diff options
Diffstat (limited to 'mm/rmap.c')
| -rw-r--r-- | mm/rmap.c | 3200 |
1 files changed, 3200 insertions, 0 deletions
diff --git a/mm/rmap.c b/mm/rmap.c new file mode 100644 index 000000000..1f72d279b --- /dev/null +++ b/mm/rmap.c @@ -0,0 +1,3200 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * mm/rmap.c - physical to virtual reverse mappings + * + * Copyright 2001, Rik van Riel <riel@conectiva.com.br> + * + * 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_rwsem (while writing or truncating, not reading or faulting) + * mm->mmap_lock + * mapping->invalidate_lock (in filemap_fault) + * folio_lock + * hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share, see hugetlbfs below) + * vma_start_write + * mapping->i_mmap_rwsem + * anon_vma->rwsem + * mm->page_table_lock or pte_lock + * swap_lock (in swap_duplicate, swap_info_get) + * mmlist_lock (in mmput, drain_mmlist and others) + * mapping->private_lock (in block_dirty_folio) + * i_pages lock (widely used) + * lruvec->lru_lock (in folio_lruvec_lock_irq) + * 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_mmap_rwsem (memory_failure, collect_procs_anon) + * ->tasklist_lock + * pte map lock + * + * hugetlbfs PageHuge() take locks in this order: + * hugetlb_fault_mutex (hugetlbfs specific page fault mutex) + * vma_lock (hugetlb specific lock for pmd_sharing) + * mapping->i_mmap_rwsem (also used for hugetlb pmd sharing) + * folio_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/leafops.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/huge_mm.h> +#include <linux/backing-dev.h> +#include <linux/page_idle.h> +#include <linux/memremap.h> +#include <linux/userfaultfd_k.h> +#include <linux/mm_inline.h> +#include <linux/oom.h> + +#include <asm/tlb.h> + +#define CREATE_TRACE_POINTS +#include <trace/events/migrate.h> + +#include "internal.h" +#include "swap.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->num_children = 0; + anon_vma->num_active_vmas = 0; + 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 folio_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 folio_lock_anon_vma_read(). This orders: + * + * folio_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_assign(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_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 folio_lock_anon_vma_read() + * and that may actually touch the rwsem 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. + */ +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; + + mmap_assert_locked(mm); + 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; + anon_vma->num_children++; /* self-parent link for new root */ + 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_assign(vma, avc, anon_vma); + anon_rmap_tree_insert(avc, anon_vma); + anon_vma->num_active_vmas++; + 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; +} + +static void check_anon_vma_clone(struct vm_area_struct *dst, + struct vm_area_struct *src, + enum vma_operation operation) +{ + /* The write lock must be held. */ + mmap_assert_write_locked(src->vm_mm); + /* If not a fork then must be on same mm. */ + VM_WARN_ON_ONCE(operation != VMA_OP_FORK && dst->vm_mm != src->vm_mm); + + /* If we have anything to do src->anon_vma must be provided. */ + VM_WARN_ON_ONCE(!src->anon_vma && !list_empty(&src->anon_vma_chain)); + VM_WARN_ON_ONCE(!src->anon_vma && dst->anon_vma); + /* We are establishing a new anon_vma_chain. */ + VM_WARN_ON_ONCE(!list_empty(&dst->anon_vma_chain)); + /* + * On fork, dst->anon_vma is set NULL (temporarily). Otherwise, anon_vma + * must be the same across dst and src. + */ + VM_WARN_ON_ONCE(dst->anon_vma && dst->anon_vma != src->anon_vma); + /* + * Essentially equivalent to above - if not a no-op, we should expect + * dst->anon_vma to be set for everything except a fork. + */ + VM_WARN_ON_ONCE(operation != VMA_OP_FORK && src->anon_vma && + !dst->anon_vma); + /* For the anon_vma to be compatible, it can only be singular. */ + VM_WARN_ON_ONCE(operation == VMA_OP_MERGE_UNFAULTED && + !list_is_singular(&src->anon_vma_chain)); +#ifdef CONFIG_PER_VMA_LOCK + /* Only merging an unfaulted VMA leaves the destination attached. */ + VM_WARN_ON_ONCE(operation != VMA_OP_MERGE_UNFAULTED && + vma_is_attached(dst)); +#endif +} + +static void maybe_reuse_anon_vma(struct vm_area_struct *dst, + struct anon_vma *anon_vma) +{ + /* If already populated, nothing to do.*/ + if (dst->anon_vma) + return; + + /* + * We reuse an anon_vma if any linking VMAs were unmapped and it has + * only a single child at most. + */ + if (anon_vma->num_active_vmas > 0) + return; + if (anon_vma->num_children > 1) + return; + + dst->anon_vma = anon_vma; + anon_vma->num_active_vmas++; +} + +static void cleanup_partial_anon_vmas(struct vm_area_struct *vma); + +/** + * anon_vma_clone - Establishes new anon_vma_chain objects in @dst linking to + * all of the anon_vma objects contained within @src anon_vma_chain's. + * @dst: The destination VMA with an empty anon_vma_chain. + * @src: The source VMA we wish to duplicate. + * @operation: The type of operation which resulted in the clone. + * + * This is the heart of the VMA side of the anon_vma implementation - we invoke + * this function whenever we need to set up a new VMA's anon_vma state. + * + * This is invoked for: + * + * - VMA Merge, but only when @dst is unfaulted and @src is faulted - meaning we + * clone @src into @dst. + * - VMA split. + * - VMA (m)remap. + * - Fork of faulted VMA. + * + * In all cases other than fork this is simply a duplication. Fork additionally + * adds a new active anon_vma. + * + * ONLY in the case of fork do we try to 'reuse' existing anon_vma's in an + * anon_vma hierarchy, reusing anon_vma's which have no VMA associated with them + * but do have a single child. This is to avoid waste of memory when repeatedly + * forking. + * + * Returns: 0 on success, -ENOMEM on failure. + */ +int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src, + enum vma_operation operation) +{ + struct anon_vma_chain *avc, *pavc; + struct anon_vma *active_anon_vma = src->anon_vma; + + check_anon_vma_clone(dst, src, operation); + + if (!active_anon_vma) + return 0; + + /* + * Allocate AVCs. We don't need an anon_vma lock for this as we + * are not updating the anon_vma rbtree nor are we changing + * anon_vma statistics. + * + * Either src, dst have the same mm for which we hold an exclusive mmap + * write lock, or we are forking and we hold it on src->vm_mm and dst is + * not yet accessible to other threads so there's no possibliity of the + * unlinked AVC's being observed yet. + */ + list_for_each_entry(pavc, &src->anon_vma_chain, same_vma) { + avc = anon_vma_chain_alloc(GFP_KERNEL); + if (!avc) + goto enomem_failure; + + anon_vma_chain_assign(dst, avc, pavc->anon_vma); + } + + /* + * Now link the anon_vma's back to the newly inserted AVCs. + * Note that all anon_vma's share the same root. + */ + anon_vma_lock_write(src->anon_vma); + list_for_each_entry_reverse(avc, &dst->anon_vma_chain, same_vma) { + struct anon_vma *anon_vma = avc->anon_vma; + + anon_rmap_tree_insert(avc, anon_vma); + if (operation == VMA_OP_FORK) + maybe_reuse_anon_vma(dst, anon_vma); + } + + if (operation != VMA_OP_FORK) + dst->anon_vma->num_active_vmas++; + + anon_vma_unlock_write(active_anon_vma); + return 0; + + enomem_failure: + cleanup_partial_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 rc; + + /* 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; + + anon_vma = anon_vma_alloc(); + if (!anon_vma) + return -ENOMEM; + avc = anon_vma_chain_alloc(GFP_KERNEL); + if (!avc) { + put_anon_vma(anon_vma); + return -ENOMEM; + } + + /* + * First, attach the new VMA to the parent VMA's anon_vmas, + * so rmap can find non-COWed pages in child processes. + */ + rc = anon_vma_clone(vma, pvma, VMA_OP_FORK); + /* An error arose or an existing anon_vma was reused, all done then. */ + if (rc || vma->anon_vma) { + put_anon_vma(anon_vma); + anon_vma_chain_free(avc); + return rc; + } + + /* + * OK no reuse, so add our own anon_vma. + * + * Since it is not linked anywhere we can safely manipulate anon_vma + * fields without a lock. + */ + + anon_vma->num_active_vmas = 1; + /* + * The root anon_vma's rwsem 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_chain_assign(vma, avc, anon_vma); + /* Now let rmap see it. */ + anon_vma_lock_write(anon_vma); + anon_rmap_tree_insert(avc, anon_vma); + anon_vma->parent->num_children++; + anon_vma_unlock_write(anon_vma); + + return 0; +} + +/* + * In the unfortunate case of anon_vma_clone() failing to allocate memory we + * have to clean things up. + * + * Since we allocate anon_vma_chain's before we insert them into the interval + * trees, we simply have to free up the AVC's and remove the entries from the + * VMA's anon_vma_chain. + */ +static void cleanup_partial_anon_vmas(struct vm_area_struct *vma) +{ + struct anon_vma_chain *avc, *next; + + list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { + list_del(&avc->same_vma); + anon_vma_chain_free(avc); + } + + /* + * The anon_vma assigned to this VMA is no longer valid, as we were not + * able to correctly clone AVC state. Avoid inconsistent anon_vma tree + * state by resetting. + */ + vma->anon_vma = NULL; +} + +/** + * unlink_anon_vmas() - remove all links between a VMA and anon_vma's, freeing + * anon_vma_chain objects. + * @vma: The VMA whose links to anon_vma objects is to be severed. + * + * As part of the process anon_vma_chain's are freed, + * anon_vma->num_children,num_active_vmas is updated as required and, if the + * relevant anon_vma references no further VMAs, its reference count is + * decremented. + */ +void unlink_anon_vmas(struct vm_area_struct *vma) +{ + struct anon_vma_chain *avc, *next; + struct anon_vma *active_anon_vma = vma->anon_vma; + + /* Always hold mmap lock, read-lock on unmap possibly. */ + mmap_assert_locked(vma->vm_mm); + + /* Unfaulted is a no-op. */ + if (!active_anon_vma) { + VM_WARN_ON_ONCE(!list_empty(&vma->anon_vma_chain)); + return; + } + + anon_vma_lock_write(active_anon_vma); + + /* + * 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; + + anon_rmap_tree_remove(avc, anon_vma); + + /* + * 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->num_children--; + continue; + } + + list_del(&avc->same_vma); + anon_vma_chain_free(avc); + } + + active_anon_vma->num_active_vmas--; + /* + * vma would still be needed after unlink, and anon_vma will be prepared + * when handle fault. + */ + vma->anon_vma = NULL; + anon_vma_unlock_write(active_anon_vma); + + + /* + * 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->num_children); + VM_WARN_ON(anon_vma->num_active_vmas); + 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 folio_remove_rmap_*() + * the best this function can do is return a refcount increased 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 folio_mapped() [ hence all those folio_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 SLAB_TYPESAFE_BY_RCU and we know from + * folio_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. + * + * NOTE: the caller should hold folio lock when calling this. + */ +struct anon_vma *folio_get_anon_vma(const struct folio *folio) +{ + struct anon_vma *anon_vma = NULL; + unsigned long anon_mapping; + + VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio); + + rcu_read_lock(); + anon_mapping = (unsigned long)READ_ONCE(folio->mapping); + if ((anon_mapping & FOLIO_MAPPING_FLAGS) != FOLIO_MAPPING_ANON) + goto out; + if (!folio_mapped(folio)) + goto out; + + anon_vma = (struct anon_vma *) (anon_mapping - FOLIO_MAPPING_ANON); + if (!atomic_inc_not_zero(&anon_vma->refcount)) { + anon_vma = NULL; + goto out; + } + + /* + * If this folio 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 (!folio_mapped(folio)) { + rcu_read_unlock(); + put_anon_vma(anon_vma); + return NULL; + } +out: + rcu_read_unlock(); + + return anon_vma; +} + +/* + * Similar to folio_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 folio_get_anon_vma() and then block on the mutex + * on !rwc->try_lock case. + */ +struct anon_vma *folio_lock_anon_vma_read(const struct folio *folio, + struct rmap_walk_control *rwc) +{ + struct anon_vma *anon_vma = NULL; + struct anon_vma *root_anon_vma; + unsigned long anon_mapping; + + VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio); + + rcu_read_lock(); + anon_mapping = (unsigned long)READ_ONCE(folio->mapping); + if ((anon_mapping & FOLIO_MAPPING_FLAGS) != FOLIO_MAPPING_ANON) + goto out; + if (!folio_mapped(folio)) + goto out; + + anon_vma = (struct anon_vma *) (anon_mapping - FOLIO_MAPPING_ANON); + root_anon_vma = READ_ONCE(anon_vma->root); + if (down_read_trylock(&root_anon_vma->rwsem)) { + /* + * If the folio 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 (!folio_mapped(folio)) { + up_read(&root_anon_vma->rwsem); + anon_vma = NULL; + } + goto out; + } + + if (rwc && rwc->try_lock) { + anon_vma = NULL; + rwc->contended = true; + goto out; + } + + /* trylock failed, we got to sleep */ + if (!atomic_inc_not_zero(&anon_vma->refcount)) { + anon_vma = NULL; + goto out; + } + + if (!folio_mapped(folio)) { + 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; +} + +#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(); +} + +/* + * Bits 0-14 of mm->tlb_flush_batched record pending generations. + * Bits 16-30 of mm->tlb_flush_batched bit record flushed generations. + */ +#define TLB_FLUSH_BATCH_FLUSHED_SHIFT 16 +#define TLB_FLUSH_BATCH_PENDING_MASK \ + ((1 << (TLB_FLUSH_BATCH_FLUSHED_SHIFT - 1)) - 1) +#define TLB_FLUSH_BATCH_PENDING_LARGE \ + (TLB_FLUSH_BATCH_PENDING_MASK / 2) + +static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval, + unsigned long start, unsigned long end) +{ + struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc; + int batch; + bool writable = pte_dirty(pteval); + + if (!pte_accessible(mm, pteval)) + return; + + arch_tlbbatch_add_pending(&tlb_ubc->arch, mm, start, end); + tlb_ubc->flush_required = true; + + /* + * Ensure compiler does not re-order the setting of tlb_flush_batched + * before the PTE is cleared. + */ + barrier(); + batch = atomic_read(&mm->tlb_flush_batched); +retry: + if ((batch & TLB_FLUSH_BATCH_PENDING_MASK) > TLB_FLUSH_BATCH_PENDING_LARGE) { + /* + * Prevent `pending' from catching up with `flushed' because of + * overflow. Reset `pending' and `flushed' to be 1 and 0 if + * `pending' becomes large. + */ + if (!atomic_try_cmpxchg(&mm->tlb_flush_batched, &batch, 1)) + goto retry; + } else { + atomic_inc(&mm->tlb_flush_batched); + } + + /* + * 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) +{ + if (!(flags & TTU_BATCH_FLUSH)) + return false; + + return arch_tlbbatch_should_defer(mm); +} + +/* + * 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) +{ + int batch = atomic_read(&mm->tlb_flush_batched); + int pending = batch & TLB_FLUSH_BATCH_PENDING_MASK; + int flushed = batch >> TLB_FLUSH_BATCH_FLUSHED_SHIFT; + + if (pending != flushed) { + flush_tlb_mm(mm); + /* + * If the new TLB flushing is pending during flushing, leave + * mm->tlb_flush_batched as is, to avoid losing flushing. + */ + atomic_cmpxchg(&mm->tlb_flush_batched, batch, + pending | (pending << TLB_FLUSH_BATCH_FLUSHED_SHIFT)); + } +} +#else +static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval, + unsigned long start, unsigned long end) +{ +} + +static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags) +{ + return false; +} +#endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */ + +/** + * page_address_in_vma - The virtual address of a page in this VMA. + * @folio: The folio containing the page. + * @page: The page within the folio. + * @vma: The VMA we need to know the address in. + * + * Calculates the user virtual address of this page in the specified VMA. + * It is the caller's responsibility to check the page is actually + * within the VMA. There may not currently be a PTE pointing at this + * page, but if a page fault occurs at this address, this is the page + * which will be accessed. + * + * Context: Caller should hold a reference to the folio. Caller should + * hold a lock (eg the i_mmap_lock or the mmap_lock) which keeps the + * VMA from being altered. + * + * Return: The virtual address corresponding to this page in the VMA. + */ +unsigned long page_address_in_vma(const struct folio *folio, + const struct page *page, const struct vm_area_struct *vma) +{ + if (folio_test_anon(folio)) { + struct anon_vma *anon_vma = folio_anon_vma(folio); + /* + * 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 || !anon_vma || + vma->anon_vma->root != anon_vma->root) + return -EFAULT; + } else if (!vma->vm_file) { + return -EFAULT; + } else if (vma->vm_file->f_mapping != folio->mapping) { + return -EFAULT; + } + + /* KSM folios don't reach here because of the !anon_vma check */ + return vma_address(vma, page_pgoff(folio, page), 1); +} + +/* + * Returns the actual pmd_t* where we expect 'address' to be mapped from, or + * NULL if it doesn't exist. No guarantees / checks on what the pmd_t* + * represents. + */ +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; + + 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); +out: + return pmd; +} + +struct folio_referenced_arg { + int mapcount; + int referenced; + vm_flags_t vm_flags; + struct mem_cgroup *memcg; +}; + +/* + * arg: folio_referenced_arg will be passed + */ +static bool folio_referenced_one(struct folio *folio, + struct vm_area_struct *vma, unsigned long address, void *arg) +{ + struct folio_referenced_arg *pra = arg; + DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0); + int ptes = 0, referenced = 0; + unsigned int nr; + + while (page_vma_mapped_walk(&pvmw)) { + address = pvmw.address; + nr = 1; + + if (vma->vm_flags & VM_LOCKED) { + ptes++; + pra->mapcount--; + + /* Only mlock fully mapped pages */ + if (pvmw.pte && ptes != pvmw.nr_pages) + continue; + + /* + * All PTEs must be protected by page table lock in + * order to mlock the page. + * + * If page table boundary has been cross, current ptl + * only protect part of ptes. + */ + if (pvmw.flags & PVMW_PGTABLE_CROSSED) + continue; + + /* Restore the mlock which got missed */ + mlock_vma_folio(folio, vma); + page_vma_mapped_walk_done(&pvmw); + pra->vm_flags |= VM_LOCKED; + return false; /* To break the loop */ + } + + /* + * Skip the non-shared swapbacked folio mapped solely by + * the exiting or OOM-reaped process. This avoids redundant + * swap-out followed by an immediate unmap. + */ + if ((!atomic_read(&vma->vm_mm->mm_users) || + check_stable_address_space(vma->vm_mm)) && + folio_test_anon(folio) && folio_test_swapbacked(folio) && + !folio_maybe_mapped_shared(folio)) { + pra->referenced = -1; + page_vma_mapped_walk_done(&pvmw); + return false; + } + + if (pvmw.pte && folio_test_large(folio)) { + const unsigned long end_addr = pmd_addr_end(address, vma->vm_end); + const unsigned int max_nr = (end_addr - address) >> PAGE_SHIFT; + pte_t pteval = ptep_get(pvmw.pte); + + nr = folio_pte_batch(folio, pvmw.pte, pteval, max_nr); + } + + /* + * When LRU is switching, we don’t know where the surrounding folios + * are. —they could be on active/inactive lists or on MGLRU. So the + * simplest approach is to disable this look-around optimization. + */ + if (lru_gen_enabled() && !lru_gen_switching() && pvmw.pte) { + if (lru_gen_look_around(&pvmw, nr)) + referenced++; + } else if (pvmw.pte) { + if (clear_flush_young_ptes_notify(vma, address, pvmw.pte, nr)) + referenced++; + } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { + if (pmdp_clear_flush_young_notify(vma, address, + pvmw.pmd)) + referenced++; + } else { + /* unexpected pmd-mapped folio? */ + WARN_ON_ONCE(1); + } + + ptes += nr; + pra->mapcount -= nr; + /* + * If we are sure that we batched the entire folio, + * we can just optimize and stop right here. + */ + if (ptes == pvmw.nr_pages) { + page_vma_mapped_walk_done(&pvmw); + break; + } + + /* Skip the batched PTEs */ + pvmw.pte += nr - 1; + pvmw.address += (nr - 1) * PAGE_SIZE; + } + + if (referenced) + folio_clear_idle(folio); + if (folio_test_clear_young(folio)) + referenced++; + + if (referenced) { + pra->referenced++; + pra->vm_flags |= vma->vm_flags & ~VM_LOCKED; + } + + if (!pra->mapcount) + return false; /* To break the loop */ + + return true; +} + +static bool invalid_folio_referenced_vma(struct vm_area_struct *vma, void *arg) +{ + struct folio_referenced_arg *pra = arg; + struct mem_cgroup *memcg = pra->memcg; + + /* + * Ignore