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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH,USER_AGENT_MUTT 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 890B9C28CF6 for ; Sun, 29 Jul 2018 02:03:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 42D3A20862 for ; Sun, 29 Jul 2018 02:03:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="gTzEnw6p" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 42D3A20862 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 S1731699AbeG2Dbb (ORCPT ); Sat, 28 Jul 2018 23:31:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:55648 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731502AbeG2Dbb (ORCPT ); Sat, 28 Jul 2018 23:31:31 -0400 Received: from localhost (c-67-160-202-76.hsd1.ca.comcast.net [67.160.202.76]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2AAE120862; Sun, 29 Jul 2018 02:02:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1532829775; bh=P2eq149ZsGgr/AQxsp90I4lo+LCRR+5n3n6Ug9xcRwo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=gTzEnw6pWyarJij6JdoSkLjRhE3Z9xXp1MGo+8d8tg3PdcYVCbaGkKeiNaJLYoFoF SDl8LPyLsVZ9ig/bL5ml1hdmNlrhD3n41nXlozXkFFCTQJeSoNtK1r1lisVrCDVhT2 OqGqX1yv911ISq7zF2/NS0KgPz9ma9Bnl3UsB5+Q= Date: Sat, 28 Jul 2018 19:02:54 -0700 From: Jaegeuk Kim To: Chao Yu Cc: Chao Yu , linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH] f2fs: avoid race between zero_range and background GC Message-ID: <20180729020254.GH83620@jaegeuk-macbookpro.roam.corp.google.com> References: <20180726104536.114340-1-yuchao0@huawei.com> <20180727102916.GI16155@jaegeuk-macbookpro.roam.corp.google.com> <10d7814b-06d0-6751-ca56-85e7c8b92a27@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <10d7814b-06d0-6751-ca56-85e7c8b92a27@kernel.org> User-Agent: Mutt/1.8.2 (2017-04-18) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? > > > > >> 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