The quilt patch titled
Subject: mm/memory: ignore writable bit in folio_pte_batch()
has been removed from the -mm tree. Its filename was
mm-memory-ignore-writable-bit-in-folio_pte_batch.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm/memory: ignore writable bit in folio_pte_batch()
Date: Mon, 29 Jan 2024 13:46:49 +0100
.. and conditionally return to the caller if any PTE except the first
one is writable. fork() has to make sure to properly write-protect in
case any PTE is writable. Other users (e.g., page unmaping) are expected
to not care.
Link: https://lkml.kernel.org/r/20240129124649.189745-16-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx>
Cc: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Cc: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Dinh Nguyen <dinguyen@xxxxxxxxxx>
Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx>
Cc: Paul Walmsley <paul.walmsley@xxxxxxxxxx>
Cc: Russell King (Oracle) <linux@xxxxxxxxxxxxxxx>
Cc: Sven Schnelle <svens@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 30 ++++++++++++++++++++++++------
1 file changed, 24 insertions(+), 6 deletions(-)
--- a/mm/memory.c~mm-memory-ignore-writable-bit-in-folio_pte_batch
+++ a/mm/memory.c
@@ -968,7 +968,7 @@ static inline pte_t __pte_batch_clear_ig
pte = pte_mkclean(pte);
if (likely(flags & FPB_IGNORE_SOFT_DIRTY))
pte = pte_clear_soft_dirty(pte);
- return pte_mkold(pte);
+ return pte_wrprotect(pte_mkold(pte));
}
/*
@@ -976,21 +976,32 @@ static inline pte_t __pte_batch_clear_ig
* pages of the same folio.
*
* All PTEs inside a PTE batch have the same PTE bits set, excluding the PFN,
- * the accessed bit, dirty bit (with FPB_IGNORE_DIRTY) and soft-dirty bit
- * (with FPB_IGNORE_SOFT_DIRTY).
+ * the accessed bit, writable bit, dirty bit (with FPB_IGNORE_DIRTY) and
+ * soft-dirty bit (with FPB_IGNORE_SOFT_DIRTY).
+ *
+ * If "any_writable" is set, it will indicate if any other PTE besides the
+ * first (given) PTE is writable.
*/
static inline int folio_pte_batch(struct folio *folio, unsigned long addr,
- pte_t *start_ptep, pte_t pte, int max_nr, fpb_t flags)
+ pte_t *start_ptep, pte_t pte, int max_nr, fpb_t flags,
+ bool *any_writable)
{
unsigned long folio_end_pfn = folio_pfn(folio) + folio_nr_pages(folio);
const pte_t *end_ptep = start_ptep + max_nr;
pte_t expected_pte = __pte_batch_clear_ignored(pte_next_pfn(pte), flags);
pte_t *ptep = start_ptep + 1;
+ bool writable;
+
+ if (any_writable)
+ *any_writable = false;
VM_WARN_ON_FOLIO(!pte_present(pte), folio);
while (ptep != end_ptep) {
- pte = __pte_batch_clear_ignored(ptep_get(ptep), flags);
+ pte = ptep_get(ptep);
+ if (any_writable)
+ writable = !!pte_write(pte);
+ pte = __pte_batch_clear_ignored(pte, flags);
if (!pte_same(pte, expected_pte))
break;
@@ -1003,6 +1014,9 @@ static inline int folio_pte_batch(struct
if (pte_pfn(pte) == folio_end_pfn)
break;
+ if (any_writable)
+ *any_writable |= writable;
+
expected_pte = pte_next_pfn(expected_pte);
ptep++;
}
@@ -1024,6 +1038,7 @@ copy_present_ptes(struct vm_area_struct
{
struct page *page;
struct folio *folio;
+ bool any_writable;
fpb_t flags = 0;
int err, nr;
@@ -1044,7 +1059,8 @@ copy_present_ptes(struct vm_area_struct
if (!vma_soft_dirty_enabled(src_vma))
flags |= FPB_IGNORE_SOFT_DIRTY;
- nr = folio_pte_batch(folio, addr, src_pte, pte, max_nr, flags);
+ nr = folio_pte_batch(folio, addr, src_pte, pte, max_nr, flags,
+ &any_writable);
folio_ref_add(folio, nr);
if (folio_test_anon(folio)) {
if (unlikely(folio_try_dup_anon_rmap_ptes(folio, page,
@@ -1058,6 +1074,8 @@ copy_present_ptes(struct vm_area_struct
folio_dup_file_rmap_ptes(folio, page, nr);
rss[mm_counter_file(folio)] += nr;
}
+ if (any_writable)
+ pte = pte_mkwrite(pte, src_vma);
__copy_present_ptes(dst_vma, src_vma, dst_pte, src_pte, pte,
addr, nr);
return nr;
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
mm-memory-factor-out-zapping-of-present-pte-into-zap_present_pte.patch
mm-memory-handle-page-case-in-zap_present_pte-separately.patch
mm-memory-further-separate-anon-and-pagecache-folio-handling-in-zap_present_pte.patch
mm-memory-factor-out-zapping-folio-pte-into-zap_present_folio_pte.patch
mm-mmu_gather-pass-delay_rmap-instead-of-encoded-page-to-__tlb_remove_page_size.patch
mm-mmu_gather-define-encoded_page_flag_delay_rmap.patch
mm-mmu_gather-add-tlb_remove_tlb_entries.patch
mm-mmu_gather-add-__tlb_remove_folio_pages.patch
mm-mmu_gather-improve-cond_resched-handling-with-large-folios-and-expensive-page-freeing.patch
mm-memory-optimize-unmap-zap-with-pte-mapped-thp.patch
