diff options
Diffstat (limited to 'mm/rmap.c')
| -rw-r--r-- | mm/rmap.c | 1236 |
1 files changed, 1236 insertions, 0 deletions
diff --git a/mm/rmap.c b/mm/rmap.c new file mode 100644 index 0000000..1099394 --- /dev/null +++ b/mm/rmap.c @@ -0,0 +1,1236 @@ +/* + * 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_mutex (while writing or truncating, not reading or faulting) + * inode->i_alloc_sem (vmtruncate_range) + * mm->mmap_sem + * page->flags PG_locked (lock_page) + * mapping->i_mmap_lock + * anon_vma->lock + * mm->page_table_lock or pte_lock + * zone->lru_lock (in mark_page_accessed, isolate_lru_page) + * swap_lock (in swap_duplicate, swap_info_get) + * mmlist_lock (in mmput, drain_mmlist and others) + * 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 <linux/module.h> +#include <linux/kallsyms.h> +#include <linux/memcontrol.h> +#include <linux/mmu_notifier.h> + +#include <asm/tlbflush.h> + +#include "internal.h" + +static struct kmem_cache *anon_vma_cachep; + +static inline struct anon_vma *anon_vma_alloc(void) +{ + return kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); +} + +static inline void anon_vma_free(struct anon_vma *anon_vma) +{ + kmem_cache_free(anon_vma_cachep, anon_vma); +} + +/** + * anon_vma_prepare - attach an anon_vma to a memory region + * @vma: the memory region in question + * + * This makes sure the memory mapping described by 'vma' has + * an 'anon_vma' attached to it, so that we can associate the + * anonymous pages mapped into it with that anon_vma. + * + * The common case will be that we already have one, but if + * if not we either need to find an adjacent mapping that we + * can re-use the anon_vma from (very common when the only + * reason for splitting a vma has been mprotect()), or we + * allocate a new one. + * + * Anon-vma allocations are very subtle, because we may have + * optimistically looked up an anon_vma in page_lock_anon_vma() + * and that may actually touch the spinlock even in the newly + * allocated vma (it depends on RCU to make sure that the + * anon_vma isn't actually destroyed). + * + * As a result, we need to do proper anon_vma locking even + * for the new allocation. At the same time, we do not want + * to do any locking for the common case of already having + * an anon_vma. + * + * This must be called with the mmap_sem held for reading. + */ +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; + + anon_vma = find_mergeable_anon_vma(vma); + allocated = NULL; + if (!anon_vma) { + anon_vma = anon_vma_alloc(); + if (unlikely(!anon_vma)) + return -ENOMEM; + allocated = anon_vma; + } + spin_lock(&anon_vma->lock); + + /* 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_tail(&vma->anon_vma_node, &anon_vma->head); + allocated = NULL; + } + spin_unlock(&mm->page_table_lock); + + spin_unlock(&anon_vma->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_tail(&vma->anon_vma_node, &anon_vma->head); +} + +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_tail(&vma->anon_vma_node, &anon_vma->head); + 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); + 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) +{ + 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); +} + +/* + * 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. + */ +struct anon_vma *page_lock_anon_vma(struct page *page) +{ + struct anon_vma *anon_vma; + 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); + return anon_vma; +out: + rcu_read_unlock(); + return NULL; +} + +void page_unlock_anon_vma(struct anon_vma *anon_vma) +{ + spin_unlock(&anon_vma->lock); + rcu_read_unlock(); +} + +/* + * At what user virtual address is page expected in @vma? + * Returns virtual address or -EFAULT if page's index/offset is not + * within the range mapped the @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 @vma mapping range */ + return -EFAULT; + } + return address; +} + +/* + * At what user virtual address is page expected in vma? checking that the + * page matches the vma: currently only used on anon pages, by unuse_vma; + */ +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 || + vma->vm_file->f_mapping != page->mapping) + return -EFAULT; + } else + return -EFAULT; + return