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linux/mm/rmap.c
Matthew Wilcox (Oracle) 4dc7d37370 remove references to page->flags in documentation 
Mostly rewording, but remove entirely the copy of page_fixed_fake_head()
in the documentation; we can refer people to the actual source if
necessary.

Link: https://lkml.kernel.org/r/20240326171045.410737-10-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-04-25 20:56:15 -07:00

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/*
* 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)
* folio_lock
* hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share, see hugetlbfs below)
* vma_start_write
* mapping->i_mmap_rwsem
* anon_vma->rwsem
* mm->page_table_lock or pte_lock
* swap_lock (in swap_duplicate, swap_info_get)
* mmlist_lock (in mmput, drain_mmlist and others)
* mapping->private_lock (in block_dirty_folio)
* 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)
* folio_lock
*/
#include <linux/mm.h>
#include <linux/sched/mm.h>
#include <linux/sched/task.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/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_expand(), vma_merge(), __split_vma(),
* copy_vma() and anon_vma_fork(). The first four 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 num_active_vmas 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 folio_remove_rmap_*()
* the best this function can do is return a refcount increased anon_vma
* that might have been relevant to this page.
*
* The page might have been remapped to a different anon_vma or the anon_vma
* returned may already be freed (and even reused).
*
* In case it was remapped to a different anon_vma, the new anon_vma will be a
* child of the old anon_vma, and the anon_vma lifetime rules will therefore
* ensure that any anon_vma obtained from the page will still be valid for as
* long as we observe 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
* folio_remove_rmap_*() that the anon_vma pointer from page->mapping is valid
* if there is a mapcount, we can dereference the anon_vma after observing
* those.
*
* NOTE: the caller should normally hold folio lock when calling this. If
* not, the caller needs to double check the anon_vma didn't change after
* taking the anon_vma lock for either read or write (UFFDIO_MOVE can modify it
* concurrently without folio lock protection). See folio_lock_anon_vma_read()
* which has already covered that, and comment above remap_pages().
*/
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;
retry:
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)) {
/*
* folio_move_anon_rmap() might have changed the anon_vma as we
* might not hold the folio lock here.
*/
if (unlikely((unsigned long)READ_ONCE(folio->mapping) !=
anon_mapping)) {
up_read(&root_anon_vma->rwsem);
rcu_read_unlock();
goto retry;
}
/*
* 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);
/*
* folio_move_anon_rmap() might have changed the anon_vma as we might
* not hold the folio lock here.
*/
if (unlikely((unsigned long)READ_ONCE(folio->mapping) !=
anon_mapping)) {
anon_vma_unlock_read(anon_vma);
put_anon_vma(anon_vma);
anon_vma = NULL;
goto retry;
}
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 = &current->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 = &current->tlb_ubc;
if (tlb_ubc->writable)
try_to_unmap_flush();
}
/*
* Bits 0-14 of mm->tlb_flush_batched record pending generations.
* Bits 16-30 of mm->tlb_flush_batched bit record flushed generations.
*/
#define TLB_FLUSH_BATCH_FLUSHED_SHIFT 16
#define TLB_FLUSH_BATCH_PENDING_MASK \
((1 << (TLB_FLUSH_BATCH_FLUSHED_SHIFT - 1)) - 1)
#define TLB_FLUSH_BATCH_PENDING_LARGE \
(TLB_FLUSH_BATCH_PENDING_MASK / 2)
static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval,
unsigned long uaddr)
{
struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
int batch;
bool writable = pte_dirty(pteval);
if (!pte_accessible(mm, pteval))
return;
arch_tlbbatch_add_pending(&tlb_ubc->arch, mm, uaddr);
tlb_ubc->flush_required = true;
/*
* Ensure compiler does not re-order the setting of tlb_flush_batched
* before the PTE is cleared.
*/
barrier();
batch = atomic_read(&mm->tlb_flush_batched);
retry:
if ((batch & TLB_FLUSH_BATCH_PENDING_MASK) > TLB_FLUSH_BATCH_PENDING_LARGE) {
/*
* Prevent `pending' from catching up with `flushed' because of
* overflow. Reset `pending' and `flushed' to be 1 and 0 if
* `pending' becomes large.
*/
if (!atomic_try_cmpxchg(&mm->tlb_flush_batched, &batch, 1))
goto retry;
} else {
atomic_inc(&mm->tlb_flush_batched);
}
/*
* If the PTE was dirty then it's best to assume it's writable. The
* caller must use try_to_unmap_flush_dirty() or try_to_unmap_flush()
* before the page is queued for IO.
