mm/mprotect: use long for page accountings and retval

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>

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index b6b10101bea725323cda960ddd06682854eb3629..e3aa336df900ea1d2b9ac2d03651e4edb00cb95b 100644 (file)
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -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);
 
@@ -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)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 329ed67edd7644aa1a20b2a4be0cd0f1643458fc..4ac5ea4b584c924d08a01eb5ed1c6c5012637c4d 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -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,

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index a82f410241671db67ed405688c6c14c31c0f4584..a0d6d09800649bab86644ced44747aeb80697a86 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -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)
 {
@@ -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;

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index d3558248a0f0dc900777b5206ae80524c09eea63..a86b8f15e2f0975dc419fac895c7815bfbf74abe 100644 (file)
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -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);
 

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 71358e45a742f3ea2d66a8e4fd900e07a7c86d0f..0af22ab59ea80e8c6e1ab1e4ba047982c890e3ca 100644 (file)
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -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;
@@ -353,13 +353,13 @@ 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;
 
@@ -367,7 +367,7 @@ static inline unsigned long change_pmd_range(struct mmu_gather *tlb,
 
        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_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 {
@@ -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);
@@ -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);