[PATCH RFC 0/5] mm/autonuma: replace savedwrite infrastructure

[PATCH RFC 0/5] mm/autonuma: replace savedwrite infrastructure

[David Hildenbrand]

As discussed in my talk at LPC, we can reuse the same mechanism for
deciding whether to map a pte writable when upgrading permissions via
mprotect() -- e.g., PROT_READ -> PROT_READ|PROT_WRITE -- to replace the
savedwrite infrastructure used for NUMA hinting faults (e.g., PROT_NONE
-> PROT_READ|PROT_WRITE). Instead of maintaining previous write permissions
for a pte/pmd, we re-determine if the pte/pmd can be writable.

The big benefit is that we have a common logic for deciding whether we can
map a pte/pmd writable on protection changes.

For private mappings, there should be no difference -- from
what I understand, that is what autonuma benchmarks care about.

I ran autonumabench on a system with 2 NUMA nodes, 96 GiB each via:
	perf stat --null --repeat 10

The numa1 benchmark is quite noisy in my environment. I suspect that there
is no actual change in performance, even though the numbers indicate that
this series might improve performance slightly.

numa1:
	mm-stable:   156.75 +- 11.67 seconds time elapsed  ( +-  7.44% )
	mm-stable++: 147.50 +- 9.35 seconds time elapsed  ( +-  6.34% )

numa2:
	mm-stable:   15.9834 +- 0.0589 seconds time elapsed  ( +-  0.37% )
	mm-stable++: 16.1467 +- 0.0946 seconds time elapsed  ( +-  0.59% )

It is worth noting that for shared writable mappings that require
writenotify, we will only avoid write faults if the pte/pmd is dirty
(inherited from the older mprotect logic). If we ever care about optimizing
that further, we'd need a different mechanism to identify whether the FS
still needs to get notified on the next write access. In any case, such an
optimiztion will then not be autonuma-specific, but mprotect() permission
upgrades would similarly benefit from it.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>

David Hildenbrand (4):
  mm/mprotect: minor can_change_pte_writable() cleanups
  mm/huge_memory: try avoiding write faults when changing PMD protection
  mm/autonuma: use can_change_(pte|pmd)_writable() to replace savedwrite
  mm: remove unused savedwrite infrastructure

Nadav Amit (1):
  mm/mprotect: allow clean exclusive anon pages to be writable

 arch/powerpc/include/asm/book3s/64/pgtable.h | 80 +-------------------
 arch/powerpc/kvm/book3s_hv_rm_mmu.c          |  2 +-
 include/linux/mm.h                           |  2 +
 include/linux/pgtable.h                      | 24 ------
 mm/debug_vm_pgtable.c                        | 32 --------
 mm/huge_memory.c                             | 66 ++++++++++++----
 mm/ksm.c                                     |  9 +--
 mm/memory.c                                  | 19 ++++-
 mm/mprotect.c                                | 23 +++---
 9 files changed, 93 insertions(+), 164 deletions(-)

-- 
2.37.3

[PATCH RFC 1/5] mm/mprotect: allow clean exclusive anon pages to be writable

[David Hildenbrand]

From: Nadav Amit <namit@vmware.com>

Anonymous pages might have the dirty bit clear, but this should not
prevent mprotect from making them writable if they are exclusive.
Therefore, skip the test whether the page is dirty in this case.

Note that there are already other ways to get a writable PTE mapping an
anonymous page that is clean: for example, via MADV_FREE. In an ideal
world, we'd have a different indication from the FS whether writenotify
is still required.

