From patchwork Thu Feb 27 21:14:16 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: James Simmons X-Patchwork-Id: 11410743 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id BCACF924 for ; Thu, 27 Feb 2020 21:45:46 +0000 (UTC) Received: from pdx1-mailman02.dreamhost.com (pdx1-mailman02.dreamhost.com [64.90.62.194]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A4566246A2 for ; Thu, 27 Feb 2020 21:45:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A4566246A2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lustre-devel-bounces@lists.lustre.org Received: from pdx1-mailman02.dreamhost.com (localhost [IPv6:::1]) by pdx1-mailman02.dreamhost.com (Postfix) with ESMTP id 8F68034B0AC; Thu, 27 Feb 2020 13:36:25 -0800 (PST) X-Original-To: lustre-devel@lists.lustre.org Delivered-To: lustre-devel-lustre.org@pdx1-mailman02.dreamhost.com Received: from smtp3.ccs.ornl.gov (smtp3.ccs.ornl.gov [160.91.203.39]) by pdx1-mailman02.dreamhost.com (Postfix) with ESMTP id 1937421FBE7 for ; Thu, 27 Feb 2020 13:20:19 -0800 (PST) Received: from star.ccs.ornl.gov (star.ccs.ornl.gov [160.91.202.134]) by smtp3.ccs.ornl.gov (Postfix) with ESMTP id D82BA8ABB; Thu, 27 Feb 2020 16:18:17 -0500 (EST) Received: by star.ccs.ornl.gov (Postfix, from userid 2004) id D6A0846C; Thu, 27 Feb 2020 16:18:17 -0500 (EST) From: James Simmons To: Andreas Dilger , Oleg Drokin , NeilBrown Date: Thu, 27 Feb 2020 16:14:16 -0500 Message-Id: <1582838290-17243-389-git-send-email-jsimmons@infradead.org> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1582838290-17243-1-git-send-email-jsimmons@infradead.org> References: <1582838290-17243-1-git-send-email-jsimmons@infradead.org> Subject: [lustre-devel] [PATCH 388/622] lustre: obdclass: add comment for rcu handling in lu_env_remove 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: James Simmons , Lustre Development List MIME-Version: 1.0 Errors-To: lustre-devel-bounces@lists.lustre.org Sender: "lustre-devel" During the review it was pointed out why the RCU lock was dropped in lu_env_remove() but the code itself doesn't explain why. Add a comment giving the details why RCU locking is not needed. WC-bug-id: https://jira.whamcloud.com/browse/LU-12491 Lustre-commit: 709fbe6ee54a ("LU-12491 obdclass: add comment for rcu handling in lu_env_remove") Signed-off-by: James Simmons Reviewed-on: https://review.whamcloud.com/35447 Reviewed-by: Andreas Dilger Reviewed-by: Shaun Tancheff Reviewed-by: Neil Brown Reviewed-by: Oleg Drokin Signed-off-by: James Simmons --- fs/lustre/obdclass/lu_object.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/lustre/obdclass/lu_object.c b/fs/lustre/obdclass/lu_object.c index c94911d..d8bff3f 100644 --- a/fs/lustre/obdclass/lu_object.c +++ b/fs/lustre/obdclass/lu_object.c @@ -1932,6 +1932,11 @@ void lu_env_remove(struct lu_env *env) } } + /* The rcu_lock is not taking in this case since the key + * used is the actual task_struct. This implies that each + * object is only removed by the owning thread, so there + * can never be a race on a particular object. + */ lei = rhashtable_lookup_fast(&lu_env_rhash, &task, lu_env_rhash_params); if (lei && rhashtable_remove_fast(&lu_env_rhash, &lei->lei_linkage,