| /* |
| * 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) |
| * mm->mmap_sem |
| * page->flags PG_locked (lock_page) |
| * hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share) |
| * mapping->i_mmap_rwsem |
| * anon_vma->rwsem |
| * 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) |
| * mem_cgroup_{begin,end}_page_stat (memcg->move_lock) |
| * mapping->tree_lock (widely used) |
| * inode->i_lock (in set_page_dirty's __mark_inode_dirty) |
| * bdi.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 bdi.wb->list_lock in __sync_single_inode) |
| * |
| * anon_vma->rwsem,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/export.h> |
| #include <linux/memcontrol.h> |
| #include <linux/mmu_notifier.h> |
| #include <linux/migrate.h> |
| #include <linux/hugetlb.h> |
| #include <linux/backing-dev.h> |
| #include <linux/page_idle.h> |
| |
| #include <asm/tlbflush.h> |
| |
| #include <trace/events/tlb.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); |
| anon_vma->degree = 1; /* Reference for first vma */ |
| anon_vma->parent = anon_vma; |
| /* |
| * 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_read() 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 |
| * down_read_trylock() from page_lock_anon_vma_read(). This orders: |
| * |
| * page_lock_anon_vma_read() VS put_anon_vma() |
| * down_read_trylock() atomic_dec_and_test() |
| * LOCK MB |
| * atomic_read() rwsem_is_locked() |
| * |
| * LOCK should suffice since the actual taking of the lock must |
| * happen _before_ what follows. |
| */ |
| might_sleep(); |
| if (rwsem_is_locked(&anon_vma->root->rwsem)) { |
| anon_vma_lock_write(anon_vma); |
| anon_vma_unlock_write(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); |
| } |
| |
| 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_interval_tree_insert(avc, &anon_vma->rb_root); |
| } |
| |
| /** |
| * __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, which |
| * is handled inline by anon_vma_prepare(). 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_read() |
| * 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 mm_struct *mm = vma->vm_mm; |
| struct anon_vma *anon_vma, *allocated; |
| struct anon_vma_chain *avc; |
| |
| might_sleep(); |
| |
| 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_write(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; |
| anon_vma_chain_link(vma, avc, anon_vma); |
| /* vma reference or self-parent link for new root */ |
| anon_vma->degree++; |
| allocated = NULL; |
| avc = NULL; |
| } |
| spin_unlock(&mm->page_table_lock); |
| anon_vma_unlock_write(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)) |
| up_write(&root->rwsem); |
| root = new_root; |
| down_write(&root->rwsem); |
| } |
| return root; |
| } |
| |
| static inline void unlock_anon_vma_root(struct anon_vma *root) |
| { |
| if (root) |
| up_write(&root->rwsem); |
| } |
| |
| /* |
| * Attach the anon_vmas from src to dst. |
| * Returns 0 on success, -ENOMEM on failure. |
| * |
| * If dst->anon_vma is NULL this function tries to find and reuse existing |
| * anon_vma which has no vmas and only one child anon_vma. This prevents |
| * degradation of anon_vma hierarchy to endless linear chain in case of |
| * constantly forking task. On the other hand, an anon_vma with more than one |
| * child isn't reused even if there was no alive vma, thus rmap walker has a |
| * good chance of avoiding scanning the whole hierarchy when it searches where |
| * page is mapped. |
| */ |
| 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); |
| |
| /* |
| * Reuse existing anon_vma if its degree lower than two, |
| * that means it has no vma and only one anon_vma child. |
| * |
| * Do not chose parent anon_vma, otherwise first child |
| * will always reuse it. Root anon_vma is never reused: |
| * it has self-parent reference and at least one child. |
| */ |
| if (!dst->anon_vma && anon_vma != src->anon_vma && |
| anon_vma->degree < 2) |
| dst->anon_vma = anon_vma; |
| } |
| if (dst->anon_vma) |
| dst->anon_vma->degree++; |
| unlock_anon_vma_root(root); |
| return 0; |
| |
| enomem_failure: |
| /* |
| * dst->anon_vma is dropped here otherwise its degree can be incorrectly |
| * decremented in unlink_anon_vmas(). |
| * We can safely do this because callers of anon_vma_clone() don't care |
| * about dst->anon_vma if anon_vma_clone() failed. |
| */ |
| dst->anon_vma = NULL; |
| 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; |
| int error; |
| |
| /* Don't bother if the parent process has no anon_vma here. */ |
| if (!pvma->anon_vma) |
