1 files changed, 862 insertions, 0 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
new file mode 100644
index 000000000000..884d6d1928bc
--- /dev/null
+++ b/mm/rmap.c
@@ -0,0 +1,862 @@
+/*
+ * mm/rmap.c - physical to virtual reverse mappings
+ *
+ * Copyright 2001, Rik van Riel <riel@conectiva.com.br>
+ * Released under the General Public License (GPL).
+ *
+ * Simple, low overhead reverse mapping scheme.
+ * Please try to keep this thing as modular as possible.
+ *
+ * Provides methods for unmapping each kind of mapped page:
+ * the anon methods track anonymous pages, and
+ * the file methods track pages belonging to an inode.
+ *
+ * Original design by Rik van Riel <riel@conectiva.com.br> 2001
+ * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004
+ * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004
+ * Contributions by Hugh Dickins <hugh@veritas.com> 2003, 2004
+ */
+
+/*
+ * Lock ordering in mm:
+ *
+ * inode->i_sem (while writing or truncating, not reading or faulting)
+ *   inode->i_alloc_sem
+ *
+ * When a page fault occurs in writing from user to file, down_read
+ * of mmap_sem nests within i_sem; in sys_msync, i_sem nests within
+ * down_read of mmap_sem; i_sem and down_write of mmap_sem are never
+ * taken together; in truncation, i_sem is taken outermost.
+ *
+ * mm->mmap_sem
+ *   page->flags PG_locked (lock_page)
+ *     mapping->i_mmap_lock
+ *       anon_vma->lock
+ *         mm->page_table_lock
+ *           zone->lru_lock (in mark_page_accessed)
+ *           swap_list_lock (in swap_free etc's swap_info_get)
+ *             mmlist_lock (in mmput, drain_mmlist and others)
+ *             swap_device_lock (in swap_duplicate, swap_info_get)
+ *             mapping->private_lock (in __set_page_dirty_buffers)
+ *             inode_lock (in set_page_dirty's __mark_inode_dirty)
+ *               sb_lock (within inode_lock in fs/fs-writeback.c)
+ *               mapping->tree_lock (widely used, in set_page_dirty,
+ *                         in arch-dependent flush_dcache_mmap_lock,
+ *                         within inode_lock in __sync_single_inode)
+ */
+
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/rmap.h>
+#include <linux/rcupdate.h>
+
+#include <asm/tlbflush.h>
+
+//#define RMAP_DEBUG /* can be enabled only for debugging */
+
+kmem_cache_t *anon_vma_cachep;
+
+static inline void validate_anon_vma(struct vm_area_struct *find_vma)
+{
+#ifdef RMAP_DEBUG
+        struct anon_vma *anon_vma = find_vma->anon_vma;
+        struct vm_area_struct *vma;
+        unsigned int mapcount = 0;
+        int found = 0;
+
+        list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
+                mapcount++;
+                BUG_ON(mapcount > 100000);
+                if (vma == find_vma)
+                        found = 1;
+        }
+        BUG_ON(!found);
+#endif
+}
+
+/* This must be called under the mmap_sem. */
+int anon_vma_prepare(struct vm_area_struct *vma)
+{
+        struct anon_vma *anon_vma = vma->anon_vma;
+
+        might_sleep();
+        if (unlikely(!anon_vma)) {
+                struct mm_struct *mm = vma->vm_mm;
+                struct anon_vma *allocated, *locked;
+
+                anon_vma = find_mergeable_anon_vma(vma);
+                if (anon_vma) {
+                        allocated = NULL;
+                        locked = anon_vma;
+                        spin_lock(&locked->lock);
+                } else {
+                        anon_vma = anon_vma_alloc();
+                        if (unlikely(!anon_vma))
+                                return -ENOMEM;
+                        allocated = anon_vma;
+                        locked = NULL;
+                }
+
+                /* page_table_lock to protect against threads */
+                spin_lock(&mm->page_table_lock);
+                if (likely(!vma->anon_vma)) {
+                        vma->anon_vma = anon_vma;
+                        list_add(&vma->anon_vma_node, &anon_vma->head);
+                        allocated = NULL;
+                }
+                spin_unlock(&mm->page_table_lock);
+
+                if (locked)
