From patchwork Thu Jul 30 05:48:03 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yang Dongsheng X-Patchwork-Id: 6898641 Return-Path: X-Original-To: patchwork-linux-fsdevel@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 5DE2AC05AC for ; Thu, 30 Jul 2015 05:55:11 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 8DA5D20551 for ; Thu, 30 Jul 2015 05:55:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A9B7B2054D for ; Thu, 30 Jul 2015 05:55:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753943AbbG3FzG (ORCPT ); Thu, 30 Jul 2015 01:55:06 -0400 Received: from cn.fujitsu.com ([59.151.112.132]:20145 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751444AbbG3FyQ (ORCPT ); Thu, 30 Jul 2015 01:54:16 -0400 X-IronPort-AV: E=Sophos;i="5.15,520,1432569600"; d="scan'208";a="99064472" Received: from unknown (HELO edo.cn.fujitsu.com) ([10.167.33.5]) by heian.cn.fujitsu.com with ESMTP; 30 Jul 2015 13:57:48 +0800 Received: from G08CNEXCHPEKD02.g08.fujitsu.local (localhost.localdomain [127.0.0.1]) by edo.cn.fujitsu.com (8.14.3/8.13.1) with ESMTP id t6U5qNBi028267; Thu, 30 Jul 2015 13:52:23 +0800 Received: from yds-PC.g08.fujitsu.local (10.167.226.66) by G08CNEXCHPEKD02.g08.fujitsu.local (10.167.33.89) with Microsoft SMTP Server (TLS) id 14.3.181.6; Thu, 30 Jul 2015 13:54:14 +0800 From: Dongsheng Yang To: , , , CC: , , Dongsheng Yang Subject: [PATCH v2 07/35] fs: char_dev: introduce cd_acquire function to acquire cdev Date: Thu, 30 Jul 2015 13:48:03 +0800 Message-ID: <1438235311-23788-8-git-send-email-yangds.fnst@cn.fujitsu.com> X-Mailer: git-send-email 1.8.4.2 In-Reply-To: <1438235311-23788-1-git-send-email-yangds.fnst@cn.fujitsu.com> References: <1438235311-23788-1-git-send-email-yangds.fnst@cn.fujitsu.com> MIME-Version: 1.0 X-Originating-IP: [10.167.226.66] Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Spam-Status: No, score=-8.3 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, 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 cd_acquire() works like bd_acquire() to get cdev by an inode, this commit is a preparation for lookup_cdev(). Signed-off-by: Dongsheng Yang --- fs/char_dev.c | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/fs/char_dev.c b/fs/char_dev.c index ea06a3d..e818faa 100644 --- a/fs/char_dev.c +++ b/fs/char_dev.c @@ -439,6 +439,41 @@ static int exact_lock(dev_t dev, void *data) return cdev_get(p) ? 0 : -1; } +struct cdev *cd_acquire(struct inode *inode) +{ + struct cdev *cdev; + struct cdev *new = NULL; + + spin_lock(&cdev_lock); + cdev = inode->i_cdev; + if (!cdev) { + struct kobject *kobj; + int idx; + spin_unlock(&cdev_lock); + kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx); + if (!kobj) { + cdev = NULL; + goto out; + } + new = container_of(kobj, struct cdev, kobj); + spin_lock(&cdev_lock); + /* Check i_cdev again in case somebody beat us to it while + we dropped the lock. */ + cdev = inode->i_cdev; + if (!cdev) { + inode->i_cdev = cdev = new; + list_add(&inode->i_devices, &cdev->list); + } + } + + if (!cdev_get(cdev)) + cdev = NULL; + spin_unlock(&cdev_lock); + +out: + return cdev; +} + /** * cdev_add() - add a char device to the system * @p: the cdev structure for the device