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v3.1
   1/*
   2 * mm/rmap.c - physical to virtual reverse mappings
   3 *
   4 * Copyright 2001, Rik van Riel <riel@conectiva.com.br>
   5 * Released under the General Public License (GPL).
   6 *
   7 * Simple, low overhead reverse mapping scheme.
   8 * Please try to keep this thing as modular as possible.
   9 *
  10 * Provides methods for unmapping each kind of mapped page:
  11 * the anon methods track anonymous pages, and
  12 * the file methods track pages belonging to an inode.
  13 *
  14 * Original design by Rik van Riel <riel@conectiva.com.br> 2001
  15 * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004
  16 * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004
  17 * Contributions by Hugh Dickins 2003, 2004
  18 */
  19
  20/*
  21 * Lock ordering in mm:
  22 *
  23 * inode->i_mutex	(while writing or truncating, not reading or faulting)
  24 *   mm->mmap_sem
  25 *     page->flags PG_locked (lock_page)
  26 *       mapping->i_mmap_mutex
  27 *         anon_vma->mutex
  28 *           mm->page_table_lock or pte_lock
  29 *             zone->lru_lock (in mark_page_accessed, isolate_lru_page)
  30 *             swap_lock (in swap_duplicate, swap_info_get)
  31 *               mmlist_lock (in mmput, drain_mmlist and others)
  32 *               mapping->private_lock (in __set_page_dirty_buffers)
  33 *               inode->i_lock (in set_page_dirty's __mark_inode_dirty)
  34 *               bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty)
  35 *                 sb_lock (within inode_lock in fs/fs-writeback.c)
  36 *                 mapping->tree_lock (widely used, in set_page_dirty,
  37 *                           in arch-dependent flush_dcache_mmap_lock,
  38 *                           within bdi.wb->list_lock in __sync_single_inode)
 
 
 
 
 
  39 *
  40 * anon_vma->mutex,mapping->i_mutex      (memory_failure, collect_procs_anon)
  41 *   ->tasklist_lock
  42 *     pte map lock
 
 
 
 
 
 
  43 */
  44
  45#include <linux/mm.h>
 
 
  46#include <linux/pagemap.h>
  47#include <linux/swap.h>
  48#include <linux/swapops.h>
  49#include <linux/slab.h>
  50#include <linux/init.h>
  51#include <linux/ksm.h>
  52#include <linux/rmap.h>
  53#include <linux/rcupdate.h>
  54#include <linux/module.h>
  55#include <linux/memcontrol.h>
  56#include <linux/mmu_notifier.h>
  57#include <linux/migrate.h>
  58#include <linux/hugetlb.h>
 
 
 
 
 
 
  59
  60#include <asm/tlbflush.h>
  61
 
 
 
 
  62#include "internal.h"
  63
  64static struct kmem_cache *anon_vma_cachep;
  65static struct kmem_cache *anon_vma_chain_cachep;
  66
  67static inline struct anon_vma *anon_vma_alloc(void)
  68{
  69	struct anon_vma *anon_vma;
  70
  71	anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
  72	if (anon_vma) {
  73		atomic_set(&anon_vma->refcount, 1);
 
 
 
  74		/*
  75		 * Initialise the anon_vma root to point to itself. If called
  76		 * from fork, the root will be reset to the parents anon_vma.
  77		 */
  78		anon_vma->root = anon_vma;
  79	}
  80
  81	return anon_vma;
  82}
  83
  84static inline void anon_vma_free(struct anon_vma *anon_vma)
  85{
  86	VM_BUG_ON(atomic_read(&anon_vma->refcount));
  87
  88	/*
  89	 * Synchronize against page_lock_anon_vma() such that
  90	 * we can safely hold the lock without the anon_vma getting
  91	 * freed.
  92	 *
  93	 * Relies on the full mb implied by the atomic_dec_and_test() from
  94	 * put_anon_vma() against the acquire barrier implied by
  95	 * mutex_trylock() from page_lock_anon_vma(). This orders:
  96	 *
  97	 * page_lock_anon_vma()		VS	put_anon_vma()
  98	 *   mutex_trylock()			  atomic_dec_and_test()
  99	 *   LOCK				  MB
 100	 *   atomic_read()			  mutex_is_locked()
 101	 *
 102	 * LOCK should suffice since the actual taking of the lock must
 103	 * happen _before_ what follows.
 104	 */
 105	if (mutex_is_locked(&anon_vma->root->mutex)) {
 106		anon_vma_lock(anon_vma);
 107		anon_vma_unlock(anon_vma);
 
 108	}
 109
 110	kmem_cache_free(anon_vma_cachep, anon_vma);
 111}
 112
 113static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
 114{
 115	return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
 116}
 117
 118static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
 119{
 120	kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
 121}
 122
 
 
 
 
 
 
 
 
 
 
 123/**
 124 * anon_vma_prepare - attach an anon_vma to a memory region
 125 * @vma: the memory region in question
 126 *
 127 * This makes sure the memory mapping described by 'vma' has
 128 * an 'anon_vma' attached to it, so that we can associate the
 129 * anonymous pages mapped into it with that anon_vma.
 130 *
 131 * The common case will be that we already have one, but if
 
 132 * not we either need to find an adjacent mapping that we
 133 * can re-use the anon_vma from (very common when the only
 134 * reason for splitting a vma has been mprotect()), or we
 135 * allocate a new one.
 136 *
 137 * Anon-vma allocations are very subtle, because we may have
 138 * optimistically looked up an anon_vma in page_lock_anon_vma()
 139 * and that may actually touch the spinlock even in the newly
 140 * allocated vma (it depends on RCU to make sure that the
 141 * anon_vma isn't actually destroyed).
 142 *
 143 * As a result, we need to do proper anon_vma locking even
 144 * for the new allocation. At the same time, we do not want
 145 * to do any locking for the common case of already having
 146 * an anon_vma.
 147 *
 148 * This must be called with the mmap_sem held for reading.
 149 */
 150int anon_vma_prepare(struct vm_area_struct *vma)
 151{
 152	struct anon_vma *anon_vma = vma->anon_vma;
 
 153	struct anon_vma_chain *avc;
 154
 155	might_sleep();
 156	if (unlikely(!anon_vma)) {
 157		struct mm_struct *mm = vma->vm_mm;
 158		struct anon_vma *allocated;
 159
 160		avc = anon_vma_chain_alloc(GFP_KERNEL);
 161		if (!avc)
 162			goto out_enomem;
 163
 164		anon_vma = find_mergeable_anon_vma(vma);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 165		allocated = NULL;
 166		if (!anon_vma) {
 167			anon_vma = anon_vma_alloc();
 168			if (unlikely(!anon_vma))
 169				goto out_enomem_free_avc;
 170			allocated = anon_vma;
 171		}
 172
 173		anon_vma_lock(anon_vma);
 174		/* page_table_lock to protect against threads */
 175		spin_lock(&mm->page_table_lock);
 176		if (likely(!vma->anon_vma)) {
 177			vma->anon_vma = anon_vma;
 178			avc->anon_vma = anon_vma;
 179			avc->vma = vma;
 180			list_add(&avc->same_vma, &vma->anon_vma_chain);
 181			list_add_tail(&avc->same_anon_vma, &anon_vma->head);
 182			allocated = NULL;
 183			avc = NULL;
 184		}
 185		spin_unlock(&mm->page_table_lock);
 186		anon_vma_unlock(anon_vma);
 187
 188		if (unlikely(allocated))
 189			put_anon_vma(allocated);
 190		if (unlikely(avc))
 191			anon_vma_chain_free(avc);
 192	}
 
 
 
 
 
 
 
 
 193	return 0;
 194
 195 out_enomem_free_avc:
 196	anon_vma_chain_free(avc);
 197 out_enomem:
 198	return -ENOMEM;
 199}
 200
 201/*
 202 * This is a useful helper function for locking the anon_vma root as
 203 * we traverse the vma->anon_vma_chain, looping over anon_vma's that
 204 * have the same vma.
 205 *
 206 * Such anon_vma's should have the same root, so you'd expect to see
 207 * just a single mutex_lock for the whole traversal.
 208 */
 209static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
 210{
 211	struct anon_vma *new_root = anon_vma->root;
 212	if (new_root != root) {
 213		if (WARN_ON_ONCE(root))
 214			mutex_unlock(&root->mutex);
 215		root = new_root;
 216		mutex_lock(&root->mutex);
 217	}
 218	return root;
 219}
 220
 221static inline void unlock_anon_vma_root(struct anon_vma *root)
 222{
 223	if (root)
 224		mutex_unlock(&root->mutex);
 225}
 226
 227static void anon_vma_chain_link(struct vm_area_struct *vma,
 228				struct anon_vma_chain *avc,
 229				struct anon_vma *anon_vma)
 230{
 231	avc->vma = vma;
 232	avc->anon_vma = anon_vma;
 233	list_add(&avc->same_vma, &vma->anon_vma_chain);
 234
 235	/*
 236	 * It's critical to add new vmas to the tail of the anon_vma,
 237	 * see comment in huge_memory.c:__split_huge_page().
 238	 */
 239	list_add_tail(&avc->same_anon_vma, &anon_vma->head);
 240}
 241
 242/*
 243 * Attach the anon_vmas from src to dst.
 244 * Returns 0 on success, -ENOMEM on failure.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 245 */
 246int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
 247{
 248	struct anon_vma_chain *avc, *pavc;
 249	struct anon_vma *root = NULL;
 250
 251	list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
 252		struct anon_vma *anon_vma;
 253
 254		avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
 255		if (unlikely(!avc)) {
 256			unlock_anon_vma_root(root);
 257			root = NULL;
 258			avc = anon_vma_chain_alloc(GFP_KERNEL);
 259			if (!avc)
 260				goto enomem_failure;
 261		}
 262		anon_vma = pavc->anon_vma;
 263		root = lock_anon_vma_root(root, anon_vma);
 264		anon_vma_chain_link(dst, avc, anon_vma);
 
