| /* |
| * mm/rmap.c - physical to virtual reverse mappings |
| * |
| * Copyright 2001, Rik van Riel <riel@conectiva.com.br> |
| * Released under the General Public License (GPL). |
| * |
| * Simple, low overhead reverse mapping scheme. |
| * Please try to keep this thing as modular as possible. |
| * |
| * Provides methods for unmapping each kind of mapped page: |
| * the anon methods track anonymous pages, and |
| * the file methods track pages belonging to an inode. |
| * |
| * Original design by Rik van Riel <riel@conectiva.com.br> 2001 |
| * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004 |
| * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004 |
| * Contributions by Hugh Dickins 2003, 2004 |
| */ |
| |
| /* |
| * Lock ordering in mm: |
| * |
| * inode->i_rwsem (while writing or truncating, not reading or faulting) |
| * mm->mmap_lock |
| * mapping->invalidate_lock (in filemap_fault) |
| * page->flags PG_locked (lock_page) |
| * hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share, see hugetlbfs below) |
| * 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) |
| * folio_lock_memcg move_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) |
| * page->flags PG_locked (lock_page) |
| */ |
| |
| #include <linux/mm.h> |
| #include <linux/sched/mm.h> |
| #include <linux/sched/task.h> |
| #include <linux/pagemap.h> |
| #include <linux/swap.h> |
| #include <linux/swapops.h> |
| #include <linux/slab.h> |
| #include <linux/init.h> |
| #include <linux/ksm.h> |
| #include <linux/rmap.h> |
| #include <linux/rcupdate.h> |
| #include <linux/export.h> |
| #include <linux/memcontrol.h> |
| #include <linux/mmu_notifier.h> |
| #include <linux/migrate.h> |
| #include <linux/hugetlb.h> |
| #include <linux/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 <asm/tlbflush.h> |
| |
| #define CREATE_TRACE_POINTS |
| #include <trace/events/tlb.h> |
| #include <trace/events/migrate.h> |
| |
| #include "internal.h" |
| |
| static struct kmem_cache *anon_vma_cachep; |
| static struct kmem_cache *anon_vma_chain_cachep; |
| |
| static inline struct anon_vma *anon_vma_alloc(void) |
| { |
| struct anon_vma *anon_vma; |
| |
| anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); |
| if (anon_vma) { |
| atomic_set(&anon_vma->refcount, 1); |
| anon_vma->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_link(struct vm_area_struct *vma, |
| struct anon_vma_chain *avc, |
| struct anon_vma *anon_vma) |
| { |
| avc->vma = vma; |
| avc->anon_vma = anon_vma; |
| list_add(&avc->same_vma, &vma->anon_vma_chain); |
| anon_vma_interval_tree_insert(avc, &anon_vma->rb_root); |
| } |
| |
| /** |
| * __anon_vma_prepare - attach an anon_vma to a memory region |
| * @vma: the memory region in question |
| * |
| * This makes sure the memory mapping described by 'vma' has |
| * an 'anon_vma' attached to it, so that we can associate the |
| * anonymous pages mapped into it with that anon_vma. |
| * |
| * The common case will be that we already have one, which |
| * is handled inline by anon_vma_prepare(). But if |
| * not we either need to find an adjacent mapping that we |
| * can re-use the anon_vma from (very common when the only |
| * reason for splitting a vma has been mprotect()), or we |
| * allocate a new one. |
| * |
| * Anon-vma allocations are very subtle, because we may have |
| * optimistically looked up an anon_vma in 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. |
| * |
| * This must be called with the mmap_lock held for reading. |
| */ |
| int __anon_vma_prepare(struct vm_area_struct *vma) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| struct anon_vma *anon_vma, *allocated; |
| struct anon_vma_chain *avc; |
| |
| might_sleep(); |
| |
| avc = anon_vma_chain_alloc(GFP_KERNEL); |
| if (!avc) |
| goto out_enomem; |
| |
| anon_vma = find_mergeable_anon_vma(vma); |
| allocated = NULL; |
| if (!anon_vma) { |
| anon_vma = anon_vma_alloc(); |
| if (unlikely(!anon_vma)) |
| goto out_enomem_free_avc; |
| 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_link(vma, 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; |
| } |
| |
| /* |
| * This is a useful helper function for locking the anon_vma root as |
| * we traverse the vma->anon_vma_chain, looping over anon_vma's that |
| * have the same vma. |
| * |
| * Such anon_vma's should have the same root, so you'd expect to see |
| * just a single mutex_lock for the whole traversal. |
| */ |
| static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma) |
| { |
| struct anon_vma *new_root = anon_vma->root; |
| if (new_root != root) { |
| if (WARN_ON_ONCE(root)) |
| up_write(&root->rwsem); |
| root = new_root; |
| down_write(&root->rwsem); |
| } |
| return root; |
| } |
| |
| static inline void unlock_anon_vma_root(struct anon_vma *root) |
| { |
| if (root) |
| up_write(&root->rwsem); |
| } |
| |
| /* |
| * Attach the anon_vmas from src to dst. |
| * Returns 0 on success, -ENOMEM on failure. |
| * |
| * anon_vma_clone() is called by __vma_adjust(), __split_vma(), copy_vma() and |
| * anon_vma_fork(). The first three want an exact copy of src, while the last |
| * one, anon_vma_fork(), may try to reuse an existing anon_vma to prevent |
| * endless growth of anon_vma. Since dst->anon_vma is set to NULL before call, |
| * we can identify this case by checking (!dst->anon_vma && src->anon_vma). |
| * |
| * If (!dst->anon_vma && src->anon_vma) is true, this function tries to find |
| * and reuse existing anon_vma which has no vmas and only one child anon_vma. |
| * This prevents degradation of anon_vma hierarchy to endless linear chain in |
| * case of constantly forking task. On the other hand, an anon_vma with more |
| * than one child isn't reused even if there was no alive vma, thus rmap |
| * walker has a good chance of avoiding scanning the whole hierarchy when it |
| * searches where page is mapped. |
| */ |
| int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) |
| { |
| struct anon_vma_chain *avc, *pavc; |
| struct anon_vma *root = NULL; |
| |
| list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) { |
| struct anon_vma *anon_vma; |
| |
| avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN); |
| if (unlikely(!avc)) { |
| unlock_anon_vma_root(root); |
| root = NULL; |
| avc = anon_vma_chain_alloc(GFP_KERNEL); |
| if (!avc) |
| goto enomem_failure; |
| } |
| anon_vma = pavc->anon_vma; |
| root = lock_anon_vma_root(root, anon_vma); |
| anon_vma_chain_link(dst, avc, anon_vma); |
| |
| /* |
| * Reuse existing anon_vma if it has no vma and only one |
| * anon_vma child. |
| * |
| * Root anon_vma is never reused: |
| * it has self-parent reference and at least one child. |
| */ |
| if (!dst->anon_vma && src->anon_vma && |
| anon_vma->num_children < 2 && |
| anon_vma->num_active_vmas == 0) |
