RE: data=journal regressions in 3.16-rc1

["Lukáš Czerner" <lczerner@redhat.com>]

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On Fri, 27 Jun 2014, Namjae Jeon wrote:

> Date: Fri, 27 Jun 2014 15:03:38 +0900
> From: Namjae Jeon <namjae.jeon@samsung.com>
> To: 'Lukáš Czerner' <lczerner@redhat.com>,
>     "'Wilcox, Matthew R'" <matthew.r.wilcox@intel.com>
> Cc: 'Eric Whitney' <enwlinux@gmail.com>, linux-ext4@vger.kernel.org,
>     tytso@mit.edu, Christoph Hellwig <hch@infradead.org>,
>     Ashish Sangwan <a.sangwan@samsung.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@gmail.com>
> > > > To: "Wilcox, Matthew R" <matthew.r.wilcox@intel.com>
> > > > Cc: Eric Whitney <enwlinux@gmail.com>,
> > > >     "linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>,
> > > >     "tytso@mit.edu" <tytso@mit.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 ?
> > Hi, Lukas.
> > 
> > It seems this issue is related with collapse range on test result(with fsx -C option)
> > I will check it.
> 
> Looks fstart is wrongly calcurated..
> 
> - fstart = start + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
> + fstart = (start - vma->vm_start) + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);

Good catch, this indeed is a bug. And this change fixes the problem
we're seeing with data=journal in ext4.

Will you send a proper patch ?

Thanks!
-Lukas

> 
> Could you confirm this change is correct ? Matthew ?
> 
> Thanks.
> 
> > 
> > Thanks!
> > >
> > > -Lukas
> > >
> > > >
> > > > Eric
> > > >
> > > >
> > > > * Wilcox, Matthew R <matthew.r.wilcox@intel.com>:
> > > > > Which test in 075.0.fsxlog indicates failure?
> > > > > ________________________________________
> > > > > From: Eric Whitney [enwlinux@gmail.com]
> > > > > Sent: June 23, 2014 1:24 PM
> > > > > To: linux-ext4@vger.kernel.org
> > > > > Cc: tytso@mit.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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> > > >
> 
>