[PATCH] mm/page_isolation: fix isolate_single_pageblock() isolation behavior

[Zi Yan <zi.yan@xxxxxxxx>]

From: Zi Yan <ziy@xxxxxxxxxx>

set_migratetype_isolate() does not allow isolating MIGRATE_CMA pageblocks
unless it is used for CMA allocation. isolate_single_pageblock() did not
have the same behavior when it is used together with
set_migratetype_isolate() in start_isolate_page_range(). This allows
alloc_contig_range() with migratetype other than MIGRATE_CMA, like
MIGRATE_MOVABLE (used by alloc_contig_pages()), to isolate first and last
pageblock but fail the rest. The failure leads to changing migratetype
of the first and last pageblock to MIGRATE_MOVABLE from MIGRATE_CMA,
corrupting the CMA region. This can happen during gigantic page
allocations.

Fix it by passing migratetype into isolate_single_pageblock(), so that
set_migratetype_isolate() used by isolate_single_pageblock() will prevent
the isolation happening.

Fixes: b2c9e2fbba32 ("mm: make alloc_contig_range work at pageblock granularity")
Reported-by: Doug Berger <opendmb@xxxxxxxxx>
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
 mm/page_isolation.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index c66d61e0bc72..04141a9bea70 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -288,6 +288,7 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
  * @isolate_before:	isolate the pageblock before the boundary_pfn
  * @skip_isolation:	the flag to skip the pageblock isolation in second
  *			isolate_single_pageblock()
+ * @migratetype:	migrate type to set in error recovery.
  *
  * Free and in-use pages can be as big as MAX_ORDER-1 and contain more than one
  * pageblock. When not all pageblocks within a page are isolated at the same
@@ -302,9 +303,9 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages)
  * the in-use page then splitting the free page.
  */
 static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
-			gfp_t gfp_flags, bool isolate_before, bool skip_isolation)
+			gfp_t gfp_flags, bool isolate_before, bool skip_isolation,
+			int migratetype)
 {
-	unsigned char saved_mt;
 	unsigned long start_pfn;
 	unsigned long isolate_pageblock;
 	unsigned long pfn;
@@ -328,13 +329,13 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
 	start_pfn  = max(ALIGN_DOWN(isolate_pageblock, MAX_ORDER_NR_PAGES),
 				      zone->zone_start_pfn);
 
-	saved_mt = get_pageblock_migratetype(pfn_to_page(isolate_pageblock));
+	if (skip_isolation) {
+		int mt = get_pageblock_migratetype(pfn_to_page(isolate_pageblock));
 
-	if (skip_isolation)
-		VM_BUG_ON(!is_migrate_isolate(saved_mt));
-	else {
-		ret = set_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt, flags,
-				isolate_pageblock, isolate_pageblock + pageblock_nr_pages);
+		VM_BUG_ON(!is_migrate_isolate(mt));
+	} else {
+		ret = set_migratetype_isolate(pfn_to_page(isolate_pageblock), migratetype,
+				flags, isolate_pageblock, isolate_pageblock + pageblock_nr_pages);
 
 		if (ret)
 			return ret;
@@ -475,7 +476,7 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
 failed:
 	/* restore the original migratetype */
 	if (!skip_isolation)
-		unset_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt);
+		unset_migratetype_isolate(pfn_to_page(isolate_pageblock), migratetype);
 	return -EBUSY;
 }
 
@@ -537,7 +538,8 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 	bool skip_isolation = false;
 
 	/* isolate [isolate_start, isolate_start + pageblock_nr_pages) pageblock */
-	ret = isolate_single_pageblock(isolate_start, flags, gfp_flags, false, skip_isolation);
+	ret = isolate_single_pageblock(isolate_start, flags, gfp_flags, false,
+			skip_isolation, migratetype);
 	if (ret)
 		return ret;
 
@@ -545,7 +547,8 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 		skip_isolation = true;
 
 	/* isolate [isolate_end - pageblock_nr_pages, isolate_end) pageblock */
-	ret = isolate_single_pageblock(isolate_end, flags, gfp_flags, true, skip_isolation);
+	ret = isolate_single_pageblock(isolate_end, flags, gfp_flags, true,
+			skip_isolation, migratetype);
 	if (ret) {
 		unset_migratetype_isolate(pfn_to_page(isolate_start), migratetype);
 		return ret;
-- 
2.35.1