Re: [PATCH] mm: shmem: ignore sysfs configs for shmem forced collapse

[Lance Yang]

On Fri, Sep 11, 2026 at 12:04:33PM +0800, Baolin Wang wrote:
>According to Documentation/mm/transhuge.rst, MADV_COLLAPSE is expected to
>ignore any THP or mTHP interface settings.
>
>However, after commit 6beeab870e70 ("mm: shmem: move shmem_huge_global_enabled()
>into shmem_allowable_huge_orders()"), performing MADV_COLLAPSE on shmem
>will depend on /sys/.../hugepages-2048kB/shmem_enabled being set to "inherit"
>(although that is the default), which can cause MADV_COLLAPSE to fail
>unexpectedly.
>
>Fix this by returning the result of shmem_huge_global_enabled() directly
>when MADV_COLLAPSE is requested, allowing PMD-order collapse while ignoring
>shmem THP/mTHP settings.
>
>Fixes: 6beeab870e70 ("mm: shmem: move shmem_huge_global_enabled() into shmem_allowable_huge_orders()")
>Reported-by: Kiryl Shutsemau (Meta) <kas@xxxxxxxxxx>
>Closes: https://lore.kernel.org/all/20260908125105.1510704-7-kirill@xxxxxxxxxxxxx/
>Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
>---

With the Fixes tag corrected as Kiryl suggested, LGTM!

Reviewed-by: Lance Yang <lance.yang@xxxxxxxxx>