 
 
 
 
 
 
 
 
 
 
 
 265	}
 
 
 266	unlock_anon_vma_root(root);
 267	return 0;
 268
 269 enomem_failure:
 
 
 
 
 
 
 
 270	unlink_anon_vmas(dst);
 271	return -ENOMEM;
 272}
 273
 274/*
 275 * Attach vma to its own anon_vma, as well as to the anon_vmas that
 276 * the corresponding VMA in the parent process is attached to.
 277 * Returns 0 on success, non-zero on failure.
 278 */
 279int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
 280{
 281	struct anon_vma_chain *avc;
 282	struct anon_vma *anon_vma;
 
 283
 284	/* Don't bother if the parent process has no anon_vma here. */
 285	if (!pvma->anon_vma)
 286		return 0;
 287
 
 
 
 288	/*
 289	 * First, attach the new VMA to the parent VMA's anon_vmas,
 290	 * so rmap can find non-COWed pages in child processes.
 291	 */
 292	if (anon_vma_clone(vma, pvma))
 293		return -ENOMEM;
 
 
 
 
 
 294
 295	/* Then add our own anon_vma. */
 296	anon_vma = anon_vma_alloc();
 297	if (!anon_vma)
 298		goto out_error;
 
 299	avc = anon_vma_chain_alloc(GFP_KERNEL);
 300	if (!avc)
 301		goto out_error_free_anon_vma;
 302
 303	/*
 304	 * The root anon_vma's spinlock is the lock actually used when we
 305	 * lock any of the anon_vmas in this anon_vma tree.
 306	 */
 307	anon_vma->root = pvma->anon_vma->root;
 
 308	/*
 309	 * With refcounts, an anon_vma can stay around longer than the
 310	 * process it belongs to. The root anon_vma needs to be pinned until
 311	 * this anon_vma is freed, because the lock lives in the root.
 312	 */
 313	get_anon_vma(anon_vma->root);
 314	/* Mark this anon_vma as the one where our new (COWed) pages go. */
 315	vma->anon_vma = anon_vma;
 316	anon_vma_lock(anon_vma);
 317	anon_vma_chain_link(vma, avc, anon_vma);
 318	anon_vma_unlock(anon_vma);
 
 319
 320	return 0;
 321
 322 out_error_free_anon_vma:
 323	put_anon_vma(anon_vma);
 324 out_error:
 325	unlink_anon_vmas(vma);
 326	return -ENOMEM;
 327}
 328
 329void unlink_anon_vmas(struct vm_area_struct *vma)
 330{
 331	struct anon_vma_chain *avc, *next;
 332	struct anon_vma *root = NULL;
 333
 334	/*
 335	 * Unlink each anon_vma chained to the VMA.  This list is ordered
 336	 * from newest to oldest, ensuring the root anon_vma gets freed last.
 337	 */
 338	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
 339		struct anon_vma *anon_vma = avc->anon_vma;
 340
 341		root = lock_anon_vma_root(root, anon_vma);
 342		list_del(&avc->same_anon_vma);
 343
 344		/*
 345		 * Leave empty anon_vmas on the list - we'll need
 346		 * to free them outside the lock.
 347		 */
 348		if (list_empty(&anon_vma->head))
 
 349			continue;
 
 350
 351		list_del(&avc->same_vma);
 352		anon_vma_chain_free(avc);
 353	}
 
 
 
 
 
 
 
 
 
 354	unlock_anon_vma_root(root);
 355
 356	/*
 357	 * Iterate the list once more, it now only contains empty and unlinked
 358	 * anon_vmas, destroy them. Could not do before due to __put_anon_vma()
 359	 * needing to acquire the anon_vma->root->mutex.
 360	 */
 361	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
 362		struct anon_vma *anon_vma = avc->anon_vma;
 363
 
 
 364		put_anon_vma(anon_vma);
 365
 366		list_del(&avc->same_vma);
 367		anon_vma_chain_free(avc);
 368	}
 369}
 370
 371static void anon_vma_ctor(void *data)
 372{
 373	struct anon_vma *anon_vma = data;
 374
 375	mutex_init(&anon_vma->mutex);
 376	atomic_set(&anon_vma->refcount, 0);
 377	INIT_LIST_HEAD(&anon_vma->head);
 378}
 379
 380void __init anon_vma_init(void)
 381{
 382	anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
 383			0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor);
 384	anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC);
 
 
 385}
 386
 387/*
 388 * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
 389 *
 390 * Since there is no serialization what so ever against page_remove_rmap()
 391 * the best this function can do is return a locked anon_vma that might
 392 * have been relevant to this page.
 393 *
 394 * The page might have been remapped to a different anon_vma or the anon_vma
 395 * returned may already be freed (and even reused).
 396 *
 397 * In case it was remapped to a different anon_vma, the new anon_vma will be a
 398 * child of the old anon_vma, and the anon_vma lifetime rules will therefore
 399 * ensure that any anon_vma obtained from the page will still be valid for as
 400 * long as we observe page_mapped() [ hence all those page_mapped() tests ].
 401 *
 402 * All users of this function must be very careful when walking the anon_vma
 403 * chain and verify that the page in question is indeed mapped in it
 404 * [ something equivalent to page_mapped_in_vma() ].
 405 *
 406 * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap()
 407 * that the anon_vma pointer from page->mapping is valid if there is a
 408 * mapcount, we can dereference the anon_vma after observing those.
 
 
 
 
 
 
 
 409 */
 410struct anon_vma *page_get_anon_vma(struct page *page)
 411{
 412	struct anon_vma *anon_vma = NULL;
 413	unsigned long anon_mapping;
 414
 415	rcu_read_lock();
 416	anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
 417	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
 418		goto out;
 419	if (!page_mapped(page))
 420		goto out;
 421
 422	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
 423	if (!atomic_inc_not_zero(&anon_vma->refcount)) {
 424		anon_vma = NULL;
 425		goto out;
 426	}
 427
 428	/*
 429	 * If this page is still mapped, then its anon_vma cannot have been
 430	 * freed.  But if it has been unmapped, we have no security against the
 431	 * anon_vma structure being freed and reused (for another anon_vma:
 432	 * SLAB_DESTROY_BY_RCU guarantees that - so the atomic_inc_not_zero()
 433	 * above cannot corrupt).
 434	 */
 435	if (!page_mapped(page)) {
 
 436		put_anon_vma(anon_vma);
 437		anon_vma = NULL;
 438	}
 439out:
 440	rcu_read_unlock();
 441
 442	return anon_vma;
 443}
 444
 445/*
 446 * Similar to page_get_anon_vma() except it locks the anon_vma.
 447 *
 448 * Its a little more complex as it tries to keep the fast path to a single
 449 * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
 450 * reference like with page_get_anon_vma() and then block on the mutex.
 
