From patchwork Mon Feb 15 15:44:52 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 383364 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=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS 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 56AA2C433E0 for ; Mon, 15 Feb 2021 16:22:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2E10064DF0 for ; Mon, 15 Feb 2021 16:22:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232116AbhBOQVJ (ORCPT ); Mon, 15 Feb 2021 11:21:09 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:48443 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231656AbhBOPq2 (ORCPT ); Mon, 15 Feb 2021 10:46:28 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613403900; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=I0qlBdxKxClBfihp/lgdjTIf+rONu/U7ZON8p6l2s80=; b=E9spuKvgvOFhnyMiJ6rtlpGUjcShzcArFHvFka6j/8twiMUz+vAnRd5mxdUJZjnWASzbjU dIKhxRN9XDQRDK5P68tOd3/t+ySlcXNPrFgghze4Je1OzV2Db3WkQQrGHce0ohf6WpteIn CJ+7EL/+zIu99FcQWBK7zFcK1OI8m9Q= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-463-XD3HjPbrO-a3_Rft59zEag-1; Mon, 15 Feb 2021 10:44:58 -0500 X-MC-Unique: XD3HjPbrO-a3_Rft59zEag-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 479DD801962; Mon, 15 Feb 2021 15:44:56 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-119-68.rdu2.redhat.com [10.10.119.68]) by smtp.corp.redhat.com (Postfix) with ESMTP id CF03C608DB; Mon, 15 Feb 2021 15:44:52 +0000 (UTC) Organization: Red Hat UK Ltd. 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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 03/33] mm: Implement readahead_control pageset expansion From: David Howells To: Trond Myklebust , Anna Schumaker , Steve French , Dominique Martinet Cc: "Matthew Wilcox (Oracle)" , "Matthew Wilcox (Oracle)" , Alexander Viro , Christoph Hellwig , linux-mm@kvack.org, linux-cachefs@redhat.com, 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, dhowells@redhat.com, Jeff Layton , David Wysochanski , "Matthew Wilcox (Oracle)" , Alexander Viro , linux-cachefs@redhat.com, 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 Date: Mon, 15 Feb 2021 15:44:52 +0000 Message-ID: <161340389201.1303470.14353807284546854878.stgit@warthog.procyon.org.uk> In-Reply-To: <161340385320.1303470.2392622971006879777.stgit@warthog.procyon.org.uk> References: <161340385320.1303470.2392622971006879777.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org Provide a function, readahead_expand(), that expands the set of pages specified by a readahead_control object to encompass a revised area with a proposed size and length. The proposed area must include all of the old area and may be expanded yet more by this function so that the edges align on (transparent huge) page boundaries as allocated. The expansion will be cut short if a page already exists in either of the areas being expanded into. Note that any expansion made in such a case is not rolled back. This will be used by fscache so that reads can be expanded to cache granule boundaries, thereby allowing whole granules to be stored in the cache, but there are other potential users also. Suggested-by: Matthew Wilcox (Oracle) Signed-off-by: David Howells cc: Matthew Wilcox (Oracle) cc: Alexander Viro cc: Christoph Hellwig cc: linux-mm@kvack.org cc: linux-cachefs@redhat.com cc: linux-afs@lists.infradead.org cc: linux-nfs@vger.kernel.org cc: linux-cifs@vger.kernel.org cc: ceph-devel@vger.kernel.org cc: v9fs-developer@lists.sourceforge.net cc: linux-fsdevel@vger.kernel.org --- include/linux/pagemap.h | 2 + mm/readahead.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 72 insertions(+) diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 365a28ece763..d2786607d297 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -761,6 +761,8 @@ extern void __delete_from_page_cache(struct page *page, void *shadow); int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask); void delete_from_page_cache_batch(struct address_space *mapping, struct pagevec *pvec); +void readahead_expand(struct readahead_control *ractl, + loff_t new_start, size_t new_len); /* * Like add_to_page_cache_locked, but used to add newly allocated pages: diff --git a/mm/readahead.c b/mm/readahead.c index c5b0457415be..4446dada0bc2 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -638,3 +638,73 @@ SYSCALL_DEFINE3(readahead, int, fd, loff_t, offset, size_t, count) { return ksys_readahead(fd, offset, count); } + +/** + * readahead_expand - Expand a readahead request + * @ractl: The request to be expanded + * @new_start: The revised start + * @new_len: The revised size of the request + * + * Attempt to expand a readahead request outwards from the current size to the + * specified size by inserting locked pages before and after the current window + * to increase the size to the new window. This may involve the insertion of + * THPs, in which case the window may get expanded even beyond what was + * requested. + * + * The algorithm will stop if it encounters a conflicting page already in the + * pagecache and leave a smaller expansion than requested. + * + * The caller must check for this by examining the revised @ractl object for a + * different expansion than was requested. + */ +void readahead_expand(struct readahead_control *ractl, + loff_t new_start, size_t new_len) +{ + struct address_space *mapping = ractl->mapping; + pgoff_t new_index, new_nr_pages; + gfp_t gfp_mask = readahead_gfp_mask(mapping); + + new_index = new_start / PAGE_SIZE; + + /* Expand the leading edge downwards */ + while (ractl->_index > new_index) { + unsigned long index = ractl->_index - 1; + struct page *page = xa_load(&mapping->i_pages, index); + + if (page && !xa_is_value(page)) + return; /* Page apparently present */ + + page = __page_cache_alloc(gfp_mask); + if (!page) + return; + if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) { + put_page(page); + return; + } + + ractl->_nr_pages++; + ractl->_index = page->index; + } + + new_len += new_start - readahead_pos(ractl); + new_nr_pages = DIV_ROUND_UP(new_len, PAGE_SIZE); + + /* Expand the trailing edge upwards */ + while (ractl->_nr_pages < new_nr_pages) { + unsigned long index = ractl->_index + ractl->_nr_pages; + struct page *page = xa_load(&mapping->i_pages, index); + + if (page && !xa_is_value(page)) + return; /* Page apparently present */ + + page = __page_cache_alloc(gfp_mask); + if (!page) + return; + if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) { + put_page(page); + return; + } + ractl->_nr_pages++; + } +} +EXPORT_SYMBOL(readahead_expand);