1 files changed, 256 insertions, 0 deletions

diff --git a/mm/fremap.c b/mm/fremap.c
new file mode 100644
index 000000000000..3235fb77c133
--- /dev/null
+++ b/mm/fremap.c
@@ -0,0 +1,256 @@
+/*
+ *   linux/mm/fremap.c
+ * 
+ * Explicit pagetable population and nonlinear (random) mappings support.
+ *
+ * started by Ingo Molnar, Copyright (C) 2002, 2003
+ */
+
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/file.h>
+#include <linux/mman.h>
+#include <linux/pagemap.h>
+#include <linux/swapops.h>
+#include <linux/rmap.h>
+#include <linux/module.h>
+#include <linux/syscalls.h>
+
+#include <asm/mmu_context.h>
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+
+static inline void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
+                        unsigned long addr, pte_t *ptep)
+{
+        pte_t pte = *ptep;
+
+        if (pte_none(pte))
+                return;
+        if (pte_present(pte)) {
+                unsigned long pfn = pte_pfn(pte);
+
+                flush_cache_page(vma, addr, pfn);
+                pte = ptep_clear_flush(vma, addr, ptep);
+                if (pfn_valid(pfn)) {
+                        struct page *page = pfn_to_page(pfn);
+                        if (!PageReserved(page)) {
+                                if (pte_dirty(pte))
+                                        set_page_dirty(page);
+                                page_remove_rmap(page);
+                                page_cache_release(page);
+                                dec_mm_counter(mm, rss);
+                        }
+                }
+        } else {
+                if (!pte_file(pte))
+                        free_swap_and_cache(pte_to_swp_entry(pte));
+                pte_clear(mm, addr, ptep);
+        }
+}
+
+/*
+ * Install a file page to a given virtual memory address, release any
+ * previously existing mapping.
+ */
+int install_page(struct mm_struct *mm, struct vm_area_struct *vma,
+                unsigned long addr, struct page *page, pgprot_t prot)
+{
+        struct inode *inode;
+        pgoff_t size;
+        int err = -ENOMEM;
+        pte_t *pte;
+        pmd_t *pmd;
+        pud_t *pud;
+        pgd_t *pgd;
+        pte_t pte_val;
+
+        pgd = pgd_offset(mm, addr);
+        spin_lock(&mm->page_table_lock);
+        
+        pud = pud_alloc(mm, pgd, addr);
+        if (!pud)
+                goto err_unlock;
+
+        pmd = pmd_alloc(mm, pud, addr);
+        if (!pmd)
+                goto err_unlock;
+
+        pte = pte_alloc_map(mm, pmd, addr);
+        if (!pte)
+                goto err_unlock;
+
+        /*
+         * This page may have been truncated. Tell the
+         * caller about it.
+         */
+        err = -EINVAL;
+        inode = vma->vm_file->f_mapping->host;
+        size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+        if (!page->mapping || page->index >= size)
+                goto err_unlock;
+
+        zap_pte(mm, vma, addr, pte);
+
+        inc_mm_counter(mm,rss);
+        flush_icache_page(vma, page);
+        set_pte_at(mm, addr, pte, mk_pte(page, prot));
+        page_add_file_rmap(page);
+        pte_val = *pte;
+        pte_unmap(pte);
+        update_mmu_cache(vma, addr, pte_val);
+
+        err = 0;
+err_unlock:
+        spin_unlock(&mm->page_table_lock);
+        return err;
+}
+EXPORT_SYMBOL(install_page);
+
+
+/*
+ * Install a file pte to a given virtual memory address, release any
+ * previously existing mapping.
+ */
+int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
+                unsigned long addr, unsigned long pgoff, pgprot_t prot)
+{
+        int err = -ENOMEM;
+        pte_t *pte;
+        pmd_t *pmd;
+        pud_t *pud;
+        pgd_t *pgd;
+        pte_t pte_val;
+
+        pgd = pgd_offset(mm, addr);
+        spin_lock(&mm->page_table_lock);
+        
+        pud = pud_alloc(mm, pgd, addr);
+        if (!pud)
+                goto err_unlock;
+
+        pmd = pmd_alloc(mm, pud, addr);
+        if (!pmd)
+                goto err_unlock;
+
+        pte = pte_alloc_map(mm, pmd, addr);
+        if (!pte)
+                goto err_unlock;
+
+        zap_pte(mm, vma, addr, pte);
+
+        set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
+        pte_val = *pte;
+        pte_unmap(pte);
+        update_mmu_cache(vma, addr, pte_val);
+        spin_unlock(&mm->page_table_lock);
+        return 0;
+
+err_unlock:
+        spin_unlock(&mm->page_table_lock);
+        return err;
+}
+
+
+/***
+ * sys_remap_file_pages - remap arbitrary pages of a shared backing store
+ *                        file within an existing vma.
