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Re: xfstests xfs fuzzers fail with DAX

Started byDan Williams <dan.j.williams@intel.com>
First post2016-08-30 04:00 +0200
Last post2016-08-30 18:50 +0200
Articles 5 — 2 participants

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  Re: xfstests xfs fuzzers fail with DAX Dan Williams <dan.j.williams@intel.com> - 2016-08-30 04:00 +0200
    Re: xfstests xfs fuzzers fail with DAX "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-08-30 04:40 +0200
      Re: xfstests xfs fuzzers fail with DAX Dan Williams <dan.j.williams@intel.com> - 2016-08-30 17:00 +0200
        Re: xfstests xfs fuzzers fail with DAX Dan Williams <dan.j.williams@intel.com> - 2016-08-30 18:30 +0200
          Re: xfstests xfs fuzzers fail with DAX "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-08-30 18:50 +0200

#1472194 — Re: xfstests xfs fuzzers fail with DAX

FromDan Williams <dan.j.williams@intel.com>
Date2016-08-30 04:00 +0200
SubjectRe: xfstests xfs fuzzers fail with DAX
Message-ID<sbGvf-6E9-3@gated-at.bofh.it>
[ Adding Darrick on the off chance that this triggers an "aha, of
course it does!" ]

Darrick these corruption tests you added to xfstests last year all
fail the same way with DAX enabled.  They spew:

    "pwrite64: Structure needs cleaning"

...reports that are cleaned up by running without "-o dax".

Alternatively you could sit back and watch me try to figure it out,
that should be quite entertaining... as a start I'll try to pin down a
stack trace when the error is returned.


On Wed, Aug 3, 2016 at 7:45 PM, Xiong Zhou <xzhou@redhat.com> wrote:
> Hi,
>
> A few xfs fuzzers in xfstests fail with dax mount option, pass without dax.
> They are xfs/086 xfs/088 xfs/089 xfs/091.
>
> xfstests to commit 4470ad4c7e  (Jul 26)
> kernel   to commit dd95069545  (Jul 24)
>
> + ./check xfs/091
> FSTYP         -- xfs (non-debug)
> PLATFORM      -- Linux/x86_64 rhel73 4.7.0+
> MKFS_OPTIONS  -- -f -bsize=4096 /dev/pmem1
> MOUNT_OPTIONS -- -o context=system_u:object_r:nfs_t:s0 /dev/pmem1 /daxsch
>
> xfs/091  104s
> Ran: xfs/091
> Passed all 1 tests
>
> + echo 'MOUNT_OPTIONS="-o dax"'
> + ./check xfs/091
> FSTYP         -- xfs (non-debug)
> PLATFORM      -- Linux/x86_64 rhel73 4.7.0+
> MKFS_OPTIONS  -- -f -bsize=4096 /dev/pmem1
> MOUNT_OPTIONS -- -o dax -o context=system_u:object_r:nfs_t:s0 /dev/pmem1 /daxsch
>
> xfs/091 104s ...  - output mismatch (see /root/xfstests/results//xfs/091.out.bad)
>     --- tests/xfs/091.out       2016-07-18 02:57:47.670000000 -0400
>     +++ /root/xfstests/results//xfs/091.out.bad 2016-08-03 22:38:14.948000000 -0400
>     @@ -6,6 +6,70 @@
>      + corrupt image
>      + mount image
>      + modify files
>     +pwrite64: Structure needs cleaning
>     +pwrite64: Structure needs cleaning
>     +pwrite64: Structure needs cleaning
>     +pwrite64: Structure needs cleaning
>     ...
>     (Run 'diff -u tests/xfs/091.out /root/xfstests/results//xfs/091.out.bad'  to see the entire diff)
> Ran: xfs/091
> Failures: xfs/091
> Failed 1 of 1 tests
>
> # diff -u xfstests/tests/xfs/091.out /root/xfstests/results//xfs/091.out.bad
> --- xfstests/tests/xfs/091.out  2016-07-18 02:57:47.670000000 -0400
> +++ /root/xfstests/results//xfs/091.out.bad     2016-08-03 22:38:14.948000000 -0400
> @@ -6,6 +6,70 @@
>  + corrupt image
>  + mount image
>  + modify files
> +pwrite64: Structure needs cleaning
> <snip 62 more same lines>
> +pwrite64: Structure needs cleaning
>  + repair fs
>  + mount image
>  + chattr -R -i
>
>
> Thanks,
> Xiong
>
> _______________________________________________
> Linux-nvdimm mailing list
> Linux-nvdimm@lists.01.org
> https://lists.01.org/mailman/listinfo/linux-nvdimm