| return 0; |
| |
| /* Drop inherited anon_vma, we'll reuse existing or allocate new. */ |
| vma->anon_vma = NULL; |
| |
| /* |
| * First, attach the new VMA to the parent VMA's anon_vmas, |
| * so rmap can find non-COWed pages in child processes. |
| */ |
| error = anon_vma_clone(vma, pvma); |
| if (error) |
| return error; |
| |
| /* An existing anon_vma has been reused, all done then. */ |
| if (vma->anon_vma) |
| return 0; |
| |
| /* 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; |
| anon_vma->parent = pvma->anon_vma; |
| /* |
| * 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_write(anon_vma); |
| anon_vma_chain_link(vma, avc, anon_vma); |
| anon_vma->parent->degree++; |
| anon_vma_unlock_write(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); |
| anon_vma_interval_tree_remove(avc, &anon_vma->rb_root); |
| |
| /* |
| * Leave empty anon_vmas on the list - we'll need |
| * to free them outside the lock. |
| */ |
| if (RB_EMPTY_ROOT(&anon_vma->rb_root)) { |
| anon_vma->parent->degree--; |
| continue; |
| } |
| |
| list_del(&avc->same_vma); |
| anon_vma_chain_free(avc); |
| } |
| if (vma->anon_vma) |
| vma->anon_vma->degree--; |
| 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 write-acquire the anon_vma->root->rwsem. |
| */ |
| list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { |
| struct anon_vma *anon_vma = avc->anon_vma; |
| |
| VM_WARN_ON(anon_vma->degree); |
| 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; |
| |
| init_rwsem(&anon_vma->rwsem); |
| atomic_set(&anon_vma->refcount, 0); |
| anon_vma->rb_root = RB_ROOT; |
| } |
| |
| 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|SLAB_ACCOUNT, |
| anon_vma_ctor); |
| anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, |
| SLAB_PANIC|SLAB_ACCOUNT); |
| } |
| |
| /* |
| * 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)READ_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)) { |
| rcu_read_unlock(); |
| put_anon_vma(anon_vma); |
| return 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_read(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)READ_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 = READ_ONCE(anon_vma->root); |
| if (down_read_trylock(&root_anon_vma->rwsem)) { |
| /* |
| * 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)) { |
| up_read(&root_anon_vma->rwsem); |
| 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)) { |
| rcu_read_unlock(); |
| put_anon_vma(anon_vma); |
| return NULL; |
| } |
| |
| /* we pinned the anon_vma, its safe to sleep */ |
| rcu_read_unlock(); |
| anon_vma_lock_read(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_write() recursion. |
| */ |
| anon_vma_unlock_read(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_read(struct anon_vma *anon_vma) |
| { |
| anon_vma_unlock_read(anon_vma); |
| } |
| |
| #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH |
| /* |
| * Flush TLB entries for recently unmapped pages from remote CPUs. It is |
| * important if a PTE was dirty when it was unmapped that it's flushed |
| * before any IO is initiated on the page to prevent lost writes. Similarly, |
| * it must be flushed before freeing to prevent data leakage. |
| */ |
| void try_to_unmap_flush(void) |
| { |
| struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc; |
| int cpu; |
| |
| if (!tlb_ubc->flush_required) |
| return; |
| |
| cpu = get_cpu(); |
| |
| if (cpumask_test_cpu(cpu, &tlb_ubc->cpumask)) { |
| count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL); |
| local_flush_tlb(); |
| trace_tlb_flush(TLB_LOCAL_SHOOTDOWN, TLB_FLUSH_ALL); |
| } |
| |
| if (cpumask_any_but(&tlb_ubc->cpumask, cpu) < nr_cpu_ids) |
| flush_tlb_others(&tlb_ubc->cpumask, NULL, 0, TLB_FLUSH_ALL); |
| cpumask_clear(&tlb_ubc->cpumask); |
| tlb_ubc->flush_required = false; |
| tlb_ubc->writable = false; |
| put_cpu(); |
| } |
| |
| /* Flush iff there are potentially writable TLB entries that can race with IO */ |
| void try_to_unmap_flush_dirty(void) |
| { |
| struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc; |
| |
| if (tlb_ubc->writable) |
| try_to_unmap_flush(); |
| } |
| |
| static void set_tlb_ubc_flush_pending(struct mm_struct *mm, |
| struct page *page, bool writable) |
| { |
| struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc; |
| |
| cpumask_or(&tlb_ubc->cpumask, &tlb_ubc->cpumask, mm_cpumask(mm)); |
| tlb_ubc->flush_required = true; |
| |
| /* |
| * If the PTE was dirty then it's best to assume it's writable. The |
| * caller must use try_to_unmap_flush_dirty() or try_to_unmap_flush() |