| dst->anon_vma = anon_vma; |
| } |
| if (dst->anon_vma) |
| dst->anon_vma->num_active_vmas++; |
| unlock_anon_vma_root(root); |
| return 0; |
| |
| enomem_failure: |
| /* |
| * dst->anon_vma is dropped here otherwise its degree can be incorrectly |
| * decremented in unlink_anon_vmas(). |
| * We can safely do this because callers of anon_vma_clone() don't care |
| * about dst->anon_vma if anon_vma_clone() failed. |
| */ |
| dst->anon_vma = NULL; |
| unlink_anon_vmas(dst); |
| return -ENOMEM; |
| } |
| |
| /* |
| * Attach vma to its own anon_vma, as well as to the anon_vmas that |
| * the corresponding VMA in the parent process is attached to. |
| * Returns 0 on success, non-zero on failure. |
| */ |
| int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) |
| { |
| struct anon_vma_chain *avc; |
| struct anon_vma *anon_vma; |
| int error; |
| |
| /* Don't bother if the parent process has no anon_vma here. */ |
| if (!pvma->anon_vma) |
| return 0; |
| |
| /* Drop inherited anon_vma, we'll reuse existing or allocate new. */ |
| vma->anon_vma = NULL; |
| |
| /* |
| * First, attach the new VMA to the parent VMA's anon_vmas, |
| * so rmap can find non-COWed pages in child processes. |
| */ |
| error = anon_vma_clone(vma, pvma); |
| if (error) |
| return error; |
| |
| /* An existing anon_vma has been reused, all done then. */ |
| if (vma->anon_vma) |
| return 0; |
| |
| /* Then add our own anon_vma. */ |
| anon_vma = anon_vma_alloc(); |
| if (!anon_vma) |
| goto out_error; |
| anon_vma->num_active_vmas++; |
| avc = anon_vma_chain_alloc(GFP_KERNEL); |
| if (!avc) |
| goto out_error_free_anon_vma; |
| |
| /* |
| * 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_lock_write(anon_vma); |
| anon_vma_chain_link(vma, avc, anon_vma); |
| anon_vma->parent->num_children++; |
| anon_vma_unlock_write(anon_vma); |
| |
| return 0; |
| |
| out_error_free_anon_vma: |
| put_anon_vma(anon_vma); |
| out_error: |
| unlink_anon_vmas(vma); |
| return -ENOMEM; |
| } |
| |
| void unlink_anon_vmas(struct vm_area_struct *vma) |
| { |
| struct anon_vma_chain *avc, *next; |
| struct anon_vma *root = NULL; |
| |
| /* |
| * Unlink each anon_vma chained to the VMA. This list is ordered |
| * from newest to oldest, ensuring the root anon_vma gets freed last. |
| */ |
| list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { |
| struct anon_vma *anon_vma = avc->anon_vma; |
| |
| root = lock_anon_vma_root(root, anon_vma); |
| anon_vma_interval_tree_remove(avc, &anon_vma->rb_root); |
| |
| /* |
| * Leave empty anon_vmas on the list - we'll need |
| * to free them outside the lock. |
| */ |
| if (RB_EMPTY_ROOT(&anon_vma->rb_root.rb_root)) { |
| anon_vma->parent->num_children--; |
| continue; |
| } |
| |
| list_del(&avc->same_vma); |
| anon_vma_chain_free(avc); |
| } |
| if (vma->anon_vma) { |
| vma->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; |
| } |
| unlock_anon_vma_root(root); |
| |
| /* |
| * Iterate the list once more, it now only contains empty and unlinked |
| * anon_vmas, destroy them. Could not do before due to __put_anon_vma() |
| * needing to write-acquire the anon_vma->root->rwsem. |
| */ |
| list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { |
| struct anon_vma *anon_vma = avc->anon_vma; |
| |
| VM_WARN_ON(anon_vma->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 page_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 page_mapped() [ hence all those page_mapped() tests ]. |
| * |
| * All users of this function must be very careful when walking the anon_vma |
| * chain and verify that the page in question is indeed mapped in it |
| * [ something equivalent to page_mapped_in_vma() ]. |
| * |
| * Since anon_vma's slab is SLAB_TYPESAFE_BY_RCU and we know from |
| * page_remove_rmap() that the anon_vma pointer from page->mapping is valid |
| * if there is a mapcount, we can dereference the anon_vma after observing |
| * those. |
| */ |
| struct anon_vma *folio_get_anon_vma(struct folio *folio) |
| { |
| struct anon_vma *anon_vma = NULL; |
| unsigned long anon_mapping; |
| |
| rcu_read_lock(); |
| anon_mapping = (unsigned long)READ_ONCE(folio->mapping); |
| if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) |
| goto out; |
| if (!folio_mapped(folio)) |
| goto out; |
| |
| anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); |
| if (!atomic_inc_not_zero(&anon_vma->refcount)) { |
| anon_vma = NULL; |
| goto out; |
| } |
| |
| /* |
| * If this 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(struct folio *folio, |
| struct rmap_walk_control *rwc) |
| { |
| struct anon_vma *anon_vma = NULL; |
| struct anon_vma *root_anon_vma; |
| unsigned long anon_mapping; |
| |
| rcu_read_lock(); |
| anon_mapping = (unsigned long)READ_ONCE(folio->mapping); |
| if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) |
| goto out; |
| if (!folio_mapped(folio)) |
| goto out; |
| |
| anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); |
| root_anon_vma = READ_ONCE(anon_vma->root); |
| if (down_read_trylock(&root_anon_vma->rwsem)) { |
| /* |
| * If the 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, bool writable) |
| { |
| struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc; |
| int batch, nbatch; |
| |
| arch_tlbbatch_add_mm(&tlb_ubc->arch, mm); |
| tlb_ubc->flush_required = true; |
| |
| /* |
| * Ensure compiler does not re-order the setting of tlb_flush_batched |
| * before the PTE is cleared. |
| */ |
| barrier(); |
| 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. |
| */ |
| nbatch = atomic_cmpxchg(&mm->tlb_flush_batched, batch, 1); |
| if (nbatch != batch) { |
| batch = nbatch; |
| 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) |
| { |
| bool should_defer = false; |
| |
| if (!(flags & TTU_BATCH_FLUSH)) |
| return false; |
| |
| /* If remote CPUs need to be flushed then defer batch the flush */ |
| if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids) |
| should_defer = true; |
| put_cpu(); |
| |
| return should_defer; |
| } |
| |
| /* |
| * Reclaim unmaps pages under the PTL but do not flush the TLB prior to |
| * releasing the PTL if TLB flushes are batched. It's possible for a parallel |
| * operation such as mprotect or munmap to race between reclaim unmapping |
| * the page and flushing the page. If this race occurs, it potentially allows |
| * access to data via a stale TLB entry. Tracking all mm's that have TLB |
| * batching in flight would be expensive during reclaim so instead track |
| * whether TLB batching occurred in the past and if so then do a flush here |
| * if required. This will cost one additional flush per reclaim cycle paid |
| * by the first operation at risk such as mprotect and mumap. |
| * |
| * This must be called under the PTL so that an access to tlb_flush_batched |
