The patch titled
Subject: mm: thp: fix soft dirty for migration when split
has been removed from the -mm tree. Its filename was
mm-thp-fix-soft-dirty-for-migration-when-split.patch
This patch was dropped because an updated version will be merged
------------------------------------------------------
From: Peter Xu <peterx@xxxxxxxxxx>
Subject: mm: thp: fix soft dirty for migration when split
When splitting a huge migrating PMD, we'll transfer the soft dirty bit
from the huge page to the small pages. However we're possibly using wrong
data since when fetching the bit we're using pmd_soft_dirty() upon a
migration entry. Fix it up.
If my understanding is correct about the problem then if without the patch
there is chance to lose some of the dirty bits in the migrating pmd pages
(on x86_64 we're fetching bit 11 which is part of swap offset instead of
bit 2) and it could potentially corrupt the memory of an userspace program
which depends on the dirty bit.
Link: http://lkml.kernel.org/r/20181206084604.17167-1-peterx@xxxxxxxxxx
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Souptick Joarder <jrdr.linux@xxxxxxxxx>
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/huge_memory.c~mm-thp-fix-soft-dirty-for-migration-when-split
+++ a/mm/huge_memory.c
@@ -2158,7 +2158,10 @@ static void __split_huge_pmd_locked(stru
SetPageDirty(page);
write = pmd_write(old_pmd);
young = pmd_young(old_pmd);
- soft_dirty = pmd_soft_dirty(old_pmd);
+ if (unlikely(pmd_migration))
+ soft_dirty = pmd_swp_soft_dirty(old_pmd);
+ else
+ soft_dirty = pmd_soft_dirty(old_pmd);
/*
* Withdraw the table only after we mark the pmd entry invalid.
_
Patches currently in -mm which might be from peterx@xxxxxxxxxx are
