| /* |
| * 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 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) |
| * |
| * (code doesn't rely on that order so it could be switched around) |
| * ->tasklist_lock |
| * anon_vma->lock (memory_failure, collect_procs_anon) |
| * pte map lock |
| */ |
| |
| #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/ksm.h> |
| #include <linux/rmap.h> |
| #include <linux/rcupdate.h> |
| #include <linux/module.h> |
| #include <linux/memcontrol.h> |
| #include <linux/mmu_notifier.h> |
| #include <linux/migrate.h> |
| |
| #include <asm/tlbflush.h> |
| |
| #include "internal.h" |
| |
| static struct kmem_cache *anon_vma_cachep; |
| static struct kmem_cache *anon_vma_chain_cachep; |
| |
| static inline struct anon_vma *anon_vma_alloc(void) |
| { |
| return kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); |
| } |
| |
| void anon_vma_free(struct anon_vma *anon_vma) |
| { |
| kmem_cache_free(anon_vma_cachep, anon_vma); |
| } |
| |
| static inline struct anon_vma_chain *anon_vma_chain_alloc(void) |
| { |
| return kmem_cache_alloc(anon_vma_chain_cachep, GFP_KERNEL); |
| } |
| |
| void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain) |
| { |
| kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain); |
| } |
| |
| /** |
| * 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; |
| struct anon_vma_chain *avc; |
| |
| might_sleep(); |
| if (unlikely(!anon_vma)) { |
| struct mm_struct *mm = vma->vm_mm; |
| struct anon_vma *allocated; |
| |
| avc = anon_vma_chain_alloc(); |
| if (!avc) |
| goto out_enomem; |
| |
| anon_vma = find_mergeable_anon_vma(vma); |
| allocated = NULL; |
| if (!anon_vma) { |
| anon_vma = anon_vma_alloc(); |
| if (unlikely(!anon_vma)) |
| goto out_enomem_free_avc; |
| allocated = anon_vma; |
| /* |
| * This VMA had no anon_vma yet. This anon_vma is |
| * the root of any anon_vma tree that might form. |
| */ |
| anon_vma->root = anon_vma; |
| } |
| |
| anon_vma_lock(anon_vma); |
| /* page_table_lock to protect against threads */ |
| spin_lock(&mm->page_table_lock); |
| if (likely(!vma->anon_vma)) { |
| vma->anon_vma = anon_vma; |
| avc->anon_vma = anon_vma; |
| avc->vma = vma; |
| list_add(&avc->same_vma, &vma->anon_vma_chain); |
| list_add(&avc->same_anon_vma, &anon_vma->head); |
| allocated = NULL; |
| avc = NULL; |
| } |
| spin_unlock(&mm->page_table_lock); |
| anon_vma_unlock(anon_vma); |
| |
| if (unlikely(allocated)) |
| anon_vma_free(allocated); |
| if (unlikely(avc)) |
| anon_vma_chain_free(avc); |
| } |
| return 0; |
| |
| out_enomem_free_avc: |
| anon_vma_chain_free(avc); |
| out_enomem: |
| return -ENOMEM; |
| } |
| |
| static void anon_vma_chain_link(struct vm_area_struct *vma, |
| struct anon_vma_chain *avc, |
| struct anon_vma *anon_vma) |
| { |
| avc->vma = vma; |
| avc->anon_vma = anon_vma; |
| list_add(&avc->same_vma, &vma->anon_vma_chain); |
| |
| anon_vma_lock(anon_vma); |
| list_add_tail(&avc->same_anon_vma, &anon_vma->head); |
| anon_vma_unlock(anon_vma); |
| } |
| |
| /* |
| * Attach the anon_vmas from src to dst. |
| * Returns 0 on success, -ENOMEM on failure. |
| */ |
| int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) |
| { |
| struct anon_vma_chain *avc, *pavc; |
| |
| list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) { |
| avc = anon_vma_chain_alloc(); |
| if (!avc) |
| goto enomem_failure; |
| anon_vma_chain_link(dst, avc, pavc->anon_vma); |
| } |
| return 0; |
| |
| enomem_failure: |
| unlink_anon_vmas(dst); |
| return -ENOMEM; |
| } |
| |
| /* |
| * Attach vma to its own anon_vma, as well as to the anon_vmas that |
| * the corresponding VMA in the parent process is attached to. |
| * Returns 0 on success, non-zero on failure. |