| * that is potentially a "reclaim vs mprotect/munmap/etc" race will synchronise |
| * via the PTL. |
| */ |
| void flush_tlb_batched_pending(struct mm_struct *mm) |
| { |
| 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, bool writable) |
| { |
| } |
| |
| static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags) |
| { |
| return false; |
| } |
| #endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */ |
| |
| /* |
| * At what user virtual address is page expected in vma? |
| * Caller should check the page is actually part of the vma. |
| */ |
| unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) |
| { |
| struct folio *folio = page_folio(page); |
| if (folio_test_anon(folio)) { |
| struct anon_vma *page__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 || !page__anon_vma || |
| vma->anon_vma->root != page__anon_vma->root) |
| return -EFAULT; |
| } else if (!vma->vm_file) { |
| return -EFAULT; |
| } else if (vma->vm_file->f_mapping != folio->mapping) { |
| return -EFAULT; |
| } |
| |
| return vma_address(page, vma); |
| } |
| |
| /* |
| * 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; |
| unsigned long 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 referenced = 0; |
| |
| while (page_vma_mapped_walk(&pvmw)) { |
| address = pvmw.address; |
| |
| if ((vma->vm_flags & VM_LOCKED) && |
| (!folio_test_large(folio) || !pvmw.pte)) { |
| /* Restore the mlock which got missed */ |
| mlock_vma_folio(folio, vma, !pvmw.pte); |
| page_vma_mapped_walk_done(&pvmw); |
| pra->vm_flags |= VM_LOCKED; |
| return false; /* To break the loop */ |
| } |
| |
| if (pvmw.pte) { |
| if (lru_gen_enabled() && pte_young(*pvmw.pte) && |
| !(vma->vm_flags & (VM_SEQ_READ | VM_RAND_READ))) { |
| lru_gen_look_around(&pvmw); |
| referenced++; |
| } |
| |
| if (ptep_clear_flush_young_notify(vma, address, |
| pvmw.pte)) { |
| /* |
| * Don't treat a reference through |
| * a sequentially read mapping as such. |
| * 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. |
| */ |
| if (likely(!(vma->vm_flags & VM_SEQ_READ))) |
| referenced++; |
| } |
| } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { |
| if (pmdp_clear_flush_young_notify(vma, address, |
| pvmw.pmd)) |
| referenced++; |
| } else { |
| /* unexpected pmd-mapped folio? */ |
| WARN_ON_ONCE(1); |
| } |
| |
| pra->mapcount--; |
| } |
| |
| 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; |
| |
| if (!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, unsigned long *vm_flags) |
| { |
| int we_locked = 0; |
| 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, |
| }; |
| |
| *vm_flags = 0; |
| if (!pra.mapcount) |
| return 0; |
| |
| if (!folio_raw_mapping(folio)) |
| return 0; |
| |
| if (!is_locked && (!folio_test_anon(folio) || folio_test_ksm(folio))) { |
| we_locked = folio_trylock(folio); |
| if (!we_locked) |
| return 1; |
| } |
| |
| /* |
| * If we are reclaiming on behalf of a cgroup, skip |
| * counting on behalf of references from different |
| * cgroups |
| */ |
| if (memcg) { |
| rwc.invalid_vma = invalid_folio_referenced_vma; |
| } |
| |
| 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, 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 entry; |
| pte_t *pte = pvmw->pte; |
| |
| if (!pte_dirty(*pte) && !pte_write(*pte)) |
| continue; |
| |
| flush_cache_page(vma, address, pte_pfn(*pte)); |
| entry = ptep_clear_flush(vma, address, pte); |
| entry = pte_wrprotect(entry); |
| entry = pte_mkclean(entry); |
| set_pte_at(vma->vm_mm, address, pte, entry); |
| ret = 1; |
| } else { |
| #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| pmd_t *pmd = pvmw->pmd; |
| pmd_t entry; |
| |
| if (!pmd_dirty(*pmd) && !pmd_write(*pmd)) |
| 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 |
| } |
| |
| /* |
| * No need to call mmu_notifier_invalidate_range() as we are |
| * downgrading page table protection not changing it to point |
| * to a new page. |
| * |
| * See Documentation/mm/mmu_notifier.rst |
| */ |
| 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); |
| |
| /** |
| * 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_pgoff_address(pgoff, nr_pages, vma); |
| VM_BUG_ON_VMA(pvmw.address == -EFAULT, vma); |
| |
| return page_vma_mkclean_one(&pvmw); |
| } |
| |
| /** |
| * page_move_anon_rmap - move a page to our anon_vma |
| * @page: the page to move to our anon_vma |
| * @vma: the vma the page belongs to |
| * |
| * When a page belongs exclusively to one process after a COW event, |
| * that page can be moved into the anon_vma that belongs to just that |
| * process, so the rmap code will not search the parent or sibling |
| * processes. |
| */ |
| void page_move_anon_rmap(struct page *page, struct vm_area_struct *vma) |
| { |
| void *anon_vma = vma->anon_vma; |
| struct folio *folio = page_folio(page); |
| |
| VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
| VM_BUG_ON_VMA(!anon_vma, vma); |
| |
| anon_vma += PAGE_MAPPING_ANON; |
| /* |
| * Ensure that anon_vma and the PAGE_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); |
| SetPageAnonExclusive(page); |
| } |
| |
| /** |
| * __page_set_anon_rmap - set up new anonymous rmap |
| * @page: Page or Hugepage to add to rmap |
| * @vma: VM area to add page to. |
| * @address: User virtual address of the mapping |
| * @exclusive: the page is exclusively owned by the current process |
| */ |
| static void __page_set_anon_rmap(struct page *page, |
| struct vm_area_struct *vma, unsigned long address, int exclusive) |
| { |
| struct anon_vma *anon_vma = vma->anon_vma; |
| |
| BUG_ON(!anon_vma); |
| |
| if (PageAnon(page)) |
| goto out; |
| |
| /* |
| * If the page isn't exclusively mapped into this vma, |
| * we must use the _oldest_ possible anon_vma for the |
| * page mapping! |
| */ |
| if (!exclusive) |
| anon_vma = anon_vma->root; |
| |
| /* |
| * page_idle does a lockless/optimistic rmap scan on page->mapping. |
| * Make sure the compiler doesn't split the stores of anon_vma and |
| * the PAGE_MAPPING_ANON type identifier, otherwise the rmap code |
| * could mistake the mapping for a struct address_space and crash. |
| */ |
| anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
| WRITE_ONCE(page->mapping, (struct address_space *) anon_vma); |
| page->index = linear_page_index(vma, address); |
| out: |
| if (exclusive) |
| SetPageAnonExclusive(page); |
| } |
| |
| /** |
| * __page_check_anon_rmap - sanity check anonymous rmap addition |
| * @page: the page to add the mapping to |
| * @vma: the vm area in which the mapping is added |
| * @address: the user virtual address mapped |
| */ |
| static void __page_check_anon_rmap(struct page *page, |
| struct vm_area_struct *vma, unsigned long address) |
| { |
| struct folio *folio = page_folio(page); |
| /* |
| * The page's anon-rmap details (mapping and index) are guaranteed to |