| * before the page is queued for IO. |
| */ |
| if (writable) |
| tlb_ubc->writable = true; |
| } |
| |
| /* |
| * Returns true if the TLB flush should be deferred to the end of a batch of |
| * unmap operations to reduce IPIs. |
| */ |
| static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags) |
| { |
| bool should_defer = false; |
| |
| if (!(flags & TTU_BATCH_FLUSH)) |
| return false; |
| |
| /* If remote CPUs need to be flushed then defer batch the flush */ |
| if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids) |
| should_defer = true; |
| put_cpu(); |
| |
| return should_defer; |
| } |
| #else |
| static void set_tlb_ubc_flush_pending(struct mm_struct *mm, |
| struct page *page, bool writable) |
| { |
| } |
| |
| static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags) |
| { |
| return false; |
| } |
| #endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */ |
| |
| /* |
| * 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) |
| { |
| unsigned long address; |
| 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) { |
| if (!vma->vm_file || vma->vm_file->f_mapping != page->mapping) |
| return -EFAULT; |
| } else |
| return -EFAULT; |
| address = __vma_address(page, vma); |
| if (unlikely(address < vma->vm_start || address >= vma->vm_end)) |
| return -EFAULT; |
| return address; |
| } |
| |
| pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address) |
| { |
| pgd_t *pgd; |
| pud_t *pud; |
| pmd_t *pmd = NULL; |
| pmd_t pmde; |
| |
| pgd = pgd_offset(mm, address); |
| if (!pgd_present(*pgd)) |
| goto out; |
| |
| pud = pud_offset(pgd, address); |
| if (!pud_present(*pud)) |
| goto out; |
| |
| pmd = pmd_offset(pud, address); |
| /* |
| * Some THP functions use the sequence pmdp_huge_clear_flush(), set_pmd_at() |
| * without holding anon_vma lock for write. So when looking for a |
| * genuine pmde (in which to find pte), test present and !THP together. |
| */ |
| pmde = *pmd; |
| barrier(); |
| if (!pmd_present(pmde) || pmd_trans_huge(pmde)) |
| pmd = NULL; |
| out: |
| return pmd; |
| } |
| |
| /* |
| * 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) |
| { |
| pmd_t *pmd; |
| pte_t *pte; |
| spinlock_t *ptl; |
| |
| if (unlikely(PageHuge(page))) { |
| /* when pud is not present, pte will be NULL */ |
| pte = huge_pte_offset(mm, address); |
| if (!pte) |
| return NULL; |
| |
| ptl = huge_pte_lockptr(page_hstate(page), mm, pte); |
| goto check; |
| } |
| |
| pmd = mm_find_pmd(mm, address); |
| if (!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 (unlikely(address < vma->vm_start || address >= vma->vm_end)) |
| 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; |
| } |
| |
| #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| /* |
| * Check that @page is mapped at @address into @mm. In contrast to |
| * page_check_address(), this function can handle transparent huge pages. |
| * |
| * On success returns true with pte mapped and locked. For PMD-mapped |
| * transparent huge pages *@ptep is set to NULL. |
| */ |
| bool page_check_address_transhuge(struct page *page, struct mm_struct *mm, |
| unsigned long address, pmd_t **pmdp, |
| pte_t **ptep, spinlock_t **ptlp) |
| { |
| pgd_t *pgd; |
| pud_t *pud; |
| pmd_t *pmd; |
| pte_t *pte; |
| spinlock_t *ptl; |
| |
| if (unlikely(PageHuge(page))) { |
| /* when pud is not present, pte will be NULL */ |
| pte = huge_pte_offset(mm, address); |
| if (!pte) |
| return false; |
| |
| ptl = huge_pte_lockptr(page_hstate(page), mm, pte); |
| pmd = NULL; |
| goto check_pte; |
| } |
| |
| pgd = pgd_offset(mm, address); |
| if (!pgd_present(*pgd)) |
| return false; |
| pud = pud_offset(pgd, address); |
| if (!pud_present(*pud)) |
| return false; |
| pmd = pmd_offset(pud, address); |
| |
| if (pmd_trans_huge(*pmd)) { |
| ptl = pmd_lock(mm, pmd); |
| if (!pmd_present(*pmd)) |
| goto unlock_pmd; |
| if (unlikely(!pmd_trans_huge(*pmd))) { |
| spin_unlock(ptl); |
| goto map_pte; |
| } |
| |
| if (pmd_page(*pmd) != page) |
| goto unlock_pmd; |
| |
| pte = NULL; |
| goto found; |
| unlock_pmd: |
| spin_unlock(ptl); |
| return false; |
| } else { |
| pmd_t pmde = *pmd; |
| |
| barrier(); |
| if (!pmd_present(pmde) || pmd_trans_huge(pmde)) |
| return false; |
| } |
| map_pte: |
| pte = pte_offset_map(pmd, address); |
| if (!pte_present(*pte)) { |
| pte_unmap(pte); |
| return false; |
| } |
| |
| ptl = pte_lockptr(mm, pmd); |
| check_pte: |
| spin_lock(ptl); |
| |
| if (!pte_present(*pte)) { |
| pte_unmap_unlock(pte, ptl); |
| return false; |
| } |
| |
| /* THP can be referenced by any subpage */ |