| */ |
| int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) |
| { |
| struct anon_vma_chain *avc; |
| struct anon_vma *anon_vma; |
| |
| /* Don't bother if the parent process has no anon_vma here. */ |
| if (!pvma->anon_vma) |
| return 0; |
| |
| /* |
| * First, attach the new VMA to the parent VMA's anon_vmas, |
| * so rmap can find non-COWed pages in child processes. |
| */ |
| if (anon_vma_clone(vma, pvma)) |
| return -ENOMEM; |
| |
| /* Then add our own anon_vma. */ |
| anon_vma = anon_vma_alloc(); |
| if (!anon_vma) |
| goto out_error; |
| avc = anon_vma_chain_alloc(); |
| if (!avc) |
| goto out_error_free_anon_vma; |
| |
| /* |
| * The root anon_vma's spinlock is the lock actually used when we |
| * lock any of the anon_vmas in this anon_vma tree. |
| */ |
| anon_vma->root = pvma->anon_vma->root; |
| /* |
| * With KSM refcounts, an anon_vma can stay around longer than the |
| * process it belongs to. The root anon_vma needs to be pinned |
| * until this anon_vma is freed, because the lock lives in the root. |
| */ |
| get_anon_vma(anon_vma->root); |
| /* Mark this anon_vma as the one where our new (COWed) pages go. */ |
| vma->anon_vma = anon_vma; |
| anon_vma_chain_link(vma, avc, anon_vma); |
| |
| return 0; |
| |
| out_error_free_anon_vma: |
| anon_vma_free(anon_vma); |
| out_error: |
| unlink_anon_vmas(vma); |
| return -ENOMEM; |
| } |
| |
| static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain) |
| { |
| struct anon_vma *anon_vma = anon_vma_chain->anon_vma; |
| int empty; |
| |
| /* If anon_vma_fork fails, we can get an empty anon_vma_chain. */ |
| if (!anon_vma) |
| return; |
| |
| anon_vma_lock(anon_vma); |
| list_del(&anon_vma_chain->same_anon_vma); |
| |
| /* We must garbage collect the anon_vma if it's empty */ |
| empty = list_empty(&anon_vma->head) && !anonvma_external_refcount(anon_vma); |
| anon_vma_unlock(anon_vma); |
| |
| if (empty) { |
| /* We no longer need the root anon_vma */ |
| if (anon_vma->root != anon_vma) |
| drop_anon_vma(anon_vma->root); |
| anon_vma_free(anon_vma); |
| } |
| } |
| |
| void unlink_anon_vmas(struct vm_area_struct *vma) |
| { |
| struct anon_vma_chain *avc, *next; |
| |
| /* |
| * Unlink each anon_vma chained to the VMA. This list is ordered |
| * from newest to oldest, ensuring the root anon_vma gets freed last. |
| */ |
| list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { |
| anon_vma_unlink(avc); |
| list_del(&avc->same_vma); |
| anon_vma_chain_free(avc); |
| } |
| } |
| |
| static void anon_vma_ctor(void *data) |
| { |
| struct anon_vma *anon_vma = data; |
| |
| spin_lock_init(&anon_vma->lock); |
| anonvma_external_refcount_init(anon_vma); |
| 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); |
| anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC); |
| } |
| |
| /* |
| * 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) ACCESS_ONCE(page->mapping); |
| if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) |
| goto out; |
| if (!page_mapped(page)) |
| goto out; |
| |
| anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); |
| anon_vma_lock(anon_vma); |
| return anon_vma; |
| out: |
| rcu_read_unlock(); |
| return NULL; |
| } |
| |
| void page_unlock_anon_vma(struct anon_vma *anon_vma) |
| { |
| anon_vma_unlock(anon_vma); |
| 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? |
| * Caller should check the page is actually part of the vma. |
| */ |
| unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) |
| { |
| if (PageAnon(page)) |
| ; |
| 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. |
| */ |
| 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. |
| */ |
| int page_referenced_one(struct page *page, struct vm_area_struct *vma, |
