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/
Link: https://docs.kernel.org/mm/highmem.html#temporary-virtual-mappings
Signed-off-by: David Reaver <me@davidreaver.com>
Link: https://patch.msgid.link/20250112152658.20132-1-me@davidreaver.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index c9fb559a63993c9669f9ca6de0ea0704a127e58c..4e6e24e8b85441ffe1ae515db268fe495517a686 100644 (file)
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -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);
 }
 
 /**