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#1472205

From"Darrick J. Wong" <darrick.wong@oracle.com>
Date2016-08-30 04:40 +0200
Message-ID<sbH7X-7gh-1@gated-at.bofh.it>
In reply to#1472194
On Mon, Aug 29, 2016 at 06:50:05PM -0700, Dan Williams wrote:
> [ Adding Darrick on the off chance that this triggers an "aha, of
> course it does!" ]

Aha!  Of course it does!!! :)

> Darrick these corruption tests you added to xfstests last year all
> fail the same way with DAX enabled.  They spew:
> 
>     "pwrite64: Structure needs cleaning"
> 
> ...reports that are cleaned up by running without "-o dax".

I think this happens because in non-dax mode, the pwrite is a buffered
write and so long as we can create a delalloc reservation, everything
is ok and nothing fails.  Whereas for dax we have to allocate the
blocks for the pwrite immediately, thereby triggering the cntbt
verifier error.

Proceeding from the assumption "DAX behaves a lot like DIO", all the
tests that rely on buffered mode semantics are going to choke if DAX
is turned on without them knowing about it.

> Alternatively you could sit back and watch me try to figure it out,
> that should be quite entertaining... as a start I'll try to pin down a
> stack trace when the error is returned.

As for how to fix this, probably the best option is to change line 98
to 'pwrite -W -S 0x62...' and update the output to include the
'structure needs cleaning' message.

Or get rid of the mount option and require explicitly turning on DAX
on a per-inode basis, which I think is where Dave is already going.

--D

> 
> 
> On Wed, Aug 3, 2016 at 7:45 PM, Xiong Zhou <xzhou@redhat.com> wrote:
> > Hi,
> >
> > A few xfs fuzzers in xfstests fail with dax mount option, pass without dax.
> > They are xfs/086 xfs/088 xfs/089 xfs/091.
> >
> > xfstests to commit 4470ad4c7e  (Jul 26)
> > kernel   to commit dd95069545  (Jul 24)
> >
> > + ./check xfs/091
> > FSTYP         -- xfs (non-debug)
> > PLATFORM      -- Linux/x86_64 rhel73 4.7.0+
> > MKFS_OPTIONS  -- -f -bsize=4096 /dev/pmem1
> > MOUNT_OPTIONS -- -o context=system_u:object_r:nfs_t:s0 /dev/pmem1 /daxsch
> >
> > xfs/091  104s
> > Ran: xfs/091
> > Passed all 1 tests
> >
> > + echo 'MOUNT_OPTIONS="-o dax"'
> > + ./check xfs/091
> > FSTYP         -- xfs (non-debug)
> > PLATFORM      -- Linux/x86_64 rhel73 4.7.0+
> > MKFS_OPTIONS  -- -f -bsize=4096 /dev/pmem1
> > MOUNT_OPTIONS -- -o dax -o context=system_u:object_r:nfs_t:s0 /dev/pmem1 /daxsch
> >
> > xfs/091 104s ...  - output mismatch (see /root/xfstests/results//xfs/091.out.bad)
> >     --- tests/xfs/091.out       2016-07-18 02:57:47.670000000 -0400
> >     +++ /root/xfstests/results//xfs/091.out.bad 2016-08-03 22:38:14.948000000 -0400
> >     @@ -6,6 +6,70 @@
> >      + corrupt image
> >      + mount image
> >      + modify files
> >     +pwrite64: Structure needs cleaning
> >     +pwrite64: Structure needs cleaning
> >     +pwrite64: Structure needs cleaning
> >     +pwrite64: Structure needs cleaning
> >     ...
> >     (Run 'diff -u tests/xfs/091.out /root/xfstests/results//xfs/091.out.bad'  to see the entire diff)
> > Ran: xfs/091
> > Failures: xfs/091
> > Failed 1 of 1 tests
> >
> > # diff -u xfstests/tests/xfs/091.out /root/xfstests/results//xfs/091.out.bad
> > --- xfstests/tests/xfs/091.out  2016-07-18 02:57:47.670000000 -0400
> > +++ /root/xfstests/results//xfs/091.out.bad     2016-08-03 22:38:14.948000000 -0400
> > @@ -6,6 +6,70 @@
> >  + corrupt image
> >  + mount image
> >  + modify files
> > +pwrite64: Structure needs cleaning
> > <snip 62 more same lines>
> > +pwrite64: Structure needs cleaning
> >  + repair fs
> >  + mount image
> >  + chattr -R -i
> >
> >
> > Thanks,
> > Xiong
> >
> > _______________________________________________
> > Linux-nvdimm mailing list
> > Linux-nvdimm@lists.01.org
> > https://lists.01.org/mailman/listinfo/linux-nvdimm
> 
> _______________________________________________
> xfs mailing list
> xfs@oss.sgi.com
> http://oss.sgi.com/mailman/listinfo/xfs