 451 */
 452struct anon_vma *page_lock_anon_vma(struct page *page)
 
 453{
 454	struct anon_vma *anon_vma = NULL;
 455	struct anon_vma *root_anon_vma;
 456	unsigned long anon_mapping;
 457
 
 458	rcu_read_lock();
 459	anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
 460	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
 461		goto out;
 462	if (!page_mapped(page))
 463		goto out;
 464
 465	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
 466	root_anon_vma = ACCESS_ONCE(anon_vma->root);
 467	if (mutex_trylock(&root_anon_vma->mutex)) {
 
 
 
 
 
 
 
 
 
 
 
 468		/*
 469		 * If the page is still mapped, then this anon_vma is still
 470		 * its anon_vma, and holding the mutex ensures that it will
 471		 * not go away, see anon_vma_free().
 472		 */
 473		if (!page_mapped(page)) {
 474			mutex_unlock(&root_anon_vma->mutex);
 475			anon_vma = NULL;
 476		}
 477		goto out;
 478	}
 479
 
 
 
 
 
 
 480	/* trylock failed, we got to sleep */
 481	if (!atomic_inc_not_zero(&anon_vma->refcount)) {
 482		anon_vma = NULL;
 483		goto out;
 484	}
 485
 486	if (!page_mapped(page)) {
 
 487		put_anon_vma(anon_vma);
 488		anon_vma = NULL;
 489		goto out;
 490	}
 491
 492	/* we pinned the anon_vma, its safe to sleep */
 493	rcu_read_unlock();
 494	anon_vma_lock(anon_vma);
 
 
 
 
 
 
 
 
 
 
 
 
 495
 496	if (atomic_dec_and_test(&anon_vma->refcount)) {
 497		/*
 498		 * Oops, we held the last refcount, release the lock
 499		 * and bail -- can't simply use put_anon_vma() because
 500		 * we'll deadlock on the anon_vma_lock() recursion.
 501		 */
 502		anon_vma_unlock(anon_vma);
 503		__put_anon_vma(anon_vma);
 504		anon_vma = NULL;
 505	}
 506
 507	return anon_vma;
 508
 509out:
 510	rcu_read_unlock();
 511	return anon_vma;
 512}
 513
 514void page_unlock_anon_vma(struct anon_vma *anon_vma)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 515{
 516	anon_vma_unlock(anon_vma);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 517}
 518
 519/*
 520 * At what user virtual address is page expected in @vma?
 521 * Returns virtual address or -EFAULT if page's index/offset is not
 522 * within the range mapped the @vma.
 523 */
 524inline unsigned long
 525vma_address(struct page *page, struct vm_area_struct *vma)
 526{
 527	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
 528	unsigned long address;
 529
 530	if (unlikely(is_vm_hugetlb_page(vma)))
 531		pgoff = page->index << huge_page_order(page_hstate(page));
 532	address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
 533	if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
 534		/* page should be within @vma mapping range */
 535		return -EFAULT;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 536	}
 537	return address;
 
 
 
 
 538}
 539
 
 
 
 
 
 
 540/*
 541 * At what user virtual address is page expected in vma?
 542 * Caller should check the page is actually part of the vma.
 543 */
 544unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
 545{
 546	if (PageAnon(page)) {
 547		struct anon_vma *page__anon_vma = page_anon_vma(page);
 
 548		/*
 549		 * Note: swapoff's unuse_vma() is more efficient with this
 550		 * check, and needs it to match anon_vma when KSM is active.
 551		 */
 552		if (!vma->anon_vma || !page__anon_vma ||
 553		    vma->anon_vma->root != page__anon_vma->root)
 554			return -EFAULT;
 555	} else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
 556		if (!vma->vm_file ||
 557		    vma->vm_file->f_mapping != page->mapping)
 558			return -EFAULT;
 559	} else
 560		return -EFAULT;
 
 
 561	return vma_address(page, vma);
 562}
 563
 564/*
 565 * Check that @page is mapped at @address into @mm.
 566 *
 567 * If @sync is false, page_check_address may perform a racy check to avoid
 568 * the page table lock when the pte is not present (helpful when reclaiming
 569 * highly shared pages).
 570 *
 571 * On success returns with pte mapped and locked.
 572 */
 573pte_t *__page_check_address(struct page *page, struct mm_struct *mm,
 574			  unsigned long address, spinlock_t **ptlp, int sync)
 575{
 576	pgd_t *pgd;
 
 577	pud_t *pud;
 578	pmd_t *pmd;
 579	pte_t *pte;
 580	spinlock_t *ptl;
 581
 582	if (unlikely(PageHuge(page))) {
 583		pte = huge_pte_offset(mm, address);
 584		ptl = &mm->page_table_lock;
 585		goto check;
 586	}
 587
 588	pgd = pgd_offset(mm, address);
 589	if (!pgd_present(*pgd))
 590		return NULL;
 591
 592	pud = pud_offset(pgd, address);
 
 
 
 
 593	if (!pud_present(*pud))
 594		return NULL;
 595
 596	pmd = pmd_offset(pud, address);
 597	if (!pmd_present(*pmd))
 598		return NULL;
 599	if (pmd_trans_huge(*pmd))
 600		return NULL;
 601
 602	pte = pte_offset_map(pmd, address);
 603	/* Make a quick check before getting the lock */
 604	if (!sync && !pte_present(*pte)) {
 605		pte_unmap(pte);
 606		return NULL;
 607	}
 608
 609	ptl = pte_lockptr(mm, pmd);
 610check:
 611	spin_lock(ptl);
 612	if (pte_present(*pte) && page_to_pfn(page) == pte_pfn(*pte)) {
 613		*ptlp = ptl;
 614		return pte;
 615	}
 616	pte_unmap_unlock(pte, ptl);
 617	return NULL;
 618}
 619
 620/**
 621 * page_mapped_in_vma - check whether a page is really mapped in a VMA
 622 * @page: the page to test
 623 * @vma: the VMA to test
 624 *
 625 * Returns 1 if the page is mapped into the page tables of the VMA, 0
 626 * if the page is not mapped into the page tables of this VMA.  Only
 627 * valid for normal file or anonymous VMAs.
 628 */
 629int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
 630{
 631	unsigned long address;
 632	pte_t *pte;
 633	spinlock_t *ptl;
 634
 635	address = vma_address(page, vma);
 636	if (address == -EFAULT)		/* out of vma range */
 637		return 0;
 638	pte = page_check_address(page, vma->vm_mm, address, &ptl, 1);
 639	if (!pte)			/* the page is not in this mm */
 640		return 0;
 641	pte_unmap_unlock(pte, ptl);
 642
 643	return 1;
 644}
 645
 646/*
 647 * Subfunctions of page_referenced: page_referenced_one called
 648 * repeatedly from either page_referenced_anon or page_referenced_file.
 649 */
 650int page_referenced_one(struct page *page, struct vm_area_struct *vma,
 651			unsigned long address, unsigned int *mapcount,
 652			unsigned long *vm_flags)
 653{
 654	struct mm_struct *mm = vma->vm_mm;
 
 655	int referenced = 0;
 
 656
 657	if (unlikely(PageTransHuge(page))) {
 658		pmd_t *pmd;
 659
 660		spin_lock(&mm->page_table_lock);
 661		/*
 662		 * rmap might return false positives; we must filter
 663		 * these out using page_check_address_pmd().
 664		 */
 665		pmd = page_check_address_pmd(page, mm, address,
 666					     PAGE_CHECK_ADDRESS_PMD_FLAG);
 667		if (!pmd) {
 668			spin_unlock(&mm->page_table_lock);
 669			goto out;
 670		}
 671
 672		if (vma->vm_flags & VM_LOCKED) {
 673			spin_unlock(&mm->page_table_lock);
 674			*mapcount = 0;	/* break early from loop */
 675			*vm_flags |= VM_LOCKED;
 676			goto out;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 677		}
 678
 679		/* go ahead even if the pmd is pmd_trans_splitting() */
 680		if (pmdp_clear_flush_young_notify(vma, address, pmd))
 681			referenced++;
 682		spin_unlock(&mm->page_table_lock);
 683	} else {
 684		pte_t *pte;
 685		spinlock_t *ptl;
 686
 687		/*
 688		 * rmap might return false positives; we must filter
 689		 * these out using page_check_address().
 690		 */
 691		pte = page_check_address(page, mm, address, &ptl, 0);
 692		if (!pte)
 693			goto out;
 694
 695		if (vma->vm_flags & VM_LOCKED) {
 696			pte_unmap_unlock(pte, ptl);
 697			*mapcount = 0;	/* break early from loop */
 698			*vm_flags |= VM_LOCKED;
 699			goto out;
 
 
 
 
 
 700		}
 701
 702		if (ptep_clear_flush_young_notify(vma, address, pte)) {
 703			/*
 704			 * Don't treat a reference through a sequentially read
 705			 * mapping as such.  If the page has been used in
 706			 * another mapping, we will catch it; if this other
 707			 * mapping is already gone, the unmap path will have
 708			 * set PG_referenced or activated the page.
 709			 */
 710			if (likely(!VM_SequentialReadHint(vma)))
 711				referenced++;
 
 
 
 
 
 
 
 712		}
 713		pte_unmap_unlock(pte, ptl);
 714	}
 715
 716	/* Pretend the page is referenced if the task has the
 717	   swap token and is in the middle of a page fault. */
 718	if (mm != current->mm && has_swap_token(mm) &&
 719			rwsem_is_locked(&mm->mmap_sem))
 720		referenced++;
 721
 722	(*mapcount)--;
 
 
 
 723
 724	if (referenced)
 725		*vm_flags |= vma->vm_flags;
 726out:
 727	return referenced;
 728}
 729
 730static int page_referenced_anon(struct page *page,
 731				struct mem_cgroup *mem_cont,
 732				unsigned long *vm_flags)
 733{
 734	unsigned int mapcount;
 735	struct anon_vma *anon_vma;
 736	struct anon_vma_chain *avc;
 737	int referenced = 0;
 738
 739	anon_vma = page_lock_anon_vma(page);
 740	if (!anon_vma)
 741		return referenced;
 
 
 
 
 
