diff options
Diffstat (limited to 'mm/rmap.c')
| -rw-r--r-- | mm/rmap.c | 1996 |
1 files changed, 1996 insertions, 0 deletions
diff --git a/mm/rmap.c b/mm/rmap.c new file mode 100644 index 000000000..e578eb942 --- /dev/null +++ b/mm/rmap.c @@ -0,0 +1,1996 @@ +/* + * 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) + * i_pages 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) + * i_pages 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/sched/mm.h> +#include <linux/sched/task.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 <linux/memremap.h> +#include <linux/userfaultfd_k.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.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_CACHED; +} + +void __init anon_vma_init(void) +{ + anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma), + 0, SLAB_TYPESAFE_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_TYPESAFE_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; + + if (!tlb_ubc->flush_required) + return; + + arch_tlbbatch_flush(&tlb_ubc->arch); + tlb_ubc->flush_required = false; + tlb_ubc->writable = false; +} + +/* 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, bool writable) +{ + struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc; + + arch_tlbbatch_add_mm(&tlb_ubc->arch, mm); + tlb_ubc->flush_required = true; + + /* + * Ensure compiler does not re-order the setting of tlb_flush_batched + * before the PTE is cleared. + */ + barrier(); + mm->tlb_flush_batched = 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; +} + +/* + * Reclaim unmaps pages under the PTL but do not flush the TLB prior to + * releasing the PTL if TLB flushes are batched. It's possible for a parallel + * operation such as mprotect or munmap to race between reclaim unmapping + * the page and flushing the page. If this race occurs, it potentially allows + * access to data via a stale TLB entry. Tracking all mm's that have TLB + * batching in flight would be expensive during reclaim so instead track + * whether TLB batching occurred in the past and if so then do a flush here + * if required. This will cost one additional flush per reclaim cycle paid + * by the first operation at risk such as mprotect and mumap. + * + * This must be called under the PTL so that an access to tlb_flush_batched + * that is potentially a "reclaim vs mprotect/munmap/etc" race will synchronise + * via the PTL. + */ +void flush_tlb_batched_pending(struct mm_struct *mm) +{ + if (mm->tlb_flush_batched) { + flush_tlb_mm(mm); + + /* + * Do not allow the compiler to re-order the clearing of + * tlb_flush_batched before the tlb is flushed. + */ + barrier(); + mm->tlb_flush_batched = false; + } +} +#else +static void set_tlb_ubc_flush_pending(struct mm_struct *mm, 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) +{ + 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 (!vma->vm_file) { + return -EFAULT; + } else if (vma->vm_file->f_mapping != compound_head(page)->mapping) { + return -EFAULT; + } + + return vma_address(page, vma); +} + +pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address) +{ + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + pmd_t *pmd = NULL; + pmd_t pmde; + + pgd = pgd_offset(mm, address); + if (!pgd_present(*pgd)) + goto out; + + p4d = p4d_offset(pgd, address); + if (!p4d_present(*p4d)) + goto out; + + pud = pud_offset(p4d, 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; +} + +struct page_referenced_arg { + int mapcount; + int referenced; + unsigned long vm_flags; + struct mem_cgroup *memcg; +}; +/* + * arg: page_referenced_arg will be passed + */ +static bool 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 false; /* 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 false; /* To break the loop */ + + return true; +} + +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 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; + } + + rmap_walk(page, &rwc); + *vm_flags = pra.vm_flags; + + if (we_locked) + unlock_page(page); + + return pra.referenced; +} + +static bool page_mkclean_one(struct page *page, struct vm_area_struct *vma, + unsigned long address, void *arg) +{ + struct page_vma_mapped_walk pvmw = { + .page = page, + .vma = vma, + .address = address, + .flags = PVMW_SYNC, + }; + unsigned long start = address, end; + int *cleaned = arg; + + /* + * We have to assume the worse case ie pmd for invalidation. Note that + * the page can not be free from this function. + */ + end = vma_address_end(page, vma); + mmu_notifier_invalidate_range_start(vma->vm_mm, start, end); + + while (page_vma_mapped_walk(&pvmw)) { + unsigned long cstart; + int ret = 0; + + cstart = address = pvmw.address; + if (pvmw.pte) { + pte_t entry; + pte_t *pte = pvmw.pte; + + if (!pte_dirty(*pte) && !pte_write(*pte)) + continue; + + 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(vma->vm_mm, address, pte, entry); + ret = 1; + } else { +#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE + pmd_t *pmd = pvmw.pmd; + pmd_t entry; + + if (!pmd_dirty(*pmd) && !pmd_write(*pmd)) + continue; + + flush_cache_page(vma, address, page_to_pfn(page)); + entry = pmdp_invalidate(vma, address, pmd); + entry = pmd_wrprotect(entry); + entry = pmd_mkclean(entry); + set_pmd_at(vma->vm_mm, address, pmd, entry); + cstart &= PMD_MASK; + ret = 1; +#else + /* unexpected pmd-mapped page? */ + WARN_ON_ONCE(1); +#endif + } + + /* + * No need to call mmu_notifier_invalidate_range() as we are + * downgrading page table protection not changing it to point + * to a new page. + * + * See Documentation/vm/mmu_notifier.rst + */ + if (ret) + (*cleaned)++; + } + + mmu_notifier_invalidate_range_end(vma->vm_mm, start, end); + + return true; +} + +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 + * @compound: charge the page as compound or small page + * + * 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_lruvec_page_state(page, NR_FILE_MAPPED, nr); +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}_lruvec_page_state because + * these counters are not modified in interrupt context, and + * pte lock(a spinlock) is held, which implies preemption disabled. + */ + __mod_lruvec_page_state(page, NR_FILE_MAPPED, -nr); + + 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_unref_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. + */ +} + +/* + * @arg: enum ttu_flags will be passed to this argument + */ +static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, + unsigned long address, void *arg) +{ + struct mm_struct *mm = vma->vm_mm; + struct page_vma_mapped_walk pvmw = { + .page = page, + .vma = vma, + .address = address, + }; + pte_t pteval; + struct page *subpage; + bool ret = true; + unsigned long start = address, end; + enum ttu_flags flags = (enum ttu_flags)arg; + + /* + * When racing against e.g. zap_pte_range() on another cpu, + * in between its ptep_get_and_clear_full() and page_remove_rmap(), + * try_to_unmap() may return false when it is about to become true, + * if page table locking is skipped: use TTU_SYNC to wait for that. + */ + if (flags & TTU_SYNC) + pvmw.flags = PVMW_SYNC; + + /* munlock has nothing to gain from examining un-locked vmas */ + if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED)) + return true; + + if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION) && + is_zone_device_page(page) && !is_device_private_page(page)) + return true; + + if (flags & TTU_SPLIT_HUGE_PMD) { + split_huge_pmd_address(vma, address, + flags & TTU_SPLIT_FREEZE, page); + } + + /* + * For THP, we have to assume the worse case ie pmd for invalidation. + * For hugetlb, it could be much worse if we need to do pud + * invalidation in the case of pmd sharing. + * + * Note that the page can not be free in this function as call of + * try_to_unmap() must hold a reference on the page. + */ + end = PageKsm(page) ? + address + PAGE_SIZE : vma_address_end(page, vma); + if (PageHuge(page)) { + /* + * If sharing is possible, start and end will be adjusted + * accordingly. + */ + adjust_range_if_pmd_sharing_possible(vma, &start, &end); + } + mmu_notifier_invalidate_range_start(vma->vm_mm, start, end); + + while (page_vma_mapped_walk(&pvmw)) { +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION + /* PMD-mapped THP migration entry */ + if (!pvmw.pte && (flags & TTU_MIGRATION)) { + VM_BUG_ON_PAGE(PageHuge(page) || !PageTransCompound(page), page); + + set_pmd_migration_entry(&pvmw, page); + continue; + } +#endif + + /* + * 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 = false; + page_vma_mapped_walk_done(&pvmw); + break; + } + if (flags & TTU_MUNLOCK) + continue; + } + + /* Unexpected PMD-mapped THP? */ + VM_BUG_ON_PAGE(!pvmw.pte, page); + + subpage = page - page_to_pfn(page) + pte_pfn(*pvmw.pte); + address = pvmw.address; + + if (PageHuge(page)) { + if (huge_pmd_unshare(mm, &address, pvmw.pte)) { + /* + * huge_pmd_unshare unmapped an entire PMD + * page. There is no way of knowing exactly + * which PMDs may be cached for this mm, so + * we must flush them all. start/end were + * already adjusted above to cover this range. + */ + flush_cache_range(vma, start, end); + flush_tlb_range(vma, start, end); + mmu_notifier_invalidate_range(mm, start, end); + + /* + * The ref count of the PMD page was dropped + * which is part of the way map counting + * is done for shared PMDs. Return 'true' + * here. When there is no other sharing, + * huge_pmd_unshare returns false and we will + * unmap the actual page and drop map count + * to zero. + */ + page_vma_mapped_walk_done(&pvmw); + break; + } + } + + if (IS_ENABLED(CONFIG_MIGRATION) && + (flags & TTU_MIGRATION) && + is_zone_device_page(page)) { + swp_entry_t entry; + pte_t swp_pte; + + pteval = ptep_get_and_clear(mm, pvmw.address, pvmw.