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#1472534

FromDan Williams <dan.j.williams@intel.com>
Date2016-08-30 17:00 +0200
Message-ID<sbSG5-6ew-27@gated-at.bofh.it>
In reply to#1472205
On Mon, Aug 29, 2016 at 7:37 PM, Darrick J. Wong
<darrick.wong@oracle.com> wrote:
> On Mon, Aug 29, 2016 at 06:50:05PM -0700, Dan Williams wrote:
>> [ Adding Darrick on the off chance that this triggers an "aha, of
>> course it does!" ]
>
> Aha!  Of course it does!!! :)

Heh, thanks :).  And apologies to Dave for missing his earlier note
pointing out the delalloc failure, linux-nvdimm list ate the response.

>
>> Darrick these corruption tests you added to xfstests last year all
>> fail the same way with DAX enabled.  They spew:
>>
>>     "pwrite64: Structure needs cleaning"
>>
>> ...reports that are cleaned up by running without "-o dax".
>
> I think this happens because in non-dax mode, the pwrite is a buffered
> write and so long as we can create a delalloc reservation, everything
> is ok and nothing fails.  Whereas for dax we have to allocate the
> blocks for the pwrite immediately, thereby triggering the cntbt
> verifier error.
>
> Proceeding from the assumption "DAX behaves a lot like DIO", all the
> tests that rely on buffered mode semantics are going to choke if DAX
> is turned on without them knowing about it.
>
>> Alternatively you could sit back and watch me try to figure it out,
>> that should be quite entertaining... as a start I'll try to pin down a
>> stack trace when the error is returned.
>
> As for how to fix this, probably the best option is to change line 98
> to 'pwrite -W -S 0x62...' and update the output to include the
> 'structure needs cleaning' message.

I'll give it a shot.

> Or get rid of the mount option and require explicitly turning on DAX
> on a per-inode basis, which I think is where Dave is already going.

Yes, I think we can't run away from the dax mount option fast enough.
The semantics are different, so an application / administrator needs
to explicitly opt-in to DAX semantics per-inode otherwise we are
guaranteed to cause surprises.

