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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable 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 2B943C3A5A3 for ; Thu, 22 Aug 2019 15:00:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0727223401 for ; Thu, 22 Aug 2019 15:00:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389238AbfHVPAo (ORCPT ); Thu, 22 Aug 2019 11:00:44 -0400 Received: from mx2.suse.de ([195.135.220.15]:32828 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1731841AbfHVPAn (ORCPT ); Thu, 22 Aug 2019 11:00:43 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 2C68EAD7C; Thu, 22 Aug 2019 15:00:42 +0000 (UTC) Date: Thu, 22 Aug 2019 10:00:38 -0500 From: Goldwyn Rodrigues To: RITESH HARJANI Cc: linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org, hch@lst.de, darrick.wong@oracle.com, ruansy.fnst@cn.fujitsu.com Subject: Re: [PATCH 07/13] btrfs: basic direct read operation Message-ID: <20190822150038.rebfrmyk2m6ljzoo@fiona> References: <20190802220048.16142-1-rgoldwyn@suse.de> <20190802220048.16142-8-rgoldwyn@suse.de> <20190812123201.904205204F@d06av21.portsmouth.uk.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190812123201.904205204F@d06av21.portsmouth.uk.ibm.com> User-Agent: NeoMutt/20180716 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 18:02 12/08, RITESH HARJANI wrote: > > On 8/3/19 3:30 AM, Goldwyn Rodrigues wrote: > > From: Goldwyn Rodrigues > > > > Add btrfs_dio_iomap_ops for iomap.begin() function. In order to > > accomodate dio reads, add a new function btrfs_file_read_iter() > > which would call btrfs_dio_iomap_read() for DIO reads and > > fallback to generic_file_read_iter otherwise. > > > > Signed-off-by: Goldwyn Rodrigues > > --- > > fs/btrfs/ctree.h | 2 ++ > > fs/btrfs/file.c | 10 +++++++++- > > fs/btrfs/iomap.c | 20 ++++++++++++++++++++ > > 3 files changed, 31 insertions(+), 1 deletion(-) > > > > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h > > index 7a4ff524dc77..9eca2d576dd1 100644 > > --- a/fs/btrfs/ctree.h > > +++ b/fs/btrfs/ctree.h > > @@ -3247,7 +3247,9 @@ int btrfs_fdatawrite_range(struct inode *inode, loff_t start, loff_t end); > > loff_t btrfs_remap_file_range(struct file *file_in, loff_t pos_in, > > struct file *file_out, loff_t pos_out, > > loff_t len, unsigned int remap_flags); > > +/* iomap.c */ > > size_t btrfs_buffered_iomap_write(struct kiocb *iocb, struct iov_iter *from); > > +ssize_t btrfs_dio_iomap_read(struct kiocb *iocb, struct iov_iter *to); > > /* tree-defrag.c */ > > int btrfs_defrag_leaves(struct btrfs_trans_handle *trans, > > diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c > > index f7087e28ac08..997eb152a35a 100644 > > --- a/fs/btrfs/file.c > > +++ b/fs/btrfs/file.c > > @@ -2839,9 +2839,17 @@ static int btrfs_file_open(struct inode *inode, struct file *filp) > > return generic_file_open(inode, filp); > > } > > +static ssize_t btrfs_file_read_iter(struct kiocb *iocb, struct iov_iter *to) > > +{ > > + if (iocb->ki_flags & IOCB_DIRECT) > > + return btrfs_dio_iomap_read(iocb, to); > > No provision to fallback to bufferedIO read? Not sure from btrfs > perspective, > but earlier generic_file_read_iter may fall through to bufferedIO read say > in case where directIO could not be completed (returned 0 or less than the > requested read bytes). > Is it not required anymore in case of btrfs when we move to iomap > infrastructure, to still fall back to bufferedIO read? > Correct me if I am missing anything here. > No, you are right here. We should fallback to buffered reads in case of incomplete reads. Thanks for pointing it out. I will incorporate it in the next series. -- Goldwyn