[PATCH] ACPI: NVS: replace __get_free_page() with kmalloc()

[Mike Rapoport (Microsoft)]

suspend_nvs_alloc() allocates shadow pages for saving and restoring
ACPI Non-Volatile Storage regions across suspend/resume.

These buffers can be allocated with kmalloc() as there's nothing special
about them to go directly to the page allocator.

kmalloc() provides a better API that does not require ugly casts and
kfree() does not need to know the size of the freed object.

Performance difference between kmalloc() and __get_free_pages() is not
measurable as both allocators take an object/page from a per-CPU list for
fast path allocations.

For the slow path the performance is anyway determined by the amount of
reclaim involved rather than by what allocator is used.

Replace use of __get_free_page() with kmalloc() and free_page() with
kfree().

Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@xxxxxxxxxx
Signed-off-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
---
This is a (tiny) part of larger work of replacing page allocator calls
with kmalloc:

My initial intention a few month ago was to remove ugly casts [1], but then
willy pointed out that Linus objected to something like this [2] and it
looks like more than a decade old technical debt.

[1] https://lore.kernel.org/all/20251018093002.3660549-1-rppt@xxxxxxxxxx/
[2] https://lore.kernel.org/all/CA+55aFwp4iy4rtX2gE2WjBGFL=NxMVnoFeHqYa2j1dYOMMGqxg@xxxxxxxxxxxxxx/ 

Also in git:
https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git gfp-to-kmalloc/acpi
---
 drivers/acpi/nvs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/nvs.c b/drivers/acpi/nvs.c
index 6eaad7dd0241..12aee4102696 100644
--- a/drivers/acpi/nvs.c
+++ b/drivers/acpi/nvs.c
@@ -133,7 +133,7 @@ void suspend_nvs_free(void)
 
 	list_for_each_entry(entry, &nvs_list, node)
 		if (entry->data) {
-			free_page((unsigned long)entry->data);
+			kfree(entry->data);
 			entry->data = NULL;
 			if (entry->kaddr) {
 				if (entry->unmap) {
@@ -156,7 +156,7 @@ int suspend_nvs_alloc(void)
 	struct nvs_page *entry;
 
 	list_for_each_entry(entry, &nvs_list, node) {
-		entry->data = (void *)__get_free_page(GFP_KERNEL);
+		entry->data = kmalloc(PAGE_SIZE, GFP_KERNEL);
 		if (!entry->data) {
 			suspend_nvs_free();
 			return -ENOMEM;

---
base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
change-id: 20260624-b4-acpi-01183daee9b6

Best regards,
--  
Sincerely yours,
Mike.