references from this mapping if it has no recency. If the + * folio has been used in another mapping, we will catch it; if this + * other mapping is already gone, the unmap path will have set the + * referenced flag or activated the folio in zap_pte_range(). + */ + if (!vma_has_recency(vma)) + return true; + + /* + * If we are reclaiming on behalf of a cgroup, skip counting on behalf + * of references from different cgroups. + */ + if (memcg && !mm_match_cgroup(vma->vm_mm, memcg)) + return true; + + return false; +} + +/** + * folio_referenced() - Test if the folio was referenced. + * @folio: The folio to test. + * @is_locked: Caller holds lock on the folio. + * @memcg: target memory cgroup + * @vm_flags: A combination of all the vma->vm_flags which referenced the folio. + * + * Quick test_and_clear_referenced for all mappings of a folio, + * + * Return: The number of mappings which referenced the folio. Return -1 if + * the function bailed out due to rmap lock contention. + */ +int folio_referenced(struct folio *folio, int is_locked, + struct mem_cgroup *memcg, vm_flags_t *vm_flags) +{ + bool we_locked = false; + struct folio_referenced_arg pra = { + .mapcount = folio_mapcount(folio), + .memcg = memcg, + }; + struct rmap_walk_control rwc = { + .rmap_one = folio_referenced_one, + .arg = (void *)&pra, + .anon_lock = folio_lock_anon_vma_read, + .try_lock = true, + .invalid_vma = invalid_folio_referenced_vma, + }; + + VM_WARN_ON_ONCE_FOLIO(folio_is_zone_device(folio), folio); + *vm_flags = 0; + if (!pra.mapcount) + return 0; + + if (!folio_raw_mapping(folio)) + return 0; + + if (!is_locked) { + we_locked = folio_trylock(folio); + if (!we_locked) + return 1; + } + + rmap_walk(folio, &rwc); + *vm_flags = pra.vm_flags; + + if (we_locked) + folio_unlock(folio); + + return rwc.contended ? -1 : pra.referenced; +} + +static int page_vma_mkclean_one(struct page_vma_mapped_walk *pvmw) +{ + int cleaned = 0; + struct vm_area_struct *vma = pvmw->vma; + struct mmu_notifier_range range; + unsigned long address = pvmw->address; + + /* + * We have to assume the worse case ie pmd for invalidation. Note that + * the folio can not be freed from this function. + */ + mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_PAGE, 0, + vma->vm_mm, address, vma_address_end(pvmw)); + mmu_notifier_invalidate_range_start(&range); + + while (page_vma_mapped_walk(pvmw)) { + int ret = 0; + + address = pvmw->address; + if (pvmw->pte) { + pte_t *pte = pvmw->pte; + pte_t entry = ptep_get(pte); + + /* + * PFN swap PTEs, such as device-exclusive ones, that + * actually map pages are clean and not writable from a + * CPU perspective. The MMU notifier takes care of any + * device aspects. + */ + if (!pte_present(entry)) + continue; + if (!pte_dirty(entry) && !pte_write(entry)) + continue; + + flush_cache_page(vma, address, pte_pfn(entry)); + 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_HUGEPAGE + pmd_t *pmd = pvmw->pmd; + pmd_t entry = pmdp_get(pmd); + + /* + * Please see the comment above (!pte_present). + * A non present PMD is not writable from a CPU + * perspective. + */ + if (!pmd_present(entry)) + continue; + if (!pmd_dirty(entry) && !pmd_write(entry)) + continue; + + flush_cache_range(vma, address, + address + HPAGE_PMD_SIZE); + entry = pmdp_invalidate(vma, address, pmd); + entry = pmd_wrprotect(entry); + entry = pmd_mkclean(entry); + set_pmd_at(vma->vm_mm, address, pmd, entry); + ret = 1; +#else + /* unexpected pmd-mapped folio? */ + WARN_ON_ONCE(1); +#endif + } + + if (ret) + cleaned++; + } + + mmu_notifier_invalidate_range_end(&range); + + return cleaned; +} + +static bool page_mkclean_one(struct folio *folio, struct vm_area_struct *vma, + unsigned long address, void *arg) +{ + DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, PVMW_SYNC); + int *cleaned = arg; + + *cleaned += page_vma_mkclean_one(&pvmw); + + 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 folio_mkclean(struct folio *folio) +{ + 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(!folio_test_locked(folio)); + + if (!folio_mapped(folio)) + return 0; + + mapping = folio_mapping(folio); + if (!mapping) + return 0; + + rmap_walk(folio, &rwc); + + return cleaned; +} +EXPORT_SYMBOL_GPL(folio_mkclean); + +struct wrprotect_file_state { + int cleaned; + pgoff_t pgoff; + unsigned long pfn; + unsigned long nr_pages; +}; + +static bool mapping_wrprotect_range_one(struct folio *folio, + struct vm_area_struct *vma, unsigned long address, void *arg) +{ + struct wrprotect_file_state *state = (struct wrprotect_file_state *)arg; + struct page_vma_mapped_walk pvmw = { + .pfn = state->pfn, + .nr_pages = state->nr_pages, + .pgoff = state->pgoff, + .vma = vma, + .address = address, + .flags = PVMW_SYNC, + }; + + state->cleaned += page_vma_mkclean_one(&pvmw); + + return true; +} + +static void __rmap_walk_file(struct folio *folio, struct address_space *mapping, + pgoff_t pgoff_start, unsigned long nr_pages, + struct rmap_walk_control *rwc, bool locked); + +/** + * mapping_wrprotect_range() - Write-protect all mappings in a specified range. + * + * @mapping: The mapping whose reverse mapping should be traversed. + * @pgoff: The page offset at which @pfn is mapped within @mapping. + * @pfn: The PFN of the page mapped in @mapping at @pgoff. + * @nr_pages: The number of physically contiguous base pages spanned. + * + * Traverses the reverse mapping, finding all VMAs which contain a shared + * mapping of the pages in the specified range in @mapping, and write-protects + * them (that is, updates the page tables to mark the mappings read-only such + * that a write protection fault arises when the mappings are written to). + * + * The @pfn value need not refer to a folio, but rather can reference a kernel + * allocation which is mapped into userland. We therefore do not require that + * the page maps to a folio with a valid mapping or index field, rather the + * caller specifies these in @mapping and @pgoff. + * + * Return: the number of write-protected PTEs, or an error. + */ +int mapping_wrprotect_range(struct address_space *mapping, pgoff_t pgoff, + unsigned long pfn, unsigned long nr_pages) +{ + struct wrprotect_file_state state = { + .cleaned = 0, + .pgoff = pgoff, + .pfn = pfn, + .nr_pages = nr_pages, + }; + struct rmap_walk_control rwc = { + .arg = (void *)&state, + .rmap_one = mapping_wrprotect_range_one, + .invalid_vma = invalid_mkclean_vma, + }; + + if (!mapping) + return 0; + + __rmap_walk_file(/* folio = */NULL, mapping, pgoff, nr_pages, &rwc, + /* locked = */false); + + return state.cleaned; +} +EXPORT_SYMBOL_GPL(mapping_wrprotect_range); + +/** + * pfn_mkclean_range - Cleans the PTEs (including PMDs) mapped with range of + * [@pfn, @pfn + @nr_pages) at the specific offset (@pgoff) + * within the @vma of shared mappings. And since clean PTEs + * should also be readonly, write protects them too. + * @pfn: start pfn. + * @nr_pages: number of physically contiguous pages srarting with @pfn. + * @pgoff: page offset that the @pfn mapped with. + * @vma: vma that @pfn mapped within. + * + * Returns the number of cleaned PTEs (including PMDs). + */ +int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff, + struct vm_area_struct *vma) +{ + struct page_vma_mapped_walk pvmw = { + .pfn = pfn, + .nr_pages = nr_pages, + .pgoff = pgoff, + .vma = vma, + .flags = PVMW_SYNC, + }; + + if (invalid_mkclean_vma(vma, NULL)) + return 0; + + pvmw.address = vma_address(vma, pgoff, nr_pages); + VM_BUG_ON_VMA(pvmw.address == -EFAULT, vma); + + return page_vma_mkclean_one(&pvmw); +} + +static void __folio_mod_stat(struct folio *folio, int nr, int nr_pmdmapped) +{ + int idx; + + if (nr) { + idx = folio_test_anon(folio) ? NR_ANON_MAPPED : NR_FILE_MAPPED; + lruvec_stat_mod_folio(folio, idx, nr); + } + if (nr_pmdmapped) { + if (folio_test_anon(folio)) { + idx = NR_ANON_THPS; + lruvec_stat_mod_folio(folio, idx, nr_pmdmapped); + } else { + /* NR_*_PMDMAPPED are not maintained per-memcg */ + idx = folio_test_swapbacked(folio) ? + NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED; + __mod_node_page_state(folio_pgdat(folio), idx, + nr_pmdmapped); + } + } +} + +static __always_inline void __folio_add_rmap(struct folio *folio, + struct page *page, int nr_pages, struct vm_area_struct *vma, + enum pgtable_level level) +{ + atomic_t *mapped = &folio->_nr_pages_mapped; + const int orig_nr_pages = nr_pages; + int first = 0, nr = 0, nr_pmdmapped = 0; + + __folio_rmap_sanity_checks(folio, page, nr_pages, level); + + switch (level) { + case PGTABLE_LEVEL_PTE: + if (!folio_test_large(folio)) { + nr = atomic_inc_and_test(&folio->_mapcount); + break; + } + + if (IS_ENABLED(CONFIG_NO_PAGE_MAPCOUNT)) { + nr = folio_add_return_large_mapcount(folio, orig_nr_pages, vma); + if (nr == orig_nr_pages) + /* Was completely unmapped. */ + nr = folio_large_nr_pages(folio); + else + nr = 0; + break; + } + + do { + first += atomic_inc_and_test(&page->_mapcount); + } while (page++, --nr_pages > 0); + + if (first && + atomic_add_return_relaxed(first, mapped) < ENTIRELY_MAPPED) + nr = first; + + folio_add_large_mapcount(folio, orig_nr_pages, vma); + break; + case PGTABLE_LEVEL_PMD: + case PGTABLE_LEVEL_PUD: + first = atomic_inc_and_test(&folio->_entire_mapcount); + if (IS_ENABLED(CONFIG_NO_PAGE_MAPCOUNT)) { + if (level == PGTABLE_LEVEL_PMD && first) + nr_pmdmapped = folio_large_nr_pages(folio); + nr = folio_inc_return_large_mapcount(folio, vma); + if (nr == 1) + /* Was completely unmapped. */ + nr = folio_large_nr_pages(folio); + else + nr = 0; + break; + } + + if (first) { + nr = atomic_add_return_relaxed(ENTIRELY_MAPPED, mapped); + if (likely(nr < ENTIRELY_MAPPED + ENTIRELY_MAPPED)) { + nr_pages = folio_large_nr_pages(folio); + /* + * We only track PMD mappings of PMD-sized + * folios separately. + */ + if (level == PGTABLE_LEVEL_PMD) + nr_pmdmapped = nr_pages; + nr = nr_pages - (nr & FOLIO_PAGES_MAPPED); + /* Raced ahead of a remove and another add? */ + if (unlikely(nr < 0)) + nr = 0; + } else { + /* Raced ahead of a remove of ENTIRELY_MAPPED */ + nr = 0; + } + } + folio_inc_large_mapcount(folio, vma); + break; + default: + BUILD_BUG(); + } + __folio_mod_stat(folio, nr, nr_pmdmapped); +} + +/** + * folio_move_anon_rmap - move a folio