The patch titled
Subject: mm/thp: carry over dirty bit when thp splits on pmd
has been added to the -mm mm-unstable branch. Its filename is
mm-thp-carry-over-dirty-bit-when-thp-splits-on-pmd.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-thp-carry-over-dirty-bit-when-thp-splits-on-pmd.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: Peter Xu <peterx@xxxxxxxxxx>
Subject: mm/thp: carry over dirty bit when thp splits on pmd
Date: Thu, 11 Aug 2022 12:13:28 -0400
Carry over the dirty bit from pmd to pte when a huge pmd splits. It
shouldn't be a correctness issue since when pmd_dirty() we'll have the
page marked dirty anyway, however having dirty bit carried over helps the
next initial writes of split ptes on some archs like x86.
Link: https://lkml.kernel.org/r/20220811161331.37055-5-peterx@xxxxxxxxxx
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Reviewed-by: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Andi Kleen <andi.kleen@xxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: "Kirill A . Shutemov" <kirill@xxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Nadav Amit <nadav.amit@xxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/mm/huge_memory.c~mm-thp-carry-over-dirty-bit-when-thp-splits-on-pmd
+++ a/mm/huge_memory.c
@@ -2027,7 +2027,7 @@ static void __split_huge_pmd_locked(stru
pgtable_t pgtable;
pmd_t old_pmd, _pmd;
bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false;
- bool anon_exclusive = false;
+ bool anon_exclusive = false, dirty = false;
unsigned long addr;
int i;
@@ -2116,8 +2116,10 @@ static void __split_huge_pmd_locked(stru
uffd_wp = pmd_swp_uffd_wp(old_pmd);
} else {
page = pmd_page(old_pmd);
- if (pmd_dirty(old_pmd))
+ if (pmd_dirty(old_pmd)) {
+ dirty = true;
SetPageDirty(page);
+ }
write = pmd_write(old_pmd);
young = pmd_young(old_pmd);
soft_dirty = pmd_soft_dirty(old_pmd);
@@ -2183,6 +2185,9 @@ static void __split_huge_pmd_locked(stru
entry = pte_wrprotect(entry);
if (!young)
entry = pte_mkold(entry);
+ /* NOTE: this may set soft-dirty too on some archs */
+ if (dirty)
+ entry = pte_mkdirty(entry);
if (soft_dirty)
entry = pte_mksoft_dirty(entry);
if (uffd_wp)
_
Patches currently in -mm which might be from peterx@xxxxxxxxxx are
mm-smaps-dont-access-young-dirty-bit-if-pte-unpresent.patch
mm-uffd-reset-write-protection-when-unregister-with-wp-mode.patch
mm-x86-use-swp_type_bits-in-3-level-swap-macros.patch
mm-swap-comment-all-the-ifdef-in-swapopsh.patch
mm-swap-add-swp_offset_pfn-to-fetch-pfn-from-swap-entry.patch
mm-thp-carry-over-dirty-bit-when-thp-splits-on-pmd.patch
mm-remember-young-dirty-bit-for-page-migrations.patch
mm-swap-cache-maximum-swapfile-size-when-init-swap.patch
mm-swap-cache-swap-migration-a-d-bits-support.patch