Signed-off-by: Nadav Amit <namit@vmware.com>
[ comment for dirty/clean handling; return directly; update description ]
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 mm/mprotect.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/mm/mprotect.c b/mm/mprotect.c
index ed013f836b4a..c6c13a0a4bcc 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -45,7 +45,7 @@ static inline bool can_change_pte_writable(struct vm_area_struct *vma,
 
 	VM_BUG_ON(!(vma->vm_flags & VM_WRITE) || pte_write(pte));
 
-	if (pte_protnone(pte) || !pte_dirty(pte))
+	if (pte_protnone(pte))
 		return false;
 
 	/* Do we need write faults for softdirty tracking? */
@@ -64,11 +64,15 @@ static inline bool can_change_pte_writable(struct vm_area_struct *vma,
 		 * the PT lock.
 		 */
 		page = vm_normal_page(vma, addr, pte);
-		if (!page || !PageAnon(page) || !PageAnonExclusive(page))
-			return false;
+		return page && PageAnon(page) && PageAnonExclusive(page);
 	}
 
-	return true;
+	/*
+	 * Shared mapping: "clean" might indicate that the FS still has to be
+	 * notified via a write fault once first -- see vma_wants_writenotify().
+	 * If "dirty", the assumtion is that there already was a write fault.
+	 */
+	return pte_dirty(pte);
 }
 
 static unsigned long change_pte_range(struct mmu_gather *tlb,
-- 
2.37.3

[PATCH RFC 2/5] mm/mprotect: minor can_change_pte_writable() cleanups

[David Hildenbrand]

We want to replicate this code for handling PMDs soon. No need to crash
the kernel, warning and rejecting is good enough. As this will no longer
get optimized out, drop the pte_write() check: no harm would be done.

While at it, add a comment why PROT_NONE mapped pages are excluded.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 mm/mprotect.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/mprotect.c b/mm/mprotect.c
index c6c13a0a4bcc..95323bc9a951 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -43,8 +43,10 @@ static inline bool can_change_pte_writable(struct vm_area_struct *vma,
 {
 	struct page *page;
 
-	VM_BUG_ON(!(vma->vm_flags & VM_WRITE) || pte_write(pte));
+	if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE)))
+		return false;
 
+	/* Don't touch entries that are not even readable (NUMA hinting). */
 	if (pte_protnone(pte))
 		return false;
 
-- 
2.37.3

[PATCH RFC 3/5] mm/huge_memory: try avoiding write faults when changing PMD protection

[David Hildenbrand]

Let's replicate what we have for PTEs in can_change_pte_writable() also
for PMDs.

While this might look like a pure performance improvement, we'll us this to
get rid of savedwrite handling in do_huge_pmd_numa_page() next. Place
do_huge_pmd_numa_page() stategicly good for that purpose.

Note that MM_CP_TRY_CHANGE_WRITABLE is currently only set when we come
via mprotect_fixup().

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 mm/huge_memory.c | 38 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 36 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 2f18896c8f9a..e5ce3e11d4ae 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1386,6 +1386,36 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf)
 	return VM_FAULT_FALLBACK;
 }
 
+static inline bool can_change_pmd_writable(struct vm_area_struct *vma,
+					   unsigned long addr, pmd_t pmd)
+{
+	struct page *page;
+
+	if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE)))
+		return false;
+
+	/* Don't touch entries that are not even readable (NUMA hinting). */
+	if (pmd_protnone(pmd))
+		return false;
+
+	/* Do we need write faults for softdirty tracking? */
+	if (vma_soft_dirty_enabled(vma) && !pmd_soft_dirty(pmd))
+		return false;
+
+	/* Do we need write faults for uffd-wp tracking? */
+	if (userfaultfd_huge_pmd_wp(vma, pmd))
+		return false;
+
+	if (!(vma->vm_flags & VM_SHARED)) {
+		/* See can_change_pte_writable(). */
+		page = vm_normal_page_pmd(vma, addr, pmd);
+		return page && PageAnon(page) && !PageAnonExclusive(page);
+	}
+
+	/* See can_change_pte_writable(). */
+	return pmd_dirty(pmd);
+}
+
 /* FOLL_FORCE can write to even unwritable PMDs in COW mappings. */
 static inline bool can_follow_write_pmd(pmd_t pmd, struct page *page,
 					struct vm_area_struct *vma,
@@ -1889,13 +1919,17 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 		 */
 		entry = pmd_clear_uffd_wp(entry);
 	}
+
+	/* See change_pte_range(). */
+	if ((cp_flags & MM_CP_TRY_CHANGE_WRITABLE) && !pmd_write(entry) &&
+	    can_change_pmd_writable(vma, addr, entry))
+		entry = pmd_mkwrite(entry);
+
 	ret = HPAGE_PMD_NR;
 	set_pmd_at(mm, addr, pmd, entry);
 
