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 D8A27C3A5A4 for ; Mon, 2 Sep 2019 01:16:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AEF142184D for ; Mon, 2 Sep 2019 01:16:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729246AbfIBBQp (ORCPT ); Sun, 1 Sep 2019 21:16:45 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:5264 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729117AbfIBBQp (ORCPT ); Sun, 1 Sep 2019 21:16:45 -0400 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 05DDA2834E6AD09C6159; Mon, 2 Sep 2019 09:16:42 +0800 (CST) Received: from [10.134.22.195] (10.134.22.195) by smtp.huawei.com (10.3.19.214) with Microsoft SMTP Server (TLS) id 14.3.439.0; Mon, 2 Sep 2019 09:16:35 +0800 Subject: Re: [PATCH v4] f2fs: add bio cache for IPU To: Jaegeuk Kim CC: , , References: <20190219081529.5106-1-yuchao0@huawei.com> <20190901071757.GA49907@jaegeuk-macbookpro.roam.corp.google.com> From: Chao Yu Message-ID: <024fe351-8e25-35cd-47a7-9755498c73f4@huawei.com> Date: Mon, 2 Sep 2019 09:16:35 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190901071757.GA49907@jaegeuk-macbookpro.roam.corp.google.com> Content-Type: text/plain; charset="windows-1252" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.134.22.195] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/9/1 15:17, Jaegeuk Kim wrote: > On 08/31, Chao Yu wrote: >> On 2019/2/19 16:15, Chao Yu wrote: >>> @@ -1976,10 +2035,13 @@ static int __write_data_page(struct page *page, bool *submitted, >>> } >>> >>> unlock_page(page); >>> - if (!S_ISDIR(inode->i_mode) && !IS_NOQUOTA(inode)) >>> + if (!S_ISDIR(inode->i_mode) && !IS_NOQUOTA(inode)) { >>> + f2fs_submit_ipu_bio(sbi, bio, page); >>> f2fs_balance_fs(sbi, need_balance_fs); >>> + } >> >> Above bio submission was added to avoid below deadlock: >> >> - __write_data_page >> - f2fs_do_write_data_page >> - set_page_writeback ---- set writeback flag >> - f2fs_inplace_write_data >> - f2fs_balance_fs >> - f2fs_gc >> - do_garbage_collect >> - gc_data_segment >> - move_data_page >> - f2fs_wait_on_page_writeback >> - wait_on_page_writeback --- wait writeback >> >> However, it breaks the merge of IPU IOs, to solve this issue, it looks we need >> to add global bio cache for such IPU merge case, then later >> f2fs_wait_on_page_writeback can check whether writebacked page is cached or not, >> and do the submission if necessary. >> >> Jaegeuk, any thoughts? > > How about calling f2fs_submit_ipu_bio() when we need to do GC in the same > context? However it also could happen in race case: Thread A Thread B - __write_data_page (inode x, page y) - f2fs_do_write_data_page - set_page_writeback ---- set writeback flag in page y - f2fs_inplace_write_data - f2fs_balance_fs - lock gc_mutex - lock gc_mutex - f2fs_gc - do_garbage_collect - gc_data_segment - move_data_page - f2fs_wait_on_page_writeback - wait_on_page_writeback --- wait writeback of page y So it needs a global bio cache for merged IPU pages, how about adding a list to link all ipu bios in struct f2fs_bio_info? struct f2fs_bio_info { .... struct list_head ipu_bio_list; /* track all ipu bio */ spinlock_t ipu_bio_lock; /* protect ipu bio list */ } > >> >> Thanks, > . >