[PATCH v1 1/4] PM: hibernate: Add arch specific hooks for hibernate_map/unmap_page

[Vincent Donnefort]

hibernate_map_page() is called from an atomic context. This is
problematic for Arm BBML3 systems where the linear map may contain
blocks and is allowed to split as splitting is a sleepable operation.

Add arch hook so arm64 can define its own implementation without relying
on the direct map.

Signed-off-by: Vincent Donnefort <vdonnefort at google.com>
---
 include/linux/suspend.h |  2 ++
 kernel/power/snapshot.c | 10 ++++++----
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index b02876f1ae38..10fe2298d94e 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -401,6 +401,8 @@ int hibernate_quiet_exec(int (*func)(void *data), void *data);
 int hibernate_resume_nonboot_cpu_disable(void);
 int arch_hibernation_header_save(void *addr, unsigned int max_size);
 int arch_hibernation_header_restore(void *addr);
+void *hibernate_map_page(struct page *page);
+void hibernate_unmap_page(struct page *page);
 
 #else /* CONFIG_HIBERNATION */
 static inline void register_nosave_region(unsigned long b, unsigned long e) {}
diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index b209712cb2c3..b41952f1de2a 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -85,7 +85,7 @@ static inline int hibernate_restore_unprotect_page(void *page_address) {return 0
  * It is still worth to have a warning here if something changes and this
  * will no longer be the case.
  */
-static inline void hibernate_map_page(struct page *page)
+void * __weak hibernate_map_page(struct page *page)
 {
 	if (IS_ENABLED(CONFIG_ARCH_HAS_SET_DIRECT_MAP)) {
 		int ret = set_direct_map_default_noflush(page);
@@ -95,9 +95,10 @@ static inline void hibernate_map_page(struct page *page)
 	} else {
 		debug_pagealloc_map_pages(page, 1);
 	}
+	return page_address(page);
 }
 
-static inline void hibernate_unmap_page(struct page *page)
+void __weak hibernate_unmap_page(struct page *page)
 {
 	if (IS_ENABLED(CONFIG_ARCH_HAS_SET_DIRECT_MAP)) {
 		unsigned long addr = (unsigned long)page_address(page);
@@ -1456,8 +1457,9 @@ static bool safe_copy_page(void *dst, struct page *s_page)
 	if (kernel_page_present(s_page)) {
 		zeros_only = do_copy_page(dst, page_address(s_page));
 	} else {
-		hibernate_map_page(s_page);
-		zeros_only = do_copy_page(dst, page_address(s_page));
+		void *src = hibernate_map_page(s_page);
+
+		zeros_only = do_copy_page(dst, src);
 		hibernate_unmap_page(s_page);
 	}
 	return zeros_only;
-- 
2.55.0.1082.g2b9226bbc0-goog