*/
if (writable)
tlb_ubc->writable = true;
}
/*
* Returns true if the TLB flush should be deferred to the end of a batch of
* unmap operations to reduce IPIs.
*/
static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
{
if (!(flags & TTU_BATCH_FLUSH))
return false;
return arch_tlbbatch_should_defer(mm);
}
/*
* Reclaim unmaps pages under the PTL but do not flush the TLB prior to
* releasing the PTL if TLB flushes are batched. It's possible for a parallel
* operation such as mprotect or munmap to race between reclaim unmapping
* the page and flushing the page. If this race occurs, it potentially allows
* access to data via a stale TLB entry. Tracking all mm's that have TLB
* batching in flight would be expensive during reclaim so instead track
* whether TLB batching occurred in the past and if so then do a flush here
* if required. This will cost one additional flush per reclaim cycle paid
* by the first operation at risk such as mprotect and mumap.
*
* This must be called under the PTL so that an access to tlb_flush_batched
* that is potentially a "reclaim vs mprotect/munmap/etc" race will synchronise
* via the PTL.
*/
void flush_tlb_batched_pending(struct mm_struct *mm)
{
int batch = atomic_read(&mm->tlb_flush_batched);
int pending = batch & TLB_FLUSH_BATCH_PENDING_MASK;
int flushed = batch >> TLB_FLUSH_BATCH_FLUSHED_SHIFT;
if (pending != flushed) {
arch_flush_tlb_batched_pending(mm);
/*
* If the new TLB flushing is pending during flushing, leave
* mm->tlb_flush_batched as is, to avoid losing flushing.
*/
atomic_cmpxchg(&mm->tlb_flush_batched, batch,
pending | (pending << TLB_FLUSH_BATCH_FLUSHED_SHIFT));
}
}
#else
static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval,
unsigned long uaddr)
{
}
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;
unsigned long start = address, ptes = 0;
while (page_vma_mapped_walk(&pvmw)) {
address = pvmw.address;
if (vma->vm_flags & VM_LOCKED) {
if (!folio_test_large(folio) || !pvmw.pte) {
/* Restore the mlock which got missed */
mlock_vma_folio(folio, vma);
page_vma_mapped_walk_done(&pvmw);
pra->vm_flags |= VM_LOCKED;
return false; /* To break the loop */
}
/*
* For large folio fully mapped to VMA, will
* be handled after the pvmw loop.
*
* For large folio cross VMA boundaries, it's
* expected to be picked by page reclaim. But
* should skip reference of pages which are in
* the range of VM_LOCKED vma. As page reclaim
* should just count the reference of pages out
* the range of VM_LOCKED vma.
*/
ptes++;
pra->mapcount--;
continue;
}
if (pvmw.pte) {
if (lru_gen_enabled() &&
pte_young(ptep_get(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 ((vma->vm_flags & VM_LOCKED) &&
folio_test_large(folio) &&
folio_within_vma(folio, vma)) {
unsigned long s_align, e_align;
s_align = ALIGN_DOWN(start, PMD_SIZE);
e_align = ALIGN_DOWN(start + folio_size(folio) - 1, PMD_SIZE);
/* folio doesn't cross page table boundary and fully mapped */
if ((s_align == e_align) && (ptes == folio_nr_pages(folio))) {
/* Restore the mlock which got missed */
mlock_vma_folio(folio, vma);
pra->vm_flags |= VM_LOCKED;
return false; /* To break the loop */
}
}
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;
}
static int page_vma_mkclean_one(struct page_vma_mapped_walk *pvmw)
{
int cleaned = 0;
struct vm_area_struct *vma = pvmw->vma;
struct mmu_notifier_range range;
unsigned long address = pvmw->address;
/*
* We have to assume the worse case ie pmd for invalidation. Note that
* the folio can not be freed from this function.
*/
mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_PAGE, 0,
vma->vm_mm, address, vma_address_end(pvmw));
mmu_notifier_invalidate_range_start(&range);
while (page_vma_mapped_walk(pvmw)) {
int ret = 0;
address = pvmw->address;
if (pvmw->pte) {
pte_t *pte = pvmw->pte;
pte_t entry = ptep_get(pte);
if (!pte_dirty(entry) && !pte_write(entry))
continue;
flush_cache_page(vma, address, pte_pfn(entry));
entry = ptep_clear_flush(vma, address, pte);
entry = pte_wrprotect(entry);
entry = pte_mkclean(entry);
set_pte_at(vma->vm_mm, address, pte, entry);
ret = 1;
} else {
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
pmd_t *pmd = pvmw->pmd;
pmd_t entry;
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
}
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);
}
int folio_total_mapcount(const struct folio *folio)
{
int mapcount = folio_entire_mapcount(folio);
int nr_pages;
int i;
/* In the common case, avoid the loop when no pages mapped by PTE */
if (folio_nr_pages_mapped(folio) == 0)
return mapcount;
/*
* Add all the PTE mappings of those pages mapped by PTE.
