From patchwork Mon Sep 7 14:02:11 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kinglong Mee X-Patchwork-Id: 7135551 Return-Path: X-Original-To: patchwork-linux-nfs@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 20D59BEEC1 for ; Mon, 7 Sep 2015 14:02:30 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 2826820837 for ; Mon, 7 Sep 2015 14:02:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 32B1320835 for ; Mon, 7 Sep 2015 14:02:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752070AbbIGOCZ (ORCPT ); Mon, 7 Sep 2015 10:02:25 -0400 Received: from mail-pa0-f43.google.com ([209.85.220.43]:33504 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751184AbbIGOCW (ORCPT ); Mon, 7 Sep 2015 10:02:22 -0400 Received: by pacex6 with SMTP id ex6so98083997pac.0; Mon, 07 Sep 2015 07:02:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=subject:to:references:cc:from:message-id:date:user-agent :mime-version:in-reply-to:content-type:content-transfer-encoding; bh=+tKugXgOwTTT+p16p8mD11mnWfnfJcjARZPuzLxcaO4=; b=wPW/AV5/+seHwHSjwRbFsq25fsE/fSzkiQiQg7vB/1vsyX20IVHrIH8amPxgS5kuE1 EWX71Glk/wgY4Ot6N5M5veotZyWAhO+0dWJMwg/ObYD72r6TnEOsSdL2OA1SQpB6cjDA A6T8pFrlEjIeIF6cAIlxgdEVJb39+hTicb4guNeblecRybeoUv+qVjDURMF1wWrPTbcc 50a2OG4DCxSrgs1Dn8DnXlfispKA69K3oX2dsRpEvpQOqVgXu808PueCMxbdpOXD4SFf Nc/5Y3ay/6c9ZTINyZoo3Xj+RhI1IgGhQ0OQiVO16bXOq53mvp7lV2h4joNWM5W1emF1 DtOA== X-Received: by 10.68.111.165 with SMTP id ij5mr45432746pbb.59.1441634541961; Mon, 07 Sep 2015 07:02:21 -0700 (PDT) Received: from [192.168.99.8] ([104.143.41.79]) by smtp.googlemail.com with ESMTPSA id u6sm12169935pds.69.2015.09.07.07.02.15 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 07 Sep 2015 07:02:21 -0700 (PDT) Subject: [PATCH 1/6 v10] fs-pin: allow pin_remove() to be called other than from->kill() To: "J. Bruce Fields" , Al Viro References: <55ED9899.9010401@gmail.com> Cc: "linux-nfs@vger.kernel.org" , linux-fsdevel@vger.kernel.org, NeilBrown , Trond Myklebust , kinglongmee@gmail.com From: Kinglong Mee Message-ID: <55ED98E3.8060609@gmail.com> Date: Mon, 7 Sep 2015 22:02:11 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <55ED9899.9010401@gmail.com> Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org X-Spam-Status: No, score=-6.8 required=5.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, FREEMAIL_FROM, RCVD_IN_DNSWL_HI, T_DKIM_INVALID, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: NeilBrown fs-pin currently assumes when either the vfsmount or the fs_pin wants to unpin, pin_kill() will be called. This requires that the ->kill() function can wait for any transient references to the fs_pin to be released. If the structure containing the fs_pin doesn't already have the ability to wait for references, this can be a burden. As the fs_pin already has infrastructure for waiting, that can be leveraged to remove the burden. In this alternate scenario, only the vfsmount calls pin_kill() when it wants to unpin. The owner of the fs_pin() instead calls pin_remove(). The ->kill() function removes any long-term references, and then calls pin_kill() (recursively). When the last reference on (the structure containing) the fs_pin is dropped, pin_remove() will be called and the (recursive) pin_kill() call will complete. For this to be safe, the final "put" must *not* free the structure if pin_kill() has already been called, as that could leave ->kill() accessing freed data. So we provide a return value for pin_remove() which reports the old ->done value. When final put calls pin_remove() it checks that value. If it was 0, then pin_kill() has not called ->kill and will not, so final put can free the data structure. If it was -1, then pin_kill() has called ->kill, and ->kill will free the data structure - final put must not touch it. This makes the 'wait' infrastructure of fs_pin available to any pinning client which wants to use it. Signed-Off-By: NeilBrown --- fs/fs_pin.c | 18 +++++++++++++++++- include/linux/fs_pin.h | 2 +- 2 files changed, 18 insertions(+), 2 deletions(-) diff --git a/fs/fs_pin.c b/fs/fs_pin.c index 611b540..b7954a9 100644 --- a/fs/fs_pin.c +++ b/fs/fs_pin.c @@ -6,16 +6,32 @@ static DEFINE_SPINLOCK(pin_lock); -void pin_remove(struct fs_pin *pin) +/** + * pin_remove - disconnect an fs_pin from the pinned structure. + * @pin: The struct fs_pin which is pinning something. + * + * Detach a 'pin' which was added by pin_insert(). A return value + * of -1 implies that pin_kill() has already been called and that the + * ->kill() function now owns the data structure containing @pin. + * The function which called pin_remove() must not touch the data structure + * again (unless it is the ->kill() function itself). + * A return value of 0 implies an uneventful disconnect: pin_kill() has not called, + * and will not call, the ->kill() function on this @pin. + * Any other return value is a usage error - e.g. repeated call to pin_remove(). + */ +int pin_remove(struct fs_pin *pin) { + int ret; spin_lock(&pin_lock); hlist_del_init(&pin->m_list); hlist_del_init(&pin->s_list); spin_unlock(&pin_lock); spin_lock_irq(&pin->wait.lock); + ret = pin->done; pin->done = 1; wake_up_locked(&pin->wait); spin_unlock_irq(&pin->wait.lock); + return ret; } void pin_insert_group(struct fs_pin *pin, struct vfsmount *m, struct hlist_head *p) diff --git a/include/linux/fs_pin.h b/include/linux/fs_pin.h index 3886b3b..2fe9d3b 100644 --- a/include/linux/fs_pin.h +++ b/include/linux/fs_pin.h @@ -18,7 +18,7 @@ static inline void init_fs_pin(struct fs_pin *p, void (*kill)(struct fs_pin *)) p->kill = kill; } -void pin_remove(struct fs_pin *); +int pin_remove(struct fs_pin *); void pin_insert_group(struct fs_pin *, struct vfsmount *, struct hlist_head *); void pin_insert(struct fs_pin *, struct vfsmount *); void pin_kill(struct fs_pin *);