to our anon_vma + * @folio: The folio to move to our anon_vma + * @vma: The vma the folio belongs to + * + * When a folio belongs exclusively to one process after a COW event, + * that folio 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 folio_move_anon_rmap(struct folio *folio, struct vm_area_struct *vma) +{ + void *anon_vma = vma->anon_vma; + + VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); + VM_BUG_ON_VMA(!anon_vma, vma); + + anon_vma += FOLIO_MAPPING_ANON; + /* + * Ensure that anon_vma and the FOLIO_MAPPING_ANON bit are written + * simultaneously, so a concurrent reader (eg folio_referenced()'s + * folio_test_anon()) will not see one without the other. + */ + WRITE_ONCE(folio->mapping, anon_vma); +} + +/** + * __folio_set_anon - set up a new anonymous rmap for a folio + * @folio: The folio to set up the new anonymous rmap for. + * @vma: VM area to add the folio to. + * @address: User virtual address of the mapping + * @exclusive: Whether the folio is exclusive to the process. + */ +static void __folio_set_anon(struct folio *folio, struct vm_area_struct *vma, + unsigned long address, bool exclusive) +{ + struct anon_vma *anon_vma = vma->anon_vma; + + BUG_ON(!anon_vma); + + /* + * If the folio isn't exclusive to this vma, we must use the _oldest_ + * possible anon_vma for the folio mapping! + */ + if (!exclusive) + anon_vma = anon_vma->root; + + /* + * page_idle does a lockless/optimistic rmap scan on folio->mapping. + * Make sure the compiler doesn't split the stores of anon_vma and + * the FOLIO_MAPPING_ANON type identifier, otherwise the rmap code + * could mistake the mapping for a struct address_space and crash. + */ + anon_vma = (void *) anon_vma + FOLIO_MAPPING_ANON; + WRITE_ONCE(folio->mapping, (struct address_space *) anon_vma); + folio->index = linear_page_index(vma, address); +} + +/** + * __page_check_anon_rmap - sanity check anonymous rmap addition + * @folio: The folio containing @page. + * @page: the page to check the mapping of + * @vma: the vm area in which the mapping is added + * @address: the user virtual address mapped + */ +static void __page_check_anon_rmap(const struct folio *folio, + const struct page *page, struct vm_area_struct *vma, + unsigned long address) +{ + /* + * The page's anon-rmap details (mapping and index) are guaranteed to + * be set up correctly at this point. + * + * We have exclusion against folio_add_anon_rmap_*() because the caller + * always holds the page locked. + * + * We have exclusion against folio_add_new_anon_rmap because those pages + * are initially only visible via the pagetables, and the pte is locked + * over the call to folio_add_new_anon_rmap. + */ + VM_BUG_ON_FOLIO(folio_anon_vma(folio)->root != vma->anon_vma->root, + folio); + VM_BUG_ON_PAGE(page_pgoff(folio, page) != linear_page_index(vma, address), + page); +} + +static __always_inline void __folio_add_anon_rmap(struct folio *folio, + struct page *page, int nr_pages, struct vm_area_struct *vma, + unsigned long address, rmap_t flags, enum pgtable_level level) +{ + int i; + + VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); + + __folio_add_rmap(folio, page, nr_pages, vma, level); + + if (likely(!folio_test_ksm(folio))) + __page_check_anon_rmap(folio, page, vma, address); + + if (flags & RMAP_EXCLUSIVE) { + switch (level) { + case PGTABLE_LEVEL_PTE: + for (i = 0; i < nr_pages; i++) + SetPageAnonExclusive(page + i); + break; + case PGTABLE_LEVEL_PMD: + SetPageAnonExclusive(page); + break; + case PGTABLE_LEVEL_PUD: + /* + * Keep the compiler happy, we don't support anonymous + * PUD mappings. + */ + WARN_ON_ONCE(1); + break; + default: + BUILD_BUG(); + } + } + + VM_WARN_ON_FOLIO(!folio_test_large(folio) && PageAnonExclusive(page) && + atomic_read(&folio->_mapcount) > 0, folio); + for (i = 0; i < nr_pages; i++) { + struct page *cur_page = page + i; + + VM_WARN_ON_FOLIO(folio_test_large(folio) && + folio_entire_mapcount(folio) > 1 && + PageAnonExclusive(cur_page), folio); + if (IS_ENABLED(CONFIG_NO_PAGE_MAPCOUNT)) + continue; + + /* + * While PTE-mapping a THP we have a PMD and a PTE + * mapping. + */ + VM_WARN_ON_FOLIO(atomic_read(&cur_page->_mapcount) > 0 && + PageAnonExclusive(cur_page), folio); + } + + /* + * Only mlock it if the folio is fully mapped to the VMA. + * + * Partially mapped folios can be split on reclaim and part outside + * of mlocked VMA can be evicted or freed. + */ + if (folio_nr_pages(folio) == nr_pages) + mlock_vma_folio(folio, vma); +} + +/** + * folio_add_anon_rmap_ptes - add PTE mappings to a page range of an anon folio + * @folio: The folio to add the mappings to + * @page: The first page to add + * @nr_pages: The number of pages which will be mapped + * @vma: The vm area in which the mappings are added + * @address: The user virtual address of the first page to map + * @flags: The rmap flags + * + * The page range of folio is defined by [first_page, first_page + nr_pages) + * + * The caller needs to hold the page table lock, and the page must be locked in + * the anon_vma case: to serialize mapping,index checking after setting, + * and to ensure that an anon folio is not being upgraded racily to a KSM folio + * (but KSM folios are never downgraded). + */ +void folio_add_anon_rmap_ptes(struct folio *folio, struct page *page, + int nr_pages, struct vm_area_struct *vma, unsigned long address, + rmap_t flags) +{ + __folio_add_anon_rmap(folio, page, nr_pages, vma, address, flags, + PGTABLE_LEVEL_PTE); +} + +/** + * folio_add_anon_rmap_pmd - add a PMD mapping to a page range of an anon folio + * @folio: The folio to add the mapping to + * @page: The first page to add + * @vma: The vm area in which the mapping is added + * @address: The user virtual address of the first page to map + * @flags: The rmap flags + * + * The page range of folio is defined by [first_page, first_page + HPAGE_PMD_NR) + * + * The caller needs to hold the page table lock, and the page must be locked in + * the anon_vma case: to serialize mapping,index checking after setting. + */ +void folio_add_anon_rmap_pmd(struct folio *folio, struct page *page, + struct vm_area_struct *vma, unsigned long address, rmap_t flags) +{ +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + __folio_add_anon_rmap(folio, page, HPAGE_PMD_NR, vma, address, flags, + PGTABLE_LEVEL_PMD); +#else + WARN_ON_ONCE(true); +#endif +} + +/** + * folio_add_new_anon_rmap - Add mapping to a new anonymous folio. + * @folio: The folio to add the mapping to. + * @vma: the vm area in which the mapping is added + * @address: the user virtual address mapped + * @flags: The rmap flags + * + * Like folio_add_anon_rmap_*() but must only be called on *new* folios. + * This means the inc-and-test can be bypassed. + * The folio doesn't necessarily need to be locked while it's exclusive + * unless two threads map it concurrently. However, the folio must be + * locked if it's shared. + * + * If the folio is pmd-mappable, it is accounted as a THP. + */ +void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma, + unsigned long address, rmap_t flags) +{ + const bool exclusive = flags & RMAP_EXCLUSIVE; + int nr = 1, nr_pmdmapped = 0; + + VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio); + VM_WARN_ON_FOLIO(!exclusive && !folio_test_locked(folio), folio); + + /* + * VM_DROPPABLE mappings don't swap; instead they're just dropped when + * under memory pressure. + */ + if (!folio_test_swapbacked(folio) && !(vma->vm_flags & VM_DROPPABLE)) + __folio_set_swapbacked(folio); + __folio_set_anon(folio, vma, address, exclusive); + + if (likely(!folio_test_large(folio))) { + /* increment count (starts at -1) */ + atomic_set(&folio->_mapcount, 0); + if (exclusive) + SetPageAnonExclusive(&folio->page); + } else if (!folio_test_pmd_mappable(folio)) { + int i; + + nr = folio_large_nr_pages(folio); + for (i = 0; i < nr; i++) { + struct page *page = folio_page(folio, i); + + if (IS_ENABLED(CONFIG_PAGE_MAPCOUNT)) + /* increment count (starts at -1) */ + atomic_set(&page->_mapcount, 0); + if (exclusive) + SetPageAnonExclusive(page); + } + + folio_set_large_mapcount(folio, nr, vma); + if (IS_ENABLED(CONFIG_PAGE_MAPCOUNT)) + atomic_set(&folio->_nr_pages_mapped, nr); + } else { + nr = folio_large_nr_pages(folio); + /* increment count (starts at -1) */ + atomic_set(&folio->_entire_mapcount, 0); + folio_set_large_mapcount(folio, 1, vma); + if (IS_ENABLED(CONFIG_PAGE_MAPCOUNT)) + atomic_set(&folio->_nr_pages_mapped, ENTIRELY_MAPPED); + if (exclusive) + SetPageAnonExclusive(&folio->page); + nr_pmdmapped = nr; + } + + VM_WARN_ON_ONCE(address < vma->vm_start || + address + (nr << PAGE_SHIFT) > vma->vm_end); + + __folio_mod_stat(folio, nr, nr_pmdmapped); + mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_ANON, 1); +} + +static __always_inline void __folio_add_file_rmap(struct folio *folio, + struct page *page, int nr_pages, struct vm_area_struct *vma, + enum pgtable_level level) +{ + VM_WARN_ON_FOLIO(folio_test_anon(folio), folio); + + __folio_add_rmap(folio, page, nr_pages, vma, level); + + /* + * Only mlock it if the folio is fully mapped to the VMA. + * + * Partially mapped folios can be split on reclaim and part outside + * of mlocked VMA can be evicted or freed. + */ + if (folio_nr_pages(folio) == nr_pages) + mlock_vma_folio(folio, vma); +} + +/** + * folio_add_file_rmap_ptes - add PTE mappings to a page range of a folio + * @folio: The folio to add the mappings to + * @page: The first page to add + * @nr_pages: The number of pages that will be mapped using PTEs + * @vma: The vm area in which the mappings are added + * + * The page range of the folio is defined by [page, page + nr_pages) + * + * The caller needs to hold the page table lock. + */ +void folio_add_file_rmap_ptes(struct folio *folio, struct page *page, + int nr_pages, struct vm_area_struct *vma) +{ + __folio_add_file_rmap(folio, page, nr_pages, vma, PGTABLE_LEVEL_PTE); +} + +/** + * folio_add_file_rmap_pmd - add a PMD mapping to a page range of a folio + * @folio: The folio to add the mapping to + * @page: The first page to add + * @vma: The vm area in which the mapping is added + * + * The page range of the folio is defined by [page, page + HPAGE_PMD_NR) + * + * The caller needs to hold the page