1 files changed, 256 insertions, 324 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
index 068522d8502a..962e2a1e13a0 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -660,17 +660,22 @@ int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
         return 1;
 }
 
+struct page_referenced_arg {
+        int mapcount;
+        int referenced;
+        unsigned long vm_flags;
+        struct mem_cgroup *memcg;
+};
 /*
- * Subfunctions of page_referenced: page_referenced_one called
- * repeatedly from either page_referenced_anon or page_referenced_file.
+ * arg: page_referenced_arg will be passed
  */
 int page_referenced_one(struct page *page, struct vm_area_struct *vma,
-                        unsigned long address, unsigned int *mapcount,
-                        unsigned long *vm_flags)
+                        unsigned long address, void *arg)
 {
         struct mm_struct *mm = vma->vm_mm;
         spinlock_t *ptl;
         int referenced = 0;
+        struct page_referenced_arg *pra = arg;
 
         if (unlikely(PageTransHuge(page))) {
                 pmd_t *pmd;
@@ -682,13 +687,12 @@ int page_referenced_one(struct page *page, struct vm_area_struct *vma,
                 pmd = page_check_address_pmd(page, mm, address,
                                              PAGE_CHECK_ADDRESS_PMD_FLAG, &ptl);
                 if (!pmd)
-                        goto out;
+                        return SWAP_AGAIN;
 
                 if (vma->vm_flags & VM_LOCKED) {
                         spin_unlock(ptl);
-                        *mapcount = 0;  /* break early from loop */
-                        *vm_flags |= VM_LOCKED;
-                        goto out;
+                        pra->vm_flags |= VM_LOCKED;
+                        return SWAP_FAIL; /* To break the loop */
                 }
 
                 /* go ahead even if the pmd is pmd_trans_splitting() */
@@ -704,13 +708,12 @@ int page_referenced_one(struct page *page, struct vm_area_struct *vma,
                  */
                 pte = page_check_address(page, mm, address, &ptl, 0);
                 if (!pte)
-                        goto out;
+                        return SWAP_AGAIN;
 
                 if (vma->vm_flags & VM_LOCKED) {
                         pte_unmap_unlock(pte, ptl);
-                        *mapcount = 0;  /* break early from loop */
-                        *vm_flags |= VM_LOCKED;
-                        goto out;
+                        pra->vm_flags |= VM_LOCKED;
+                        return SWAP_FAIL; /* To break the loop */
                 }
 
                 if (ptep_clear_flush_young_notify(vma, address, pte)) {
@@ -727,113 +730,27 @@ int page_referenced_one(struct page *page, struct vm_area_struct *vma,
                 pte_unmap_unlock(pte, ptl);
         }
 
-        (*mapcount)--;
-
-        if (referenced)
-                *vm_flags |= vma->vm_flags;
-out:
-        return referenced;
-}
-
-static int page_referenced_anon(struct page *page,
-                                struct mem_cgroup *memcg,
-                                unsigned long *vm_flags)
-{
-        unsigned int mapcount;
-        struct anon_vma *anon_vma;
-        pgoff_t pgoff;
-        struct anon_vma_chain *avc;
-        int referenced = 0;
-
-        anon_vma = page_lock_anon_vma_read(page);
-        if (!anon_vma)
-                return referenced;
-
-        mapcount = page_mapcount(page);
-        pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
-        anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
-                struct vm_area_struct *vma = avc->vma;
-                unsigned long address = vma_address(page, vma);
-                /*
-                 * If we are reclaiming on behalf of a cgroup, skip
-                 * counting on behalf of references from different
-                 * cgroups
-                 */
-                if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
-                        continue;
-                referenced += page_referenced_one(page, vma, address,
-                                                  &mapcount, vm_flags);
-                if (!mapcount)
-                        break;
+        if (referenced) {
+                pra->referenced++;
+                pra->vm_flags |= vma->vm_flags;
         }
 
-        page_unlock_anon_vma_read(anon_vma);
-        return referenced;
+        pra->mapcount--;
+        if (!pra->mapcount)
+                return SWAP_SUCCESS; /* To break the loop */
+
+        return SWAP_AGAIN;
 }
 
