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.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>

1 files changed, 16 insertions, 17 deletions

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 8a0f16d2e4c3..b3f074d1682e 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -444,7 +444,6 @@ failed:
  * 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))