From patchwork Fri Nov 20 15:06:53 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 11920697 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 68680C63777 for ; Fri, 20 Nov 2020 15:07:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1492022226 for ; Fri, 20 Nov 2020 15:07:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="gfXGrmd7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728438AbgKTPHH (ORCPT ); Fri, 20 Nov 2020 10:07:07 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:54499 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728238AbgKTPHG (ORCPT ); Fri, 20 Nov 2020 10:07:06 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1605884825; 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=OASbtfxyD6eIUPjL3PNzYRIfoGBOulxlBVzyzkIasn0=; b=gfXGrmd7wd463+ERjAiLwGn9UlcFup+6K8HcLAu4wZN7ix7BNIB1mZLzVLsxTY4JSBdL5r 8nyp/okgP85N1Tc1GHQQyPuPApzVvijPDBhSFoaJaUSjqrP2SSjkETy/uvjp/18FhLh2kC C3N4eTnWZRzTBTMzooWcknuK5WtC+ro= 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-160-mRGFeT5KP024Srat-9T2_g-1; Fri, 20 Nov 2020 10:07:02 -0500 X-MC-Unique: mRGFeT5KP024Srat-9T2_g-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 346E31DDE6; Fri, 20 Nov 2020 15:07:00 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-112-246.rdu2.redhat.com [10.10.112.246]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6356F19C71; Fri, 20 Nov 2020 15:06:54 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 Subject: [RFC PATCH 20/76] mm: Stop generic_file_buffered_read() from grabbing a superfluous page From: David Howells To: Trond Myklebust , Anna Schumaker , Steve French , Dominique Martinet Cc: dhowells@redhat.com, Jeff Layton , Matthew Wilcox , 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: Fri, 20 Nov 2020 15:06:53 +0000 Message-ID: <160588481358.3465195.16552616179674485179.stgit@warthog.procyon.org.uk> In-Reply-To: <160588455242.3465195.3214733858273019178.stgit@warthog.procyon.org.uk> References: <160588455242.3465195.3214733858273019178.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org Under some circumstances, generic_file_buffered_read() will allocate sufficient pages to read to the end of the file, call readahead/readpages on them and copy the data over - and then it will allocate another page at the EOF and call readpage on that and then ignore it. This is unnecessary and a waste of time and resources. Catch the overallocation in the "no_cached_page:" part and prevent it from happening. Signed-off-by: David Howells --- mm/filemap.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/filemap.c b/mm/filemap.c index cfb753955e36..5a63aa1dd71e 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2447,6 +2447,8 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb, * Ok, it wasn't cached, so we need to create a new * page.. */ + if ((index << PAGE_SHIFT) >= i_size_read(inode)) + goto out; page = page_cache_alloc(mapping); if (!page) { error = -ENOMEM;