table lock. + */ +void folio_add_file_rmap_pmd(struct folio *folio, struct page *page, + struct vm_area_struct *vma) +{ +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + __folio_add_file_rmap(folio, page, HPAGE_PMD_NR, vma, PGTABLE_LEVEL_PMD); +#else + WARN_ON_ONCE(true); +#endif +} + +/** + * folio_add_file_rmap_pud - add a PUD mapping to a page range of a folio + * @folio: The folio to add the mapping to + * @page: The first page to add + * @vma: The vm area in which the mapping is added + * + * The page range of the folio is defined by [page, page + HPAGE_PUD_NR) + * + * The caller needs to hold the page table lock. + */ +void folio_add_file_rmap_pud(struct folio *folio, struct page *page, + struct vm_area_struct *vma) +{ +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && \ + defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) + __folio_add_file_rmap(folio, page, HPAGE_PUD_NR, vma, PGTABLE_LEVEL_PUD); +#else + WARN_ON_ONCE(true); +#endif +} + +static __always_inline void __folio_remove_rmap(struct folio *folio, + struct page *page, int nr_pages, struct vm_area_struct *vma, + enum pgtable_level level) +{ + atomic_t *mapped = &folio->_nr_pages_mapped; + int last = 0, nr = 0, nr_pmdmapped = 0; + bool partially_mapped = false; + + __folio_rmap_sanity_checks(folio, page, nr_pages, level); + + switch (level) { + case PGTABLE_LEVEL_PTE: + if (!folio_test_large(folio)) { + nr = atomic_add_negative(-1, &folio->_mapcount); + break; + } + + if (IS_ENABLED(CONFIG_NO_PAGE_MAPCOUNT)) { + nr = folio_sub_return_large_mapcount(folio, nr_pages, vma); + if (!nr) { + /* Now completely unmapped. */ + nr = folio_large_nr_pages(folio); + } else { + partially_mapped = nr < folio_large_nr_pages(folio) && + !folio_entire_mapcount(folio); + nr = 0; + } + break; + } + + folio_sub_large_mapcount(folio, nr_pages, vma); + do { + last += atomic_add_negative(-1, &page->_mapcount); + } while (page++, --nr_pages > 0); + + if (last && + atomic_sub_return_relaxed(last, mapped) < ENTIRELY_MAPPED) + nr = last; + + partially_mapped = nr && atomic_read(mapped); + break; + case PGTABLE_LEVEL_PMD: + case PGTABLE_LEVEL_PUD: + if (IS_ENABLED(CONFIG_NO_PAGE_MAPCOUNT)) { + last = atomic_add_negative(-1, &folio->_entire_mapcount); + if (level == PGTABLE_LEVEL_PMD && last) + nr_pmdmapped = folio_large_nr_pages(folio); + nr = folio_dec_return_large_mapcount(folio, vma); + if (!nr) { + /* Now completely unmapped. */ + nr = folio_large_nr_pages(folio); + } else { + partially_mapped = last && + nr < folio_large_nr_pages(folio); + nr = 0; + } + break; + } + + folio_dec_large_mapcount(folio, vma); + last = atomic_add_negative(-1, &folio->_entire_mapcount); + if (last) { + nr = atomic_sub_return_relaxed(ENTIRELY_MAPPED, mapped); + if (likely(nr < ENTIRELY_MAPPED)) { + nr_pages = folio_large_nr_pages(folio); + if (level == PGTABLE_LEVEL_PMD) + nr_pmdmapped = nr_pages; + nr = nr_pages - nr; + /* Raced ahead of another remove and an add? */ + if (unlikely(nr < 0)) + nr = 0; + } else { + /* An add of ENTIRELY_MAPPED raced ahead */ + nr = 0; + } + } + + partially_mapped = nr && nr < nr_pmdmapped; + break; + default: + BUILD_BUG(); + } + + /* + * Queue anon large folio for deferred split if at least one page of + * the folio is unmapped and at least one page is still mapped. + * + * Check partially_mapped first to ensure it is a large folio. + * + * Device private folios do not support deferred splitting and + * shrinker based scanning of the folios to free. + */ + if (partially_mapped && folio_test_anon(folio) && + !folio_test_partially_mapped(folio) && + !folio_is_device_private(folio)) + deferred_split_folio(folio, true); + + __folio_mod_stat(folio, -nr, -nr_pmdmapped); + + /* + * It would be tidy to reset folio_test_anon mapping when fully + * unmapped, but that might overwrite a racing folio_add_anon_rmap_*() + * which increments mapcount after us but sets mapping before us: + * so leave the reset to free_pages_prepare, and remember that + * it's only reliable while mapped. + */ + + munlock_vma_folio(folio, vma); +} + +/** + * folio_remove_rmap_ptes - remove PTE mappings from a page range of a folio + * @folio: The folio to remove the mappings from + * @page: The first page to remove + * @nr_pages: The number of pages that will be removed from the mapping + * @vma: The vm area from which the mappings are removed + * + * The page range of the folio is defined by [page, page + nr_pages) + * + * The caller needs to hold the page table lock. + */ +void folio_remove_rmap_ptes(struct folio *folio, struct page *page, + int nr_pages, struct vm_area_struct *vma) +{ + __folio_remove_rmap(folio, page, nr_pages, vma, PGTABLE_LEVEL_PTE); +} + +/** + * folio_remove_rmap_pmd - remove a PMD mapping from a page range of a folio + * @folio: The folio to remove the mapping from + * @page: The first page to remove + * @vma: The vm area from which the mapping is removed + * + * The page range of the folio is defined by [page, page + HPAGE_PMD_NR) + * + * The caller needs to hold the page table lock. + */ +void folio_remove_rmap_pmd(struct folio *folio, struct page *page, + struct vm_area_struct *vma) +{ +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + __folio_remove_rmap(folio, page, HPAGE_PMD_NR, vma, PGTABLE_LEVEL_PMD); +#else + WARN_ON_ONCE(true); +#endif +} + +/** + * folio_remove_rmap_pud - remove a PUD mapping from a page range of a folio + * @folio: The folio to remove the mapping from + * @page: The first page to remove + * @vma: The vm area from which the mapping is removed + * + * The page range of the folio is defined by [page, page + HPAGE_PUD_NR) + * + * The caller needs to hold the page table lock. + */ +void folio_remove_rmap_pud(struct folio *folio, struct page *page, + struct vm_area_struct *vma) +{ +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && \ + defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) + __folio_remove_rmap(folio, page, HPAGE_PUD_NR, vma, PGTABLE_LEVEL_PUD); +#else + WARN_ON_ONCE(true); +#endif +} + +static inline unsigned int folio_unmap_pte_batch(struct folio *folio, + struct page_vma_mapped_walk *pvmw, + enum ttu_flags flags, pte_t pte) +{ + unsigned long end_addr, addr = pvmw->address; + struct vm_area_struct *vma = pvmw->vma; + unsigned int max_nr; + + if (flags & TTU_HWPOISON) + return 1; + if (!folio_test_large(folio)) + return 1; + + /* We may only batch within a single VMA and a single page table. */ + end_addr = pmd_addr_end(addr, vma->vm_end); + max_nr = (end_addr - addr) >> PAGE_SHIFT; + + /* We only support lazyfree or file folios batching for now ... */ + if (folio_test_anon(folio) && folio_test_swapbacked(folio)) + return 1; + + if (pte_unused(pte)) + return 1; + + /* + * If unmap fails, we need to restore the ptes. To avoid accidentally + * upgrading write permissions for ptes that were not originally + * writable, and to avoid losing the soft-dirty bit, use the + * appropriate FPB flags. + */ + return folio_pte_batch_flags(folio, vma, pvmw->pte, &pte, max_nr, + FPB_RESPECT_WRITE | FPB_RESPECT_SOFT_DIRTY); +} + +static bool try_to_unmap_poisoned_hugetlb_one(struct folio *folio, + struct vm_area_struct *vma, unsigned long address, void *arg) +{ + DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0); + const unsigned long hsz = huge_page_size(hstate_vma(vma)); + const enum ttu_flags flags = (enum ttu_flags)(long)arg; + struct mm_struct *mm = vma->vm_mm; + struct mmu_notifier_range range; + bool ret = true; + pte_t pteval; + + /* + * The try_to_unmap() is only passed a hugetlb folio in the case + * where the hugetlb folio is poisoned. + */ + VM_WARN_ON_ONCE_FOLIO(!folio_test_hwpoison(folio), folio); + VM_WARN_ON_ONCE(!(flags & TTU_HWPOISON)); + + range.end = vma_address_end(&pvmw); + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm, + address, range.end); + adjust_range_if_pmd_sharing_possible(vma, &range.start, &range.end); + mmu_notifier_invalidate_range_start(&range); + + /* There is only a single mapping in a VMA. */ + if (!page_vma_mapped_walk(&pvmw)) + goto range_end; + + VM_WARN_ON_ONCE(address != pvmw.address); + + pteval = huge_ptep_get(mm, address, pvmw.pte); + VM_WARN_ON_ONCE(!pte_present(pteval)); + VM_WARN_ON_ONCE(pte_pfn(pteval) != folio_pfn(folio)); + + /* + * huge_pmd_unshare may unmap 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, range.start, range.end); + + /* + * To call huge_pmd_unshare, i_mmap_rwsem must be held in write mode. + * Caller needs to explicitly do this outside rmap routines. + * + * We also must hold hugetlb vma_lock in write mode. Lock order dictates + * acquiring vma_lock BEFORE i_mmap_rwsem. We can only try lock here and + * fail if unsuccessful. + */ + if (!folio_test_anon(folio)) { + struct mmu_gather tlb; + + VM_WARN_ON_ONCE(!(flags & TTU_RMAP_LOCKED)); + if (!hugetlb_vma_trylock_write(vma)) { + ret = false; + goto walk_done; + } + + tlb_gather_mmu_vma(&tlb, vma); + if (huge_pmd_unshare(&tlb, vma, address, pvmw.pte)) { + hugetlb_vma_unlock_write(vma); + huge_pmd_unshare_flush(&tlb, vma); + tlb_finish_mmu(&tlb); + /* + * The PMD table was unmapped, consequently unmapping + * the folio. + */ + goto walk_done; + } + hugetlb_vma_unlock_write(vma); + tlb_finish_mmu(&tlb); + } + pteval = huge_ptep_clear_flush(vma, address, pvmw.pte); + if (huge_pte_dirty(pteval)) + folio_mark_dirty(folio); + + pteval = swp_entry_to_pte(make_hwpoison_entry(folio_page(folio, 0))); + hugetlb_count_sub(folio_nr_pages(folio), mm); + set_huge_pte_at(mm, address, pvmw.pte, pteval, hsz); + hugetlb_remove_rmap(folio); + folio_put_refs(folio, 1); + +walk_done: + page_vma_mapped_walk_done(&pvmw); +range_end: + mmu_notifier_invalidate_range_end(&range); + return ret; +} + +static bool ttu_anon_lazyfree_folio(struct vm_area_struct *vma, + struct folio *folio, unsigned long nr_pages) +{ + int ref_count, map_count; + + /* + * Synchronize with gup_pte_range(): + * - clear PTE; barrier; read refcount + * - inc refcount; barrier; read PTE + */ + smp_mb(); + + ref_count = folio_ref_count(folio); + map_count = folio_mapcount(folio); + + /* + * Order reads for page refcount and dirty flag + * (see comments in __remove_mapping()). + */ + smp_rmb(); + + if (folio_test_dirty(folio) && !