| if (pte_pfn(*pte) - page_to_pfn(page) >= hpage_nr_pages(page)) { |
| pte_unmap_unlock(pte, ptl); |
| return false; |
| } |
| found: |
| *ptep = pte; |
| *pmdp = pmd; |
| *ptlp = ptl; |
| return true; |
| } |
| #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ |
| |
| struct page_referenced_arg { |
| int mapcount; |
| int referenced; |
| unsigned long vm_flags; |
| struct mem_cgroup *memcg; |
| }; |
| /* |
| * arg: page_referenced_arg will be passed |
| */ |
| static int page_referenced_one(struct page *page, struct vm_area_struct *vma, |
| unsigned long address, void *arg) |
| { |
| struct page_referenced_arg *pra = arg; |
| struct page_vma_mapped_walk pvmw = { |
| .page = page, |
| .vma = vma, |
| .address = address, |
| }; |
| int referenced = 0; |
| |
| while (page_vma_mapped_walk(&pvmw)) { |
| address = pvmw.address; |
| |
| if (vma->vm_flags & VM_LOCKED) { |
| page_vma_mapped_walk_done(&pvmw); |
| pra->vm_flags |= VM_LOCKED; |
| return SWAP_FAIL; /* To break the loop */ |
| } |
| |
| if (pvmw.pte) { |
| if (ptep_clear_flush_young_notify(vma, address, |
| pvmw.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(!(vma->vm_flags & VM_SEQ_READ))) |
| referenced++; |
| } |
| } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { |
| if (pmdp_clear_flush_young_notify(vma, address, |
| pvmw.pmd)) |
| referenced++; |
| } else { |
| /* unexpected pmd-mapped page? */ |
| WARN_ON_ONCE(1); |
| } |
| |
| pra->mapcount--; |
| } |
| |
| if (referenced) |
| clear_page_idle(page); |
| if (test_and_clear_page_young(page)) |
| referenced++; |
| |
| if (referenced) { |
| pra->referenced++; |
| pra->vm_flags |= vma->vm_flags; |
| } |
| |
| if (!pra->mapcount) |
| return SWAP_SUCCESS; /* To break the loop */ |
| |
| return SWAP_AGAIN; |
| } |
| |
| static bool invalid_page_referenced_vma(struct vm_area_struct *vma, void *arg) |
| { |
| struct page_referenced_arg *pra = arg; |
| struct mem_cgroup *memcg = pra->memcg; |
| |
| if (!mm_match_cgroup(vma->vm_mm, memcg)) |
| return true; |
| |
| return false; |
| } |
| |
| /** |
| * page_referenced - test if the page was referenced |
| * @page: the page to test |
| * @is_locked: caller holds lock on the page |
| * @memcg: target memory cgroup |
| * @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 *memcg, |
| unsigned long *vm_flags) |
| { |
| int ret; |
| int we_locked = 0; |
| struct page_referenced_arg pra = { |
| .mapcount = total_mapcount(page), |
| .memcg = memcg, |
| }; |
| struct rmap_walk_control rwc = { |
| .rmap_one = page_referenced_one, |
| .arg = (void *)&pra, |
| .anon_lock = page_lock_anon_vma_read, |
| }; |
| |
| *vm_flags = 0; |
| if (!page_mapped(page)) |
| return 0; |
| |
| if (!page_rmapping(page)) |
| return 0; |
| |
| if (!is_locked && (!PageAnon(page) || PageKsm(page))) { |
| we_locked = trylock_page(page); |
| if (!we_locked) |
| return 1; |
| } |
| |
| /* |
| * If we are reclaiming on behalf of a cgroup, skip |
| * counting on behalf of references from different |
| * cgroups |
| */ |
| if (memcg) { |
| rwc.invalid_vma = invalid_page_referenced_vma; |
| } |
| |
| ret = rmap_walk(page, &rwc); |
| *vm_flags = pra.vm_flags; |
| |
| if (we_locked) |
| unlock_page(page); |
| |
| return pra.referenced; |
| } |
| |
| static int page_mkclean_one(struct page *page, struct vm_area_struct *vma, |
| unsigned long address, void *arg) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| pte_t *pte; |
| spinlock_t *ptl; |
| int ret = 0; |
| int *cleaned = arg; |
| |
| pte = page_check_address(page, mm, address, &ptl, 1); |
| if (!pte) |
| goto out; |
| |
| if (pte_dirty(*pte) || pte_write(*pte)) { |
| pte_t entry; |
| |
| flush_cache_page(vma, address, pte_pfn(*pte)); |
| entry = ptep_clear_flush(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); |
| |
| if (ret) { |
| mmu_notifier_invalidate_page(mm, address); |
| (*cleaned)++; |
| } |
| out: |
| return SWAP_AGAIN; |
| } |
| |
| static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg) |
| { |
| if (vma->vm_flags & VM_SHARED) |
| return false; |
| |
| return true; |
| } |
| |
| int page_mkclean(struct page *page) |
| { |
| int cleaned = 0; |
| struct address_space *mapping; |
| struct rmap_walk_control rwc = { |
| .arg = (void *)&cleaned, |
| .rmap_one = page_mkclean_one, |
| .invalid_vma = invalid_mkclean_vma, |
| }; |
| |
| BUG_ON(!PageLocked(page)); |
| |
| if (!page_mapped(page)) |
| return 0; |
| |
| mapping = page_mapping(page); |
| if (!mapping) |
| return 0; |
| |
| rmap_walk(page, &rwc); |
| |
| return cleaned; |
| } |
| 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 |
| * |