 742
 743	mapcount = page_mapcount(page);
 744	list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
 745		struct vm_area_struct *vma = avc->vma;
 746		unsigned long address = vma_address(page, vma);
 747		if (address == -EFAULT)
 748			continue;
 749		/*
 750		 * If we are reclaiming on behalf of a cgroup, skip
 751		 * counting on behalf of references from different
 752		 * cgroups
 753		 */
 754		if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont))
 755			continue;
 756		referenced += page_referenced_one(page, vma, address,
 757						  &mapcount, vm_flags);
 758		if (!mapcount)
 759			break;
 760	}
 761
 762	page_unlock_anon_vma(anon_vma);
 763	return referenced;
 764}
 765
 766/**
 767 * page_referenced_file - referenced check for object-based rmap
 768 * @page: the page we're checking references on.
 769 * @mem_cont: target memory controller
 770 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
 771 *
 772 * For an object-based mapped page, find all the places it is mapped and
 773 * check/clear the referenced flag.  This is done by following the page->mapping
 774 * pointer, then walking the chain of vmas it holds.  It returns the number
 775 * of references it found.
 776 *
 777 * This function is only called from page_referenced for object-based pages.
 778 */
 779static int page_referenced_file(struct page *page,
 780				struct mem_cgroup *mem_cont,
 781				unsigned long *vm_flags)
 782{
 783	unsigned int mapcount;
 784	struct address_space *mapping = page->mapping;
 785	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
 786	struct vm_area_struct *vma;
 787	struct prio_tree_iter iter;
 788	int referenced = 0;
 
 
 
 
 789
 790	/*
 791	 * The caller's checks on page->mapping and !PageAnon have made
 792	 * sure that this is a file page: the check for page->mapping
 793	 * excludes the case just before it gets set on an anon page.
 794	 */
 795	BUG_ON(PageAnon(page));
 796
 797	/*
 798	 * The page lock not only makes sure that page->mapping cannot
 799	 * suddenly be NULLified by truncation, it makes sure that the
 800	 * structure at mapping cannot be freed and reused yet,
 801	 * so we can safely take mapping->i_mmap_mutex.
 802	 */
 803	BUG_ON(!PageLocked(page));
 
 
 
 
 
 
 
 
 
 
 804
 805	mutex_lock(&mapping->i_mmap_mutex);
 
 
 
 
 
 806
 807	/*
 808	 * i_mmap_mutex does not stabilize mapcount at all, but mapcount
 809	 * is more likely to be accurate if we note it after spinning.
 810	 */
 811	mapcount = page_mapcount(page);
 
 
 812
 813	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
 814		unsigned long address = vma_address(page, vma);
 815		if (address == -EFAULT)
 816			continue;
 817		/*
 818		 * If we are reclaiming on behalf of a cgroup, skip
 819		 * counting on behalf of references from different
 820		 * cgroups
 821		 */
 822		if (mem_cont && !mm_match_cgroup(vma->vm_mm, mem_cont))
 823			continue;
 824		referenced += page_referenced_one(page, vma, address,
 825						  &mapcount, vm_flags);
 826		if (!mapcount)
 827			break;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 828	}
 829
 830	mutex_unlock(&mapping->i_mmap_mutex);
 831	return referenced;
 
 832}
 833
 834/**
 835 * page_referenced - test if the page was referenced
 836 * @page: the page to test
 837 * @is_locked: caller holds lock on the page
 838 * @mem_cont: target memory controller
 839 * @vm_flags: collect encountered vma->vm_flags who actually referenced the page
 840 *
 841 * Quick test_and_clear_referenced for all mappings to a page,
 842 * returns the number of ptes which referenced the page.
 843 */
 844int page_referenced(struct page *page,
 845		    int is_locked,
 846		    struct mem_cgroup *mem_cont,
 847		    unsigned long *vm_flags)
 848{
 849	int referenced = 0;
 850	int we_locked = 0;
 851
 852	*vm_flags = 0;
 853	if (page_mapped(page) && page_rmapping(page)) {
 854		if (!is_locked && (!PageAnon(page) || PageKsm(page))) {
 855			we_locked = trylock_page(page);
 856			if (!we_locked) {
 857				referenced++;
 858				goto out;
 859			}
 860		}
 861		if (unlikely(PageKsm(page)))
 862			referenced += page_referenced_ksm(page, mem_cont,
 863								vm_flags);
 864		else if (PageAnon(page))
 865			referenced += page_referenced_anon(page, mem_cont,
 866								vm_flags);
 867		else if (page->mapping)
 868			referenced += page_referenced_file(page, mem_cont,
 869								vm_flags);
 870		if (we_locked)
 871			unlock_page(page);
 872
 873		if (page_test_and_clear_young(page_to_pfn(page)))
 874			referenced++;
 875	}
 876out:
 877	return referenced;
 878}
 879
 880static int page_mkclean_one(struct page *page, struct vm_area_struct *vma,
 881			    unsigned long address)
 882{
 883	struct mm_struct *mm = vma->vm_mm;
 884	pte_t *pte;
 885	spinlock_t *ptl;
 886	int ret = 0;
 887
 888	pte = page_check_address(page, mm, address, &ptl, 1);
 889	if (!pte)
 890		goto out;
 
 
 
 
 
 
 
 
 
 891
 892	if (pte_dirty(*pte) || pte_write(*pte)) {
 893		pte_t entry;
 894
 895		flush_cache_page(vma, address, pte_pfn(*pte));
 896		entry = ptep_clear_flush_notify(vma, address, pte);
 897		entry = pte_wrprotect(entry);
 898		entry = pte_mkclean(entry);
 899		set_pte_at(mm, address, pte, entry);
 900		ret = 1;
 901	}
 902
 903	pte_unmap_unlock(pte, ptl);
 904out:
 905	return ret;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 906}
 907
 908static int page_mkclean_file(struct address_space *mapping, struct page *page)
 909{
 910	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
 911	struct vm_area_struct *vma;
 912	struct prio_tree_iter iter;
 913	int ret = 0;
 914
 915	BUG_ON(PageAnon(page));
 
 
 
 
 
 
 
 
 
 
 916
 917	mutex_lock(&mapping->i_mmap_mutex);
 918	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
 919		if (vma->vm_flags & VM_SHARED) {
 920			unsigned long address = vma_address(page, vma);
 921			if (address == -EFAULT)
 922				continue;
 923			ret += page_mkclean_one(page, vma, address);
 924		}
 925	}
 926	mutex_unlock(&mapping->i_mmap_mutex);
 927	return ret;
 928}
 929
 930int page_mkclean(struct page *page)
 
 
 931{
 932	int ret = 0;
 
 933
 934	BUG_ON(!PageLocked(page));
 935
 936	if (page_mapped(page)) {
 937		struct address_space *mapping = page_mapping(page);
 938		if (mapping) {
 939			ret = page_mkclean_file(mapping, page);
 940			if (page_test_and_clear_dirty(page_to_pfn(page), 1))
 941				ret = 1;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 942		}
 
 943	}
 944
 945	return ret;
 946}
 947EXPORT_SYMBOL_GPL(page_mkclean);
 948
 949/**
 950 * page_move_anon_rmap - move a page to our anon_vma
 951 * @page:	the page to move to our anon_vma
 952 * @vma:	the vma the page belongs to
 953 * @address:	the user virtual address mapped
 954 *
 955 * When a page belongs exclusively to one process after a COW event,
 956 * that page can be moved into the anon_vma that belongs to just that
 957 * process, so the rmap code will not search the parent or sibling
 958 * processes.
 959 */
 960void page_move_anon_rmap(struct page *page,
 961	struct vm_area_struct *vma, unsigned long address)
 962{
 963	struct anon_vma *anon_vma = vma->anon_vma;
 964
 965	VM_BUG_ON(!PageLocked(page));
 966	VM_BUG_ON(!anon_vma);
 967	VM_BUG_ON(page->index != linear_page_index(vma, address));
 968
 969	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
 970	page->mapping = (struct address_space *) anon_vma;
 
 
 
 
 
 971}
 972
 973/**
 974 * __page_set_anon_rmap - set up new anonymous rmap
 975 * @page:	Page to add to rmap	
 976 * @vma:	VM area to add page to.
 977 * @address:	User virtual address of the mapping	
 978 * @exclusive:	the page is exclusively owned by the current process
 979 */
 980static void __page_set_anon_rmap(struct page *page,
 981	struct vm_area_struct *vma, unsigned long address, int exclusive)
 982{
 983	struct anon_vma *anon_vma = vma->anon_vma;
 984
 985	BUG_ON(!anon_vma);
 986
 987	if (PageAnon(page))
 988		return;
 989
 990	/*
 991	 * If the page isn't exclusively mapped into this vma,
 992	 * we must use the _oldest_ possible anon_vma for the
 993	 * page mapping!
 994	 */
 995	if (!exclusive)
 996		anon_vma = anon_vma->root;
 997
 
 
 
 
 
 
 998	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
 999	page->mapping = (struct address_space *) anon_vma;
1000	page->index = linear_page_index(vma, address);
1001}
1002
1003/**
1004 * __page_check_anon_rmap - sanity check anonymous rmap addition
1005 * @page:	the page to add the mapping to
 
