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Message-ID: <20250507211059.2211628-2-ziy@nvidia.com>
Date: Wed,  7 May 2025 17:10:56 -0400
From: Zi Yan <ziy@...dia.com>
To: David Hildenbrand <david@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Oscar Salvador <osalvador@...e.de>,
	Vlastimil Babka <vbabka@...e.cz>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>,
	Brendan Jackman <jackmanb@...gle.com>,
	Richard Chang <richardycc@...gle.com>,
	linux-kernel@...r.kernel.org,
	Zi Yan <ziy@...dia.com>
Subject: [PATCH v3 1/4] mm/page_isolation: make page isolation a standalone bit.

During page isolation, the original migratetype is overwritten, since
MIGRATE_* are enums and stored in pageblock bitmaps. Change
MIGRATE_ISOLATE to be stored a standalone bit, PB_migrate_isolate, like
PB_migrate_skip, so that migratetype is not lost during pageblock
isolation. pageblock bits needs to be word aligned, so expand
the number of pageblock bits from 4 to 8 and make PB_migrate_isolate bit 7.

Signed-off-by: Zi Yan <ziy@...dia.com>
---
 include/linux/mmzone.h          | 17 ++++++++++----
 include/linux/page-isolation.h  |  2 +-
 include/linux/pageblock-flags.h | 33 +++++++++++++++++++++++++-
 mm/page_alloc.c                 | 41 ++++++++++++++++++++++++++++++++-
 4 files changed, 86 insertions(+), 7 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index b19a98c20de8..9ec022a0b826 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -106,14 +106,23 @@ static inline bool migratetype_is_mergeable(int mt)
 
 extern int page_group_by_mobility_disabled;
 
-#define MIGRATETYPE_MASK ((1UL << PB_migratetype_bits) - 1)
+#ifdef CONFIG_MEMORY_ISOLATION
+#define MIGRATETYPE_MASK ((BIT(PB_migratetype_bits) - 1) | PB_migrate_isolate_bit)
+#else
+#define MIGRATETYPE_MASK (BIT(PB_migratetype_bits) - 1)
+#endif
 
+#ifdef CONFIG_MEMORY_ISOLATION
+unsigned long get_pageblock_migratetype(const struct page *page);
+#else
 #define get_pageblock_migratetype(page)					\
 	get_pfnblock_flags_mask(page, page_to_pfn(page), MIGRATETYPE_MASK)
 
-#define folio_migratetype(folio)				\
-	get_pfnblock_flags_mask(&folio->page, folio_pfn(folio),		\
-			MIGRATETYPE_MASK)
+#endif
+
+#define folio_migratetype(folio)					\
+	get_pageblock_migratetype(&folio->page)
+
 struct free_area {
 	struct list_head	free_list[MIGRATE_TYPES];
 	unsigned long		nr_free;
diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
index 898bb788243b..51797dc39cbc 100644
--- a/include/linux/page-isolation.h
+++ b/include/linux/page-isolation.h
@@ -5,7 +5,7 @@
 #ifdef CONFIG_MEMORY_ISOLATION
 static inline bool is_migrate_isolate_page(struct page *page)
 {
-	return get_pageblock_migratetype(page) == MIGRATE_ISOLATE;
+	return get_pageblock_isolate(page);
 }
 static inline bool is_migrate_isolate(int migratetype)
 {
diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h
index 0c4963339f0b..9fadae5892b2 100644
--- a/include/linux/pageblock-flags.h
+++ b/include/linux/pageblock-flags.h
@@ -20,7 +20,10 @@ enum pageblock_bits {
 	PB_migrate_end = PB_migrate + PB_migratetype_bits - 1,
 			/* 3 bits required for migrate types */
 	PB_migrate_skip,/* If set the block is skipped by compaction */
-
+#ifdef CONFIG_MEMORY_ISOLATION
+	PB_migrate_isolate = 7, /* If set the block is isolated */
+			/* set it to 7 to make pageblock bit word aligned */
+#endif
 	/*
 	 * Assume the bits will always align on a word. If this assumption
 	 * changes then get/set pageblock needs updating.
@@ -28,6 +31,10 @@ enum pageblock_bits {
 	NR_PAGEBLOCK_BITS
 };
 
