The patch titled
Subject: mm-fix-is_pinnable_page-against-on-cma-page-v5
has been added to the -mm mm-unstable branch. Its filename is
mm-fix-is_pinnable_page-against-on-cma-page-v5.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-fix-is_pinnable_page-against-on-cma-page-v5.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Minchan Kim <minchan@xxxxxxxxxx>
Subject: mm-fix-is_pinnable_page-against-on-cma-page-v5
* clarification why we need READ_ONCE - Paul
* Add a comment about READ_ONCE - John
Link: https://lkml.kernel.org/r/20220512204143.3961150-1-minchan@xxxxxxxxxx
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
Cc: "Paul E . McKenney" <paulmck@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mm.h | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
--- a/include/linux/mm.h~mm-fix-is_pinnable_page-against-on-cma-page-v5
+++ a/include/linux/mm.h
@@ -1627,13 +1627,14 @@ static inline bool is_pinnable_page(stru
{
#ifdef CONFIG_CMA
/*
- * use volatile to use local variable mt instead of
- * refetching mt value.
+ * Defend against future compiler LTO features, or code refactoring
+ * that inlines the above function, by forcing a single read. Because,
+ * this routine races with set_pageblock_migratetype(), and we want to
+ * avoid reading zero, when actually one or the other flags was set.
*/
- int __mt = get_pageblock_migratetype(page);
int mt = __READ_ONCE(__mt);
- if (mt == MIGRATE_CMA || mt == MIGRATE_ISOLATE)
+ if (mt & (MIGRATE_CMA | MIGRATE_ISOLATE))
return false;
#endif
_
Patches currently in -mm which might be from minchan@xxxxxxxxxx are
mm-fix-is_pinnable_page-against-on-cma-page.patch
mm-fix-is_pinnable_page-against-on-cma-page-v5.patch
mm-dont-be-stuck-to-rmap-lock-on-reclaim-path.patch