+                        spin_unlock(&locked->lock);
+                if (unlikely(allocated))
+                        anon_vma_free(allocated);
+        }
+        return 0;
+}
+
+void __anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next)
+{
+        BUG_ON(vma->anon_vma != next->anon_vma);
+        list_del(&next->anon_vma_node);
+}
+
+void __anon_vma_link(struct vm_area_struct *vma)
+{
+        struct anon_vma *anon_vma = vma->anon_vma;
+
+        if (anon_vma) {
+                list_add(&vma->anon_vma_node, &anon_vma->head);
+                validate_anon_vma(vma);
+        }
+}
+
+void anon_vma_link(struct vm_area_struct *vma)
+{
+        struct anon_vma *anon_vma = vma->anon_vma;
+
+        if (anon_vma) {
+                spin_lock(&anon_vma->lock);
+                list_add(&vma->anon_vma_node, &anon_vma->head);
+                validate_anon_vma(vma);
+                spin_unlock(&anon_vma->lock);
+        }
+}
+
+void anon_vma_unlink(struct vm_area_struct *vma)
+{
+        struct anon_vma *anon_vma = vma->anon_vma;
+        int empty;
+
+        if (!anon_vma)
+                return;
+
+        spin_lock(&anon_vma->lock);
+        validate_anon_vma(vma);
+        list_del(&vma->anon_vma_node);
+
+        /* We must garbage collect the anon_vma if it's empty */
+        empty = list_empty(&anon_vma->head);
+        spin_unlock(&anon_vma->lock);
+
+        if (empty)
+                anon_vma_free(anon_vma);
+}
+
+static void anon_vma_ctor(void *data, kmem_cache_t *cachep, unsigned long flags)
+{
+        if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
+                                                SLAB_CTOR_CONSTRUCTOR) {
+                struct anon_vma *anon_vma = data;
+
+                spin_lock_init(&anon_vma->lock);
+                INIT_LIST_HEAD(&anon_vma->head);
+        }
+}
+
+void __init anon_vma_init(void)
+{
+        anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
+                        0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor, NULL);
+}
+
+/*
+ * Getting a lock on a stable anon_vma from a page off the LRU is
+ * tricky: page_lock_anon_vma rely on RCU to guard against the races.
+ */
+static struct anon_vma *page_lock_anon_vma(struct page *page)
+{
+        struct anon_vma *anon_vma = NULL;
+        unsigned long anon_mapping;
+
+        rcu_read_lock();
+        anon_mapping = (unsigned long) page->mapping;
+        if (!(anon_mapping & PAGE_MAPPING_ANON))
+                goto out;
+        if (!page_mapped(page))
+                goto out;
+
+        anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
+        spin_lock(&anon_vma->lock);
+out:
+        rcu_read_unlock();
+        return anon_vma;
+}
+
+/*
+ * At what user virtual address is page expected in vma?
+ */
+static inline unsigned long
+vma_address(struct page *page, struct vm_area_struct *vma)
+{
+        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+        unsigned long address;
+
+        address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+        if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
+                /* page should be within any vma from prio_tree_next */
+                BUG_ON(!PageAnon(page));
+                return -EFAULT;
+        }
+        return address;
+}
+
+/*
+ * At what user virtual address is page expected in vma? checking that the
+ * page matches the vma: currently only used by unuse_process, on anon pages.
+ */
+unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
+{
+        if (PageAnon(page)) {
+                if ((void *)vma->anon_vma !=
+                    (void *)page->mapping - PAGE_MAPPING_ANON)
+                        return -EFAULT;
+        } else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
+                if (vma->vm_file->f_mapping != page->mapping)
+                        return -EFAULT;
+        } else
+                return -EFAULT;
+        return vma_address(page, vma);
+}
+
+/*
+ * Subfunctions of page_referenced: page_referenced_one called
+ * repeatedly from either page_referenced_anon or page_referenced_file.
