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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 9BC24C3A5A1 for ; Wed, 28 Aug 2019 22:32:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7404C2339E for ; Wed, 28 Aug 2019 22:32:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727108AbfH1WcY (ORCPT ); Wed, 28 Aug 2019 18:32:24 -0400 Received: from mail105.syd.optusnet.com.au ([211.29.132.249]:54966 "EHLO mail105.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726658AbfH1WcY (ORCPT ); Wed, 28 Aug 2019 18:32:24 -0400 Received: from dread.disaster.area (pa49-181-255-194.pa.nsw.optusnet.com.au [49.181.255.194]) by mail105.syd.optusnet.com.au (Postfix) with ESMTPS id 98ED4361338; Thu, 29 Aug 2019 08:32:20 +1000 (AEST) Received: from dave by dread.disaster.area with local (Exim 4.92) (envelope-from ) id 1i36UE-00057N-WE; Thu, 29 Aug 2019 08:32:19 +1000 Date: Thu, 29 Aug 2019 08:32:18 +1000 From: Dave Chinner To: Jan Kara Cc: Matthew Bobrowski , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, tytso@mit.edu, riteshh@linux.ibm.com Subject: Re: [PATCH 4/5] ext4: introduce direct IO write code path using iomap infrastructure Message-ID: <20190828223218.GZ7777@dread.disaster.area> References: <581c3a2da89991e7ce5862d93dcfb23e1dc8ddc8.1565609891.git.mbobrowski@mbobrowski.org> <20190828202619.GG22343@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190828202619.GG22343@quack2.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.2 cv=D+Q3ErZj c=1 sm=1 tr=0 a=YO9NNpcXwc8z/SaoS+iAiA==:117 a=YO9NNpcXwc8z/SaoS+iAiA==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=FmdZ9Uzk2mMA:10 a=4ERQYXhnAAAA:8 a=7-415B0cAAAA:8 a=YRs46oH6ve-dZsFn3eoA:9 a=CjuIK1q_8ugA:10 a=HrUHXJcpxbsINVJ6ux1W:22 a=biEYGPWJfzWAr4FL6Ov7:22 Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Wed, Aug 28, 2019 at 10:26:19PM +0200, Jan Kara wrote: > On Mon 12-08-19 22:53:26, Matthew Bobrowski wrote: > > This patch introduces a new direct IO write code path implementation > > that makes use of the iomap infrastructure. > > > > All direct IO write operations are now passed from the ->write_iter() callback > > to the new function ext4_dio_write_iter(). This function is responsible for > > calling into iomap infrastructure via iomap_dio_rw(). Snippets of the direct > > IO code from within ext4_file_write_iter(), such as checking whether the IO > > request is unaligned asynchronous IO, or whether it will ber overwriting > > allocated and initialized blocks has been moved out and into > > ext4_dio_write_iter(). > > > > The block mapping flags that are passed to ext4_map_blocks() from within > > ext4_dio_get_block() and friends have effectively been taken out and > > introduced within the ext4_iomap_begin(). If ext4_map_blocks() happens to have > > instantiated blocks beyond the i_size, then we attempt to place the inode onto > > the orphan list. Despite being able to perform i_size extension checking > > earlier on in the direct IO code path, it makes most sense to perform this bit > > post successful block allocation. > > > > The ->end_io() callback ext4_dio_write_end_io() is responsible for removing > > the inode from the orphan list and determining if we should truncate a failed > > write in the case of an error. We also convert a range of unwritten extents to > > written if IOMAP_DIO_UNWRITTEN is set and perform the necessary > > i_size/i_disksize extension if the iocb->ki_pos + dio->size > i_size_read(inode). > > > > In the instance of a short write, we fallback to buffered IO and complete > > whatever is left the 'iter'. Any blocks that may have been allocated in > > preparation for direct IO will be reused by buffered IO, so there's no issue > > with leaving allocated blocks beyond EOF. > > > > Signed-off-by: Matthew Bobrowski > > --- > > fs/ext4/file.c | 227 ++++++++++++++++++++++++++++++++++++++++---------------- > > fs/ext4/inode.c | 42 +++++++++-- > > 2 files changed, 199 insertions(+), 70 deletions(-) > > Overall this is very nice. Some smaller comments below. > > > @@ -235,6 +244,34 @@ static ssize_t ext4_write_checks(struct kiocb *iocb, struct iov_iter *from) > > return iov_iter_count(from); > > } > > > > +static ssize_t ext4_buffered_write_iter(struct kiocb *iocb, > > + struct iov_iter *from) > > +{ > > + ssize_t ret; > > + struct inode *inode = file_inode(iocb->ki_filp); > > + > > + if (!inode_trylock(inode)) { > > + if (iocb->ki_flags & IOCB_NOWAIT) > > + return -EOPNOTSUPP; > > + inode_lock(inode); > > + } > > Currently there's no support for IOCB_NOWAIT for buffered IO so you can > replace this with "inode_lock(inode)". IOCB_NOWAIT is supported for buffered reads. It is not supported on buffered writes (as yet), so this should return EOPNOTSUPP if IOCB_NOWAIT is set, regardless of whether the lock can be grabbed or not. Cheers, Dave. -- Dave Chinner david@fromorbit.com