[PATCH v2 10/34] kasan, page_alloc: merge kasan_alloc_pages into post_alloc_hook

[andrey.konovalov@linux.dev]

From: Andrey Konovalov <andreyknvl@google.com>

Currently, the code responsible for initializing and poisoning memory in
post_alloc_hook() is scattered across two locations: kasan_alloc_pages()
hook for HW_TAGS KASAN and post_alloc_hook() itself. This is confusing.

This and a few following patches combine the code from these two
locations. Along the way, these patches do a step-by-step restructure
the many performed checks to make them easier to follow.

This patch replaces the only caller of kasan_alloc_pages() with its
implementation.

As kasan_has_integrated_init() is only true when CONFIG_KASAN_HW_TAGS
is enabled, moving the code does no functional changes.

The patch also moves init and init_tags variables definitions out of
kasan_has_integrated_init() clause in post_alloc_hook(), as they have
the same values regardless of what the if condition evaluates to.

This patch is not useful by itself but makes the simplifications in
the following patches easier to follow.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 include/linux/kasan.h |  9 ---------
 mm/kasan/common.c     |  2 +-
 mm/kasan/hw_tags.c    | 22 ----------------------
 mm/page_alloc.c       | 20 +++++++++++++++-----
 4 files changed, 16 insertions(+), 37 deletions(-)

diff --git a/include/linux/kasan.h b/include/linux/kasan.h
index 89a43d8ae4fe..1031070be3f3 100644
--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -94,8 +94,6 @@ static inline bool kasan_hw_tags_enabled(void)
 	return kasan_enabled();
 }
 
-void kasan_alloc_pages(struct page *page, unsigned int order, gfp_t flags);
-
 #else /* CONFIG_KASAN_HW_TAGS */
 
 static inline bool kasan_enabled(void)
@@ -108,13 +106,6 @@ static inline bool kasan_hw_tags_enabled(void)
 	return false;
 }
 
-static __always_inline void kasan_alloc_pages(struct page *page,
-					      unsigned int order, gfp_t flags)
-{
-	/* Only available for integrated init. */
-	BUILD_BUG();
-}
-
 #endif /* CONFIG_KASAN_HW_TAGS */
 
 static inline bool kasan_has_integrated_init(void)
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 66078cc1b4f0..d7168bfca61a 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -536,7 +536,7 @@ void * __must_check __kasan_kmalloc_large(const void *ptr, size_t size,
 		return NULL;
 
 	/*
-	 * The object has already been unpoisoned by kasan_alloc_pages() for
+	 * The object has already been unpoisoned by kasan_unpoison_pages() for
 	 * alloc_pages() or by kasan_krealloc() for krealloc().
 	 */
 
diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
index c643740b8599..76cf2b6229c7 100644
--- a/mm/kasan/hw_tags.c
+++ b/mm/kasan/hw_tags.c
@@ -192,28 +192,6 @@ void __init kasan_init_hw_tags(void)
 		kasan_stack_collection_enabled() ? "on" : "off");
 }
 
-void kasan_alloc_pages(struct page *page, unsigned int order, gfp_t flags)
-{
-	/*
-	 * This condition should match the one in post_alloc_hook() in
-	 * page_alloc.c.
-	 */
-	bool init = !want_init_on_free() && want_init_on_alloc(flags);
-	bool init_tags = init && (flags & __GFP_ZEROTAGS);
-
-	if (flags & __GFP_SKIP_KASAN_POISON)
-		SetPageSkipKASanPoison(page);
-
-	if (init_tags) {
-		int i;
-
-		for (i = 0; i != 1 << order; ++i)
-			tag_clear_highpage(page + i);
-	} else {
-		kasan_unpoison_pages(page, order, init);
-	}
-}
-
 #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST)
 
 void kasan_enable_tagging_sync(void)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 507004a54f2f..d33e0b0547be 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2383,6 +2383,9 @@ static bool check_new_pages(struct page *page, unsigned int order)
 inline void post_alloc_hook(struct page *page, unsigned int order,
 				gfp_t gfp_flags)
 {
+	bool init = !want_init_on_free() && want_init_on_alloc(gfp_flags);
+	bool init_tags = init && (gfp_flags & __GFP_ZEROTAGS);
+
 	set_page_private(page, 0);
 	set_page_refcounted(page);
 
@@ -2398,15 +2401,22 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
 
 	/*
 	 * As memory initialization might be integrated into KASAN,
-	 * kasan_alloc_pages and kernel_init_free_pages must be
+	 * KASAN unpoisoning and memory initializion code must be
 	 * kept together to avoid discrepancies in behavior.
 	 */
 	if (kasan_has_integrated_init()) {
-		kasan_alloc_pages(page, order, gfp_flags);
-	} else {
-		bool init = !want_init_on_free() && want_init_on_alloc(gfp_flags);
-		bool init_tags = init && (gfp_flags & __GFP_ZEROTAGS);
+		if (gfp_flags & __GFP_SKIP_KASAN_POISON)
+			SetPageSkipKASanPoison(page);
+
+		if (init_tags) {
+			int i;
 
+			for (i = 0; i != 1 << order; ++i)
+				tag_clear_highpage(page + i);
+		} else {
+			kasan_unpoison_pages(page, order, init);
+		}
+	} else {
 		kasan_unpoison_pages(page, order, init);
 
 		if (init_tags) {
-- 
2.25.1