Re: [PATCH v2 1/2] kho: use unsigned long for nr_pages

[Mike Rapoport <rppt@kernel.org>]

On Fri, Jan 16, 2026 at 11:22:14AM +0000, Pratyush Yadav wrote:
> With 4k pages, a 32-bit nr_pages can span up to 16 TiB. While it is a
> lot, there exist systems with terabytes of RAM. gup is also moving to
> using long for nr_pages. Use unsigned long and make KHO future-proof.
> 
> Suggested-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> Signed-off-by: Pratyush Yadav <pratyush@kernel.org>

Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

> ---
> 
> Changes in v2:
> - New in v2.
> 
>  include/linux/kexec_handover.h     |  6 +++---
>  kernel/liveupdate/kexec_handover.c | 11 ++++++-----
>  2 files changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/kexec_handover.h b/include/linux/kexec_handover.h
> index 5f7b9de97e8d..81814aa92370 100644
> --- a/include/linux/kexec_handover.h
> +++ b/include/linux/kexec_handover.h
> @@ -45,15 +45,15 @@ bool is_kho_boot(void);
>  
>  int kho_preserve_folio(struct folio *folio);
>  void kho_unpreserve_folio(struct folio *folio);
> -int kho_preserve_pages(struct page *page, unsigned int nr_pages);
> -void kho_unpreserve_pages(struct page *page, unsigned int nr_pages);
> +int kho_preserve_pages(struct page *page, unsigned long nr_pages);
> +void kho_unpreserve_pages(struct page *page, unsigned long nr_pages);
>  int kho_preserve_vmalloc(void *ptr, struct kho_vmalloc *preservation);
>  void kho_unpreserve_vmalloc(struct kho_vmalloc *preservation);
>  void *kho_alloc_preserve(size_t size);
>  void kho_unpreserve_free(void *mem);
>  void kho_restore_free(void *mem);
>  struct folio *kho_restore_folio(phys_addr_t phys);
> -struct page *kho_restore_pages(phys_addr_t phys, unsigned int nr_pages);
> +struct page *kho_restore_pages(phys_addr_t phys, unsigned long nr_pages);
>  void *kho_restore_vmalloc(const struct kho_vmalloc *preservation);
>  int kho_add_subtree(const char *name, void *fdt);
>  void kho_remove_subtree(void *fdt);
> diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
> index 9dc51fab604f..709484fbf9fd 100644
> --- a/kernel/liveupdate/kexec_handover.c
> +++ b/kernel/liveupdate/kexec_handover.c
> @@ -222,7 +222,8 @@ static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn,
>  static struct page *kho_restore_page(phys_addr_t phys, bool is_folio)
>  {
>  	struct page *page = pfn_to_online_page(PHYS_PFN(phys));
> -	unsigned int nr_pages, ref_cnt;
> +	unsigned long nr_pages;
> +	unsigned int ref_cnt;
>  	union kho_page_info info;
>  
>  	if (!page)
> @@ -249,7 +250,7 @@ static struct page *kho_restore_page(phys_addr_t phys, bool is_folio)
>  	 * count of 1
>  	 */
>  	ref_cnt = is_folio ? 0 : 1;
> -	for (unsigned int i = 1; i < nr_pages; i++)
> +	for (unsigned long i = 1; i < nr_pages; i++)
>  		set_page_count(page + i, ref_cnt);
>  
>  	if (is_folio && info.order)
> @@ -283,7 +284,7 @@ EXPORT_SYMBOL_GPL(kho_restore_folio);
>   *
>   * Return: 0 on success, error code on failure
>   */
> -struct page *kho_restore_pages(phys_addr_t phys, unsigned int nr_pages)
> +struct page *kho_restore_pages(phys_addr_t phys, unsigned long nr_pages)
>  {
>  	const unsigned long start_pfn = PHYS_PFN(phys);
>  	const unsigned long end_pfn = start_pfn + nr_pages;
> @@ -829,7 +830,7 @@ EXPORT_SYMBOL_GPL(kho_unpreserve_folio);
>   *
>   * Return: 0 on success, error code on failure
>   */
> -int kho_preserve_pages(struct page *page, unsigned int nr_pages)
> +int kho_preserve_pages(struct page *page, unsigned long nr_pages)
>  {
>  	struct kho_mem_track *track = &kho_out.track;
>  	const unsigned long start_pfn = page_to_pfn(page);
> @@ -873,7 +874,7 @@ EXPORT_SYMBOL_GPL(kho_preserve_pages);
>   * kho_preserve_pages() call. Unpreserving arbitrary sub-ranges of larger
>   * preserved blocks is not supported.
>   */
> -void kho_unpreserve_pages(struct page *page, unsigned int nr_pages)
> +void kho_unpreserve_pages(struct page *page, unsigned long nr_pages)
>  {
>  	struct kho_mem_track *track = &kho_out.track;
>  	const unsigned long start_pfn = page_to_pfn(page);
> -- 
> 2.52.0.457.g6b5491de43-goog
> 

-- 
Sincerely yours,
Mike.