Re: [PATCH v3] selftests/mm: add folio_split() and filemap_get_entry() race test

[Zi Yan]

On 20 Mar 2026, at 13:53, Lorenzo Stoakes (Oracle) wrote:

> (-cc old email)
>
> On Thu, Mar 19, 2026 at 03:04:08PM -0400, Zi Yan wrote:
>> The added folio_split_race_test is a modified C port of the race condition
>> test from [1]. The test creates shmem huge pages, where the main thread
>> punches holes in the shmem to cause folio_split() in the kernel and
>> a set of 16 threads reads the shmem to cause filemap_get_entry() in the
>> kernel. filemap_get_entry() reads the folio and xarray split by
>> folio_split() locklessly. The original test[2] is written in rust and uses
>> memfd (shmem backed). This C port uses shmem directly and use a single
>> process.
>>
>> Note: the initial rust to C conversion is done by Cursor.
>>
>> Link: https://lore.kernel.org/all/CAKNNEtw5_kZomhkugedKMPOG-sxs5Q5OLumWJdiWXv+C9Yct0w@xxxxxxxxxxxxxx/ [1]
>> Link: https://github.com/dfinity/thp-madv-remove-test [2]
>> Signed-off-by: Bas van Dijk <bas@xxxxxxxxxxx>
>> Signed-off-by: Adam Bratschi-Kaye <adam.bratschikaye@xxxxxxxxxxx>
>> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
>
> No .gitignore entry? :)
>
> (Just saw it flag up locally in git status)
>
> Linus says don't remove, but he doesn't say don't add :P

I did not know about that. The fixup is below. Thank you for pointing it out.

From bd164a7090c0e8b6e3013502c64c161214e38714 Mon Sep 17 00:00:00 2001
From: Zi Yan <ziy@xxxxxxxxxx>
Date: Fri, 20 Mar 2026 13:56:04 -0400
Subject: [PATCH] git: add generated binary into gitignore

Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
 tools/testing/selftests/mm/.gitignore | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/testing/selftests/mm/.gitignore b/tools/testing/selftests/mm/.gitignore
index 83ad9454dd9d1..b0c30c5ee9e30 100644
--- a/tools/testing/selftests/mm/.gitignore
+++ b/tools/testing/selftests/mm/.gitignore
@@ -61,3 +61,4 @@ guard-regions
 merge
 prctl_thp_disable
 rmap
+folio_split_race_test
-- 
2.51.0



Best Regards,
Yan, Zi