Re: [PATCH] common/config: Always create RESULT_BASE

[Nikolay Borisov <nborisov@suse.com>]

On 4.01.19 г. 11:43 ч., Eryu Guan wrote:
> On Fri, Jan 04, 2019 at 08:56:09AM +1100, Dave Chinner wrote:
>> On Thu, Jan 03, 2019 at 02:29:08PM +0200, Nikolay Borisov wrote:
>>>
>>>
>>> On 3.01.19 г. 12:01 ч., Nikolay Borisov wrote:
>>>> Commit 7fc034868d5d ("common/config: create $RESULT_BASE before dumping kmemleak leaks")
>>>> inadvertently broke $RESULT_BASE dir creation since it changed the logic
>>>> to only create the directory only if this variable is not explicitly set
>>>> by the user. Fix this by ensuring RESULT_BASE is always created.
>>>>
>>>> Signed-off-by: Nikolay Borisov <nborisov@suse.com>
>>>
>>> Eryu,
>>>
>>> I think Johannes' commit should actually be reverted. Currently
>>> get_next_config is called at the beginning of the section code _AFTER_
>>> _init_kmemleak so it's not really fixing the problem that Johannes
>>> described. So care to revert his commit ?
>>
>> Yes, the original commit should be reverted. Using RESULT_BASE in
>> the way that init_kmemleak is using it is fundamentally broken.
>> Using RESULTS_BASE is incorrect - harness run state is supposed to
>> be stored in the section-aware RESULTS_DIR (e.g. see
>> _require_scratch()) which is constant and always exists for each
>> section that is run.
>>
>> The code was architectected this way because section definitions can
>> change RESULT_BASE, and that means the RESULT_BASE defined when
>> init_kmemleak() is called may not point to the same location as when
>> check_memleak() is called. Hence check_memleak will never run if a
>> section definition changes RESULT_BASE.
>>
>> IOWs, the init_kmemleak() call needs to be done inside the
>> section iteration loop, after the section config has been parsed and
>> we've determined if the the section will be run. This is where the
>> original code created RESULT_BASE if it didn't exist. Further, all
>> the section run state is then stored in RESULTS_DIR, which is
>> created from the current RESULT_BASE (e.g. see _require_scratch,
>> check_dmesg, etc).
> 
> This makes more sense, thanks for the suggestion!
> 
>>
>> Hence init_kmemleak() and check_kmemleak() should have a scope
>> inside a valid RESULT_DIR path. And once this is done, you can then
>> add a USE_KMEMLEAK section variable to turn kmemleak detection on
>> and off via the config file on a per-section basis.....
>>
>> So, IMO, the correct thing to do here is revert the original broken
>> change and fix the kmemleak infrastructure to be properly aware of
>> config sections.
> 
> I think we can take Nikolay's patch for now so we don't leave
> user-specified RESULT_BASE not created for any longer, and revert it and
> 7fc034868d5d when we rework kmemleak infrastructure.

Actually no, for the following RESULT_BASE pattern: 
RESULT_BASE="$PWD/results/$HOST/$(uname -r)"/$(date +%Y-%m-%d-%H-%M-%N)/


Running a test I can see the following mkdirs happening: 

created RESULT_BASE: /root/xfstests-dev/results/linux/4.12.14-nikbor/2019-01-04-09-48-027249346/
created RESULT_BASE: /root/xfstests-dev/results/linux/4.12.14-nikbor/2019-01-04-09-48-093731409/
created RESULT_BASE: /root/xfstests-dev/results/linux/4.12.14-nikbor/2019-01-04-09-48-093731409/

In my case for every test run it potentially creates 2 directories, where only one is really 
populated with data. This is no good. I will strongly suggest that you revert the original patch and 
let kmemleak be broken rather than piling hacks (which have funky side effects as I have shown above)
or leaving dir creation broken altogether.

While at it you might also consider reverting 074740a32c6a36c5ba7d4be66dd4ee63e9f744f3 until Darick 
(or anyone else interested) properly integrated kmemleak support. 



> 
> Thanks,
> Eryu
>