linux-ext4 - Re: data=journal regressions in 3.16-rc1

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Date:	Thu, 26 Jun 2014 17:12:44 +0200 (CEST)
From:	Lukáš Czerner <lczerner@...hat.com>
To:	Eric Whitney <enwlinux@...il.com>
cc:	"Wilcox, Matthew R" <matthew.r.wilcox@...el.com>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	"tytso@....edu" <tytso@....edu>, namjae.jeon@...sung.com
Subject: Re: data=journal regressions in 3.16-rc1

On Mon, 23 Jun 2014, Eric Whitney wrote:

> Date: Mon, 23 Jun 2014 17:55:14 -0400
> From: Eric Whitney <enwlinux@...il.com>
> To: "Wilcox, Matthew R" <matthew.r.wilcox@...el.com>
> Cc: Eric Whitney <enwlinux@...il.com>,
>     "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
>     "tytso@....edu" <tytso@....edu>
> Subject: Re: data=journal regressions in 3.16-rc1
> 
> The first invocation of fsx causes generic/075 to fail.  Within 075.0.fsxlog,
> bad reads appear to be the cause:
> 
> READ BAD DATA: offset = 0xb7f0, size = 0x8111, fname = 075.0
> OFFSET	GOOD	BAD	RANGE
> 0x13000	0x1aee	0x0000	0x    0
> operation# (mod 256) for the bad data unknown, check HOLE and EXTEND ops
> 0x13001	0xee1a	0x0000	0x    1
> operation# (mod 256) for the bad data unknown, check HOLE and EXTEND ops
> 0x13002	0x1a01	0x0000	0x    2
> 
> (etc. - goes on until RANGE = 0xf)
> 
> This code is new to me, but it looks like fsx is getting zeros where it
> expects other values.

This seems to be related to collapse range feature. When adding -C
to the fsx the problem goes away. Also when comparing the fsxgood
with the real file it seems that there is a big chunk if the file
missing in the middle.

We need to investigate further. Namjae any idea what might be
causing it ?

-Lukas

> 
> Eric
> 
> 
> * Wilcox, Matthew R <matthew.r.wilcox@...el.com>:
> > Which test in 075.0.fsxlog indicates failure?
> > ________________________________________
> > From: Eric Whitney [enwlinux@...il.com]
> > Sent: June 23, 2014 1:24 PM
> > To: linux-ext4@...r.kernel.org
> > Cc: tytso@....edu; Wilcox, Matthew R
> > Subject: data=journal regressions in 3.16-rc1
> > 
> > My regression test results for 3.16-rc1 on x86_64 show three new xfstests
> > failures since 3.15 final when running on an ext4 filesystem mounted with the
> > data=journal and block_validity mount options (xfstests-bld's data_journal
> > scenario). These are generic/075, /112, and /231.  All three tests fail
> > consistently.
> > 
> > These failures bisect to this kernel patch:
> > 7fc34a62ca  mm/msync.c: sync only the requested range in msync()
> > 
> > These failures also appear when running on 3.16-rc2, and disappear if the
> > aforementioned patch is reverted.  I've not seen the failures in any of the
> > other test scenarios I've run on 3.16-rc1 (4k, ext3, nojournal, etc.).
> > 
> > No error messages appear in the kernel log, and not a lot useful is reported
> > when a test fails.  Just for reference, here's the result of a generic/075
> > failure:
> > 
> > generic/075 62s ...     [15:33:07] [15:33:09] [failed, exit status 1] - output mismatch (see /root/xfstests/results//generic/075.out.bad)
> >     --- tests/generic/075.out   2014-06-16 13:14:27.233891460 -0400
> >     +++ /root/xfstests/results//generic/075.out.bad     2014-06-23 15:33:09.654212783 -0400
> >     @@ -4,15 +4,5 @@
> >      -----------------------------------------------
> >      fsx.0 : -d -N numops -S 0
> >      -----------------------------------------------
> >     -
> >     ------------------------------------------------
> >     -fsx.1 : -d -N numops -S 0 -x
> >     ------------------------------------------------
> >     ...
> >     (Run 'diff -u tests/generic/075.out /root/xfstests/results//generic/075.out.bad'  to see the entire diff)
> > Ran: generic/075
> > Failures: generic/075
> > Failed 1 of 1 tests
> > 
> > 
> > And the contents of xfstests/results/generic/075.out.bad:
> > 
> > 
> > QA output created by 075
> > brevity is wit...
> > 
> > -----------------------------------------------
> > fsx.0 : -d -N numops -S 0
> > -----------------------------------------------
> >     fsx (-d -N 1000 -S 0) failed, 0 - compare /root/xfstests/results//generic/075.0.{good,bad,fsxlog}
> > od: /root/xfstests/results//generic/075.0.fsxgood: No such file or directory
> > 
> > 
> > Additional test configuration info:
> > 
> > e2fsprogs master branch:  bb9cca2ca9
> > xfstests master branch:  45d1fac130
> > 
> > Perhaps data=journal has an unexpected dependency on the old msync behavior,
> > given the patch comment?
> > 
> > Thanks,
> > Eric
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