Re: [PATCH 05/13] selftests/mm: size tmpfs according to PMD page size in split_huge_page_test

[Zi Yan <ziy@nvidia.com>]

On 10 Mar 2026, at 5:49, Sayali Patil wrote:

> The split_file_backed_thp() test mounts a tmpfs with a fixed size of
> "4m". This works on systems with smaller PMD page sizes,
> but fails on configurations where the PMD huge page size is
> larger (e.g. 16MB).
>
> On such systems, the fixed 4MB tmpfs is insufficient to allocate even
> a single PMD-sized THP, causing the test to fail.
>
> Fix this by sizing the tmpfs dynamically based on the runtime
> pmd_pagesize, allocating space for two PMD-sized pages.
>
> Before patch:
>   running ./split_huge_page_test /tmp/xfs_dir_YTrI5E
>   --------------------------------------------------
>   TAP version 13
>   1..55
>   ok 1 Split zero filled huge pages successful
>   ok 2 Split huge pages to order 0 successful
>   ok 3 Split huge pages to order 2 successful
>   ok 4 Split huge pages to order 3 successful
>   ok 5 Split huge pages to order 4 successful
>   ok 6 Split huge pages to order 5 successful
>   ok 7 Split huge pages to order 6 successful
>   ok 8 Split huge pages to order 7 successful
>   ok 9 Split PTE-mapped huge pages successful
>    Please enable pr_debug in split_huge_pages_in_file() for more info.
>    Failed to write data to testing file: Success (0)
>   Bail out! Error occurred
>    Planned tests != run tests (55 != 9)
>    Totals: pass:9 fail:0 xfail:0 xpass:0 skip:0 error:0
>  [FAIL]
>
> After patch:
>   --------------------------------------------------
>   running ./split_huge_page_test /tmp/xfs_dir_bMvj6o
>   --------------------------------------------------
>   TAP version 13
>   1..55
>   ok 1 Split zero filled huge pages successful
>   ok 2 Split huge pages to order 0 successful
>   ok 3 Split huge pages to order 2 successful
>   ok 4 Split huge pages to order 3 successful
>   ok 5 Split huge pages to order 4 successful
>   ok 6 Split huge pages to order 5 successful
>   ok 7 Split huge pages to order 6 successful
>   ok 8 Split huge pages to order 7 successful
>   ok 9 Split PTE-mapped huge pages successful
>    Please enable pr_debug in split_huge_pages_in_file() for more info.
>    Please check dmesg for more information
>   ok 10 File-backed THP split to order 0 test done
>    Please enable pr_debug in split_huge_pages_in_file() for more info.
>    Please check dmesg for more information
>   ok 11 File-backed THP split to order 1 test done
>    Please enable pr_debug in split_huge_pages_in_file() for more info.
>    Please check dmesg for more information
>   ok 12 File-backed THP split to order 2 test done
> ...
>   ok 55 Split PMD-mapped pagecache folio to order 7 at
>     in-folio offset 128 passed
>    Totals: pass:55 fail:0 xfail:0 xpass:0 skip:0 error:0
>    [PASS]
> ok 1 split_huge_page_test /tmp/xfs_dir_bMvj6o
>
> Fixes: fbe37501b252 ("mm: huge_memory: debugfs for file-backed THP split")
> Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
> ---
>  tools/testing/selftests/mm/split_huge_page_test.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
Thanks for fixing it.

Reviewed-by: Zi Yan <ziy@nvidia.com>

Best Regards,
Yan, Zi