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#1472617

FromDan Williams <dan.j.williams@intel.com>
Date2016-08-30 18:30 +0200
Message-ID<sbU5b-7gZ-9@gated-at.bofh.it>
In reply to#1472534
On Tue, Aug 30, 2016 at 7:53 AM, Dan Williams <dan.j.williams@intel.com> wrote:
> On Mon, Aug 29, 2016 at 7:37 PM, Darrick J. Wong
> <darrick.wong@oracle.com> wrote:
>> On Mon, Aug 29, 2016 at 06:50:05PM -0700, Dan Williams wrote:
>>> [ Adding Darrick on the off chance that this triggers an "aha, of
>>> course it does!" ]
>>
>> Aha!  Of course it does!!! :)
>
> Heh, thanks :).  And apologies to Dave for missing his earlier note
> pointing out the delalloc failure, linux-nvdimm list ate the response.
>
>>
>>> Darrick these corruption tests you added to xfstests last year all
>>> fail the same way with DAX enabled.  They spew:
>>>
>>>     "pwrite64: Structure needs cleaning"
>>>
>>> ...reports that are cleaned up by running without "-o dax".
>>
>> I think this happens because in non-dax mode, the pwrite is a buffered
>> write and so long as we can create a delalloc reservation, everything
>> is ok and nothing fails.  Whereas for dax we have to allocate the
>> blocks for the pwrite immediately, thereby triggering the cntbt
>> verifier error.
>>
>> Proceeding from the assumption "DAX behaves a lot like DIO", all the
>> tests that rely on buffered mode semantics are going to choke if DAX
>> is turned on without them knowing about it.
>>
>>> Alternatively you could sit back and watch me try to figure it out,
>>> that should be quite entertaining... as a start I'll try to pin down a
>>> stack trace when the error is returned.
>>
>> As for how to fix this, probably the best option is to change line 98
>> to 'pwrite -W -S 0x62...' and update the output to include the
>> 'structure needs cleaning' message.
>
> I'll give it a shot.

So, that did not modulate the failure or the passing case.  However,
using -d at line 122 makes the no-dax case fail the same as the dax
case.

Would a change like this be acceptable in the interim while we figure
out which tests are delalloc sensitive, or did I just invalidate the
test?

diff --git a/tests/xfs/086 b/tests/xfs/086
index 143915bafaa1..26607c7a4697 100755
--- a/tests/xfs/086
+++ b/tests/xfs/086
@@ -96,7 +96,7 @@ _scratch_mount

 echo "+ modify files"
 for x in `seq 1 64`; do
-       $XFS_IO_PROG -f -c "pwrite -S 0x62 0 ${blksz}"
"${TESTFILE}.${x}" >> $seqres.full
+       $XFS_IO_PROG -f -c "pwrite -d -S 0x62 0 ${blksz}"
"${TESTFILE}.${x}" >> $seqres.full
 done
 umount "${SCRATCH_MNT}"

@@ -119,7 +119,7 @@ echo "broken: ${broken}"
 # Try appending again, now that we've fixed the fs
 echo "+ modify files (2)"
 for x in `seq 1 64`; do
-       $XFS_IO_PROG -f -c "pwrite -S 0x62 ${blksz} ${blksz}"
"${TESTFILE}.${x}" >> $seqres.fu
+       $XFS_IO_PROG -f -c "pwrite -d -S 0x62 ${blksz} ${blksz}"
"${TESTFILE}.${x}" >> $seqres
 done
 umount "${SCRATCH_MNT}"

diff --git a/tests/xfs/086.out b/tests/xfs/086.out
index 6c053f42deea..e2ec84e6b90f 100644
--- a/tests/xfs/086.out
+++ b/tests/xfs/086.out
@@ -16,5 +16,5 @@ broken: 1
 + mount image
 + chattr -R -i
 + check files (2)
-broken: 0
+broken: 1
 + check fs (2)

