mm: page_isolation: enable arbitrary range page isolation.

Now start_isolate_page_range() is ready to handle arbitrary range
isolation, so move the alignment check/adjustment into the function body. 
Do the same for its counterpart undo_isolate_page_range(). 
alloc_contig_range(), its caller, can pass an arbitrary range instead of a
MAX_ORDER_NR_PAGES aligned one.

Link: https://lkml.kernel.org/r/20220425143118.2850746-5-zi.yan@sent.comSigned-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>

mm/page_alloc.c

@@ -8956,16 +8956,6 @@ void *__init alloc_large_system_hash(const char *tablename,
 }
 
 #ifdef CONFIG_CONTIG_ALLOC
-static unsigned long pfn_max_align_down(unsigned long pfn)
-{
-	return ALIGN_DOWN(pfn, MAX_ORDER_NR_PAGES);
-}
-
-static unsigned long pfn_max_align_up(unsigned long pfn)
-{
-	return ALIGN(pfn, MAX_ORDER_NR_PAGES);
-}
-
 #if defined(CONFIG_DYNAMIC_DEBUG) || \
 	(defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE))
 /* Usage: See admin-guide/dynamic-debug-howto.rst */
@@ -9107,8 +9097,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
 	 * put back to page allocator so that buddy can use them.
 	 */
 
-	ret = start_isolate_page_range(pfn_max_align_down(start),
-				pfn_max_align_up(end), migratetype, 0, gfp_mask);
+	ret = start_isolate_page_range(start, end, migratetype, 0, gfp_mask);
 	if (ret)
 		goto done;
 
@@ -9189,8 +9178,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
 		free_contig_range(end, outer_end - end);
 
 done:
-	undo_isolate_page_range(pfn_max_align_down(start),
-				pfn_max_align_up(end), migratetype);
+	undo_isolate_page_range(start, end, migratetype);
 	return ret;
 }
 EXPORT_SYMBOL(alloc_contig_range);

mm/page_isolation.c

@@ -444,7 +444,6 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, gfp_t gfp_flags,
  * be MIGRATE_ISOLATE.
  * @start_pfn:		The lower PFN of the range to be isolated.
  * @end_pfn:		The upper PFN of the range to be isolated.
- *			start_pfn/end_pfn must be aligned to pageblock_order.
  * @migratetype:	Migrate type to set in error recovery.
  * @flags:		The following flags are allowed (they can be combined in
  *			a bit mask)
@@ -491,33 +490,33 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 {
 	unsigned long pfn;
 	struct page *page;
+	/* isolation is done at page block granularity */
+	unsigned long isolate_start = ALIGN_DOWN(start_pfn, pageblock_nr_pages);
+	unsigned long isolate_end = ALIGN(end_pfn, pageblock_nr_pages);
 	int ret;
 
-	BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
-	BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
-
-	/* isolate [start_pfn, start_pfn + pageblock_nr_pages) pageblock */
-	ret = isolate_single_pageblock(start_pfn, gfp_flags, false);
+	/* isolate [isolate_start, isolate_start + pageblock_nr_pages) pageblock */
+	ret = isolate_single_pageblock(isolate_start, gfp_flags, false);
 	if (ret)
 		return ret;
 
-	/* isolate [end_pfn - pageblock_nr_pages, end_pfn) pageblock */
-	ret = isolate_single_pageblock(end_pfn, gfp_flags, true);
+	/* isolate [isolate_end - pageblock_nr_pages, isolate_end) pageblock */
+	ret = isolate_single_pageblock(isolate_end, gfp_flags, true);
 	if (ret) {
-		unset_migratetype_isolate(pfn_to_page(start_pfn), migratetype);
+		unset_migratetype_isolate(pfn_to_page(isolate_start), migratetype);
 		return ret;
 	}
 
 	/* skip isolated pageblocks at the beginning and end */
-	for (pfn = start_pfn + pageblock_nr_pages;
-	     pfn < end_pfn - pageblock_nr_pages;
+	for (pfn = isolate_start + pageblock_nr_pages;
+	     pfn < isolate_end - pageblock_nr_pages;
 	     pfn += pageblock_nr_pages) {
 		page = __first_valid_page(pfn, pageblock_nr_pages);
 		if (page && set_migratetype_isolate(page, migratetype, flags,
 					start_pfn, end_pfn)) {
-			undo_isolate_page_range(start_pfn, pfn, migratetype);
+			undo_isolate_page_range(isolate_start, pfn, migratetype);
 			unset_migratetype_isolate(
-				pfn_to_page(end_pfn - pageblock_nr_pages),
+				pfn_to_page(isolate_end - pageblock_nr_pages),
 				migratetype);
 			return -EBUSY;
 		}
@@ -533,12 +532,12 @@ void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 {
 	unsigned long pfn;
 	struct page *page;
+	unsigned long isolate_start = ALIGN_DOWN(start_pfn, pageblock_nr_pages);
+	unsigned long isolate_end = ALIGN(end_pfn, pageblock_nr_pages);
 
-	BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
-	BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
 
-	for (pfn = start_pfn;
-	     pfn < end_pfn;
+	for (pfn = isolate_start;
+	     pfn < isolate_end;
 	     pfn += pageblock_nr_pages) {
 		page = __first_valid_page(pfn, pageblock_nr_pages);
 		if (!page || !is_migrate_isolate_page(page))