From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754480AbbIOJJ4 (ORCPT ); Tue, 15 Sep 2015 05:09:56 -0400 Received: from mail.kernel.org ([198.145.29.136]:52721 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754414AbbIOJJw (ORCPT ); Tue, 15 Sep 2015 05:09:52 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Junxiao Bi , Joseph Qi , Mark Fasheh , Joel Becker , Andrew Morton , Linus Torvalds , Zefan Li Subject: [PATCH 3.4 079/146] ocfs2: dlm: fix race between purge and get lock resource Date: Tue, 15 Sep 2015 17:03:14 +0800 Message-Id: <1442307861-32031-79-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1442307787-31952-1-git-send-email-lizf@kernel.org> References: <1442307787-31952-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Junxiao Bi 3.4.109-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit b1432a2a35565f538586774a03bf277c27fc267d upstream. There is a race window in dlm_get_lock_resource(), which may return a lock resource which has been purged. This will cause the process to hang forever in dlmlock() as the ast msg can't be handled due to its lock resource not existing. dlm_get_lock_resource { ... spin_lock(&dlm->spinlock); tmpres = __dlm_lookup_lockres_full(dlm, lockid, namelen, hash); if (tmpres) { spin_unlock(&dlm->spinlock); >>>>>>>> race window, dlm_run_purge_list() may run and purge the lock resource spin_lock(&tmpres->spinlock); ... spin_unlock(&tmpres->spinlock); } } Signed-off-by: Junxiao Bi Cc: Joseph Qi Cc: Mark Fasheh Cc: Joel Becker Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Zefan Li --- fs/ocfs2/dlm/dlmmaster.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/fs/ocfs2/dlm/dlmmaster.c b/fs/ocfs2/dlm/dlmmaster.c index dbc372e..7ba6ac1 100644 --- a/fs/ocfs2/dlm/dlmmaster.c +++ b/fs/ocfs2/dlm/dlmmaster.c @@ -729,6 +729,19 @@ lookup: if (tmpres) { spin_unlock(&dlm->spinlock); spin_lock(&tmpres->spinlock); + + /* + * Right after dlm spinlock was released, dlm_thread could have + * purged the lockres. Check if lockres got unhashed. If so + * start over. + */ + if (hlist_unhashed(&tmpres->hash_node)) { + spin_unlock(&tmpres->spinlock); + dlm_lockres_put(tmpres); + tmpres = NULL; + goto lookup; + } + /* Wait on the thread that is mastering the resource */ if (tmpres->owner == DLM_LOCK_RES_OWNER_UNKNOWN) { __dlm_wait_on_lockres(tmpres); -- 1.9.1