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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,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 5AFC0C433E0 for ; Tue, 30 Jun 2020 20:56:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2B0762077D for ; Tue, 30 Jun 2020 20:56:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593550598; bh=SyHZ0Wo0kdMmXhB3HauNfjbw3rcUtpXH44TVKsmAjGU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=qoXDrgu7773q7m+Z9mrOUIEGXVCPBTpG5euUJq+cFin89jhe5xCzgUzfg3qacGIuk y0RMUWJlsdI0TgKaQqApG+d+WtIMbEUBi2k9UB3OVAYxh36PKE+u4yDnbei7i5JkWF uWKZUUTdCwNHW02eFmD3+BTnG1rciqg8gxhkCK7c= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727772AbgF3U4h (ORCPT ); Tue, 30 Jun 2020 16:56:37 -0400 Received: from mail.kernel.org ([198.145.29.99]:34910 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727045AbgF3U4g (ORCPT ); Tue, 30 Jun 2020 16:56:36 -0400 Received: from localhost (unknown [104.132.1.66]) (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 F32E22074D; Tue, 30 Jun 2020 20:56:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593550596; bh=SyHZ0Wo0kdMmXhB3HauNfjbw3rcUtpXH44TVKsmAjGU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=poiy4WZ9FK2/3ySDGGwENxJRuNeC9b7nRe7aM8hJoJXADIW3NillTF248reYglom8 0+ZuFTxbRjkkQjnv+ejTW5FXps36eGS/0zvgIlkiu8CDtqvPzWWSp08v4sfnRsVBJk InH2N6wr38soyV1bleIvfSlOAcFHCPDb6YcWj1aA= Date: Tue, 30 Jun 2020 13:56:35 -0700 From: Jaegeuk Kim To: Nathan Chancellor Cc: kernel-team@android.com, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Subject: Re: [f2fs-dev] [PATCH v3] f2fs: avoid readahead race condition Message-ID: <20200630205635.GB1396584@google.com> References: <20200624012148.180050-1-jaegeuk@kernel.org> <20200629150323.GA3293033@google.com> <20200629202720.GA230664@google.com> <20200630204348.GA2504307@ubuntu-s3-xlarge-x86> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200630204348.GA2504307@ubuntu-s3-xlarge-x86> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/30, Nathan Chancellor wrote: > On Mon, Jun 29, 2020 at 01:27:20PM -0700, Jaegeuk Kim wrote: > > If two readahead threads having same offset enter in readpages, every read > > IOs are split and issued to the disk which giving lower bandwidth. > > > > This patch tries to avoid redundant readahead calls. > > > > Signed-off-by: Jaegeuk Kim > > --- > > v3: > > - use READ|WRITE_ONCE > > v2: > > - add missing code to bypass read > > > > fs/f2fs/data.c | 18 ++++++++++++++++++ > > fs/f2fs/f2fs.h | 1 + > > fs/f2fs/super.c | 2 ++ > > 3 files changed, 21 insertions(+) > > > > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c > > index 995cf78b23c5e..360b4c9080d97 100644 > > --- a/fs/f2fs/data.c > > +++ b/fs/f2fs/data.c > > @@ -2296,6 +2296,7 @@ static int f2fs_mpage_readpages(struct inode *inode, > > unsigned nr_pages = rac ? readahead_count(rac) : 1; > > unsigned max_nr_pages = nr_pages; > > int ret = 0; > > + bool drop_ra = false; > > > > map.m_pblk = 0; > > map.m_lblk = 0; > > @@ -2306,10 +2307,24 @@ static int f2fs_mpage_readpages(struct inode *inode, > > map.m_seg_type = NO_CHECK_TYPE; > > map.m_may_create = false; > > > > + /* > > + * Two readahead threads for same address range can cause race condition > > + * which fragments sequential read IOs. So let's avoid each other. > > + */ > > + if (rac && readahead_count(rac)) { > > + if (READ_ONCE(F2FS_I(inode)->ra_offset) == readahead_index(rac)) > > + drop_ra = true; > > + else > > + WRITE_ONCE(F2FS_I(inode)->ra_offset, > > + readahead_index(rac)); > > + } > > + > > for (; nr_pages; nr_pages--) { > > if (rac) { > > page = readahead_page(rac); > > prefetchw(&page->flags); > > + if (drop_ra) > > + goto next_page; > > When CONFIG_F2FS_FS_COMPRESSION is not set (i.e. x86_64 defconfig + > CONFIG_F2FS_FS=y): > > $ make -skj"$(nproc)" O=out distclean defconfig fs/f2fs/data.o > ../fs/f2fs/data.c: In function ‘f2fs_mpage_readpages’: > ../fs/f2fs/data.c:2327:5: error: label ‘next_page’ used but not defined > 2327 | goto next_page; > | ^~~~ > ... Thanks. I pushed the fix for -next. https://lore.kernel.org/linux-f2fs-devel/1be18397-7fc6-703e-121b-e210e101357f@infradead.org/T/#t Thanks, > > Cheers, > Nathan > > > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel