From patchwork Sat Feb 1 15:12:32 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Wilcox X-Patchwork-Id: 11361077 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 775C414B4 for ; Sat, 1 Feb 2020 15:12:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 55F6820842 for ; Sat, 1 Feb 2020 15:12:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="bY3NBrXn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727265AbgBAPMv (ORCPT ); Sat, 1 Feb 2020 10:12:51 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:51880 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727225AbgBAPMs (ORCPT ); Sat, 1 Feb 2020 10:12:48 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From :Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=Ml5Puu4JmLRdzMhiiCOiBo4ACbPsQdjTb+QSPxS+DKY=; b=bY3NBrXng43eEHaP4qFkNBHkjA /0ai0QxQPvj+vzTnehD7kfdwvHZ8vzjptHG3nMCtmSDzhJPLlrrRvHwMG04vHV9fd/CCJRTd7hZ9S kCY6iKxXzzldIpqfDcbhn1eEv9lpm3OwGdFjku0KJeD/QhITkP89Q8r/3MLB+25BxQPdL5yjJPCI/ zaoC9Cl+tOymw4aTP+dhrGrhEN9KAUrBXzsBIHlqEM/UfvzLlZxLPkERj8Ov2t+ljIWtVaj85jqMP h352PTKYgXTRiVZYfWwYCWlL9sM65Px7gR4w2uvH7jwuclAa5kmfsGcMYSDK+NcJWFvdA8OCVg7ot FV+G0YLQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1ixuRu-0006HT-5R; Sat, 01 Feb 2020 15:12:42 +0000 From: Matthew Wilcox To: linux-fsdevel@vger.kernel.org Cc: "Matthew Wilcox (Oracle)" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, cluster-devel@redhat.com, ocfs2-devel@oss.oracle.com Subject: [PATCH v4 04/12] mm: Add readahead address space operation Date: Sat, 1 Feb 2020 07:12:32 -0800 Message-Id: <20200201151240.24082-5-willy@infradead.org> X-Mailer: git-send-email 2.21.1 In-Reply-To: <20200201151240.24082-1-willy@infradead.org> References: <20200201151240.24082-1-willy@infradead.org> MIME-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org From: "Matthew Wilcox (Oracle)" This replaces ->readpages with a saner interface: - Return the number of pages not read 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) Cc: linux-btrfs@vger.kernel.org Cc: linux-erofs@lists.ozlabs.org Cc: linux-ext4@vger.kernel.org Cc: linux-f2fs-devel@lists.sourceforge.net Cc: linux-xfs@vger.kernel.org Cc: cluster-devel@redhat.com Cc: ocfs2-devel@oss.oracle.com --- Documentation/filesystems/locking.rst | 7 ++++++- Documentation/filesystems/vfs.rst | 14 ++++++++++++++ include/linux/fs.h | 2 ++ include/linux/pagemap.h | 12 ++++++++++++ mm/readahead.c | 13 ++++++++++++- 5 files changed, 46 insertions(+), 2 deletions(-) diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index 5057e4d9dcd1..3d10729caf44 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -239,6 +239,8 @@ prototypes:: int (*readpage)(struct file *, struct page *); int (*writepages)(struct address_space *, struct writeback_control *); int (*set_page_dirty)(struct page *page); + unsigned (*readahead)(struct file *, struct address_space *, + pgoff_t start, unsigned nr_pages); 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 +273,8 @@ 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 +298,8 @@ 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..c2bc345f2169 100644 --- a/Documentation/filesystems/vfs.rst +++ b/Documentation/filesystems/vfs.rst @@ -706,6 +706,8 @@ 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); + unsigned (*readahead)(struct file *filp, struct address_space *mapping, + pgoff_t start, unsigned nr_pages); 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, @@ -781,6 +783,18 @@ 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 attempting 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, return the number + of pages which were not read so the caller can 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. diff --git a/include/linux/fs.h b/include/linux/fs.h index 41584f50af0d..3bfc142e7d10 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -375,6 +375,8 @@ struct address_space_operations { */ int (*readpages)(struct file *filp, struct address_space *mapping, struct list_head *pages, unsigned nr_pages); + unsigned (*readahead)(struct file *, struct address_space *, + pgoff_t start, unsigned nr_pages); 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 ccb14b6a16b5..a2cf007826f2 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -630,6 +630,18 @@ static inline int add_to_page_cache(struct page *page, return error; } +/* + * Only call this from a ->readahead implementation. + */ +static inline +struct page *readahead_page(struct address_space *mapping, pgoff_t index) +{ + struct page *page = xa_load(&mapping->i_pages, index); + VM_BUG_ON_PAGE(!PageLocked(page), page); + + return page; +} + static inline unsigned long dir_pages(struct inode *inode) { return (unsigned long)(inode->i_size + PAGE_SIZE - 1) >> diff --git a/mm/readahead.c b/mm/readahead.c index 7daef0038b14..b2ed0baf3a5d 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -121,7 +121,18 @@ static void read_pages(struct address_space *mapping, struct file *filp, blk_start_plug(&plug); - if (mapping->a_ops->readpages) { + if (mapping->a_ops->readahead) { + unsigned left = mapping->a_ops->readahead(filp, mapping, + start, nr_pages); + + while (left) { + struct page *page = readahead_page(mapping, + start + nr_pages - left); + unlock_page(page); + put_page(page); + left--; + } + } else if (mapping->a_ops->readpages) { mapping->a_ops->readpages(filp, mapping, pages, nr_pages); /* Clean up the remaining pages */ put_pages_list(pages);