From patchwork Mon May 20 12:51:02 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: James Simmons X-Patchwork-Id: 10951051 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 E5DF2112C for ; Mon, 20 May 2019 12:52:39 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D474228770 for ; Mon, 20 May 2019 12:52:39 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id C852B28786; Mon, 20 May 2019 12:52:39 +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 7B2EB28824 for ; Mon, 20 May 2019 12:52:39 +0000 (UTC) Received: from pdx1-mailman02.dreamhost.com (localhost [IPv6:::1]) by pdx1-mailman02.dreamhost.com (Postfix) with ESMTP id 63D0C21FAAC; Mon, 20 May 2019 05:52:00 -0700 (PDT) X-Original-To: lustre-devel@lists.lustre.org Delivered-To: lustre-devel-lustre.org@pdx1-mailman02.dreamhost.com Received: from smtp4.ccs.ornl.gov (smtp4.ccs.ornl.gov [160.91.203.40]) by pdx1-mailman02.dreamhost.com (Postfix) with ESMTP id BC02C21F468 for ; Mon, 20 May 2019 05:51:21 -0700 (PDT) Received: from star.ccs.ornl.gov (star.ccs.ornl.gov [160.91.202.134]) by smtp4.ccs.ornl.gov (Postfix) with ESMTP id 825FA1005241; Mon, 20 May 2019 08:51:13 -0400 (EDT) Received: by star.ccs.ornl.gov (Postfix, from userid 2004) id 800392BB; Mon, 20 May 2019 08:51:13 -0400 (EDT) From: James Simmons To: Andreas Dilger , Oleg Drokin , NeilBrown Date: Mon, 20 May 2019 08:51:02 -0400 Message-Id: <1558356671-29599-21-git-send-email-jsimmons@infradead.org> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1558356671-29599-1-git-send-email-jsimmons@infradead.org> References: <1558356671-29599-1-git-send-email-jsimmons@infradead.org> Subject: [lustre-devel] [PATCH v2 20/29] 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 MIME-Version: 1.0 Errors-To: lustre-devel-bounces@lists.lustre.org Sender: "lustre-devel" X-Virus-Scanned: ClamAV using ClamSMTP From: NeilBrown 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 must be provided at a higher level than where this code is trying to handle it. So remove this pointless code. Signed-off-by: NeilBrown --- fs/lustre/obdclass/lustre_handles.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/fs/lustre/obdclass/lustre_handles.c b/fs/lustre/obdclass/lustre_handles.c index 00d8a89..d8bab07 100644 --- a/fs/lustre/obdclass/lustre_handles.c +++ b/fs/lustre/obdclass/lustre_handles.c @@ -149,15 +149,11 @@ void *class_handle2object(u64 cookie, const char *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); - CDEBUG(D_INFO, "GET %s %p refcount=%d\n", - h->h_owner, h, - refcount_read(&h->h_ref)); - retval = h; - } - spin_unlock(&h->h_lock); + refcount_inc(&h->h_ref); + CDEBUG(D_INFO, "GET %s %p refcount=%d\n", + h->h_owner, h, + refcount_read(&h->h_ref)); + retval = h; break; } rcu_read_unlock();