+ */
+static int page_referenced_one(struct page *page,
+        struct vm_area_struct *vma, unsigned int *mapcount, int ignore_token)
+{
+        struct mm_struct *mm = vma->vm_mm;
+        unsigned long address;
+        pgd_t *pgd;
+        pud_t *pud;
+        pmd_t *pmd;
+        pte_t *pte;
+        int referenced = 0;
+
+        if (!get_mm_counter(mm, rss))
+                goto out;
+        address = vma_address(page, vma);
+        if (address == -EFAULT)
+                goto out;
+
+        spin_lock(&mm->page_table_lock);
+
+        pgd = pgd_offset(mm, address);
+        if (!pgd_present(*pgd))
+                goto out_unlock;
+
+        pud = pud_offset(pgd, address);
+        if (!pud_present(*pud))
+                goto out_unlock;
+
+        pmd = pmd_offset(pud, address);
+        if (!pmd_present(*pmd))
+                goto out_unlock;
+
+        pte = pte_offset_map(pmd, address);
+        if (!pte_present(*pte))
+                goto out_unmap;
+
+        if (page_to_pfn(page) != pte_pfn(*pte))
+                goto out_unmap;
+
+        if (ptep_clear_flush_young(vma, address, pte))
+                referenced++;
+
+        if (mm != current->mm && !ignore_token && has_swap_token(mm))
+                referenced++;
+
+        (*mapcount)--;
+
+out_unmap:
+        pte_unmap(pte);
+out_unlock:
+        spin_unlock(&mm->page_table_lock);
+out:
+        return referenced;
+}
+
+static int page_referenced_anon(struct page *page, int ignore_token)
+{
+        unsigned int mapcount;
+        struct anon_vma *anon_vma;
+        struct vm_area_struct *vma;
+        int referenced = 0;
+
+        anon_vma = page_lock_anon_vma(page);
+        if (!anon_vma)
+                return referenced;
+
+        mapcount = page_mapcount(page);
+        list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
+                referenced += page_referenced_one(page, vma, &mapcount,
+                                                        ignore_token);
+                if (!mapcount)
+                        break;
+        }
+        spin_unlock(&anon_vma->lock);
+        return referenced;
+}
+
+/**
+ * page_referenced_file - referenced check for object-based rmap
+ * @page: the page we're checking references on.
+ *
+ * For an object-based mapped page, find all the places it is mapped and
+ * check/clear the referenced flag.  This is done by following the page->mapping
+ * pointer, then walking the chain of vmas it holds.  It returns the number
+ * of references it found.
+ *
+ * This function is only called from page_referenced for object-based pages.
+ */
+static int page_referenced_file(struct page *page, int ignore_token)
+{
+        unsigned int mapcount;
+        struct address_space *mapping = page->mapping;
+        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+        struct vm_area_struct *vma;
+        struct prio_tree_iter iter;
+        int referenced = 0;
+
+        /*
+         * The caller's checks on page->mapping and !PageAnon have made
+         * sure that this is a file page: the check for page->mapping
+         * excludes the case just before it gets set on an anon page.
+         */
+        BUG_ON(PageAnon(page));
+
+        /*
+         * The page lock not only makes sure that page->mapping cannot
+         * suddenly be NULLified by truncation, it makes sure that the
+         * structure at mapping cannot be freed and reused yet,
+         * so we can safely take mapping->i_mmap_lock.
+         */
+        BUG_ON(!PageLocked(page));
+
+        spin_lock(&mapping->i_mmap_lock);
+
+        /*
+         * i_mmap_lock does not stabilize mapcount at all, but mapcount
+         * is more likely to be accurate if we note it after spinning.
+         */
+        mapcount = page_mapcount(page);
+
+        vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
+                if ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE))
+                                  == (VM_LOCKED|VM_MAYSHARE)) {
+                        referenced++;
+                        break;
+                }
+                referenced += page_referenced_one(page, vma, &mapcount,
+                                                        ignore_token);
+                if (!mapcount)
+                        break;
+        }
+
+        spin_unlock(&mapping->i_mmap_lock);
+        return referenced;
+}
+
+/**
+ * page_referenced - test if the page was referenced
+ * @page: the page to test
+ * @is_locked: caller holds lock on the page
+ *
+ * Quick test_and_clear_referenced for all mappings to a page,
+ * returns the number of ptes which referenced the page.
