mm/pageblock-flags: remove PB_migratetype_bits/PB_migrate_end

enum pageblock_bits defines the meaning of pageblock bits.  Currently
PB_migratetype_bits says the lowest 3 bits represents migratetype and
PB_migrate_end/MIGRATETYPE_MASK's definition rely on it with magical
computation.

Remove the definition of PB_migratetype_bits/PB_migrate_end.  Use
PB_migrate_[0|1|2] to represent lowest bits for migratetype.  Then we can
simplify related definition.

Also, MIGRATETYPE_AND_ISO_MASK is MIGRATETYPE_MASK add isolation bit.  Use
MIGRATETYPE_MASK in the definition of MIGRATETYPE_AND_ISO_MASK looks
cleaner.

No functional change intended.

Link: https://lkml.kernel.org/r/20250827070105.16864-3-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h
index 6a44be0f39f45f0857019435cfef4b1ba0eae8d4..e046278a01fa8c37d898df94114d088933b6747f 100644 (file)
--- a/include/linux/pageblock-flags.h
+++ b/include/linux/pageblock-flags.h
@@ -13,12 +13,11 @@
 
 #include <linux/types.h>
 
-#define PB_migratetype_bits 3
 /* Bit indices that affect a whole block of pages */
 enum pageblock_bits {
-       PB_migrate,
-       PB_migrate_end = PB_migrate + PB_migratetype_bits - 1,
-                       /* 3 bits required for migrate types */
+       PB_migrate_0,
+       PB_migrate_1,
+       PB_migrate_2,
        PB_compact_skip,/* If set the block is skipped by compaction */
 
 #ifdef CONFIG_MEMORY_ISOLATION
@@ -37,11 +36,10 @@ enum pageblock_bits {
 
 #define NR_PAGEBLOCK_BITS (roundup_pow_of_two(__NR_PAGEBLOCK_BITS))
 
-#define MIGRATETYPE_MASK ((1UL << (PB_migrate_end + 1)) - 1)
+#define MIGRATETYPE_MASK (BIT(PB_migrate_0)|BIT(PB_migrate_1)|BIT(PB_migrate_2))
 
 #ifdef CONFIG_MEMORY_ISOLATION
-#define MIGRATETYPE_AND_ISO_MASK \
-       (((1UL << (PB_migrate_end + 1)) - 1) | BIT(PB_migrate_isolate))
+#define MIGRATETYPE_AND_ISO_MASK (MIGRATETYPE_MASK | BIT(PB_migrate_isolate))
 #else
 #define MIGRATETYPE_AND_ISO_MASK MIGRATETYPE_MASK
 #endif

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c524b80a3b727c8d888665f6d71f23bd0c78d884..2df6ee6998ab44ac259b3ab1483436db5e166a6b 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -355,7 +355,7 @@ static inline int pfn_to_bitidx(const struct page *page, unsigned long pfn)
 
 static __always_inline bool is_standalone_pb_bit(enum pageblock_bits pb_bit)
 {
-       return pb_bit > PB_migrate_end && pb_bit < __NR_PAGEBLOCK_BITS;
+       return pb_bit >= PB_compact_skip && pb_bit < __NR_PAGEBLOCK_BITS;
 }
 
 static __always_inline void
@@ -370,7 +370,7 @@ get_pfnblock_bitmap_bitidx(const struct page *page, unsigned long pfn,
 #else
        BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4);
 #endif
-       BUILD_BUG_ON(__MIGRATE_TYPE_END >= (1 << PB_migratetype_bits));
+       BUILD_BUG_ON(__MIGRATE_TYPE_END > MIGRATETYPE_MASK);
        VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page);
 
        bitmap = get_pageblock_bitmap(page, pfn);