Re: [PATCH mm-hotfixes] mm/huge_memory: use correct flags for device private PMD entry

[Lorenzo Stoakes <ljs@kernel.org>]

On Mon, Jun 01, 2026 at 09:30:44AM +0100, Lorenzo Stoakes wrote:
>  mm/huge_memory.c | 45 +++++++++++++++++++++++++++++++++------------
>  1 file changed, 33 insertions(+), 12 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index bf9b480bb3b0..79463c709c98 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -4982,7 +4982,7 @@ int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
>  	struct vm_area_struct *vma = pvmw->vma;
>  	struct mm_struct *mm = vma->vm_mm;
>  	unsigned long address = pvmw->address;
> -	bool anon_exclusive;
> +	bool anon_exclusive, present, writable, softdirty, uffd_wp;
>  	pmd_t pmdval;
>  	swp_entry_t entry;
>  	pmd_t pmdswp;
> @@ -4990,12 +4990,26 @@ int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
>  	if (!(pvmw->pmd && !pvmw->pte))
>  		return 0;
>
> -	flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
> -	if (unlikely(!pmd_present(*pvmw->pmd)))
> -		pmdval = pmdp_huge_get_and_clear(vma->vm_mm, address, pvmw->pmd);
> -	else
> +	present = pmd_present(*pvmw->pmd);
> +	if (likely(present)) {
> +		flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);

Oh I forgot to mention in the commit message that I moved
flush_cache_range() into the present branch, as it's not meaningful for a
softleaf (i.e. non-present) entry.

Cheers, Lorenzo