(vma->vm_flags & VM_DROPPABLE)) { + /* + * redirtied either using the page table or a previously + * obtained GUP reference. + */ + folio_set_swapbacked(folio); + return false; + } + + /* + * Additional references could be due to GUP or speculative lookups. + * GUP users must mark the folio dirty if there was a modification. + * This folio cannot be reclaimed right now either way, so act just + * like nothing happened. We'll come back here later and detect if the + * folio was dirtied when the additional reference is gone. + */ + if (ref_count != 1 + map_count) + return false; + + add_mm_counter(vma->vm_mm, MM_ANONPAGES, -nr_pages); + return true; +} + +static pte_t swp_pte_prepare(swp_entry_t entry, pte_t old_pte, + bool anon_exclusive) +{ + pte_t swp_pte = swp_entry_to_pte(entry); + + if (anon_exclusive) + swp_pte = pte_swp_mkexclusive(swp_pte); + + if (likely(pte_present(old_pte))) { + if (pte_soft_dirty(old_pte)) + swp_pte = pte_swp_mksoft_dirty(swp_pte); + if (pte_uffd(old_pte)) + swp_pte = pte_swp_mkuffd(swp_pte); + } else { + /* Device-exclusive entry */ + if (pte_swp_soft_dirty(old_pte)) + swp_pte = pte_swp_mksoft_dirty(swp_pte); + if (pte_swp_uffd(old_pte)) + swp_pte = pte_swp_mkuffd(swp_pte); + } + + return swp_pte; +} + +static bool ttu_anon_swapbacked_folio(struct vm_area_struct *vma, + struct folio *folio, struct page *page, unsigned long address, + pte_t *ptep, pte_t pteval) +{ + const bool anon_exclusive = folio_test_anon(folio) && + PageAnonExclusive(page); + swp_entry_t entry = page_swap_entry(page); + struct mm_struct *mm = vma->vm_mm; + + if (folio_dup_swap(folio, page) < 0) + return false; + + /* + * arch_unmap_one() is expected to be a NOP on + * architectures where we could have PFN swap PTEs, + * so we'll not check/care. + */ + if (arch_unmap_one(mm, vma, address, pteval) < 0) { + folio_put_swap(folio, page); + return false; + } + + /* See folio_try_share_anon_rmap(): clear PTE first. */ + if (anon_exclusive && folio_try_share_anon_rmap_pte(folio, page)) { + folio_put_swap(folio, page); + return false; + } + + mm_prepare_for_swap_entries(mm); + dec_mm_counter(mm, MM_ANONPAGES); + inc_mm_counter(mm, MM_SWAPENTS); + set_pte_at(mm, address, ptep, + swp_pte_prepare(entry, pteval, anon_exclusive)); + return true; +} + +static bool ttu_anon_folio(struct vm_area_struct *vma, struct folio *folio, + struct page *page, unsigned long address, pte_t *ptep, + pte_t pteval, unsigned long nr_pages) +{ + /* + * Store the swap location in the pte. + * See handle_pte_fault() ... + */ + if (WARN_ON_ONCE(folio_test_swapbacked(folio) != + folio_test_swapcache(folio))) + return false; + + if (!folio_test_swapbacked(folio)) + return ttu_anon_lazyfree_folio(vma, folio, nr_pages); + + /* nr_pages > 1 not supported yet */ + return ttu_anon_swapbacked_folio(vma, folio, page, address, ptep, + pteval); +} + +/* + * @arg: enum ttu_flags will be passed to this argument + */ +static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, + unsigned long address, void *arg) +{ + struct mm_struct *mm = vma->vm_mm; + DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0); + bool ret = true; + pte_t pteval; + struct page *page; + struct mmu_notifier_range range; + enum ttu_flags flags = (enum ttu_flags)(long)arg; + unsigned long nr_pages = 1, end_addr; + unsigned long pfn; + int ptes = 0; + + /* + * When racing against e.g. zap_pte_range() on another cpu, + * in between its ptep_get_and_clear_full() and folio_remove_rmap_*(), + * try_to_unmap() may return before folio_mapped() has become false, + * if page table locking is skipped: use TTU_SYNC to wait for that. + */ + if (flags & TTU_SYNC) + pvmw.flags = PVMW_SYNC; + + /* + * For THP, we have to assume the worse case ie pmd for invalidation. + * + * Note that the folio can not be freed in this function as call of + * try_to_unmap() must hold a reference on the folio. + */ + range.end = vma_address_end(&pvmw); + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm, + address, range.end); + mmu_notifier_invalidate_range_start(&range); + + while (page_vma_mapped_walk(&pvmw)) { + nr_pages = 1; + + /* + * If the folio is in an mlock()d vma, we must not swap it out. + */ + if (!(flags & TTU_IGNORE_MLOCK) && + (vma->vm_flags & VM_LOCKED)) { + ptes++; + + /* + * Set 'ret' to indicate the page cannot be unmapped. + * + * Do not jump to walk_abort immediately as additional + * iteration might be required to detect fully mapped + * folio an mlock it. + */ + ret = false; + + /* Only mlock fully mapped pages */ + if (pvmw.pte && ptes != pvmw.nr_pages) + continue; + + /* + * All PTEs must be protected by page table lock in + * order to mlock the page. + * + * If page table boundary has been cross, current ptl + * only protect part of ptes. + */ + if (pvmw.flags & PVMW_PGTABLE_CROSSED) + goto walk_done; + + /* Restore the mlock which got missed */ + mlock_vma_folio(folio, vma); + goto walk_done; + } + + if (!pvmw.pte) { + if (folio_test_lazyfree(folio)) { + if (unmap_huge_pmd_locked(vma, pvmw.address, pvmw.pmd, folio)) + goto walk_done; + /* + * unmap_huge_pmd_locked has either already marked + * the folio as swap-backed or decided to retain it + * due to GUP or speculative references. + */ + goto walk_abort; + } + + if (flags & TTU_SPLIT_HUGE_PMD) { + /* + * We temporarily have to drop the PTL and + * restart so we can process the PTE-mapped THP. + */ + split_huge_pmd_locked(vma, pvmw.address, + pvmw.pmd, false); + flags &= ~TTU_SPLIT_HUGE_PMD; + page_vma_mapped_walk_restart(&pvmw); + continue; + } + } + + /* Unexpected PMD-mapped THP? */ + VM_BUG_ON_FOLIO(!pvmw.pte, folio); + + address = pvmw.address; + if (folio_test_hugetlb(folio)) { + pteval = huge_ptep_get(mm, address, pvmw.pte); + } else { + pteval = ptep_get(pvmw.pte); + } + if (likely(pte_present(pteval))) { + pfn = pte_pfn(pteval); + } else { + /* + * Handle PFN swap PTEs, such as device-exclusive ones, + * that actually map pages. + */ + const softleaf_t entry = softleaf_from_pte(pteval); + + pfn = softleaf_to_pfn(entry); + } + + page = folio_page(folio, pfn - folio_pfn(folio)); + + if (likely(pte_present(pteval))) { + nr_pages = folio_unmap_pte_batch(folio, &pvmw, flags, pteval); + end_addr = address + nr_pages * PAGE_SIZE; + flush_cache_range(vma, address, end_addr); + + /* Nuke the page table entry. */ + pteval = get_and_clear_ptes(mm, address, pvmw.pte, nr_pages); + /* + * We clear the PTE but do not flush so potentially + * a remote CPU could still be writing to the folio. + * 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. + */ + if (should_defer_flush(mm, flags)) + set_tlb_ubc_flush_pending(mm, pteval, address, end_addr); + else + flush_tlb_range(vma, address, end_addr); + if (pte_dirty(pteval)) + folio_mark_dirty(folio); + } else { + pte_clear(mm, address, pvmw.pte); + } + + /* + * Now the pte is cleared. If this pte was uffd-wp armed, + * we may want to replace a none pte with a marker pte if + * it's file-backed, so we don't lose the tracking info. + */ + cond_install_uffd_wp_ptes(vma, address, pvmw.pte, pteval, + nr_pages); + + /* Update high watermark before we lower rss */ + update_hiwater_rss(mm); + + /* unmap_poisoned_folio() only refs order-0 folios */ + if (folio_test_hwpoison(folio) && (flags & TTU_HWPOISON)) { + pteval = swp_entry_to_pte(make_hwpoison_entry(page)); + dec_mm_counter(mm, mm_counter(folio)); + set_pte_at(mm, address, pvmw.pte, pteval); + } else if (likely(pte_present(pteval)) && 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(folio)); + } else if (folio_test_anon(folio)) { + if (!ttu_anon_folio(vma, folio, page, address, + pvmw.pte, pteval, nr_pages)) { + set_ptes(mm, address, pvmw.pte, pteval, nr_pages); + goto walk_abort; + } + + goto finish_unmap; + } else { + /* + * This is a locked file-backed folio, + * so it cannot be removed from the page + * cache and replaced by a new folio before + * mmu_notifier_invalidate_range_end, so no + * concurrent thread might update its page table + * to point at a new folio while a device is + * still using this folio. + * + * See Documentation/mm/mmu_notifier.rst + */ + add_mm_counter(mm, mm_counter_file(folio), -nr_pages); + } +finish_unmap: + folio_remove_rmap_ptes(folio, page, nr_pages, vma); + if (vma->vm_flags & VM_LOCKED) + mlock_drain_local(); + folio_put_refs(folio, nr_pages); + + /* + * If we are sure that we batched the entire folio and cleared + * all PTEs, we can just optimize and stop right here. + */ + if (nr_pages == folio_nr_pages(folio)) + goto walk_done; + continue; +walk_abort: + ret = false; +walk_done: + page_vma_mapped_walk_done(&pvmw); + break; + } + + mmu_notifier_invalidate_range_end(&range); + + return ret; +} + +static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg) +{ + return vma_is_temporary_stack(vma); +} + +static int folio_not_mapped(struct folio *folio) +{ + return !folio_mapped(folio); +} + +/** + * try_to_unmap - Try to remove all page table mappings to a folio. + * @folio: The folio to unmap. + * @flags: action and flags + * + * Tries to remove all the page table entries which are mapping this + * folio. It is the caller's responsibility to check if the folio is + * still mapped if needed (use TTU_SYNC to prevent accounting races). + * + * Context: Caller must hold the folio lock. + */ +void try_to_unmap(struct folio *folio, enum ttu_flags flags) +{ + struct rmap_walk_control rwc = { + .rmap_one = folio_test_hugetlb(folio) ? + try_to_unmap_poisoned_hugetlb_one : try_to_unmap_one, + .arg = (void *)flags, + .done = folio_not_mapped, + .anon_lock = folio_lock_anon_vma_read, + }; + + if (flags & TTU_RMAP_LOCKED) + rmap_walk_locked(folio, &rwc); + else + rmap_walk(folio, &rwc); +} + +/* + * @arg: enum ttu_flags will be passed to this argument. + * + * If TTU_SPLIT_HUGE_PMD is specified any PMD mappings will be split into PTEs + * containing migration entries. + */ +static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, + unsigned long address, void *arg) +{ + struct mm_struct *mm = vma->vm_mm; + DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0); + bool anon_exclusive, writable, ret = true; + pte_t pteval; + struct page *subpage; + struct mmu_notifier_range range; + enum ttu_flags flags = (enum ttu_flags)(long)arg; + unsigned long