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linux/mm/rmap.c
Zhiguo Jiang c495b97624 mm: shrink skip folio mapped by an exiting process 
The releasing process of the non-shared anonymous folio mapped solely by
an exiting process may go through two flows: 1) the anonymous folio is
firstly is swaped-out into swapspace and transformed into a swp_entry in
shrink_folio_list; 2) then the swp_entry is released in the process
exiting flow.  This will result in the high cpu load of releasing a
non-shared anonymous folio mapped solely by an exiting process.

When the low system memory and the exiting process exist at the same time,
it will be likely to happen, because the non-shared anonymous folio mapped
solely by an exiting process may be reclaimed by shrink_folio_list.

This patch is that shrink skips the non-shared anonymous folio solely
mapped by an exting process and this folio is only released directly in
the process exiting flow, which will save swap-out time and alleviate the
load of the process exiting.

Barry provided some effectiveness testing in [1].  "I observed that
this patch effectively skipped 6114 folios (either 4KB or 64KB mTHP),
potentially reducing the swap-out by up to 92MB (97,300,480 bytes)
during the process exit.  The working set size is 256MB."

Link: https://lkml.kernel.org/r/20240710083641.546-1-justinjiang@vivo.com
Link: https://lore.kernel.org/linux-mm/20240710033212.36497-1-21cnbao@gmail.com/ [1]
Signed-off-by: Zhiguo Jiang <justinjiang@vivo.com>
Acked-by: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-09-01 20:25:48 -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 <linux/oom.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.
*/
int __anon_vma_prepare(struct vm_area_struct *vma)
{
struct mm_struct *mm = vma->vm_mm;
struct anon_vma *anon_vma, *allocated;
struct anon_vma_chain *avc;
mmap_assert_locked(mm);
might_sleep();
avc = anon_vma_chain_alloc(GFP_KERNEL);
if (!avc)
goto out_enomem;
anon_vma = find_mergeable_anon_vma(vma);
allocated = NULL;
if (!anon_vma) {
anon_vma = anon_vma_alloc();
if (unlikely(!anon_vma))
goto out_enomem_free_avc;
anon_vma->num_children++; /* self-parent link for new root */
allocated = anon_vma;
}
anon_vma_lock_write(anon_vma);
/* page_table_lock to protect against threads */
spin_lock(&mm->page_table_lock);
if (likely(!vma->anon_vma)) {
vma->anon_vma = anon_vma;
anon_vma_chain_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);
pgoff_t pgoff;
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;
}
/* The !page__anon_vma above handles KSM folios */
pgoff = folio->index + folio_page_idx(folio, page);
return vma_address(vma, pgoff, 1);
}
/*
* Returns the actual pmd_t* where we expect 'address' to be mapped from, or
* NULL if it doesn't exist. No guarantees / checks on what the pmd_t*
* represents.
*/
pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
{
pgd_t *pgd;
p4d_t *p4d;
pud_t *pud;
pmd_t *pmd = NULL;
pgd = pgd_offset(mm, address);
if (!pgd_present(*pgd))
goto out;
p4d = p4d_offset(pgd, address);
if (!p4d_present(*p4d))
goto out;
pud = pud_offset(p4d, address);
if (!pud_present(*pud))
goto out;
pmd = pmd_offset(pud, address);
out:
return pmd;
}
struct folio_referenced_arg {
int mapcount;
int referenced;
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;
}
/*
* Skip the non-shared swapbacked folio mapped solely by
* the exiting or OOM-reaped process. This avoids redundant
* swap-out followed by an immediate unmap.
*/
if ((!atomic_read(&vma->vm_mm->mm_users) ||
check_stable_address_space(vma->vm_mm)) &&
folio_test_anon(folio) && folio_test_swapbacked(folio) &&
!folio_likely_mapped_shared(folio)) {
pra->referenced = -1;
page_vma_mapped_walk_done(&pvmw);
return false;
}
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)
{
bool we_locked = false;
struct folio_referenced_arg pra = {
.mapcount = folio_mapcount(folio),
.memcg = memcg,
};
struct rmap_walk_control rwc = {
.rmap_one = folio_referenced_one,
.arg = (void *)&pra,
.anon_lock = folio_lock_anon_vma_read,
.try_lock = true,
.invalid_vma = invalid_folio_referenced_vma,
};
*vm_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_address(vma, pgoff, nr_pages);
VM_BUG_ON_VMA(pvmw.address == -EFAULT, vma);
return page_vma_mkclean_one(&pvmw);
}
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;
const int orig_nr_pages = nr_pages;
int first, nr = 0;
__folio_rmap_sanity_checks(folio, page, nr_pages, level);
switch (level) {
case RMAP_LEVEL_PTE:
if (!folio_test_large(folio)) {
nr = atomic_inc_and_test(&page->_mapcount);
break;
}
do {
first = atomic_inc_and_test(&page->_mapcount);
if (first) {
first = atomic_inc_return_relaxed(mapped);
if (first < ENTIRELY_MAPPED)
nr++;
}
} while (page++, --nr_pages > 0);
atomic_add(orig_nr_pages, &folio->_large_mapcount);
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;
}
}
atomic_inc(&folio->_large_mapcount);
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 void __folio_mod_stat(struct folio *folio, int nr, int nr_pmdmapped)
{
int idx;
if (nr) {
idx = folio_test_anon(folio) ? NR_ANON_MAPPED : NR_FILE_MAPPED;
__lruvec_stat_mod_folio(folio, idx, nr);
}
if (nr_pmdmapped) {
if (folio_test_anon(folio)) {
idx = NR_ANON_THPS;
__lruvec_stat_mod_folio(folio, idx, nr_pmdmapped);
} else {
/* NR_*_PMDMAPPED are not maintained per-memcg */
idx = folio_test_swapbacked(folio) ?
NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED;
__mod_node_page_state(folio_pgdat(folio), idx,
nr_pmdmapped);
}
}
}
static __always_inline void __folio_add_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;
VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
nr = __folio_add_rmap(folio, page, nr_pages, level, &nr_pmdmapped);
if (likely(!folio_test_ksm(folio)))
__page_check_anon_rmap(folio, page, vma, address);
__folio_mod_stat(folio, nr, nr_pmdmapped);
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
* @flags: The rmap flags
*
* Like folio_add_anon_rmap_*() but must only be called on *new* folios.
* This means the inc-and-test can be bypassed.
* The folio doesn't necessarily need to be locked while it's exclusive
* unless two threads map it concurrently. However, the folio must be
* locked if it's shared.
*
* If the folio is pmd-mappable, it is accounted as a THP.
*/
void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
unsigned long address, rmap_t flags)
{
const int nr = folio_nr_pages(folio);
const bool exclusive = flags & RMAP_EXCLUSIVE;
int nr_pmdmapped = 0;
VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
VM_WARN_ON_FOLIO(!exclusive && !folio_test_locked(folio), folio);
VM_BUG_ON_VMA(address < vma->vm_start ||
address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
/*
* VM_DROPPABLE mappings don't swap; instead they're just dropped when
* under memory pressure.
*/
if (!folio_test_swapbacked(folio) && !(vma->vm_flags & VM_DROPPABLE))
__folio_set_swapbacked(folio);
__folio_set_anon(folio, vma, address, exclusive);
if (likely(!folio_test_large(folio))) {
/* increment count (starts at -1) */
atomic_set(&folio->_mapcount, 0);
if (exclusive)
SetPageAnonExclusive(&folio->page);
} else if (!folio_test_pmd_mappable(folio)) {
int i;
for (i = 0; i < nr; i++) {
struct page *page = folio_page(folio, i);
/* increment count (starts at -1) */
atomic_set(&page->_mapcount, 0);
if (exclusive)
SetPageAnonExclusive(page);
}
/* increment count (starts at -1) */
atomic_set(&folio->_large_mapcount, nr - 1);
atomic_set(&folio->_nr_pages_mapped, nr);
} else {
/* increment count (starts at -1) */
atomic_set(&folio->_entire_mapcount, 0);
/* increment count (starts at -1) */
atomic_set(&folio->_large_mapcount, 0);
atomic_set(&folio->_nr_pages_mapped, ENTIRELY_MAPPED);
if (exclusive)
SetPageAnonExclusive(&folio->page);
nr_pmdmapped = nr;
}
__folio_mod_stat(folio, nr, nr_pmdmapped);
}
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);
__folio_mod_stat(folio, nr, nr_pmdmapped);
/* 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;
bool partially_mapped = false;
__folio_rmap_sanity_checks(folio, page, nr_pages, level);
switch (level) {
case RMAP_LEVEL_PTE:
if (!folio_test_large(folio)) {
nr = atomic_add_negative(-1, &page->_mapcount);
break;
}
atomic_sub(nr_pages, &folio->_large_mapcount);
do {
last = atomic_add_negative(-1, &page->_mapcount);
if (last) {
last = atomic_dec_return_relaxed(mapped);
if (last < ENTIRELY_MAPPED)
nr++;
}
} while (page++, --nr_pages > 0);
partially_mapped = nr && atomic_read(mapped);
break;
case RMAP_LEVEL_PMD:
atomic_dec(&folio->_large_mapcount);
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;
}
}
partially_mapped = nr < nr_pmdmapped;
break;
}
if (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.
*
* Check partially_mapped first to ensure it is a large folio.
*/
if (folio_test_anon(folio) && partially_mapped &&
list_empty(&folio->_deferred_list))
deferred_split_folio(folio);
}
__folio_mod_stat(folio, -nr, -nr_pmdmapped);
/*
* It would be tidy to reset folio_test_anon mapping when fully
* unmapped, but that might overwrite a racing folio_add_anon_rmap_*()
* which increments mapcount after us but sets mapping before us:
* so leave the reset to free_pages_prepare, and remember that
* it's only reliable while mapped.