* Limit the loop to folio_nr_pages_mapped()?
* Perhaps: given all the raciness, that may be a good or a bad idea.
*/
nr_pages = folio_nr_pages(folio);
for (i = 0; i < nr_pages; i++)
mapcount += atomic_read(&folio_page(folio, i)->_mapcount);
/* But each of those _mapcounts was based on -1 */
mapcount += nr_pages;
return mapcount;
}
static __always_inline unsigned int __folio_add_rmap(struct folio *folio,
struct page *page, int nr_pages, enum rmap_level level,
int *nr_pmdmapped)
{
atomic_t *mapped = &folio->_nr_pages_mapped;
int first, nr = 0;
__folio_rmap_sanity_checks(folio, page, nr_pages, level);
switch (level) {
case RMAP_LEVEL_PTE:
do {
first = atomic_inc_and_test(&page->_mapcount);
if (first && folio_test_large(folio)) {
first = atomic_inc_return_relaxed(mapped);
first = (first < ENTIRELY_MAPPED);
}
if (first)
nr++;
} while (page++, --nr_pages > 0);
break;
case RMAP_LEVEL_PMD:
first = atomic_inc_and_test(&folio->_entire_mapcount);
if (first) {
nr = atomic_add_return_relaxed(ENTIRELY_MAPPED, mapped);
if (likely(nr < ENTIRELY_MAPPED + ENTIRELY_MAPPED)) {
*nr_pmdmapped = folio_nr_pages(folio);
nr = *nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
/* Raced ahead of a remove and another add? */
if (unlikely(nr < 0))
nr = 0;
} else {
/* Raced ahead of a remove of ENTIRELY_MAPPED */
nr = 0;
}
}
break;
}
return nr;
}
/**
* folio_move_anon_rmap - move a folio to our anon_vma
* @folio: The folio to move to our anon_vma
* @vma: The vma the folio belongs to
*
* When a folio belongs exclusively to one process after a COW event,
* that folio can be moved into the anon_vma that belongs to just that
* process, so the rmap code will not search the parent or sibling processes.
*/
void folio_move_anon_rmap(struct folio *folio, struct vm_area_struct *vma)
{
void *anon_vma = vma->anon_vma;
VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
VM_BUG_ON_VMA(!anon_vma, vma);
anon_vma += 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);
}
/**
* __folio_set_anon - set up a new anonymous rmap for a folio
* @folio: The folio to set up the new anonymous rmap for.
* @vma: VM area to add the folio to.
* @address: User virtual address of the mapping
* @exclusive: Whether the folio is exclusive to the process.
*/
static void __folio_set_anon(struct folio *folio, struct vm_area_struct *vma,
unsigned long address, bool exclusive)
{
struct anon_vma *anon_vma = vma->anon_vma;
BUG_ON(!anon_vma);
/*
* If the folio isn't exclusive to this vma, we must use the _oldest_
* possible anon_vma for the folio mapping!
*/
if (!exclusive)
anon_vma = anon_vma->root;
/*
* page_idle does a lockless/optimistic rmap scan on folio->mapping.
* Make sure the compiler doesn't split the stores of anon_vma and
* the 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(folio->mapping, (struct address_space *) anon_vma);
folio->index = linear_page_index(vma, address);
}
/**
* __page_check_anon_rmap - sanity check anonymous rmap addition
* @folio: The folio containing @page.
* @page: the page to check the mapping of
* @vma: the vm area in which the mapping is added
* @address: the user virtual address mapped
*/
static void __page_check_anon_rmap(struct folio *folio, struct page *page,
struct vm_area_struct *vma, unsigned long address)
{
/*
* The page's anon-rmap details (mapping and index) are guaranteed to
* be set up correctly at this point.
*
* We have exclusion against folio_add_anon_rmap_*() because the caller
* always holds the page locked.
*
* We have exclusion against folio_add_new_anon_rmap because those pages
* are initially only visible via the pagetables, and the pte is locked
* over the call to folio_add_new_anon_rmap.
