From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:55754 "EHLO mx0b-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752741AbaAGUP0 (ORCPT ); Tue, 7 Jan 2014 15:15:26 -0500 Message-ID: <52CC6052.3000100@fb.com> Date: Tue, 7 Jan 2014 15:15:14 -0500 From: Josef Bacik MIME-Version: 1.0 To: Eric Sandeen , Ben Myers , Eric Sandeen CC: , Subject: Re: [PATCH] xfstests: kill lib/random.c References: <1389038323-8304-1-git-send-email-jbacik@fb.com> <52CB20ED.1010705@redhat.com> <52CB2336.2060009@fb.com> <52CB2452.70507@redhat.com> <20140107200135.GD1935@sgi.com> <52CC5F27.1090602@sandeen.net> In-Reply-To: <52CC5F27.1090602@sandeen.net> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 01/07/2014 03:10 PM, Eric Sandeen wrote: > On 1/7/14, 2:01 PM, Ben Myers wrote: >> Hey Gents, >> >> On Mon, Jan 06, 2014 at 03:46:58PM -0600, Eric Sandeen wrote: >>> On 1/6/14, 3:42 PM, Josef Bacik wrote: >>>> On 01/06/2014 04:32 PM, Eric Sandeen wrote: >>>>> On 1/6/14, 1:58 PM, Josef Bacik wrote: >>>>>> I was trying to reproduce something with fsx and I noticed that no matter what >>>>>> seed I set I was getting the same file. Come to find out we are overloading >>>>>> random() with our own custom horribleness for some unknown reason. So nuke the >>>>>> damn thing from orbit and rely on glibc's random(). With this fix the -S option >>>>>> actually does something with fsx. Thanks, >>>>> Hm, old comments seem to indicate that this was done to make random >>>>> behave the same on different architectures (i.e. same result from same seed, >>>>> I guess?) I . . . don't know if that is true of glibc's random(), is it? >>>>> >>>>> I'd like to dig into the history just a bit before we yank this, just to >>>>> be sure. >>>> I think that if we need the output to match based on a predictable >>>> random() output then we've lost already. We shouldn't be checking for >>>> specific output (like inode numbers or sizes etc) that are dependant >>>> on random()'s behaviour, and if we are we need to fix those tests. So >>>> even if that is why it was put in place originally I'd say it is high >>>> time we ripped it out and fixed up any tests that rely on this >>>> behaviour. Thanks, >>> Yeah, you're probably right. And the ancient xfstests history seems to >>> be lost in the mists of time, at least as far as I can see. So I'm ok >>> with this but let's let Dave & SGI chime in too just to be certain. >> I did not have success locating the history prior to what we have posted on >> oss. I agree that it was likely added so that tests that expose output from >> random into golden output files will have the same results across arches. >> Maybe this is still of concern for folks who use a different c library with the >> kernel. >> >> Looks there are quite a few callers. IMO if we're going to remove this we >> should fix the tests first. > Or first, determine if they really need fixing. Did you find tests which > actually contain the random results in the golden output? > I looked through stuff when I ripped it out and I couldn't find anything that relied on consistent numbers, we tend to filter all that stuff out. I think ripping it out and waiting to see if somebody complains is a good way to figure out if things need fixing, but that may be less than friendly ;). Thanks, Josef