Re: [PATCH v3 1/4] mm/page_isolation: make page isolation a standalone bit.

[Zi Yan <ziy@nvidia.com>]

On 7 May 2025, at 17:10, Zi Yan wrote:

> 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@nvidia.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(-)
>

Here is the fixup 1/3 to address Johannes’ comments.

From 7eb1d9fa58fdab216862436181e5d2baf2958c54 Mon Sep 17 00:00:00 2001
From: Zi Yan <ziy@nvidia.com>
Date: Thu, 8 May 2025 12:05:59 -0400
Subject: [PATCH] fixup for mm/page_isolation: make page isolation a standalone
 bit

1. keep the original is_migrate_isolate_page()
2. move {get,set,clear}_pageblock_isolate() to mm/page_isolation.c
3. use a single version for get_pageblock_migratetype() and
   get_pfnblock_migratetype().

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
 include/linux/mmzone.h          |  6 ------
 include/linux/page-isolation.h  |  2 +-
 include/linux/pageblock-flags.h | 24 ------------------------
 mm/page_alloc.c                 | 25 ++++++++++---------------
 mm/page_isolation.c             | 17 +++++++++++++++++
 5 files changed, 28 insertions(+), 46 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 9ec022a0b826..7ef01fe148ce 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -112,13 +112,7 @@ extern int page_group_by_mobility_disabled;
 #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)
-
-#endif

 #define folio_migratetype(folio)					\
 	get_pageblock_migratetype(&folio->page)
diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
index 51797dc39cbc..898bb788243b 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_isolate(page);
+	return get_pageblock_migratetype(page) == MIGRATE_ISOLATE;
 }
 static inline bool is_migrate_isolate(int migratetype)
 {
diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h
index 9fadae5892b2..00040e7df8c8 100644
--- a/include/linux/pageblock-flags.h
+++ b/include/linux/pageblock-flags.h
@@ -112,28 +112,4 @@ 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 acf68ef041d8..04e301fb4879 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -381,16 +381,16 @@ 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);
+#ifdef CONFIG_MEMORY_ISOLATION
 	if (flags & PB_migrate_isolate_bit)
 		return MIGRATE_ISOLATE;
-
+#endif
 	return flags;
 }

@@ -401,19 +401,12 @@ static __always_inline int get_pfnblock_migratetype(const struct page *page,

 	flags = get_pfnblock_flags_mask(page, pfn,
 			MIGRATETYPE_MASK);
+#ifdef CONFIG_MEMORY_ISOLATION
 	if (flags & PB_migrate_isolate_bit)
 		return MIGRATE_ISOLATE;
-
+#endif
 	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
@@ -461,11 +454,13 @@ void set_pageblock_migratetype(struct page *page, int migratetype)
 		migratetype = MIGRATE_UNMOVABLE;

 #ifdef CONFIG_MEMORY_ISOLATION
-	if (migratetype == MIGRATE_ISOLATE)
-		set_pageblock_isolate(page);
-	else
+	if (migratetype == MIGRATE_ISOLATE) {
+		set_pfnblock_flags_mask(page, PB_migrate_isolate_bit,
+				page_to_pfn(page), PB_migrate_isolate_bit);
+		return;
+	}
 #endif
-		set_pfnblock_flags_mask(page, (unsigned long)migratetype,
+	set_pfnblock_flags_mask(page, (unsigned long)migratetype,
 				page_to_pfn(page), MIGRATETYPE_MASK);
 }

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index b2fc5266e3d2..b6a62132e20e 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -15,6 +15,23 @@
 #define CREATE_TRACE_POINTS
 #include <trace/events/page_isolation.h>

+static inline bool get_pageblock_isolate(struct page *page)
+{
+	return get_pfnblock_flags_mask(page, page_to_pfn(page),
+			PB_migrate_isolate_bit);
+}
+static inline void clear_pageblock_isolate(struct page *page)
+{
+	set_pfnblock_flags_mask(page, 0, page_to_pfn(page),
+			PB_migrate_isolate_bit);
+}
+static inline void set_pageblock_isolate(struct page *page)
+{
+	set_pfnblock_flags_mask(page, PB_migrate_isolate_bit,
+			page_to_pfn(page),
+			PB_migrate_isolate_bit);
+}
+
 /*
  * This function checks whether the range [start_pfn, end_pfn) includes
  * unmovable pages or not. The range must fall into a single pageblock and
-- 
2.47.2



Best Regards,
Yan, Zi