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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 D3B20C3A59B for ; Fri, 30 Aug 2019 16:49:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B016620820 for ; Fri, 30 Aug 2019 16:49:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728257AbfH3QtS (ORCPT ); Fri, 30 Aug 2019 12:49:18 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:3962 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727883AbfH3QtS (ORCPT ); Fri, 30 Aug 2019 12:49:18 -0400 Received: from DGGEMM404-HUB.china.huawei.com (unknown [172.30.72.53]) by Forcepoint Email with ESMTP id 6662DE36B8648C21C1E2; Sat, 31 Aug 2019 00:49:16 +0800 (CST) Received: from dggeme762-chm.china.huawei.com (10.3.19.108) by DGGEMM404-HUB.china.huawei.com (10.3.20.212) with Microsoft SMTP Server (TLS) id 14.3.439.0; Sat, 31 Aug 2019 00:49:15 +0800 Received: from architecture4 (10.140.130.215) by dggeme762-chm.china.huawei.com (10.3.19.108) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1591.10; Sat, 31 Aug 2019 00:49:15 +0800 Date: Sat, 31 Aug 2019 00:48:27 +0800 From: Gao Xiang To: Christoph Hellwig CC: Chao Yu , Dan Carpenter , Joe Perches , Greg Kroah-Hartman , , LKML , , Chao Yu , Miao Xie , , "Fang Wei" Subject: Re: [PATCH v3 7/7] erofs: redundant assignment in __erofs_get_meta_page() Message-ID: <20190830164827.GA107220@architecture4> References: <20190830032006.GA20217@architecture4> <20190830033643.51019-1-gaoxiang25@huawei.com> <20190830033643.51019-7-gaoxiang25@huawei.com> <20190830162812.GA10694@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20190830162812.GA10694@infradead.org> User-Agent: Mutt/1.9.4 (2018-02-28) X-Originating-IP: [10.140.130.215] X-ClientProxiedBy: dggeme705-chm.china.huawei.com (10.1.199.101) To dggeme762-chm.china.huawei.com (10.3.19.108) X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Christoph, On Fri, Aug 30, 2019 at 09:28:12AM -0700, Christoph Hellwig wrote: > > - err = bio_add_page(bio, page, PAGE_SIZE, 0); > > - if (err != PAGE_SIZE) { > > + if (bio_add_page(bio, page, PAGE_SIZE, 0) != PAGE_SIZE) { > > err = -EFAULT; > > goto err_out; > > } > > This patch looks like an improvement. But looking at that whole > area just makes me cringe. OK, I agree with you, I will improve it or just kill them all with new iomap approach after it supports tail-end packing inline. > > Why is there __erofs_get_meta_page with the two weird booleans instead > of a single erofs_get_meta_page that gets and gfp_t for additional > flags and an unsigned int for additional bio op flags. I agree with you. Thanks for your suggestion. > > Why do need ioprio support to start with? Seeing that in a new > fs look kinda odd. Do you have benchmarks that show the difference? I don't have some benchmark for all of these, can I just set REQ_PRIO for all metadata? is that reasonable? Could you kindly give some suggestion on this? > > That function then calls erofs_grab_bio, which tries to handle a > bio_alloc failure, except that the function will not actually fail > due the mempool backing it. It also seems like and awfully > huge function to inline. OK, I will simplify it. Thanks for your suggestion. > > Why is there __submit_bio which really just obsfucates what is > going on? Also why is __submit_bio using bio_set_op_attrs instead > of opencode it as the comment right next to it asks you to? Originally, mainly due to backport consideration since some of our smartphones use 3.x kernel as well... > > Also I really don't understand why you can't just use read_cache_page > or even read_cache_page_gfp instead of __erofs_get_meta_page. > That function is a whole lot of duplication of functionality shared > by a lot of other file systems. OK, I have to admit, that code was originally just copied from f2fs with some modification (maybe it's not a good example for us). Thanks, Gao Xiang