[RFC PATCH v12 based on mm-unstable as of Feb 21, 2025 06/25] mm: move should_skip_kasan_poison() to mm/internal.h

[Byungchul Park <byungchul@sk.com>]

Functionally, no change.  This is a preparation for luf mechanism that
needs to use should_skip_kasan_poison() function in mm/internal.h.

Signed-off-by: Byungchul Park <byungchul@sk.com>
---
 mm/internal.h   | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 mm/page_alloc.c | 47 -----------------------------------------------
 2 files changed, 47 insertions(+), 47 deletions(-)

diff --git a/mm/internal.h b/mm/internal.h
index c4d2018a7cf8e..ee8af97c39f59 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1067,8 +1067,55 @@ static inline void vunmap_range_noflush(unsigned long start, unsigned long end)
 DECLARE_STATIC_KEY_TRUE(deferred_pages);
 
 bool __init deferred_grow_zone(struct zone *zone, unsigned int order);
+
+static inline bool deferred_pages_enabled(void)
+{
+	return static_branch_unlikely(&deferred_pages);
+}
+#else
+static inline bool deferred_pages_enabled(void)
+{
+	return false;
+}
 #endif /* CONFIG_DEFERRED_STRUCT_PAGE_INIT */
 
+/*
+ * Skip KASAN memory poisoning when either:
+ *
+ * 1. For generic KASAN: deferred memory initialization has not yet completed.
+ *    Tag-based KASAN modes skip pages freed via deferred memory initialization
+ *    using page tags instead (see below).
+ * 2. For tag-based KASAN modes: the page has a match-all KASAN tag, indicating
+ *    that error detection is disabled for accesses via the page address.
+ *
+ * Pages will have match-all tags in the following circumstances:
+ *
+ * 1. Pages are being initialized for the first time, including during deferred
+ *    memory init; see the call to page_kasan_tag_reset in __init_single_page.
+ * 2. The allocation was not unpoisoned due to __GFP_SKIP_KASAN, with the
+ *    exception of pages unpoisoned by kasan_unpoison_vmalloc.
+ * 3. The allocation was excluded from being checked due to sampling,
+ *    see the call to kasan_unpoison_pages.
+ *
+ * Poisoning pages during deferred memory init will greatly lengthen the
+ * process and cause problem in large memory systems as the deferred pages
+ * initialization is done with interrupt disabled.
+ *
+ * Assuming that there will be no reference to those newly initialized
+ * pages before they are ever allocated, this should have no effect on
+ * KASAN memory tracking as the poison will be properly inserted at page
+ * allocation time. The only corner case is when pages are allocated by
+ * on-demand allocation and then freed again before the deferred pages
+ * initialization is done, but this is not likely to happen.
+ */
+static inline bool should_skip_kasan_poison(struct page *page)
+{
+	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+		return deferred_pages_enabled();
+
+	return page_kasan_tag(page) == KASAN_TAG_KERNEL;
+}
+
 enum mminit_level {
 	MMINIT_WARNING,
 	MMINIT_VERIFY,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 86c9fa45d36fe..f3930a2a05cd3 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -299,11 +299,6 @@ int page_group_by_mobility_disabled __read_mostly;
  */
 DEFINE_STATIC_KEY_TRUE(deferred_pages);
 
-static inline bool deferred_pages_enabled(void)
-{
-	return static_branch_unlikely(&deferred_pages);
-}
-
 /*
  * deferred_grow_zone() is __init, but it is called from
  * get_page_from_freelist() during early boot until deferred_pages permanently
@@ -316,11 +311,6 @@ _deferred_grow_zone(struct zone *zone, unsigned int order)
 	return deferred_grow_zone(zone, order);
 }
 #else
-static inline bool deferred_pages_enabled(void)
-{
-	return false;
-}
-
 static inline bool _deferred_grow_zone(struct zone *zone, unsigned int order)
 {
 	return false;
@@ -993,43 +983,6 @@ static int free_tail_page_prepare(struct page *head_page, struct page *page)
 	return ret;
 }
 
-/*
- * Skip KASAN memory poisoning when either:
- *
- * 1. For generic KASAN: deferred memory initialization has not yet completed.
- *    Tag-based KASAN modes skip pages freed via deferred memory initialization
- *    using page tags instead (see below).
- * 2. For tag-based KASAN modes: the page has a match-all KASAN tag, indicating
- *    that error detection is disabled for accesses via the page address.
- *
- * Pages will have match-all tags in the following circumstances:
- *
- * 1. Pages are being initialized for the first time, including during deferred
- *    memory init; see the call to page_kasan_tag_reset in __init_single_page.
- * 2. The allocation was not unpoisoned due to __GFP_SKIP_KASAN, with the
- *    exception of pages unpoisoned by kasan_unpoison_vmalloc.
- * 3. The allocation was excluded from being checked due to sampling,
- *    see the call to kasan_unpoison_pages.
- *
- * Poisoning pages during deferred memory init will greatly lengthen the
- * process and cause problem in large memory systems as the deferred pages
- * initialization is done with interrupt disabled.
- *
- * Assuming that there will be no reference to those newly initialized
- * pages before they are ever allocated, this should have no effect on
- * KASAN memory tracking as the poison will be properly inserted at page
- * allocation time. The only corner case is when pages are allocated by
- * on-demand allocation and then freed again before the deferred pages
- * initialization is done, but this is not likely to happen.
- */
-static inline bool should_skip_kasan_poison(struct page *page)
-{
-	if (IS_ENABLED(CONFIG_KASAN_GENERIC))
-		return deferred_pages_enabled();
-
-	return page_kasan_tag(page) == KASAN_TAG_KERNEL;
-}
-
 static void kernel_init_pages(struct page *page, int numpages)
 {
 	int i;
-- 
2.17.1