-/**
- * page_referenced_file - referenced check for object-based rmap
- * @page: the page we're checking references on.
- * @memcg: target memory control group
- * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
- *
- * 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,
-                                struct mem_cgroup *memcg,
-                                unsigned long *vm_flags)
+static bool invalid_page_referenced_vma(struct vm_area_struct *vma, void *arg)
 {
-        unsigned int mapcount;
-        struct address_space *mapping = page->mapping;
-        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
-        struct vm_area_struct *vma;
-        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_mutex.
-         */
-        BUG_ON(!PageLocked(page));
-
-        mutex_lock(&mapping->i_mmap_mutex);
+        struct page_referenced_arg *pra = arg;
+        struct mem_cgroup *memcg = pra->memcg;
 
-        /*
-         * i_mmap_mutex 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_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
-                unsigned long address = vma_address(page, vma);
-                /*
-                 * If we are reclaiming on behalf of a cgroup, skip
-                 * counting on behalf of references from different
-                 * cgroups
-                 */
-                if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
-                        continue;
-                referenced += page_referenced_one(page, vma, address,
-                                                  &mapcount, vm_flags);
-                if (!mapcount)
-                        break;
-        }
+        if (!mm_match_cgroup(vma->vm_mm, memcg))
+                return true;
 
-        mutex_unlock(&mapping->i_mmap_mutex);
-        return referenced;
+        return false;
 }
 
 /**
@@ -851,41 +768,57 @@ int page_referenced(struct page *page,
                     struct mem_cgroup *memcg,
                     unsigned long *vm_flags)
 {
-        int referenced = 0;
+        int ret;
         int we_locked = 0;
+        struct page_referenced_arg pra = {
+                .mapcount = page_mapcount(page),
+                .memcg = memcg,
+        };
+        struct rmap_walk_control rwc = {
+                .rmap_one = page_referenced_one,
+                .arg = (void *)&pra,
+                .anon_lock = page_lock_anon_vma_read,
+        };
 
         *vm_flags = 0;
-        if (page_mapped(page) && page_rmapping(page)) {
-                if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
-                        we_locked = trylock_page(page);
-                        if (!we_locked) {
-                                referenced++;
-                                goto out;
-                        }
-                }
-                if (unlikely(PageKsm(page)))
-                        referenced += page_referenced_ksm(page, memcg,
-                                                                vm_flags);
-                else if (PageAnon(page))
-                        referenced += page_referenced_anon(page, memcg,
-                                                                vm_flags);
-                else if (page->mapping)
-                        referenced += page_referenced_file(page, memcg,
-                                                                vm_flags);
-                if (we_locked)
-                        unlock_page(page);
+        if (!page_mapped(page))
+                return 0;
+
+        if (!page_rmapping(page))
+                return 0;
+
+        if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
+                we_locked = trylock_page(page);
+                if (!we_locked)
+                        return 1;
         }
-out:
-        return referenced;
+
+        /*
+         * If we are reclaiming on behalf of a cgroup, skip
+         * counting on behalf of references from different
+         * cgroups
+         */
+        if (memcg) {
+                rwc.invalid_vma = invalid_page_referenced_vma;
+        }
+
+        ret = rmap_walk(page, &rwc);
+        *vm_flags = pra.vm_flags;
+
+        if (we_locked)
+                unlock_page(page);
+
+        return pra.referenced;
 }
 
 static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
-                            unsigned long address)
+                            unsigned long address, void *arg)
 {
         struct mm_struct *mm = vma->vm_mm;
         pte_t *pte;
         spinlock_t *ptl;
         int ret = 0;
+        int *cleaned = arg;
 
         pte = page_check_address(page, mm, address, &ptl, 1);
         if (!pte)
@@ -904,44 +837,44 @@ static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
 
         pte_unmap_unlock(pte, ptl);
 
-        if (ret)
+        if (ret) {
                 mmu_notifier_invalidate_page(mm, address);
+                (*cleaned)++;
+        }
 out:
-        return ret;
+        return SWAP_AGAIN;
 }
 