*/
VM_BUG_ON_FOLIO(folio_anon_vma(folio)->root != vma->anon_vma->root,
folio);
VM_BUG_ON_PAGE(page_to_pgoff(page) != linear_page_index(vma, address),
page);
}
static __always_inline void __folio_add_anon_rmap(struct folio *folio,
struct page *page, int nr_pages, struct vm_area_struct *vma,
unsigned long address, rmap_t flags, enum rmap_level level)
{
int i, nr, nr_pmdmapped = 0;
nr = __folio_add_rmap(folio, page, nr_pages, level, &nr_pmdmapped);
if (nr_pmdmapped)
__lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr_pmdmapped);
if (nr)
__lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr);
if (unlikely(!folio_test_anon(folio))) {
VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio);
/*
* For a PTE-mapped large folio, we only know that the single
* PTE is exclusive. Further, __folio_set_anon() might not get
* folio->index right when not given the address of the head
* page.
*/
VM_WARN_ON_FOLIO(folio_test_large(folio) &&
level != RMAP_LEVEL_PMD, folio);
__folio_set_anon(folio, vma, address,
!!(flags & RMAP_EXCLUSIVE));
} else if (likely(!folio_test_ksm(folio))) {
__page_check_anon_rmap(folio, page, vma, address);
}
if (flags & RMAP_EXCLUSIVE) {
switch (level) {
case RMAP_LEVEL_PTE:
for (i = 0; i < nr_pages; i++)
SetPageAnonExclusive(page + i);
break;
case RMAP_LEVEL_PMD:
SetPageAnonExclusive(page);
break;
}
}
for (i = 0; i < nr_pages; i++) {
struct page *cur_page = page + i;
/* While PTE-mapping a THP we have a PMD and a PTE mapping. */
VM_WARN_ON_FOLIO((atomic_read(&cur_page->_mapcount) > 0 ||
(folio_test_large(folio) &&
folio_entire_mapcount(folio) > 1)) &&
PageAnonExclusive(cur_page), folio);
}
/*
* For large folio, only mlock it if it's fully mapped to VMA. It's
* not easy to check whether the large folio is fully mapped to VMA
* here. Only mlock normal 4K folio and leave page reclaim to handle
* large folio.
*/
if (!folio_test_large(folio))
mlock_vma_folio(folio, vma);
}
/**
* folio_add_anon_rmap_ptes - add PTE mappings to a page range of an anon folio
* @folio: The folio to add the mappings to
* @page: The first page to add
* @nr_pages: The number of pages which will be mapped
* @vma: The vm area in which the mappings are added
* @address: The user virtual address of the first page to map
* @flags: The rmap flags
*
* The page range of folio is defined by [first_page, first_page + nr_pages)
*
* The caller needs to hold the page table lock, and the page must be locked in
* the anon_vma case: to serialize mapping,index checking after setting,
* and to ensure that an anon folio is not being upgraded racily to a KSM folio
* (but KSM folios are never downgraded).
*/
void folio_add_anon_rmap_ptes(struct folio *folio, struct page *page,
int nr_pages, struct vm_area_struct *vma, unsigned long address,
rmap_t flags)
{
__folio_add_anon_rmap(folio, page, nr_pages, vma, address, flags,
RMAP_LEVEL_PTE);
}
/**
* folio_add_anon_rmap_pmd - add a PMD mapping to a page range of an anon folio
* @folio: The folio to add the mapping to
* @page: The first page to add
* @vma: The vm area in which the mapping is added
* @address: The user virtual address of the first page to map
* @flags: The rmap flags
*
* The page range of folio is defined by [first_page, first_page + HPAGE_PMD_NR)
*
* The caller needs to hold the page table lock, and the page must be locked in
* the anon_vma case: to serialize mapping,index checking after setting.
*/
void folio_add_anon_rmap_pmd(struct folio *folio, struct page *page,
struct vm_area_struct *vma, unsigned long address, rmap_t flags)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
__folio_add_anon_rmap(folio, page, HPAGE_PMD_NR, vma, address, flags,
RMAP_LEVEL_PMD);
#else
WARN_ON_ONCE(true);
#endif
}
/**
* folio_add_new_anon_rmap - Add mapping to a new anonymous folio.
* @folio: The folio to add the mapping to.
* @vma: the vm area in which the mapping is added
* @address: the user virtual address mapped
*
* Like folio_add_anon_rmap_*() but must only be called on *new* folios.
* This means the inc-and-test can be bypassed.
* The folio does not have to be locked.
