193643.GK20115@casper.infradead.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20201013193643.GK20115@casper.infradead.org>
X-BeenThere: linuxppc-dev@lists.ozlabs.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Linux on PowerPC Developers Mail List <linuxppc-dev.lists.ozlabs.org>
List-Unsubscribe: <https://lists.ozlabs.org/options/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=unsubscribe>
List-Archive: <http://lists.ozlabs.org/pipermail/linuxppc-dev/>
List-Post: <mailto:linuxppc-dev@lists.ozlabs.org>
List-Help: <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=help>
List-Subscribe: <https://lists.ozlabs.org/listinfo/linuxppc-dev>,
 <mailto:linuxppc-dev-request@lists.ozlabs.org?subject=subscribe>
Cc: linux-aio@kvack.org, linux-efi <linux-efi@vger.kernel.org>,
 KVM list <kvm@vger.kernel.org>,
 Linux Doc Mailing List <linux-doc@vger.kernel.org>,
 Peter Zijlstra <peterz@infradead.org>, linux-mmc@vger.kernel.org,
 Dave Hansen <dave.hansen@linux.intel.com>,
 Maling list - DRI developers <dri-devel@lists.freedesktop.org>,
 Linux MM <linux-mm@kvack.org>, target-devel@vger.kernel.org,
 linux-mtd@lists.infradead.org, linux-kselftest@vger.kernel.org,
 samba-technical@lists.samba.org, "Weiny, Ira" <ira.weiny@intel.com>,
 Dan Williams <dan.j.williams@intel.com>, drbd-dev@lists.linbit.com,
 devel@driverdev.osuosl.org, linux-cifs@vger.kernel.org,
 linux-nilfs@vger.kernel.org, linux-scsi <linux-scsi@vger.kernel.org>,
 linux-nvdimm <linux-nvdimm@lists.01.org>,
 linux-rdma <linux-rdma@vger.kernel.org>, X86 ML <x86@kernel.org>,
 ceph-devel@vger.kernel.org, amd-gfx list <amd-gfx@lists.freedesktop.org>,
 io-uring@vger.kernel.org, cluster-devel@redhat.com,
 Ingo Molnar <mingo@redhat.com>, intel-wired-lan@lists.osuosl.org,
 xen-devel <xen-devel@lists.xenproject.org>,
 linux-ext4 <linux-ext4@vger.kernel.org>, Fenghua Yu <fenghua.yu@intel.com>,
 linux-afs@lists.infradead.org, linux-um@lists.infradead.org,
 intel-gfx@lists.freedesktop.org, ecryptfs@vger.kernel.org,
 linux-erofs@lists.ozlabs.org, reiserfs-devel@vger.kernel.org,
 linux-block@vger.kernel.org, linux-bcache@vger.kernel.org,
 Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>,
 Thomas Gleixner <tglx@linutronix.de>,
 Andrew Morton <akpm@linux-foundation.org>, linux-cachefs@redhat.com,
 linux-nfs@vger.kernel.org, Nicolas Pitre <nico@fluxnic.net>,
 linux-ntfs-dev@lists.sourceforge.net, Netdev <netdev@vger.kernel.org>,
 Kexec Mailing List <kexec@lists.infradead.org>,
 Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
 linux-f2fs-devel@lists.sourceforge.net,
 linux-fsdevel <linux-fsdevel@vger.kernel.org>, bpf@vger.kernel.org,
 linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
 linux-btrfs <linux-btrfs@vger.kernel.org>
Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org
Sender: "Linuxppc-dev"
 <linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org>

On Tue, Oct 13, 2020 at 08:36:43PM +0100, Matthew Wilcox wrote:

> static inline void copy_to_highpage(struct page *to, void *vfrom, unsigned int size)
> {
> 	char *vto = kmap_atomic(to);
> 
> 	memcpy(vto, vfrom, size);
> 	kunmap_atomic(vto);
> }
> 
> in linux/highmem.h ?

You mean, like
static void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)
{
        char *from = kmap_atomic(page);
        memcpy(to, from + offset, len);
        kunmap_atomic(from);
}

static void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len)
{
        char *to = kmap_atomic(page);
        memcpy(to + offset, from, len);
        kunmap_atomic(to);
}

static void memzero_page(struct page *page, size_t offset, size_t len)
{
        char *addr = kmap_atomic(page);
        memset(addr + offset, 0, len);
        kunmap_atomic(addr);
}

in lib/iov_iter.c?  FWIW, I don't like that "highpage" in the name and
highmem.h as location - these make perfect sense regardless of highmem;
they are normal memory operations with page + offset used instead of
a pointer...