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_compact_skip, so that migratetype is not lost during pageblock
isolation.

Link: https://lkml.kernel.org/r/20250617021115.2331563-3-ziy@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kirill A. Shuemov <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Richard Chang <richardycc@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

3 files changed, 33 insertions, 0 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 76d66c07b673..1d1bb2b7f40d 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -79,6 +79,9 @@ enum migratetype {
 	 * __free_pageblock_cma() function.
 	 */
 	MIGRATE_CMA,
+	__MIGRATE_TYPE_END = MIGRATE_CMA,
+#else
+	__MIGRATE_TYPE_END = MIGRATE_HIGHATOMIC,
 #endif
 #ifdef CONFIG_MEMORY_ISOLATION
 	MIGRATE_ISOLATE,	/* can't allocate from here */
diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
index 277d8d92980c..fc021d3f95ca 100644
--- a/include/linux/page-isolation.h
+++ b/include/linux/page-isolation.h
@@ -11,6 +11,12 @@ static inline bool is_migrate_isolate(int migratetype)
 {
 	return migratetype == MIGRATE_ISOLATE;
 }
+#define get_pageblock_isolate(page) \
+	get_pfnblock_bit(page, page_to_pfn(page), PB_migrate_isolate)
+#define clear_pageblock_isolate(page) \
+	clear_pfnblock_bit(page, page_to_pfn(page), PB_migrate_isolate)
+#define set_pageblock_isolate(page) \
+	set_pfnblock_bit(page, page_to_pfn(page), PB_migrate_isolate)
 #else
 static inline bool is_migrate_isolate_page(struct page *page)
 {
@@ -20,6 +26,16 @@ static inline bool is_migrate_isolate(int migratetype)
 {
 	return false;
 }
+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
 
 #define MEMORY_OFFLINE	0x1
diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h
index c240c7a1fb03..6a44be0f39f4 100644
--- a/include/linux/pageblock-flags.h
+++ b/include/linux/pageblock-flags.h
@@ -21,6 +21,13 @@ enum pageblock_bits {
 			/* 3 bits required for migrate types */
 	PB_compact_skip,/* If set the block is skipped by compaction */
 
+#ifdef CONFIG_MEMORY_ISOLATION
+	/*
+	 * Pageblock isolation is represented with a separate bit, so that
+	 * the migratetype of a block is not overwritten by isolation.
+	 */
+	PB_migrate_isolate, /* If set the block is isolated */
+#endif
 	/*
 	 * Assume the bits will always align on a word. If this assumption
 	 * changes then get/set pageblock needs updating.
@@ -32,6 +39,13 @@ enum pageblock_bits {
 
 #define MIGRATETYPE_MASK ((1UL << (PB_migrate_end + 1)) - 1)
 
+#ifdef CONFIG_MEMORY_ISOLATION
+#define MIGRATETYPE_AND_ISO_MASK \
+	(((1UL << (PB_migrate_end + 1)) - 1) | BIT(PB_migrate_isolate))
+#else
+#define MIGRATETYPE_AND_ISO_MASK MIGRATETYPE_MASK
+#endif
+
 #if defined(CONFIG_HUGETLB_PAGE)
 
 #ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE