From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758578AbYD2WLt (ORCPT ); Tue, 29 Apr 2008 18:11:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756114AbYD2WLO (ORCPT ); Tue, 29 Apr 2008 18:11:14 -0400 Received: from mail.fieldses.org ([66.93.2.214]:51842 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757953AbYD2WLN (ORCPT ); Tue, 29 Apr 2008 18:11:13 -0400 Date: Tue, 29 Apr 2008 18:11:07 -0400 To: Mike Frysinger Cc: Andrew Morton , Bryan Wu , linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, willy@debian.org, viro@zeniv.linux.org.uk, uclinux-dist-devel@blackfin.uclinux.org, richterd@citi.umich.edu Subject: Re: [LTP/VFS] fcntl SETLEASE fails on ramfs/tmpfs Message-ID: <20080429221107.GH26468@fieldses.org> References: <386072610804282042y2dda4b52h927683a8a938ce1f@mail.gmail.com> <20080429135454.efebec8f.akpm@linux-foundation.org> <20080429214231.GC26468@fieldses.org> <8bd0f97a0804291501i2751d688h933508df2a4587b4@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8bd0f97a0804291501i2751d688h933508df2a4587b4@mail.gmail.com> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) From: "J. Bruce Fields" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 29, 2008 at 06:01:47PM -0400, Mike Frysinger wrote: > On Tue, Apr 29, 2008 at 5:42 PM, J. Bruce Fields wrote: > > The one thing I suspect is *not* a really serious problem here is the > > reported LTP failure, since probably the only user of this is Samba, > > which probably doesn't do a lot of tmpfs exports, and in any case it can > > probably soldier on (if with degraded performance--how badly I don't > > know) without getting the write lease it wants. > > i'm not sure i follow. the reported problem is that file locking does > not work on tmpfs/ramfs storage. a not terribly uncommon scenario is > to use tmpfs on /tmp (or similar location) and have file locking not > work at all. so programs that use file locking or scripts that > leverage the flock utility from the util-linux package break. There are three different mechanisms that might be called "file locks": - fcntl() locks, aka "posix locks", "byte-range locks": documented in the "Advisory locking" section of fcntl(2). - flock() locks: documented in flock(2) This is what the shell utility from util-linux uses. - leases, documented in the "Leases" section of fcntl(2). For the former two, I agree with you, applications actually depend on them. The bug report, however, is for leases, which are much less widely used. (The only users I know of are Samba and, to a lesser extent, NFSv4 (which doesn't currently use write leases due to all these problems).) --b.