-static int page_mkclean_file(struct address_space *mapping, struct page *page)
+static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg)
 {
-        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
-        struct vm_area_struct *vma;
-        int ret = 0;
-
-        BUG_ON(PageAnon(page));
+        if (vma->vm_flags & VM_SHARED)
+                return 0;
 
-        mutex_lock(&mapping->i_mmap_mutex);
-        vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
-                if (vma->vm_flags & VM_SHARED) {
-                        unsigned long address = vma_address(page, vma);
-                        ret += page_mkclean_one(page, vma, address);
-                }
-        }
-        mutex_unlock(&mapping->i_mmap_mutex);
-        return ret;
+        return 1;
 }
 
 int page_mkclean(struct page *page)
 {
-        int ret = 0;
+        int cleaned = 0;
+        struct address_space *mapping;
+        struct rmap_walk_control rwc = {
+                .arg = (void *)&cleaned,
+                .rmap_one = page_mkclean_one,
+                .invalid_vma = invalid_mkclean_vma,
+        };
 
         BUG_ON(!PageLocked(page));
 
-        if (page_mapped(page)) {
-                struct address_space *mapping = page_mapping(page);
-                if (mapping)
-                        ret = page_mkclean_file(mapping, page);
-        }
+        if (!page_mapped(page))
+                return 0;
 
-        return ret;
+        mapping = page_mapping(page);
+        if (!mapping)
+                return 0;
+
+        rmap_walk(page, &rwc);
+
+        return cleaned;
 }
 EXPORT_SYMBOL_GPL(page_mkclean);
 
@@ -1177,17 +1110,17 @@ out:
 }
 
 /*
- * Subfunctions of try_to_unmap: try_to_unmap_one called
- * repeatedly from try_to_unmap_ksm, try_to_unmap_anon or try_to_unmap_file.
+ * @arg: enum ttu_flags will be passed to this argument
  */
 int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
-                     unsigned long address, enum ttu_flags flags)
+                     unsigned long address, void *arg)
 {
         struct mm_struct *mm = vma->vm_mm;
         pte_t *pte;
         pte_t pteval;
         spinlock_t *ptl;
         int ret = SWAP_AGAIN;
+        enum ttu_flags flags = (enum ttu_flags)arg;
 
         pte = page_check_address(page, mm, address, &ptl, 0);
         if (!pte)
@@ -1426,124 +1359,18 @@ static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
         return ret;
 }
 
-bool is_vma_temporary_stack(struct vm_area_struct *vma)
-{
-        int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
-
-        if (!maybe_stack)
-                return false;
-
-        if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
-                                                VM_STACK_INCOMPLETE_SETUP)
-                return true;
-
-        return false;
-}
-
-/**
- * try_to_unmap_anon - unmap or unlock anonymous page using the object-based
- * rmap method
- * @page: the page to unmap/unlock
- * @flags: action and flags
- *
- * Find all the mappings of a page using the mapping pointer and the vma chains
- * contained in the anon_vma struct it points to.
- *
- * This function is only called from try_to_unmap/try_to_munlock for
- * anonymous pages.
- * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
- * where the page was found will be held for write.  So, we won't recheck
- * vm_flags for that VMA.  That should be OK, because that vma shouldn't be
- * 'LOCKED.
- */
-static int try_to_unmap_anon(struct page *page, enum ttu_flags flags)
-{
-        struct anon_vma *anon_vma;
-        pgoff_t pgoff;
-        struct anon_vma_chain *avc;
-        int ret = SWAP_AGAIN;
-
-        anon_vma = page_lock_anon_vma_read(page);
-        if (!anon_vma)
-                return ret;
-
-        pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
-        anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
-                struct vm_area_struct *vma = avc->vma;
-                unsigned long address;
-
-                /*
-                 * During exec, a temporary VMA is setup and later moved.
-                 * The VMA is moved under the anon_vma lock but not the
-                 * page tables leading to a race where migration cannot
-                 * find the migration ptes. Rather than increasing the
-                 * locking requirements of exec(), migration skips
-                 * temporary VMAs until after exec() completes.
-                 */
-                if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) &&
-                                is_vma_temporary_stack(vma))
-                        continue;
-
-                address = vma_address(page, vma);
-                ret = try_to_unmap_one(page, vma, address, flags);
-                if (ret != SWAP_AGAIN || !page_mapped(page))
-                        break;
-        }
-
-        page_unlock_anon_vma_read(anon_vma);
-        return ret;
-}
-
-/**
- * try_to_unmap_file - unmap/unlock file page using the object-based rmap method
- * @page: the page to unmap/unlock
- * @flags: action and flags
- *
- * 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/try_to_munlock for
- * object-based pages.
- * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
- * where the page was found will be held for write.  So, we won't recheck
- * vm_flags for that VMA.  That should be OK, because that vma shouldn't be
- * 'LOCKED.
- */
-static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
+static int try_to_unmap_nonlinear(struct page *page,
+                struct address_space *mapping, struct vm_area_struct *vma)
 {
-        struct address_space *mapping = page->mapping;
-        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
-        struct vm_area_struct *vma;
         int ret = SWAP_AGAIN;
         unsigned long cursor;
         unsigned long max_nl_cursor = 0;
         unsigned long max_nl_size = 0;
         unsigned int mapcount;
 
