The patch titled
Subject: Partly revert "mm/thp: carry over dirty bit when thp splits on pmd"
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
partly-revert-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/partly-revert-mm-thp-carry-over-dirty-bit-when-thp-splits-on-pmd.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: Peter Xu <peterx@xxxxxxxxxx>
Subject: Partly revert "mm/thp: carry over dirty bit when thp splits on pmd"
Content-type: text/plain
Anatoly Pugachev reported sparc64 breakage on the patch:
https://lore.kernel.org/r/20221021160603.GA23307@xxxxxxxxxxxx
The sparc64 impl of pte_mkdirty() is definitely slightly special in that
it leverages a code patching mechanism for sun4u/sun4v on relevant pgtable
entry operations.
Before having a clue of why the sparc64 is special and caused the patch to
SIGSEGV the processes, revert the patch for now. The swap path of dirty
bit inheritage is kept because that's using the swap shared code so we
assume it'll not be affected.
Link: https://lkml.kernel.org/r/Y1Wbi4yyVvDtg4zN@x1n
Fixes: 0ccf7f168e17 ("mm/thp: carry over dirty bit when thp splits on pmd")
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Reported-by: Anatoly Pugachev <matorola@xxxxxxxxx>
Tested-by: Anatoly Pugachev <matorola@xxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Andi Kleen <andi.kleen@xxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
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, 6 insertions(+), 3 deletions(-)
--- a/mm/huge_memory.c~partly-revert-mm-thp-carry-over-dirty-bit-when-thp-splits-on-pmd
+++ a/mm/huge_memory.c
@@ -2206,9 +2206,12 @@ 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);
+ /*
+ * NOTE: we don't do pte_mkdirty when dirty==true
+ * because it breaks sparc64 which can sigsegv
+ * random process. Need to revisit when we figure
+ * out what is special with sparc64.
+ */
if (soft_dirty)
entry = pte_mksoft_dirty(entry);
if (uffd_wp)
_
Patches currently in -mm which might be from peterx@xxxxxxxxxx are
partly-revert-mm-thp-carry-over-dirty-bit-when-thp-splits-on-pmd.patch
selftests-vm-use-memfd-for-uffd-hugetlb-tests.patch
selftests-vm-use-memfd-for-hugetlb-madvise-test.patch
selftests-vm-use-memfd-for-hugepage-mremap-test.patch
selftests-vm-drop-mnt-point-for-hugetlb-in-run_vmtestssh.patch
mm-hugetlb-unify-clearing-of-restorereserve-for-private-pages.patch
revert-mm-uffd-fix-warning-without-pte_marker_uffd_wp-compiled-in.patch
