mm: mempolicy: Implement change_prot_numa() in terms of change_protection()

This patch converts change_prot_numa() to use change_protection(). As
pte_numa and friends check the PTE bits directly it is necessary for
change_protection() to use pmd_mknuma(). Hence the required
modifications to change_protection() are a little clumsy but the
end result is that most of the numa page table helpers are just one or
two instructions.

Signed-off-by: Mel Gorman <mgorman@suse.de>

5 files changed, 85 insertions, 145 deletions

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index dabb5108d6c0..027ad04ef3a8 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -27,7 +27,8 @@ extern int move_huge_pmd(struct vm_area_struct *vma,
                          unsigned long new_addr, unsigned long old_end,
                          pmd_t *old_pmd, pmd_t *new_pmd);
 extern int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
-                        unsigned long addr, pgprot_t newprot);
+                        unsigned long addr, pgprot_t newprot,
+                        int prot_numa);
 
 enum transparent_hugepage_flag {
         TRANSPARENT_HUGEPAGE_FLAG,
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 471185e29bab..d04c2f0aab36 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1080,7 +1080,7 @@ extern unsigned long do_mremap(unsigned long addr,
                                unsigned long flags, unsigned long new_addr);
 extern unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
                               unsigned long end, pgprot_t newprot,
-                              int dirty_accountable);
+                              int dirty_accountable, int prot_numa);
 extern int mprotect_fixup(struct vm_area_struct *vma,
                           struct vm_area_struct **pprev, unsigned long start,
                           unsigned long end, unsigned long newflags);
@@ -1552,7 +1552,7 @@ static inline pgprot_t vm_get_page_prot(unsigned long vm_flags)
 #endif
 
 #ifdef CONFIG_ARCH_USES_NUMA_PROT_NONE
-void change_prot_numa(struct vm_area_struct *vma,
+unsigned long change_prot_numa(struct vm_area_struct *vma,
                         unsigned long start, unsigned long end);
 #endif
 
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 5723b551c023..d79f7a55bf6f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1147,7 +1147,7 @@ out:
 }
 
 int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
-                unsigned long addr, pgprot_t newprot)
+                unsigned long addr, pgprot_t newprot, int prot_numa)
 {
         struct mm_struct *mm = vma->vm_mm;
         int ret = 0;
@@ -1155,7 +1155,17 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
         if (__pmd_trans_huge_lock(pmd, vma) == 1) {
                 pmd_t entry;
                 entry = pmdp_get_and_clear(mm, addr, pmd);
-                entry = pmd_modify(entry, newprot);
+                if (!prot_numa)
+                        entry = pmd_modify(entry, newprot);
+                else {
+                        struct page *page = pmd_page(*pmd);
+
+                        /* only check non-shared pages */
+                        if (page_mapcount(page) == 1 &&
+                            !pmd_numa(*pmd)) {
+                                entry = pmd_mknuma(entry);
+                        }
+                }
                 set_pmd_at(mm, addr, pmd, entry);
                 spin_unlock(&vma->vm_mm->page_table_lock);
                 ret = 1;
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 51d3ebd8561e..75d4600a5e92 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -568,134 +568,23 @@ static inline int check_pgd_range(struct vm_area_struct *vma,
 