*
* If the folio is pmd-mappable, it is accounted as a THP. As the folio
* is new, it's assumed to be mapped exclusively by a single process.
*/
void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
unsigned long address)
{
int nr = folio_nr_pages(folio);
VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
VM_BUG_ON_VMA(address < vma->vm_start ||
address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
__folio_set_swapbacked(folio);
__folio_set_anon(folio, vma, address, true);
if (likely(!folio_test_large(folio))) {
/* increment count (starts at -1) */
atomic_set(&folio->_mapcount, 0);
SetPageAnonExclusive(&folio->page);
} else if (!folio_test_pmd_mappable(folio)) {
int i;
for (i = 0; i < nr; i++) {
struct page *page = folio_page(folio, i);
/* increment count (starts at -1) */
atomic_set(&page->_mapcount, 0);
SetPageAnonExclusive(page);
}
atomic_set(&folio->_nr_pages_mapped, nr);
} else {
/* increment count (starts at -1) */
atomic_set(&folio->_entire_mapcount, 0);
atomic_set(&folio->_nr_pages_mapped, ENTIRELY_MAPPED);
SetPageAnonExclusive(&folio->page);
__lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr);
}
__lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr);
}
static __always_inline void __folio_add_file_rmap(struct folio *folio,
struct page *page, int nr_pages, struct vm_area_struct *vma,
enum rmap_level level)
{
int nr, nr_pmdmapped = 0;
VM_WARN_ON_FOLIO(folio_test_anon(folio), folio);
nr = __folio_add_rmap(folio, page, nr_pages, level, &nr_pmdmapped);
if (nr_pmdmapped)
__lruvec_stat_mod_folio(folio, folio_test_swapbacked(folio) ?
NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED, nr_pmdmapped);
if (nr)
__lruvec_stat_mod_folio(folio, NR_FILE_MAPPED, nr);
/* See comments in folio_add_anon_rmap_*() */
if (!folio_test_large(folio))
mlock_vma_folio(folio, vma);
}
/**
* folio_add_file_rmap_ptes - add PTE mappings to a page range of a folio
* @folio: The folio to add the mappings to
* @page: The first page to add
* @nr_pages: The number of pages that will be mapped using PTEs
* @vma: The vm area in which the mappings are added
*
* The page range of the folio is defined by [page, page + nr_pages)
*
* The caller needs to hold the page table lock.
*/
void folio_add_file_rmap_ptes(struct folio *folio, struct page *page,
int nr_pages, struct vm_area_struct *vma)
{
__folio_add_file_rmap(folio, page, nr_pages, vma, RMAP_LEVEL_PTE);
}
/**
* folio_add_file_rmap_pmd - add a PMD mapping to a page range of a folio
* @folio: The folio to add the mapping to
* @page: The first page to add
* @vma: The vm area in which the mapping is added
*
* The page range of the folio is defined by [page, page + HPAGE_PMD_NR)
*
* The caller needs to hold the page table lock.
*/
void folio_add_file_rmap_pmd(struct folio *folio, struct page *page,
struct vm_area_struct *vma)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
__folio_add_file_rmap(folio, page, HPAGE_PMD_NR, vma, RMAP_LEVEL_PMD);
#else
WARN_ON_ONCE(true);
#endif
}
static __always_inline void __folio_remove_rmap(struct folio *folio,
struct page *page, int nr_pages, struct vm_area_struct *vma,
enum rmap_level level)
{
atomic_t *mapped = &folio->_nr_pages_mapped;
int last, nr = 0, nr_pmdmapped = 0;
enum node_stat_item idx;
__folio_rmap_sanity_checks(folio, page, nr_pages, level);
switch (level) {
case RMAP_LEVEL_PTE:
do {
last = atomic_add_negative(-1, &page->_mapcount);
if (last && folio_test_large(folio)) {
last = atomic_dec_return_relaxed(mapped);
last = (last < ENTIRELY_MAPPED);
}
if (last)
nr++;
} while (page++, --nr_pages > 0);
break;
case RMAP_LEVEL_PMD:
last = atomic_add_negative(-1, &folio->_entire_mapcount);
if (last) {
nr = atomic_sub_return_relaxed(ENTIRELY_MAPPED, mapped);
if (likely(nr < ENTIRELY_MAPPED)) {
nr_pmdmapped = folio_nr_pages(folio);
nr = nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
/* Raced ahead of another remove and an add? */
if (unlikely(nr < 0))
nr = 0;
} else {
/* An add of ENTIRELY_MAPPED raced ahead */
nr = 0;
}
}
break;
}
if (nr_pmdmapped) {
if (folio_test_anon(folio))
idx = NR_ANON_THPS;
else if (folio_test_swapbacked(folio))
idx = NR_SHMEM_PMDMAPPED;
else
idx = NR_FILE_PMDMAPPED;
__lruvec_stat_mod_folio(folio, idx, -nr_pmdmapped);
}
if (nr) {
idx = folio_test_anon(folio) ? NR_ANON_MAPPED : NR_FILE_MAPPED;
__lruvec_stat_mod_folio(folio, idx, -nr);
/*
* Queue anon large folio for deferred split if at least one
* page of the folio is unmapped and at least one page
* is still mapped.