 	if (huge_pmd_needs_flush(oldpmd, entry))
 		tlb_flush_pmd_range(tlb, addr, HPAGE_PMD_SIZE);
-
-	BUG_ON(vma_is_anonymous(vma) && !preserve_write && pmd_write(entry));
 unlock:
 	spin_unlock(ptl);
 	return ret;
-- 
2.37.3

[PATCH RFC 4/5] mm/autonuma: use can_change_(pte|pmd)_writable() to replace savedwrite

[David Hildenbrand]

commit b191f9b106ea ("mm: numa: preserve PTE write permissions across a
NUMA hinting fault") added remembering write permissions using ordinary
pte_write() for PROT_NONE mapped pages to avoid write faults when
remapping the page !PROT_NONE on NUMA hinting faults.

That commit noted:

    The patch looks hacky but the alternatives looked worse. The tidest was
    to rewalk the page tables after a hinting fault but it was more complex
    than this approach and the performance was worse. It's not generally
    safe to just mark the page writable during the fault if it's a write
    fault as it may have been read-only for COW so that approach was
    discarded.

Later, commit 288bc54949fc ("mm/autonuma: let architecture override how
the write bit should be stashed in a protnone pte.") introduced a family
of savedwrite PTE functions that didn't necessarily improve the whole
situation.

One confusing thing is that nowadays, if a page is pte_protnone()
and pte_savedwrite() then also pte_write() is true. Another source of
confusion is that there is only a single pte_mk_savedwrite() call in the
kernel. All other write-protection code seems to silently rely on
pte_wrprotect().

Ever since PageAnonExclusive was introduced and we started using it in
mprotect context via commit 64fe24a3e05e ("mm/mprotect: try avoiding write
faults for exclusive anonymous pages when changing protection"), we do
have machinery in place to avoid write faults when changing protection,
which is exactly what we want to do here.

Let's similarly do what ordinary mprotect() does nowadays when upgrading
write permissions and reuse can_change_pte_writable() and
can_change_pmd_writable() to detect if we can upgrade PTE permissions to be
writable.

For anonymous pages there should be absolutely no change: if an
anonymous page is not exclusive, it could not have been mapped writable --
because only exclusive anonymous pages can be mapped writable.

However, there *might* be a change for writable shared mappings that
require writenotify: if they are not dirty, we cannot map them writable.
While it might not matter in practice, we'd need a different way to
identify whether writenotify is actually required -- and ordinary mprotect
would benefit from that as well.

We'll remove all savedwrite leftovers next.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 include/linux/mm.h |  2 ++
 mm/huge_memory.c   | 28 +++++++++++++++++-----------
 mm/ksm.c           |  9 ++++-----
 mm/memory.c        | 19 ++++++++++++++++---
 mm/mprotect.c      |  7 ++-----
 5 files changed, 41 insertions(+), 24 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8a5ad9d050bf..20061a9f7f47 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1954,6 +1954,8 @@ extern unsigned long move_page_tables(struct vm_area_struct *vma,
 #define  MM_CP_UFFD_WP_ALL                 (MM_CP_UFFD_WP | \
 					    MM_CP_UFFD_WP_RESOLVE)
 
+bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr,
+			     pte_t pte);
 extern unsigned long change_protection(struct mmu_gather *tlb,
 			      struct vm_area_struct *vma, unsigned long start,
 			      unsigned long end, pgprot_t newprot,
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e5ce3e11d4ae..f148d1295d2e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1507,8 +1507,7 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
 	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
 	int page_nid = NUMA_NO_NODE;
 	int target_nid, last_cpupid = (-1 & LAST_CPUPID_MASK);
-	bool migrated = false;
-	bool was_writable = pmd_savedwrite(oldpmd);
+	bool try_change_writable, migrated = false;
 	int flags = 0;
 
 	vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
@@ -1517,13 +1516,22 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
 		goto out;
 	}
 
