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;
+}
+