+ */
+int page_referenced(struct page *page, int is_locked, int ignore_token)
+{
+        int referenced = 0;
+
+        if (!swap_token_default_timeout)
+                ignore_token = 1;
+
+        if (page_test_and_clear_young(page))
+                referenced++;
+
+        if (TestClearPageReferenced(page))
+                referenced++;
+
+        if (page_mapped(page) && page->mapping) {
+                if (PageAnon(page))
+                        referenced += page_referenced_anon(page, ignore_token);
+                else if (is_locked)
+                        referenced += page_referenced_file(page, ignore_token);
+                else if (TestSetPageLocked(page))
+                        referenced++;
+                else {
+                        if (page->mapping)
+                                referenced += page_referenced_file(page,
+                                                                ignore_token);
+                        unlock_page(page);
+                }
+        }
+        return referenced;
+}
+
+/**
+ * page_add_anon_rmap - add pte mapping to an anonymous page
+ * @page:       the page to add the mapping to
+ * @vma:        the vm area in which the mapping is added
+ * @address:    the user virtual address mapped
+ *
+ * The caller needs to hold the mm->page_table_lock.
+ */
+void page_add_anon_rmap(struct page *page,
+        struct vm_area_struct *vma, unsigned long address)
+{
+        struct anon_vma *anon_vma = vma->anon_vma;
+        pgoff_t index;
+
+        BUG_ON(PageReserved(page));
+        BUG_ON(!anon_vma);
+
+        inc_mm_counter(vma->vm_mm, anon_rss);
+
+        anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
+        index = (address - vma->vm_start) >> PAGE_SHIFT;
+        index += vma->vm_pgoff;
+        index >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;
+
+        if (atomic_inc_and_test(&page->_mapcount)) {
+                page->index = index;
+                page->mapping = (struct address_space *) anon_vma;
+                inc_page_state(nr_mapped);
+        }
+        /* else checking page index and mapping is racy */
+}
+
+/**
+ * page_add_file_rmap - add pte mapping to a file page
+ * @page: the page to add the mapping to
+ *
+ * The caller needs to hold the mm->page_table_lock.
+ */
+void page_add_file_rmap(struct page *page)
+{
+        BUG_ON(PageAnon(page));
+        if (!pfn_valid(page_to_pfn(page)) || PageReserved(page))
+                return;
+
+        if (atomic_inc_and_test(&page->_mapcount))
+                inc_page_state(nr_mapped);
+}
+
+/**
+ * page_remove_rmap - take down pte mapping from a page
+ * @page: page to remove mapping from
+ *
+ * Caller needs to hold the mm->page_table_lock.
+ */
+void page_remove_rmap(struct page *page)
+{
+        BUG_ON(PageReserved(page));
+
+        if (atomic_add_negative(-1, &page->_mapcount)) {
+                BUG_ON(page_mapcount(page) < 0);
+                /*
+                 * It would be tidy to reset the PageAnon mapping here,
+                 * but that might overwrite a racing page_add_anon_rmap
+                 * which increments mapcount after us but sets mapping
+                 * before us: so leave the reset to free_hot_cold_page,
+                 * and remember that it's only reliable while mapped.
+                 * Leaving it set also helps swapoff to reinstate ptes
+                 * faster for those pages still in swapcache.
+                 */
+                if (page_test_and_clear_dirty(page))
+                        set_page_dirty(page);
+                dec_page_state(nr_mapped);
+        }
+}
+
+/*
+ * Subfunctions of try_to_unmap: try_to_unmap_one called
+ * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
+ */
+static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
+{
+        struct mm_struct *mm = vma->vm_mm;
+        unsigned long address;
+        pgd_t *pgd;
+        pud_t *pud;
+        pmd_t *pmd;
+        pte_t *pte;
+        pte_t pteval;
+        int ret = SWAP_AGAIN;
+
+        if (!get_mm_counter(mm, rss))
+                goto out;
+        address = vma_address(page, vma);
+        if (address == -EFAULT)
+                goto out;
+
+        /*
+         * We need the page_table_lock to protect us from page faults,
+         * munmap, fork, etc...