1006 * @vma:	the vm area in which the mapping is added
1007 * @address:	the user virtual address mapped
1008 */
1009static void __page_check_anon_rmap(struct page *page,
1010	struct vm_area_struct *vma, unsigned long address)
1011{
1012#ifdef CONFIG_DEBUG_VM
1013	/*
1014	 * The page's anon-rmap details (mapping and index) are guaranteed to
1015	 * be set up correctly at this point.
1016	 *
1017	 * We have exclusion against page_add_anon_rmap because the caller
1018	 * always holds the page locked, except if called from page_dup_rmap,
1019	 * in which case the page is already known to be setup.
1020	 *
1021	 * We have exclusion against page_add_new_anon_rmap because those pages
1022	 * are initially only visible via the pagetables, and the pte is locked
1023	 * over the call to page_add_new_anon_rmap.
1024	 */
1025	BUG_ON(page_anon_vma(page)->root != vma->anon_vma->root);
1026	BUG_ON(page->index != linear_page_index(vma, address));
1027#endif
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1028}
1029
1030/**
1031 * page_add_anon_rmap - add pte mapping to an anonymous page
1032 * @page:	the page to add the mapping to
1033 * @vma:	the vm area in which the mapping is added
1034 * @address:	the user virtual address mapped
 
 
 
 
 
1035 *
1036 * The caller needs to hold the pte lock, and the page must be locked in
1037 * the anon_vma case: to serialize mapping,index checking after setting,
1038 * and to ensure that PageAnon is not being upgraded racily to PageKsm
1039 * (but PageKsm is never downgraded to PageAnon).
1040 */
1041void page_add_anon_rmap(struct page *page,
1042	struct vm_area_struct *vma, unsigned long address)
 
1043{
1044	do_page_add_anon_rmap(page, vma, address, 0);
 
1045}
1046
1047/*
1048 * Special version of the above for do_swap_page, which often runs
1049 * into pages that are exclusively owned by the current process.
1050 * Everybody else should continue to use page_add_anon_rmap above.
1051 */
1052void do_page_add_anon_rmap(struct page *page,
1053	struct vm_area_struct *vma, unsigned long address, int exclusive)
1054{
1055	int first = atomic_inc_and_test(&page->_mapcount);
1056	if (first) {
1057		if (!PageTransHuge(page))
1058			__inc_zone_page_state(page, NR_ANON_PAGES);
1059		else
1060			__inc_zone_page_state(page,
1061					      NR_ANON_TRANSPARENT_HUGEPAGES);
1062	}
1063	if (unlikely(PageKsm(page)))
1064		return;
1065
1066	VM_BUG_ON(!PageLocked(page));
1067	/* address might be in next vma when migration races vma_adjust */
1068	if (first)
1069		__page_set_anon_rmap(page, vma, address, exclusive);
1070	else
1071		__page_check_anon_rmap(page, vma, address);
1072}
1073
1074/**
1075 * page_add_new_anon_rmap - add pte mapping to a new anonymous page
1076 * @page:	the page to add the mapping to
1077 * @vma:	the vm area in which the mapping is added
1078 * @address:	the user virtual address mapped
1079 *
1080 * Same as page_add_anon_rmap but must only be called on *new* pages.
1081 * This means the inc-and-test can be bypassed.
1082 * Page does not have to be locked.
 
 
 
1083 */
1084void page_add_new_anon_rmap(struct page *page,
1085	struct vm_area_struct *vma, unsigned long address)
1086{
1087	VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1088	SetPageSwapBacked(page);
1089	atomic_set(&page->_mapcount, 0); /* increment count (starts at -1) */
1090	if (!PageTransHuge(page))
1091		__inc_zone_page_state(page, NR_ANON_PAGES);
1092	else
1093		__inc_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
1094	__page_set_anon_rmap(page, vma, address, 1);
1095	if (page_evictable(page, vma))
1096		lru_cache_add_lru(page, LRU_ACTIVE_ANON);
1097	else
1098		add_page_to_unevictable_list(page);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1099}
1100
1101/**
1102 * page_add_file_rmap - add pte mapping to a file page
1103 * @page: the page to add the mapping to
1104 *
1105 * The caller needs to hold the pte lock.
1106 */
1107void page_add_file_rmap(struct page *page)
1108{
1109	if (atomic_inc_and_test(&page->_mapcount)) {
1110		__inc_zone_page_state(page, NR_FILE_MAPPED);
1111		mem_cgroup_inc_page_stat(page, MEMCG_NR_FILE_MAPPED);
1112	}
 
 
 
 
 
 
 
 
 
 
1113}
1114
1115/**
1116 * page_remove_rmap - take down pte mapping from a page
1117 * @page: page to remove mapping from
 
 
 
1118 *
1119 * The caller needs to hold the pte lock.
 
 
1120 */
1121void page_remove_rmap(struct page *page)
 
1122{
1123	/* page still mapped by someone else? */
1124	if (!atomic_add_negative(-1, &page->_mapcount))
1125		return;
1126
1127	/*
1128	 * Now that the last pte has gone, s390 must transfer dirty
1129	 * flag from storage key to struct page.  We can usually skip
1130	 * this if the page is anon, so about to be freed; but perhaps
1131	 * not if it's in swapcache - there might be another pte slot
1132	 * containing the swap entry, but page not yet written to swap.
1133	 */
1134	if ((!PageAnon(page) || PageSwapCache(page)) &&
1135	    page_test_and_clear_dirty(page_to_pfn(page), 1))
1136		set_page_dirty(page);
1137	/*
1138	 * Hugepages are not counted in NR_ANON_PAGES nor NR_FILE_MAPPED
1139	 * and not charged by memcg for now.
1140	 */
1141	if (unlikely(PageHuge(page)))
1142		return;
1143	if (PageAnon(page)) {
1144		mem_cgroup_uncharge_page(page);
1145		if (!PageTransHuge(page))
1146			__dec_zone_page_state(page, NR_ANON_PAGES);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1147		else
1148			__dec_zone_page_state(page,
1149					      NR_ANON_TRANSPARENT_HUGEPAGES);
1150	} else {
1151		__dec_zone_page_state(page, NR_FILE_MAPPED);
1152		mem_cgroup_dec_page_stat(page, MEMCG_NR_FILE_MAPPED);
1153	}
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1154	/*
1155	 * It would be tidy to reset the PageAnon mapping here,
1156	 * but that might overwrite a racing page_add_anon_rmap
1157	 * which increments mapcount after us but sets mapping
1158	 * before us: so leave the reset to free_hot_cold_page,
1159	 * and remember that it's only reliable while mapped.
1160	 * Leaving it set also helps swapoff to reinstate ptes
1161	 * faster for those pages still in swapcache.
1162	 */
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1163}
1164
1165/*
1166 * Subfunctions of try_to_unmap: try_to_unmap_one called
1167 * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
1168 */
1169int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
1170		     unsigned long address, enum ttu_flags flags)
1171{
1172	struct mm_struct *mm = vma->vm_mm;
1173	pte_t *pte;
1174	pte_t pteval;
1175	spinlock_t *ptl;
1176	int ret = SWAP_AGAIN;
 
 
 
 
1177
1178	pte = page_check_address(page, mm, address, &ptl, 0);
1179	if (!pte)
1180		goto out;
 
 
 
 
 
 
 
 
1181
1182	/*
1183	 * If the page is mlock()d, we cannot swap it out.
1184	 * If it's recently referenced (perhaps page_referenced
1185	 * skipped over this mm) then we should reactivate it.
 
 
 
1186	 */
1187	if (!(flags & TTU_IGNORE_MLOCK)) {
1188		if (vma->vm_flags & VM_LOCKED)
1189			goto out_mlock;
 
 
 
 
 
 
 
1190
1191		if (TTU_ACTION(flags) == TTU_MUNLOCK)
1192			goto out_unmap;
1193	}
1194	if (!(flags & TTU_IGNORE_ACCESS)) {
1195		if (ptep_clear_flush_young_notify(vma, address, pte)) {
1196			ret = SWAP_FAIL;
1197			goto out_unmap;
 
 
 
 
 
 
 
 
 
 
 
 
 
1198		}
1199  	}
1200
1201	/* Nuke the page table entry. */
1202	flush_cache_page(vma, address, page_to_pfn(page));
1203	pteval = ptep_clear_flush_notify(vma, address, pte);
 
 
1204
1205	/* Move the dirty bit to the physical page now the pte is gone. */
1206	if (pte_dirty(pteval))
1207		set_page_dirty(page);
1208
1209	/* Update high watermark before we lower rss */
1210	update_hiwater_rss(mm);
 
 
 
 
 
 
 
 
 
 
 
1211
1212	if (PageHWPoison(page) && !(flags & TTU_IGNORE_HWPOISON)) {
1213		if (PageAnon(page))
1214			dec_mm_counter(mm, MM_ANONPAGES);
1215		else
1216			dec_mm_counter(mm, MM_FILEPAGES);
1217		set_pte_at(mm, address, pte,
1218				swp_entry_to_pte(make_hwpoison_entry(page)));
1219	} else if (PageAnon(page)) {
1220		swp_entry_t entry = { .val = page_private(page) };
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1221
1222		if (PageSwapCache(page)) {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1223			/*
1224			 * Store the swap location in the pte.
1225			 * See handle_pte_fault() ...
1226			 */
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1227			if (swap_duplicate(entry) < 0) {
1228				set_pte_at(mm, address, pte, pteval);
1229				ret = SWAP_FAIL;
1230				goto out_unmap;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1231			}
1232			if (list_empty(&mm->mmlist)) {
1233				spin_lock(&mmlist_lock);
1234				if (list_empty(&mm->mmlist))
1235					list_add(&mm->mmlist, &init_mm.mmlist);
1236				spin_unlock(&mmlist_lock);
1237			}
1238			dec_mm_counter(mm, MM_ANONPAGES);
1239			inc_mm_counter(mm, MM_SWAPENTS);
1240		} else if (PAGE_MIGRATION) {
 
 
 
 
 
 
 
 
1241			/*
1242			 * Store the pfn of the page in a special migration
1243			 * pte. do_swap_page() will wait until the migration
1244			 * pte is removed and then restart fault handling.
 
