mm: cma: use pageblock_order as the single alignment

Now alloc_contig_range() works at pageblock granularity.  Change CMA
allocation, which uses alloc_contig_range(), to use pageblock_nr_pages
alignment.

Link: https://lkml.kernel.org/r/20220425143118.2850746-6-zi.yan@sent.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: Eric Ren <renzhengeek@gmail.com>
Cc: kernel test robot <lkp@intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/cma.h

@@ -17,11 +17,11 @@
 #define CMA_MAX_NAME 64
 
 /*
- * TODO: once the buddy -- especially pageblock merging and alloc_contig_range()
+ *  the buddy -- especially pageblock merging and alloc_contig_range()
  * -- can deal with only some pageblocks of a higher-order page being
  *  MIGRATE_CMA, we can use pageblock_nr_pages.
  */
-#define CMA_MIN_ALIGNMENT_PAGES MAX_ORDER_NR_PAGES
+#define CMA_MIN_ALIGNMENT_PAGES pageblock_nr_pages
 #define CMA_MIN_ALIGNMENT_BYTES (PAGE_SIZE * CMA_MIN_ALIGNMENT_PAGES)
 
 struct cma;

include/linux/mmzone.h

@@ -54,10 +54,7 @@ enum migratetype {
 	 *
 	 * The way to use it is to change migratetype of a range of
 	 * pageblocks to MIGRATE_CMA which can be done by
-	 * __free_pageblock_cma() function.  What is important though
-	 * is that a range of pageblocks must be aligned to
-	 * MAX_ORDER_NR_PAGES should biggest page be bigger than
-	 * a single pageblock.
+	 * __free_pageblock_cma() function.
 	 */
 	MIGRATE_CMA,
 #endif

mm/page_alloc.c

@@ -9046,8 +9046,8 @@ int __alloc_contig_migrate_range(struct compact_control *cc,
  *			be either of the two.
  * @gfp_mask:	GFP mask to use during compaction
  *
- * The PFN range does not have to be pageblock or MAX_ORDER_NR_PAGES
- * aligned.  The PFN range must belong to a single zone.
+ * The PFN range does not have to be pageblock aligned. The PFN range must
+ * belong to a single zone.
  *
  * The first thing this routine does is attempt to MIGRATE_ISOLATE all
  * pageblocks in the range.  Once isolated, the pageblocks should not