| * be set up correctly at this point. |
| * |
| * We have exclusion against page_add_anon_rmap because the caller |
| * always holds the page locked. |
| * |
| * We have exclusion against page_add_new_anon_rmap because those pages |
| * are initially only visible via the pagetables, and the pte is locked |
| * over the call to page_add_new_anon_rmap. |
| */ |
| VM_BUG_ON_FOLIO(folio_anon_vma(folio)->root != vma->anon_vma->root, |
| folio); |
| VM_BUG_ON_PAGE(page_to_pgoff(page) != linear_page_index(vma, address), |
| page); |
| } |
| |
| /** |
| * page_add_anon_rmap - add pte mapping to an anonymous page |
| * @page: the page to add the mapping to |
| * @vma: the vm area in which the mapping is added |
| * @address: the user virtual address mapped |
| * @flags: the rmap flags |
| * |
| * The caller needs to hold the pte lock, and the page must be locked in |
| * the anon_vma case: to serialize mapping,index checking after setting, |
| * and to ensure that PageAnon is not being upgraded racily to PageKsm |
| * (but PageKsm is never downgraded to PageAnon). |
| */ |
| void page_add_anon_rmap(struct page *page, |
| struct vm_area_struct *vma, unsigned long address, rmap_t flags) |
| { |
| bool compound = flags & RMAP_COMPOUND; |
| bool first; |
| |
| if (unlikely(PageKsm(page))) |
| lock_page_memcg(page); |
| else |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| |
| if (compound) { |
| atomic_t *mapcount; |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| VM_BUG_ON_PAGE(!PageTransHuge(page), page); |
| mapcount = compound_mapcount_ptr(page); |
| first = atomic_inc_and_test(mapcount); |
| } else { |
| first = atomic_inc_and_test(&page->_mapcount); |
| } |
| VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page); |
| VM_BUG_ON_PAGE(!first && PageAnonExclusive(page), page); |
| |
| if (first) { |
| int nr = compound ? thp_nr_pages(page) : 1; |
| /* |
| * We use the irq-unsafe __{inc|mod}_zone_page_stat because |
| * these counters are not modified in interrupt context, and |
| * pte lock(a spinlock) is held, which implies preemption |
| * disabled. |
| */ |
| if (compound) |
| __mod_lruvec_page_state(page, NR_ANON_THPS, nr); |
| __mod_lruvec_page_state(page, NR_ANON_MAPPED, nr); |
| } |
| |
| if (unlikely(PageKsm(page))) |
| unlock_page_memcg(page); |
| |
| /* address might be in next vma when migration races vma_adjust */ |
| else if (first) |
| __page_set_anon_rmap(page, vma, address, |
| !!(flags & RMAP_EXCLUSIVE)); |
| else |
| __page_check_anon_rmap(page, vma, address); |
| |
| mlock_vma_page(page, vma, compound); |
| } |
| |
| /** |
| * page_add_new_anon_rmap - add mapping to a new anonymous page |
| * @page: the page to add the mapping to |
| * @vma: the vm area in which the mapping is added |
| * @address: the user virtual address mapped |
| * |
| * If it's a compound page, it is accounted as a compound page. As the page |
| * is new, it's assume to get mapped exclusively by a single process. |
| * |
| * Same as page_add_anon_rmap but must only be called on *new* pages. |
| * This means the inc-and-test can be bypassed. |
| * Page does not have to be locked. |
| */ |
| void page_add_new_anon_rmap(struct page *page, |
| struct vm_area_struct *vma, unsigned long address) |
| { |
| const bool compound = PageCompound(page); |
| int nr = compound ? thp_nr_pages(page) : 1; |
| |
| VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma); |
| __SetPageSwapBacked(page); |
| if (compound) { |
| VM_BUG_ON_PAGE(!PageTransHuge(page), page); |
| /* increment count (starts at -1) */ |
| atomic_set(compound_mapcount_ptr(page), 0); |
| atomic_set(compound_pincount_ptr(page), 0); |
| |
| __mod_lruvec_page_state(page, NR_ANON_THPS, nr); |
| } else { |
| /* increment count (starts at -1) */ |
| atomic_set(&page->_mapcount, 0); |
| } |
| __mod_lruvec_page_state(page, NR_ANON_MAPPED, nr); |
| __page_set_anon_rmap(page, vma, address, 1); |
| } |
| |
| /** |
| * page_add_file_rmap - add pte mapping to a file page |
| * @page: the page to add the mapping to |
| * @vma: the vm area in which the mapping is added |
| * @compound: charge the page as compound or small page |
| * |
| * The caller needs to hold the pte lock. |
| */ |
| void page_add_file_rmap(struct page *page, |
| struct vm_area_struct *vma, bool compound) |
| { |
| int i, nr = 0; |
| |
| VM_BUG_ON_PAGE(compound && !PageTransHuge(page), page); |
| lock_page_memcg(page); |
| if (compound && PageTransHuge(page)) { |
| int nr_pages = thp_nr_pages(page); |
| |
| for (i = 0; i < nr_pages; i++) { |
| if (atomic_inc_and_test(&page[i]._mapcount)) |
| nr++; |
| } |
| if (!atomic_inc_and_test(compound_mapcount_ptr(page))) |
| goto out; |
| |
| /* |
| * It is racy to ClearPageDoubleMap in page_remove_file_rmap(); |
| * but page lock is held by all page_add_file_rmap() compound |
| * callers, and SetPageDoubleMap below warns if !PageLocked: |
| * so here is a place that DoubleMap can be safely cleared. |
| */ |
| VM_WARN_ON_ONCE(!PageLocked(page)); |
| if (nr == nr_pages && PageDoubleMap(page)) |
| ClearPageDoubleMap(page); |
| |
| if (PageSwapBacked(page)) |
| __mod_lruvec_page_state(page, NR_SHMEM_PMDMAPPED, |
| nr_pages); |
| else |
| __mod_lruvec_page_state(page, NR_FILE_PMDMAPPED, |
| nr_pages); |
| } else { |
| if (PageTransCompound(page) && page_mapping(page)) { |
| VM_WARN_ON_ONCE(!PageLocked(page)); |
| SetPageDoubleMap(compound_head(page)); |
| } |
| if (atomic_inc_and_test(&page->_mapcount)) |
| nr++; |
| } |
| out: |
| if (nr) |
| __mod_lruvec_page_state(page, NR_FILE_MAPPED, nr); |
| unlock_page_memcg(page); |
| |
| mlock_vma_page(page, vma, compound); |
| } |
| |
| static void page_remove_file_rmap(struct page *page, bool compound) |
| { |
| int i, nr = 0; |
| |
| VM_BUG_ON_PAGE(compound && !PageHead(page), page); |
| |
| /* Hugepages are not counted in NR_FILE_MAPPED for now. */ |
| if (unlikely(PageHuge(page))) { |
| /* hugetlb pages are always mapped with pmds */ |
| atomic_dec(compound_mapcount_ptr(page)); |
| return; |
| } |
| |
| /* page still mapped by someone else? */ |
| if (compound && PageTransHuge(page)) { |
| int nr_pages = thp_nr_pages(page); |
| |
| for (i = 0; i < nr_pages; i++) { |
| if (atomic_add_negative(-1, &page[i]._mapcount)) |
| nr++; |
| } |
| if (!atomic_add_negative(-1, compound_mapcount_ptr(page))) |
| goto out; |
| if (PageSwapBacked(page)) |
| __mod_lruvec_page_state(page, NR_SHMEM_PMDMAPPED, |
| -nr_pages); |
| else |
| __mod_lruvec_page_state(page, NR_FILE_PMDMAPPED, |
| -nr_pages); |
| } else { |
| if (atomic_add_negative(-1, &page->_mapcount)) |
| nr++; |
| } |
| out: |
| if (nr) |
| __mod_lruvec_page_state(page, NR_FILE_MAPPED, -nr); |
| } |
| |
| static void page_remove_anon_compound_rmap(struct page *page) |
| { |
| int i, nr; |
| |
