> > On Jul 14, 2026, at 01:14, Xiangfeng Cai <[email protected]> wrote: > > > > Add a regression test for the list corruption in > > allocate_file_region_entries() fixed by the previous patch > > ("mm/hugetlb: fix list corruption in allocate_file_region_entries()"). > > > > Triggering the bug requires a concurrent reservation operation to drain > > resv->region_cache while allocate_file_region_entries() has dropped > > resv->lock for its GFP_KERNEL allocation, forcing its retry loop to run > > again. As the mmap() and fallocate(PUNCH_HOLE) paths serialise on > > inode_lock, the cache has to be drained by faults from a separate address > > space. The test forks several processes sharing one hugetlb inode via > > memfd_create(MFD_HUGETLB); each mmap()s and faults ranges and punches holes > > to keep the shared resv_map fragmented. > > > > Two modes are provided: > > > > - default: a safe single-process functional check that exercises the buggy > > line without forcing a second loop iteration; safe on any kernel. > > > > - --trigger: the concurrent reproducer, which panics a vulnerable > > CONFIG_DEBUG_LIST=y kernel and is therefore opt-in. It faults pages in, > > so it needs as many free huge pages as the file is large. > > > > Assisted-by: Claude:claude-opus-4-8 > > Signed-off-by: Xiangfeng Cai <[email protected]> > > It looks like this is a regression test case for a very specific instance of > list corruption. > > In my opinion, selftests should focus more on functional testing with clear > expected behaviors and results to users. I don't think it's worth maintaining > a test case for a minor issue like this, especially since code changes happen > so quickly. Once the code evolves, this specific list corruption might never > occur again, and the function itself could even be deleted during a refactor. > > Therefore, I wouldn't recommend adding this as a selftest.
That makes sense to me. This test is quite specific to the previous internal list corruption, so I agree it is probably not a good fit for selftests. I'll drop it. Thanks for the review. Xiangfeng