*/
munlock_vma_folio(folio, vma);
}
/**
* folio_remove_rmap_ptes - remove PTE mappings from a page range of a folio
* @folio: The folio to remove the mappings from
* @page: The first page to remove
* @nr_pages: The number of pages that will be removed from the mapping
* @vma: The vm area from which the mappings are removed
*
* The page range of the folio is defined by [page, page + nr_pages)
*
* The caller needs to hold the page table lock.
*/
void folio_remove_rmap_ptes(struct folio *folio, struct page *page,
int nr_pages, struct vm_area_struct *vma)
{
__folio_remove_rmap(folio, page, nr_pages, vma, 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;
/*
* 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)) {
/*
* 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);
goto walk_abort;
}
if (!pvmw.pte) {
if (unmap_huge_pmd_locked(vma, pvmw.address, pvmw.pmd,
folio))
goto walk_done;
if (flags & TTU_SPLIT_HUGE_PMD) {
/*
* We temporarily have to drop the PTL and
* restart so we can process the PTE-mapped THP.
*/
split_huge_pmd_locked(vma, pvmw.address,
pvmw.pmd, false, folio);
flags &= ~TTU_SPLIT_HUGE_PMD;
page_vma_mapped_walk_restart(&pvmw);
continue;
}
}
/* Unexpected PMD-mapped THP? */
VM_BUG_ON_FOLIO(!pvmw.pte, folio);
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))
goto walk_abort;
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.
*/
goto walk_done;
}
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);
goto walk_abort;
}
/* 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) ||
/*
* Unlike MADV_FREE mappings, VM_DROPPABLE
* ones can be dropped even if they've
* been dirtied.
*/
(vma->vm_flags & VM_DROPPABLE))) {
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);
/*
* Unlike MADV_FREE mappings, VM_DROPPABLE ones
* never get swap backed on failure to drop.
*/
if (!(vma->vm_flags & VM_DROPPABLE))
folio_set_swapbacked(folio);
goto walk_abort;
}
if (swap_duplicate(entry) < 0) {
set_pte_at(mm, address, pvmw.pte, pteval);
goto walk_abort;
}
if (arch_unmap_one(mm, vma, address, pteval) < 0) {
swap_free(entry);
set_pte_at(mm, address, pvmw.pte, pteval);
goto walk_abort;
}
/* 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);
goto walk_abort;
}
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);
continue;
walk_abort:
ret = false;
walk_done:
page_vma_mapped_walk_done(&pvmw);
break;
}
mmu_notifier_invalidate_range_end(&range);
return ret;
}
static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
{
return vma_is_temporary_stack(vma);
}
static int folio_not_mapped(struct folio *folio)
{
return !folio_mapped(folio);
}
/**
* try_to_unmap - Try to remove all page table mappings to a folio.
* @folio: The folio to unmap.
* @flags: action and flags
*
* Tries to remove all the page table entries which are mapping this
* folio. It is the caller's responsibility to check if the folio is
* still mapped if needed (use TTU_SYNC to prevent accounting races).
*
* Context: Caller must hold the folio lock.
*/
void try_to_unmap(struct folio *folio, enum ttu_flags flags)
{
struct rmap_walk_control rwc = {
.rmap_one = 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(vma, pgoff_start,
folio_nr_pages(folio));
VM_BUG_ON_VMA(address == -EFAULT, vma);
cond_resched();
if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
continue;
if (!rwc->rmap_one(folio, vma, address, rwc->arg))
break;
if (rwc->done && rwc->done(folio))
break;
}
if (!locked)
anon_vma_unlock_read(anon_vma);
}
/*
* rmap_walk_file - 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(vma, pgoff_start,
folio_nr_pages(folio));
VM_BUG_ON_VMA(address == -EFAULT, vma);
cond_resched();
if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
continue;
if (!rwc->rmap_one(folio, vma, address, rwc->arg))
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);
atomic_inc(&folio->_large_mapcount);
if (flags & RMAP_EXCLUSIVE)
SetPageAnonExclusive(&folio->page);
VM_WARN_ON_FOLIO(folio_entire_mapcount(folio) > 1 &&
PageAnonExclusive(&folio->page), folio);
}
void hugetlb_add_new_anon_rmap(struct folio *folio,
struct vm_area_struct *vma, unsigned long address)
{
VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
BUG_ON(address < vma->vm_start || address >= vma->vm_end);
/* increment count (starts at -1) */
atomic_set(&folio->_entire_mapcount, 0);
atomic_set(&folio->_large_mapcount, 0);
folio_clear_hugetlb_restore_reserve(folio);
__folio_set_anon(folio, vma, address, true);
SetPageAnonExclusive(&folio->page);
}
#endif /* CONFIG_HUGETLB_PAGE */
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