+	/* See mprotect_fixup(). */
+	if (vma->vm_flags & VM_SHARED)
+		try_change_writable = vma_wants_writenotify(vma, vma->vm_page_prot);
+	else
+		try_change_writable = !!(vma->vm_flags & VM_WRITE);
+
 	pmd = pmd_modify(oldpmd, vma->vm_page_prot);
 	page = vm_normal_page_pmd(vma, haddr, pmd);
 	if (!page)
 		goto out_map;
 
 	/* See similar comment in do_numa_page for explanation */
-	if (!was_writable)
+	if (try_change_writable && !pmd_write(pmd) &&
+	     can_change_pmd_writable(vma, vmf->address, pmd))
+		pmd = pmd_mkwrite(pmd);
+	if (!pmd_write(pmd))
 		flags |= TNF_NO_GROUP;
 
 	page_nid = page_to_nid(page);
@@ -1568,8 +1576,12 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf)
 	/* Restore the PMD */
 	pmd = pmd_modify(oldpmd, vma->vm_page_prot);
 	pmd = pmd_mkyoung(pmd);
-	if (was_writable)
+
+	/* Similar to mprotect() protection updates, avoid write faults. */
+	if (try_change_writable && !pmd_write(pmd) &&
+	     can_change_pmd_writable(vma, vmf->address, pmd))
 		pmd = pmd_mkwrite(pmd);
+
 	set_pmd_at(vma->vm_mm, haddr, vmf->pmd, pmd);
 	update_mmu_cache_pmd(vma, vmf->address, vmf->pmd);
 	spin_unlock(vmf->ptl);
@@ -1809,11 +1821,10 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 	struct mm_struct *mm = vma->vm_mm;
 	spinlock_t *ptl;
 	pmd_t oldpmd, entry;
-	bool preserve_write;
-	int ret;
 	bool prot_numa = cp_flags & MM_CP_PROT_NUMA;
 	bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
 	bool uffd_wp_resolve = cp_flags & MM_CP_UFFD_WP_RESOLVE;
+	int ret = 1;
 
 	tlb_change_page_size(tlb, HPAGE_PMD_SIZE);
 
@@ -1824,9 +1835,6 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 	if (!ptl)
 		return 0;
 
-	preserve_write = prot_numa && pmd_write(*pmd);
-	ret = 1;
-
 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
 	if (is_swap_pmd(*pmd)) {
 		swp_entry_t entry = pmd_to_swp_entry(*pmd);
@@ -1906,8 +1914,6 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 	oldpmd = pmdp_invalidate_ad(vma, addr, pmd);
 
 	entry = pmd_modify(oldpmd, newprot);
-	if (preserve_write)
-		entry = pmd_mk_savedwrite(entry);
 	if (uffd_wp) {
 		entry = pmd_wrprotect(entry);
 		entry = pmd_mkuffd_wp(entry);
diff --git a/mm/ksm.c b/mm/ksm.c
index fd6d03cb0463..40baecec117a 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1065,7 +1065,6 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page,
 
 	anon_exclusive = PageAnonExclusive(page);
 	if (pte_write(*pvmw.pte) || pte_dirty(*pvmw.pte) ||
-	    (pte_protnone(*pvmw.pte) && pte_savedwrite(*pvmw.pte)) ||
 	    anon_exclusive || mm_tlb_flush_pending(mm)) {
 		pte_t entry;
 
@@ -1103,11 +1102,11 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page,
 
 		if (pte_dirty(entry))
 			set_page_dirty(page);
+		entry = pte_mkclean(entry);
+
+		if (pte_write(entry))
+			entry = pte_wrprotect(entry);
 