| * 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) |
| { |
| struct anon_vma *anon_vma = vma->anon_vma; |
| |
| page = compound_head(page); |
| |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| VM_BUG_ON_VMA(!anon_vma, vma); |
| |
| anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
| /* |
| * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written |
| * simultaneously, so a concurrent reader (eg page_referenced()'s |
| * PageAnon()) will not see one without the other. |
| */ |
| WRITE_ONCE(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_to_pgoff(page) != 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 |
| * @compound: charge the page as compound or small page |
| * |
| * 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, bool compound) |
| { |
| do_page_add_anon_rmap(page, vma, address, compound ? RMAP_COMPOUND : 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 flags) |
| { |
| bool compound = flags & RMAP_COMPOUND; |
| bool first; |
| |
| if (compound) { |
| atomic_t *mapcount; |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| VM_BUG_ON_PAGE(!PageTransHuge(page), page); |
| mapcount = compound_mapcount_ptr(page); |
| first = atomic_inc_and_test(mapcount); |
| } else { |
| first = atomic_inc_and_test(&page->_mapcount); |
| } |
| |
| if (first) { |
| int nr = compound ? hpage_nr_pages(page) : 1; |
| /* |
| * We use the irq-unsafe __{inc|mod}_zone_page_stat because |
| * these counters are not modified in interrupt context, and |
| * pte lock(a spinlock) is held, which implies preemption |
| * disabled. |
| */ |
| if (compound) |
| __inc_node_page_state(page, NR_ANON_THPS); |
| __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, nr); |
| } |
| if (unlikely(PageKsm(page))) |
| return; |
| |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| |
| /* address might be in next vma when migration races vma_adjust */ |
| if (first) |
| __page_set_anon_rmap(page, vma, address, |
| flags & RMAP_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 |
| * @compound: charge the page as compound or small page |
| * |
| * 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, bool compound) |
| { |
| int nr = compound ? hpage_nr_pages(page) : 1; |
| |
| VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma); |
| __SetPageSwapBacked(page); |
| if (compound) { |
| VM_BUG_ON_PAGE(!PageTransHuge(page), page); |
| /* increment count (starts at -1) */ |
| atomic_set(compound_mapcount_ptr(page), 0); |
| __inc_node_page_state(page, NR_ANON_THPS); |
| } else { |
| /* Anon THP always mapped first with PMD */ |
| VM_BUG_ON_PAGE(PageTransCompound(page), page); |
| /* increment count (starts at -1) */ |
| atomic_set(&page->_mapcount, 0); |
| } |
| __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, nr); |
| __page_set_anon_rmap(page, vma, address, 1); |
| } |
| |
| /** |
| * 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, bool compound) |
| { |
| int i, nr = 1; |
| |
| VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page); |
| lock_page_memcg(page); |
| if (compound && PageTransHuge(page)) { |
| for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) { |
| if (atomic_inc_and_test(&page[i]._mapcount)) |
| nr++; |
| } |
| if (!atomic_inc_and_test(compound_mapcount_ptr(page))) |
| goto out; |
| VM_BUG_ON_PAGE(!PageSwapBacked(page), page); |
| __inc_node_page_state(page, NR_SHMEM_PMDMAPPED); |
| } else { |
| if (PageTransCompound(page) && page_mapping(page)) { |
| VM_WARN_ON_ONCE(!PageLocked(page)); |
| |
| SetPageDoubleMap(compound_head(page)); |
| if (PageMlocked(page)) |
| clear_page_mlock(compound_head(page)); |
| } |
| if (!atomic_inc_and_test(&page->_mapcount)) |
| goto out; |
| } |
| __mod_node_page_state(page_pgdat(page), NR_FILE_MAPPED, nr); |
| mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED); |
| out: |
| unlock_page_memcg(page); |
| } |
| |
| static void page_remove_file_rmap(struct page *page, bool compound) |
| { |
| int i, nr = 1; |
| |
| VM_BUG_ON_PAGE(compound && !PageHead(page), page); |
| lock_page_memcg(page); |
| |
| /* Hugepages are not counted in NR_FILE_MAPPED for now. */ |
| if (unlikely(PageHuge(page))) { |
| /* hugetlb pages are always mapped with pmds */ |
| atomic_dec(compound_mapcount_ptr(page)); |
| goto out; |
| } |
| |
| /* page still mapped by someone else? */ |
| if (compound && PageTransHuge(page)) { |
| for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) { |
| if (atomic_add_negative(-1, &page[i]._mapcount)) |
| nr++; |
| } |
| if (!atomic_add_negative(-1, compound_mapcount_ptr(page))) |