| if (!atomic_add_negative(-1, compound_mapcount_ptr(page))) |
| return; |
| |
| /* Hugepages are not counted in NR_ANON_PAGES for now. */ |
| if (unlikely(PageHuge(page))) |
| return; |
| |
| if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) |
| return; |
| |
| __mod_lruvec_page_state(page, NR_ANON_THPS, -thp_nr_pages(page)); |
| |
| if (TestClearPageDoubleMap(page)) { |
| /* |
| * Subpages can be mapped with PTEs too. Check how many of |
| * them are still mapped. |
| */ |
| for (i = 0, nr = 0; i < thp_nr_pages(page); i++) { |
| if (atomic_add_negative(-1, &page[i]._mapcount)) |
| nr++; |
| } |
| |
| /* |
| * Queue the page for deferred split if at least one small |
| * page of the compound page is unmapped, but at least one |
| * small page is still mapped. |
| */ |
| if (nr && nr < thp_nr_pages(page)) |
| deferred_split_huge_page(page); |
| } else { |
| nr = thp_nr_pages(page); |
| } |
| |
| if (nr) |
| __mod_lruvec_page_state(page, NR_ANON_MAPPED, -nr); |
| } |
| |
| /** |
| * page_remove_rmap - take down pte mapping from a page |
| * @page: page to remove mapping from |
| * @vma: the vm area from which the mapping is removed |
| * @compound: uncharge the page as compound or small page |
| * |
| * The caller needs to hold the pte lock. |
| */ |
| void page_remove_rmap(struct page *page, |
| struct vm_area_struct *vma, bool compound) |
| { |
| lock_page_memcg(page); |
| |
| if (!PageAnon(page)) { |
| page_remove_file_rmap(page, compound); |
| goto out; |
| } |
| |
| if (compound) { |
| page_remove_anon_compound_rmap(page); |
| goto out; |
| } |
| |
| /* page still mapped by someone else? */ |
| if (!atomic_add_negative(-1, &page->_mapcount)) |
| goto out; |
| |
| /* |
| * We use the irq-unsafe __{inc|mod}_zone_page_stat because |
| * these counters are not modified in interrupt context, and |
| * pte lock(a spinlock) is held, which implies preemption disabled. |
| */ |
| __dec_lruvec_page_state(page, NR_ANON_MAPPED); |
| |
| if (PageTransCompound(page)) |
| deferred_split_huge_page(compound_head(page)); |
| |
| /* |
| * It would be tidy to reset the PageAnon mapping here, |
| * but that might overwrite a racing page_add_anon_rmap |
| * which increments mapcount after us but sets mapping |
| * before us: so leave the reset to free_unref_page, |
| * and remember that it's only reliable while mapped. |
| * Leaving it set also helps swapoff to reinstate ptes |
| * faster for those pages still in swapcache. |
| */ |
| out: |
| unlock_page_memcg(page); |
| |
| munlock_vma_page(page, vma, compound); |
| } |
| |
| /* |
| * @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); |
| pte_t pteval; |
| struct page *subpage; |
| bool anon_exclusive, ret = true; |
| struct mmu_notifier_range range; |
| enum ttu_flags flags = (enum ttu_flags)(long)arg; |
| |
| /* |
| * When racing against e.g. zap_pte_range() on another cpu, |
| * in between its ptep_get_and_clear_full() and page_remove_rmap(), |
| * try_to_unmap() may return before page_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; |
| |
| if (flags & TTU_SPLIT_HUGE_PMD) |
| split_huge_pmd_address(vma, address, false, folio); |
| |
| /* |
| * 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 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, 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); |
| } |
| mmu_notifier_invalidate_range_start(&range); |
| |
| while (page_vma_mapped_walk(&pvmw)) { |
| /* Unexpected PMD-mapped THP? */ |
| VM_BUG_ON_FOLIO(!pvmw.pte, folio); |
| |
| /* |
| * 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)) { |
| /* Restore the mlock which got missed */ |
| mlock_vma_folio(folio, vma, false); |
| page_vma_mapped_walk_done(&pvmw); |
| ret = false; |
| break; |
| } |
| |
| subpage = folio_page(folio, |
| pte_pfn(*pvmw.pte) - folio_pfn(folio)); |
| address = pvmw.address; |
| anon_exclusive = folio_test_anon(folio) && |
| PageAnonExclusive(subpage); |
| |
| if (folio_test_hugetlb(folio)) { |
| bool anon = folio_test_anon(folio); |
| |
| /* |
| * The try_to_unmap() is only passed a hugetlb page |
| * in the case where the hugetlb page is poisoned. |
| */ |
| VM_BUG_ON_PAGE(!PageHWPoison(subpage), subpage); |
| /* |
| * 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) { |
| VM_BUG_ON(!(flags & TTU_RMAP_LOCKED)); |
| if (!hugetlb_vma_trylock_write(vma)) { |
| page_vma_mapped_walk_done(&pvmw); |
| ret = false; |
| break; |
| } |
| if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) { |
| hugetlb_vma_unlock_write(vma); |
| flush_tlb_range(vma, |
| range.start, range.end); |
| mmu_notifier_invalidate_range(mm, |
| range.start, range.end); |
| /* |
| * The ref count of the PMD page was |
| * dropped which is part of the way map |
| * counting is done for shared PMDs. |
| * Return 'true' here. When there is |
| * no other sharing, huge_pmd_unshare |
| * returns false and we will unmap the |
| * actual page and drop map count |
| * to zero. |
| */ |
| page_vma_mapped_walk_done(&pvmw); |
| break; |
| } |
| hugetlb_vma_unlock_write(vma); |
| } |
| pteval = huge_ptep_clear_flush(vma, address, pvmw.pte); |
| } else { |
| flush_cache_page(vma, address, pte_pfn(*pvmw.pte)); |
| /* 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, pte_dirty(pteval)); |
| } else { |
| pteval = ptep_clear_flush(vma, 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. |
| */ |
| pte_install_uffd_wp_if_needed(vma, address, pvmw.pte, pteval); |
| |
| /* Set the dirty flag on the folio now the pte is gone. */ |
| if (pte_dirty(pteval)) |
| folio_mark_dirty(folio); |
| |
| /* Update high watermark before we lower rss */ |
| update_hiwater_rss(mm); |
| |
| if (PageHWPoison(subpage) && (flags & TTU_HWPOISON)) { |
| 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); |
| } else { |
| dec_mm_counter(mm, mm_counter(&folio->page)); |
| set_pte_at(mm, address, pvmw.pte, pteval); |
| } |
| |
| } else if (pte_unused(pteval) && !userfaultfd_armed(vma)) { |
| /* |
| * The guest indicated that the page content is of no |
| * interest anymore. Simply discard the pte, vmscan |
| * will take care of the rest. |
| * A future reference will then fault in a new zero |
| * page. When userfaultfd is active, we must not drop |
| * this page though, as its main user (postcopy |
| * migration) will not expect userfaults on already |
| * copied pages. |
| */ |
| dec_mm_counter(mm, mm_counter(&folio->page)); |
| /* We have to invalidate as we cleared the pte */ |
| mmu_notifier_invalidate_range(mm, address, |
| address + PAGE_SIZE); |
| } else if (folio_test_anon(folio)) { |
| swp_entry_t entry = { .val = page_private(subpage) }; |
| pte_t swp_pte; |
| /* |
| * Store the swap location in the pte. |
| * See handle_pte_fault() ... |
| */ |
| if (unlikely(folio_test_swapbacked(folio) != |
