Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760788AbXE2T1m (ORCPT ); Tue, 29 May 2007 15:27:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752153AbXE2T1f (ORCPT ); Tue, 29 May 2007 15:27:35 -0400 Received: from agminet01.oracle.com ([141.146.126.228]:53421 "EHLO agminet01.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750926AbXE2T1f (ORCPT ); Tue, 29 May 2007 15:27:35 -0400 Date: Tue, 29 May 2007 12:33:26 -0700 From: Randy Dunlap To: "Josh Boyer" Cc: "Robert P. J. Day" , "Andrew Morton" , "Linux Kernel Mailing List" , "Alexander Viro" Subject: Re: [PATCH] FILESYSTEMS: Delete unused "int dummy[5]" from inodes_stat_t. Message-Id: <20070529123326.a8a1bd64.randy.dunlap@oracle.com> In-Reply-To: <625fc13d0705291144u1aef3b6dx4b00873f3d05b652@mail.gmail.com> References: <20070529110041.49bf57f1.akpm@linux-foundation.org> <20070529111902.27055fd0.randy.dunlap@oracle.com> <465C71EA.5040706@oracle.com> <625fc13d0705291144u1aef3b6dx4b00873f3d05b652@mail.gmail.com> Organization: Oracle Linux Eng. X-Mailer: Sylpheed 2.3.1 (GTK+ 2.8.10; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Whitelist: TRUE X-Whitelist: TRUE X-Brightmail-Tracker: AAAAAQAAAAI= Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2639 Lines: 61 On Tue, 29 May 2007 13:44:42 -0500 Josh Boyer wrote: > On 5/29/07, Randy Dunlap wrote: > > Robert P. J. Day wrote: > > > On Tue, 29 May 2007, Randy Dunlap wrote: > > > > > >> On Tue, 29 May 2007 14:07:01 -0400 (EDT) Robert P. J. Day wrote: > > >> > > >>> On Tue, 29 May 2007, Andrew Morton wrote: > > >>> > > >>>> kernel/sysctl.c: > > >>>> > > >>>> { > > >>>> .ctl_name = FS_STATINODE, > > >>>> .procname = "inode-state", > > >>>> .data = &inodes_stat, > > >>>> .maxlen = 7*sizeof(int), <----- > > >>>> .mode = 0444, > > >>>> .proc_handler = &proc_dointvec, > > >>>> }, > > >>>> > > >>>> akpm:/home/akpm> cat /proc/sys/fs/inode-state > > >>>> 608039 178454 0 0 0 0 0 > > >>>> > > >>>> So it _is_ used: to present those five zeroes. I think this is > > >>>> for back-compatibility with some cretaceous-era kernel. > > >>> ah, gotcha. well, i'll leave this up to someone else to do > > >>> anything with if they are so inclined. > > >> There's little to be done, except possibly put a /* comment */ on > > >> the struct's dummy line so that we don't go thru this again in N > > >> years. > > > > > > so, just to clarify, what *is* the value of those trailing five > > > zeroes? andrew suggests it's to be backward-compatible with an old > > > kernel, which doesn't make much sense to me. it would make more sense > > > to say that that's backward-compatible with some old userspace app > > > that always wants to see seven values and just ignores the last five. > > > > Agreed, it's for compat with some (unknown) userspace app that reads > > /proc/sys/fs/inode-state and scans for 7 (or more than 2) numbers there. > > The mantra is "don't break userspace," so we leave the numbers there... > > Couldn't you remove the dummy member and just have the proc entry > print out 5 dummy zeros? In theory someone could do that, but it would (a) require a comment so that someone else didn't try to remove it 5 years from now and (b) require more proc/sysctl code just for that one sysctl entry since the sysctl entries are all table-driven right now and printing 5 zeros would require a new /proc/sys handler for just this one sysctl. --- ~Randy *** Remember to use Documentation/SubmitChecklist when testing your code *** - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/