-		if (pte_protnone(entry))
-			entry = pte_mkclean(pte_clear_savedwrite(entry));
-		else
-			entry = pte_mkclean(pte_wrprotect(entry));
 		set_pte_at_notify(mm, pvmw.address, pvmw.pte, entry);
 	}
 	*orig_pte = *pvmw.pte;
diff --git a/mm/memory.c b/mm/memory.c
index b994784158f5..8df1b77767cb 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4676,12 +4676,12 @@ int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
 static vm_fault_t do_numa_page(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
+	bool try_change_writable;
 	struct page *page = NULL;
 	int page_nid = NUMA_NO_NODE;
 	int last_cpupid;
 	int target_nid;
 	pte_t pte, old_pte;
-	bool was_writable = pte_savedwrite(vmf->orig_pte);
 	int flags = 0;
 
 	/*
@@ -4696,6 +4696,12 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
 		goto out;
 	}
 
+	/* See mprotect_fixup(). */
+	if (vma->vm_flags & VM_SHARED)
+		try_change_writable = vma_wants_writenotify(vma, vma->vm_page_prot);
+	else
+		try_change_writable = !!(vma->vm_flags & VM_WRITE);
+
 	/* Get the normal PTE  */
 	old_pte = ptep_get(vmf->pte);
 	pte = pte_modify(old_pte, vma->vm_page_prot);
@@ -4716,7 +4722,10 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
 	 * pte_dirty has unpredictable behaviour between PTE scan updates,
 	 * background writeback, dirty balancing and application behaviour.
 	 */
-	if (!was_writable)
+	if (try_change_writable && !pte_write(pte) &&
+	     can_change_pte_writable(vma, vmf->address, pte))
+		pte = pte_mkwrite(pte);
+	if (!pte_write(pte))
 		flags |= TNF_NO_GROUP;
 
 	/*
@@ -4771,8 +4780,12 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
 	old_pte = ptep_modify_prot_start(vma, vmf->address, vmf->pte);
 	pte = pte_modify(old_pte, vma->vm_page_prot);
 	pte = pte_mkyoung(pte);
-	if (was_writable)
+
+	/* Similar to mprotect() protection updates, avoid write faults. */
+	if (try_change_writable && !pte_write(pte) &&
+	     can_change_pte_writable(vma, vmf->address, pte))
 		pte = pte_mkwrite(pte);
+
 	ptep_modify_prot_commit(vma, vmf->address, vmf->pte, old_pte, pte);
 	update_mmu_cache(vma, vmf->address, vmf->pte);
 	pte_unmap_unlock(vmf->pte, vmf->ptl);
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 95323bc9a951..1077906136ff 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -38,8 +38,8 @@
 
 #include "internal.h"
 
-static inline bool can_change_pte_writable(struct vm_area_struct *vma,
-					   unsigned long addr, pte_t pte)
+bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr,
+			     pte_t pte)
 {
 	struct page *page;
 
@@ -118,7 +118,6 @@ static unsigned long change_pte_range(struct mmu_gather *tlb,
 		oldpte = *pte;
 		if (pte_present(oldpte)) {
 			pte_t ptent;
-			bool preserve_write = prot_numa && pte_write(oldpte);
 
 			/*
 			 * Avoid trapping faults against the zero or KSM
@@ -174,8 +173,6 @@ static unsigned long change_pte_range(struct mmu_gather *tlb,
 
 			oldpte = ptep_modify_prot_start(vma, addr, pte);
 			ptent = pte_modify(oldpte, newprot);
-			if (preserve_write)
-				ptent = pte_mk_savedwrite(ptent);
 
 			if (uffd_wp) {
 				ptent = pte_wrprotect(ptent);
-- 
2.37.3

[PATCH RFC 5/5] mm: remove unused savedwrite infrastructure

[David Hildenbrand]

NUMA hinting no longer uses savedwrite, let's rip it out.

