linux-kernel - Re: [RFC PATCH v3 2/2] selftests: restrictedmem: Check hugepage-ness of shmem file backing restrictedmem fd

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Message-ID: <diqz5ya319rb.fsf@ackerleytng-cloudtop.c.googlers.com>
Date:   Tue, 11 Apr 2023 01:35:20 +0000
From:   Ackerley Tng <ackerleytng@...gle.com>
To:     David Hildenbrand <david@...hat.com>
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Subject: Re: [RFC PATCH v3 2/2] selftests: restrictedmem: Check hugepage-ness
 of shmem file backing restrictedmem fd

David Hildenbrand <david@...hat.com> writes:

> On 01.04.23 01:50, Ackerley Tng wrote:
>> For memfd_restricted() calls without a userspace mount, the backing
>> file should be the shmem mount in the kernel, and the size of backing
>> pages should be as defined by system-wide shmem configuration.

>> If a userspace mount is provided, the size of backing pages should be
>> as defined in the mount.

>> Also includes negative tests for invalid inputs, including fds
>> representing read-only superblocks/mounts.


> When you talk about "hugepage" in this patch, do you mean THP or
> hugetlb? I suspect thp, so it might be better to spell that out. IIRC,
> there are plans to support actual huge pages in the future, at which
> point "hugepage" terminology could be misleading.


Thanks for pointing this out! I've replaced references to hugepage with
thp, please see RFC v4 at
https://lore.kernel.org/lkml/cover.1681176340.git.ackerleytng@google.com/T/

>> Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
>> ---
>>    tools/testing/selftests/Makefile              |   1 +
>>    .../selftests/restrictedmem/.gitignore        |   3 +
>>    .../testing/selftests/restrictedmem/Makefile  |  15 +
>>    .../testing/selftests/restrictedmem/common.c  |   9 +
>>    .../testing/selftests/restrictedmem/common.h  |   8 +
>>    .../restrictedmem_hugepage_test.c             | 486 ++++++++++++++++++
>>    6 files changed, 522 insertions(+)
>>    create mode 100644 tools/testing/selftests/restrictedmem/.gitignore
>>    create mode 100644 tools/testing/selftests/restrictedmem/Makefile
>>    create mode 100644 tools/testing/selftests/restrictedmem/common.c
>>    create mode 100644 tools/testing/selftests/restrictedmem/common.h
>>    create mode 100644  
>> tools/testing/selftests/restrictedmem/restrictedmem_hugepage_test.c

>> ...