Re: [PATCH] mm/memory: use folio lock/ref helpers in do_swap_page

[Andrew Morton]

On Tue, 21 Jul 2026 09:33:47 +0800 Hongfu Li <hongfu.li@xxxxxxxxx> wrote:

> From: Hongfu Li <lihongfu@xxxxxxxxxx>
> 
> Replace page-level lock/ref operations with their folio equivalents
> in the device_private migration path of do_swap_page().
> 
> Introduce a local fault_folio to hold page_folio(vmf->page) to avoid
> repeated page_folio() invocations.
> 
> ...
>
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4852,6 +4852,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>  			vmf->page = softleaf_to_page(entry);
>  			ret = remove_device_exclusive_entry(vmf);
>  		} else if (softleaf_is_device_private(entry)) {
> +			struct folio *fault_folio;
> +
>  			if (vmf->flags & FAULT_FLAG_VMA_LOCK) {
>  				/*
>  				 * migrate_to_ram is not yet ready to operate
> @@ -4863,6 +4865,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>  			}
>  
>  			vmf->page = softleaf_to_page(entry);
> +			fault_folio = page_folio(vmf->page);
>  			vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
>  					vmf->address, &vmf->ptl);

AI review thinks we shouldn't be reading vmf->page until after taking
the page table lock:

	https://sashiko.dev/#/patchset/20260721013347.65698-1-hongfu.li@xxxxxxxxx