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

Pratyush Yadav posted 2 patches 3 weeks, 1 day ago
[PATCH v2 1/2] kho: use unsigned long for nr_pages
Posted by Pratyush Yadav 3 weeks, 1 day ago 
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>
---

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
Re: [PATCH v2 1/2] kho: use unsigned long for nr_pages
Posted by Pasha Tatashin 2 weeks, 2 days ago 
> @@ -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)

Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Re: [PATCH v2 1/2] kho: use unsigned long for nr_pages
Posted by Mike Rapoport 2 weeks, 4 days ago 
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.
Re: [PATCH v2 1/2] kho: use unsigned long for nr_pages
Posted by Andrew Morton 3 weeks, 1 day ago 
On Fri, 16 Jan 2026 11:22:14 +0000 Pratyush Yadav <pratyush@kernel.org> 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.

We can expect people to be using LTS kernel five years from now,
perhaps much longer.  Machines will be bigger then!

IOW, shouldn't we backport this?
Re: [PATCH v2 1/2] kho: use unsigned long for nr_pages
Posted by Mike Rapoport 2 weeks, 4 days ago 
On Fri, Jan 16, 2026 at 02:26:35PM -0800, Andrew Morton wrote:
> On Fri, 16 Jan 2026 11:22:14 +0000 Pratyush Yadav <pratyush@kernel.org> 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.
> 
> We can expect people to be using LTS kernel five years from now,
> perhaps much longer.  Machines will be bigger then!
> 
> IOW, shouldn't we backport this?

The latest LTS is 6.12 that still does not have KHO, I don't think it makes
sense to backport this to 6.18.

-- 
Sincerely yours,
Mike.

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