| unsigned long address, unsigned int *mapcount, |
| unsigned long *vm_flags) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| pte_t *pte; |
| spinlock_t *ptl; |
| int referenced = 0; |
| |
| 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 */ |
| *vm_flags |= VM_LOCKED; |
| goto out_unmap; |
| } |
| |
| if (ptep_clear_flush_young_notify(vma, address, pte)) { |
| /* |
| * Don't treat a reference through a sequentially read |
| * mapping as such. If the page has been used in |
| * another mapping, we will catch it; if this other |
| * mapping is already gone, the unmap path will have |
| * set PG_referenced or activated the page. |
| */ |
| if (likely(!VM_SequentialReadHint(vma))) |
| 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); |
| |
| if (referenced) |
| *vm_flags |= vma->vm_flags; |
| out: |
| return referenced; |
| } |
| |
| static int page_referenced_anon(struct page *page, |
| struct mem_cgroup *mem_cont, |
| unsigned long *vm_flags) |
| { |
| unsigned int mapcount; |
| struct anon_vma *anon_vma; |
| struct anon_vma_chain *avc; |
| int referenced = 0; |
| |
| anon_vma = page_lock_anon_vma(page); |
| if (!anon_vma) |
| return referenced; |
| |
| mapcount = page_mapcount(page); |
| list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { |
| struct vm_area_struct *vma = avc->vma; |
| unsigned long address = vma_address(page, vma); |
| if (address == -EFAULT) |
| continue; |
| /* |
| * 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, address, |
| &mapcount, vm_flags); |
| 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 |
| * @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 *mem_cont, |
| unsigned long *vm_flags) |
| { |
| 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) { |
| unsigned long address = vma_address(page, vma); |
| if (address == -EFAULT) |
| continue; |
| /* |
| * 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, address, |
| &mapcount, vm_flags); |
| 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 |
| * @vm_flags: collect encountered vma->vm_flags who actually referenced 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, |
| struct mem_cgroup *mem_cont, |
| unsigned long *vm_flags) |
| { |
| int referenced = 0; |
| int we_locked = 0; |
| |
| *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, mem_cont, |
| vm_flags); |
| else if (PageAnon(page)) |
| referenced += page_referenced_anon(page, mem_cont, |
| vm_flags); |
| else if (page->mapping) |
| referenced += page_referenced_file(page, mem_cont, |
| vm_flags); |
| if (we_locked) |
| unlock_page(page); |
| } |
| out: |
| if (page_test_and_clear_young(page)) |
| referenced++; |
| |
| return referenced; |
| } |
| |
| static int page_mkclean_one(struct page *page, struct vm_area_struct *vma, |
| unsigned long address) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| pte_t *pte; |
| spinlock_t *ptl; |
| int ret = 0; |
| |
| 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) { |
| unsigned long address = vma_address(page, vma); |
| if (address == -EFAULT) |
| continue; |
| ret += page_mkclean_one(page, vma, address); |
| } |
| } |
| 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_move_anon_rmap - move a page to our anon_vma |
| * @page: the page to move to our anon_vma |
| * @vma: the vma the page belongs to |
| * @address: the user virtual address mapped |
| * |
| * When a page belongs exclusively to one process after a COW event, |
| * that page can be moved into the anon_vma that belongs to just that |
| * process, so the rmap code will not search the parent or sibling |
| * processes. |
| */ |
| void page_move_anon_rmap(struct page *page, |
| struct vm_area_struct *vma, unsigned long address) |
