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 A8308C4361A for ; Thu, 3 Dec 2020 15:14:38 +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 105F4206A4 for ; Thu, 3 Dec 2020 15:14:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 105F4206A4 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.43761.78607 (Exim 4.92) (envelope-from ) id 1kkqJL-000126-13; Thu, 03 Dec 2020 15:14:23 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 43761.78607; Thu, 03 Dec 2020 15:14:22 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kkqJK-00011z-UD; Thu, 03 Dec 2020 15:14:22 +0000 Received: by outflank-mailman (input) for mailman id 43761; Thu, 03 Dec 2020 15:14:21 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kkqJJ-00011s-C2 for xen-devel@lists.xenproject.org; Thu, 03 Dec 2020 15:14:21 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 287800c4-73b6-4983-97ab-e58aa7256a5a; Thu, 03 Dec 2020 15:14:20 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 3ACF8AC65; Thu, 3 Dec 2020 15:14:19 +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: 287800c4-73b6-4983-97ab-e58aa7256a5a 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=1607008459; h=from:from:reply-to: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=cAn2gV3OTPE4+DePVqcaxMGFcAzZWJKht69BAfdBfVg=; b=ZjA27wArEfi1L+86c1bhieLj1dHbCNkTwNqAEydupkfmm0n2XD3q86/lSnlwEAx5FKQElv 2MtVGvvX9gYqZ2on0MK5kaccqnwgwtWszS7GevldmYhowm2lZNQhWyTd/kUsLZFB4NuBIi C28OrlW6sxQ/T/P595qUtmGO9pG1wWI= Subject: Re: [PATCH v2 12/17] xen/hypfs: add new enter() and exit() per node callbacks To: Jan Beulich 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> <0c57dd86-36d9-c378-6bdb-50221a7812b8@suse.com> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: <2503547c-1b3c-2224-c4a9-c647d9d1a058@suse.com> Date: Thu, 3 Dec 2020 16:14:18 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <0c57dd86-36d9-c378-6bdb-50221a7812b8@suse.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="DpINg4kaag5UxHPSm2KwlwvvqM6Trvnbl" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --DpINg4kaag5UxHPSm2KwlwvvqM6Trvnbl Content-Type: multipart/mixed; boundary="AXnDHrJzysLHpeiJxwKVZv0EOYK9JNuAV"; protected-headers="v1" From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= To: Jan Beulich Cc: Andrew Cooper , George Dunlap , Ian Jackson , Julien Grall , Stefano Stabellini , Wei Liu , xen-devel@lists.xenproject.org Message-ID: <2503547c-1b3c-2224-c4a9-c647d9d1a058@suse.com> Subject: Re: [PATCH v2 12/17] xen/hypfs: add new enter() and exit() per node callbacks References: <20201201082128.15239-1-jgross@suse.com> <20201201082128.15239-13-jgross@suse.com> <0c57dd86-36d9-c378-6bdb-50221a7812b8@suse.com> In-Reply-To: <0c57dd86-36d9-c378-6bdb-50221a7812b8@suse.com> --AXnDHrJzysLHpeiJxwKVZv0EOYK9JNuAV Content-Type: multipart/mixed; boundary="------------29B8FDFF0FC4529743171AB6" Content-Language: en-US This is a multi-part message in MIME format. --------------29B8FDFF0FC4529743171AB6 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 03.12.20 15:59, Jan Beulich wrote: > 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. >=20 > 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. Basically for dynamic entries based on a template the entry function will return the address of template->e instead of the dynamic entry itself. This will enable to have the standard entry functions for any nodes being linked to the template. >=20 >> @@ -100,11 +112,58 @@ static void hypfs_unlock(void) >> } >> } >> =20 >> +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 =3D &this_cpu(hypfs_last_node_ent= ered); >> + >> + entry =3D entry->funcs->enter(entry); >> + if ( IS_ERR(entry) ) >> + return PTR_ERR(entry); >> + >> + ASSERT(!*last || *last =3D=3D entry->parent); >> + >> + *last =3D entry; >> + >> + return 0; >> +} >> + >> +static void node_exit(const struct hypfs_entry *entry) >> +{ >> + const struct hypfs_entry **last =3D &this_cpu(hypfs_last_node_ent= ered); >> + >> + if ( !*last ) >> + return; >=20 > Under what conditions is this legitimate to happen? IOW shouldn't > there be an ASSERT_UNREACHABLE() here? This is for the "/" node. 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