Commit d42044aa authored by David Reaver's avatar David Reaver Committed by Rafael J. Wysocki
Browse files

PM: hibernate: Replace deprecated kmap_atomic() with kmap_local_page() 

kmap_atomic() is deprecated and should be replaced with kmap_local_page()
[1][2]. kmap_local_page() is faster in kernels with HIGHMEM enabled, can
take page faults, and allows preemption.

According to [2], this replacement is safe as long as the code between
kmap_atomic() and kunmap_atomic() does not implicitly depend on disabling
page faults or preemption. In all of the call sites in this patch, the only
thing happening between mapping and unmapping pages is copy_page() calls,
and I don't suspect they depend on disabling page faults or preemption.

Link: https://lwn.net/Articles/836144/ [1]
Link: https://docs.kernel.org/mm/highmem.html#temporary-virtual-mappings

 [2]
Signed-off-by: default avatarDavid Reaver <me@davidreaver.com>
Link: https://patch.msgid.link/20250112152658.20132-1-me@davidreaver.com


Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 0ad2507d

kernel/power/snapshot.c

+8 −8
Original line number Diff line number Diff line
@@ -2270,9 +2270,9 @@ int snapshot_read_next(struct snapshot_handle *handle) 
			 */

			void *kaddr;



			kaddr = kmap_atomic(page);

			kaddr = kmap_local_page(page);

			copy_page(buffer, kaddr);

			kunmap_atomic(kaddr);

			kunmap_local(kaddr);

			handle->buffer = buffer;

		} else {

			handle->buffer = page_address(page);
@@ -2561,9 +2561,9 @@ static void copy_last_highmem_page(void) 
	if (last_highmem_page) {

		void *dst;



		dst = kmap_atomic(last_highmem_page);

		dst = kmap_local_page(last_highmem_page);

		copy_page(dst, buffer);

		kunmap_atomic(dst);

		kunmap_local(dst);

		last_highmem_page = NULL;

	}

}
@@ -2881,13 +2881,13 @@ static inline void swap_two_pages_data(struct page *p1, struct page *p2, 
{

	void *kaddr1, *kaddr2;



	kaddr1 = kmap_atomic(p1);

	kaddr2 = kmap_atomic(p2);

	kaddr1 = kmap_local_page(p1);

	kaddr2 = kmap_local_page(p2);

	copy_page(buf, kaddr1);

	copy_page(kaddr1, kaddr2);

	copy_page(kaddr2, buf);

	kunmap_atomic(kaddr2);

	kunmap_atomic(kaddr1);

	kunmap_local(kaddr2);

	kunmap_local(kaddr1);

}



/**