vma_address(page, vma); +} + +/* + * Check that @page is mapped at @address into @mm. + * + * If @sync is false, page_check_address may perform a racy check to avoid + * the page table lock when the pte is not present (helpful when reclaiming + * highly shared pages). + * + * On success returns with pte mapped and locked. + */ +pte_t *page_check_address(struct page *page, struct mm_struct *mm, + unsigned long address, spinlock_t **ptlp, int sync) +{ + pgd_t *pgd; + pud_t *pud; + pmd_t *pmd; + pte_t *pte; + spinlock_t *ptl; + + pgd = pgd_offset(mm, address); + if (!pgd_present(*pgd)) + return NULL; + + pud = pud_offset(pgd, address); + if (!pud_present(*pud)) + return NULL; + + pmd = pmd_offset(pud, address); + if (!pmd_present(*pmd)) + return NULL; + + pte = pte_offset_map(pmd, address); + /* Make a quick check before getting the lock */ + if (!sync && !pte_present(*pte)) { + pte_unmap(pte); + return NULL; + } + + ptl = pte_lockptr(mm, pmd); + spin_lock(ptl); + if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) { + *ptlp = ptl; + return pte; + } + pte_unmap_unlock(pte, ptl); + return NULL; +} + +/** + * page_mapped_in_vma - check whether a page is really mapped in a VMA + * @page: the page to test + * @vma: the VMA to test + * + * Returns 1 if the page is mapped into the page tables of the VMA, 0 + * if the page is not mapped into the page tables of this VMA. Only + * valid for normal file or anonymous VMAs. + */ +static int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma) +{ + unsigned long address; + pte_t *pte; + spinlock_t *ptl; + + address = vma_address(page, vma); + if (address == -EFAULT) /* out of vma range */ + return 0; + pte = page_check_address(page, vma->vm_mm, address, &ptl, 1); + if (!pte) /* the page is not in this mm */ + return 0; + pte_unmap_unlock(pte, ptl); + + return 1; +} + +/* + * 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) +{ + struct mm_struct *mm = vma->vm_mm; + unsigned long address; + pte_t *pte; + spinlock_t *ptl; + int referenced = 0; + + address = vma_address(page, vma); + if (address == -EFAULT) + goto out; + + pte = page_check_address(page, mm, address, &ptl, 0); + if (!pte) + goto out; + + /* + * Don't want to elevate referenced for mlocked page that gets this far, + * in order that it progresses to try_to_unmap and is moved to the + * unevictable list. + */ + if (vma->vm_flags & VM_LOCKED) { + *mapcount = 1; /* break early from loop */ + goto out_unmap; + } + + if (ptep_clear_flush_young_notify(vma, address, pte)) + referenced++; + + /* Pretend the page is referenced if the task has the + swap token and is in the middle of a page fault. */ + if (mm != current->mm && has_swap_token(mm) && + rwsem_is_locked(&mm->mmap_sem)) + referenced++; + +out_unmap: + (*mapcount)--; + pte_unmap_unlock(pte, ptl); +out: + return referenced; +} + +static int page_referenced_anon(struct page *page, + struct mem_cgroup *mem_cont) +{ + 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) { + /* + * If we are reclaiming on behalf of a cgroup, skip + * counting on behalf of references from different + * cgroups + */ + if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont)) + continue; + referenced += page_referenced_one(page, vma, &mapcount); + if (!mapcount) + break; + } + + page_unlock_anon_vma(anon_vma); + return referenced; +} + +/** + * page_referenced_file - referenced check for object-based rmap + * @page: the page we're checking references on. + * @mem_cont: target memory controller + * + * 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 *mem_cont) +{ + 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 we are reclaiming on behalf of a cgroup, skip + * counting on behalf of references from different + * cgroups + */ + if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont)) + continue; + referenced += page_referenced_one(page, vma, &mapcount); + 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 + * @mem_cont: target memory controller + * + * 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, + struct mem_cgroup *mem_cont) +{ + int referenced = 0; + + if (TestClearPageReferenced(page)) + referenced++; + + if (page_mapped(page) && page->mapping) { + if (PageAnon(page)) + referenced += page_referenced_anon(page, mem_cont); + else if (is_locked) + referenced += page_referenced_file(page, mem_cont); + else if (!trylock_page(page)) + referenced++; + else { + if (page->mapping) + referenced += + page_referenced_file(page, mem_cont); + unlock_page(page); + } + } + + if (page_test_and_clear_young(page)) + referenced++; + + return referenced; +} + +static int page_mkclean_one(struct page *page, struct vm_area_struct *vma) +{ + struct mm_struct *mm = vma->vm_mm; + unsigned long address; + pte_t *pte; + spinlock_t *ptl; + int ret = 0; + + address = vma_address(page, vma); + if (address == -EFAULT) + goto out; + + pte = page_check_address(page, mm, address, &ptl, 1); + if (!pte) + goto out; + + if (pte_dirty(*pte) || pte_write(*pte)) { + pte_t entry; + + flush_cache_page(vma, address, pte_pfn(*pte)); + entry = ptep_clear_flush_notify(vma, address, pte); + entry = pte_wrprotect(entry); + entry = pte_mkclean(entry); + set_pte_at(mm, address, pte, entry); + ret = 1; + } + + pte_unmap_unlock(pte, ptl); +out: + return ret; +} + +static int page_mkclean_file(struct address_space *mapping, struct page *page) +{ + pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT); + struct vm_area_struct *vma; + struct prio_tree_iter iter; + int ret = 0; + + BUG_ON(PageAnon(page)); + + spin_lock(&mapping->i_mmap_lock); + vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { + if (vma->vm_flags & VM_SHARED) + ret += page_mkclean_one(page, vma); + } + spin_unlock(&mapping->i_mmap_lock); + return ret; +} + +int page_mkclean(struct page *page) +{ + int ret = 0; + + 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_test_dirty(page)) { + page_clear_dirty(page); + ret = 1; + } + } + } + + return ret; +} +EXPORT_SYMBOL_GPL(page_mkclean); + +/** + * __page_set_anon_rmap - setup new anonymous rmap + * @page: the page to add the mapping to + * @vma: the vm area in which the mapping is added + * @address: the user virtual address mapped + */ +static void __page_set_anon_rmap(struct page *page, + struct vm_area_struct *vma, unsigned long address) +{ + struct anon_vma *anon_vma = vma->anon_vma; + + BUG_ON(!anon_vma); + anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; + page->mapping = (struct address_space *) anon_vma; + + page->index = linear_page_index(vma, address); + + /* + * nr_mapped state can be updated without turning off + * interrupts because it is not modified via interrupt. + */ + __inc_zone_page_state(page, NR_ANON_PAGES); +} + +/** + * __page_check_anon_rmap - sanity check anonymous rmap addition + * @page: the page to add the mapping to + * @vma: the vm area in which the mapping is added + * @address: the user virtual address mapped + */ +static void __page_check_anon_rmap(struct page *page, + struct vm_area_struct *vma, unsigned long address) +{ +#ifdef CONFIG_DEBUG_VM + /* + * The page's anon-rmap details (mapping and index) are guaranteed to + * be set up correctly at this point. + * + * We have exclusion against page_add_anon_rmap because the caller + * always holds the page locked, except if called from page_dup_rmap, + * in which case the page is already known to be setup. + * + * We have exclusion against page_add_new_anon_rmap because those pages + * are initially only visible via the pagetables, and the pte is locked + * over the call to page_add_new_anon_rmap. + */ + struct anon_vma *anon_vma = vma->anon_vma; + anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; + BUG_ON(page->mapping != (struct address_space *)anon_vma); + BUG_ON(page->index != linear_page_index(vma, address)); +#endif +} + +/** + * 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 pte lock and the page must be locked. + */ +void page_add_anon_rmap(struct page *page, + struct vm_area_struct *vma, unsigned long address) +{ + VM_BUG_ON(!PageLocked(page)); + VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end); + if (atomic_inc_and_test(&page->_mapcount)) + __page_set_anon_rmap(page, vma, address); + else + __page_check_anon_rmap(page, vma, address); +} + +/** + * page_add_new_anon_rmap - add pte mapping to a new 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 + * + * Same as page_add_anon_rmap but must only be called on *new* pages. + * This means the inc-and-test can be bypassed. + * Page does not have to be locked. + */ +void page_add_new_anon_rmap(struct page *page, + struct vm_area_struct *vma, unsigned long address) +{ + BUG_ON(address < vma->vm_start || address >= vma->vm_end); + atomic_set(&page->_mapcount, 0); /* elevate count by 1 (starts at -1) */ + __page_set_anon_rmap(page, vma, address); +} + +/** + * 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 pte lock. + */ +void page_add_file_rmap(struct page *page) +{ + if (atomic_inc_and_test(&page->_mapcount)) + __inc_zone_page_state(page, NR_FILE_MAPPED); +} + +#ifdef CONFIG_DEBUG_VM +/** + * page_dup_rmap - duplicate pte mapping to a page + * @page: the page to add the mapping to + * @vma: the vm area being duplicated + * @address: the user virtual address mapped + * + * For copy_page_range only: minimal extract from page_add_file_rmap / + * page_add_anon_rmap, avoiding unnecessary tests (already checked) so it's + * quicker. + * + * The caller needs to hold the pte lock. + */ +void page_dup_rmap(struct page *page, struct vm_area_struct *vma, unsigned long address) +{ + BUG_ON(page_mapcount(page) == 0); + if (PageAnon(page)) + __page_check_anon_rmap(page, vma, address); + atomic_inc(&page->_mapcount); +} +#endif + +/** + * page_remove_rmap - take down pte mapping from a page + * @page: page to remove mapping from + * @vma: the vm area in which the mapping is removed + * + * The caller needs to hold the pte lock. + */ +void page_remove_rmap(struct page *page, struct vm_area_struct *vma) +{ + if (atomic_add_negative(-1, &page->_mapcount)) { + if (unlikely(page_mapcount(page) < 0)) { + printk (KERN_EMERG "Eeek! page_mapcount(page) went negative! (%d)\n", page_mapcount(page)); + printk (KERN_EMERG " page pfn = %lx\n", page_to_pfn(page)); + printk (KERN_EMERG " page->flags = %lx\n", page->flags); + printk (KERN_EMERG " page->count = %x\n", page_count(page)); + printk (KERN_EMERG " page->mapping = %p\n", page->mapping); + print_symbol (KERN_EMERG " vma->vm_ops = %s\n", (unsigned long)vma->vm_ops); + if (vma->vm_ops) { + print_symbol (KERN_EMERG " vma->vm_ops->fault = %s\n", (unsigned long)vma->vm_ops->fault); + } + if (vma->vm_file && vma->vm_file->f_op) + print_symbol (KERN_EMERG " vma->vm_file->f_op->mmap = %s\n", (unsigned long)vma->vm_file->f_op->mmap); + BUG(); + } + + /* + * Now that the last pte has gone, s390 must transfer dirty + * flag from storage key to struct page. We can usually skip + * this if the page is anon, so about to be freed; but perhaps + * not if it's in swapcache - there might be another pte slot + * containing the swap entry, but page not yet written to swap. + */ + if ((!PageAnon(page) || PageSwapCache(page)) && + page_test_dirty(page)) { + page_clear_dirty(page); + set_page_dirty(page); + } + if (PageAnon(page)) + mem_cgroup_uncharge_page(page); + __dec_zone_page_state(page, + PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED); + /* + * 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. + */ + } +} + +/* + * 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, + int migration) +{ + struct mm_struct *mm = vma->vm_mm; + unsigned long address; + pte_t *pte; + pte_t pteval; + spinlock_t *ptl; + int ret = SWAP_AGAIN; + + address = vma_address(page, vma); + if (address == -EFAULT) + goto out; + + pte = page_check_address(page, mm, address, &ptl, 0); + if (!pte) + goto out; + + /* + * 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 (!migration) { + if (vma->vm_flags & VM_LOCKED) { + ret = SWAP_MLOCK; + goto out_unmap; + } + if (ptep_clear_flush_young_notify(vma, address, pte)) { + ret = SWAP_FAIL; + goto out_unmap; + } + } + + /* Nuke the page table entry. */ + flush_cache_page(vma, address, page_to_pfn(page)); + pteval = ptep_clear_flush_notify(vma, address, pte); + + /* Move the dirty bit to the physical page now the pte is gone. */ + if (pte_dirty(pteval)) + set_page_dirty(page); + + /* Update high watermark before we lower rss */ + update_hiwater_rss(mm); + + if (PageAnon(page)) { + swp_entry_t entry = { .val = page_private(page) }; + + if (PageSwapCache(page)) { + /* + * Store the swap location in the pte. + * See handle_pte_fault() ... + */ + swap_duplicate(entry); + if (list_empty(&mm->mmlist)) { + spin_lock(&mmlist_lock); + if (list_empty(&mm->mmlist)) + list_add(&mm->mmlist, &init_mm.mmlist); + spin_unlock(&mmlist_lock); + } + dec_mm_counter(mm, anon_rss); +#ifdef CONFIG_MIGRATION + } else { + /* + * Store the pfn of the page in a special migration + * pte. do_swap_page() will wait until the migration + * pte is removed and then restart fault handling. + */ + BUG_ON(!migration); + entry = make_migration_entry(page, pte_write(pteval)); +#endif + } + set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); + BUG_ON(pte_file(*pte)); + } else +#ifdef CONFIG_MIGRATION + if (migration) { + /* Establish migration entry for a file page */ + swp_entry_t entry; + entry = make_migration_entry(page, pte_write(pteval)); + set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); + } else +#endif + dec_mm_counter(mm, file_rss); + + + page_remove_rmap(page, vma); + page_cache_release(page); + +out_unmap: + pte_unmap_unlock(pte, ptl); +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. + * + * Mlocked pages: check VM_LOCKED under mmap_sem held for read, if we can + * acquire it without blocking. If vma locked, mlock the pages in the cluster, + * rather than unmapping them. If we encounter the "check_page" that vmscan is + * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN. + */ +#define CLUSTER_SIZE min(32*PAGE_SIZE, PMD_SIZE) +#define CLUSTER_MASK (~(CLUSTER_SIZE - 1)) + +static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount, + struct vm_area_struct *vma, struct page *check_page) +{ + struct mm_struct *mm = vma->vm_mm; + pgd_t *pgd; + pud_t *pud; + pmd_t *pmd; + pte_t *pte; + pte_t pteval; + spinlock_t *ptl; + struct page *page; + unsigned long address; + unsigned long end; + int ret = SWAP_AGAIN; + int locked_vma = 0; + + 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)) + return ret; + + pud = pud_offset(pgd, address); + if (!pud_present(*pud)) + return ret; + + pmd = pmd_offset(pud, address); + if (!pmd_present(*pmd)) + return ret; + + /* + * MLOCK_PAGES => feature is configured. + * if we can acquire the mmap_sem for read, and vma is VM_LOCKED, + * keep the sem while scanning the cluster for mlocking pages. + */ + if (MLOCK_PAGES && down_read_trylock(&vma->vm_mm->mmap_sem)) { + locked_vma = (vma->vm_flags & VM_LOCKED); + if (!locked_vma) + up_read(&vma->vm_mm->mmap_sem); /* don't need it */ + } + + pte = pte_offset_map_lock(mm, pmd, address, &ptl); + + /* Update high watermark before we lower rss */ + update_hiwater_rss(mm); + + for (; address < end; pte++, address += PAGE_SIZE) { + if (!pte_present(*pte)) + continue; + page = vm_normal_page(vma, address, *pte); + BUG_ON(!page || PageAnon(page)); + + if (locked_vma) { + mlock_vma_page(page); /* no-op if already mlocked */ + if (page == check_page) + ret = SWAP_MLOCK; + continue; /* don't unmap */ + } + + if (ptep_clear_flush_young_notify(vma, address, pte)) + continue; + + /* Nuke the page table entry. */ + flush_cache_page(vma, address, pte_pfn(*pte)); + pteval = ptep_clear_flush_notify(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, vma); + page_cache_release(page); + dec_mm_counter(mm, file_rss); + (*mapcount)--; + } + pte_unmap_unlock(pte - 1, ptl); + if (locked_vma) + up_read(&vma->vm_mm->mmap_sem); + return ret; +} + +/* + * common handling for pages mapped in VM_LOCKED vmas + */ +static int try_to_mlock_page(struct page *page, struct vm_area_struct *vma) +{ + int mlocked = 0; + + if (down_read_trylock(&vma->vm_mm->mmap_sem)) { + if (vma->vm_flags & VM_LOCKED) { + mlock_vma_page(page); + mlocked++; /* really mlocked the page */ + } + up_read(&vma->vm_mm->mmap_sem); + } + return mlocked; +} + +/** + * try_to_unmap_anon - unmap or unlock anonymous page using the object-based + * rmap method + * @page: the page to unmap/unlock + * @unlock: request for unlock rather than unmap [unlikely] + * @migration: unmapping for migration - ignored if @unlock + * + * 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, int unlock, int migration) +{ + struct anon_vma *anon_vma; + struct vm_area_struct *vma; + unsigned int mlocked = 0; + int ret = SWAP_AGAIN; + + if (MLOCK_PAGES && unlikely(unlock)) + ret = SWAP_SUCCESS; /* default for try_to_munlock() */ + + anon_vma = page_lock_anon_vma(page); + if (!anon_vma) + return ret; + + list_for_each_entry(vma, &anon_vma->head, anon_vma_node) { + if (MLOCK_PAGES && unlikely(unlock)) { + if (!