Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 69159C433EF for ; Mon, 6 Dec 2021 11:42:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240733AbhLFLpz (ORCPT ); Mon, 6 Dec 2021 06:45:55 -0500 Received: from out30-42.freemail.mail.aliyun.com ([115.124.30.42]:54919 "EHLO out30-42.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237397AbhLFLpz (ORCPT ); Mon, 6 Dec 2021 06:45:55 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R271e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04395;MF=jefflexu@linux.alibaba.com;NM=1;PH=DS;RN=18;SR=0;TI=SMTPD_---0UzcMKwq_1638790938; Received: from 30.225.24.25(mailfrom:jefflexu@linux.alibaba.com fp:SMTPD_---0UzcMKwq_1638790938) by smtp.aliyun-inc.com(127.0.0.1); Mon, 06 Dec 2021 19:42:19 +0800 Message-ID: Date: Mon, 6 Dec 2021 19:42:18 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.3.0 Subject: Re: [PATCH 24/64] netfs: Pass more information on how to deal with a hole in the cache Content-Language: en-US To: David Howells , linux-cachefs@redhat.com Cc: Trond Myklebust , Anna Schumaker , Steve French , Dominique Martinet , Jeff Layton , Matthew Wilcox , Alexander Viro , Omar Sandoval , Linus Torvalds , linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs-developer@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org References: <163819575444.215744.318477214576928110.stgit@warthog.procyon.org.uk> <163819612321.215744.9738308885948264476.stgit@warthog.procyon.org.uk> From: JeffleXu In-Reply-To: <163819612321.215744.9738308885948264476.stgit@warthog.procyon.org.uk> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On 11/29/21 10:28 PM, David Howells wrote: > Pass more information to the cache on how to deal with a hole if it > encounters one when trying to read from the cache. Three options are > provided: > > (1) NETFS_READ_HOLE_IGNORE. Read the hole along with the data, assuming > it to be a punched-out extent by the backing filesystem. > > (2) NETFS_READ_HOLE_CLEAR. If there's a hole, erase the requested region > of the cache and clear the read buffer. > > (3) NETFS_READ_HOLE_FAIL. Fail the read if a hole is detected. > > Signed-off-by: David Howells > cc: linux-cachefs@redhat.com > --- > > fs/netfs/read_helper.c | 8 ++++---- > include/linux/netfs.h | 11 ++++++++++- > 2 files changed, 14 insertions(+), 5 deletions(-) > > diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c > index 7dc79fa8a1f3..08df413efdf3 100644 > --- a/fs/netfs/read_helper.c > +++ b/fs/netfs/read_helper.c > @@ -170,7 +170,7 @@ static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error > */ > static void netfs_read_from_cache(struct netfs_read_request *rreq, > struct netfs_read_subrequest *subreq, > - bool seek_data) > + enum netfs_read_from_hole read_hole) > { > struct netfs_cache_resources *cres = &rreq->cache_resources; > struct iov_iter iter; > @@ -180,7 +180,7 @@ static void netfs_read_from_cache(struct netfs_read_request *rreq, > subreq->start + subreq->transferred, > subreq->len - subreq->transferred); > > - cres->ops->read(cres, subreq->start, &iter, seek_data, > + cres->ops->read(cres, subreq->start, &iter, read_hole, > netfs_cache_read_terminated, subreq); > } > > @@ -466,7 +466,7 @@ static void netfs_rreq_short_read(struct netfs_read_request *rreq, > netfs_get_read_subrequest(subreq); > atomic_inc(&rreq->nr_rd_ops); > if (subreq->source == NETFS_READ_FROM_CACHE) > - netfs_read_from_cache(rreq, subreq, true); > + netfs_read_from_cache(rreq, subreq, NETFS_READ_HOLE_CLEAR); Hi I'm not sure why NETFS_READ_HOLE_CLEAR style should be used in 'short read' case. Besides, ``` static void netfs_read_from_cache(struct netfs_read_request *rreq, struct netfs_read_subrequest *subreq, enum netfs_read_from_hole read_hole) { struct netfs_cache_resources *cres = &rreq->cache_resources; struct iov_iter iter; netfs_stat(&netfs_n_rh_read); iov_iter_xarray(&iter, READ, &rreq->mapping->i_pages, subreq->start + subreq->transferred, subreq->len - subreq->transferred); cres->ops->read(cres, subreq->start, &iter, read_hole, netfs_cache_read_terminated, subreq); } ``` I'm not sure why 'subreq->start' is not incremented with 'subreq->transferred' when calling cres->ops->read() in 'short read' case. > else > netfs_read_from_server(rreq, subreq); > } > @@ -794,7 +794,7 @@ static bool netfs_rreq_submit_slice(struct netfs_read_request *rreq, > netfs_read_from_server(rreq, subreq); > break; > case NETFS_READ_FROM_CACHE: > - netfs_read_from_cache(rreq, subreq, false); > + netfs_read_from_cache(rreq, subreq, NETFS_READ_HOLE_IGNORE); > break; > default: > BUG(); > diff --git a/include/linux/netfs.h b/include/linux/netfs.h > index 5a46fde65759..b46c39d98bbd 100644 > --- a/include/linux/netfs.h > +++ b/include/linux/netfs.h > @@ -196,6 +196,15 @@ struct netfs_read_request_ops { > void (*cleanup)(struct address_space *mapping, void *netfs_priv); > }; > > +/* > + * How to handle reading from a hole. > + */ > +enum netfs_read_from_hole { > + NETFS_READ_HOLE_IGNORE, > + NETFS_READ_HOLE_CLEAR, > + NETFS_READ_HOLE_FAIL, > +}; > + > /* > * Table of operations for access to a cache. This is obtained by > * rreq->ops->begin_cache_operation(). > @@ -208,7 +217,7 @@ struct netfs_cache_ops { > int (*read)(struct netfs_cache_resources *cres, > loff_t start_pos, > struct iov_iter *iter, > - bool seek_data, > + enum netfs_read_from_hole read_hole, > netfs_io_terminated_t term_func, > void *term_func_priv); > > -- Thanks, Jeffle