-        if (PageHuge(page))
-                pgoff = page->index << compound_order(page);
+        list_for_each_entry(vma,
+                &mapping->i_mmap_nonlinear, shared.nonlinear) {
 
-        mutex_lock(&mapping->i_mmap_mutex);
-        vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
-                unsigned long address = vma_address(page, vma);
-                ret = try_to_unmap_one(page, vma, address, flags);
-                if (ret != SWAP_AGAIN || !page_mapped(page))
-                        goto out;
-        }
-
-        if (list_empty(&mapping->i_mmap_nonlinear))
-                goto out;
-
-        /*
-         * We don't bother to try to find the munlocked page in nonlinears.
-         * It's costly. Instead, later, page reclaim logic may call
-         * try_to_unmap(TTU_MUNLOCK) and recover PG_mlocked lazily.
-         */
-        if (TTU_ACTION(flags) == TTU_MUNLOCK)
-                goto out;
-
-        list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
-                                                        shared.nonlinear) {
                 cursor = (unsigned long) vma->vm_private_data;
                 if (cursor > max_nl_cursor)
                         max_nl_cursor = cursor;
@@ -1553,8 +1380,7 @@ static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
         }
 
         if (max_nl_size == 0) { /* all nonlinears locked or reserved ? */
-                ret = SWAP_FAIL;
-                goto out;
+                return SWAP_FAIL;
         }
 
         /*
@@ -1566,7 +1392,8 @@ static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
          */
         mapcount = page_mapcount(page);
         if (!mapcount)
-                goto out;
+                return ret;
+
         cond_resched();
 
         max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
@@ -1574,10 +1401,11 @@ static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
                 max_nl_cursor = CLUSTER_SIZE;
 
         do {
-                list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
-                                                        shared.nonlinear) {
+                list_for_each_entry(vma,
+                        &mapping->i_mmap_nonlinear, shared.nonlinear) {
+
                         cursor = (unsigned long) vma->vm_private_data;
-                        while ( cursor < max_nl_cursor &&
+                        while (cursor < max_nl_cursor &&
                                 cursor < vma->vm_end - vma->vm_start) {
                                 if (try_to_unmap_cluster(cursor, &mapcount,
                                                 vma, page) == SWAP_MLOCK)
@@ -1585,7 +1413,7 @@ static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
                                 cursor += CLUSTER_SIZE;
                                 vma->vm_private_data = (void *) cursor;
                                 if ((int)mapcount <= 0)
-                                        goto out;
+                                        return ret;
                         }
                         vma->vm_private_data = (void *) max_nl_cursor;
                 }
@@ -1600,11 +1428,34 @@ static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
          */
         list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.nonlinear)
                 vma->vm_private_data = NULL;
-out:
-        mutex_unlock(&mapping->i_mmap_mutex);
+
         return ret;
 }
 
