Date:	Wed, 18 Jan 2012 12:42:26 +0800
From:	Liu Bo <liubo2009@...fujitsu.com>
To:	Eric Sandeen <sandeen@...hat.com>
CC:	xfs-oss <xfs@....sgi.com>,
	ext4 development <linux-ext4@...r.kernel.org>,
	Eryu Guan <eguan@...hat.com>
Subject: Re: [PATCH V2] xfstests: make 275 pass

On 01/18/2012 12:03 PM, Eric Sandeen wrote:
> On 1/17/12 8:42 PM, Liu Bo wrote:
>> On 01/05/2012 04:54 AM, Eric Sandeen wrote:
>>> Ok, this is a significant rework of 275, which made too many
>>> assumptions about details of space usage and failed on several
>>> filesystems (it passed on xfs, but only by accident).
>>>
>>> This new version tries to leave about 256k free, then tries
>>> a single 1M IO, and fails only if 0 bytes are written.
>>>
>>> It also sends a lot more to $seq.full for debugging on failure
>>> and fixes a few other stylistic things.
>>>
>>> Signed-off-by: Eric Sandeen <sandeen@...hat.com>
>>> ---
>>>
>>> diff --git a/275 b/275
>>> index 214262e..8f521f8 100755
>>> --- a/275
>>> +++ b/275
>>> @@ -1,8 +1,8 @@
>>>  #! /bin/bash
>>>  # FS QA Test No. 275
>>>  #
>>> -# The posix write test. when write size is larger than disk free size,
>>> -# should write as more as possible
>>> +# The posix write test.  When write size is larger than disk free size,
>>> +# should write as much as possible until ENOSPC.
>>>  #
>>>  #-----------------------------------------------------------------------
>>>  # Copyright (c) 2011-2012 Fujitsu, Inc.  All Rights Reserved.
>>> @@ -30,13 +30,12 @@ echo "QA output created by $seq"
>>>  
>>>  here=`pwd`
>>>  tmp=/tmp/$$
>>> -status=0    # success is the default!
>>> +status=1    # failure is the default!
>>>  trap "_cleanup; exit \$status" 0 1 2 3 15
>>>  
>>>  _cleanup()
>>>  {
>>>  	cd /
>>> -	rm -f $SCRATCH_MNT/* $tmp.*
>>>  	_scratch_unmount
>>>  }
>>>  
>>> @@ -49,7 +48,7 @@ _supported_os IRIX Linux
>>>  _require_scratch
>>>  
>>>  echo "------------------------------"
>>> -echo "write lack test"
>>> +echo "write until ENOSPC test"
>>>  echo "------------------------------"
>>>  
>>>  rm -f $seq.full
>>> @@ -59,31 +58,38 @@ _scratch_mkfs_sized $((1 * 1024 * 1024 * 1024)) >>$seq.full 2>&1
>>>  _scratch_mount
>>>  
>>>  rm -rf $SCRATCH_MNT/*
>>> -cd $SCRATCH_MNT
>>>  
>>> -dd if=/dev/zero of=tmp1 bs=4K count=1 >/dev/null 2>&1
>>> -if [ $? -ne 0 ]
>>> -then
>>> -	echo "create file err"
>>> -	status=1
>>> -	exit
>>> -fi
>>> +dd if=/dev/zero of=$SCRATCH_MNT/tmp1 bs=256K count=1 >>$seq.full 2>&1
>>> +[ $? -ne 0 ] && _fail "Error creating file"
>>>  
>>> -dd if=/dev/zero of=tmp2 bs=1M >/dev/null 2>&1
>>> -dd if=/dev/zero of=tmp3 bs=4K >/dev/null 2>&1
>>> +# Attempt to completely fill fs
>>> +dd if=/dev/zero of=$SCRATCH_MNT/tmp2 bs=1M >>$seq.full 2>&1
>>>  sync
>>> +dd if=/dev/zero of=$SCRATCH_MNT/tmp3 bs=4K >>$seq.full 2>&1
>>> +sync
>>> +# Last effort, use O_SYNC
>>> +dd if=/dev/zero of=$SCRATCH_MNT/tmp4 bs=4K oflag=sync >>$seq.full 2>&1
>>> +# Save space usage info to the full file
>>> +echo "Pre rm space:" >> $seq.full
>>> +df $SCRATCH_MNT >>$seq.full 2>&1
>>>  
>>> -rm -f tmp1
>>> +# Should leave approx 256k free
>>> +rm -f $SCRATCH_MNT/tmp1
>>>  sync
>>> +echo "Post rm space:" >> $seq.full
>>> +df $SCRATCH_MNT >>$seq.full 2>&1
>>> +_freespace=`df -k $SCRATCH_MNT | tail -n 1 | awk '{print $4}'`
>>> +[ $_freespace -gt 1024 ] && _fail "could not sufficiently fill filesystem"
>>> +
>> I doubt this cause btrfs has a mixed data+meta mode, which means data and metadata can
>> share space, but this mode is only enabled when the filesystem size is less than 1G.
>>
>> We can apply the below to avoid it:
>> -_scratch_mkfs_sized $((1 * 1024 * 1024 * 1024)) >>$seq.full 2>&1
>> +_scratch_mkfs_sized $((2 * 1024 * 1024 * 1024)) >>$seq.full 2>&1
> 
> Ok, I can do that easily enough (assuming scratch space is likely to be at least 2G...)
> 
>>> +# Try a write larger than available space
>>> +dd if=/dev/zero of=$SCRATCH_MNT/tmp1 bs=1M count=1 >>$seq.full 2>&1
>>> +echo "Bytes written until ENOSPC:" >>$seq.full
>>> +du $SCRATCH_MNT/tmp1 >>$seq.full
>>>  
>>> -dd if=/dev/zero of=tmp1 bs=8K count=1 >/dev/null 2>&1
>>> -_filesize=`du tmp1 | awk '{print $1}'`
>>> -if [ $_filesize -ne 4 ]
>>> -then
>>> -	echo "write file err"
>>> -	status=1
>>> -	exit
>>> -fi
>>> +# And at least some of it should succeed.
>>> +_filesize=`du $SCRATCH_MNT/tmp1 | awk '{print $1}'`
>>> +[ $_filesize -eq 0 ] && _fail "write file err: Partial write until enospc failed; wrote 0 bytes."
>>>  
>> And btrfs will check free space first and then decide if it should allocate blocks, so a partial write
>> will fail anyway.
> 
> Ok, I'm not quite clear - will the above be a problem for btrfs or is it ok?
> 

It is ok since it depends on the underlying FS IMO.

thanks,
liubo

> Thanks,
> -Eric
> 
>> Other parts looks good to me :)
>>
>> thanks,
>> liubo
>>
>>>  echo "done"
>>> +status=0
>>>  exit
>>> diff --git a/275.out b/275.out
>>> index 30af43c..69b9d52 100644
>>> --- a/275.out
>>> +++ b/275.out
>>> @@ -1,5 +1,5 @@
>>>  QA output created by 275
>>>  ------------------------------
>>> -write lack test
>>> +write until ENOSPC test
>>>  ------------------------------
>>>  done
>>>
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> 
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