From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752963AbbFQWrv (ORCPT ); Wed, 17 Jun 2015 18:47:51 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:35740 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751859AbbFQWaZ (ORCPT ); Wed, 17 Jun 2015 18:30:25 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Junxiao Bi , Joseph Qi , Mark Fasheh , Joel Becker , Andrew Morton , Linus Torvalds , Kamal Mostafa Subject: [PATCH 3.13.y-ckt 053/122] ocfs2: dlm: fix race between purge and get lock resource Date: Wed, 17 Jun 2015 15:28:00 -0700 Message-Id: <1434580149-3095-54-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1434580149-3095-1-git-send-email-kamal@canonical.com> References: <1434580149-3095-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.13.11-ckt22 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Junxiao Bi 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: Kamal Mostafa --- 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 1be3398..1dd0bcc 100644 --- a/fs/ocfs2/dlm/dlmmaster.c +++ b/fs/ocfs2/dlm/dlmmaster.c @@ -726,6 +726,19 @@ 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