 #ifdef CONFIG_ARCH_USES_NUMA_PROT_NONE
 /*
- * Here we search for not shared page mappings (mapcount == 1) and we
- * set up the pmd/pte_numa on those mappings so the very next access
- * will fire a NUMA hinting page fault.
+ * This is used to mark a range of virtual addresses to be inaccessible.
+ * These are later cleared by a NUMA hinting fault. Depending on these
+ * faults, pages may be migrated for better NUMA placement.
+ *
+ * This is assuming that NUMA faults are handled using PROT_NONE. If
+ * an architecture makes a different choice, it will need further
+ * changes to the core.
  */
-static int
-change_prot_numa_range(struct mm_struct *mm, struct vm_area_struct *vma,
-                        unsigned long address)
-{
-        pgd_t *pgd;
-        pud_t *pud;
-        pmd_t *pmd;
-        pte_t *pte, *_pte;
-        struct page *page;
-        unsigned long _address, end;
-        spinlock_t *ptl;
-        int ret = 0;
-
-        VM_BUG_ON(address & ~PAGE_MASK);
-
-        pgd = pgd_offset(mm, address);
-        if (!pgd_present(*pgd))
-                goto out;
-
-        pud = pud_offset(pgd, address);
-        if (!pud_present(*pud))
-                goto out;
-
-        pmd = pmd_offset(pud, address);
-        if (pmd_none(*pmd))
-                goto out;
-
-        if (pmd_trans_huge_lock(pmd, vma) == 1) {
-                int page_nid;
-                ret = HPAGE_PMD_NR;
-
-                VM_BUG_ON(address & ~HPAGE_PMD_MASK);
-
-                if (pmd_numa(*pmd)) {
-                        spin_unlock(&mm->page_table_lock);
-                        goto out;
-                }
-
-                page = pmd_page(*pmd);
-
-                /* only check non-shared pages */
-                if (page_mapcount(page) != 1) {
-                        spin_unlock(&mm->page_table_lock);
-                        goto out;
-                }
-
-                page_nid = page_to_nid(page);
-
-                if (pmd_numa(*pmd)) {
-                        spin_unlock(&mm->page_table_lock);
-                        goto out;
-                }
-
-                set_pmd_at(mm, address, pmd, pmd_mknuma(*pmd));
-                ret += HPAGE_PMD_NR;
-                /* defer TLB flush to lower the overhead */
-                spin_unlock(&mm->page_table_lock);
-                goto out;
-        }
-
-        if (pmd_trans_unstable(pmd))
-                goto out;
-        VM_BUG_ON(!pmd_present(*pmd));
-
-        end = min(vma->vm_end, (address + PMD_SIZE) & PMD_MASK);
-        pte = pte_offset_map_lock(mm, pmd, address, &ptl);
-        for (_address = address, _pte = pte; _address < end;
-             _pte++, _address += PAGE_SIZE) {
-                pte_t pteval = *_pte;
-                if (!pte_present(pteval))
-                        continue;
-                if (pte_numa(pteval))
-                        continue;
-                page = vm_normal_page(vma, _address, pteval);
-                if (unlikely(!page))
-                        continue;
-                /* only check non-shared pages */
-                if (page_mapcount(page) != 1)
-                        continue;
-
-                set_pte_at(mm, _address, _pte, pte_mknuma(pteval));
-
-                /* defer TLB flush to lower the overhead */
-                ret++;
-        }
-        pte_unmap_unlock(pte, ptl);
-
-        if (ret && !pmd_numa(*pmd)) {
-                spin_lock(&mm->page_table_lock);
-                set_pmd_at(mm, address, pmd, pmd_mknuma(*pmd));
-                spin_unlock(&mm->page_table_lock);
-                /* defer TLB flush to lower the overhead */
-        }
-
-out:
-        return ret;
-}
-
-/* Assumes mmap_sem is held */
-void
-change_prot_numa(struct vm_area_struct *vma,
-                        unsigned long address, unsigned long end)
+unsigned long change_prot_numa(struct vm_area_struct *vma,
+                        unsigned long addr, unsigned long end)
 {
-        struct mm_struct *mm = vma->vm_mm;
-        int progress = 0;
-
-        while (address < end) {
-                VM_BUG_ON(address < vma->vm_start ||
-                          address + PAGE_SIZE > vma->vm_end);
+        int nr_updated;
+        BUILD_BUG_ON(_PAGE_NUMA != _PAGE_PROTNONE);
 
-                progress += change_prot_numa_range(mm, vma, address);
-                address = (address + PMD_SIZE) & PMD_MASK;
-        }
+        nr_updated = change_protection(vma, addr, end, vma->vm_page_prot, 0, 1);
 
-        /*
-         * Flush the TLB for the mm to start the NUMA hinting
-         * page faults after we finish scanning this vma part
-         * if there were any PTE updates
-         */
-        if (progress) {
-                mmu_notifier_invalidate_range_start(vma->vm_mm, address, end);
-                flush_tlb_range(vma, address, end);
-                mmu_notifier_invalidate_range_end(vma->vm_mm, address, end);
-        }
+        return nr_updated;
 }
 #else
 static unsigned long change_prot_numa(struct vm_area_struct *vma,
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 7c3628a8b486..7ef6ae964e8f 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -35,10 +35,11 @@ static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
 }
 #endif
 
-static unsigned long change_pte_range(struct mm_struct *mm, pmd_t *pmd,
+static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
                 unsigned long addr, unsigned long end, pgprot_t newprot,
-                int dirty_accountable)
+                int dirty_accountable, int prot_numa)
 {
+        struct mm_struct *mm = vma->vm_mm;
         pte_t *pte, oldpte;
         spinlock_t *ptl;
         unsigned long pages = 0;
@@ -49,19 +50,39 @@ static unsigned long change_pte_range(struct mm_struct *mm, pmd_t *pmd,
                 oldpte = *pte;
                 if (pte_present(oldpte)) {
                         pte_t ptent;
+                        bool updated = false;
 
                         ptent = ptep_modify_prot_start(mm, addr, pte);
-                        ptent = pte_modify(ptent, newprot);
+                        if (!prot_numa) {
+                                ptent = pte_modify(ptent, newprot);
+                                updated = true;
+                        } else {
+                                struct page *page;
+
+                                page = vm_normal_page(vma, addr, oldpte);
+                                if (page) {
+                                        /* only check non-shared pages */
+                                        if (!pte_numa(oldpte) &&
+                                            page_mapcount(page) == 1) {
+                                                ptent = pte_mknuma(ptent);
+                                                updated = true;
+                                        }
+                                }
+                        }
 
                         /*
                          * Avoid taking write faults for pages we know to be
                          * dirty.
                          */
-                        if (dirty_accountable && pte_dirty(ptent))
+                        if (dirty_accountable && pte_dirty(ptent)) {
                                 ptent = pte_mkwrite(ptent);
+                                updated = true;
+                        }
+
+                        if (updated)
+                                pages++;
 
