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Subject: Re: [PATCH] btrfs/029: fix wrong usage of name filter
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From: "Misono, Tomohiro" <misono.tomohiro@jp.fujitsu.com>
Message-ID: <7ec7d078-9a33-91ca-ea68-652f58fb5d41@jp.fujitsu.com>
Date: Fri, 1 Sep 2017 09:44:59 +0900
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To: Eryu Guan <eguan@redhat.com>
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On 2017/08/31 16:33, Eryu Guan wrote:
> On Thu, Aug 31, 2017 at 08:53:09AM +0900, Misono, Tomohiro wrote:
>> On 2017/08/30 20:09, Eryu Guan wrote:
>>> On Wed, Aug 30, 2017 at 04:38:16PM +0900, Misono, Tomohiro wrote:
>>>> btrfs/029 uses _filter_testdirs() to filter the name of $TEST_DIR and
>>>> $SCRATCH_MNT directory.
>>>>
>>>> In this function, it calls both _filter_test_dir and _filter_scratch
>>>> concatenapted by pipe. Therefore if $TEST_DIR is a prefix of
>>>> $SCRATCH_MNT, this filter function gives wrong filtered name for
>>>> $SCRATCH_MNT and the test fails.
>>>
>>> Sorry, I'm a bit confused, how could $TEST_DIR be a prefix of
>>> $SCRATCH_MNT? Won't that fail the test at setup time?
>>
>> I used "/mnt" for $TEST_DIR and "/mnt_scratch" for $SCRATCH_MNT and hit
>> this problem because "/mnt_scratch" is filtered to "$TEST_DIR_scrach"
>> instead of "$SCRATCH_MNT".
>>
>> I think these are valid directory names and other btrfs tests run correctly
>> with these names.
> 
> Ah, yes, that's possible and a valid (though not usual) test setup. The
> filter becomes complex when one string is prefix of another string, we
> have similar problems when filtering TEST_DIR vs TEST_DEV and
> SCRATCH_MNT vs SCRATCH_DEV in _filter_test_dir and _filter_scratch.
> 
> But the fix only works around btrfs/029, but there're other places we
> use the two filters together, like in _filter_quota, TEST_DIR filter
> results would be wrong if SCRATCH_MNT is a prefix of TEST_DIR, because
> in _filter_quota it calls _filter_scratch first.
> 
> I think one solution is that we filter the longer string first, e.g.
> move _filter_testdirs to common/filter and update it to something like:
> 
> # filter both test and scratch mount points and devices, but always
> # filter the longer string if the other string is a substring of the
> # first one.
> _filter_testdirs()
> {
> 	if echo "$TEST_DIR" | grep -q "$SCRATCH_MNT"; then
> 		_filter_test_dir | _filter_scratch
> 	else
> 		_filter_scratch | _filter_test_dir
> 	fi
> }
> 
> And use this new helper when needed. I found 4 places that need update,
> they're btrfs/029, generic/409, generic/410, generic/411 and
> _filter_quota().
> 

Ok. I will do that if you won't, though I'm not sure other combination of 
filters would pose the similar problem.

Thanks,
Tomohiro