Return-Path: Received: from esgaroth.petrovitsch.at ([78.47.184.11]:3654 "EHLO esgaroth.petrovitsch.priv.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754094Ab0E0OLD (ORCPT ); Thu, 27 May 2010 10:11:03 -0400 Subject: Re: Debugging fcntl() file locks From: Bernd Petrovitsch To: Trond Myklebust Cc: linux-nfs@vger.kernel.org In-Reply-To: <1274963686.2895.7.camel@heimdal.trondhjem.org> References: <1274955060.14002.40.camel@thorin> <1274963686.2895.7.camel@heimdal.trondhjem.org> Content-Type: text/plain; charset="UTF-8" Date: Thu, 27 May 2010 15:46:37 +0200 Message-ID: <1274967997.14002.42.camel@thorin> Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 Hi! On Don, 2010-05-27 at 08:34 -0400, Trond Myklebust wrote: > On Thu, 2010-05-27 at 12:11 +0200, Bernd Petrovitsch wrote: [...] > > How can I debug fcntl() file locks on a NFSv3-client? > > The server side is a NetApp-Box (no details at hand but I can ask). > > The client side are stock-RHEL5.3/CentOS-5.3 kernels - 2.6.18-92.el5. > > > > The file system in question is mounted on 2 clients. flock() on a file > > succeeds but fcntl() fails with EAGAIN. From what I found in the > > Internet and manual pages, this means that someone else already locked > > that file (- the file is successfully open()ed read/write so it can't be > > "your are not allowed to write-lock the file"). > > But how do I find out on which host and which process? > > > > strace shows: > > ---- snip ---- > > open("/... secret ...", O_RDWR) = 3 > > ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7fff7925b400) = -1 ENOTTY (Inappropriate ioctl for device) > > lseek(3, 0, SEEK_CUR) = 0 > > fstat(3, {st_mode=S_IFREG|0600, st_size=935, ...}) = 0 > > fcntl(3, F_SETFD, FD_CLOEXEC) = 0 > > flock(3, LOCK_EX|LOCK_NB) = 0 > > fcntl(3, F_SETLK, {type=F_WRLCK, whence=SEEK_SET, start=0, len=0}) = -1 EAGAIN (Resource temporarily unavailable) > > ---- snip ---- > > [ This is a perl script using CPAN modules at the top. ] [...] > The Linux NFS client does not allow you to lock a file using both > flock() and POSIX locks. You should choose one or the other locking > scheme. If you remove the flock() line above, then the POSIX lock will > likely succeed. Thanks. Does flock() work on NFS these days on NFS? Historically that was not the case IIRC. Bernd -- Bernd Petrovitsch Email : bernd@petrovitsch.priv.at LUGA : http://www.luga.at