| goto out; |
| VM_BUG_ON_PAGE(!PageSwapBacked(page), page); |
| __dec_node_page_state(page, NR_SHMEM_PMDMAPPED); |
| } else { |
| if (!atomic_add_negative(-1, &page->_mapcount)) |
| goto out; |
| } |
| |
| /* |
| * We use the irq-unsafe __{inc|mod}_zone_page_state because |
| * these counters are not modified in interrupt context, and |
| * pte lock(a spinlock) is held, which implies preemption disabled. |
| */ |
| __mod_node_page_state(page_pgdat(page), NR_FILE_MAPPED, -nr); |
| mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_FILE_MAPPED); |
| |
| if (unlikely(PageMlocked(page))) |
| clear_page_mlock(page); |
| out: |
| unlock_page_memcg(page); |
| } |
| |
| static void page_remove_anon_compound_rmap(struct page *page) |
| { |
| int i, nr; |
| |
| if (!atomic_add_negative(-1, compound_mapcount_ptr(page))) |
| return; |
| |
| /* Hugepages are not counted in NR_ANON_PAGES for now. */ |
| if (unlikely(PageHuge(page))) |
| return; |
| |
| if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) |
| return; |
| |
| __dec_node_page_state(page, NR_ANON_THPS); |
| |
| if (TestClearPageDoubleMap(page)) { |
| /* |
| * Subpages can be mapped with PTEs too. Check how many of |
| * themi are still mapped. |
| */ |
| for (i = 0, nr = 0; i < HPAGE_PMD_NR; i++) { |
| if (atomic_add_negative(-1, &page[i]._mapcount)) |
| nr++; |
| } |
| } else { |
| nr = HPAGE_PMD_NR; |
| } |
| |
| if (unlikely(PageMlocked(page))) |
| clear_page_mlock(page); |
| |
| if (nr) { |
| __mod_node_page_state(page_pgdat(page), NR_ANON_MAPPED, -nr); |
| deferred_split_huge_page(page); |
| } |
| } |
| |
| /** |
| * page_remove_rmap - take down pte mapping from a page |
| * @page: page to remove mapping from |
| * @compound: uncharge the page as compound or small page |
| * |
| * The caller needs to hold the pte lock. |
| */ |
| void page_remove_rmap(struct page *page, bool compound) |
| { |
| if (!PageAnon(page)) |
| return page_remove_file_rmap(page, compound); |
| |
| if (compound) |
| return page_remove_anon_compound_rmap(page); |
| |
| /* page still mapped by someone else? */ |
| if (!atomic_add_negative(-1, &page->_mapcount)) |
| return; |
| |
| /* |
| * We use the irq-unsafe __{inc|mod}_zone_page_stat because |
| * these counters are not modified in interrupt context, and |
| * pte lock(a spinlock) is held, which implies preemption disabled. |
| */ |
| __dec_node_page_state(page, NR_ANON_MAPPED); |
| |
| if (unlikely(PageMlocked(page))) |
| clear_page_mlock(page); |
| |
| if (PageTransCompound(page)) |
| deferred_split_huge_page(compound_head(page)); |
| |
| /* |
| * 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. |
| */ |
| } |
| |
| struct rmap_private { |
| enum ttu_flags flags; |
| int lazyfreed; |
| }; |
| |
| /* |
| * @arg: enum ttu_flags will be passed to this argument |
| */ |
| static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, |
| unsigned long address, void *arg) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| pte_t *pte; |
| pte_t pteval; |
| spinlock_t *ptl; |
| int ret = SWAP_AGAIN; |
| struct rmap_private *rp = arg; |
| enum ttu_flags flags = rp->flags; |
| |
| /* munlock has nothing to gain from examining un-locked vmas */ |
| if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED)) |
| goto out; |
| |
| if (flags & TTU_SPLIT_HUGE_PMD) { |
| split_huge_pmd_address(vma, address, |
| flags & TTU_MIGRATION, page); |
| /* check if we have anything to do after split */ |
| if (page_mapcount(page) == 0) |
| goto out; |
| } |
| |
| pte = page_check_address(page, mm, address, &ptl, |
| PageTransCompound(page)); |
| 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) { |
| /* PTE-mapped THP are never mlocked */ |
| if (!PageTransCompound(page)) { |
| /* |
| * Holding pte lock, we do *not* need |
| * mmap_sem here |
| */ |
| mlock_vma_page(page); |
| } |
| ret = SWAP_MLOCK; |
| goto out_unmap; |
| } |
| if (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)); |
| if (should_defer_flush(mm, flags)) { |
| /* |
| * We clear the PTE but do not flush so potentially a remote |
| * CPU could still be writing to the page. If the entry was |
| * previously clean then the architecture must guarantee that |
| * a clear->dirty transition on a cached TLB entry is written |
| * through and traps if the PTE is unmapped. |
| */ |
| pteval = ptep_get_and_clear(mm, address, pte); |
| |
| set_tlb_ubc_flush_pending(mm, page, pte_dirty(pteval)); |
| } else { |
| pteval = ptep_clear_flush(vma, address, pte); |
| } |
| |
| /* Move the dirty bit to the physical page now the pte is gone. */ |