                         ptep_modify_prot_commit(mm, addr, pte, ptent);
-                        pages++;
                 } else if (IS_ENABLED(CONFIG_MIGRATION) && !pte_file(oldpte)) {
                         swp_entry_t entry = pte_to_swp_entry(oldpte);
 
@@ -83,9 +104,25 @@ static unsigned long change_pte_range(struct mm_struct *mm, pmd_t *pmd,
         return pages;
 }
 
+#ifdef CONFIG_NUMA_BALANCING
+static inline void change_pmd_protnuma(struct mm_struct *mm, unsigned long addr,
+                pmd_t *pmd)
+{
+        spin_lock(&mm->page_table_lock);
+        set_pmd_at(mm, addr & PMD_MASK, pmd, pmd_mknuma(*pmd));
+        spin_unlock(&mm->page_table_lock);
+}
+#else
+static inline void change_pmd_protnuma(struct mm_struct *mm, unsigned long addr,
+                pmd_t *pmd)
+{
+        BUG();
+}
+#endif /* CONFIG_NUMA_BALANCING */
+
 static inline unsigned long change_pmd_range(struct vm_area_struct *vma, pud_t *pud,
                 unsigned long addr, unsigned long end, pgprot_t newprot,
-                int dirty_accountable)
+                int dirty_accountable, int prot_numa)
 {
         pmd_t *pmd;
         unsigned long next;
@@ -97,7 +134,7 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, pud_t *
                 if (pmd_trans_huge(*pmd)) {
                         if (next - addr != HPAGE_PMD_SIZE)
                                 split_huge_page_pmd(vma->vm_mm, pmd);
-                        else if (change_huge_pmd(vma, pmd, addr, newprot)) {
+                        else if (change_huge_pmd(vma, pmd, addr, newprot, prot_numa)) {
                                 pages += HPAGE_PMD_NR;
                                 continue;
                         }
@@ -105,8 +142,11 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, pud_t *
                 }
                 if (pmd_none_or_clear_bad(pmd))
                         continue;
-                pages += change_pte_range(vma->vm_mm, pmd, addr, next, newprot,
-                                 dirty_accountable);
+                pages += change_pte_range(vma, pmd, addr, next, newprot,
+                                 dirty_accountable, prot_numa);
+
+                if (prot_numa)
+                        change_pmd_protnuma(vma->vm_mm, addr, pmd);
         } while (pmd++, addr = next, addr != end);
 
         return pages;
@@ -114,7 +154,7 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, pud_t *
 
 static inline unsigned long change_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
                 unsigned long addr, unsigned long end, pgprot_t newprot,
-                int dirty_accountable)
+                int dirty_accountable, int prot_numa)
 {
         pud_t *pud;
         unsigned long next;
@@ -126,7 +166,7 @@ static inline unsigned long change_pud_range(struct vm_area_struct *vma, pgd_t *
                 if (pud_none_or_clear_bad(pud))
                         continue;
                 pages += change_pmd_range(vma, pud, addr, next, newprot,
-                                 dirty_accountable);
+                                 dirty_accountable, prot_numa);
         } while (pud++, addr = next, addr != end);
 
         return pages;
@@ -134,7 +174,7 @@ static inline unsigned long change_pud_range(struct vm_area_struct *vma, pgd_t *
 
 static unsigned long change_protection_range(struct vm_area_struct *vma,
                 unsigned long addr, unsigned long end, pgprot_t newprot,
-                int dirty_accountable)
+                int dirty_accountable, int prot_numa)
 {
         struct mm_struct *mm = vma->vm_mm;
         pgd_t *pgd;
@@ -150,7 +190,7 @@ static unsigned long change_protection_range(struct vm_area_struct *vma,
                 if (pgd_none_or_clear_bad(pgd))
                         continue;
                 pages += change_pud_range(vma, pgd, addr, next, newprot,
-                                 dirty_accountable);
+                                 dirty_accountable, prot_numa);
         } while (pgd++, addr = next, addr != end);
 
         /* Only flush the TLB if we actually modified any entries: */
@@ -162,7 +202,7 @@ static unsigned long change_protection_range(struct vm_area_struct *vma,
 
 unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
                        unsigned long end, pgprot_t newprot,
-                       int dirty_accountable)
+                       int dirty_accountable, int prot_numa)
 {
         struct mm_struct *mm = vma->vm_mm;
         unsigned long pages;
@@ -171,7 +211,7 @@ unsigned long change_protection(struct vm_area_struct *vma, unsigned long start,
         if (is_vm_hugetlb_page(vma))
                 pages = hugetlb_change_protection(vma, start, end, newprot);
         else
-                pages = change_protection_range(vma, start, end, newprot, dirty_accountable);
+                pages = change_protection_range(vma, start, end, newprot, dirty_accountable, prot_numa);
         mmu_notifier_invalidate_range_end(mm, start, end);
 
         return pages;
@@ -249,7 +289,7 @@ success:
                 dirty_accountable = 1;
         }
 
-        change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable);
+        change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable, 0);
 
         vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
         vm_stat_account(mm, newflags, vma->vm_file, nrpages);