Re: [PATCH v1] selftests/mm: fix charge_reserved_hugetlb.sh test

[David Hildenbrand <david@redhat.com>]

On 21.08.24 17:59, Mina Almasry wrote:
> On Wed, Aug 21, 2024 at 8:31 AM David Hildenbrand <david@redhat.com> wrote:
>>
>> Currently, running the charge_reserved_hugetlb.sh selftest we can
>> sometimes observe something like:
>>
>>    $ ./charge_reserved_hugetlb.sh -cgroup-v2
>>    ...
>>    write_result is 0
>>    After write:
>>    hugetlb_usage=0
>>    reserved_usage=10485760
>>    killing write_to_hugetlbfs
>>    Received 2.
>>    Deleting the memory
>>    Detach failure: Invalid argument
>>    umount: /mnt/huge: target is busy.
>>
>> Both cases are issues in the test.
>>
>> While the unmount error seems to be racy, it will make the test fail:
>>          $ ./run_vmtests.sh -t hugetlb
>>          ...
>>          # [FAIL]
>>          not ok 10 charge_reserved_hugetlb.sh -cgroup-v2 # exit=32
>>
>> The issue is that we are not waiting for the write_to_hugetlbfs process
>> to quit. So it might still have a hugetlbfs file open, about which
>> umount is not happy. Fix that by making "killall" wait for the process
>> to quit.
>>
>> The other error ("Detach failure: Invalid argument") does not seem to
>> result in a test error, but is misleading. Turns out write_to_hugetlbfs.c
>> unconditionally tries to cleanup using shmdt(), even when we only
>> mmap()'ed a hugetlb file. Even worse, shmaddr is never even set for the
>> SHM case. Fix that as well.
>>
>> With this change it seems to work as expected.
>>
>> Fixes: 29750f71a9b4 ("hugetlb_cgroup: add hugetlb_cgroup reservation tests")
>> Reported-by: Mario Casquero <mcasquer@redhat.com>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Shuah Khan <shuah@kernel.org>
>> Cc: Muchun Song <muchun.song@linux.dev>
>> Cc: Mina Almasry <almasrymina@google.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
> 
> Initially I thought it could be nice to split fixes for the 2 issues
> in separate patches in case one of them ends up needing a revert or
> something, but probably not worth a respin. Fixes look good to me.

I was debating with myself as well if it should be separated, but 
decided to go the simple route of a single patch :)

> 
> Reviewed-by: Mina Almasry <almasrymina@google.com>

Thanks!

-- 
Cheers,

David / dhildenb