 
 
 
 
 
1245			 */
1246			BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION);
1247			entry = make_migration_entry(page, pte_write(pteval));
1248		}
1249		set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
1250		BUG_ON(pte_file(*pte));
1251	} else if (PAGE_MIGRATION && (TTU_ACTION(flags) == TTU_MIGRATION)) {
1252		/* Establish migration entry for a file page */
1253		swp_entry_t entry;
1254		entry = make_migration_entry(page, pte_write(pteval));
1255		set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
1256	} else
1257		dec_mm_counter(mm, MM_FILEPAGES);
1258
1259	page_remove_rmap(page);
1260	page_cache_release(page);
1261
1262out_unmap:
1263	pte_unmap_unlock(pte, ptl);
1264out:
1265	return ret;
 
1266
1267out_mlock:
1268	pte_unmap_unlock(pte, ptl);
 
 
1269
 
 
 
 
1270
1271	/*
1272	 * We need mmap_sem locking, Otherwise VM_LOCKED check makes
1273	 * unstable result and race. Plus, We can't wait here because
1274	 * we now hold anon_vma->mutex or mapping->i_mmap_mutex.
1275	 * if trylock failed, the page remain in evictable lru and later
1276	 * vmscan could retry to move the page to unevictable lru if the
1277	 * page is actually mlocked.
1278	 */
1279	if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
1280		if (vma->vm_flags & VM_LOCKED) {
1281			mlock_vma_page(page);
1282			ret = SWAP_MLOCK;
1283		}
1284		up_read(&vma->vm_mm->mmap_sem);
1285	}
1286	return ret;
 
 
 
 
 
 
 
 
1287}
1288
1289/*
1290 * objrmap doesn't work for nonlinear VMAs because the assumption that
1291 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
1292 * Consequently, given a particular page and its ->index, we cannot locate the
1293 * ptes which are mapping that page without an exhaustive linear search.
1294 *
1295 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
1296 * maps the file to which the target page belongs.  The ->vm_private_data field
1297 * holds the current cursor into that scan.  Successive searches will circulate
1298 * around the vma's virtual address space.
1299 *
1300 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
1301 * more scanning pressure is placed against them as well.   Eventually pages
1302 * will become fully unmapped and are eligible for eviction.
1303 *
1304 * For very sparsely populated VMAs this is a little inefficient - chances are
1305 * there there won't be many ptes located within the scan cluster.  In this case
1306 * maybe we could scan further - to the end of the pte page, perhaps.
1307 *
1308 * Mlocked pages:  check VM_LOCKED under mmap_sem held for read, if we can
1309 * acquire it without blocking.  If vma locked, mlock the pages in the cluster,
1310 * rather than unmapping them.  If we encounter the "check_page" that vmscan is
1311 * trying to unmap, return SWAP_MLOCK, else default SWAP_AGAIN.
1312 */
1313#define CLUSTER_SIZE	min(32*PAGE_SIZE, PMD_SIZE)
1314#define CLUSTER_MASK	(~(CLUSTER_SIZE - 1))
1315
1316static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount,
1317		struct vm_area_struct *vma, struct page *check_page)
1318{
1319	struct mm_struct *mm = vma->vm_mm;
1320	pgd_t *pgd;
1321	pud_t *pud;
1322	pmd_t *pmd;
1323	pte_t *pte;
1324	pte_t pteval;
1325	spinlock_t *ptl;
1326	struct page *page;
1327	unsigned long address;
1328	unsigned long end;
1329	int ret = SWAP_AGAIN;
1330	int locked_vma = 0;
1331
1332	address = (vma->vm_start + cursor) & CLUSTER_MASK;
1333	end = address + CLUSTER_SIZE;
1334	if (address < vma->vm_start)
1335		address = vma->vm_start;
1336	if (end > vma->vm_end)
1337		end = vma->vm_end;
1338
1339	pgd = pgd_offset(mm, address);
1340	if (!pgd_present(*pgd))
1341		return ret;
1342
1343	pud = pud_offset(pgd, address);
1344	if (!pud_present(*pud))
1345		return ret;
 
1346
1347	pmd = pmd_offset(pud, address);
1348	if (!pmd_present(*pmd))
1349		return ret;
 
 
 
1350
1351	/*
1352	 * If we can acquire the mmap_sem for read, and vma is VM_LOCKED,
1353	 * keep the sem while scanning the cluster for mlocking pages.
 
 
 
 
1354	 */
1355	if (down_read_trylock(&vma->vm_mm->mmap_sem)) {
1356		locked_vma = (vma->vm_flags & VM_LOCKED);
1357		if (!locked_vma)
1358			up_read(&vma->vm_mm->mmap_sem); /* don't need it */
 
 
 
 
 
 
 
 
 
1359	}
 
1360
1361	pte = pte_offset_map_lock(mm, pmd, address, &ptl);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1362
1363	/* Update high watermark before we lower rss */
1364	update_hiwater_rss(mm);
1365
1366	for (; address < end; pte++, address += PAGE_SIZE) {
1367		if (!pte_present(*pte))
1368			continue;
1369		page = vm_normal_page(vma, address, *pte);
1370		BUG_ON(!page || PageAnon(page));
1371
1372		if (locked_vma) {
1373			mlock_vma_page(page);   /* no-op if already mlocked */
1374			if (page == check_page)
1375				ret = SWAP_MLOCK;
1376			continue;	/* don't unmap */
 
 
 
 
 
 
 
 
 
 
1377		}
 
 
 
1378
1379		if (ptep_clear_flush_young_notify(vma, address, pte))
1380			continue;
1381
1382		/* Nuke the page table entry. */
1383		flush_cache_page(vma, address, pte_pfn(*pte));
1384		pteval = ptep_clear_flush_notify(vma, address, pte);
 
 
 
 
 
1385
1386		/* If nonlinear, store the file page offset in the pte. */
1387		if (page->index != linear_page_index(vma, address))
1388			set_pte_at(mm, address, pte, pgoff_to_pte(page->index));
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1389
1390		/* Move the dirty bit to the physical page now the pte is gone. */
1391		if (pte_dirty(pteval))
1392			set_page_dirty(page);
1393
1394		page_remove_rmap(page);
1395		page_cache_release(page);
1396		dec_mm_counter(mm, MM_FILEPAGES);
1397		(*mapcount)--;
1398	}
1399	pte_unmap_unlock(pte - 1, ptl);
1400	if (locked_vma)
1401		up_read(&vma->vm_mm->mmap_sem);
1402	return ret;
1403}
1404
1405bool is_vma_temporary_stack(struct vm_area_struct *vma)
1406{
1407	int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
 
 
 
 
 
1408
1409	if (!maybe_stack)
1410		return false;
1411
1412	if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==
1413						VM_STACK_INCOMPLETE_SETUP)
1414		return true;
1415
1416	return false;
1417}
 
 
 
 
1418
1419/**
1420 * try_to_unmap_anon - unmap or unlock anonymous page using the object-based
1421 * rmap method
1422 * @page: the page to unmap/unlock
1423 * @flags: action and flags
1424 *
1425 * Find all the mappings of a page using the mapping pointer and the vma chains
1426 * contained in the anon_vma struct it points to.
1427 *
1428 * This function is only called from try_to_unmap/try_to_munlock for
1429 * anonymous pages.
1430 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1431 * where the page was found will be held for write.  So, we won't recheck
1432 * vm_flags for that VMA.  That should be OK, because that vma shouldn't be
1433 * 'LOCKED.
1434 */
1435static int try_to_unmap_anon(struct page *page, enum ttu_flags flags)
1436{
1437	struct anon_vma *anon_vma;
1438	struct anon_vma_chain *avc;
1439	int ret = SWAP_AGAIN;
 
