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- /*
- * mm/rmap.c - physical to virtual reverse mappings
- *
- * Copyright 2001, Rik van Riel <[email protected]>
- * 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 <[email protected]> 2001
- * File methods by Dave McCracken <[email protected]> 2003, 2004
- * Anonymous methods by Andrea Arcangeli <[email protected]> 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)
- * 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)
- * 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>
- #undef CREATE_TRACE_POINTS
- #include <trace/hooks/mm.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) {
- trace_android_vh_look_around(&pvmw, folio, vma, &referenced);
- if (lru_gen_enabled() && pte_young(*pvmw.pte)) {
- lru_gen_look_around(&pvmw);
- referenced++;
- }
- if (ptep_clear_flush_young_notify(vma, address,
- pvmw.pte))
- 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;
- /*
- * 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, 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,
- .invalid_vma = invalid_folio_referenced_vma,
- };
- *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;
- }
- rmap_walk(folio, &rwc);
- *vm_flags = pra.vm_flags;
- if (we_locked)
- folio_unlock(folio);
- return rwc.contended ? -1 : pra.referenced;
- }
- EXPORT_SYMBOL_GPL(folio_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);
- trace_android_vh_page_add_new_anon_rmap(page, vma, address);
- }
- /**
- * 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);
- trace_android_vh_try_to_unmap_one(folio, vma, address, arg, ret);
- 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 */
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