+#ifdef CONFIG_MEMORY_ISOLATION
+#define PB_migrate_isolate_bit BIT(PB_migrate_isolate)
+#endif
+
 #if defined(CONFIG_PAGE_BLOCK_ORDER)
 #define PAGE_BLOCK_ORDER CONFIG_PAGE_BLOCK_ORDER
 #else
@@ -105,4 +112,28 @@ static inline void set_pageblock_skip(struct page *page)
 }
 #endif /* CONFIG_COMPACTION */
 
+#ifdef CONFIG_MEMORY_ISOLATION
+#define get_pageblock_isolate(page) \
+	get_pfnblock_flags_mask(page, page_to_pfn(page),	\
+			PB_migrate_isolate_bit)
+#define clear_pageblock_isolate(page) \
+	set_pfnblock_flags_mask(page, 0, page_to_pfn(page),	\
+			PB_migrate_isolate_bit)
+#define set_pageblock_isolate(page) \
+	set_pfnblock_flags_mask(page, PB_migrate_isolate_bit,	\
+			page_to_pfn(page),			\
+			PB_migrate_isolate_bit)
+#else
+static inline bool get_pageblock_isolate(struct page *page)
+{
+	return false;
+}
+static inline void clear_pageblock_isolate(struct page *page)
+{
+}
+static inline void set_pageblock_isolate(struct page *page)
+{
+}
+#endif /* CONFIG_MEMORY_ISOLATION */
+
 #endif	/* PAGEBLOCK_FLAGS_H */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c77592b22256..acf68ef041d8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -381,12 +381,40 @@ unsigned long get_pfnblock_flags_mask(const struct page *page,
 	return (word >> bitidx) & mask;
 }
 
+#ifdef CONFIG_MEMORY_ISOLATION
+unsigned long get_pageblock_migratetype(const struct page *page)
+{
+	unsigned long flags;
+
+	flags = get_pfnblock_flags_mask(page, page_to_pfn(page),
+			MIGRATETYPE_MASK);
+	if (flags & PB_migrate_isolate_bit)
+		return MIGRATE_ISOLATE;
+
+	return flags;
+}
+
+static __always_inline int get_pfnblock_migratetype(const struct page *page,
+					unsigned long pfn)
+{
+	unsigned long flags;
+
+	flags = get_pfnblock_flags_mask(page, pfn,
+			MIGRATETYPE_MASK);
+	if (flags & PB_migrate_isolate_bit)
+		return MIGRATE_ISOLATE;
+
+	return flags;
+}
+#else
 static __always_inline int get_pfnblock_migratetype(const struct page *page,
 					unsigned long pfn)
 {
 	return get_pfnblock_flags_mask(page, pfn, MIGRATETYPE_MASK);
 }
 
+#endif
+
 /**
  * set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages
  * @page: The page within the block of interest
@@ -402,8 +430,14 @@ void set_pfnblock_flags_mask(struct page *page, unsigned long flags,
 	unsigned long bitidx, word_bitidx;
 	unsigned long word;
 
+#ifdef CONFIG_MEMORY_ISOLATION
+	BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 8);
+	/* extra one for MIGRATE_ISOLATE */
+	BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits) + 1);
+#else
 	BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4);
 	BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits));
+#endif
 
 	bitmap = get_pageblock_bitmap(page, pfn);
 	bitidx = pfn_to_bitidx(page, pfn);
@@ -426,7 +460,12 @@ void set_pageblock_migratetype(struct page *page, int migratetype)
 		     migratetype < MIGRATE_PCPTYPES))
 		migratetype = MIGRATE_UNMOVABLE;
 
-	set_pfnblock_flags_mask(page, (unsigned long)migratetype,
+#ifdef CONFIG_MEMORY_ISOLATION
+	if (migratetype == MIGRATE_ISOLATE)
+		set_pageblock_isolate(page);
+	else
+#endif
+		set_pfnblock_flags_mask(page, (unsigned long)migratetype,
 				page_to_pfn(page), MIGRATETYPE_MASK);
 }
 
-- 
2.47.2


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