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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 0C31EC3404D for ; Wed, 19 Feb 2020 00:13:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D96C724656 for ; Wed, 19 Feb 2020 00:13:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="LZUXi8JQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726795AbgBSANE (ORCPT ); Tue, 18 Feb 2020 19:13:04 -0500 Received: from hqnvemgate25.nvidia.com ([216.228.121.64]:18092 "EHLO hqnvemgate25.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726415AbgBSANE (ORCPT ); Tue, 18 Feb 2020 19:13:04 -0500 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate25.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Tue, 18 Feb 2020 16:12:27 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Tue, 18 Feb 2020 16:12:59 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Tue, 18 Feb 2020 16:12:59 -0800 Received: from [10.110.48.28] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Wed, 19 Feb 2020 00:12:59 +0000 Subject: Re: [PATCH v6 08/19] mm: Add readahead address space operation To: Matthew Wilcox , CC: , , , , , , , , References: <20200217184613.19668-1-willy@infradead.org> <20200217184613.19668-14-willy@infradead.org> X-Nvconfidentiality: public From: John Hubbard Message-ID: Date: Tue, 18 Feb 2020 16:12:59 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200217184613.19668-14-willy@infradead.org> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1582071148; bh=XYyqV3UUSvdocn4sI3PrA/ovYe/qDo2rL7zzBYFMHHQ=; h=X-PGP-Universal:Subject:To:CC:References:X-Nvconfidentiality:From: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=LZUXi8JQOUsxM4MhkbKZoN+us77X32agHHEERvyhJFQIOA1HQvZOoIGniinVZGnwn pZ2VcWEgxoh8iz45kjTzfdIeohxKJWjgA24H8/wDDP9a0/3dFwa4tJpxgpapBn1SP0 6/Wfm0vT02ejD0TSvYWlZdshSpOysFqkccwchWZ9fxvkGg5guUZEdfBxSiI/mMsYEp FgymXJQ1zao4g21+WHoUfPhqNPoyrsbrhqpLdsNEHa/aoseWOTMxw940mhXVsqG1Ib OHqwlrvjGtIuPOEVEUVsVzgkbxTMVawyEuM/R5wrTMKOe7ZmOR2cspeFnXDRI9uYLT teYbgBQPqd3OA== Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On 2/17/20 10:45 AM, Matthew Wilcox wrote: > From: "Matthew Wilcox (Oracle)" > > This replaces ->readpages with a saner interface: > - Return void instead of an ignored error code. > - Pages are already in the page cache when ->readahead is called. > - Implementation looks up the pages in the page cache instead of > having them passed in a linked list. > > Signed-off-by: Matthew Wilcox (Oracle) > --- > Documentation/filesystems/locking.rst | 6 +++++- > Documentation/filesystems/vfs.rst | 13 +++++++++++++ > include/linux/fs.h | 2 ++ > include/linux/pagemap.h | 18 ++++++++++++++++++ > mm/readahead.c | 8 +++++++- > 5 files changed, 45 insertions(+), 2 deletions(-) > Looks nice, Reviewed-by: John Hubbard thanks, -- John Hubbard NVIDIA > diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst > index 5057e4d9dcd1..0ebc4491025a 100644 > --- a/Documentation/filesystems/locking.rst > +++ b/Documentation/filesystems/locking.rst > @@ -239,6 +239,7 @@ prototypes:: > int (*readpage)(struct file *, struct page *); > int (*writepages)(struct address_space *, struct writeback_control *); > int (*set_page_dirty)(struct page *page); > + void (*readahead)(struct readahead_control *); > int (*readpages)(struct file *filp, struct address_space *mapping, > struct list_head *pages, unsigned nr_pages); > int (*write_begin)(struct file *, struct address_space *mapping, > @@ -271,7 +272,8 @@ writepage: yes, unlocks (see below) > readpage: yes, unlocks > writepages: > set_page_dirty no > -readpages: > +readahead: yes, unlocks > +readpages: no > write_begin: locks the page exclusive > write_end: yes, unlocks exclusive > bmap: > @@ -295,6 +297,8 @@ the request handler (/dev/loop). > ->readpage() unlocks the page, either synchronously or via I/O > completion. > > +->readahead() unlocks the pages like ->readpage(). > + > ->readpages() populates the pagecache with the passed pages and starts > I/O against them. They come unlocked upon I/O completion. > > diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst > index 7d4d09dd5e6d..81ab30fbe45c 100644 > --- a/Documentation/filesystems/vfs.rst > +++ b/Documentation/filesystems/vfs.rst > @@ -706,6 +706,7 @@ cache in your filesystem. The following members are defined: > int (*readpage)(struct file *, struct page *); > int (*writepages)(struct address_space *, struct writeback_control *); > int (*set_page_dirty)(struct page *page); > + void (*readahead)(struct readahead_control *); > int (*readpages)(struct file *filp, struct address_space *mapping, > struct list_head *pages, unsigned nr_pages); > int (*write_begin)(struct file *, struct address_space *mapping, > @@ -781,12 +782,24 @@ cache in your filesystem. The following members are defined: > If defined, it should set the PageDirty flag, and the > PAGECACHE_TAG_DIRTY tag in the radix tree. > > +``readahead`` > + Called by the VM to read pages associated with the address_space > + object. The pages are consecutive in the page cache and are > + locked. The implementation should decrement the page refcount > + after starting I/O on each page. Usually the page will be > + unlocked by the I/O completion handler. If the function does > + not attempt I/O on some pages, the caller will decrement the page > + refcount and unlock the pages for you. Set PageUptodate if the > + I/O completes successfully. Setting PageError on any page will > + be ignored; simply unlock the page if an I/O error occurs. > + > ``readpages`` > called by the VM to read pages associated with the address_space > object. This is essentially just a vector version of readpage. > Instead of just one page, several pages are requested. > readpages is only used for read-ahead, so read errors are > ignored. If anything goes wrong, feel free to give up. > + This interface is deprecated; implement readahead instead. > > ``write_begin`` > Called by the generic buffered write code to ask the filesystem > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 3cd4fe6b845e..d4e2d2964346 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -292,6 +292,7 @@ enum positive_aop_returns { > struct page; > struct address_space; > struct writeback_control; > +struct readahead_control; > > /* > * Write life time hint values. > @@ -375,6 +376,7 @@ struct address_space_operations { > */ > int (*readpages)(struct file *filp, struct address_space *mapping, > struct list_head *pages, unsigned nr_pages); > + void (*readahead)(struct readahead_control *); > > int (*write_begin)(struct file *, struct address_space *mapping, > loff_t pos, unsigned len, unsigned flags, > diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h > index 3613154e79e4..bd4291f78f41 100644 > --- a/include/linux/pagemap.h > +++ b/include/linux/pagemap.h > @@ -665,6 +665,24 @@ static inline void readahead_next(struct readahead_control *rac) > #define readahead_for_each(rac, page) \ > for (; (page = readahead_page(rac)); readahead_next(rac)) > > +/* The byte offset into the file of this readahead block */ > +static inline loff_t readahead_offset(struct readahead_control *rac) > +{ > + return (loff_t)rac->_start * PAGE_SIZE; > +} > + > +/* The number of bytes in this readahead block */ > +static inline loff_t readahead_length(struct readahead_control *rac) > +{ > + return (loff_t)rac->_nr_pages * PAGE_SIZE; > +} > + > +/* The index of the first page in this readahead block */ > +static inline unsigned int readahead_index(struct readahead_control *rac) > +{ > + return rac->_start; > +} > + > /* The number of pages in this readahead block */ > static inline unsigned int readahead_count(struct readahead_control *rac) > { > diff --git a/mm/readahead.c b/mm/readahead.c > index 9e430daae42f..975ff5e387be 100644 > --- a/mm/readahead.c > +++ b/mm/readahead.c > @@ -121,7 +121,13 @@ static void read_pages(struct readahead_control *rac, struct list_head *pages) > > blk_start_plug(&plug); > > - if (aops->readpages) { > + if (aops->readahead) { > + aops->readahead(rac); > + readahead_for_each(rac, page) { > + unlock_page(page); > + put_page(page); > + } > + } else if (aops->readpages) { > aops->readpages(rac->file, rac->mapping, pages, > readahead_count(rac)); > /* Clean up the remaining pages */ >