diff mbox series

[03/10] mm/page_alloc: don't corrupt pcppage_migratetype

Message ID 20210820020412.EA2QVRAWd%akpm@linux-foundation.org (mailing list archive)
State New
Headers show
Series [01/10] Revert "mm/shmem: fix shmem_swapin() race with swapoff" | expand

Commit Message

Andrew Morton Aug. 20, 2021, 2:04 a.m. UTC 
From: Doug Berger <opendmb@gmail.com>
Subject: mm/page_alloc: don't corrupt pcppage_migratetype

When placing pages on a pcp list, migratetype values over MIGRATE_PCPTYPES
get added to the MIGRATE_MOVABLE pcp list.

However, the actual migratetype is preserved in the page and should not be
changed to MIGRATE_MOVABLE or the page may end up on the wrong free_list.

The impact is that HIGHATOMIC or CMA pages getting bulk freed from the PCP
lists could potentially end up on the wrong buddy list.  There are various
consequences but minimally NR_FREE_CMA_PAGES accounting could get screwed
up.

[mgorman@techsingularity.net: changelog update]
Link: https://lkml.kernel.org/r/20210811182917.2607994-1-opendmb@gmail.com
Fixes: df1acc856923 ("mm/page_alloc: avoid conflating IRQs disabled with zone->lock")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_alloc.c |   25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)
diff mbox series

Patch

--- a/mm/page_alloc.c~mm-page_alloc-dont-corrupt-pcppage_migratetype
+++ a/mm/page_alloc.c
@@ -3453,19 +3453,10 @@  void free_unref_page_list(struct list_he
 		 * comment in free_unref_page.
 		 */
 		migratetype = get_pcppage_migratetype(page);
-		if (unlikely(migratetype >= MIGRATE_PCPTYPES)) {
-			if (unlikely(is_migrate_isolate(migratetype))) {
-				list_del(&page->lru);
-				free_one_page(page_zone(page), page, pfn, 0,
-							migratetype, FPI_NONE);
-				continue;
-			}
-
-			/*
-			 * Non-isolated types over MIGRATE_PCPTYPES get added
-			 * to the MIGRATE_MOVABLE pcp list.
-			 */
-			set_pcppage_migratetype(page, MIGRATE_MOVABLE);
+		if (unlikely(is_migrate_isolate(migratetype))) {
+			list_del(&page->lru);
+			free_one_page(page_zone(page), page, pfn, 0, migratetype, FPI_NONE);
+			continue;
 		}
 
 		set_page_private(page, pfn);
@@ -3475,7 +3466,15 @@  void free_unref_page_list(struct list_he
 	list_for_each_entry_safe(page, next, list, lru) {
 		pfn = page_private(page);
 		set_page_private(page, 0);
+
+		/*
+		 * Non-isolated types over MIGRATE_PCPTYPES get added
+		 * to the MIGRATE_MOVABLE pcp list.
+		 */
 		migratetype = get_pcppage_migratetype(page);
+		if (unlikely(migratetype >= MIGRATE_PCPTYPES))
+			migratetype = MIGRATE_MOVABLE;
+
 		trace_mm_page_free_batched(page);
 		free_unref_page_commit(page, pfn, migratetype, 0);