From: Rob Gardner Subject: Re: Huge race in lockd for async lock requests? Date: Thu, 28 May 2009 20:59:02 -0600 Message-ID: <4A1F4F76.70108@hp.com> References: <4A0D80B6.4070101@redhat.com> <4A0D9D63.1090102@hp.com> <4A11657B.4070002@redhat.com> <4A1168E0.3090409@hp.com> <4A1319F9.90304@hp.com> <4A13A973.4050703@hp.com> <4a140d0a.85c2f10a.53bc.0979@mx.google.com> <4A1431B1.6080708@hp.com> <20090528200523.GE13860@fieldses.org> <4A1F035B.4040306@hp.com> <20090529002636.GA19184@fieldses.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: "tmtalpey@gmail.com" , "linux-nfs@vger.kernel.org" To: "J. Bruce Fields" Return-path: Received: from g4t0014.houston.hp.com ([15.201.24.17]:4658 "EHLO g4t0014.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751253AbZE2C7D (ORCPT ); Thu, 28 May 2009 22:59:03 -0400 In-Reply-To: <20090529002636.GA19184@fieldses.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: J. Bruce Fields wrote: > > Looking at the code.... This is all under the BKL, and as far as I can > tell there aren't any blocking operations anywhere there, so I don't > think this should happen if the filesystem is careful. Have you seen it > happen? Aha, I just figured it out and you were right. The filesystem in this case was not careful. It broke the rules and actually made the fl_grant call *before* even returning to nlmsvc_lock's call to vfs_lock_file, and it did it in the lockd thread! So the BKL was of no use, and I saw nlmsvc_grant_deferred print "grant for unknown block". So I think everything is ok, no huge race in lockd for async lock requests. Thank you for clearing this up. Rob Gardner