+         */
+        spin_lock(&mm->page_table_lock);
+
+        pgd = pgd_offset(mm, address);
+        if (!pgd_present(*pgd))
+                goto out_unlock;
+
+        pud = pud_offset(pgd, address);
+        if (!pud_present(*pud))
+                goto out_unlock;
+
+        pmd = pmd_offset(pud, address);
+        if (!pmd_present(*pmd))
+                goto out_unlock;
+
+        pte = pte_offset_map(pmd, address);
+        if (!pte_present(*pte))
+                goto out_unmap;
+
+        if (page_to_pfn(page) != pte_pfn(*pte))
+                goto out_unmap;
+
+        /*
+         * If the page is mlock()d, we cannot swap it out.
+         * If it's recently referenced (perhaps page_referenced
+         * skipped over this mm) then we should reactivate it.
+         */
+        if ((vma->vm_flags & (VM_LOCKED|VM_RESERVED)) ||
+                        ptep_clear_flush_young(vma, address, pte)) {
+                ret = SWAP_FAIL;
+                goto out_unmap;
+        }
+
+        /*
+         * Don't pull an anonymous page out from under get_user_pages.
+         * GUP carefully breaks COW and raises page count (while holding
+         * page_table_lock, as we have here) to make sure that the page
+         * cannot be freed.  If we unmap that page here, a user write
+         * access to the virtual address will bring back the page, but
+         * its raised count will (ironically) be taken to mean it's not
+         * an exclusive swap page, do_wp_page will replace it by a copy
+         * page, and the user never get to see the data GUP was holding
+         * the original page for.
+         *
+         * This test is also useful for when swapoff (unuse_process) has
+         * to drop page lock: its reference to the page stops existing
+         * ptes from being unmapped, so swapoff can make progress.
+         */
+        if (PageSwapCache(page) &&
+            page_count(page) != page_mapcount(page) + 2) {
+                ret = SWAP_FAIL;
+                goto out_unmap;
+        }
+
+        /* Nuke the page table entry. */
+        flush_cache_page(vma, address, page_to_pfn(page));
+        pteval = ptep_clear_flush(vma, address, pte);
+
+        /* Move the dirty bit to the physical page now the pte is gone. */
+        if (pte_dirty(pteval))
+                set_page_dirty(page);
+
+        if (PageAnon(page)) {
+                swp_entry_t entry = { .val = page->private };
+                /*
+                 * Store the swap location in the pte.
+                 * See handle_pte_fault() ...
+                 */
+                BUG_ON(!PageSwapCache(page));
+                swap_duplicate(entry);
+                if (list_empty(&mm->mmlist)) {
+                        spin_lock(&mmlist_lock);
+                        list_add(&mm->mmlist, &init_mm.mmlist);
+                        spin_unlock(&mmlist_lock);
+                }
+                set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
+                BUG_ON(pte_file(*pte));
+                dec_mm_counter(mm, anon_rss);
+        }
+
+        inc_mm_counter(mm, rss);
+        page_remove_rmap(page);
+        page_cache_release(page);
+
+out_unmap:
+        pte_unmap(pte);
+out_unlock:
+        spin_unlock(&mm->page_table_lock);
+out:
+        return ret;
+}
+
+/*
+ * objrmap doesn't work for nonlinear VMAs because the assumption that
+ * offset-into-file correlates with offset-into-virtual-addresses does not hold.
+ * Consequently, given a particular page and its ->index, we cannot locate the
+ * ptes which are mapping that page without an exhaustive linear search.
+ *
+ * So what this code does is a mini "virtual scan" of each nonlinear VMA which
+ * maps the file to which the target page belongs.  The ->vm_private_data field
+ * holds the current cursor into that scan.  Successive searches will circulate
+ * around the vma's virtual address space.
