Re: [PATCH] mm/migrate_device: document folio_get requirement before frozen PMD split

[Zi Yan]

On 6 Mar 2026, at 5:44, Usama Arif wrote:

> split_huge_pmd_address() with freeze=true splits a PMD migration entry
> into PTE migration entries, consuming one folio reference in the
> process.  The folio_get() before it provides this reference.
>
> Add a comment explaining this relationship and a VM_WARN_ON_ONCE to
> catch an unexpected refcount != 1 entry state.
>
> Suggested-by: Zi Yan <ziy@xxxxxxxxxx>
> Signed-off-by: Usama Arif <usama.arif@xxxxxxxxx>
> ---
>  mm/migrate_device.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
Thanks for fixing the logic in my suggestion,

Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>

Best Regards,
Yan, Zi