+bool is_vma_temporary_stack(struct vm_area_struct *vma)
+{
+        int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
+
+        if (!maybe_stack)
+                return false;
+
+        if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
+                                                VM_STACK_INCOMPLETE_SETUP)
+                return true;
+
+        return false;
+}
+
+static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
+{
+        return is_vma_temporary_stack(vma);
+}
+
+static int page_not_mapped(struct page *page)
+{
+        return !page_mapped(page);
+};
+
 /**
  * try_to_unmap - try to remove all page table mappings to a page
  * @page: the page to get unmapped
@@ -1622,16 +1473,29 @@ out:
 int try_to_unmap(struct page *page, enum ttu_flags flags)
 {
         int ret;
+        struct rmap_walk_control rwc = {
+                .rmap_one = try_to_unmap_one,
+                .arg = (void *)flags,
+                .done = page_not_mapped,
+                .file_nonlinear = try_to_unmap_nonlinear,
+                .anon_lock = page_lock_anon_vma_read,
+        };
 
-        BUG_ON(!PageLocked(page));
         VM_BUG_ON(!PageHuge(page) && PageTransHuge(page));
 
-        if (unlikely(PageKsm(page)))
-                ret = try_to_unmap_ksm(page, flags);
-        else if (PageAnon(page))
-                ret = try_to_unmap_anon(page, flags);
-        else
-                ret = try_to_unmap_file(page, flags);
+        /*
+         * During exec, a temporary VMA is setup and later moved.
+         * The VMA is moved under the anon_vma lock but not the
+         * page tables leading to a race where migration cannot
+         * find the migration ptes. Rather than increasing the
+         * locking requirements of exec(), migration skips
+         * temporary VMAs until after exec() completes.
+         */
+        if (flags & TTU_MIGRATION && !PageKsm(page) && PageAnon(page))
+                rwc.invalid_vma = invalid_migration_vma;
+
+        ret = rmap_walk(page, &rwc);
+
         if (ret != SWAP_MLOCK && !page_mapped(page))
                 ret = SWAP_SUCCESS;
         return ret;
@@ -1654,14 +1518,25 @@ int try_to_unmap(struct page *page, enum ttu_flags flags)
  */
 int try_to_munlock(struct page *page)
 {
+        int ret;
+        struct rmap_walk_control rwc = {
+                .rmap_one = try_to_unmap_one,
+                .arg = (void *)TTU_MUNLOCK,
+                .done = page_not_mapped,
+                /*
+                 * We don't bother to try to find the munlocked page in
+                 * nonlinears. It's costly. Instead, later, page reclaim logic
+                 * may call try_to_unmap() and recover PG_mlocked lazily.
+                 */
+                .file_nonlinear = NULL,
+                .anon_lock = page_lock_anon_vma_read,
+
+        };
+
         VM_BUG_ON(!PageLocked(page) || PageLRU(page));
 
-        if (unlikely(PageKsm(page)))
-                return try_to_unmap_ksm(page, TTU_MUNLOCK);
-        else if (PageAnon(page))
-                return try_to_unmap_anon(page, TTU_MUNLOCK);
-        else
-                return try_to_unmap_file(page, TTU_MUNLOCK);
+        ret = rmap_walk(page, &rwc);
+        return ret;
 }
 
 void __put_anon_vma(struct anon_vma *anon_vma)
@@ -1674,18 +1549,13 @@ void __put_anon_vma(struct anon_vma *anon_vma)
         anon_vma_free(anon_vma);
 }
 
-#ifdef CONFIG_MIGRATION
-/*
- * rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file():
- * Called by migrate.c to remove migration ptes, but might be used more later.
- */
-static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
-                struct vm_area_struct *, unsigned long, void *), void *arg)
+static struct anon_vma *rmap_walk_anon_lock(struct page *page,
+                                        struct rmap_walk_control *rwc)
 {
         struct anon_vma *anon_vma;
-        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
-        struct anon_vma_chain *avc;
-        int ret = SWAP_AGAIN;
+
+        if (rwc->anon_lock)
+                return rwc->anon_lock(page);
 
