On 1/31/12 4:41 PM, Dave Chinner wrote:
> On Mon, Jan 30, 2012 at 04:27:51PM -0600, Eric Sandeen wrote:
>> This changes quite a few things about 274 to make it more robust
>> and useful.
>>
>> * More comments
>> * Use xfs_io for falloc (not all systems have /usr/bin/fallocate)
>> * use _require_xfs_io_falloc to be sure system & fs support preallocation
>> * Do not remove all of the files in $SCRATCH_MNT/ post-mkfs
>> * Do not remove all of the files in $SCRATCH_MNT/ on completion
>> (this breaks e2fsck when lost+found/ goes missing)
>
> FWIW, can't e2fsck be fixed to handle this case?
perhaps some day.
but it'd return "modified" if it adds lost+found ...
I suppose it could just be left missing unless otherwise needed.
> ......
>> _cleanup()
>> {
>> cd /
>> - rm -f $SCRATCH_MNT/* $tmp.*
>> + rm -f $tmp.*
>> _scratch_unmount
>> }
>>
>> @@ -46,6 +48,7 @@ _cleanup()
>> _supported_fs generic
>> _supported_os IRIX Linux
>> _require_scratch
>> +_require_xfs_io_falloc
>>
>> echo "------------------------------"
>> echo "preallocation test"
>> @@ -57,32 +60,39 @@ umount $SCRATCH_DEV 2>/dev/null
>> _scratch_mkfs_sized $((1 * 1024 * 1024 * 1024)) >>$seq.full 2>&1
>> _scratch_mount
>>
>> -rm -rf $SCRATCH_MNT/*
>> -cd $SCRATCH_MNT
>> -dd if=/dev/zero of=test bs=4K count=1 >/dev/null 2>&1
>> +# Create a 4k file
>> +dd if=/dev/zero of=$SCRATCH_MNT/test bs=4K count=1 >>$seq.full 2>&1
>> if [ $? -ne 0 ]
>> then
>> - echo "create file err"
>> + echo "create file error"
>> status=1
>> exit
>> fi
>>
>> -fallocate -n -o 4K -l 1M test >/dev/null 2>&1
>> +# Allocate 4M past EOF on that file
>> +xfs_io -F -c "falloc -k 4k 4m" $SCRATCH_MNT/test >>$seq.full 2>&1
>> if [ $? -ne 0 ]
>> then
>> - echo "fallocate file err"
>> + echo "fallocate file error"
>> status=1
>> exit
>> fi
>
> That whole create and falloc step can be done with one command:
>
> xfs_io -F -c "write 0 4k" -c "falloc -k 4k 4m" $SCRATCH_MNT/test
>
> The output of xfs_io will tell us what failed if it does.
>
> Also, failure handling is as simple as appending:
>
> || _fail "failure string"
>
> to the command. It handles setting status appropriately, tees the
> failure string to $seq.full, and tells the user to go look at
> $seq.full for why the test failed. hence that 16 lines of script can
> be simply replaced with these 2 lines:
>
> xfs_io -F -c "write 0 4k" -c "falloc -k 4k 4m" $SCRATCH_MNT/test \
> >>$seq.full 2>&1 || _fail "failed to create test file"
Ok, that's fine.
>> -dd if=/dev/zero of=tmp1 bs=1M >/dev/null 2>&1
>> -dd if=/dev/zero of=tmp2 bs=4K >/dev/null 2>&1
>> +# Fill the rest of the fs completely
>> +dd if=/dev/zero of=$SCRATCH_MNT/tmp1 bs=1M >>$seq.full 2>&1
>> +dd if=/dev/zero of=$SCRATCH_MNT/tmp2 bs=4K >>$seq.full 2>&1
>> sync
>> +# Last effort, use O_SYNC
>> +dd if=/dev/zero of=$SCRATCH_MNT/tmp3 bs=4K oflag=sync >>$seq.full 2>&1
>> +# Save space usage info
>> +echo "Post-fill space:" >> $seq.full
>> +df $SCRATCH_MNT >>$seq.full 2>&1
>>
>> -dd if=/dev/zero of=test seek=1 bs=4K count=2 conv=notrunc >/dev/null 2>&1
>> +# Now attempt a write into all of the preallocated space
>> +dd if=/dev/zero of=$SCRATCH_MNT/test seek=1 bs=4K count=1024 conv=notrunc >>$seq.full 2>&1
>> if [ $? -ne 0 ]
>> then
>> - echo "fill prealloc range err"
>> + echo "fill prealloc range error"
>> status=1
>> exit
>> fi
>
> I'd still like to see this write attempt to trigger nasty behaviours
> like needing to allocate a metadata block for the extent list. I
> suggested randholes, but perhaps this would be easier:
>
> for i in `seq 1 2 1023`; do
> dd if=/dev/zero of=$SCRATCH_MNT/test seek=$i bs=4K count=1 conv=notrunc \
> >>$seq.full 2>&1 || _fail "failed to write test file"
> done
>
> which will write every second block and so only convert every second
> block from unwritten to written and hence blow out the size of the
> extent list and require extent map block allocation and potentially
> trigger ENOSPC that way....
but will also only write half the actual preallocated space. I guess it
depends on what we are trying to test - reservations for metadata or proper
accounting of prealloc'd space itself...?
(and really, what is the proper amount of preallocated metadata space; if
I subbed 2G for 4M, would anything survive the test above?)
-Eric
> Cheers,
>
> Dave.
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