... and while at it, drop __pte_write() and __pmd_write() on ppc64.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 arch/powerpc/include/asm/book3s/64/pgtable.h | 80 +-------------------
 arch/powerpc/kvm/book3s_hv_rm_mmu.c          |  2 +-
 include/linux/pgtable.h                      | 24 ------
 mm/debug_vm_pgtable.c                        | 32 --------
 4 files changed, 5 insertions(+), 133 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
index 392ff48f77df..b3ddc34d71c1 100644
--- a/arch/powerpc/include/asm/book3s/64/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
@@ -418,35 +418,9 @@ static inline int __ptep_test_and_clear_young(struct mm_struct *mm,
 #define __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSH
 #define pmdp_clear_flush_young pmdp_test_and_clear_young
 
-static inline int __pte_write(pte_t pte)
-{
-	return !!(pte_raw(pte) & cpu_to_be64(_PAGE_WRITE));
-}
-
-#ifdef CONFIG_NUMA_BALANCING
-#define pte_savedwrite pte_savedwrite
-static inline bool pte_savedwrite(pte_t pte)
-{
-	/*
-	 * Saved write ptes are prot none ptes that doesn't have
-	 * privileged bit sit. We mark prot none as one which has
-	 * present and pviliged bit set and RWX cleared. To mark
-	 * protnone which used to have _PAGE_WRITE set we clear
-	 * the privileged bit.
-	 */
-	return !(pte_raw(pte) & cpu_to_be64(_PAGE_RWX | _PAGE_PRIVILEGED));
-}
-#else
-#define pte_savedwrite pte_savedwrite
-static inline bool pte_savedwrite(pte_t pte)
-{
-	return false;
-}
-#endif
-
 static inline int pte_write(pte_t pte)
 {
-	return __pte_write(pte) || pte_savedwrite(pte);
+	return !!(pte_raw(pte) & cpu_to_be64(_PAGE_WRITE));
 }
 
 static inline int pte_read(pte_t pte)
@@ -458,24 +432,16 @@ static inline int pte_read(pte_t pte)
 static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addr,
 				      pte_t *ptep)
 {
-	if (__pte_write(*ptep))
+	if (pte_write(*ptep))
 		pte_update(mm, addr, ptep, _PAGE_WRITE, 0, 0);
-	else if (unlikely(pte_savedwrite(*ptep)))
-		pte_update(mm, addr, ptep, 0, _PAGE_PRIVILEGED, 0);
 }
 
 #define __HAVE_ARCH_HUGE_PTEP_SET_WRPROTECT
 static inline void huge_ptep_set_wrprotect(struct mm_struct *mm,
 					   unsigned long addr, pte_t *ptep)
 {
-	/*
-	 * We should not find protnone for hugetlb, but this complete the
-	 * interface.
-	 */
-	if (__pte_write(*ptep))
+	if (pte_write(*ptep))
 		pte_update(mm, addr, ptep, _PAGE_WRITE, 0, 1);
-	else if (unlikely(pte_savedwrite(*ptep)))
-		pte_update(mm, addr, ptep, 0, _PAGE_PRIVILEGED, 1);
 }
 
 #define __HAVE_ARCH_PTEP_GET_AND_CLEAR
@@ -552,36 +518,6 @@ static inline int pte_protnone(pte_t pte)
 	return (pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT | _PAGE_PTE | _PAGE_RWX)) ==
 		cpu_to_be64(_PAGE_PRESENT | _PAGE_PTE);
 }
-
-#define pte_mk_savedwrite pte_mk_savedwrite
-static inline pte_t pte_mk_savedwrite(pte_t pte)
-{
-	/*
-	 * Used by Autonuma subsystem to preserve the write bit
-	 * while marking the pte PROT_NONE. Only allow this
-	 * on PROT_NONE pte
-	 */
-	VM_BUG_ON((pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT | _PAGE_RWX | _PAGE_PRIVILEGED)) !=
-		  cpu_to_be64(_PAGE_PRESENT | _PAGE_PRIVILEGED));
-	return __pte_raw(pte_raw(pte) & cpu_to_be64(~_PAGE_PRIVILEGED));
-}
-
-#define pte_clear_savedwrite pte_clear_savedwrite
-static inline pte_t pte_clear_savedwrite(pte_t pte)
-{
-	/*
-	 * Used by KSM subsystem to make a protnone pte readonly.
-	 */
-	VM_BUG_ON(!pte_protnone(pte));
-	return __pte_raw(pte_raw(pte) | cpu_to_be64(_PAGE_PRIVILEGED));
-}
-#else
-#define pte_clear_savedwrite pte_clear_savedwrite
-static inline pte_t pte_clear_savedwrite(pte_t pte)
-{
-	VM_WARN_ON(1);
-	return __pte_raw(pte_raw(pte) & cpu_to_be64(~_PAGE_WRITE));
-}
 #endif /* CONFIG_NUMA_BALANCING */
 
