From patchwork Tue Feb 19 00:09:06 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 10819097 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 681356C2 for ; Tue, 19 Feb 2019 00:14:52 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 540002B65E for ; Tue, 19 Feb 2019 00:14:52 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 488DF2BDE4; Tue, 19 Feb 2019 00:14:52 +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=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from pdx1-mailman02.dreamhost.com (pdx1-mailman02.dreamhost.com [64.90.62.194]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 3595E2B65E for ; Tue, 19 Feb 2019 00:14:51 +0000 (UTC) Received: from pdx1-mailman02.dreamhost.com (localhost [IPv6:::1]) by pdx1-mailman02.dreamhost.com (Postfix) with ESMTP id F07924E3178; Mon, 18 Feb 2019 16:14:50 -0800 (PST) X-Original-To: lustre-devel@lists.lustre.org Delivered-To: lustre-devel-lustre.org@pdx1-mailman02.dreamhost.com Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by pdx1-mailman02.dreamhost.com (Postfix) with ESMTP id 0FCF24E312F for ; Mon, 18 Feb 2019 16:14:49 -0800 (PST) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 4F0C5ACC1; Tue, 19 Feb 2019 00:14:48 +0000 (UTC) From: NeilBrown To: James Simmons , Andreas Dilger , Oleg Drokin Date: Tue, 19 Feb 2019 11:09:06 +1100 Message-ID: <155053494669.24125.10413095649039339042.stgit@noble.brown> In-Reply-To: <155053473693.24125.6976971762921761309.stgit@noble.brown> References: <155053473693.24125.6976971762921761309.stgit@noble.brown> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Subject: [lustre-devel] [PATCH 33/37] lustre: portals_handle: remove locking from class_handle2object() X-BeenThere: lustre-devel@lists.lustre.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "For discussing Lustre software development." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Lustre Development List Errors-To: lustre-devel-bounces@lists.lustre.org Sender: "lustre-devel" X-Virus-Scanned: ClamAV using ClamSMTP There can be no value in this locking and test on h_in. If the lookup could have run in parallel with class_handle_unhash_nolock() and seen "h_in == 0", then it could equally well have run moments earlier and not seen it - no locking would prevent that, so the caller much be prepared to have an object returned which has already been unhashed by the time it sees the object. In other words, an interlock between unhash and lookup much be provided at a higher level than where this code is trying to handle it. So remove this pointless code. Signed-off-by: NeilBrown --- .../lustre/lustre/obdclass/lustre_handles.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/drivers/staging/lustre/lustre/obdclass/lustre_handles.c b/drivers/staging/lustre/lustre/obdclass/lustre_handles.c index 30a84ff1e479..40461c7fc8ef 100644 --- a/drivers/staging/lustre/lustre/obdclass/lustre_handles.c +++ b/drivers/staging/lustre/lustre/obdclass/lustre_handles.c @@ -149,12 +149,8 @@ void *class_handle2object(u64 cookie, void *owner) if (h->h_cookie != cookie || h->h_owner != owner) continue; - spin_lock(&h->h_lock); - if (likely(h->h_in != 0)) { - refcount_inc(&h->h_ref); - retval = h; - } - spin_unlock(&h->h_lock); + refcount_inc(&h->h_ref); + retval = h; break; } rcu_read_unlock();