pfn; + unsigned long hsz = 0; + + /* + * When racing against e.g. zap_pte_range() on another cpu, + * in between its ptep_get_and_clear_full() and folio_remove_rmap_*(), + * try_to_migrate() may return before folio_mapped() has become false, + * if page table locking is skipped: use TTU_SYNC to wait for that. + */ + if (flags & TTU_SYNC) + pvmw.flags = PVMW_SYNC; + + /* + * 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. + */ + range.end = vma_address_end(&pvmw); + mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm, + address, range.end); + if (folio_test_hugetlb(folio)) { + /* + * If sharing is possible, start and end will be adjusted + * accordingly. + */ + adjust_range_if_pmd_sharing_possible(vma, &range.start, + &range.end); + + /* We need the huge page size for set_huge_pte_at() */ + hsz = huge_page_size(hstate_vma(vma)); + } + mmu_notifier_invalidate_range_start(&range); + + while (page_vma_mapped_walk(&pvmw)) { + /* PMD-mapped THP migration entry */ + if (!pvmw.pte) { + __maybe_unused unsigned long pfn; + __maybe_unused pmd_t pmdval; + + if (flags & TTU_SPLIT_HUGE_PMD) { + /* + * split_huge_pmd_locked() might leave the + * folio mapped through PTEs. Retry the walk + * so we can detect this scenario and properly + * abort the walk. + */ + split_huge_pmd_locked(vma, pvmw.address, + pvmw.pmd, true); + flags &= ~TTU_SPLIT_HUGE_PMD; + page_vma_mapped_walk_restart(&pvmw); + continue; + } +#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES + pmdval = pmdp_get(pvmw.pmd); + if (likely(pmd_present(pmdval))) + pfn = pmd_pfn(pmdval); + else + pfn = softleaf_to_pfn(softleaf_from_pmd(pmdval)); + + subpage = folio_page(folio, pfn - folio_pfn(folio)); + + VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) || + !folio_test_pmd_mappable(folio), folio); + + if (set_pmd_migration_entry(&pvmw, subpage)) { + ret = false; + page_vma_mapped_walk_done(&pvmw); + break; + } + continue; +#endif + } + + /* Unexpected PMD-mapped THP? */ + VM_BUG_ON_FOLIO(!pvmw.pte, folio); + + address = pvmw.address; + if (folio_test_hugetlb(folio)) + pteval = huge_ptep_get(mm, address, pvmw.pte); + else + pteval = ptep_get(pvmw.pte); + if (likely(pte_present(pteval))) { + pfn = pte_pfn(pteval); + } else { + /* + * Handle PFN swap PTEs, such as device-exclusive ones, + * that actually map pages. + */ + const softleaf_t entry = softleaf_from_pte(pteval); + + pfn = softleaf_to_pfn(entry); + VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio); + } + + subpage = folio_page(folio, pfn - folio_pfn(folio)); + anon_exclusive = folio_test_anon(folio) && + PageAnonExclusive(subpage); + + if (folio_test_hugetlb(folio)) { + bool anon = folio_test_anon(folio); + + /* + * huge_pmd_unshare may unmap 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, range.start, range.end); + + /* + * To call huge_pmd_unshare, i_mmap_rwsem must be + * held in write mode. Caller needs to explicitly + * do this outside rmap routines. + * + * We also must hold hugetlb vma_lock in write mode. + * Lock order dictates acquiring vma_lock BEFORE + * i_mmap_rwsem. We can only try lock here and + * fail if unsuccessful. + */ + if (!anon) { + struct mmu_gather tlb; + + VM_BUG_ON(!(flags & TTU_RMAP_LOCKED)); + if (!hugetlb_vma_trylock_write(vma)) { + page_vma_mapped_walk_done(&pvmw); + ret = false; + break; + } + + tlb_gather_mmu_vma(&tlb, vma); + if (huge_pmd_unshare(&tlb, vma, address, pvmw.pte)) { + hugetlb_vma_unlock_write(vma); + huge_pmd_unshare_flush(&tlb, vma); + tlb_finish_mmu(&tlb); + /* + * The PMD table was unmapped, + * consequently unmapping the folio. + */ + page_vma_mapped_walk_done(&pvmw); + break; + } + hugetlb_vma_unlock_write(vma); + tlb_finish_mmu(&tlb); + } + /* Nuke the hugetlb page table entry */ + pteval = huge_ptep_clear_flush(vma, address, pvmw.pte); + if (pte_dirty(pteval)) + folio_mark_dirty(folio); + writable = pte_write(pteval); + } else if (likely(pte_present(pteval))) { + flush_cache_page(vma, address, pfn); + /* Nuke the page table entry. */ + 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 folio. + * 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, pteval, address, address + PAGE_SIZE); + } else { + pteval = ptep_clear_flush(vma, address, pvmw.pte); + } + if (pte_dirty(pteval)) + folio_mark_dirty(folio); + writable = pte_write(pteval); + } else { + const softleaf_t entry = softleaf_from_pte(pteval); + + pte_clear(mm, address, pvmw.pte); + + writable = softleaf_is_device_private_write(entry); + } + + VM_WARN_ON_FOLIO(writable && folio_test_anon(folio) && + !anon_exclusive, folio); + + /* Update high watermark before we lower rss */ + update_hiwater_rss(mm); + + if (PageHWPoison(subpage)) { + VM_WARN_ON_FOLIO(folio_is_device_private(folio), folio); + + pteval = swp_entry_to_pte(make_hwpoison_entry(subpage)); + if (folio_test_hugetlb(folio)) { + hugetlb_count_sub(folio_nr_pages(folio), mm); + set_huge_pte_at(mm, address, pvmw.pte, pteval, + hsz); + } else { + dec_mm_counter(mm, mm_counter(folio)); + set_pte_at(mm, address, pvmw.pte, pteval); + } + } else if (likely(pte_present(pteval)) && 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(folio)); + } else { + swp_entry_t entry; + pte_t swp_pte; + + /* + * arch_unmap_one() is expected to be a NOP on + * architectures where we could have PFN swap PTEs, + * so we'll not check/care. + */ + if (arch_unmap_one(mm, vma, address, pteval) < 0) { + if (folio_test_hugetlb(folio)) + set_huge_pte_at(mm, address, pvmw.pte, + pteval, hsz); + else + set_pte_at(mm, address, pvmw.pte, pteval); + ret = false; + page_vma_mapped_walk_done(&pvmw); + break; + } + + /* See folio_try_share_anon_rmap_pte(): clear PTE first. */ + if (folio_test_hugetlb(folio)) { + if (anon_exclusive && + hugetlb_try_share_anon_rmap(folio)) { + set_huge_pte_at(mm, address, pvmw.pte, + pteval, hsz); + ret = false; + page_vma_mapped_walk_done(&pvmw); + break; + } + } else if (anon_exclusive && + folio_try_share_anon_rmap_pte(folio, subpage)) { + 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. + */ + if (writable) + entry = make_writable_migration_entry( + page_to_pfn(subpage)); + else if (anon_exclusive) + entry = make_readable_exclusive_migration_entry( + page_to_pfn(subpage)); + else + entry = make_readable_migration_entry( + page_to_pfn(subpage)); + if (likely(pte_present(pteval))) { + if (pte_young(pteval)) + entry = make_migration_entry_young(entry); + if (pte_dirty(pteval)) + entry = make_migration_entry_dirty(entry); + swp_pte = swp_entry_to_pte(entry); + if (pte_soft_dirty(pteval)) + swp_pte = pte_swp_mksoft_dirty(swp_pte); + if (pte_uffd(pteval)) + swp_pte = pte_swp_mkuffd(swp_pte); + } else { + swp_pte = swp_entry_to_pte(entry); + if (pte_swp_soft_dirty(pteval)) + swp_pte = pte_swp_mksoft_dirty(swp_pte); + if (pte_swp_uffd(pteval)) + swp_pte = pte_swp_mkuffd(swp_pte); + } + if (folio_test_hugetlb(folio)) + set_huge_pte_at(mm, address, pvmw.pte, swp_pte, + hsz); + else + set_pte_at(mm, address, pvmw.pte, swp_pte); + trace_set_migration_pte(address, pte_val(swp_pte), + folio_order(folio)); + /* + * No need to invalidate here it will synchronize on + * against the special swap migration pte. + */ + } + + if (unlikely(folio_test_hugetlb(folio))) + hugetlb_remove_rmap(folio); + else + folio_remove_rmap_pte(folio, subpage, vma); + if (vma->vm_flags & VM_LOCKED) + mlock_drain_local(); + folio_put(folio); + } + + mmu_notifier_invalidate_range_end(&range); + + return ret; +} + +/** + * try_to_migrate - try to replace all page table mappings with swap entries + * @folio: the folio to replace page table entries for + * @flags: action and flags + * + * Tries to remove all the page table entries which are mapping this folio and + * replace them with special swap entries. Caller must hold the folio lock. + */ +void try_to_migrate(struct folio *folio, enum ttu_flags flags) +{ + struct rmap_walk_control rwc = { + .rmap_one = try_to_migrate_one, + .arg = (void *)flags, + .done = folio_not_mapped, + .anon_lock = folio_lock_anon_vma_read, + }; + + /* + * Migration always ignores mlock and only supports TTU_RMAP_LOCKED and + * TTU_SPLIT_HUGE_PMD, TTU_SYNC, and TTU_BATCH_FLUSH flags. + */ + if (WARN_ON_ONCE(flags & ~(TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD | + TTU_SYNC | TTU_BATCH_FLUSH))) + return; + + if (folio_is_zone_device(folio) && + (!folio_is_device_private(folio) && !folio_is_device_coherent(folio))) + return; + + /* + * 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 (!folio_test_ksm(folio) && folio_test_anon(folio)) + rwc.invalid_vma = invalid_migration_vma; + + if (flags & TTU_RMAP_LOCKED) + rmap_walk_locked(folio, &rwc); + else + rmap_walk(folio, &rwc); +} + +#ifdef CONFIG_DEVICE_PRIVATE +/** + * make_device_exclusive() - Mark a page for exclusive use by a device + * @mm: mm_struct of associated target process + * @addr: the virtual address to mark for exclusive device access + * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier to allow filtering + * @foliop: folio pointer will be stored here on success. + * + * This function looks up the page mapped at the given address, grabs a + * folio reference, locks the folio and replaces the PTE with special + * device-exclusive PFN swap entry, preventing access through the process + * page tables. The function will return with the folio locked and referenced. + * + * On fault, the device-exclusive entries are replaced with the original PTE + * under folio lock, after calling MMU notifiers. + * + * Only anonymous non-hugetlb folios are supported and the VMA must have + * write permissions such that we can fault in the anonymous page writable + * in order to mark it exclusive. The caller must hold the mmap_lock in read + * mode. + * + * A driver using this to program access from a device must use a mmu notifier + * critical section to hold a device specific lock during programming. Once + * programming is complete it should drop the folio lock and reference after + * which point CPU access to the page will revoke the exclusive access. + * + * Notes: + * #. This function always operates on individual PTEs mapping individual + * pages. PMD-sized THPs are first remapped to be mapped by PTEs before + * the conversion happens on a single PTE corresponding to @addr. + * #. While concurrent access through the process page tables is prevented, + * concurrent access through other page references (e.g., earlier GUP + * invocation) is not handled and not supported. + * #. device-exclusive entries are considered "clean" and "old" by core-mm. + * Device drivers must update the folio state when informed by MMU + * notifiers. + * + * Returns: pointer to mapped page on success, otherwise a negative error. + */ +struct page *make_device_exclusive(struct mm_struct *mm, unsigned long addr, + void *owner, struct folio **foliop) +{ + struct mmu_notifier_range range; + struct folio *folio, *fw_folio; + struct vm_area_struct *vma; + struct folio_walk fw; + struct page *page; + swp_entry_t entry; + pte_t swp_pte; + int ret; + + mmap_assert_locked(mm); + addr = PAGE_ALIGN_DOWN(addr); + + /* + * Fault in the page writable and try to lock it; note that if the + * address would already be marked for exclusive use by a device, + * the GUP call would undo that first by triggering a fault. + * + * If any other device would already map this page exclusively, the + * fault will trigger a conversion to an ordinary + * (non-device-exclusive) PTE and issue a MMU_NOTIFY_EXCLUSIVE. + */ +retry: + page = get_user_page_vma_remote(mm, addr, + FOLL_GET | FOLL_WRITE | FOLL_SPLIT_PMD, + &vma); + if (IS_ERR(page)) + return page; + folio = page_folio(page); + + if (!folio_test_anon(folio) || folio_test_hugetlb(folio)) { + folio_put(folio); + return ERR_PTR(-EOPNOTSUPP); + } + + ret = folio_lock_killable(folio); + if (ret) { + folio_put(folio); + return ERR_PTR(ret); + } + + /* + * Inform secondary MMUs that we are going to convert this PTE to + * device-exclusive, such that they unmap it now. Note that the + * caller must filter this event out to prevent livelocks. + */ + mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0, + mm, addr, addr + PAGE_SIZE, owner); + mmu_notifier_invalidate_range_start(&range); + + /* + * Let's do a second walk and make sure we still find the same page + * mapped writable. Note that any page of an anonymous folio can + * only be mapped writable using exactly one PTE ("exclusive"), so + * there cannot be other mappings. + */ + fw_folio = folio_walk_start(&fw, vma, addr, 0); + if (fw_folio != folio || fw.page != page || + fw.level != FW_LEVEL_PTE || !pte_write(fw.pte)) { + if (fw_folio) + folio_walk_end(&fw, vma); + mmu_notifier_invalidate_range_end(&range); + folio_unlock(folio); + folio_put(folio); + goto retry; + } + + /* Nuke the page table entry so we get the uptodate dirty bit. */ + flush_cache_page(vma, addr, page_to_pfn(page)); + fw.pte = ptep_clear_flush(vma, addr, fw.ptep); + + /* Set the dirty flag on the folio now the PTE is gone. */ + if (pte_dirty(fw.pte)) + folio_mark_dirty(folio); + + /* + * Store the pfn of the page in a special device-exclusive PFN swap PTE. + * do_swap_page() will trigger the conversion back while holding the + * folio lock. + */ + entry = make_device_exclusive_entry(page_to_pfn(page)); + swp_pte = swp_entry_to_pte(entry); + if (pte_soft_dirty(fw.pte)) + swp_pte = pte_swp_mksoft_dirty(swp_pte); + /* The pte is writable, uffd-wp does not apply. */ + set_pte_at(mm, addr, fw.ptep, swp_pte); + + folio_walk_end(&fw, vma); + mmu_notifier_invalidate_range_end(&range); + *foliop = folio; + return page; +} +EXPORT_SYMBOL_GPL(make_device_exclusive); +#endif + +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(const struct folio *folio, + struct rmap_walk_control *rwc) +{ + struct anon_vma *anon_vma; + + if (rwc->anon_lock) + return rwc->anon_lock(folio, rwc); + + /* + * Note: remove_migration_ptes() cannot use folio_lock_anon_vma_read() + * because that depends on folio_mapped(); but not all its usages + * are holding mmap_lock. Users without mmap_lock are required to + * take a reference count to prevent the anon_vma disappearing + */ + anon_vma = folio_anon_vma(folio); + if (!anon_vma) + return NULL; + + if (anon_vma_trylock_read(anon_vma)) + goto out; + + if (rwc->try_lock) { + anon_vma = NULL; + rwc->contended = true; + goto out; + } + + anon_vma_lock_read(anon_vma); +out: + return anon_vma; +} + +/* + * rmap_walk_anon - do something to anonymous page using the object-based + * rmap method + * @folio: the folio to be handled + * @rwc: control variable according to each walk type + * @locked: caller holds relevant rmap lock + * + * Find all the mappings of a folio using the mapping pointer and the vma + * chains contained in the anon_vma struct it points to. + */ +static void rmap_walk_anon(struct folio *folio, + struct rmap_walk_control *rwc, bool locked) +{ + struct anon_vma *anon_vma; + pgoff_t pgoff_start, pgoff_end; + struct anon_vma_chain *avc; + + /* + * The folio lock ensures that folio->mapping can't be changed under us + * to an anon_vma with different root. + */ + VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio); + + if (locked) { + anon_vma = folio_anon_vma(folio); + /* anon_vma disappear under us? */ + VM_BUG_ON_FOLIO(!anon_vma, folio); + } else { + anon_vma = rmap_walk_anon_lock(folio, rwc); + } + if (!anon_vma) + return; + + pgoff_start = folio_pgoff(folio); + pgoff_end = pgoff_start + folio_nr_pages(folio) - 1; + anon_rmap_tree_foreach(avc, anon_vma, pgoff_start, pgoff_end) { + struct vm_area_struct *vma = avc->vma; + unsigned long address = vma_address(vma, pgoff_start, + folio_nr_pages(folio)); + + VM_BUG_ON_VMA(address == -EFAULT, vma); + cond_resched(); + + if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) + continue; + + if (!rwc->rmap_one(folio, vma, address, rwc->arg)) + break; + if (rwc->done && rwc->done(folio)) + break; + } + + if (!locked) + anon_vma_unlock_read(anon_vma); +} + +/** + * __rmap_walk_file() - Traverse the reverse mapping for a file-backed mapping + * of a page mapped within a specified page cache object at a specified offset. + * + * @folio: Either the folio whose mappings to traverse, or if NULL, + * the callbacks specified in @rwc will be configured such + * as to be able to look up mappings correctly. + * @mapping: The page cache object whose mapping VMAs we intend to + * traverse. If @folio is non-NULL, this should be equal to + * folio_mapping(folio). + * @pgoff_start: The offset within @mapping of the page which we are + * looking up. If @folio is non-NULL, this should be equal + * to folio_pgoff(folio). + * @nr_pages: The number of pages mapped by the mapping. If @folio is + * non-NULL, this should be equal to folio_nr_pages(folio). + * @rwc: The reverse mapping walk control object describing how + * the traversal should proceed. + * @locked: Is the @mapping already locked? If not, we acquire the + * lock. + */ +static void __rmap_walk_file(struct folio *folio, struct address_space *mapping, + pgoff_t pgoff_start, unsigned long nr_pages, + struct rmap_walk_control *rwc, bool locked) +{ + pgoff_t pgoff_end = pgoff_start + nr_pages - 1; + struct vm_area_struct *vma; + + VM_WARN_ON_FOLIO(folio && mapping != folio_mapping(folio), folio); + VM_WARN_ON_FOLIO(folio && pgoff_start != folio_pgoff(folio), folio); + VM_WARN_ON_FOLIO(folio && nr_pages != folio_nr_pages(folio), folio); + + if (!locked) { + if (i_mmap_trylock_read(mapping)) + goto lookup; + + if (rwc->try_lock) { + rwc->contended = true; + return; + } + + i_mmap_lock_read(mapping); + } +lookup: + mapping_rmap_tree_foreach(vma, mapping, pgoff_start, pgoff_end) { + unsigned long address = vma_address(vma, pgoff_start, nr_pages); + + VM_BUG_ON_VMA(address == -EFAULT, vma); + cond_resched(); + + if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) + continue; + + if (!rwc->rmap_one(folio, vma, address, rwc->arg)) + goto done; + if (rwc->done && rwc->done(folio)) + goto done; + } +done: + if (!locked) + i_mmap_unlock_read(mapping); +} + +/* + * rmap_walk_file - do something to file page using the object-based rmap method + * @folio: the folio to be handled + * @rwc: control variable according to each walk type + * @locked: caller holds relevant rmap lock + * + * Find all the mappings of a folio using the mapping pointer and the vma chains + * contained in the address_space struct it points to. + */ +static void rmap_walk_file(struct folio *folio, + struct rmap_walk_control *rwc, bool locked) +{ + /* + * The folio lock not only makes sure that folio->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_FOLIO(!folio_test_locked(folio), folio); + + if (!folio->mapping) + return; + + __rmap_walk_file(folio, folio->mapping, folio->index, + folio_nr_pages(folio), rwc, locked); +} + +void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc) +{ + if (unlikely(folio_test_ksm(folio))) + rmap_walk_ksm(folio, rwc); + else if (folio_test_anon(folio)) + rmap_walk_anon(folio, rwc, false); + else + rmap_walk_file(folio, rwc, false); +} + +/* Like rmap_walk, but caller holds relevant rmap lock */ +void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc) +{ + /* no ksm support for now */ + VM_BUG_ON_FOLIO(folio_test_ksm(folio), folio); + if (folio_test_anon(folio)) + rmap_walk_anon(folio, rwc, true); + else + rmap_walk_file(folio, rwc, true); +} + +#ifdef CONFIG_HUGETLB_PAGE +/* + * The following two 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. + */ +void hugetlb_add_anon_rmap(struct folio *folio, struct vm_area_struct *vma, + unsigned long address, rmap_t flags) +{ + VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio); + VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); + + atomic_inc(&folio->_entire_mapcount); + atomic_inc(&folio->_large_mapcount); + if (flags & RMAP_EXCLUSIVE) + SetPageAnonExclusive(&folio->page); + VM_WARN_ON_FOLIO(folio_entire_mapcount(folio) > 1 && + PageAnonExclusive(&folio->page), folio); +} + +void hugetlb_add_new_anon_rmap(struct folio *folio, + struct vm_area_struct *vma, unsigned long address) +{ + VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio); + + BUG_ON(address < vma->vm_start || address >= vma->vm_end); + /* increment count (starts at -1) */ + atomic_set(&folio->_entire_mapcount, 0); + atomic_set(&folio->_large_mapcount, 0); + folio_clear_hugetlb_restore_reserve(folio); + __folio_set_anon(folio, vma, address, true); + SetPageAnonExclusive(&folio->page); +} +#endif /* CONFIG_HUGETLB_PAGE */ |