| folio_test_swapcache(folio))) { |
| WARN_ON_ONCE(1); |
| ret = false; |
| /* We have to invalidate as we cleared the pte */ |
| mmu_notifier_invalidate_range(mm, address, |
| address + PAGE_SIZE); |
| page_vma_mapped_walk_done(&pvmw); |
| break; |
| } |
| |
| /* MADV_FREE page check */ |
| if (!folio_test_swapbacked(folio)) { |
| 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(); |
| |
| /* |
| * The only page refs must be one from isolation |
| * plus the rmap(s) (dropped by discard:). |
| */ |
| if (ref_count == 1 + map_count && |
| !folio_test_dirty(folio)) { |
| /* Invalidate as we cleared the pte */ |
| mmu_notifier_invalidate_range(mm, |
| address, address + PAGE_SIZE); |
| dec_mm_counter(mm, MM_ANONPAGES); |
| goto discard; |
| } |
| |
| /* |
| * If the folio was redirtied, it cannot be |
| * discarded. Remap the page to page table. |
| */ |
| set_pte_at(mm, address, pvmw.pte, pteval); |
| folio_set_swapbacked(folio); |
| ret = false; |
| page_vma_mapped_walk_done(&pvmw); |
| break; |
| } |
| |
| if (swap_duplicate(entry) < 0) { |
| set_pte_at(mm, address, pvmw.pte, pteval); |
| ret = false; |
| page_vma_mapped_walk_done(&pvmw); |
| break; |
| } |
| if (arch_unmap_one(mm, vma, address, pteval) < 0) { |
| swap_free(entry); |
| set_pte_at(mm, address, pvmw.pte, pteval); |
| ret = false; |
| page_vma_mapped_walk_done(&pvmw); |
| break; |
| } |
| |
| /* See page_try_share_anon_rmap(): clear PTE first. */ |
| if (anon_exclusive && |
| page_try_share_anon_rmap(subpage)) { |
| swap_free(entry); |
| set_pte_at(mm, address, pvmw.pte, pteval); |
| ret = false; |
| page_vma_mapped_walk_done(&pvmw); |
| break; |
| } |
| /* |
| * Note: We *don't* remember if the page was mapped |
| * exclusively in the swap pte if the architecture |
| * doesn't support __HAVE_ARCH_PTE_SWP_EXCLUSIVE. In |
| * that case, swapin code has to re-determine that |
| * manually and might detect the page as possibly |
| * shared, for example, if there are other references on |
| * the page or if the page is under writeback. We made |
| * sure that there are no GUP pins on the page that |
| * would rely on it, so for GUP pins this is fine. |
| */ |
| if (list_empty(&mm->mmlist)) { |
| spin_lock(&mmlist_lock); |
| if (list_empty(&mm->mmlist)) |
| list_add(&mm->mmlist, &init_mm.mmlist); |
| spin_unlock(&mmlist_lock); |
| } |
| dec_mm_counter(mm, MM_ANONPAGES); |
| inc_mm_counter(mm, MM_SWAPENTS); |
| swp_pte = swp_entry_to_pte(entry); |
| if (anon_exclusive) |
| swp_pte = pte_swp_mkexclusive(swp_pte); |
| if (pte_soft_dirty(pteval)) |
| swp_pte = pte_swp_mksoft_dirty(swp_pte); |
| if (pte_uffd_wp(pteval)) |
| swp_pte = pte_swp_mkuffd_wp(swp_pte); |
| set_pte_at(mm, address, pvmw.pte, swp_pte); |
| /* Invalidate as we cleared the pte */ |
| mmu_notifier_invalidate_range(mm, address, |
| address + PAGE_SIZE); |
| } else { |
| /* |
| * This is a locked file-backed 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 |
| */ |
| dec_mm_counter(mm, mm_counter_file(&folio->page)); |
| } |
| discard: |
| /* |
| * No need to call mmu_notifier_invalidate_range() it has be |
| * done above for all cases requiring it to happen under page |
| * table lock before mmu_notifier_invalidate_range_end() |
| * |
| * See Documentation/mm/mmu_notifier.rst |
| */ |
| page_remove_rmap(subpage, vma, folio_test_hugetlb(folio)); |
| if (vma->vm_flags & VM_LOCKED) |
| mlock_page_drain_local(); |
| folio_put(folio); |
| } |
| |
| 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 page_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 = try_to_unmap_one, |
| .arg = (void *)flags, |
| .done = page_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); |
| pte_t pteval; |
| struct page *subpage; |
| bool anon_exclusive, ret = true; |
| struct mmu_notifier_range range; |
| enum ttu_flags flags = (enum ttu_flags)(long)arg; |
| |
| /* |
| * When racing against e.g. zap_pte_range() on another cpu, |
| * in between its ptep_get_and_clear_full() and page_remove_rmap(), |
| * try_to_migrate() may return before page_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; |
| |
| /* |
| * unmap_page() in mm/huge_memory.c is the only user of migration with |
| * TTU_SPLIT_HUGE_PMD and it wants to freeze. |
| */ |
| if (flags & TTU_SPLIT_HUGE_PMD) |
| split_huge_pmd_address(vma, address, true, folio); |
| |
| /* |
| * 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, 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); |
| } |
| mmu_notifier_invalidate_range_start(&range); |
| |
| while (page_vma_mapped_walk(&pvmw)) { |
| #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION |
| /* PMD-mapped THP migration entry */ |
| if (!pvmw.pte) { |
| subpage = folio_page(folio, |
| pmd_pfn(*pvmw.pmd) - 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); |
| |
| if (folio_is_zone_device(folio)) { |
| /* |
| * Our PTE is a non-present device exclusive entry and |
| * calculating the subpage as for the common case would |
| * result in an invalid pointer. |
| * |
| * Since only PAGE_SIZE pages can currently be |
| * migrated, just set it to page. This will need to be |
| * changed when hugepage migrations to device private |
| * memory are supported. |
| */ |
| VM_BUG_ON_FOLIO(folio_nr_pages(folio) > 1, folio); |
| subpage = &folio->page; |
| } else { |
| subpage = folio_page(folio, |
| pte_pfn(*pvmw.pte) - folio_pfn(folio)); |
| } |
| address = pvmw.address; |
| 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) { |
| VM_BUG_ON(!(flags & TTU_RMAP_LOCKED)); |
| if (!hugetlb_vma_trylock_write(vma)) { |
| page_vma_mapped_walk_done(&pvmw); |
| ret = false; |
| break; |
| } |
| if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) { |
| hugetlb_vma_unlock_write(vma); |
| flush_tlb_range(vma, |
| range.start, range.end); |
| mmu_notifier_invalidate_range(mm, |
| range.start, range.end); |
| |
| /* |
| * The ref count of the PMD page was |
| * dropped which is part of the way map |
| * counting is done for shared PMDs. |
| * Return 'true' here. When there is |
| * no other sharing, huge_pmd_unshare |
| * returns false and we will unmap the |
| * actual page and drop map count |
| * to zero. |
| */ |
| page_vma_mapped_walk_done(&pvmw); |
| break; |
| } |
| hugetlb_vma_unlock_write(vma); |
| } |
| /* Nuke the hugetlb page table entry */ |
| pteval = huge_ptep_clear_flush(vma, address, pvmw.pte); |
| } else { |
| flush_cache_page(vma, address, pte_pfn(*pvmw.pte)); |
| /* Nuke the page table entry. */ |
| pteval = ptep_clear_flush(vma, address, pvmw.pte); |
| } |
| |
| /* Set the dirty flag on the folio now the pte is gone. */ |
| if (pte_dirty(pteval)) |
| folio_mark_dirty(folio); |
| |
| /* Update high watermark before we lower rss */ |
| update_hiwater_rss(mm); |
| |
| if (folio_is_device_private(folio)) { |
| unsigned long pfn = folio_pfn(folio); |