 
 
 
1440
1441	anon_vma = page_lock_anon_vma(page);
1442	if (!anon_vma)
1443		return ret;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1444
1445	list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
1446		struct vm_area_struct *vma = avc->vma;
1447		unsigned long address;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1448
1449		/*
1450		 * During exec, a temporary VMA is setup and later moved.
1451		 * The VMA is moved under the anon_vma lock but not the
1452		 * page tables leading to a race where migration cannot
1453		 * find the migration ptes. Rather than increasing the
1454		 * locking requirements of exec(), migration skips
1455		 * temporary VMAs until after exec() completes.
1456		 */
1457		if (PAGE_MIGRATION && (flags & TTU_MIGRATION) &&
1458				is_vma_temporary_stack(vma))
1459			continue;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1460
1461		address = vma_address(page, vma);
1462		if (address == -EFAULT)
1463			continue;
1464		ret = try_to_unmap_one(page, vma, address, flags);
1465		if (ret != SWAP_AGAIN || !page_mapped(page))
1466			break;
 
1467	}
1468
1469	page_unlock_anon_vma(anon_vma);
 
1470	return ret;
1471}
1472
1473/**
1474 * try_to_unmap_file - unmap/unlock file page using the object-based rmap method
1475 * @page: the page to unmap/unlock
1476 * @flags: action and flags
1477 *
1478 * Find all the mappings of a page using the mapping pointer and the vma chains
1479 * contained in the address_space struct it points to.
1480 *
1481 * This function is only called from try_to_unmap/try_to_munlock for
1482 * object-based pages.
1483 * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
1484 * where the page was found will be held for write.  So, we won't recheck
1485 * vm_flags for that VMA.  That should be OK, because that vma shouldn't be
1486 * 'LOCKED.
1487 */
1488static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
1489{
1490	struct address_space *mapping = page->mapping;
1491	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1492	struct vm_area_struct *vma;
1493	struct prio_tree_iter iter;
1494	int ret = SWAP_AGAIN;
1495	unsigned long cursor;
1496	unsigned long max_nl_cursor = 0;
1497	unsigned long max_nl_size = 0;
1498	unsigned int mapcount;
1499
1500	mutex_lock(&mapping->i_mmap_mutex);
1501	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
1502		unsigned long address = vma_address(page, vma);
1503		if (address == -EFAULT)
1504			continue;
1505		ret = try_to_unmap_one(page, vma, address, flags);
1506		if (ret != SWAP_AGAIN || !page_mapped(page))
1507			goto out;
1508	}
1509
1510	if (list_empty(&mapping->i_mmap_nonlinear))
1511		goto out;
1512
1513	/*
1514	 * We don't bother to try to find the munlocked page in nonlinears.
1515	 * It's costly. Instead, later, page reclaim logic may call
1516	 * try_to_unmap(TTU_MUNLOCK) and recover PG_mlocked lazily.
1517	 */
1518	if (TTU_ACTION(flags) == TTU_MUNLOCK)
1519		goto out;
1520
1521	list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1522						shared.vm_set.list) {
1523		cursor = (unsigned long) vma->vm_private_data;
1524		if (cursor > max_nl_cursor)
1525			max_nl_cursor = cursor;
1526		cursor = vma->vm_end - vma->vm_start;
1527		if (cursor > max_nl_size)
1528			max_nl_size = cursor;
1529	}
1530
1531	if (max_nl_size == 0) {	/* all nonlinears locked or reserved ? */
1532		ret = SWAP_FAIL;
1533		goto out;
1534	}
1535
1536	/*
1537	 * We don't try to search for this page in the nonlinear vmas,
1538	 * and page_referenced wouldn't have found it anyway.  Instead
1539	 * just walk the nonlinear vmas trying to age and unmap some.
1540	 * The mapcount of the page we came in with is irrelevant,
1541	 * but even so use it as a guide to how hard we should try?
 
1542	 */
1543	mapcount = page_mapcount(page);
1544	if (!mapcount)
1545		goto out;
1546	cond_resched();
1547
1548	max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
1549	if (max_nl_cursor == 0)
1550		max_nl_cursor = CLUSTER_SIZE;
1551
1552	do {
1553		list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
1554						shared.vm_set.list) {
1555			cursor = (unsigned long) vma->vm_private_data;
1556			while ( cursor < max_nl_cursor &&
1557				cursor < vma->vm_end - vma->vm_start) {
1558				if (try_to_unmap_cluster(cursor, &mapcount,
1559						vma, page) == SWAP_MLOCK)
1560					ret = SWAP_MLOCK;
1561				cursor += CLUSTER_SIZE;
1562				vma->vm_private_data = (void *) cursor;
1563				if ((int)mapcount <= 0)
1564					goto out;
1565			}
1566			vma->vm_private_data = (void *) max_nl_cursor;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1567		}
1568		cond_resched();
1569		max_nl_cursor += CLUSTER_SIZE;
1570	} while (max_nl_cursor <= max_nl_size);
1571
1572	/*
1573	 * Don't loop forever (perhaps all the remaining pages are
1574	 * in locked vmas).  Reset cursor on all unreserved nonlinear
1575	 * vmas, now forgetting on which ones it had fallen behind.
1576	 */
1577	list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list)
1578		vma->vm_private_data = NULL;
1579out:
1580	mutex_unlock(&mapping->i_mmap_mutex);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1581	return ret;
1582}
1583
1584/**
1585 * try_to_unmap - try to remove all page table mappings to a page
1586 * @page: the page to get unmapped
1587 * @flags: action and flags
 
 
1588 *
1589 * Tries to remove all the page table entries which are mapping this
1590 * page, used in the pageout path.  Caller must hold the page lock.
1591 * Return values are:
1592 *
1593 * SWAP_SUCCESS	- we succeeded in removing all mappings
1594 * SWAP_AGAIN	- we missed a mapping, try again later
1595 * SWAP_FAIL	- the page is unswappable
1596 * SWAP_MLOCK	- page is mlocked.
1597 */
1598int try_to_unmap(struct page *page, enum ttu_flags flags)
1599{
1600	int ret;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1601
1602	BUG_ON(!PageLocked(page));
1603	VM_BUG_ON(!PageHuge(page) && PageTransHuge(page));
1604
1605	if (unlikely(PageKsm(page)))
1606		ret = try_to_unmap_ksm(page, flags);
1607	else if (PageAnon(page))
1608		ret = try_to_unmap_anon(page, flags);
1609	else
1610		ret = try_to_unmap_file(page, flags);
1611	if (ret != SWAP_MLOCK && !page_mapped(page))
1612		ret = SWAP_SUCCESS;
1613	return ret;
1614}
1615
1616/**
1617 * try_to_munlock - try to munlock a page
1618 * @page: the page to be munlocked
1619 *
1620 * Called from munlock code.  Checks all of the VMAs mapping the page
1621 * to make sure nobody else has this page mlocked. The page will be
1622 * returned with PG_mlocked cleared if no other vmas have it mlocked.
1623 *
1624 * Return values are:
1625 *
1626 * SWAP_AGAIN	- no vma is holding page mlocked, or,
1627 * SWAP_AGAIN	- page mapped in mlocked vma -- couldn't acquire mmap sem
1628 * SWAP_FAIL	- page cannot be located at present
1629 * SWAP_MLOCK	- page is now mlocked.
1630 */
1631int try_to_munlock(struct page *page)
1632{
1633	VM_BUG_ON(!PageLocked(page) || PageLRU(page));
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1634
1635	if (unlikely(PageKsm(page)))
1636		return try_to_unmap_ksm(page, TTU_MUNLOCK);
1637	else if (PageAnon(page))
1638		return try_to_unmap_anon(page, TTU_MUNLOCK);
1639	else
1640		return try_to_unmap_file(page, TTU_MUNLOCK);
 
 
1641}
 
 
1642
1643void __put_anon_vma(struct anon_vma *anon_vma)
1644{
1645	struct anon_vma *root = anon_vma->root;
1646
 
1647	if (root != anon_vma && atomic_dec_and_test(&root->refcount))
1648		anon_vma_free(root);
1649
1650	anon_vma_free(anon_vma);
1651}
1652
1653#ifdef CONFIG_MIGRATION
1654/*
1655 * rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file():
1656 * Called by migrate.c to remove migration ptes, but might be used more later.
1657 */
1658static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
1659		struct vm_area_struct *, unsigned long, void *), void *arg)
1660{
1661	struct anon_vma *anon_vma;
1662	struct anon_vma_chain *avc;
1663	int ret = SWAP_AGAIN;
 
1664
1665	/*
1666	 * Note: remove_migration_ptes() cannot use page_lock_anon_vma()
1667	 * because that depends on page_mapped(); but not all its usages
1668	 * are holding mmap_sem. Users without mmap_sem are required to
1669	 * take a reference count to prevent the anon_vma disappearing
1670	 */
1671	anon_vma = page_anon_vma(page);
1672	if (!anon_vma)
1673		return ret;
1674	anon_vma_lock(anon_vma);
1675	list_for_each_entry(avc, &anon_vma->head, same_anon_vma) {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1676		struct vm_area_struct *vma = avc->vma;
1677		unsigned long address = vma_address(page, vma);
1678		if (address == -EFAULT)
 