+ * @start: start of the remapped virtual memory range
+ * @size: size of the remapped virtual memory range
+ * @prot: new protection bits of the range
+ * @pgoff: to be mapped page of the backing store file
+ * @flags: 0 or MAP_NONBLOCKED - the later will cause no IO.
+ *
+ * this syscall works purely via pagetables, so it's the most efficient
+ * way to map the same (large) file into a given virtual window. Unlike
+ * mmap()/mremap() it does not create any new vmas. The new mappings are
+ * also safe across swapout.
+ *
+ * NOTE: the 'prot' parameter right now is ignored, and the vma's default
+ * protection is used. Arbitrary protections might be implemented in the
+ * future.
+ */
+asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size,
+        unsigned long __prot, unsigned long pgoff, unsigned long flags)
+{
+        struct mm_struct *mm = current->mm;
+        struct address_space *mapping;
+        unsigned long end = start + size;
+        struct vm_area_struct *vma;
+        int err = -EINVAL;
+        int has_write_lock = 0;
+
+        if (__prot)
+                return err;
+        /*
+         * Sanitize the syscall parameters:
+         */
+        start = start & PAGE_MASK;
+        size = size & PAGE_MASK;
+
+        /* Does the address range wrap, or is the span zero-sized? */
+        if (start + size <= start)
+                return err;
+
+        /* Can we represent this offset inside this architecture's pte's? */
+#if PTE_FILE_MAX_BITS < BITS_PER_LONG
+        if (pgoff + (size >> PAGE_SHIFT) >= (1UL << PTE_FILE_MAX_BITS))
+                return err;
+#endif
+
+        /* We need down_write() to change vma->vm_flags. */
+        down_read(&mm->mmap_sem);
+ retry:
+        vma = find_vma(mm, start);
+
+        /*
+         * Make sure the vma is shared, that it supports prefaulting,
+         * and that the remapped range is valid and fully within
+         * the single existing vma.  vm_private_data is used as a
+         * swapout cursor in a VM_NONLINEAR vma (unless VM_RESERVED
+         * or VM_LOCKED, but VM_LOCKED could be revoked later on).
+         */
+        if (vma && (vma->vm_flags & VM_SHARED) &&
+                (!vma->vm_private_data ||
+                        (vma->vm_flags & (VM_NONLINEAR|VM_RESERVED))) &&
+                vma->vm_ops && vma->vm_ops->populate &&
+                        end > start && start >= vma->vm_start &&
+                                end <= vma->vm_end) {
+
+                /* Must set VM_NONLINEAR before any pages are populated. */
+                if (pgoff != linear_page_index(vma, start) &&
+                    !(vma->vm_flags & VM_NONLINEAR)) {
+                        if (!has_write_lock) {
+                                up_read(&mm->mmap_sem);
+                                down_write(&mm->mmap_sem);
+                                has_write_lock = 1;
+                                goto retry;
+                        }
+                        mapping = vma->vm_file->f_mapping;
+                        spin_lock(&mapping->i_mmap_lock);
+                        flush_dcache_mmap_lock(mapping);
+                        vma->vm_flags |= VM_NONLINEAR;
+                        vma_prio_tree_remove(vma, &mapping->i_mmap);
+                        vma_nonlinear_insert(vma, &mapping->i_mmap_nonlinear);
+                        flush_dcache_mmap_unlock(mapping);
+                        spin_unlock(&mapping->i_mmap_lock);
+                }
+
+                err = vma->vm_ops->populate(vma, start, size,
+                                            vma->vm_page_prot,
+                                            pgoff, flags & MAP_NONBLOCK);
+
+                /*
+                 * We can't clear VM_NONLINEAR because we'd have to do
+                 * it after ->populate completes, and that would prevent
+                 * downgrading the lock.  (Locks can't be upgraded).
+                 */
+        }
+        if (likely(!has_write_lock))
+                up_read(&mm->mmap_sem);
+        else
+                up_write(&mm->mmap_sem);
+
+        return err;
+}
+