From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sat, 16 Apr 2005 15:20:36 -0700 Subject: Linux-2.6.12-rc2 Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip! --- mm/rmap.c | 862 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 862 insertions(+) create mode 100644 mm/rmap.c (limited to 'mm/rmap.c') diff --git a/mm/rmap.c b/mm/rmap.c new file mode 100644 index 00000000000..884d6d1928b --- /dev/null +++ b/mm/rmap.c @@ -0,0 +1,862 @@ +/* + * mm/rmap.c - physical to virtual reverse mappings + * + * Copyright 2001, Rik van Riel + * 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 2001 + * File methods by Dave McCracken 2003, 2004 + * Anonymous methods by Andrea Arcangeli 2004 + * Contributions by Hugh Dickins 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 +#include +#include +#include +#include +#include +#include +#include + +#include + +//#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; +} -- cgit v1.2.3