From patchwork Sun May 22 15:38:44 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chuck Lever X-Patchwork-Id: 12858178 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 92290C433F5 for ; Sun, 22 May 2022 15:38:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348137AbiEVPit (ORCPT ); Sun, 22 May 2022 11:38:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39028 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241366AbiEVPit (ORCPT ); Sun, 22 May 2022 11:38:49 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 73A8837014 for ; Sun, 22 May 2022 08:38:48 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 28060B80CA9 for ; Sun, 22 May 2022 15:38:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D7297C385AA for ; Sun, 22 May 2022 15:38:45 +0000 (UTC) Subject: [PATCH RFC] NFSD: Fix possible sleep during nfsd4_release_lockowner() From: Chuck Lever To: linux-nfs@vger.kernel.org Date: Sun, 22 May 2022 11:38:44 -0400 Message-ID: <165323344948.2381.7808135229977810927.stgit@bazille.1015granger.net> User-Agent: StGit/1.5 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org nfsd4_release_lockowner() holds clp->cl_lock when it calls check_for_locks(). However, check_for_locks() calls nfsd_file_get() / nfsd_file_put() to access the backing inode's flc_posix list, and nfsd_file_put() can sleep if the inode was recently removed. Let's instead rely on the stateowner's reference count to gate whether the release is permitted. This should be a reliable indication of locks-in-use since file lock operations and ->lm_get_owner take appropriate references, which are released appropriately when file locks are removed. Reported-by: Dai Ngo Signed-off-by: Chuck Lever Cc: stable@vger.kernel.org --- fs/nfsd/nfs4state.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) This might be a naive approach, but let's start with it. This passes light testing, but it's not clear how much our existing fleet of tests exercises this area. I've locally built a couple of pynfs tests (one is based on the one Dai posted last week) and they pass too. I don't believe that FREE_STATEID needs the same simplification. diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index a280256cbb03..b77894e668a4 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -7559,12 +7559,9 @@ nfsd4_release_lockowner(struct svc_rqst *rqstp, /* see if there are still any locks associated with it */ lo = lockowner(sop); - list_for_each_entry(stp, &sop->so_stateids, st_perstateowner) { - if (check_for_locks(stp->st_stid.sc_file, lo)) { - status = nfserr_locks_held; - spin_unlock(&clp->cl_lock); - return status; - } + if (atomic_read(&sop->so_count) > 1) { + spin_unlock(&clp->cl_lock); + return nfserr_locks_held; } nfs4_get_stateowner(sop);