Commit 20571b18 authored by Pratyush Yadav's avatar Pratyush Yadav Committed by Andrew Morton
Browse files

kho: move sanity checks to kho_restore_page() 

While KHO exposes folio as the primitive externally, internally its
restoration machinery operates on pages.  This can be seen with
kho_restore_folio() for example.  It performs some sanity checks and hands
it over to kho_restore_page() to do the heavy lifting of page restoration.
After the work done by kho_restore_page(), kho_restore_folio() only
converts the head page to folio and returns it.  Similarly,
deserialize_bitmap() operates on the head page directly to store the
order.

Move the sanity checks for valid phys and order from the public-facing
kho_restore_folio() to the private-facing kho_restore_page().  This makes
the boundary between page and folio clearer from KHO's perspective.

While at it, drop the comment above kho_restore_page().  The comment is
misleading now.  The function stopped looking like free_reserved_page()
since 12b9a2c0 ("kho: initialize tail pages for higher order folios
properly"), and now looks even more different.

Link: https://lkml.kernel.org/r/20250917125725.665-1-pratyush@kernel.org


Signed-off-by: default avatarPratyush Yadav <pratyush@kernel.org>
Reviewed-by: default avatarMike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Changyuan Lyu <changyuanl@google.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 0389c305

kernel/kexec_handover.c

+14 −14
Original line number Diff line number Diff line
@@ -183,10 +183,18 @@ static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn, 
	return 0;

}



/* almost as free_reserved_page(), just don't free the page */

static void kho_restore_page(struct page *page, unsigned int order)

static struct page *kho_restore_page(phys_addr_t phys)

{

	unsigned int nr_pages = (1 << order);

	struct page *page = pfn_to_online_page(PHYS_PFN(phys));

	unsigned int nr_pages, order;



	if (!page)

		return NULL;



	order = page->private;

	if (order > MAX_PAGE_ORDER)

		return NULL;

	nr_pages = (1 << order);



	/* Head page gets refcount of 1. */

	set_page_count(page, 1);
@@ -199,6 +207,7 @@ static void kho_restore_page(struct page *page, unsigned int order) 
		prep_compound_page(page, order);



	adjust_managed_page_count(page, nr_pages);

	return page;

}



/**
@@ -209,18 +218,9 @@ static void kho_restore_page(struct page *page, unsigned int order) 
 */

struct folio *kho_restore_folio(phys_addr_t phys)

{

	struct page *page = pfn_to_online_page(PHYS_PFN(phys));

	unsigned long order;



	if (!page)

		return NULL;



	order = page->private;

	if (order > MAX_PAGE_ORDER)

		return NULL;

	struct page *page = kho_restore_page(phys);



	kho_restore_page(page, order);

	return page_folio(page);

	return page ? page_folio(page) : NULL;

}

EXPORT_SYMBOL_GPL(kho_restore_folio);