[PATCH v2 14/20] mm: Make hibernate handle unmapped pages

[Rick Edgecombe]

For architectures with CONFIG_ARCH_HAS_SET_ALIAS, pages can be unmapped
briefly on the directmap, even when CONFIG_DEBUG_PAGEALLOC is not
configured. So this changes kernel_map_pages and kernel_page_present to be
defined when CONFIG_ARCH_HAS_SET_ALIAS is defined as well. It also changes
places (page_alloc.c) where those functions are assumed to only be
implemented when CONFIG_DEBUG_PAGEALLOC is defined.

So now when CONFIG_ARCH_HAS_SET_ALIAS=y, hibernate will handle not present
page when saving. Previously this was already done when
CONFIG_DEBUG_PAGEALLOC was configured. It does not appear to have a big
hibernating performance impact.

Before:
[    4.670938] PM: Wrote 171996 kbytes in 0.21 seconds (819.02 MB/s)

After:
[    4.504714] PM: Wrote 178932 kbytes in 0.22 seconds (813.32 MB/s)

Cc: Dave Hansen <dave.hansen at linux.intel.com>
Cc: Andy Lutomirski <luto at kernel.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: "Rafael J. Wysocki" <rjw at rjwysocki.net>
Cc: Pavel Machek <pavel at ucw.cz>
Acked-by: Pavel Machek <pavel at ucw.cz>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe at intel.com>
---
 arch/x86/mm/pageattr.c |  4 ----
 include/linux/mm.h     | 18 ++++++------------
 mm/page_alloc.c        |  7 +++++--
 3 files changed, 11 insertions(+), 18 deletions(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 3a51915a1410..717bdc188aab 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -2257,7 +2257,6 @@ int set_alias_default_noflush(struct page *page)
 	return __set_pages_p(page, 1);
 }
 
-#ifdef CONFIG_DEBUG_PAGEALLOC
 void __kernel_map_pages(struct page *page, int numpages, int enable)
 {
 	if (PageHighMem(page))
@@ -2302,11 +2301,8 @@ bool kernel_page_present(struct page *page)
 	pte = lookup_address((unsigned long)page_address(page), &level);
 	return (pte_val(*pte) & _PAGE_PRESENT);
 }
-
 #endif /* CONFIG_HIBERNATION */
 
-#endif /* CONFIG_DEBUG_PAGEALLOC */
-
 int __init kernel_map_pages_in_pgd(pgd_t *pgd, u64 pfn, unsigned long address,
 				   unsigned numpages, unsigned long page_flags)
 {
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 80bb6408fe73..b362a280a919 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2642,37 +2642,31 @@ static inline void kernel_poison_pages(struct page *page, int numpages,
 					int enable) { }
 #endif
 
-#ifdef CONFIG_DEBUG_PAGEALLOC
 extern bool _debug_pagealloc_enabled;
-extern void __kernel_map_pages(struct page *page, int numpages, int enable);
 
 static inline bool debug_pagealloc_enabled(void)
 {
-	return _debug_pagealloc_enabled;
+	return IS_ENABLED(CONFIG_DEBUG_PAGEALLOC) && _debug_pagealloc_enabled;
 }
 
+#if defined(CONFIG_DEBUG_PAGEALLOC) || defined(CONFIG_ARCH_HAS_SET_ALIAS)
+extern void __kernel_map_pages(struct page *page, int numpages, int enable);
+
 static inline void
 kernel_map_pages(struct page *page, int numpages, int enable)
 {
-	if (!debug_pagealloc_enabled())
-		return;
-
 	__kernel_map_pages(page, numpages, enable);
 }
 #ifdef CONFIG_HIBERNATION
 extern bool kernel_page_present(struct page *page);
 #endif	/* CONFIG_HIBERNATION */
-#else	/* CONFIG_DEBUG_PAGEALLOC */
+#else	/* CONFIG_DEBUG_PAGEALLOC || CONFIG_ARCH_HAS_SET_ALIAS */
 static inline void
 kernel_map_pages(struct page *page, int numpages, int enable) {}
 #ifdef CONFIG_HIBERNATION
 static inline bool kernel_page_present(struct page *page) { return true; }
 #endif	/* CONFIG_HIBERNATION */
-static inline bool debug_pagealloc_enabled(void)
-{
-	return false;
-}
-#endif	/* CONFIG_DEBUG_PAGEALLOC */
+#endif	/* CONFIG_DEBUG_PAGEALLOC || CONFIG_ARCH_HAS_SET_ALIAS */
 
 #ifdef __HAVE_ARCH_GATE_AREA
 extern struct vm_area_struct *get_gate_vma(struct mm_struct *mm);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d295c9bc01a8..92d0a0934274 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1074,7 +1074,9 @@ static __always_inline bool free_pages_prepare(struct page *page,
 	}
 	arch_free_page(page, order);
 	kernel_poison_pages(page, 1 << order, 0);
-	kernel_map_pages(page, 1 << order, 0);
+	if (debug_pagealloc_enabled())
+		kernel_map_pages(page, 1 << order, 0);
+
 	kasan_free_nondeferred_pages(page, order);
 
 	return true;
@@ -1944,7 +1946,8 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
 	set_page_refcounted(page);
 
 	arch_alloc_page(page, order);
-	kernel_map_pages(page, 1 << order, 1);
+	if (debug_pagealloc_enabled())
+		kernel_map_pages(page, 1 << order, 1);
 	kernel_poison_pages(page, 1 << order, 1);
 	kasan_alloc_pages(page, order);
 	set_page_owner(page, order, gfp_flags);
-- 
2.17.1