The quilt patch titled
Subject: mm/memory: handle !page case in zap_present_pte() separately
has been removed from the -mm tree. Its filename was
mm-memory-handle-page-case-in-zap_present_pte-separately.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: handle !page case in zap_present_pte() separately
Date: Wed, 14 Feb 2024 21:44:27 +0100
We don't need uptodate accessed/dirty bits, so in theory we could replace
ptep_get_and_clear_full() by an optimized ptep_clear_full() function.
Let's rely on the provided pte.
Further, there is no scenario where we would have to insert uffd-wp
markers when zapping something that is not a normal page (i.e., zeropage).
Add a sanity check to make sure this remains true.
should_zap_folio() no longer has to handle NULL pointers. This change
replaces 2/3 "!page/!folio" checks by a single "!page" one.
Note that arch_check_zapped_pte() on x86-64 checks the HW-dirty bit to
detect shadow stack entries. But for shadow stack entries, the HW dirty
bit (in combination with non-writable PTEs) is set by software. So for
the arch_check_zapped_pte() check, we don't have to sync against HW
setting the HW dirty bit concurrently, it is always set.
Link: https://lkml.kernel.org/r/20240214204435.167852-3-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: "Naveen N. Rao" <naveen.n.rao@xxxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Sven Schnelle <svens@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Yin Fengwei <fengwei.yin@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)
--- a/mm/memory.c~mm-memory-handle-page-case-in-zap_present_pte-separately
+++ a/mm/memory.c
@@ -1499,10 +1499,6 @@ static inline bool should_zap_folio(stru
if (should_zap_cows(details))
return true;
- /* E.g. the caller passes NULL for the case of a zero folio */
- if (!folio)
- return true;
-
/* Otherwise we should only zap non-anon folios */
return !folio_test_anon(folio);
}
@@ -1540,24 +1536,28 @@ static inline void zap_present_pte(struc
int *rss, bool *force_flush, bool *force_break)
{
struct mm_struct *mm = tlb->mm;
- struct folio *folio = NULL;
bool delay_rmap = false;
+ struct folio *folio;
struct page *page;
page = vm_normal_page(vma, addr, ptent);
- if (page)
- folio = page_folio(page);
+ if (!page) {
+ /* We don't need up-to-date accessed/dirty bits. */
+ ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm);
+ arch_check_zapped_pte(vma, ptent);
+ tlb_remove_tlb_entry(tlb, pte, addr);
+ VM_WARN_ON_ONCE(userfaultfd_wp(vma));
+ ksm_might_unmap_zero_page(mm, ptent);
+ return;
+ }
+ folio = page_folio(page);
if (unlikely(!should_zap_folio(details, folio)))
return;
ptent = ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm);
arch_check_zapped_pte(vma, ptent);
tlb_remove_tlb_entry(tlb, pte, addr);
zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent);
- if (unlikely(!page)) {
- ksm_might_unmap_zero_page(mm, ptent);
- return;
- }
if (!folio_test_anon(folio)) {
if (pte_dirty(ptent)) {
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