*/
if (folio_test_large(folio) && folio_test_anon(folio))
if (level == RMAP_LEVEL_PTE || nr < nr_pmdmapped)
deferred_split_folio(folio);
}
/*
* It would be tidy to reset folio_test_anon mapping when fully
* unmapped, but that might overwrite a racing folio_add_anon_rmap_*()
* which increments mapcount after us but sets mapping before us:
* so leave the reset to free_pages_prepare, and remember that
* it's only reliable while mapped.
*/
munlock_vma_folio(folio, vma);
}
/**
* folio_remove_rmap_ptes - remove PTE mappings from a page range of a folio
* @folio: The folio to remove the mappings from
* @page: The first page to remove
* @nr_pages: The number of pages that will be removed from the mapping
* @vma: The vm area from which the mappings are removed
*
* The page range of the folio is defined by [page, page + nr_pages)
*
* The caller needs to hold the page table lock.
*/
void folio_remove_rmap_ptes(struct folio *folio, struct page *page,
int nr_pages, struct vm_area_struct *vma)
{
__folio_remove_rmap(folio, page, nr_pages, vma, RMAP_LEVEL_PTE);
}
/**
* folio_remove_rmap_pmd - remove a PMD mapping from a page range of a folio
* @folio: The folio to remove the mapping from
* @page: The first page to remove
* @vma: The vm area from which the mapping is removed
*
* The page range of the folio is defined by [page, page + HPAGE_PMD_NR)
*
* The caller needs to hold the page table lock.
*/
void folio_remove_rmap_pmd(struct folio *folio, struct page *page,
struct vm_area_struct *vma)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
__folio_remove_rmap(folio, page, HPAGE_PMD_NR, vma, RMAP_LEVEL_PMD);
#else
WARN_ON_ONCE(true);
#endif
}
/*
* @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;
unsigned long pfn;
unsigned long hsz = 0;
/*
* When racing against e.g. zap_pte_range() on another cpu,
* in between its ptep_get_and_clear_full() and folio_remove_rmap_*(),
* try_to_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->vm_mm,
address, range.end);
if (folio_test_hugetlb(folio)) {
/*
* If sharing is possible, start and end will be adjusted
* accordingly.
*/
adjust_range_if_pmd_sharing_possible(vma, &range.start,
&range.end);
/* We need the huge page size for set_huge_pte_at() */
hsz = huge_page_size(hstate_vma(vma));
}
mmu_notifier_invalidate_range_start(&range);
while (page_vma_mapped_walk(&pvmw)) {
/* 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 */
if (!folio_test_large(folio))
mlock_vma_folio(folio, vma);
page_vma_mapped_walk_done(&pvmw);
ret = false;
break;
}
pfn = pte_pfn(ptep_get(pvmw.pte));
subpage = folio_page(folio, pfn - 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);
/*
* 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, pfn);
/* Nuke the page table entry. */
if (should_defer_flush(mm, flags)) {
/*
* We clear the PTE but do not flush so potentially
* a remote CPU could still be writing to the folio.
* If the entry was previously clean then the
* architecture must guarantee that a clear->dirty
* transition on a cached TLB entry is written through
* and traps if the PTE is unmapped.
