From patchwork Wed Jan 31 05:15:39 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 10193253 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 6F9AE60380 for ; Wed, 31 Jan 2018 05:17:35 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5E9A52841D for ; Wed, 31 Jan 2018 05:17:35 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5302B28446; Wed, 31 Jan 2018 05:17:35 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id CB78A2841D for ; Wed, 31 Jan 2018 05:17:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752345AbeAaFQr (ORCPT ); Wed, 31 Jan 2018 00:16:47 -0500 Received: from mx2.suse.de ([195.135.220.15]:35068 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752321AbeAaFQo (ORCPT ); Wed, 31 Jan 2018 00:16:44 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id DB805AB40; Wed, 31 Jan 2018 05:16:42 +0000 (UTC) From: NeilBrown To: David Howells , Andrew Morton , Ingo Molnar , Anna Schumaker Date: Wed, 31 Jan 2018 16:15:39 +1100 Subject: [PATCH 2/4] cred: add get_cred_rcu() Cc: NFS , lkml Message-ID: <151737573951.14845.5608065682472518930.stgit@noble> In-Reply-To: <151737571564.14845.2874586176125198504.stgit@noble> References: <151737571564.14845.2874586176125198504.stgit@noble> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Sometimes we want to opportunistically get a ref to a cred in an rcu_read_lock protected section. get_task_cred() does this, and NFS does as similar thing with its own credential structures. To prepare for NFS converting to use 'struct cred' more uniformly, define get_cred_rcu(), and use it in get_task_cred(). Signed-off-by: NeilBrown --- include/linux/cred.h | 11 +++++++++++ kernel/cred.c | 2 +- 2 files changed, 12 insertions(+), 1 deletion(-) -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html diff --git a/include/linux/cred.h b/include/linux/cred.h index 6dd51e503f23..69ed76f7d49f 100644 --- a/include/linux/cred.h +++ b/include/linux/cred.h @@ -247,6 +247,17 @@ static inline const struct cred *get_cred(const struct cred *cred) return get_new_cred(nonconst_cred); } +static inline const struct cred *get_cred_rcu(const struct cred *cred) +{ + struct cred *nonconst_cred = (struct cred *) cred; + if (!cred) + return NULL; + if (!atomic_inc_not_zero(&nonconst_cred->usage)) + return NULL; + validate_creds(cred); + return cred; +} + /** * put_cred - Release a reference to a set of credentials * @cred: The credentials to release diff --git a/kernel/cred.c b/kernel/cred.c index 4ce75c6fb752..f11aa4e0d2b9 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -195,7 +195,7 @@ const struct cred *get_task_cred(struct task_struct *task) do { cred = __task_cred((task)); BUG_ON(!cred); - } while (!atomic_inc_not_zero(&((struct cred *)cred)->usage)); + } while (!get_cred_rcu(cred)); rcu_read_unlock(); return cred;