| { |
| struct anon_vma *anon_vma = vma->anon_vma; |
| |
| VM_BUG_ON(!PageLocked(page)); |
| VM_BUG_ON(!anon_vma); |
| VM_BUG_ON(page->index != linear_page_index(vma, address)); |
| |
| anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
| page->mapping = (struct address_space *) anon_vma; |
| } |
| |
| /** |
| * __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 |
| * @exclusive: the page is exclusively owned by the current process |
| */ |
| static void __page_set_anon_rmap(struct page *page, |
| struct vm_area_struct *vma, unsigned long address, int exclusive) |
| { |
| struct anon_vma *anon_vma = vma->anon_vma; |
| |
| BUG_ON(!anon_vma); |
| |
| /* |
| * If the page isn't exclusively mapped into this vma, |
| * we must use the _oldest_ possible anon_vma for the |
| * page mapping! |
| * |
| * So take the last AVC chain entry in the vma, which is |
| * the deepest ancestor, and use the anon_vma from that. |
| */ |
| if (!exclusive) { |
| struct anon_vma_chain *avc; |
| avc = list_entry(vma->anon_vma_chain.prev, struct anon_vma_chain, same_vma); |
| anon_vma = avc->anon_vma; |
| } |
| |
| anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
| page->mapping = (struct address_space *) anon_vma; |
| page->index = linear_page_index(vma, address); |
| } |
| |
| /** |
| * __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. |
| */ |
| 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 in |
| * the anon_vma case: to serialize mapping,index checking after setting, |
| * and to ensure that PageAnon is not being upgraded racily to PageKsm |
| * (but PageKsm is never downgraded to PageAnon). |
| */ |
| void page_add_anon_rmap(struct page *page, |
| struct vm_area_struct *vma, unsigned long address) |
| { |
| int first = atomic_inc_and_test(&page->_mapcount); |
| if (first) |
| __inc_zone_page_state(page, NR_ANON_PAGES); |
| if (unlikely(PageKsm(page))) |
| return; |
| |
| VM_BUG_ON(!PageLocked(page)); |
| VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end); |
| if (first) |
| __page_set_anon_rmap(page, vma, address, 0); |
| 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) |
| { |
| VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end); |
| SetPageSwapBacked(page); |
| atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */ |
| __inc_zone_page_state(page, NR_ANON_PAGES); |
| __page_set_anon_rmap(page, vma, address, 1); |
| if (page_evictable(page, vma)) |
| lru_cache_add_lru(page, LRU_ACTIVE_ANON); |
| else |
| add_page_to_unevictable_list(page); |
| } |
| |
| /** |
| * 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); |
| mem_cgroup_update_file_mapped(page, 1); |
| } |
| } |
| |
| /** |
| * page_remove_rmap - take down pte mapping from a page |
| * @page: page to remove mapping from |
| * |
| * The caller needs to hold the pte lock. |
| */ |
| void page_remove_rmap(struct page *page) |
| { |
| /* page still mapped by someone else? */ |
| if (!atomic_add_negative(-1, &page->_mapcount)) |
| return; |
| |
| /* |
| * 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, NR_ANON_PAGES); |
| } else { |
| __dec_zone_page_state(page, NR_FILE_MAPPED); |
| mem_cgroup_update_file_mapped(page, -1); |
| } |
| /* |
| * 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. |
| */ |
| int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, |
| unsigned long address, enum ttu_flags flags) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| pte_t *pte; |
| pte_t pteval; |
| spinlock_t *ptl; |
| int ret = SWAP_AGAIN; |
| |
| 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 (!(flags & TTU_IGNORE_MLOCK)) { |
| if (vma->vm_flags & VM_LOCKED) |
| goto out_mlock; |
| |
| if (TTU_ACTION(flags) == TTU_MUNLOCK) |
