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=-12.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 58B2AC4361A for ; Thu, 3 Dec 2020 15:00:21 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B6B37206D6 for ; Thu, 3 Dec 2020 15:00:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B6B37206D6 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.43716.78553 (Exim 4.92) (envelope-from ) id 1kkq5N-00073M-Sf; Thu, 03 Dec 2020 14:59:57 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 43716.78553; Thu, 03 Dec 2020 14:59:57 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kkq5N-00073F-PK; Thu, 03 Dec 2020 14:59:57 +0000 Received: by outflank-mailman (input) for mailman id 43716; Thu, 03 Dec 2020 14:59:56 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kkq5M-00072j-Ng for xen-devel@lists.xenproject.org; Thu, 03 Dec 2020 14:59:56 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 53321761-819b-4c81-981f-30f84b9f9c33; Thu, 03 Dec 2020 14:59:55 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id D3822ABCE; Thu, 3 Dec 2020 14:59:54 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 53321761-819b-4c81-981f-30f84b9f9c33 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1607007595; h=from:from:reply-to: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=pSg9rmsjxLjre1vdrJTkpLratowiaDvXfmL0E9g5R6s=; b=u5gI8699UbcKNvZ99xU2yxsZvbUrGYNbcf6PaNCCFTDfIZQ1isJllL+M2Kh2GpQQO3fzew SReP1jXyQsIFOnto2+bgY8pqyahAUYUaH3Ev3fEfM33CGgPQkEruwLYix2mu3J9sB5qbGe KHuwCI4uzzYd75zH1X2Fx2w6cP2xfLs= Subject: Re: [PATCH v2 12/17] xen/hypfs: add new enter() and exit() per node callbacks To: Juergen Gross Cc: Andrew Cooper , George Dunlap , Ian Jackson , Julien Grall , Stefano Stabellini , Wei Liu , xen-devel@lists.xenproject.org References: <20201201082128.15239-1-jgross@suse.com> <20201201082128.15239-13-jgross@suse.com> From: Jan Beulich Message-ID: <0c57dd86-36d9-c378-6bdb-50221a7812b8@suse.com> Date: Thu, 3 Dec 2020 15:59:54 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 MIME-Version: 1.0 In-Reply-To: <20201201082128.15239-13-jgross@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 01.12.2020 09:21, Juergen Gross wrote: > In order to better support resource allocation and locking for dynamic > hypfs nodes add enter() and exit() callbacks to struct hypfs_funcs. > > The enter() callback is called when entering a node during hypfs user > actions (traversing, reading or writing it), while the exit() callback > is called when leaving a node (accessing another node at the same or a > higher directory level, or when returning to the user). > > For avoiding recursion this requires a parent pointer in each node. > Let the enter() callback return the entry address which is stored as > the last accessed node in order to be able to use a template entry for > that purpose in case of dynamic entries. I guess I'll learn in subsequent patches why this is necessary / useful. Right now it looks odd for the function to simple return the incoming argument, as this way it's clear the caller knows the correct value already. > @@ -100,11 +112,58 @@ static void hypfs_unlock(void) > } > } > > +const struct hypfs_entry *hypfs_node_enter(const struct hypfs_entry *entry) > +{ > + return entry; > +} > + > +void hypfs_node_exit(const struct hypfs_entry *entry) > +{ > +} > + > +static int node_enter(const struct hypfs_entry *entry) > +{ > + const struct hypfs_entry **last = &this_cpu(hypfs_last_node_entered); > + > + entry = entry->funcs->enter(entry); > + if ( IS_ERR(entry) ) > + return PTR_ERR(entry); > + > + ASSERT(!*last || *last == entry->parent); > + > + *last = entry; > + > + return 0; > +} > + > +static void node_exit(const struct hypfs_entry *entry) > +{ > + const struct hypfs_entry **last = &this_cpu(hypfs_last_node_entered); > + > + if ( !*last ) > + return; Under what conditions is this legitimate to happen? IOW shouldn't there be an ASSERT_UNREACHABLE() here? Jan