The patch titled
Subject: mm: migrate: fix an incorrect call of prep_transhuge_page()
has been removed from the -mm tree. Its filename was
mm-migrate-fix-an-incorrect-call-of-prep_transhuge_page.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Zi Yan <zi.yan@xxxxxxxxxxxxxx>
Subject: mm: migrate: fix an incorrect call of prep_transhuge_page()
In https://lkml.org/lkml/2017/11/20/411, Andrea reported that during
memory hotplug/hot remove prep_transhuge_page() is called incorrectly on
non-THP pages for migration, when THP is on but THP migration is not
enabled. This leads to a bad state of target pages for migration.
By inspecting the code, if called on a non-THP, prep_transhuge_page() will
1) change the value of the mapping of (page + 2), since it is used
for THP deferred list;
2) change the lru value of (page + 1), since it is used for THP's
dtor.
Both can lead to data corruption of these two pages.
Andrea said:
: Pragmatically and from the point of view of the memory_hotplug subsys, the
: effect is a kernel crash when pages are being migrated during a memory hot
: remove offline and migration target pages are found in a bad state.
This patch fixes it by only calling prep_transhuge_page() when we are
certain that the target page is THP.
Link: http://lkml.kernel.org/r/20171121021855.50525-1-zi.yan@xxxxxxxx
Fixes: 8135d8926c08 ("mm: memory_hotplug: memory hotremove supports thp migration")
Signed-off-by: Zi Yan <zi.yan@xxxxxxxxxxxxxx>
Reported-by: Andrea Reale <ar@xxxxxxxxxxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: "Jérôme Glisse" <jglisse@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [4.14]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/migrate.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN include/linux/migrate.h~mm-migrate-fix-an-incorrect-call-of-prep_transhuge_page include/linux/migrate.h
--- a/include/linux/migrate.h~mm-migrate-fix-an-incorrect-call-of-prep_transhuge_page
+++ a/include/linux/migrate.h
@@ -54,7 +54,7 @@ static inline struct page *new_page_node
new_page = __alloc_pages_nodemask(gfp_mask, order,
preferred_nid, nodemask);
- if (new_page && PageTransHuge(page))
+ if (new_page && PageTransHuge(new_page))
prep_transhuge_page(new_page);
return new_page;
_
Patches currently in -mm which might be from zi.yan@xxxxxxxxxxxxxx are