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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 59BACC43387 for ; Tue, 15 Jan 2019 16:14:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3369220657 for ; Tue, 15 Jan 2019 16:14:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731424AbfAOQOn (ORCPT ); Tue, 15 Jan 2019 11:14:43 -0500 Received: from relay.sw.ru ([185.231.240.75]:51454 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727163AbfAOQOn (ORCPT ); Tue, 15 Jan 2019 11:14:43 -0500 Received: from [172.16.25.169] by relay.sw.ru with esmtp (Exim 4.91) (envelope-from ) id 1gjRMO-0004Af-Sc; Tue, 15 Jan 2019 19:14:41 +0300 Subject: Re: [PATCH 2/2] fuse: Replace page without copying in fuse_writepage_in_flight() To: Miklos Szeredi Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org References: <154322517208.18737.3297786654135648324.stgit@localhost.localdomain> <154322557765.18737.14337090699283695815.stgit@localhost.localdomain> From: Kirill Tkhai Message-ID: <30c6d750-01b1-fb7e-eb80-0f60f242974a@virtuozzo.com> Date: Tue, 15 Jan 2019 19:14:39 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15.01.2019 18:39, Miklos Szeredi wrote: > On Mon, Nov 26, 2018 at 10:46 AM Kirill Tkhai wrote: >> >> It looks like we can optimize old_req page replacement >> and avoid copying by simple updating the request's page. >> >> Signed-off-by: Kirill Tkhai >> --- >> fs/fuse/file.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/fs/fuse/file.c b/fs/fuse/file.c >> index c6650c68b31a..83b54b082c86 100644 >> --- a/fs/fuse/file.c >> +++ b/fs/fuse/file.c >> @@ -1778,7 +1778,7 @@ static bool fuse_writepage_in_flight(struct fuse_req *new_req, >> if (old_req->num_pages == 1 && old_req != first_req) { >> struct backing_dev_info *bdi = inode_to_bdi(page->mapping->host); >> >> - copy_highpage(old_req->pages[0], page); >> + swap(old_req->pages[0], page); > > This would mess up refcounting for all pages involved. need to swap > with the temp page in new_req. Fixed version in #for-next. You are sure, page is just a simple pointer, not struct **page. Then we would have had to change fuse_writepage_in_flight() to use ** pointer. Updated version looks good for me. Thanks, Kirill