mm: cma: set early_pfn and bitmap as a union in cma_memrange

Since early_pfn and bitmap are never used at the same time, they can be
defined as a union to reduce the size of the data structure.  This change
can save 8 * u64 entries per CMA.

Link: https://lkml.kernel.org/r/20250509083528.1360952-1-hezhongkun.hzk@bytedance.com
Signed-off-by: Zhongkun He <hezhongkun.hzk@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/mm/cma.h b/mm/cma.h
index 41a3ab0ec3de..c70180c36559 100644
--- a/mm/cma.h
+++ b/mm/cma.h
@@ -25,9 +25,11 @@ struct cma_kobject {
  */
 struct cma_memrange {
 	unsigned long base_pfn;
-	unsigned long early_pfn;
 	unsigned long count;
-	unsigned long *bitmap;
+	union {
+		unsigned long early_pfn;
+		unsigned long *bitmap;
+	};
 #ifdef CONFIG_CMA_DEBUGFS
 	struct debugfs_u32_array dfs_bitmap;
 #endif