Re: [PATCH RFC 0/5] Test readback from fd on hugetlbfs mount

[Mike Rapoport <rppt@kernel.org>]

Hi,

On Mon, May 18, 2026 at 11:17:32AM -0700, Ackerley Tng via B4 Relay wrote:
> Hi,
> 
> I'm thinking of consolidating the tests for libhugetlbfs as kernel
> selftests, and to start that off, I picked the simplest test:
> tests/readback.c
> 
> I refactored hugepage-mmap.c to use the kselftest harness, and then used

I made a lot of changes to mm selftests recently:
https://lore.kernel.org/all/20260511162840.375890-1-rppt@kernel.org/

This work is currently in mm.git, please take a look to avoid effort
duplication.

> FIXTURE_VARIANT from the harness to port in testing readback from an fd on
> a hugetlbfs mount.

I didn't look into the patches, but in general I'm not sure that
FIXTURE_VARIANT is such a win for simple tests.
 
> This output shows that the original test behavior was retained for the
> memfd part:
> 
>   # ./hugepage-mmap
>   TAP version 13
>   1..1
>   # Returned address is 0x7f312f200000
>   # First hex is 0
>   # First hex is 3020100
>   ok 1 Read same data
>   # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
> 
>   # ./hugepage-mmap
>   TAP version 13
>   1..1
>   # Starting 1 tests from 1 test cases.
>   #  RUN           hugepage_mmap.read_write ...
>   # hugepage-mmap.c:41:read_write:Returned address is 0x7f19f3a00000
>   # hugepage-mmap.c:54:read_write:First hex is 0
>   # hugepage-mmap.c:59:read_write:First hex is 3020100
>   #            OK  hugepage_mmap.read_write
>   ok 1 hugepage_mmap.read_write
>   # PASSED: 1 / 1 tests passed.
>   # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
> 
> Let me know what you think before I genericize the 2M hugepage size to
> other sizes!
> 
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>
> ---
> Ackerley Tng (5):
>       mm: selftests: Inline check_bytes() function into caller
>       mm: selftests: Inline {read,write}_bytes functions
>       mm: selftests: Refactor hugepage-mmap to use kselftest harness
>       mm: selftests: Update hugepage-mmap to support hugetlbfs mount
>       mm: selftests: Port readback test logic from libhugetlbfs
> 
>  tools/testing/selftests/mm/hugepage-mmap.c | 143 +++++++++++++++++++++--------
>  1 file changed, 105 insertions(+), 38 deletions(-)
> ---
> base-commit: 66edb901bf874d9e0787326ba12d3548b2da8700
> change-id: 20260503-port-hugetlb-selftests-9bc63bde5116
> 
> Best regards,
> --
> Ackerley Tng <ackerleytng@google.com>
> 
> 

-- 
Sincerely yours,
Mike.