This is a note to let you know that I've just added the patch titled
mm: migrate: fix THP's mapcount on isolation
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-migrate-fix-thp-s-mapcount-on-isolation.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 488391d6b29def702747cde1fe6054588371cfc7
Author: Gavin Shan <gshan@xxxxxxxxxx>
Date: Thu Nov 24 17:55:23 2022 +0800
mm: migrate: fix THP's mapcount on isolation
[ Upstream commit 829ae0f81ce093d674ff2256f66a714753e9ce32 ]
The issue is reported when removing memory through virtio_mem device. The
transparent huge page, experienced copy-on-write fault, is wrongly
regarded as pinned. The transparent huge page is escaped from being
isolated in isolate_migratepages_block(). The transparent huge page can't
be migrated and the corresponding memory block can't be put into offline
state.
Fix it by replacing page_mapcount() with total_mapcount(). With this, the
transparent huge page can be isolated and migrated, and the memory block
can be put into offline state. Besides, The page's refcount is increased
a bit earlier to avoid the page is released when the check is executed.
Link: https://lkml.kernel.org/r/20221124095523.31061-1-gshan@xxxxxxxxxx
Fixes: 1da2f328fa64 ("mm,thp,compaction,cma: allow THP migration for CMA allocations")
Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
Reported-by: Zhenyu Zhang <zhenyzha@xxxxxxxxxx>
Tested-by: Zhenyu Zhang <zhenyzha@xxxxxxxxxx>
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: William Kucharski <william.kucharski@xxxxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [5.7+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/mm/compaction.c b/mm/compaction.c
index b6bd745a2f7f..e8fcf0e0c1ca 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -992,29 +992,29 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
goto isolate_fail;
}
+ /*
+ * Be careful not to clear PageLRU until after we're
+ * sure the page is not being freed elsewhere -- the
+ * page release code relies on it.
+ */
+ if (unlikely(!get_page_unless_zero(page)))
+ goto isolate_fail;
+
/*
* Migration will fail if an anonymous page is pinned in memory,
* so avoid taking lru_lock and isolating it unnecessarily in an
* admittedly racy check.
*/
mapping = page_mapping(page);
- if (!mapping && page_count(page) > page_mapcount(page))
- goto isolate_fail;
+ if (!mapping && (page_count(page) - 1) > total_mapcount(page))
+ goto isolate_fail_put;
/*
* Only allow to migrate anonymous pages in GFP_NOFS context
* because those do not depend on fs locks.
*/
if (!(cc->gfp_mask & __GFP_FS) && mapping)
- goto isolate_fail;
-
- /*
- * Be careful not to clear PageLRU until after we're
- * sure the page is not being freed elsewhere -- the
- * page release code relies on it.
- */
- if (unlikely(!get_page_unless_zero(page)))
- goto isolate_fail;
+ goto isolate_fail_put;
/* Only take pages on LRU: a check now makes later tests safe */
if (!PageLRU(page))
