linux-kernel - Re: [PATCH v2 1/3] selftests/mm: fix hugepages cleanup too early

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Message-ID: <ad4abcd0-30d1-4683-97ab-abb1d151700f@redhat.com>
Date: Mon, 8 Sep 2025 14:53:51 +0200
From: David Hildenbrand <david@...hat.com>
To: Chunyu Hu <chuhu@...hat.com>, akpm@...ux-foundation.org,
 shuah@...nel.org, linux-mm@...ck.org
Cc: linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
 lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com, vbabka@...e.cz,
 rppt@...nel.org, surenb@...gle.com, mhocko@...e.com
Subject: Re: [PATCH v2 1/3] selftests/mm: fix hugepages cleanup too early

On 08.09.25 14:47, Chunyu Hu wrote:
> The nr_hugepgs variable is used to keep the original nr_hugepages at the
> hugepage setup step at test beginning. After userfaultfd test, a cleaup is
> executed, both /sys/kernel/mm/hugepages/hugepages-*/nr_hugepages and
> /proc/sys//vm/nr_hugepages are reset to 'original' value before userfaultfd
> test starts.
> 
> Issue here is the value used to restore /proc/sys/vm/nr_hugepages is
> nr_hugepgs which is the initial value before the vm_runtests.sh runs, not
> the value before userfaultfd test starts. 'va_high_addr_swith.sh' tests
> runs after that will possibly see no hugepages available for test, and got
> EINVAL when mmap(HUGETLB), making the result invalid.
> 
> And before pkey tests, nr_hugepgs is changed to be used as a temp variable
> to save nr_hugepages before pkey test, and restore it after pkey tests
> finish. The original nr_hugepages value is not tracked anymore, so no way
> to restore it after all tests finish.
> 
> Add a new variable orig_nr_hugepgs to save the original nr_hugepages, and
> and restore it to nr_hugepages after all tests finish. And change to use
> the nr_hugepgs variable to save the /proc/sys/vm/nr_hugeages after hugepage
> setup, it's also the value before userfaultfd test starts, and the correct
> value to be restored after userfaultfd finishes. The va_high_addr_switch.sh
> broken will be resolved.
> 
> Signed-off-by: Chunyu Hu <chuhu@...hat.com>
> 

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Cheers

David / dhildenb