From patchwork Wed Nov 7 04:12:30 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 10671771 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 3350015E9 for ; Wed, 7 Nov 2018 04:13:45 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 229BF28B80 for ; Wed, 7 Nov 2018 04:13:45 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1678628E5C; Wed, 7 Nov 2018 04:13:45 +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=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, 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 A590328BD4 for ; Wed, 7 Nov 2018 04:13:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730912AbeKGNmT (ORCPT ); Wed, 7 Nov 2018 08:42:19 -0500 Received: from mx2.suse.de ([195.135.220.15]:56394 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726552AbeKGNmT (ORCPT ); Wed, 7 Nov 2018 08:42:19 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 2FA16B659; Wed, 7 Nov 2018 04:13:42 +0000 (UTC) From: NeilBrown To: "J. Bruce Fields" , Chuck Lever , Jeff Layton , Trond Myklebust , Anna Schumaker Date: Wed, 07 Nov 2018 15:12:30 +1100 Subject: [PATCH 02/23] cred: add get_cred_rcu() Cc: Linux NFS Mailing List , linux-kernel@vger.kernel.org Message-ID: <154156395078.24086.348735293443892342.stgit@noble> In-Reply-To: <154156285766.24086.14262073575778354276.stgit@noble> References: <154156285766.24086.14262073575778354276.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(-) diff --git a/include/linux/cred.h b/include/linux/cred.h index f1085767e1b3..48979fcb95cf 100644 --- a/include/linux/cred.h +++ b/include/linux/cred.h @@ -252,6 +252,17 @@ 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 0b3ac72bd717..ba60162249e8 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;