 static inline bool pte_hw_valid(pte_t pte)
@@ -658,8 +594,6 @@ static inline unsigned long pte_pfn(pte_t pte)
 /* Generic modifiers for PTE bits */
 static inline pte_t pte_wrprotect(pte_t pte)
 {
-	if (unlikely(pte_savedwrite(pte)))
-		return pte_clear_savedwrite(pte);
 	return __pte_raw(pte_raw(pte) & cpu_to_be64(~_PAGE_WRITE));
 }
 
@@ -1156,8 +1090,6 @@ static inline pte_t *pmdp_ptep(pmd_t *pmd)
 #define pmd_mkclean(pmd)	pte_pmd(pte_mkclean(pmd_pte(pmd)))
 #define pmd_mkyoung(pmd)	pte_pmd(pte_mkyoung(pmd_pte(pmd)))
 #define pmd_mkwrite(pmd)	pte_pmd(pte_mkwrite(pmd_pte(pmd)))
-#define pmd_mk_savedwrite(pmd)	pte_pmd(pte_mk_savedwrite(pmd_pte(pmd)))
-#define pmd_clear_savedwrite(pmd)	pte_pmd(pte_clear_savedwrite(pmd_pte(pmd)))
 
 #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
 #define pmd_soft_dirty(pmd)    pte_soft_dirty(pmd_pte(pmd))
@@ -1179,8 +1111,6 @@ static inline int pmd_protnone(pmd_t pmd)
 #endif /* CONFIG_NUMA_BALANCING */
 
 #define pmd_write(pmd)		pte_write(pmd_pte(pmd))
-#define __pmd_write(pmd)	__pte_write(pmd_pte(pmd))
-#define pmd_savedwrite(pmd)	pte_savedwrite(pmd_pte(pmd))
 
 #define pmd_access_permitted pmd_access_permitted
 static inline bool pmd_access_permitted(pmd_t pmd, bool write)
@@ -1258,10 +1188,8 @@ static inline int __pmdp_test_and_clear_young(struct mm_struct *mm,
 static inline void pmdp_set_wrprotect(struct mm_struct *mm, unsigned long addr,
 				      pmd_t *pmdp)
 {
-	if (__pmd_write((*pmdp)))
+	if (pmd_write(*pmdp))
 		pmd_hugepage_update(mm, addr, pmdp, _PAGE_WRITE, 0);
-	else if (unlikely(pmd_savedwrite(*pmdp)))
-		pmd_hugepage_update(mm, addr, pmdp, 0, _PAGE_PRIVILEGED);
 }
 
 /*
diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
index 5a05953ae13f..9182324dbef9 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -265,7 +265,7 @@ long kvmppc_do_h_enter(struct kvm *kvm, unsigned long flags,
 		}
 		pte = kvmppc_read_update_linux_pte(ptep, writing);
 		if (pte_present(pte) && !pte_protnone(pte)) {
-			if (writing && !__pte_write(pte))
+			if (writing && !pte_write(pte))
 				/* make the actual HPTE be read-only */
 				ptel = hpte_make_readonly(ptel);
 			is_ci = pte_ci(pte);
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index d13b4f7cc5be..02d88fdb44af 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -472,30 +472,6 @@ static inline pte_t pte_sw_mkyoung(pte_t pte)
 #define pte_sw_mkyoung	pte_sw_mkyoung
 #endif
 