| goto out_unmap; |
| } |
| if (!(flags & TTU_IGNORE_ACCESS)) { |
| 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 (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) { |
| if (PageAnon(page)) |
| dec_mm_counter(mm, MM_ANONPAGES); |
| else |
| dec_mm_counter(mm, MM_FILEPAGES); |
| set_pte_at(mm, address, pte, |
| swp_entry_to_pte(make_hwpoison_entry(page))); |
| } else 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() ... |
| */ |
| if (swap_duplicate(entry) < 0) { |
| set_pte_at(mm, address, pte, pteval); |
| ret = SWAP_FAIL; |
| goto out_unmap; |
| } |
| 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, MM_ANONPAGES); |
| inc_mm_counter(mm, MM_SWAPENTS); |
| } else if (PAGE_MIGRATION) { |
| /* |
| * 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(TTU_ACTION(flags) != TTU_MIGRATION); |
| entry = make_migration_entry(page, pte_write(pteval)); |
| } |
| set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); |
| BUG_ON(pte_file(*pte)); |
| } else if (PAGE_MIGRATION && (TTU_ACTION(flags) == TTU_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 |
| dec_mm_counter(mm, MM_FILEPAGES); |
| |
| page_remove_rmap(page); |
| page_cache_release(page); |
| |
| out_unmap: |
| pte_unmap_unlock(pte, ptl); |
| out: |
| return ret; |
| |
| out_mlock: |
| pte_unmap_unlock(pte, ptl); |
| |
| |
| /* |
| * We need mmap_sem locking, Otherwise VM_LOCKED check makes |
| * unstable result and race. Plus, We can't wait here because |
| * we now hold anon_vma->lock or mapping->i_mmap_lock. |
| * if trylock failed, the page remain in evictable lru and later |
| * vmscan could retry to move the page to unevictable lru if the |
| * page is actually mlocked. |
| */ |
| if (down_read_trylock(&vma->vm_mm->mmap_sem)) { |
| if (vma->vm_flags & VM_LOCKED) { |
| mlock_vma_page(page); |
| ret = SWAP_MLOCK; |
| } |
| up_read(&vma->vm_mm->mmap_sem); |
| } |
| 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; |
| |
| /* |
| * 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 (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); |
| page_cache_release(page); |
| dec_mm_counter(mm, MM_FILEPAGES); |
| (*mapcount)--; |
| } |
| pte_unmap_unlock(pte - 1, ptl); |
| if (locked_vma) |
| up_read(&vma->vm_mm->mmap_sem); |
| return ret; |
| } |
| |
| static 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; |
| struct anon_vma_chain *avc; |
| int ret = SWAP_AGAIN; |
| |
| anon_vma = page_lock_anon_vma(page); |
| if (!anon_vma) |
| return ret; |
| |
| list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { |
| 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 (PAGE_MIGRATION && (flags & TTU_MIGRATION) && |
| is_vma_temporary_stack(vma)) |
| continue; |
| |
| address = vma_address(page, vma); |
| if (address == -EFAULT) |
| continue; |
| ret = try_to_unmap_one(page, vma, address, flags); |
| if (ret != SWAP_AGAIN || !page_mapped(page)) |
| break; |
| } |
| |
| page_unlock_anon_vma(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) |
| { |
| 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) { |
| unsigned long address = vma_address(page, vma); |
| if (address == -EFAULT) |
| continue; |
| 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.vm_set.list) { |
| 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) { |
| cursor = (unsigned long) vma->vm_private_data; |
| while ( cursor < max_nl_cursor && |
| cursor < vma->vm_end - vma->vm_start) { |
| if (try_to_unmap_cluster(cursor, &mapcount, |
| vma, page) == SWAP_MLOCK) |
| ret = SWAP_MLOCK; |
| 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); |
| return ret; |
| } |
| |
| /** |
| * try_to_unmap - try to remove all page table mappings to a page |