         /*
          * Note: remove_migration_ptes() cannot use page_lock_anon_vma_read()
@@ -1695,58 +1565,120 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
          */
         anon_vma = page_anon_vma(page);
         if (!anon_vma)
-                return ret;
+                return NULL;
+
         anon_vma_lock_read(anon_vma);
+        return anon_vma;
+}
+
+/*
+ * rmap_walk_anon - do something to anonymous page using the object-based
+ * rmap method
+ * @page: the page to be handled
+ * @rwc: control variable according to each walk type
+ *
+ * Find all the mappings of a page using the mapping pointer and the vma chains
+ * contained in the anon_vma struct it points to.
+ *
+ * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
+ * where the page was found will be held for write.  So, we won't recheck
+ * vm_flags for that VMA.  That should be OK, because that vma shouldn't be
+ * LOCKED.
+ */
+static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc)
+{
+        struct anon_vma *anon_vma;
+        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+        struct anon_vma_chain *avc;
+        int ret = SWAP_AGAIN;
+
+        anon_vma = rmap_walk_anon_lock(page, rwc);
+        if (!anon_vma)
+                return ret;
+
         anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
                 struct vm_area_struct *vma = avc->vma;
                 unsigned long address = vma_address(page, vma);
-                ret = rmap_one(page, vma, address, arg);
+
+                if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
+                        continue;
+
+                ret = rwc->rmap_one(page, vma, address, rwc->arg);
                 if (ret != SWAP_AGAIN)
                         break;
+                if (rwc->done && rwc->done(page))
+                        break;
         }
         anon_vma_unlock_read(anon_vma);
         return ret;
 }
 
-static int rmap_walk_file(struct page *page, int (*rmap_one)(struct page *,
-                struct vm_area_struct *, unsigned long, void *), void *arg)
+/*
+ * rmap_walk_file - do something to file page using the object-based rmap method
+ * @page: the page to be handled
+ * @rwc: control variable according to each walk type
+ *
+ * Find all the mappings of a page using the mapping pointer and the vma chains
+ * contained in the address_space struct it points to.
+ *
+ * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
+ * where the page was found will be held for write.  So, we won't recheck
+ * vm_flags for that VMA.  That should be OK, because that vma shouldn't be
+ * LOCKED.
+ */
+static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)
 {
         struct address_space *mapping = page->mapping;
-        pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+        pgoff_t pgoff = page->index << compound_order(page);
         struct vm_area_struct *vma;
         int ret = SWAP_AGAIN;
 
+        /*
+         * 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_mutex.
+         */
+        VM_BUG_ON(!PageLocked(page));
+
         if (!mapping)
                 return ret;
         mutex_lock(&mapping->i_mmap_mutex);
         vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
                 unsigned long address = vma_address(page, vma);
-                ret = rmap_one(page, vma, address, arg);
+
+                if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
+                        continue;
+
+                ret = rwc->rmap_one(page, vma, address, rwc->arg);
                 if (ret != SWAP_AGAIN)
-                        break;
+                        goto done;
+                if (rwc->done && rwc->done(page))
+                        goto done;
         }
-        /*
-         * No nonlinear handling: being always shared, nonlinear vmas
-         * never contain migration ptes.  Decide what to do about this
-         * limitation to linear when we need rmap_walk() on nonlinear.
-         */
+
+        if (!rwc->file_nonlinear)
+                goto done;
+
+        if (list_empty(&mapping->i_mmap_nonlinear))
+                goto done;
+
+        ret = rwc->file_nonlinear(page, mapping, vma);
+
+done:
         mutex_unlock(&mapping->i_mmap_mutex);
         return ret;
 }
 
-int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
-                struct vm_area_struct *, unsigned long, void *), void *arg)
+int rmap_walk(struct page *page, struct rmap_walk_control *rwc)
 {
-        VM_BUG_ON(!PageLocked(page));
-
         if (unlikely(PageKsm(page)))
-                return rmap_walk_ksm(page, rmap_one, arg);
+                return rmap_walk_ksm(page, rwc);
         else if (PageAnon(page))
-                return rmap_walk_anon(page, rmap_one, arg);
+                return rmap_walk_anon(page, rwc);
         else
-                return rmap_walk_file(page, rmap_one, arg);
+                return rmap_walk_file(page, rwc);
 }
-#endif /* CONFIG_MIGRATION */
 
 #ifdef CONFIG_HUGETLB_PAGE
 /*