diff options
Diffstat (limited to 'mm/rmap.c')
| -rw-r--r-- | mm/rmap.c | 1776 |
1 files changed, 1776 insertions, 0 deletions
diff --git a/mm/rmap.c b/mm/rmap.c new file mode 100644 index 00000000..23295f65 --- /dev/null +++ b/mm/rmap.c @@ -0,0 +1,1776 @@ +/* + * 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_mutex + * anon_vma->mutex + * 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->i_lock (in set_page_dirty's __mark_inode_dirty) + * inode_wb_list_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_wb_list_lock in __sync_single_inode) + * + * anon_vma->mutex,mapping->i_mutex (memory_failure, collect_procs_anon) + * ->tasklist_lock + * 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 <linux/hugetlb.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) +{ + struct anon_vma *anon_vma; + + anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); + if (anon_vma) { + atomic_set(&anon_vma->refcount, 1); + /* + * Initialise the anon_vma root to point to itself. If called + * from fork, the root will be reset to the parents anon_vma. + */ + anon_vma->root = anon_vma; + } + + return anon_vma; +} + +static inline void anon_vma_free(struct anon_vma *anon_vma) +{ + VM_BUG_ON(atomic_read(&anon_vma->refcount)); + + /* + * Synchronize against page_lock_anon_vma() such that + * we can safely hold the lock without the anon_vma getting + * freed. + * + * Relies on the full mb implied by the atomic_dec_and_test() from + * put_anon_vma() against the acquire barrier implied by + * mutex_trylock() from page_lock_anon_vma(). This orders: + * + * page_lock_anon_vma() VS put_anon_vma() + * mutex_trylock() atomic_dec_and_test() + * LOCK MB + * atomic_read() mutex_is_locked() + * + * LOCK should suffice since the actual taking of the lock must + * happen _before_ what follows. + */ + if (mutex_is_locked(&anon_vma->root->mutex)) { + anon_vma_lock(anon_vma); + anon_vma_unlock(anon_vma); + } + + kmem_cache_free(anon_vma_cachep, anon_vma); +} + +static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp) +{ + return kmem_cache_alloc(anon_vma_chain_cachep, gfp); +} + +static 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 + * 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(GFP_KERNEL); + 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; + } + + 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_tail(&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)) + put_anon_vma(allocated); + if (unlikely(avc)) + anon_vma_chain_free(avc); + } + return 0; + + out_enomem_free_avc: + anon_vma_chain_free(avc); + out_enomem: + return -ENOMEM; +} + +/* + * This is a useful helper function for locking the anon_vma root as + * we traverse the vma->anon_vma_chain, looping over anon_vma's that + * have the same vma. + * + * Such anon_vma's should have the same root, so you'd expect to see + * just a single mutex_lock for the whole traversal. + */ +static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma) +{ + struct anon_vma *new_root = anon_vma->root; + if (new_root != root) { + if (WARN_ON_ONCE(root)) + mutex_unlock(&root->mutex); + root = new_root; + mutex_lock(&root->mutex); + } + return root; +} + +static inline void unlock_anon_vma_root(struct anon_vma *root) +{ + if (root) + mutex_unlock(&root->mutex); +} + +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); + + /* + * It's critical to add new vmas to the tail of the anon_vma, + * see comment in huge_memory.c:__split_huge_page(). + */ + list_add_tail(&avc->same_anon_vma, &anon_vma->head); +} + +/* + * 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; + struct anon_vma *root = NULL; + + list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) { + struct anon_vma *anon_vma; + + avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN); + if (unlikely(!avc)) { + unlock_anon_vma_root(root); + root = NULL; + avc = anon_vma_chain_alloc(GFP_KERNEL); + if (!avc) + goto enomem_failure; + } + anon_vma = pavc->anon_vma; + root = lock_anon_vma_root(root, anon_vma); + anon_vma_chain_link(dst, avc, anon_vma); + } + unlock_anon_vma_root(root); + 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(GFP_KERNEL); + 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 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_lock(anon_vma); + anon_vma_chain_link(vma, avc, anon_vma); + anon_vma_unlock(anon_vma); + + return 