+ mm-mprotect-use-long-for-page-accountings-and-retval.patch added to mm-unstable branch

+ mm-mprotect-use-long-for-page-accountings-and-retval.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: mm/mprotect: use long for page accountings and retval
has been added to the -mm mm-unstable branch.  Its filename is
     mm-mprotect-use-long-for-page-accountings-and-retval.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mprotect-use-long-for-page-accountings-and-retval.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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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

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branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days

------------------------------------------------------
From: Peter Xu <peterx@redhat.com>
Subject: mm/mprotect: use long for page accountings and retval
Date: Wed, 4 Jan 2023 17:52:06 -0500

Switch to use type "long" for page accountings and retval across the whole
procedure of change_protection().

The change should have shrinked the possible maximum page number to be
half comparing to previous (ULONG_MAX / 2), but it shouldn't overflow on
any system either because the maximum possible pages touched by change
protection should be ULONG_MAX / PAGE_SIZE.

Two reasons to switch from "unsigned long" to "long":

  1. It suites better on count_vm_numa_events(), whose 2nd parameter takes
     a long type.

  2. It paves way for returning negative (error) values in the future.

Currently the only caller that consumes this retval is change_prot_numa(),
where the unsigned long was converted to an int.  Since at it, touching up
the numa code to also take a long, so it'll avoid any possible overflow
too during the int-size convertion.

Link: https://lkml.kernel.org/r/20230104225207.1066932-3-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/hugetlb.h |    4 ++--
 include/linux/mm.h      |    2 +-
 mm/hugetlb.c            |    4 ++--
 mm/mempolicy.c          |    2 +-
 mm/mprotect.c           |   26 +++++++++++++-------------
 5 files changed, 19 insertions(+), 19 deletions(-)

--- a/include/linux/hugetlb.h~mm-mprotect-use-long-for-page-accountings-and-retval
+++ a/include/linux/hugetlb.h
@@ -248,7 +248,7 @@ void hugetlb_vma_lock_release(struct kre
 
 int pmd_huge(pmd_t pmd);
 int pud_huge(pud_t pud);
-unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
+long hugetlb_change_protection(struct vm_area_struct *vma,
 		unsigned long address, unsigned long end, pgprot_t newprot,
 		unsigned long cp_flags);
 
@@ -437,7 +437,7 @@ static inline void move_hugetlb_state(st
 {
 }
 
-static inline unsigned long hugetlb_change_protection(
+static inline long hugetlb_change_protection(
 			struct vm_area_struct *vma, unsigned long address,
 			unsigned long end, pgprot_t newprot,
 			unsigned long cp_flags)
--- a/include/linux/mm.h~mm-mprotect-use-long-for-page-accountings-and-retval
+++ a/include/linux/mm.h
@@ -2132,7 +2132,7 @@ static inline bool vma_wants_manual_pte_
 }
 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,
+extern long change_protection(struct mmu_gather *tlb,
 			      struct vm_area_struct *vma, unsigned long start,
 			      unsigned long end, unsigned long cp_flags);
 extern int mprotect_fixup(struct mmu_gather *tlb, struct vm_area_struct *vma,
--- a/mm/hugetlb.c~mm-mprotect-use-long-for-page-accountings-and-retval
+++ a/mm/hugetlb.c
@@ -6615,7 +6615,7 @@ long follow_hugetlb_page(struct mm_struc
 	return i ? i : err;
 }
 
-unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
+long hugetlb_change_protection(struct vm_area_struct *vma,
 		unsigned long address, unsigned long end,
 		pgprot_t newprot, unsigned long cp_flags)
 {
@@ -6624,7 +6624,7 @@ unsigned long hugetlb_change_protection(
 	pte_t *ptep;
 	pte_t pte;
 	struct hstate *h = hstate_vma(vma);
-	unsigned long pages = 0, psize = huge_page_size(h);
+	long pages = 0, psize = huge_page_size(h);
 	bool shared_pmd = false;
 	struct mmu_notifier_range range;
 	unsigned long last_addr_mask;
--- a/mm/mempolicy.c~mm-mprotect-use-long-for-page-accountings-and-retval
+++ a/mm/mempolicy.c
@@ -631,7 +631,7 @@ unsigned long change_prot_numa(struct vm
 			unsigned long addr, unsigned long end)
 {
 	struct mmu_gather tlb;
-	int nr_updated;
+	long nr_updated;
 
 	tlb_gather_mmu(&tlb, vma->vm_mm);
 
--- a/mm/mprotect.c~mm-mprotect-use-long-for-page-accountings-and-retval
+++ a/mm/mprotect.c
@@ -80,13 +80,13 @@ bool can_change_pte_writable(struct vm_a
 	return pte_dirty(pte);
 }
 
