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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 BA1EAC433DF for ; Wed, 3 Jun 2020 01:22:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9A9A120734 for ; Wed, 3 Jun 2020 01:22:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728114AbgFCBW4 (ORCPT ); Tue, 2 Jun 2020 21:22:56 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:5840 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726112AbgFCBW4 (ORCPT ); Tue, 2 Jun 2020 21:22:56 -0400 Received: from DGGEMS407-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 1C443241117DE6A3F4A9; Wed, 3 Jun 2020 09:22:54 +0800 (CST) Received: from [127.0.0.1] (10.166.212.218) by DGGEMS407-HUB.china.huawei.com (10.3.19.207) with Microsoft SMTP Server id 14.3.487.0; Wed, 3 Jun 2020 09:22:50 +0800 Subject: Re: [PATCH] locks: add locks_move_blocks in posix_lock_inode To: Jeff Layton , NeilBrown , , CC: , "bfields@vger.kernel.org" References: <20200601091616.34137-1-yangerkun@huawei.com> <877dwq757c.fsf@notabene.neil.brown.name> <63020790a240cfcd1d798147edebbc231b1ff32b.camel@kernel.org> From: yangerkun Message-ID: Date: Wed, 3 Jun 2020 09:22:49 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <63020790a240cfcd1d798147edebbc231b1ff32b.camel@kernel.org> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.166.212.218] X-CFilter-Loop: Reflected Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 在 2020/6/2 23:56, Jeff Layton 写道: > On Tue, 2020-06-02 at 21:49 +0800, yangerkun wrote: >> >> 在 2020/6/2 7:10, NeilBrown 写道: >>> On Mon, Jun 01 2020, yangerkun wrote: >>> >>>> We forget to call locks_move_blocks in posix_lock_inode when try to >>>> process same owner and different types. >>>> >>> >>> This patch is not necessary. >>> The caller of posix_lock_inode() must calls locks_delete_block() on >>> 'request', and that will remove all blocked request and retry them. >>> >>> So calling locks_move_blocks() here is at most an optimization. Maybe >>> it is a useful one. >>> >>> What led you to suggesting this patch? Were you just examining the >>> code, or was there some problem that you were trying to solve? >> >> >> Actually, case of this means just replace a exists file_lock. And once >> we forget to call locks_move_blocks, the function call of >> posix_lock_inode will also call locks_delete_block, and will wakeup all >> blocked requests and retry them. But we should do this until we UNLOCK >> the file_lock! So, it's really a bug here. >> > > Waking up waiters to re-poll a lock that's still blocked seems wrong. I > agree with Neil that this is mainly an optimization, but it does look > useful. Agree. Logic of this seems wrong, but it won't trigger any problem since the waiters will conflict and try wait again. > > Unfortunately this is the type of thing that's quite difficult to test > for in a userland testcase. Is this something you noticed due to the > extra wakeups or did you find it by inspection? It'd be great to have a > better way to test for this in xfstests or something. Notice this after reading the patch 5946c4319ebb ("fs/locks: allow a lock request to block other requests."), and find that we have do the same thing exist in flock_lock_inode and another place exists in posix_lock_inode. > > I'll plan to add this to linux-next. It should make v5.9, but let me > know if this is causing real-world problems and maybe we can make a case > for v5.8. Actually, I have not try to find will this lead to some real-world problems... Sorry for this.:( Thanks, Kun. > > Thanks, > Jeff > >>> >>>> Signed-off-by: yangerkun >>>> --- >>>> fs/locks.c | 1 + >>>> 1 file changed, 1 insertion(+) >>>> >>>> diff --git a/fs/locks.c b/fs/locks.c >>>> index b8a31c1c4fff..36bd2c221786 100644 >>>> --- a/fs/locks.c >>>> +++ b/fs/locks.c >>>> @@ -1282,6 +1282,7 @@ static int posix_lock_inode(struct inode *inode, struct file_lock *request, >>>> if (!new_fl) >>>> goto out; >>>> locks_copy_lock(new_fl, request); >>>> + locks_move_blocks(new_fl, request); >>>> request = new_fl; >>>> new_fl = NULL; >>>> locks_insert_lock_ctx(request, &fl->fl_list); >>>> -- >>>> 2.21.3 >