| * @page: the page to get unmapped |
| * @flags: action and flags |
| * |
| * 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, enum ttu_flags flags) |
| { |
| int ret; |
| |
| BUG_ON(!PageLocked(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); |
| if (ret != SWAP_MLOCK && !page_mapped(page)) |
| ret = SWAP_SUCCESS; |
| return ret; |
| } |
| |
| /** |
| * 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_AGAIN - no vma is holding page mlocked, or, |
| * SWAP_AGAIN - page mapped in mlocked vma -- couldn't acquire mmap sem |
| * SWAP_FAIL - page cannot be located at present |
| * SWAP_MLOCK - page is now mlocked. |
| */ |
| int try_to_munlock(struct page *page) |
| { |
| 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); |
| } |
| |
| #if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION) |
| /* |
| * Drop an anon_vma refcount, freeing the anon_vma and anon_vma->root |
| * if necessary. Be careful to do all the tests under the lock. Once |
| * we know we are the last user, nobody else can get a reference and we |
| * can do the freeing without the lock. |
| */ |
| void drop_anon_vma(struct anon_vma *anon_vma) |
| { |
| if (atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->root->lock)) { |
| struct anon_vma *root = anon_vma->root; |
| int empty = list_empty(&anon_vma->head); |
| int last_root_user = 0; |
| int root_empty = 0; |
| |
| /* |
| * The refcount on a non-root anon_vma got dropped. Drop |
| * the refcount on the root and check if we need to free it. |
| */ |
| if (empty && anon_vma != root) { |
| last_root_user = atomic_dec_and_test(&root->external_refcount); |
| root_empty = list_empty(&root->head); |
| } |
| anon_vma_unlock(anon_vma); |
| |
| if (empty) { |
| anon_vma_free(anon_vma); |
| if (root_empty && last_root_user) |
| anon_vma_free(root); |
| } |
| } |
| } |
| #endif |
| |
| #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) |
| { |
| struct anon_vma *anon_vma; |
| struct anon_vma_chain *avc; |
| int ret = SWAP_AGAIN; |
| |
| /* |
| * Note: remove_migration_ptes() cannot use page_lock_anon_vma() |
| * because that depends on page_mapped(); but not all its usages |
| * are holding mmap_sem. Users without mmap_sem are required to |
| * take a reference count to prevent the anon_vma disappearing |
| */ |
| anon_vma = page_anon_vma(page); |
| if (!anon_vma) |
| return ret; |
| anon_vma_lock(anon_vma); |
| list_for_each_entry(avc, &anon_vma->head, same_anon_vma) { |
| struct vm_area_struct *vma = avc->vma; |
| unsigned long address = vma_address(page, vma); |
| if (address == -EFAULT) |
| continue; |
| ret = rmap_one(page, vma, address, arg); |
| if (ret != SWAP_AGAIN) |
| break; |
| } |
| anon_vma_unlock(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) |
| { |
| 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; |
| |
| if (!mapping) |
| return ret; |
| spin_lock(&mapping->i_mmap_lock); |
| vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) { |
| unsigned long address = vma_address(page, vma); |
| if (address == -EFAULT) |
| continue; |
| ret = rmap_one(page, vma, address, arg); |
| if (ret != SWAP_AGAIN) |
| break; |
| } |
| /* |
| * 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. |
| */ |
| spin_unlock(&mapping->i_mmap_lock); |
| return ret; |
| } |
| |
| int rmap_walk(struct page *page, int (*rmap_one)(struct page *, |
| struct vm_area_struct *, unsigned long, void *), void *arg) |
| { |
| VM_BUG_ON(!PageLocked(page)); |
| |
| if (unlikely(PageKsm(page))) |
| return rmap_walk_ksm(page, rmap_one, arg); |
| else if (PageAnon(page)) |
| return rmap_walk_anon(page, rmap_one, arg); |
| else |
| return rmap_walk_file(page, rmap_one, arg); |
| } |
| #endif /* CONFIG_MIGRATION */ |