*/
pteval = ptep_get_and_clear(mm, address, pvmw.pte);
set_tlb_ubc_flush_pending(mm, pteval, address);
} 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,
hsz);
} else {
dec_mm_counter(mm, mm_counter(folio));
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));
} else if (folio_test_anon(folio)) {
swp_entry_t entry = page_swap_entry(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;
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)) {
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 folio_try_share_anon_rmap(): clear PTE first. */
if (anon_exclusive &&
folio_try_share_anon_rmap_pte(folio, subpage)) {
swap_free(entry);
set_pte_at(mm, address, pvmw.pte, pteval);
ret = false;
page_vma_mapped_walk_done(&pvmw);
break;
}
if (list_empty(&mm->mmlist)) {
spin_lock(&mmlist_lock);
if (list_empty(&mm->mmlist))
list_add(&mm->mmlist, &init_mm.mmlist);
spin_unlock(&mmlist_lock);
}
dec_mm_counter(mm, MM_ANONPAGES);
inc_mm_counter(mm, MM_SWAPENTS);
swp_pte = swp_entry_to_pte(entry);
if (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);
} 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));
}
discard:
if (unlikely(folio_test_hugetlb(folio)))
hugetlb_remove_rmap(folio);
else
folio_remove_rmap_pte(folio, subpage, vma);
if (vma->vm_flags & VM_LOCKED)
mlock_drain_local();
folio_put(folio);
}
mmu_notifier_invalidate_range_end(&range);
return ret;
}
static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
{
return vma_is_temporary_stack(vma);
}
static int folio_not_mapped(struct folio *folio)
{
return !folio_mapped(folio);
}
/**
* try_to_unmap - Try to remove all page table mappings to a folio.
* @folio: The folio to unmap.
* @flags: action and flags
*
* Tries to remove all the page table entries which are mapping this
* folio. It is the caller's responsibility to check if the folio is
* still mapped if needed (use TTU_SYNC to prevent accounting races).
*
* Context: Caller must hold the folio lock.
*/
void try_to_unmap(struct folio *folio, enum ttu_flags flags)
{
struct rmap_walk_control rwc = {
.rmap_one = try_to_unmap_one,
.arg = (void *)flags,
.done = folio_not_mapped,
.anon_lock = folio_lock_anon_vma_read,
};
if (flags & TTU_RMAP_LOCKED)
rmap_walk_locked(folio, &rwc);
else
rmap_walk(folio, &rwc);
}
/*
* @arg: enum ttu_flags will be passed to this argument.
*
* If TTU_SPLIT_HUGE_PMD is specified any PMD mappings will be split into PTEs
* containing migration entries.
*/
static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
unsigned long address, void *arg)
{
struct mm_struct *mm = vma->vm_mm;
DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
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;
unsigned long pfn;
unsigned long hsz = 0;
/*
* When racing against e.g. zap_pte_range() on another cpu,
* in between its ptep_get_and_clear_full() and folio_remove_rmap_*(),
* try_to_migrate() may return before 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->vm_mm,
address, range.end);
if (folio_test_hugetlb(folio)) {
/*
* If sharing is possible, start and end will be adjusted
* accordingly.
*/
adjust_range_if_pmd_sharing_possible(vma, &range.start,
&range.end);
/* We need the huge page size for set_huge_pte_at() */
hsz = huge_page_size(hstate_vma(vma));
}
mmu_notifier_invalidate_range_start(&range);
while (page_vma_mapped_walk(&pvmw)) {
#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);
pfn = pte_pfn(ptep_get(pvmw.pte));
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, pfn - 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);
/*
* 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, pfn);
/* Nuke the page table entry. */
if (should_defer_flush(mm, flags)) {
/*
* We clear the PTE but do not flush so potentially
* a remote CPU could still be writing to the folio.
* If the entry was previously clean then the
* architecture must guarantee that a clear->dirty
* transition on a cached TLB entry is written through
* and traps if the PTE is unmapped.
*/
pteval = ptep_get_and_clear(mm, address, pvmw.pte);
set_tlb_ubc_flush_pending(mm, pteval, address);
} else {
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)
WARN_ON_ONCE(folio_try_share_anon_rmap_pte(folio,
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),
folio_order(folio));
/*
* 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,
hsz);
} else {
dec_mm_counter(mm, mm_counter(folio));
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));
} 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, hsz);
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 folio_try_share_anon_rmap_pte(): clear PTE first. */
if (folio_test_hugetlb(folio)) {
if (anon_exclusive &&
hugetlb_try_share_anon_rmap(folio)) {
set_huge_pte_at(mm, address, pvmw.pte,
pteval, hsz);
ret = false;
page_vma_mapped_walk_done(&pvmw);
break;
}
} else if (anon_exclusive &&
folio_try_share_anon_rmap_pte(folio, subpage)) {
set_pte_at(mm, address, pvmw.pte, pteval);
ret = false;
page_vma_mapped_walk_done(&pvmw);
break;
}
/*
* Store the pfn of the page in a special migration
* pte. do_swap_page() will wait until the migration
* pte is removed and then restart fault handling.