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#1472637

From"Darrick J. Wong" <darrick.wong@oracle.com>
Date2016-08-30 18:50 +0200
Message-ID<sbUox-7nH-23@gated-at.bofh.it>
In reply to#1472617
On Tue, Aug 30, 2016 at 09:25:45AM -0700, Dan Williams wrote:
> On Tue, Aug 30, 2016 at 7:53 AM, Dan Williams <dan.j.williams@intel.com> wrote:
> > On Mon, Aug 29, 2016 at 7:37 PM, Darrick J. Wong
> > <darrick.wong@oracle.com> wrote:
> >> On Mon, Aug 29, 2016 at 06:50:05PM -0700, Dan Williams wrote:
> >>> [ Adding Darrick on the off chance that this triggers an "aha, of
> >>> course it does!" ]
> >>
> >> Aha!  Of course it does!!! :)
> >
> > Heh, thanks :).  And apologies to Dave for missing his earlier note
> > pointing out the delalloc failure, linux-nvdimm list ate the response.
> >
> >>
> >>> Darrick these corruption tests you added to xfstests last year all
> >>> fail the same way with DAX enabled.  They spew:
> >>>
> >>>     "pwrite64: Structure needs cleaning"
> >>>
> >>> ...reports that are cleaned up by running without "-o dax".
> >>
> >> I think this happens because in non-dax mode, the pwrite is a buffered
> >> write and so long as we can create a delalloc reservation, everything
> >> is ok and nothing fails.  Whereas for dax we have to allocate the
> >> blocks for the pwrite immediately, thereby triggering the cntbt
> >> verifier error.
> >>
> >> Proceeding from the assumption "DAX behaves a lot like DIO", all the
> >> tests that rely on buffered mode semantics are going to choke if DAX
> >> is turned on without them knowing about it.
> >>
> >>> Alternatively you could sit back and watch me try to figure it out,
> >>> that should be quite entertaining... as a start I'll try to pin down a
> >>> stack trace when the error is returned.
> >>
> >> As for how to fix this, probably the best option is to change line 98
> >> to 'pwrite -W -S 0x62...' and update the output to include the
> >> 'structure needs cleaning' message.
> >
> > I'll give it a shot.
> 
> So, that did not modulate the failure or the passing case.  However,
> using -d at line 122 makes the no-dax case fail the same as the dax
> case.
> 
> Would a change like this be acceptable in the interim while we figure
> out which tests are delalloc sensitive, or did I just invalidate the
> test?
> 
> diff --git a/tests/xfs/086 b/tests/xfs/086
> index 143915bafaa1..26607c7a4697 100755
> --- a/tests/xfs/086
> +++ b/tests/xfs/086
> @@ -96,7 +96,7 @@ _scratch_mount
> 
>  echo "+ modify files"
>  for x in `seq 1 64`; do
> -       $XFS_IO_PROG -f -c "pwrite -S 0x62 0 ${blksz}"
> "${TESTFILE}.${x}" >> $seqres.full
> +       $XFS_IO_PROG -f -c "pwrite -d -S 0x62 0 ${blksz}"
> "${TESTFILE}.${x}" >> $seqres.full
>  done
>  umount "${SCRATCH_MNT}"
> 
> @@ -119,7 +119,7 @@ echo "broken: ${broken}"
>  # Try appending again, now that we've fixed the fs
>  echo "+ modify files (2)"
>  for x in `seq 1 64`; do
> -       $XFS_IO_PROG -f -c "pwrite -S 0x62 ${blksz} ${blksz}"
> "${TESTFILE}.${x}" >> $seqres.fu
> +       $XFS_IO_PROG -f -c "pwrite -d -S 0x62 ${blksz} ${blksz}"
> "${TESTFILE}.${x}" >> $seqres
>  done
>  umount "${SCRATCH_MNT}"
> 
> diff --git a/tests/xfs/086.out b/tests/xfs/086.out
> index 6c053f42deea..e2ec84e6b90f 100644
> --- a/tests/xfs/086.out
> +++ b/tests/xfs/086.out
> @@ -16,5 +16,5 @@ broken: 1
>  + mount image
>  + chattr -R -i
>  + check files (2)
> -broken: 0
> +broken: 1

There shouldn't be any brokenness left over at this point in the test.

--D

>  + check fs (2)

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