| swp_entry_t entry; |
| pte_t swp_pte; |
| |
| if (anon_exclusive) |
| BUG_ON(page_try_share_anon_rmap(subpage)); |
| |
| /* |
| * Store the pfn of the page in a special migration |
| * pte. do_swap_page() will wait until the migration |
| * pte is removed and then restart fault handling. |
| */ |
| entry = pte_to_swp_entry(pteval); |
| if (is_writable_device_private_entry(entry)) |
| entry = make_writable_migration_entry(pfn); |
| else if (anon_exclusive) |
| entry = make_readable_exclusive_migration_entry(pfn); |
| else |
| entry = make_readable_migration_entry(pfn); |
| swp_pte = swp_entry_to_pte(entry); |
| |
| /* |
| * pteval maps a zone device page and is therefore |
| * a swap pte. |
| */ |
| if (pte_swp_soft_dirty(pteval)) |
| swp_pte = pte_swp_mksoft_dirty(swp_pte); |
| if (pte_swp_uffd_wp(pteval)) |
| swp_pte = pte_swp_mkuffd_wp(swp_pte); |
| set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte); |
| trace_set_migration_pte(pvmw.address, pte_val(swp_pte), |
| compound_order(&folio->page)); |
| /* |
| * No need to invalidate here it will synchronize on |
| * against the special swap migration pte. |
| */ |
| } else if (PageHWPoison(subpage)) { |
| 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); |
| } else { |
| dec_mm_counter(mm, mm_counter(&folio->page)); |
| set_pte_at(mm, address, pvmw.pte, pteval); |
| } |
| |
| } else if (pte_unused(pteval) && !userfaultfd_armed(vma)) { |
| /* |
| * The guest indicated that the page content is of no |
| * interest anymore. Simply discard the pte, vmscan |
| * will take care of the rest. |
| * A future reference will then fault in a new zero |
| * page. When userfaultfd is active, we must not drop |
| * this page though, as its main user (postcopy |
| * migration) will not expect userfaults on already |
| * copied pages. |
| */ |
| dec_mm_counter(mm, mm_counter(&folio->page)); |
| /* We have to invalidate as we cleared the pte */ |
| mmu_notifier_invalidate_range(mm, address, |
| address + PAGE_SIZE); |
| } else { |
| swp_entry_t entry; |
| pte_t swp_pte; |
| |
| if (arch_unmap_one(mm, vma, address, pteval) < 0) { |
| if (folio_test_hugetlb(folio)) |
| set_huge_pte_at(mm, address, pvmw.pte, pteval); |
| else |
| set_pte_at(mm, address, pvmw.pte, pteval); |
| ret = false; |
| page_vma_mapped_walk_done(&pvmw); |
| break; |
| } |
| VM_BUG_ON_PAGE(pte_write(pteval) && folio_test_anon(folio) && |
| !anon_exclusive, subpage); |
| |
| /* See page_try_share_anon_rmap(): clear PTE first. */ |
| if (anon_exclusive && |
| page_try_share_anon_rmap(subpage)) { |
| if (folio_test_hugetlb(folio)) |
| set_huge_pte_at(mm, address, pvmw.pte, pteval); |
| else |
| 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 (pte_write(pteval)) |
| 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 (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_wp(pteval)) |
| swp_pte = pte_swp_mkuffd_wp(swp_pte); |
| if (folio_test_hugetlb(folio)) |
| set_huge_pte_at(mm, address, pvmw.pte, swp_pte); |
| else |
| set_pte_at(mm, address, pvmw.pte, swp_pte); |
| trace_set_migration_pte(address, pte_val(swp_pte), |
| compound_order(&folio->page)); |
| /* |
| * No need to invalidate here it will synchronize on |
| * against the special swap migration pte. |
| */ |
| } |
| |
| /* |
| * No need to call mmu_notifier_invalidate_range() it has be |
| * done above for all cases requiring it to happen under page |
| * table lock before mmu_notifier_invalidate_range_end() |
| * |
| * See Documentation/mm/mmu_notifier.rst |
| */ |
| page_remove_rmap(subpage, vma, folio_test_hugetlb(folio)); |
| if (vma->vm_flags & VM_LOCKED) |
| mlock_page_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 = page_not_mapped, |
| .anon_lock = folio_lock_anon_vma_read, |
| }; |
| |
| /* |
| * Migration always ignores mlock and only supports TTU_RMAP_LOCKED and |
| * TTU_SPLIT_HUGE_PMD and TTU_SYNC flags. |
| */ |
| if (WARN_ON_ONCE(flags & ~(TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD | |
| TTU_SYNC))) |
| 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 |
| struct make_exclusive_args { |
| struct mm_struct *mm; |
| unsigned long address; |
| void *owner; |
| bool valid; |
| }; |
| |
| static bool page_make_device_exclusive_one(struct folio *folio, |
| struct vm_area_struct *vma, unsigned long address, void *priv) |
| { |
| struct mm_struct *mm = vma->vm_mm; |
| DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0); |
| struct make_exclusive_args *args = priv; |
| pte_t pteval; |
| struct page *subpage; |
| bool ret = true; |
| struct mmu_notifier_range range; |
| swp_entry_t entry; |
| pte_t swp_pte; |
| |
| mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0, vma, |
| vma->vm_mm, address, min(vma->vm_end, |
| address + folio_size(folio)), |
| args->owner); |
| mmu_notifier_invalidate_range_start(&range); |
| |
| while (page_vma_mapped_walk(&pvmw)) { |
| /* Unexpected PMD-mapped THP? */ |
| VM_BUG_ON_FOLIO(!pvmw.pte, folio); |
| |
| if (!pte_present(*pvmw.pte)) { |
| ret = false; |
| page_vma_mapped_walk_done(&pvmw); |
| break; |
| } |
| |
| subpage = folio_page(folio, |
| pte_pfn(*pvmw.pte) - folio_pfn(folio)); |
| address = pvmw.address; |
| |
| /* Nuke the page table entry. */ |
| flush_cache_page(vma, address, pte_pfn(*pvmw.pte)); |
| pteval = ptep_clear_flush(vma, address, pvmw.pte); |
| |
| /* Set the dirty flag on the folio now the pte is gone. */ |
| if (pte_dirty(pteval)) |
| folio_mark_dirty(folio); |
| |
| /* |
| * Check that our target page is still mapped at the expected |
| * address. |
| */ |
| if (args->mm == mm && args->address == address && |
| pte_write(pteval)) |
| args->valid = true; |
| |
| /* |
| * 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 (pte_write(pteval)) |
| entry = make_writable_device_exclusive_entry( |
| page_to_pfn(subpage)); |
| else |
| entry = make_readable_device_exclusive_entry( |
| page_to_pfn(subpage)); |
| swp_pte = swp_entry_to_pte(entry); |
| if (pte_soft_dirty(pteval)) |
| swp_pte = pte_swp_mksoft_dirty(swp_pte); |
| if (pte_uffd_wp(pteval)) |
| swp_pte = pte_swp_mkuffd_wp(swp_pte); |
| |
| set_pte_at(mm, address, pvmw.pte, swp_pte); |
| |
| /* |
| * There is a reference on the page for the swap entry which has |
| * been removed, so shouldn't take another. |
| */ |
| page_remove_rmap(subpage, vma, false); |
| } |
| |
| mmu_notifier_invalidate_range_end(&range); |
| |
| return ret; |
| } |
| |
| /** |
| * folio_make_device_exclusive - Mark the folio exclusively owned by a device. |
| * @folio: The folio to replace page table entries for. |
| * @mm: The mm_struct where the folio is expected to be mapped. |
| * @address: Address where the folio is expected to be mapped. |
| * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier callbacks |
| * |