+ *
+ * So as more replacement pressure is applied to the pages in a nonlinear VMA,
+ * more scanning pressure is placed against them as well.   Eventually pages
+ * will become fully unmapped and are eligible for eviction.
+ *
+ * For very sparsely populated VMAs this is a little inefficient - chances are
+ * there there won't be many ptes located within the scan cluster.  In this case
+ * maybe we could scan further - to the end of the pte page, perhaps.
+ */
+#define CLUSTER_SIZE    min(32*PAGE_SIZE, PMD_SIZE)
+#define CLUSTER_MASK    (~(CLUSTER_SIZE - 1))
+
+static void try_to_unmap_cluster(unsigned long cursor,
+        unsigned int *mapcount, struct vm_area_struct *vma)
+{
+        struct mm_struct *mm = vma->vm_mm;
+        pgd_t *pgd;
+        pud_t *pud;
+        pmd_t *pmd;
+        pte_t *pte;
+        pte_t pteval;
+        struct page *page;
+        unsigned long address;
+        unsigned long end;
+        unsigned long pfn;
+
+        /*
+         * We need the page_table_lock to protect us from page faults,
+         * munmap, fork, etc...
+         */
+        spin_lock(&mm->page_table_lock);
+
+        address = (vma->vm_start + cursor) & CLUSTER_MASK;
+        end = address + CLUSTER_SIZE;
+        if (address < vma->vm_start)
+                address = vma->vm_start;
+        if (end > vma->vm_end)
+                end = vma->vm_end;
+
+        pgd = pgd_offset(mm, address);
+        if (!pgd_present(*pgd))
+                goto out_unlock;
+
+        pud = pud_offset(pgd, address);
+        if (!pud_present(*pud))
+                goto out_unlock;
+
+        pmd = pmd_offset(pud, address);
+        if (!pmd_present(*pmd))
+                goto out_unlock;
+
+        for (pte = pte_offset_map(pmd, address);
+                        address < end; pte++, address += PAGE_SIZE) {
+
+                if (!pte_present(*pte))
+                        continue;
+
+                pfn = pte_pfn(*pte);
+                if (!pfn_valid(pfn))
+                        continue;
+
+                page = pfn_to_page(pfn);
+                BUG_ON(PageAnon(page));
+                if (PageReserved(page))
+                        continue;
+
+                if (ptep_clear_flush_young(vma, address, pte))
+                        continue;
+
+                /* Nuke the page table entry. */
+                flush_cache_page(vma, address, pfn);
+                pteval = ptep_clear_flush(vma, address, pte);
+
+                /* If nonlinear, store the file page offset in the pte. */
+                if (page->index != linear_page_index(vma, address))
+                        set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
+
+                /* Move the dirty bit to the physical page now the pte is gone. */
+                if (pte_dirty(pteval))
+                        set_page_dirty(page);
+
+                page_remove_rmap(page);
+                page_cache_release(page);
+                dec_mm_counter(mm, rss);
+                (*mapcount)--;
+        }
+
+        pte_unmap(pte);
+
+out_unlock:
+        spin_unlock(&mm->page_table_lock);
+}
+
+static int try_to_unmap_anon(struct page *page)
+{
+        struct anon_vma *anon_vma;
+        struct vm_area_struct *vma;
+        int ret = SWAP_AGAIN;
+
+        anon_vma = page_lock_anon_vma(page);
+        if (!anon_vma)
+                return ret;
+
+        list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
+                ret = try_to_unmap_one(page, vma);
+                if (ret == SWAP_FAIL || !page_mapped(page))
+                        break;
+        }
+        spin_unlock(&anon_vma->lock);
+        return ret;
+}
+
+/**
+ * try_to_unmap_file - unmap file page using the object-based rmap method
+ * @page: the page to unmap
+ *
+ * Find all the mappings of a page using the mapping pointer and the vma chains
+ * contained in the address_space struct it points to.
+ *
+ * This function is only called from try_to_unmap for object-based pages.