((vma->vm_flags & VM_LOCKED) && + page_mapped_in_vma(page, vma))) + continue; /* must visit all unlocked vmas */ + ret = SWAP_MLOCK; /* saw at least one mlocked vma */ + } else { + ret = try_to_unmap_one(page, vma, migration); + if (ret == SWAP_FAIL || !page_mapped(page)) + break; + } + if (ret == SWAP_MLOCK) { + mlocked = try_to_mlock_page(page, vma); + if (mlocked) + break; /* stop if actually mlocked page */ + } + } + + page_unlock_anon_vma(anon_vma); + + if (mlocked) + ret = SWAP_MLOCK; /* actually mlocked the page */ + else if (ret == SWAP_MLOCK) + ret = SWAP_AGAIN; /* saw VM_LOCKED vma */ + + return ret; +} + +/** + * try_to_unmap_file - unmap/unlock file page using the object-based rmap method + * @page: the page to unmap/unlock + * @unlock: request for unlock rather than unmap [unlikely] + * @migration: unmapping for migration - ignored if @unlock + * + * 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, int unlock, int migration) +{ + 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; + unsigned int mlocked = 0; + + if (MLOCK_PAGES && unlikely(unlock)) + ret = SWAP_SUCCESS; /* default for try_to_munlock() */ + + spin_lock(&mapping->i_mmap_lock); + vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { + if (MLOCK_PAGES && unlikely(unlock)) { + if (!(vma->vm_flags & VM_LOCKED)) + continue; /* must visit all vmas */ + ret = SWAP_MLOCK; + } else { + ret = try_to_unmap_one(page, vma, migration); + if (ret == SWAP_FAIL || !page_mapped(page)) + goto out; + } + if (ret == SWAP_MLOCK) { + mlocked = try_to_mlock_page(page, vma); + if (mlocked) + break; /* stop if actually mlocked page */ + } + } + + if (mlocked) + 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 (MLOCK_PAGES && unlikely(unlock)) { + if (!(vma->vm_flags & VM_LOCKED)) + continue; /* must visit all vmas */ + ret = SWAP_MLOCK; /* leave mlocked == 0 */ + goto out; /* no need to look further */ + } + if (!MLOCK_PAGES && !migration && (vma->vm_flags & VM_LOCKED)) + 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) { /* all 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 (!MLOCK_PAGES && !migration && + (vma->vm_flags & VM_LOCKED)) + continue; + cursor = (unsigned long) vma->vm_private_data; + while ( cursor < max_nl_cursor && + cursor < vma->vm_end - vma->vm_start) { + ret = try_to_unmap_cluster(cursor, &mapcount, + vma, page); + if (ret == SWAP_MLOCK) + mlocked = 2; /* to return below */ + 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) + vma->vm_private_data = NULL; +out: + spin_unlock(&mapping->i_mmap_lock); + if (mlocked) + ret = SWAP_MLOCK; /* actually mlocked the page */ + else if (ret == SWAP_MLOCK) + ret = SWAP_AGAIN; /* saw VM_LOCKED vma */ + return ret; +} + +/** + * try_to_unmap - try to remove all page table mappings to a page + * @page: the page to get unmapped + * @migration: migration flag + * + * 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 + * SWAP_MLOCK - page is mlocked. + */ +int try_to_unmap(struct page *page, int migration) +{ + int ret; + + BUG_ON(!PageLocked(page)); + + if (PageAnon(page)) + ret = try_to_unmap_anon(page, 0, migration); + else + ret = try_to_unmap_file(page, 0, migration); + if (ret != SWAP_MLOCK && !page_mapped(page)) + ret = SWAP_SUCCESS; + return ret; +} + +#ifdef CONFIG_UNEVICTABLE_LRU +/** + * try_to_munlock - try to munlock a page + * @page: the page to be munlocked + * + * Called from munlock code. Checks all of the VMAs mapping the page + * to make sure nobody else has this page mlocked. The page will be + * returned with PG_mlocked cleared if no other vmas have it mlocked. + * + * Return values are: + * + * SWAP_SUCCESS - no vma's holding page mlocked. + * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem + * SWAP_MLOCK - page is now mlocked. + */ +int try_to_munlock(struct page *page) +{ + VM_BUG_ON(!PageLocked(page) || PageLRU(page)); + + if (PageAnon(page)) + return try_to_unmap_anon(page, 1, 0); + else + return try_to_unmap_file(page, 1, 0); +} +#endif |