| if (pte_dirty(pteval)) |
| set_page_dirty(page); |
| |
| /* Update high watermark before we lower rss */ |
| update_hiwater_rss(mm); |
| |
| if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) { |
| if (PageHuge(page)) { |
| hugetlb_count_sub(1 << compound_order(page), mm); |
| } else { |
| dec_mm_counter(mm, mm_counter(page)); |
| } |
| set_pte_at(mm, address, pte, |
| swp_entry_to_pte(make_hwpoison_entry(page))); |
| } else if (pte_unused(pteval)) { |
| /* |
| * The guest indicated that the page content is of no |
| * interest anymore. Simply discard the pte, vmscan |
| * will take care of the rest. |
| */ |
| dec_mm_counter(mm, mm_counter(page)); |
| } else if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION)) { |
| swp_entry_t entry; |
| pte_t swp_pte; |
| /* |
| * 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. |
| */ |
| entry = make_migration_entry(page, pte_write(pteval)); |
| swp_pte = swp_entry_to_pte(entry); |
| if (pte_soft_dirty(pteval)) |
| swp_pte = pte_swp_mksoft_dirty(swp_pte); |
| set_pte_at(mm, address, pte, swp_pte); |
| } else if (PageAnon(page)) { |
| swp_entry_t entry = { .val = page_private(page) }; |
| pte_t swp_pte; |
| /* |
| * Store the swap location in the pte. |
| * See handle_pte_fault() ... |
| */ |
| VM_BUG_ON_PAGE(!PageSwapCache(page), page); |
| |
| if (!PageDirty(page) && (flags & TTU_LZFREE)) { |
| /* It's a freeable page by MADV_FREE */ |
| dec_mm_counter(mm, MM_ANONPAGES); |
| rp->lazyfreed++; |
| goto discard; |
| } |
| |
| 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); |
| swp_pte = swp_entry_to_pte(entry); |
| if (pte_soft_dirty(pteval)) |
| swp_pte = pte_swp_mksoft_dirty(swp_pte); |
| set_pte_at(mm, address, pte, swp_pte); |
| } else |
| dec_mm_counter(mm, mm_counter_file(page)); |
| |
| discard: |
| page_remove_rmap(page, PageHuge(page)); |
| put_page(page); |
| |
| out_unmap: |
| pte_unmap_unlock(pte, ptl); |
| if (ret != SWAP_FAIL && ret != SWAP_MLOCK && !(flags & TTU_MUNLOCK)) |
| mmu_notifier_invalidate_page(mm, address); |
| out: |
| return ret; |
| } |
| |
| bool is_vma_temporary_stack(struct vm_area_struct *vma) |
| { |
| int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP); |
| |
| if (!maybe_stack) |
| return false; |
| |
| if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) == |
| VM_STACK_INCOMPLETE_SETUP) |
| return true; |
| |
| return false; |
| } |
| |
| static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg) |
| { |
| return is_vma_temporary_stack(vma); |
| } |
| |
| static int page_mapcount_is_zero(struct page *page) |
| { |
| return !page_mapcount(page); |
| } |
| |
| /** |
| * 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; |
| struct rmap_private rp = { |
| .flags = flags, |
| .lazyfreed = 0, |
| }; |
| |
| struct rmap_walk_control rwc = { |
| .rmap_one = try_to_unmap_one, |
| .arg = &rp, |
| .done = page_mapcount_is_zero, |
| .anon_lock = page_lock_anon_vma_read, |
| }; |
| |
| /* |
| * During exec, a temporary VMA is setup and later moved. |
| * The VMA is moved under the anon_vma lock but not the |
| * page tables leading to a race where migration cannot |
| * find the migration ptes. Rather than increasing the |
| * locking requirements of exec(), migration skips |
| * temporary VMAs until after exec() completes. |
| */ |
| if ((flags & TTU_MIGRATION) && !PageKsm(page) && PageAnon(page)) |
| rwc.invalid_vma = invalid_migration_vma; |
| |
| if (flags & TTU_RMAP_LOCKED) |
| ret = rmap_walk_locked(page, &rwc); |
| else |
| ret = rmap_walk(page, &rwc); |
| |
| if (ret != SWAP_MLOCK && !page_mapcount(page)) { |
| ret = SWAP_SUCCESS; |
| if (rp.lazyfreed && !PageDirty(page)) |
| ret = SWAP_LZFREE; |
| } |
| return ret; |
| } |
| |
| static int page_not_mapped(struct page *page) |
| { |
| return !page_mapped(page); |
| }; |
| |
| /** |
| * 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) |
| { |
| int ret; |
| struct rmap_private rp = { |
| .flags = TTU_MUNLOCK, |
| .lazyfreed = 0, |
| }; |
| |
| struct rmap_walk_control rwc = { |
| .rmap_one = try_to_unmap_one, |
| .arg = &rp, |
| .done = page_not_mapped, |
| .anon_lock = page_lock_anon_vma_read, |
| |
| }; |
| |
| VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page); |
| |
| ret = rmap_walk(page, &rwc); |
| return ret; |
| } |
| |
| void __put_anon_vma(struct anon_vma *anon_vma) |
| { |
| struct anon_vma *root = anon_vma->root; |
| |
| anon_vma_free(anon_vma); |
| if (root != anon_vma && atomic_dec_and_test(&root->refcount)) |
| anon_vma_free(root); |
| } |
| |
| static struct anon_vma *rmap_walk_anon_lock(struct page *page, |
