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-rw-r--r--mm/memory.c53
1 files changed, 44 insertions, 9 deletions
diff --git a/mm/memory.c b/mm/memory.c
index fc38d4ed9ad..c8b5b9435a9 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -108,6 +108,17 @@ static int __init disable_randmaps(char *s)
}
__setup("norandmaps", disable_randmaps);
+static unsigned long zero_pfn __read_mostly;
+
+/*
+ * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
+ */
+static int __init init_zero_pfn(void)
+{
+ zero_pfn = page_to_pfn(ZERO_PAGE(0));
+ return 0;
+}
+core_initcall(init_zero_pfn);
/*
* If a p?d_bad entry is found while walking page tables, report
@@ -499,7 +510,9 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
if (HAVE_PTE_SPECIAL) {
if (likely(!pte_special(pte)))
goto check_pfn;
- if (!(vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP)))
+ if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
+ return NULL;
+ if (pfn != zero_pfn)
print_bad_pte(vma, addr, pte, NULL);
return NULL;
}
@@ -1144,9 +1157,14 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
goto no_page;
if ((flags & FOLL_WRITE) && !pte_write(pte))
goto unlock;
+
page = vm_normal_page(vma, address, pte);
- if (unlikely(!page))
- goto bad_page;
+ if (unlikely(!page)) {
+ if ((flags & FOLL_DUMP) ||
+ pte_pfn(pte) != zero_pfn)
+ goto bad_page;
+ page = pte_page(pte);
+ }
if (flags & FOLL_GET)
get_page(page);
@@ -2084,10 +2102,19 @@ gotten:
if (unlikely(anon_vma_prepare(vma)))
goto oom;
- VM_BUG_ON(old_page == ZERO_PAGE(0));
- new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
- if (!new_page)
- goto oom;
+
+ if (pte_pfn(orig_pte) == zero_pfn) {
+ new_page = alloc_zeroed_user_highpage_movable(vma, address);
+ if (!new_page)
+ goto oom;
+ } else {
+ new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
+ if (!new_page)
+ goto oom;
+ cow_user_page(new_page, old_page, address, vma);
+ }
+ __SetPageUptodate(new_page);
+
/*
* Don't let another task, with possibly unlocked vma,
* keep the mlocked page.
@@ -2097,8 +2124,6 @@ gotten:
clear_page_mlock(old_page);
unlock_page(old_page);
}
- cow_user_page(new_page, old_page, address, vma);
- __SetPageUptodate(new_page);
if (mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))
goto oom_free_new;
@@ -2639,6 +2664,15 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
spinlock_t *ptl;
pte_t entry;
+ if (HAVE_PTE_SPECIAL && !(flags & FAULT_FLAG_WRITE)) {
+ entry = pte_mkspecial(pfn_pte(zero_pfn, vma->vm_page_prot));
+ ptl = pte_lockptr(mm, pmd);
+ spin_lock(ptl);
+ if (!pte_none(*page_table))
+ goto unlock;
+ goto setpte;
+ }
+
/* Allocate our own private page. */
pte_unmap(page_table);
@@ -2662,6 +2696,7 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
inc_mm_counter(mm, anon_rss);
page_add_new_anon_rmap(page, vma, address);
+setpte:
set_pte_at(mm, address, page_table, entry);
/* No need to invalidate - it was non-present before */