| * Tries to remove all the page table entries which are mapping this |
| * folio and replace them with special device exclusive swap entries to |
| * grant a device exclusive access to the folio. |
| * |
| * Context: Caller must hold the folio lock. |
| * Return: false if the page is still mapped, or if it could not be unmapped |
| * from the expected address. Otherwise returns true (success). |
| */ |
| static bool folio_make_device_exclusive(struct folio *folio, |
| struct mm_struct *mm, unsigned long address, void *owner) |
| { |
| struct make_exclusive_args args = { |
| .mm = mm, |
| .address = address, |
| .owner = owner, |
| .valid = false, |
| }; |
| struct rmap_walk_control rwc = { |
| .rmap_one = page_make_device_exclusive_one, |
| .done = page_not_mapped, |
| .anon_lock = folio_lock_anon_vma_read, |
| .arg = &args, |
| }; |
| |
| /* |
| * Restrict to anonymous folios for now to avoid potential writeback |
| * issues. |
| */ |
| if (!folio_test_anon(folio)) |
| return false; |
| |
| rmap_walk(folio, &rwc); |
| |
| return args.valid && !folio_mapcount(folio); |
| } |
| |
| /** |
| * make_device_exclusive_range() - Mark a range for exclusive use by a device |
| * @mm: mm_struct of associated target process |
| * @start: start of the region to mark for exclusive device access |
| * @end: end address of region |
| * @pages: returns the pages which were successfully marked for exclusive access |
| * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier to allow filtering |
| * |
| * Returns: number of pages found in the range by GUP. A page is marked for |
| * exclusive access only if the page pointer is non-NULL. |
| * |
| * This function finds ptes mapping page(s) to the given address range, locks |
| * them and replaces mappings with special swap entries preventing userspace CPU |
| * access. On fault these entries are replaced with the original mapping after |
| * calling MMU notifiers. |
| * |
| * 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 page lock and reference after |
| * which point CPU access to the page will revoke the exclusive access. |
| */ |
| int make_device_exclusive_range(struct mm_struct *mm, unsigned long start, |
| unsigned long end, struct page **pages, |
| void *owner) |
| { |
| long npages = (end - start) >> PAGE_SHIFT; |
| long i; |
| |
| npages = get_user_pages_remote(mm, start, npages, |
| FOLL_GET | FOLL_WRITE | FOLL_SPLIT_PMD, |
| pages, NULL, NULL); |
| if (npages < 0) |
| return npages; |
| |
| for (i = 0; i < npages; i++, start += PAGE_SIZE) { |
| struct folio *folio = page_folio(pages[i]); |
| if (PageTail(pages[i]) || !folio_trylock(folio)) { |
| folio_put(folio); |
| pages[i] = NULL; |
| continue; |
| } |
| |
| if (!folio_make_device_exclusive(folio, mm, start, owner)) { |
| folio_unlock(folio); |
| folio_put(folio); |
| pages[i] = NULL; |
| } |
| } |
| |
| return npages; |
| } |
| EXPORT_SYMBOL_GPL(make_device_exclusive_range); |
| #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(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 page_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 |
| * @page: the page to be handled |
| * @rwc: control variable according to each walk type |
| * |
| * Find all the mappings of a page using the mapping pointer and the vma chains |
| * contained in the anon_vma struct it points to. |
| */ |
| 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; |
| |
| 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_vma_interval_tree_foreach(avc, &anon_vma->rb_root, |
| pgoff_start, pgoff_end) { |
| struct vm_area_struct *vma = avc->vma; |
| unsigned long address = vma_address(&folio->page, vma); |
| |
| VM_BUG_ON_VMA(address == -EFAULT, vma); |
| cond_resched(); |
| |
| if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) |
| continue; |
| |
| if (!rwc->rmap_one(folio, vma, address, rwc->arg)) |
| break; |
| if (rwc->done && rwc->done(folio)) |
| break; |
| } |
| |
| if (!locked) |
| anon_vma_unlock_read(anon_vma); |
| } |
| |
| /* |
| * rmap_walk_file - do something to file page using the object-based rmap method |
| * @page: the page to be handled |
| * @rwc: control variable according to each walk type |
| * |
| * Find all the mappings of a page using the mapping pointer and the vma chains |
| * contained in the address_space struct it points to. |
| */ |
| static void rmap_walk_file(struct folio *folio, |
| struct rmap_walk_control *rwc, bool locked) |
| { |
| struct address_space *mapping = folio_mapping(folio); |
| pgoff_t pgoff_start, pgoff_end; |
| struct vm_area_struct *vma; |
| |
| /* |
| * The page lock not only makes sure that page->mapping cannot |
| * suddenly be NULLified by truncation, it makes sure that the |
| * structure at mapping cannot be freed and reused yet, |
| * so we can safely take mapping->i_mmap_rwsem. |
| */ |
| VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
| |
| if (!mapping) |
| return; |
| |
| pgoff_start = folio_pgoff(folio); |
| pgoff_end = pgoff_start + folio_nr_pages(folio) - 1; |
| if (!locked) { |
| if (i_mmap_trylock_read(mapping)) |
| goto lookup; |
| |
| if (rwc->try_lock) { |
| rwc->contended = true; |
| return; |
| } |
| |
| i_mmap_lock_read(mapping); |
| } |
| lookup: |
| vma_interval_tree_foreach(vma, &mapping->i_mmap, |
| pgoff_start, pgoff_end) { |
| unsigned long address = vma_address(&folio->page, vma); |
| |
| VM_BUG_ON_VMA(address == -EFAULT, vma); |
| cond_resched(); |
| |
| if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) |
| continue; |
| |
| if (!rwc->rmap_one(folio, vma, address, rwc->arg)) |
| goto done; |
| if (rwc->done && rwc->done(folio)) |
| goto done; |
| } |
| |
| done: |
| if (!locked) |
| i_mmap_unlock_read(mapping); |
| } |
| |
| 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. |
| * |
| * RMAP_COMPOUND is ignored. |
| */ |
| void hugepage_add_anon_rmap(struct page *page, struct vm_area_struct *vma, |
| unsigned long address, rmap_t flags) |
| { |
| struct anon_vma *anon_vma = vma->anon_vma; |
| int first; |
| |
| BUG_ON(!PageLocked(page)); |
| BUG_ON(!anon_vma); |
| /* address might be in next vma when migration races vma_adjust */ |
| first = atomic_inc_and_test(compound_mapcount_ptr(page)); |
| VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page); |
| VM_BUG_ON_PAGE(!first && PageAnonExclusive(page), page); |
| if (first) |
| __page_set_anon_rmap(page, vma, address, |
| !!(flags & RMAP_EXCLUSIVE)); |
| } |
| |
| void hugepage_add_new_anon_rmap(struct page *page, |
| struct vm_area_struct *vma, unsigned long address) |
| { |
| BUG_ON(address < vma->vm_start || address >= vma->vm_end); |
| atomic_set(compound_mapcount_ptr(page), 0); |
| atomic_set(compound_pincount_ptr(page), 0); |
| |
| __page_set_anon_rmap(page, vma, address, 1); |
| } |
| #endif /* CONFIG_HUGETLB_PAGE */ |