| struct rmap_walk_control *rwc) |
| { |
| struct anon_vma *anon_vma; |
| |
| if (rwc->anon_lock) |
| return rwc->anon_lock(page); |
| |
| /* |
| * Note: remove_migration_ptes() cannot use page_lock_anon_vma_read() |
| * 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 NULL; |
| |
| anon_vma_lock_read(anon_vma); |
| return anon_vma; |
| } |
| |
| /* |
| * rmap_walk_anon - do something to anonymous page using the object-based |
| * rmap method |
| * @page: the page to be handled |
| * @rwc: control variable according to each walk type |
| * |
| * Find all the mappings of a page using the mapping pointer and the vma chains |
| * contained in the anon_vma struct it points to. |
| * |
| * When called from try_to_munlock(), the mmap_sem of the mm containing the vma |
| * where the page was found will be held for write. So, we won't recheck |
| * vm_flags for that VMA. That should be OK, because that vma shouldn't be |
| * LOCKED. |
| */ |
| static int rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc, |
| bool locked) |
| { |
| struct anon_vma *anon_vma; |
| pgoff_t pgoff; |
| struct anon_vma_chain *avc; |
| int ret = SWAP_AGAIN; |
| |
| if (locked) { |
| anon_vma = page_anon_vma(page); |
| /* anon_vma disappear under us? */ |
| VM_BUG_ON_PAGE(!anon_vma, page); |
| } else { |
| anon_vma = rmap_walk_anon_lock(page, rwc); |
| } |
| if (!anon_vma) |
| return ret; |
| |
| pgoff = page_to_pgoff(page); |
| anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) { |
| struct vm_area_struct *vma = avc->vma; |
| unsigned long address = vma_address(page, vma); |
| |
| cond_resched(); |
| |
| if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) |
| continue; |
| |
| ret = rwc->rmap_one(page, vma, address, rwc->arg); |
| if (ret != SWAP_AGAIN) |
| break; |
| if (rwc->done && rwc->done(page)) |
| break; |
| } |
| |
| if (!locked) |
| anon_vma_unlock_read(anon_vma); |
| return ret; |
| } |
| |
| /* |
| * rmap_walk_file - do something to file page using the object-based rmap method |
| * @page: the page to be handled |
| * @rwc: control variable according to each walk type |
| * |
| * Find all the mappings of a page using the mapping pointer and the vma chains |
| * contained in the address_space struct it points to. |
| * |
| * When called from try_to_munlock(), the mmap_sem of the mm containing the vma |
| * where the page was found will be held for write. So, we won't recheck |
| * vm_flags for that VMA. That should be OK, because that vma shouldn't be |
| * LOCKED. |
| */ |
| static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc, |
| bool locked) |
| { |
| struct address_space *mapping = page_mapping(page); |
| pgoff_t pgoff; |
| struct vm_area_struct *vma; |
| int ret = SWAP_AGAIN; |
| |
| /* |
| * The page lock not only makes sure that page->mapping cannot |
| * suddenly be NULLified by truncation, it makes sure that the |
| * structure at mapping cannot be freed and reused yet, |
| * so we can safely take mapping->i_mmap_rwsem. |
| */ |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| |
| if (!mapping) |
| return ret; |
| |
| pgoff = page_to_pgoff(page); |
| if (!locked) |
| i_mmap_lock_read(mapping); |
| vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { |
| unsigned long address = vma_address(page, vma); |
| |
| cond_resched(); |
| |
| if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) |
| continue; |
| |
| ret = rwc->rmap_one(page, vma, address, rwc->arg); |
| if (ret != SWAP_AGAIN) |
| goto done; |
| if (rwc->done && rwc->done(page)) |
| goto done; |
| } |
| |
| done: |
| if (!locked) |
| i_mmap_unlock_read(mapping); |
| return ret; |
| } |
| |
| int rmap_walk(struct page *page, struct rmap_walk_control *rwc) |
| { |
| if (unlikely(PageKsm(page))) |
| return rmap_walk_ksm(page, rwc); |
| else if (PageAnon(page)) |
| return rmap_walk_anon(page, rwc, false); |
| else |
| return rmap_walk_file(page, rwc, false); |
| } |
| |
| /* Like rmap_walk, but caller holds relevant rmap lock */ |
| int rmap_walk_locked(struct page *page, struct rmap_walk_control *rwc) |
| { |
| /* no ksm support for now */ |
| VM_BUG_ON_PAGE(PageKsm(page), page); |
| if (PageAnon(page)) |
| return rmap_walk_anon(page, rwc, true); |
| else |
| return rmap_walk_file(page, rwc, true); |
| } |
| |
| #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(compound_mapcount_ptr(page)); |
| 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(compound_mapcount_ptr(page), 0); |
| __hugepage_set_anon_rmap(page, vma, address, 1); |
| } |
| #endif /* CONFIG_HUGETLB_PAGE */ |