From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 74EEFC04E84 for ; Fri, 17 May 2019 14:04:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 52C6A2166E for ; Fri, 17 May 2019 14:04:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728407AbfEQOEm (ORCPT ); Fri, 17 May 2019 10:04:42 -0400 Received: from out30-45.freemail.mail.aliyun.com ([115.124.30.45]:42500 "EHLO out30-45.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728535AbfEQOEm (ORCPT ); Fri, 17 May 2019 10:04:42 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R301e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04420;MF=wuyihao@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0TS-hbfu_1558101865; Received: from ali-186590dcce93-2.local(mailfrom:wuyihao@linux.alibaba.com fp:SMTPD_---0TS-hbfu_1558101865) by smtp.aliyun-inc.com(127.0.0.1); Fri, 17 May 2019 22:04:26 +0800 Subject: Re: [PATCH v2 1/2] NFSv4.1: Again fix a race where CB_NOTIFY_LOCK fails to wake a waiter To: Joseph Qi , linux-nfs@vger.kernel.org, Jeff Layton , "J. Bruce Fields" Cc: caspar@linux.alibaba.com References: <346806ac-2018-b780-4939-87f29648017c@linux.alibaba.com> <48a9d50b-f7b9-407d-06db-5c9079dfbf24@linux.alibaba.com> <07216eb5-7a15-d7b1-e553-58baa0e07282@linux.alibaba.com> From: Yihao Wu Message-ID: <129d03a2-2bea-2965-d614-e5622e2e828b@linux.alibaba.com> Date: Fri, 17 May 2019 22:04:30 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <07216eb5-7a15-d7b1-e553-58baa0e07282@linux.alibaba.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On 2019/5/17 5:22 PM, Joseph Qi wrote: > Hi Yihao, > > On 19/5/13 14:57, Yihao Wu wrote: >> Commit b7dbcc0e433f "NFSv4.1: Fix a race where CB_NOTIFY_LOCK fails to wake a waiter" >> found this bug. However it didn't fix it. >> >> This commit replaces schedule_timeout() with wait_woken() and >> default_wake_function() with woken_wake_function() in function >> nfs4_retry_setlk() and nfs4_wake_lock_waiter(). wait_woken() uses >> memory barriers in its implementation to avoid potential race condition >> when putting a process into sleeping state and then waking it up. >> >> Fixes: a1d617d8f134 ("nfs: allow blocking locks to be awoken by lock callbacks") >> Cc: stable@vger.kernel.org #4.9+ >> Signed-off-by: Yihao Wu >> --- >> fs/nfs/nfs4proc.c | 23 +++++++---------------- >> 1 file changed, 7 insertions(+), 16 deletions(-) >> >> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c >> index c29cbef..f9ed6b5 100644 >> --- a/fs/nfs/nfs4proc.c >> +++ b/fs/nfs/nfs4proc.c >> @@ -6932,7 +6932,6 @@ struct nfs4_lock_waiter { >> struct task_struct *task; >> struct inode *inode; >> struct nfs_lowner *owner; >> - bool notified; >> }; >> >> static int >> @@ -6954,13 +6953,13 @@ struct nfs4_lock_waiter { >> /* Make sure it's for the right inode */ >> if (nfs_compare_fh(NFS_FH(waiter->inode), &cbnl->cbnl_fh)) >> return 0; >> - >> - waiter->notified = true; >> } >> >> /* override "private" so we can use default_wake_function */ >> wait->private = waiter->task; >> - ret = autoremove_wake_function(wait, mode, flags, key); >> + ret = woken_wake_function(wait, mode, flags, key); >> + if (ret) >> + list_del_init(&wait->entry); >> wait->private = waiter; >> return ret; >> } >> @@ -6979,8 +6978,7 @@ struct nfs4_lock_waiter { >> .s_dev = server->s_dev }; >> struct nfs4_lock_waiter waiter = { .task = current, >> .inode = state->inode, >> - .owner = &owner, >> - .notified = false }; >> + .owner = &owner}; >> wait_queue_entry_t wait; >> >> /* Don't bother with waitqueue if we don't expect a callback */ >> @@ -6993,21 +6991,14 @@ struct nfs4_lock_waiter { >> add_wait_queue(q, &wait); >> >> while(!signalled()) { >> - waiter.notified = false; >> status = nfs4_proc_setlk(state, cmd, request); >> if ((status != -EAGAIN) || IS_SETLK(cmd)) >> break; >> >> status = -ERESTARTSYS; >> - spin_lock_irqsave(&q->lock, flags); >> - if (waiter.notified) { >> - spin_unlock_irqrestore(&q->lock, flags); >> - continue; >> - } >> - set_current_state(TASK_INTERRUPTIBLE); >> - spin_unlock_irqrestore(&q->lock, flags); >> - >> - freezable_schedule_timeout(NFS4_LOCK_MAXTIMEOUT); >> + freezer_do_not_count(); >> + wait_woken(&wait, TASK_INTERRUPTIBLE, NFS4_LOCK_MAXTIMEOUT); >> + freezer_count(); > > Since now variable 'flags' is not used anymore, we have to delete it as well. > Otherwise there is a compile warning “unused variable ‘flags’”. > > Thanks, > Joseph Thank you Joseph. I'll remove unused 'flags' in PATCH v3. Thanks, Yihao Wu > >> } >> >> finish_wait(q, &wait); >>