+ */
+static int try_to_unmap_file(struct page *page)
+{
+        struct address_space *mapping = page->mapping;
+        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+        struct vm_area_struct *vma;
+        struct prio_tree_iter iter;
+        int ret = SWAP_AGAIN;
+        unsigned long cursor;
+        unsigned long max_nl_cursor = 0;
+        unsigned long max_nl_size = 0;
+        unsigned int mapcount;
+
+        spin_lock(&mapping->i_mmap_lock);
+        vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
+                ret = try_to_unmap_one(page, vma);
+                if (ret == SWAP_FAIL || !page_mapped(page))
+                        goto out;
+        }
+
+        if (list_empty(&mapping->i_mmap_nonlinear))
+                goto out;
+
+        list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
+                                                shared.vm_set.list) {
+                if (vma->vm_flags & (VM_LOCKED|VM_RESERVED))
+                        continue;
+                cursor = (unsigned long) vma->vm_private_data;
+                if (cursor > max_nl_cursor)
+                        max_nl_cursor = cursor;
+                cursor = vma->vm_end - vma->vm_start;
+                if (cursor > max_nl_size)
+                        max_nl_size = cursor;
+        }
+
+        if (max_nl_size == 0) { /* any nonlinears locked or reserved */
+                ret = SWAP_FAIL;
+                goto out;
+        }
+
+        /*
+         * We don't try to search for this page in the nonlinear vmas,
+         * and page_referenced wouldn't have found it anyway.  Instead
+         * just walk the nonlinear vmas trying to age and unmap some.
+         * The mapcount of the page we came in with is irrelevant,
+         * but even so use it as a guide to how hard we should try?
+         */
+        mapcount = page_mapcount(page);
+        if (!mapcount)
+                goto out;
+        cond_resched_lock(&mapping->i_mmap_lock);
+
+        max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
+        if (max_nl_cursor == 0)
+                max_nl_cursor = CLUSTER_SIZE;
+
+        do {
+                list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
+                                                shared.vm_set.list) {
+                        if (vma->vm_flags & (VM_LOCKED|VM_RESERVED))
+                                continue;
+                        cursor = (unsigned long) vma->vm_private_data;
+                        while (get_mm_counter(vma->vm_mm, rss) &&
+                                cursor < max_nl_cursor &&
+                                cursor < vma->vm_end - vma->vm_start) {
+                                try_to_unmap_cluster(cursor, &mapcount, vma);
+                                cursor += CLUSTER_SIZE;
+                                vma->vm_private_data = (void *) cursor;
+                                if ((int)mapcount <= 0)
+                                        goto out;
+                        }
+                        vma->vm_private_data = (void *) max_nl_cursor;
+                }
+                cond_resched_lock(&mapping->i_mmap_lock);
+                max_nl_cursor += CLUSTER_SIZE;
+        } while (max_nl_cursor <= max_nl_size);
+
+        /*
+         * Don't loop forever (perhaps all the remaining pages are
+         * in locked vmas).  Reset cursor on all unreserved nonlinear
+         * vmas, now forgetting on which ones it had fallen behind.
+         */
+        list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
+                                                shared.vm_set.list) {
+                if (!(vma->vm_flags & VM_RESERVED))
+                        vma->vm_private_data = NULL;
+        }
+out:
+        spin_unlock(&mapping->i_mmap_lock);
+        return ret;
+}
+
+/**
+ * try_to_unmap - try to remove all page table mappings to a page
+ * @page: the page to get unmapped
+ *
+ * Tries to remove all the page table entries which are mapping this
+ * page, used in the pageout path.  Caller must hold the page lock.
+ * Return values are:
+ *
+ * SWAP_SUCCESS - we succeeded in removing all mappings
+ * SWAP_AGAIN   - we missed a mapping, try again later
+ * SWAP_FAIL    - the page is unswappable
+ */
+int try_to_unmap(struct page *page)
+{
+        int ret;
+
+        BUG_ON(PageReserved(page));
+        BUG_ON(!PageLocked(page));
+
+        if (PageAnon(page))
+                ret = try_to_unmap_anon(page);
+        else
+                ret = try_to_unmap_file(page);
+
+        if (!page_mapped(page))
+                ret = SWAP_SUCCESS;
+        return ret;
+}