*/
if (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,
hsz);
else
set_pte_at(mm, address, pvmw.pte, swp_pte);
trace_set_migration_pte(address, pte_val(swp_pte),
folio_order(folio));
/*
* No need to invalidate here it will synchronize on
* against the special swap migration pte.
*/
}
if (unlikely(folio_test_hugetlb(folio)))
hugetlb_remove_rmap(folio);
else
folio_remove_rmap_pte(folio, subpage, vma);
if (vma->vm_flags & VM_LOCKED)
mlock_drain_local();
folio_put(folio);
}
mmu_notifier_invalidate_range_end(&range);
return ret;
}
/**
* try_to_migrate - try to replace all page table mappings with swap entries
* @folio: the folio to replace page table entries for
* @flags: action and flags
*
* Tries to remove all the page table entries which are mapping this folio and
* replace them with special swap entries. Caller must hold the folio lock.
*/
void try_to_migrate(struct folio *folio, enum ttu_flags flags)
{
struct rmap_walk_control rwc = {
.rmap_one = try_to_migrate_one,
.arg = (void *)flags,
.done = folio_not_mapped,
.anon_lock = folio_lock_anon_vma_read,
};
/*
* Migration always ignores mlock and only supports TTU_RMAP_LOCKED and
* TTU_SPLIT_HUGE_PMD, TTU_SYNC, and TTU_BATCH_FLUSH flags.
*/
if (WARN_ON_ONCE(flags & ~(TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD |
TTU_SYNC | TTU_BATCH_FLUSH)))
return;
if (folio_is_zone_device(folio) &&
(!folio_is_device_private(folio) && !folio_is_device_coherent(folio)))
return;
/*
* During exec, a temporary VMA is setup and later moved.
* The VMA is moved under the anon_vma lock but not the
* page tables leading to a race where migration cannot
* find the migration ptes. Rather than increasing the
* locking requirements of exec(), migration skips
* temporary VMAs until after exec() completes.
*/
if (!folio_test_ksm(folio) && folio_test_anon(folio))
rwc.invalid_vma = invalid_migration_vma;
if (flags & TTU_RMAP_LOCKED)
rmap_walk_locked(folio, &rwc);
else
rmap_walk(folio, &rwc);
}
#ifdef CONFIG_DEVICE_PRIVATE
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;
pte_t ptent;
mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0,
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);
ptent = ptep_get(pvmw.pte);
if (!pte_present(ptent)) {
ret = false;
page_vma_mapped_walk_done(&pvmw);
break;
}
subpage = folio_page(folio,
pte_pfn(ptent) - folio_pfn(folio));
address = pvmw.address;
/* Nuke the page table entry. */
flush_cache_page(vma, address, pte_pfn(ptent));
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.
*/
folio_remove_rmap_pte(folio, subpage, vma);
}
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 = folio_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);
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
* @folio: the folio to be handled
* @rwc: control variable according to each walk type
* @locked: caller holds relevant rmap lock
*
* Find all the mappings of a folio using the mapping pointer and the vma
* chains contained in the anon_vma struct it points to.
*/
static void rmap_walk_anon(struct folio *folio,
struct rmap_walk_control *rwc, bool locked)
{
struct anon_vma *anon_vma;
pgoff_t pgoff_start, pgoff_end;
struct anon_vma_chain *avc;
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
* @folio: the folio to be handled
* @rwc: control variable according to each walk type
* @locked: caller holds relevant rmap lock
*
* Find all the mappings of a folio using the mapping pointer and the vma chains
* contained in the address_space struct it points to.
*/
static void rmap_walk_file(struct folio *folio,
struct rmap_walk_control *rwc, bool locked)
{
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.
*/
void hugetlb_add_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
unsigned long address, rmap_t flags)
{
VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
atomic_inc(&folio->_entire_mapcount);
if (flags & RMAP_EXCLUSIVE)
SetPageAnonExclusive(&folio->page);
VM_WARN_ON_FOLIO(folio_entire_mapcount(folio) > 1 &&
PageAnonExclusive(&folio->page), folio);
}
void hugetlb_add_new_anon_rmap(struct folio *folio,
struct vm_area_struct *vma, unsigned long address)
{
VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
BUG_ON(address < vma->vm_start || address >= vma->vm_end);
/* increment count (starts at -1) */
atomic_set(&folio->_entire_mapcount, 0);
folio_clear_hugetlb_restore_reserve(folio);
__folio_set_anon(folio, vma, address, true);
SetPageAnonExclusive(&folio->page);
}
#endif /* CONFIG_HUGETLB_PAGE */
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