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mm/mprotect: use long for page accountings and retval
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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>
Acked-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: James Houghton <jthoughton@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Peter Xu authored and Andrew Morton committed Jan 19, 2023
1 parent 6b7cea9 commit a79390f
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Showing 5 changed files with 19 additions and 19 deletions.
4 changes: 2 additions & 2 deletions include/linux/hugetlb.h
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Original file line number Diff line number Diff line change
Expand Up @@ -248,7 +248,7 @@ void hugetlb_vma_lock_release(struct kref *kref);

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);

Expand Down Expand Up @@ -437,7 +437,7 @@ static inline void move_hugetlb_state(struct folio *old_folio,
{
}

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)
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2 changes: 1 addition & 1 deletion include/linux/mm.h
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Original file line number Diff line number Diff line change
Expand Up @@ -2132,7 +2132,7 @@ static inline bool vma_wants_manual_pte_write_upgrade(struct vm_area_struct *vma
}
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,
Expand Down
4 changes: 2 additions & 2 deletions mm/hugetlb.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6615,7 +6615,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
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)
{
Expand All @@ -6624,7 +6624,7 @@ unsigned long hugetlb_change_protection(struct vm_area_struct *vma,
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;
Expand Down
2 changes: 1 addition & 1 deletion mm/mempolicy.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -631,7 +631,7 @@ unsigned long change_prot_numa(struct vm_area_struct *vma,
unsigned long addr, unsigned long end)
{
struct mmu_gather tlb;
int nr_updated;
long nr_updated;

tlb_gather_mmu(&tlb, vma->vm_mm);

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26 changes: 13 additions & 13 deletions mm/mprotect.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -80,13 +80,13 @@ bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr,
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;
Expand Down Expand Up @@ -353,21 +353,21 @@ uffd_wp_protect_file(struct vm_area_struct *vma, unsigned long cp_flags)
} \
} 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;

range.start = 0;

pmd = pmd_offset(pud, addr);
do {
unsigned long this_pages;
long this_pages;

next = pmd_addr_end(addr, end);

Expand Down Expand Up @@ -437,13 +437,13 @@ static inline unsigned long change_pmd_range(struct mmu_gather *tlb,
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 {
Expand All @@ -458,13 +458,13 @@ static inline unsigned long change_pud_range(struct mmu_gather *tlb,
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 {
Expand All @@ -479,14 +479,14 @@ static inline unsigned long change_p4d_range(struct mmu_gather *tlb,
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);
Expand All @@ -505,12 +505,12 @@ static unsigned long change_protection_range(struct mmu_gather *tlb,
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);

Expand Down

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