0; + + out_error_free_anon_vma: + put_anon_vma(anon_vma); + out_error: + unlink_anon_vmas(vma); + return -ENOMEM; +} + +void unlink_anon_vmas(struct vm_area_struct *vma) +{ + struct anon_vma_chain *avc, *next; + struct anon_vma *root = NULL; + + /* + * 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) { + struct anon_vma *anon_vma = avc->anon_vma; + + root = lock_anon_vma_root(root, anon_vma); + list_del(&avc->same_anon_vma); + + /* + * Leave empty anon_vmas on the list - we'll need + * to free them outside the lock. + */ + if (list_empty(&anon_vma->head)) + continue; + + list_del(&avc->same_vma); + anon_vma_chain_free(avc); + } + unlock_anon_vma_root(root); + + /* + * Iterate the list once more, it now only contains empty and unlinked + * anon_vmas, destroy them. Could not do before due to __put_anon_vma() + * needing to acquire the anon_vma->root->mutex. + */ + list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { + struct anon_vma *anon_vma = avc->anon_vma; + + put_anon_vma(anon_vma); + + list_del(&avc->same_vma); + anon_vma_chain_free(avc); + } +} + +static void anon_vma_ctor(void *data) +{ + struct anon_vma *anon_vma = data; + + mutex_init(&anon_vma->mutex); + atomic_set(&anon_vma->refcount, 0); + 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! + * + * Since there is no serialization what so ever against page_remove_rmap() + * the best this function can do is return a locked anon_vma that might + * have been relevant to this page. + * + * The page might have been remapped to a different anon_vma or the anon_vma + * returned may already be freed (and even reused). + * + * In case it was remapped to a different anon_vma, the new anon_vma will be a + * child of the old anon_vma, and the anon_vma lifetime rules will therefore + * ensure that any anon_vma obtained from the page will still be valid for as + * long as we observe page_mapped() [ hence all those page_mapped() tests ]. + * + * All users of this function must be very careful when walking the anon_vma + * chain and verify that the page in question is indeed mapped in it + * [ something equivalent to page_mapped_in_vma() ]. + * + * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap() + * that the anon_vma pointer from page->mapping is valid if there is a + * mapcount, we can dereference the anon_vma after observing those. + */ +struct anon_vma *page_get_anon_vma(struct page *page) +{ + struct anon_vma *anon_vma = NULL; + 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); + if (!atomic_inc_not_zero(&anon_vma->refcount)) { + anon_vma = NULL; + goto out; + } + + /* + * If this page is still mapped, then its anon_vma cannot have been + * freed. But if it has been unmapped, we have no security against the + * anon_vma structure being freed and reused (for another anon_vma: + * SLAB_DESTROY_BY_RCU guarantees that - so the atomic_inc_not_zero() + * above cannot corrupt). + */ + if (!page_mapped(page)) { + put_anon_vma(anon_vma); + anon_vma = NULL; + } +out: + rcu_read_unlock(); + + return anon_vma; +} + +/* + * Similar to page_get_anon_vma() except it locks the anon_vma. + * + * Its a little more complex as it tries to keep the fast path to a single + * atomic op -- the trylock. If we fail the trylock, we fall back to getting a + * reference like with page_get_anon_vma() and then block on the mutex. + */ +struct anon_vma *page_lock_anon_vma(struct page *page) +{ + struct anon_vma *anon_vma = NULL; + struct anon_vma *root_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); + root_anon_vma = ACCESS_ONCE(anon_vma->root); + if (mutex_trylock(&root_anon_vma->mutex)) { + /* + * If the page is still mapped, then this anon_vma is still + * its anon_vma, and holding the mutex ensures that it will + * not go away, see anon_vma_free(). + */ + if (!page_mapped(page)) { + mutex_unlock(&root_anon_vma->mutex); + anon_vma = NULL; + } + goto out; + } + + /* trylock failed, we got to sleep */ + if (!atomic_inc_not_zero(&anon_vma->refcount)) { + anon_vma = NULL; + goto out; + } + + if (!page_mapped(page)) { + put_anon_vma(anon_vma); + anon_vma = NULL; + goto out; + } + + /* we pinned the anon_vma, its safe to sleep */ + rcu_read_unlock(); + anon_vma_lock(anon_vma); + + if (atomic_dec_and_test(&anon_vma->refcount)) { + /* + * Oops, we held the last refcount, release the lock + * and bail -- can't simply use put_anon_vma() because + * we'll deadlock on the anon_vma_lock() recursion. + */ + anon_vma_unlock(anon_vma); + __put_anon_vma(anon_vma); + anon_vma = NULL; + } + + return anon_vma; + +out: + rcu_read_unlock(); + return anon_vma; +} + +void page_unlock_anon_vma(struct anon_vma *anon_vma) +{ + anon_vma_unlock(anon_vma); +} + +/* + * 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. + */ +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; + + if (unlikely(is_vm_hugetlb_page(vma))) + pgoff = page->index << huge_page_order(page_hstate(page)); + 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)) { + struct anon_vma *page__anon_vma = page_anon_vma(page); + /* + * Note: swapoff's unuse_vma() is more efficient with this + * check, and needs it to match anon_vma when KSM is active. + */ + if (!vma->anon_vma || !page__anon_vma || + vma->anon_vma->root != page__anon_vma->root) + 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; + + if (unlikely(PageHuge(page))) { + pte = huge_pte_offset(mm, address); + ptl = &mm->page_table_lock; + goto check; + } + + 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; + if (pmd_trans_huge(*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); +check: + 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; + int referenced = 0; + + if (unlikely(PageTransHuge(page))) { + pmd_t *pmd; + + spin_lock(&mm->page_table_lock); + /* + * rmap might return false positives; we must filter + * these out using page_check_address_pmd(). + */ + pmd = page_check_address_pmd(page, mm, address, + PAGE_CHECK_ADDRESS_PMD_FLAG); + if (!pmd) { + spin_unlock(&mm->page_table_lock); + goto out; + } + + if (vma->vm_flags & VM_LOCKED) { + spin_unlock(&mm->page_table_lock); + *mapcount = 0; /* break early from loop */ + *vm_flags |= VM_LOCKED; + goto out; + } + + /* go ahead even if the pmd is pmd_trans_splitting() */ + if (pmdp_clear_flush_young_notify(vma, address, pmd)) + referenced++; + spin_unlock(&mm->page_table_lock); + } else { + pte_t *pte; + spinlock_t *ptl; + + /* + * rmap might return false positives; we must filter + * these out using page_check_address(). + */ + pte = page_check_address(page, mm, address, &ptl, 0); + if (!pte) + goto out; + + if (vma->vm_flags & VM_LOCKED) { + pte_unmap_unlock(pte, ptl); + *mapcount = 0; /* break early from loop */ + *vm_flags |= VM_LOCKED; + goto out; + } + + 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++; + } + pte_unmap_unlock(pte, ptl); + } + + /* 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++; + + (*mapcount)--; + + 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_mutex. + */ + BUG_ON(!PageLocked(page)); + + mutex_lock(&mapping->i_mmap_mutex); + + /* + * i_mmap_mutex does not stabilize mapcount at all, but mapcount + * is more likely to be accurate if we note it after spinning. + */ + mapcount = page_mapcount(page); + + vma_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; + } + + mutex_unlock(&mapping->i_mmap_mutex); + 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_to_pfn(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)); + + mutex_lock(&mapping->i_mmap_mutex); + 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); + } + } + mutex_unlock(&mapping->i_mmap_mutex); + 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_and_clear_dirty(page_to_pfn(page), 1)) + 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 - set up new anonymous rmap + * @page: Page to add to rmap + * @vma: VM area to add page to. + * @address: User virtual address of the mapping + * @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 (PageAnon(page)) + return; + + /* + * If the page isn't exclusively mapped into this vma, + * we must use the _oldest_ possible anon_vma for the + * page mapping! + */ + if (!exclusive) + anon_vma = anon_vma->root; + + 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_anon_vma(page)->root != vma->anon_vma->root); + 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) +{ + do_page_add_anon_rmap(page, vma, address, 0); +} + +/* + * Special version of the above for do_swap_page, which often runs + * into pages that are exclusively owned by the current process. + * Everybody else should continue to use page_add_anon_rmap above. + */ +void do_page_add_anon_rmap(struct page *page, + struct vm_area_struct *vma, unsigned long address, int exclusive) +{ + int first = atomic_inc_and_test(&page->_mapcount); + if (first) { + if (!PageTransHuge(page)) + __inc_zone_page_state(page, NR_ANON_PAGES); + else + __inc_zone_page_state(page, + NR_ANON_TRANSPARENT_HUGEPAGES); + } + if (unlikely(PageKsm(page))) + return; + + VM_BUG_ON(!PageLocked(page)); + /* address might be in next vma when migration races vma_adjust */ + if (first) + __page_set_anon_rmap(page, vma, address, exclusive); + 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) */ + if (!PageTransHuge(page)) + __inc_zone_page_state(page, NR_ANON_PAGES); + else + __inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES); + __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_inc_page_stat(page, MEMCG_NR_FILE_MAPPED); + } +} + +/** + * 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_and_clear_dirty(page_to_pfn(page), 1)) + set_page_dirty(page); + /* + * Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED + * and not charged by memcg for now. + */ + if (unlikely(PageHuge(page))) + return; + if (PageAnon(page)) { + mem_cgroup_uncharge_page(page); + if (!PageTransHuge(page)) + __dec_zone_page_state(page, NR_ANON_PAGES); + else + __dec_zone_page_state(page, + NR_ANON_TRANSPARENT_HUGEPAGES); + } else { + __dec_zone_page_state(page, NR_FILE_MAPPED); + mem_cgroup_dec_page_stat(page, MEMCG_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. + */ +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->mutex or mapping->i_mmap_mutex. + * 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; +} + +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; + + mutex_lock(&mapping->i_mmap_mutex); + 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(); + + 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(); + 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: + mutex_unlock(&mapping->i_mmap_mutex); + 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)); + VM_BUG_ON(!PageHuge(page) && PageTransHuge(page)); + + if (unlikely(PageKsm(page))) + ret = try_to_unmap_ksm(page, flags); + else if (PageAnon(page)) + ret = try_to_unmap_anon(page, flags); + else + ret = try_to_unmap_file(page, flags); + 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); +} + +void __put_anon_vma(struct anon_vma *anon_vma) +{ + struct anon_vma *root = anon_vma->root; + + if (root != anon_vma && atomic_dec_and_test(&root->refcount)) + anon_vma_free(root); + + anon_vma_free(anon_vma); +} + +#ifdef CONFIG_MIGRATION +/* + * rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file(): + * Called by migrate.c to remove migration ptes, but might be used more later. + */ +static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *, + struct vm_area_struct *, unsigned long, void *), void *arg) +{ + 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; + mutex_lock(&mapping->i_mmap_mutex); + 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. + */ + mutex_unlock(&mapping->i_mmap_mutex); + return ret; +} + +int rmap_walk(struct page *page, int (*rmap_one)(struct page *, + struct vm_area_struct *, unsigned long, void *), void *arg) +{ + 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 */ + +#ifdef CONFIG_HUGETLB_PAGE +/* + * The following three functions are for anonymous (private mapped) hugepages. + * Unlike common anonymous pages, anonymous hugepages have no accounting code + * and no lru code, because we handle hugepages differently from common pages. + */ +static void __hugepage_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 (PageAnon(page)) + return; + if (!exclusive) + anon_vma = anon_vma->root; + + anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; + page->mapping = (struct address_space *) anon_vma; + page->index = linear_page_index(vma, address); +} + +void hugepage_add_anon_rmap(struct page *page, + struct vm_area_struct *vma, unsigned long address) +{ + struct anon_vma *anon_vma = vma->anon_vma; + int first; + + BUG_ON(!PageLocked(page)); + BUG_ON(!anon_vma); + /* address might be in next vma when migration races vma_adjust */ + first = atomic_inc_and_test(&page->_mapcount); + if (first) + __hugepage_set_anon_rmap(page, vma, address, 0); +} + +void hugepage_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); + __hugepage_set_anon_rmap(page, vma, address, 1); +} +#endif /* CONFIG_HUGETLB_PAGE */ |