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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 DA621C433E0 for ; Mon, 22 Mar 2021 17:14:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B0B6C6199E for ; Mon, 22 Mar 2021 17:14:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232125AbhCVROR (ORCPT ); Mon, 22 Mar 2021 13:14:17 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:29598 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232123AbhCVROB (ORCPT ); Mon, 22 Mar 2021 13:14:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616433240; 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: in-reply-to:in-reply-to:references:references; bh=aMbmUNAFvNWl2qhZsFpoWOGxDUGbmddTSEhEjr5Mf7I=; b=i7ltGioUkJK5oqs5PbDLKbngj5QBxFWbnk27M8l/jiNMs2ep9ZTPlVJH6Oel2pfkDSDi7l 1OUFtBA8SM4LfDtfmyn/PVv7lW9FW0UYtCmq71Xy8717gAVSLdedMxene+gsdXNnCyT+wY mdMYbua0Mlc+puil5Ks9L1io1vGU3kg= 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-537-03ysOJ7_MVCEbA-orqBIWQ-1; Mon, 22 Mar 2021 13:13:56 -0400 X-MC-Unique: 03ysOJ7_MVCEbA-orqBIWQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 803B0801817; Mon, 22 Mar 2021 17:13:54 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-112-58.rdu2.redhat.com [10.10.112.58]) by smtp.corp.redhat.com (Postfix) with ESMTP id A8BF860C0F; Mon, 22 Mar 2021 17:13:48 +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 From: David Howells In-Reply-To: <20210321014202.GF3420@casper.infradead.org> References: <20210321014202.GF3420@casper.infradead.org> <161539526152.286939.8589700175877370401.stgit@warthog.procyon.org.uk> <161539537375.286939.16642940088716990995.stgit@warthog.procyon.org.uk> To: Matthew Wilcox Cc: dhowells@redhat.com, Trond Myklebust , Anna Schumaker , Steve French , Dominique Martinet , Jeff Layton , 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, David Wysochanski , Alexander Viro , linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 08/28] netfs: Provide readahead and readpage netfs helpers MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <2285031.1616433227.1@warthog.procyon.org.uk> Date: Mon, 22 Mar 2021 17:13:47 +0000 Message-ID: <2285032.1616433227@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org Matthew Wilcox wrote: > > + while ((page = readahead_page(ractl))) > > + put_page(page); > > You don't need this pair of lines (unless I'm missing something). > read_pages() in mm/readahead.c puts the reference and unlocks any > pages which are not read by the readahead op. Indeed, I think doing > this is buggy because you don't unlock the page. Actually, I do need them. The pages haven't been removed from the ractl at this point so just returning would cause them all to be unlocked prematurely. I don't pass the ractl to the filesystem or the cache because I may be calling them for partial pages, I may be issuing multiple ops sequentially on a page and the ractl may have ceased to exist by the time I issue an op. The unlocking is done by netfs_rreq_unlock(), even for pages that didn't get read. I've added a comment to this effect. David