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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH 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 4D93EC43142 for ; Sun, 29 Jul 2018 02:54:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E714020899 for ; Sun, 29 Jul 2018 02:54:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="v6y5gd2Y" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E714020899 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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 S1726211AbeG2EWr (ORCPT ); Sun, 29 Jul 2018 00:22:47 -0400 Received: from mail.kernel.org ([198.145.29.99]:60260 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725856AbeG2EWq (ORCPT ); Sun, 29 Jul 2018 00:22:46 -0400 Received: from [192.168.0.101] (unknown [180.111.102.36]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9212320893; Sun, 29 Jul 2018 02:54:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1532832841; bh=68xUfhKEmnhSFkkCZklvU/LIKTPXO0emH2/2dWbrEHQ=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=v6y5gd2Ygctmx/L5IhJpCNJvseGxQ7tJrpxZhzayTTEbiWxBtWFYzDYqTEz/y93t4 WAXFMbXY0g1mZqYAI3wov088+RZJL9fvse2cQc4IbWcqcO6CaCT0/ReX7eNw+0T3dB GZN+m5p6jUYt8No2EzqTX7aLWGqRazEHIK78rvCU= Subject: Re: [PATCH] f2fs: avoid race between zero_range and background GC To: Jaegeuk Kim Cc: Chao Yu , linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org References: <20180726104536.114340-1-yuchao0@huawei.com> <20180727102916.GI16155@jaegeuk-macbookpro.roam.corp.google.com> <10d7814b-06d0-6751-ca56-85e7c8b92a27@kernel.org> <20180729020254.GH83620@jaegeuk-macbookpro.roam.corp.google.com> From: Chao Yu Message-ID: <6d86bad1-52fa-2309-9403-47490345e372@kernel.org> Date: Sun, 29 Jul 2018 10:53:58 +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: <20180729020254.GH83620@jaegeuk-macbookpro.roam.corp.google.com> 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 2018/7/29 10:02, Jaegeuk Kim wrote: > On 07/27, Chao Yu wrote: >> On 2018/7/27 18:29, Jaegeuk Kim wrote: >>> On 07/26, Chao Yu wrote: >>>> Thread A Background GC >>>> - f2fs_zero_range >>>> - truncate_pagecache_range >>>> - gc_data_segment >>>> - get_read_data_page >>>> - move_data_page >>>> - set_page_dirty >>>> - set_cold_data >>>> - f2fs_do_zero_range >>>> - dn->data_blkaddr = NEW_ADDR; >>>> - f2fs_set_data_blkaddr >>>> >>>> Actually, we don't need to set dirty & checked flag on the page, since >>>> all valid data in the page should be zeroed by zero_range(). >>> >>> But, it doesn't matter too much, right? >> >> No, if the dirtied page is writebacked after f2fs_do_zero_range(), result of >> zero_range() should be wrong, as zeroed page contains valid user data. > > How about truncating page caches after block address change or doing it twice > before and after? Thread A Background GC - f2fs_zero_range - truncate_pagecache_range - gc_data_segment - get_read_data_page - move_data_page - set_page_dirty - set_cold_data - f2fs_do_zero_range - dn->data_blkaddr = NEW_ADDR; - f2fs_set_data_blkaddr bdi-flusher - __write_data_page - f2fs_update_data_blkaddr : data_blkaddr has been updated here. - truncate_pagecache_range : data & dnode has been writebacked before page cache truncation? How about this case? Thanks, > >> >>> >>>> Use i_gc_rwsem[WRITE] to avoid such race condition. >>> >>> Hope to avoid abusing i_gc_rwsem[] tho. >> >> Agreed, let's try avoiding until we have to use it. >> >> Thanks, >> >>> >>>> >>>> Signed-off-by: Chao Yu >>>> --- >>>> fs/f2fs/file.c | 2 ++ >>>> 1 file changed, 2 insertions(+) >>>> >>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >>>> index 267ec3794e1e..7bd2412a8c37 100644 >>>> --- a/fs/f2fs/file.c >>>> +++ b/fs/f2fs/file.c >>>> @@ -1309,6 +1309,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, >>>> if (ret) >>>> return ret; >>>> >>>> + down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >>>> down_write(&F2FS_I(inode)->i_mmap_sem); >>>> ret = filemap_write_and_wait_range(mapping, offset, offset + len - 1); >>>> if (ret) >>>> @@ -1389,6 +1390,7 @@ static int f2fs_zero_range(struct inode *inode, loff_t offset, loff_t len, >>>> } >>>> out_sem: >>>> up_write(&F2FS_I(inode)->i_mmap_sem); >>>> + up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); >>>> >>>> return ret; >>>> } >>>> -- >>>> 2.18.0.rc1