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, 0); + swp_pte = swp_entry_to_pte(entry); + if (pte_soft_dirty(pteval)) + swp_pte = pte_swp_mksoft_dirty(swp_pte); + set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte); + /* + * No need to invalidate here it will synchronize on + * against the special swap migration pte. + * + * The assignment to subpage above was computed from a + * swap PTE which results in an invalid pointer. + * Since only PAGE_SIZE pages can currently be + * migrated, just set it to page. This will need to be + * changed when hugepage migrations to device private + * memory are supported. + */ + subpage = page; + goto discard; + } + + if (!(flags & TTU_IGNORE_ACCESS)) { + if (ptep_clear_flush_young_notify(vma, address, + pvmw.pte)) { + ret = false; + page_vma_mapped_walk_done(&pvmw); + break; + } + } + + /* Nuke the page table entry. */ + flush_cache_page(vma, address, pte_pfn(*pvmw.pte)); + 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, pvmw.pte); + + set_tlb_ubc_flush_pending(mm, pte_dirty(pteval)); + } else { + pteval = ptep_clear_flush(vma, address, pvmw.pte); + } + + /* Move the dirty bit to the 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)) { + pteval = swp_entry_to_pte(make_hwpoison_entry(subpage)); + if (PageHuge(page)) { + int nr = 1 << compound_order(page); + hugetlb_count_sub(nr, mm); + set_huge_swap_pte_at(mm, address, + pvmw.pte, pteval, + vma_mmu_pagesize(vma)); + } else { + dec_mm_counter(mm, mm_counter(page)); + set_pte_at(mm, address, pvmw.pte, pteval); + } + + } else if (pte_unused(pteval) && !userfaultfd_armed(vma)) { + /* + * The guest indicated that the page content is of no + * interest anymore. Simply discard the pte, vmscan + * will take care of the rest. + * A future reference will then fault in a new zero + * page. When userfaultfd is active, we must not drop + * this page though, as its main user (postcopy + * migration) will not expect userfaults on already + * copied pages. + */ + dec_mm_counter(mm, mm_counter(page)); + /* We have to invalidate as we cleared the pte */ + mmu_notifier_invalidate_range(mm, address, + address + PAGE_SIZE); + } else if (IS_ENABLED(CONFIG_MIGRATION) && + (flags & (TTU_MIGRATION|TTU_SPLIT_FREEZE))) { + swp_entry_t entry; + pte_t swp_pte; + + if (arch_unmap_one(mm, vma, address, pteval) < 0) { + set_pte_at(mm, address, pvmw.pte, pteval); + ret = false; + page_vma_mapped_walk_done(&pvmw); + break; + } + + /* + * 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(subpage, + 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, pvmw.pte, swp_pte); + /* + * No need to invalidate here it will synchronize on + * against the special swap migration pte. + */ + } else if (PageAnon(page)) { + swp_entry_t entry = { .val = page_private(subpage) }; + pte_t swp_pte; + /* + * Store the swap location in the pte. + * See handle_pte_fault() ... + */ + if (unlikely(PageSwapBacked(page) != PageSwapCache(page))) { + WARN_ON_ONCE(1); + ret = false; + /* We have to invalidate as we cleared the pte */ + mmu_notifier_invalidate_range(mm, address, + address + PAGE_SIZE); + page_vma_mapped_walk_done(&pvmw); + break; + } + + /* MADV_FREE page check */ + if (!PageSwapBacked(page)) { + int ref_count, map_count; + + /* + * Synchronize with gup_pte_range(): + * - clear PTE; barrier; read refcount + * - inc refcount; barrier; read PTE + */ + smp_mb(); + + ref_count = page_ref_count(page); + map_count = page_mapcount(page); + + /* + * Order reads for page refcount and dirty flag + * (see comments in __remove_mapping()). + */ + smp_rmb(); + + /* + * The only page refs must be one from isolation + * plus the rmap(s) (dropped by discard:). + */ + if (ref_count == 1 + map_count && + !PageDirty(page)) { + /* Invalidate as we cleared the pte */ + mmu_notifier_invalidate_range(mm, + address, address + PAGE_SIZE); + dec_mm_counter(mm, MM_ANONPAGES); + goto discard; + } + + /* + * If the page was redirtied, it cannot be + * discarded. Remap the page to page table. + */ + set_pte_at(mm, address, pvmw.pte, pteval); + SetPageSwapBacked(page); + ret = false; + page_vma_mapped_walk_done(&pvmw); + break; + } + + if (swap_duplicate(entry) < 0) { + set_pte_at(mm, address, pvmw.pte, pteval); + ret = false; + page_vma_mapped_walk_done(&pvmw); + break; + } + if (arch_unmap_one(mm, vma, address, pteval) < 0) { + set_pte_at(mm, address, pvmw.pte, pteval); + ret = false; + page_vma_mapped_walk_done(&pvmw); + break; + } + 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, pvmw.pte, swp_pte); + /* Invalidate as we cleared the pte */ + mmu_notifier_invalidate_range(mm, address, + address + PAGE_SIZE); + } else { + /* + * This is a locked file-backed page, thus it cannot + * be removed from the page cache and replaced by a new + * page before mmu_notifier_invalidate_range_end, so no + * concurrent thread might update its page table to + * point at new page while a device still is using this + * page. + * + * See Documentation/vm/mmu_notifier.rst + */ + dec_mm_counter(mm, mm_counter_file(page)); + } +discard: + /* + * No need to call mmu_notifier_invalidate_range() it has be + * done above for all cases requiring it to happen under page + * table lock before mmu_notifier_invalidate_range_end() + * + * See Documentation/vm/mmu_notifier.rst + */ + page_remove_rmap(subpage, PageHuge(page)); + put_page(page); + } + + mmu_notifier_invalidate_range_end(vma->vm_mm, start, end); + + 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_not_mapped(struct page *page) +{ + return !page_mapped(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. + * + * If unmap is successful, return true. Otherwise, false. + */ +bool try_to_unmap(struct page *page, enum ttu_flags flags) +{ + struct rmap_walk_control rwc = { + .rmap_one = try_to_unmap_one, + .arg = (void *)flags, + .done = page_not_mapped, + .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|TTU_SPLIT_FREEZE)) + && !PageKsm(page) && PageAnon(page)) + rwc.invalid_vma = invalid_migration_vma; + + if (flags & TTU_RMAP_LOCKED) + rmap_walk_locked(page, &rwc); + else + rmap_walk(page, &rwc); + + /* + * When racing against e.g. zap_pte_range() on another cpu, + * in between its ptep_get_and_clear_full() and page_remove_rmap(), + * try_to_unmap() may return false when it is about to become true, + * if page table locking is skipped: use TTU_SYNC to wait for that. + */ + return !page_mapcount(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. + */ + +void try_to_munlock(struct page *page) +{ + struct rmap_walk_control rwc = { + .rmap_one = try_to_unmap_one, + .arg = (void *)TTU_MUNLOCK, + .done = page_not_mapped, + .anon_lock = page_lock_anon_vma_read, + + }; + + VM_BUG_ON_PAGE(!PageLocked(page) || PageLRU(page), page); + VM_BUG_ON_PAGE(PageCompound(page) && PageDoubleMap(page), page); + + rmap_walk(page, &rwc); +} + +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 void rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc, + bool locked) +{ + struct anon_vma *anon_vma; + pgoff_t pgoff_start, pgoff_end; + struct anon_vma_chain *avc; + + 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; + + pgoff_start = page_to_pgoff(page); + pgoff_end = pgoff_start + hpage_nr_pages(page) - 1; + anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, + pgoff_start, pgoff_end) { + struct vm_area_struct *vma = avc->vma; + unsigned long address = vma_address(page, vma); + + VM_BUG_ON_VMA(address == -EFAULT, vma); + cond_resched(); + + if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) + continue; + + if (!rwc->rmap_one(page, vma, address, rwc->arg)) + break; + if (rwc->done && rwc->done(page)) + break; + } + + if (!locked) + anon_vma_unlock_read(anon_vma); +} + +/* + * 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 void rmap_walk_file(struct page *page, struct rmap_walk_control *rwc, + bool locked) +{ + struct address_space *mapping = page_mapping(page); + pgoff_t pgoff_start, pgoff_end; + struct vm_area_struct *vma; + + /* + * 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; + + pgoff_start = page_to_pgoff(page); + pgoff_end = pgoff_start + hpage_nr_pages(page) - 1; + if (!locked) + i_mmap_lock_read(mapping); + vma_interval_tree_foreach(vma, &mapping->i_mmap, + pgoff_start, pgoff_end) { + unsigned long address = vma_address(page, vma); + + VM_BUG_ON_VMA(address == -EFAULT, vma); + cond_resched(); + + if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) + continue; + + if (!rwc->rmap_one(page, vma, address, rwc->arg)) + goto done; + if (rwc->done && rwc->done(page)) + goto done; + } + +done: + if (!locked) + i_mmap_unlock_read(mapping); +} + +void rmap_walk(struct page *page, struct rmap_walk_control *rwc) +{ + if (unlikely(PageKsm(page))) + rmap_walk_ksm(page, rwc); + else if (PageAnon(page)) + rmap_walk_anon(page, rwc, false); + else + rmap_walk_file(page, rwc, false); +} + +/* Like rmap_walk, but caller holds relevant rmap lock */ +void 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)) + rmap_walk_anon(page, rwc, true); + else + 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 */ |