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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 E86D7C43441 for ; Thu, 22 Nov 2018 10:29:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 99C8D20684 for ; Thu, 22 Nov 2018 10:29:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 99C8D20684 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2394373AbeKVVIc (ORCPT ); Thu, 22 Nov 2018 16:08:32 -0500 Received: from szxga06-in.huawei.com ([45.249.212.32]:38677 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2388128AbeKVVIc (ORCPT ); Thu, 22 Nov 2018 16:08:32 -0500 Received: from DGGEMS405-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 9E3E5A4B3FC57; Thu, 22 Nov 2018 18:29:40 +0800 (CST) Received: from [10.151.23.176] (10.151.23.176) by smtp.huawei.com (10.3.19.205) with Microsoft SMTP Server (TLS) id 14.3.408.0; Thu, 22 Nov 2018 18:29:34 +0800 Subject: Re: [PATCH 04/10] staging: erofs: fix `erofs_workgroup_{try_to_freeze, unfreeze}' To: Greg Kroah-Hartman CC: , , Chao Yu , LKML , , Miao Xie References: <20181120143425.43637-1-gaoxiang25@huawei.com> <20181120143425.43637-5-gaoxiang25@huawei.com> <20181122102155.GE3189@kroah.com> From: Gao Xiang Message-ID: Date: Thu, 22 Nov 2018 18:29:34 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <20181122102155.GE3189@kroah.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.151.23.176] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Greg, On 2018/11/22 18:21, Greg Kroah-Hartman wrote: > On Tue, Nov 20, 2018 at 10:34:19PM +0800, Gao Xiang wrote: >> There are two minor issues in the current freeze interface: >> >> 1) Freeze interfaces have not related with CONFIG_DEBUG_SPINLOCK, >> therefore fix the incorrect conditions; >> >> 2) For SMP platforms, it should also disable preemption before >> doing atomic_cmpxchg in case that some high priority tasks >> preempt between atomic_cmpxchg and disable_preempt, then spin >> on the locked refcount later. > > spinning on a refcount implies that you are trying to do your own type > of locking. Why not use the in-kernel locking api instead? It will > always do better than trying to do your own logic as the developers > there know locking across all types of cpus better than filesystem > developers :) It is because refcount also plays a role as a spinlock on a specific value (== EROFS_LOCKED_MAGIC), no need to introduce such a value since the spin window is small. Thanks, Gao Xiang > > thanks, > > greg k-h >