The patch titled
Subject: mm: migrate: Fix THP's mapcount on isolation
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-migrate-fix-thps-mapcount-on-isolation.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-migrate-fix-thps-mapcount-on-isolation.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Gavin Shan <gshan@xxxxxxxxxx>
Subject: mm: migrate: Fix THP's mapcount on isolation
Date: Wed, 23 Nov 2022 08:57:52 +0800
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.
Link: https://lkml.kernel.org/r/20221123005752.161003-1-gshan@xxxxxxxxxx
Fixes: 3917c80280c9 ("thp: change CoW semantics for anon-THP")
Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
Reported-by: Zhenyu Zhang <zhenyzha@xxxxxxxxxx>
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: William Kucharski <william.kucharski@xxxxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [v5.8+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/compaction.c~mm-migrate-fix-thps-mapcount-on-isolation
+++ a/mm/compaction.c
@@ -990,7 +990,7 @@ isolate_migratepages_block(struct compac
* admittedly racy check.
*/
mapping = page_mapping(page);
- if (!mapping && page_count(page) > page_mapcount(page))
+ if (!mapping && page_count(page) > total_mapcount(page))
goto isolate_fail;
/*
_
Patches currently in -mm which might be from gshan@xxxxxxxxxx are
mm-migrate-fix-thps-mapcount-on-isolation.patch