-static unsigned long change_pte_range(struct mmu_gather *tlb,
+static long change_pte_range(struct mmu_gather *tlb,
 		struct vm_area_struct *vma, pmd_t *pmd, unsigned long addr,
 		unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 {
 	pte_t *pte, oldpte;
 	spinlock_t *ptl;
-	unsigned long pages = 0;
+	long pages = 0;
 	int target_node = NUMA_NO_NODE;
 	bool prot_numa = cp_flags & MM_CP_PROT_NUMA;
 	bool uffd_wp = cp_flags & MM_CP_UFFD_WP;
@@ -353,13 +353,13 @@ uffd_wp_protect_file(struct vm_area_stru
 		}							\
 	} while (0)
 
-static inline unsigned long change_pmd_range(struct mmu_gather *tlb,
+static inline long change_pmd_range(struct mmu_gather *tlb,
 		struct vm_area_struct *vma, pud_t *pud, unsigned long addr,
 		unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 {
 	pmd_t *pmd;
 	unsigned long next;
-	unsigned long pages = 0;
+	long pages = 0;
 	unsigned long nr_huge_updates = 0;
 	struct mmu_notifier_range range;
 
@@ -367,7 +367,7 @@ static inline unsigned long change_pmd_r
 
 	pmd = pmd_offset(pud, addr);
 	do {
-		unsigned long this_pages;
+		long this_pages;
 
 		next = pmd_addr_end(addr, end);
 
@@ -437,13 +437,13 @@ next:
 	return pages;
 }
 
-static inline unsigned long change_pud_range(struct mmu_gather *tlb,
+static inline long change_pud_range(struct mmu_gather *tlb,
 		struct vm_area_struct *vma, p4d_t *p4d, unsigned long addr,
 		unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 {
 	pud_t *pud;
 	unsigned long next;
-	unsigned long pages = 0;
+	long pages = 0;
 
 	pud = pud_offset(p4d, addr);
 	do {
@@ -458,13 +458,13 @@ static inline unsigned long change_pud_r
 	return pages;
 }
 
-static inline unsigned long change_p4d_range(struct mmu_gather *tlb,
+static inline long change_p4d_range(struct mmu_gather *tlb,
 		struct vm_area_struct *vma, pgd_t *pgd, unsigned long addr,
 		unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 {
 	p4d_t *p4d;
 	unsigned long next;
-	unsigned long pages = 0;
+	long pages = 0;
 
 	p4d = p4d_offset(pgd, addr);
 	do {
@@ -479,14 +479,14 @@ static inline unsigned long change_p4d_r
 	return pages;
 }
 
-static unsigned long change_protection_range(struct mmu_gather *tlb,
+static long change_protection_range(struct mmu_gather *tlb,
 		struct vm_area_struct *vma, unsigned long addr,
 		unsigned long end, pgprot_t newprot, unsigned long cp_flags)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	pgd_t *pgd;
 	unsigned long next;
-	unsigned long pages = 0;
+	long pages = 0;
 
 	BUG_ON(addr >= end);
 	pgd = pgd_offset(mm, addr);
@@ -505,12 +505,12 @@ static unsigned long change_protection_r
 	return pages;
 }
 
-unsigned long change_protection(struct mmu_gather *tlb,
+long change_protection(struct mmu_gather *tlb,
 		       struct vm_area_struct *vma, unsigned long start,
 		       unsigned long end, unsigned long cp_flags)
 {
 	pgprot_t newprot = vma->vm_page_prot;
-	unsigned long pages;
+	long pages;
 
 	BUG_ON((cp_flags & MM_CP_UFFD_WP_ALL) == MM_CP_UFFD_WP_ALL);
 
_

Patches currently in -mm which might be from peterx@redhat.com are

mm-hugetlb-pre-allocate-pgtable-pages-for-uffd-wr-protects.patch
mm-uffd-fix-pte-marker-when-fork-without-fork-event.patch
mm-fix-a-few-rare-cases-of-using-swapin-error-pte-marker.patch
mm-uffd-always-wr-protect-pte-in-ptepmd_mkuffd_wp.patch
mm-hugetlb-let-vma_offset_start-to-return-start.patch
mm-hugetlb-dont-wait-for-migration-entry-during-follow-page.patch
mm-hugetlb-document-huge_pte_offset-usage.patch
mm-hugetlb-move-swap-entry-handling-into-vma-lock-when-faulted.patch
mm-hugetlb-make-userfaultfd_huge_must_wait-safe-to-pmd-unshare.patch
mm-hugetlb-make-hugetlb_follow_page_mask-safe-to-pmd-unshare.patch
mm-hugetlb-make-follow_hugetlb_page-safe-to-pmd-unshare.patch
mm-hugetlb-make-walk_hugetlb_range-safe-to-pmd-unshare.patch
mm-hugetlb-introduce-hugetlb_walk.patch
mm-mprotect-use-long-for-page-accountings-and-retval.patch
mm-uffd-detect-pgtable-allocation-failures.patch