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,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 276ECC67790 for ; Fri, 27 Jul 2018 12:17:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C81DF208B4 for ; Fri, 27 Jul 2018 12:17:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="TD7gXjv4" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C81DF208B4 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 S1732623AbeG0NjA (ORCPT ); Fri, 27 Jul 2018 09:39:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:34652 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729955AbeG0NjA (ORCPT ); Fri, 27 Jul 2018 09:39:00 -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 0E7BC208AD; Fri, 27 Jul 2018 12:17:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1532693840; bh=xLoq7KD9bjRrtmWGlQBGHUBsfQXvNTc0VBLIG0kzUyk=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=TD7gXjv4+X/Xtu2dsMbqYAwC1MOxHgBGv5Y7q98wc1IyYKBhg91RH9BHEzYZPzaGI ufmB5B/+NBlS0GiOjcJDJ0Yi1/LxFjVl58iYX3nLKuV/HPNQtYa0JHxp/cicCyZ9aO D7VVwGbtRKxAMKNFNcnO9l4uiamIOhKoyNOsp5DA= Subject: Re: [PATCH] f2fs: avoid race between zero_range and background GC To: Jaegeuk Kim , Chao Yu Cc: 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> From: Chao Yu Message-ID: <10d7814b-06d0-6751-ca56-85e7c8b92a27@kernel.org> Date: Fri, 27 Jul 2018 20:16:50 +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: <20180727102916.GI16155@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 2018/7/27 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. > >> 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