-#ifndef pte_savedwrite
-#define pte_savedwrite pte_write
-#endif
-
-#ifndef pte_mk_savedwrite
-#define pte_mk_savedwrite pte_mkwrite
-#endif
-
-#ifndef pte_clear_savedwrite
-#define pte_clear_savedwrite pte_wrprotect
-#endif
-
-#ifndef pmd_savedwrite
-#define pmd_savedwrite pmd_write
-#endif
-
-#ifndef pmd_mk_savedwrite
-#define pmd_mk_savedwrite pmd_mkwrite
-#endif
-
-#ifndef pmd_clear_savedwrite
-#define pmd_clear_savedwrite pmd_wrprotect
-#endif
-
 #ifndef __HAVE_ARCH_PMDP_SET_WRPROTECT
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static inline void pmdp_set_wrprotect(struct mm_struct *mm,
diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
index dc7df1254f0a..5dae04c05d79 100644
--- a/mm/debug_vm_pgtable.c
+++ b/mm/debug_vm_pgtable.c
@@ -175,18 +175,6 @@ static void __init pte_advanced_tests(struct pgtable_debug_args *args)
 	ptep_get_and_clear_full(args->mm, args->vaddr, args->ptep, 1);
 }
 
-static void __init pte_savedwrite_tests(struct pgtable_debug_args *args)
-{
-	pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot_none);
-
-	if (!IS_ENABLED(CONFIG_NUMA_BALANCING))
-		return;
-
-	pr_debug("Validating PTE saved write\n");
-	WARN_ON(!pte_savedwrite(pte_mk_savedwrite(pte_clear_savedwrite(pte))));
-	WARN_ON(pte_savedwrite(pte_clear_savedwrite(pte_mk_savedwrite(pte))));
-}
-
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static void __init pmd_basic_tests(struct pgtable_debug_args *args, int idx)
 {
@@ -306,22 +294,6 @@ static void __init pmd_leaf_tests(struct pgtable_debug_args *args)
 	WARN_ON(!pmd_leaf(pmd));
 }
 
-static void __init pmd_savedwrite_tests(struct pgtable_debug_args *args)
-{
-	pmd_t pmd;
-
-	if (!IS_ENABLED(CONFIG_NUMA_BALANCING))
-		return;
-
-	if (!has_transparent_hugepage())
-		return;
-
-	pr_debug("Validating PMD saved write\n");
-	pmd = pfn_pmd(args->fixed_pmd_pfn, args->page_prot_none);
-	WARN_ON(!pmd_savedwrite(pmd_mk_savedwrite(pmd_clear_savedwrite(pmd))));
-	WARN_ON(pmd_savedwrite(pmd_clear_savedwrite(pmd_mk_savedwrite(pmd))));
-}
-
 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
 static void __init pud_basic_tests(struct pgtable_debug_args *args, int idx)
 {
@@ -455,7 +427,6 @@ static void __init pmd_advanced_tests(struct pgtable_debug_args *args) { }
 static void __init pud_advanced_tests(struct pgtable_debug_args *args) { }
 static void __init pmd_leaf_tests(struct pgtable_debug_args *args) { }
 static void __init pud_leaf_tests(struct pgtable_debug_args *args) { }
-static void __init pmd_savedwrite_tests(struct pgtable_debug_args *args) { }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
@@ -1292,9 +1263,6 @@ static int __init debug_vm_pgtable(void)
 	pmd_leaf_tests(&args);
 	pud_leaf_tests(&args);
 
-	pte_savedwrite_tests(&args);
-	pmd_savedwrite_tests(&args);
-
 	pte_special_tests(&args);
 	pte_protnone_tests(&args);
 	pmd_protnone_tests(&args);
-- 
2.37.3