 
 
 
1679			continue;
1680		ret = rmap_one(page, vma, address, arg);
1681		if (ret != SWAP_AGAIN)
 
 
1682			break;
1683	}
1684	anon_vma_unlock(anon_vma);
1685	return ret;
 
1686}
1687
1688static int rmap_walk_file(struct page *page, int (*rmap_one)(struct page *,
1689		struct vm_area_struct *, unsigned long, void *), void *arg)
 
 
 
 
 
 
 
 
 
1690{
1691	struct address_space *mapping = page->mapping;
1692	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
1693	struct vm_area_struct *vma;
1694	struct prio_tree_iter iter;
1695	int ret = SWAP_AGAIN;
 
 
 
 
 
 
1696
1697	if (!mapping)
1698		return ret;
1699	mutex_lock(&mapping->i_mmap_mutex);
1700	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
1701		unsigned long address = vma_address(page, vma);
1702		if (address == -EFAULT)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1703			continue;
1704		ret = rmap_one(page, vma, address, arg);
1705		if (ret != SWAP_AGAIN)
1706			break;
 
 
1707	}
1708	/*
1709	 * No nonlinear handling: being always shared, nonlinear vmas
1710	 * never contain migration ptes.  Decide what to do about this
1711	 * limitation to linear when we need rmap_walk() on nonlinear.
1712	 */
1713	mutex_unlock(&mapping->i_mmap_mutex);
1714	return ret;
1715}
1716
1717int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
1718		struct vm_area_struct *, unsigned long, void *), void *arg)
1719{
1720	VM_BUG_ON(!PageLocked(page));
 
 
 
 
 
 
1721
1722	if (unlikely(PageKsm(page)))
1723		return rmap_walk_ksm(page, rmap_one, arg);
1724	else if (PageAnon(page))
1725		return rmap_walk_anon(page, rmap_one, arg);
 
 
 
1726	else
1727		return rmap_walk_file(page, rmap_one, arg);
1728}
1729#endif /* CONFIG_MIGRATION */
1730
1731#ifdef CONFIG_HUGETLB_PAGE
1732/*
1733 * The following three functions are for anonymous (private mapped) hugepages.
1734 * Unlike common anonymous pages, anonymous hugepages have no accounting code
1735 * and no lru code, because we handle hugepages differently from common pages.
1736 */
1737static void __hugepage_set_anon_rmap(struct page *page,
1738	struct vm_area_struct *vma, unsigned long address, int exclusive)
1739{
1740	struct anon_vma *anon_vma = vma->anon_vma;
1741
1742	BUG_ON(!anon_vma);
1743
1744	if (PageAnon(page))
1745		return;
1746	if (!exclusive)
1747		anon_vma = anon_vma->root;
1748
1749	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1750	page->mapping = (struct address_space *) anon_vma;
1751	page->index = linear_page_index(vma, address);
1752}
1753
1754void hugepage_add_anon_rmap(struct page *page,
1755			    struct vm_area_struct *vma, unsigned long address)
1756{
1757	struct anon_vma *anon_vma = vma->anon_vma;
1758	int first;
1759
1760	BUG_ON(!PageLocked(page));
1761	BUG_ON(!anon_vma);
1762	/* address might be in next vma when migration races vma_adjust */
1763	first = atomic_inc_and_test(&page->_mapcount);
1764	if (first)
1765		__hugepage_set_anon_rmap(page, vma, address, 0);
1766}
1767
1768void hugepage_add_new_anon_rmap(struct page *page,
1769			struct vm_area_struct *vma, unsigned long address)
1770{
1771	BUG_ON(address < vma->vm_start || address >= vma->vm_end);
1772	atomic_set(&page->_mapcount, 0);
1773	__hugepage_set_anon_rmap(page, vma, address, 1);
 
 
 
1774}
1775#endif /* CONFIG_HUGETLB_PAGE */
v6.8
   1/*
   2 * mm/rmap.c - physical to virtual reverse mappings
   3 *
   4 * Copyright 2001, Rik van Riel <riel@conectiva.com.br>
   5 * Released under the General Public License (GPL).
   6 *
   7 * Simple, low overhead reverse mapping scheme.
   8 * Please try to keep this thing as modular as possible.
   9 *
  10 * Provides methods for unmapping each kind of mapped page:
  11 * the anon methods track anonymous pages, and
  12 * the file methods track pages belonging to an inode.
  13 *
  14 * Original design by Rik van Riel <riel@conectiva.com.br> 2001
  15 * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004
  16 * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004
  17 * Contributions by Hugh Dickins 2003, 2004
  18 */
  19
  20/*
  21 * Lock ordering in mm:
  22 *
  23 * inode->i_rwsem	(while writing or truncating, not reading or faulting)
  24 *   mm->mmap_lock
  25 *     mapping->invalidate_lock (in filemap_fault)
  26 *       page->flags PG_locked (lock_page)
  27 *         hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share, see hugetlbfs below)
  28 *           vma_start_write
  29 *             mapping->i_mmap_rwsem
  30 *               anon_vma->rwsem
  31 *                 mm->page_table_lock or pte_lock
  32 *                   swap_lock (in swap_duplicate, swap_info_get)
  33 *                     mmlist_lock (in mmput, drain_mmlist and others)
  34 *                     mapping->private_lock (in block_dirty_folio)
  35 *                       folio_lock_memcg move_lock (in block_dirty_folio)
  36 *                         i_pages lock (widely used)
  37 *                           lruvec->lru_lock (in folio_lruvec_lock_irq)
  38 *                     inode->i_lock (in set_page_dirty's __mark_inode_dirty)
  39 *                     bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty)
  40 *                       sb_lock (within inode_lock in fs/fs-writeback.c)
  41 *                       i_pages lock (widely used, in set_page_dirty,
  42 *                                 in arch-dependent flush_dcache_mmap_lock,
  43 *                                 within bdi.wb->list_lock in __sync_single_inode)
  44 *
  45 * anon_vma->rwsem,mapping->i_mmap_rwsem   (memory_failure, collect_procs_anon)
  46 *   ->tasklist_lock
  47 *     pte map lock
  48 *
  49 * hugetlbfs PageHuge() take locks in this order:
  50 *   hugetlb_fault_mutex (hugetlbfs specific page fault mutex)
  51 *     vma_lock (hugetlb specific lock for pmd_sharing)
  52 *       mapping->i_mmap_rwsem (also used for hugetlb pmd sharing)
  53 *         page->flags PG_locked (lock_page)
  54 */
  55
  56#include <linux/mm.h>
  57#include <linux/sched/mm.h>
  58#include <linux/sched/task.h>
  59#include <linux/pagemap.h>
  60#include <linux/swap.h>
  61#include <linux/swapops.h>
  62#include <linux/slab.h>
  63#include <linux/init.h>
  64#include <linux/ksm.h>
  65#include <linux/rmap.h>
  66#include <linux/rcupdate.h>
  67#include <linux/export.h>
  68#include <linux/memcontrol.h>
  69#include <linux/mmu_notifier.h>
  70#include <linux/migrate.h>
  71#include <linux/hugetlb.h>
  72#include <linux/huge_mm.h>
  73#include <linux/backing-dev.h>
  74#include <linux/page_idle.h>
  75#include <linux/memremap.h>
  76#include <linux/userfaultfd_k.h>
  77#include <linux/mm_inline.h>
  78
  79#include <asm/tlbflush.h>
  80
  81#define CREATE_TRACE_POINTS
  82#include <trace/events/tlb.h>
  83#include <trace/events/migrate.h>
  84
  85#include "internal.h"
  86
  87static struct kmem_cache *anon_vma_cachep;
  88static struct kmem_cache *anon_vma_chain_cachep;
  89
  90static inline struct anon_vma *anon_vma_alloc(void)
  91{
  92	struct anon_vma *anon_vma;
  93
  94	anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
  95	if (anon_vma) {
  96		atomic_set(&anon_vma->refcount, 1);
  97		anon_vma->num_children = 0;
  98		anon_vma->num_active_vmas = 0;
  99		anon_vma->parent = anon_vma;
 100		/*
 101		 * Initialise the anon_vma root to point to itself. If called
 102		 * from fork, the root will be reset to the parents anon_vma.
 103		 */
 104		anon_vma->root = anon_vma;
 105	}
 106
 107	return anon_vma;
 108}
 109
 110static inline void anon_vma_free(struct anon_vma *anon_vma)
 111{
 112	VM_BUG_ON(atomic_read(&anon_vma->refcount));
 113
 114	/*
 115	 * Synchronize against folio_lock_anon_vma_read() such that
 116	 * we can safely hold the lock without the anon_vma getting
 117	 * freed.
 118	 *
 119	 * Relies on the full mb implied by the atomic_dec_and_test() from
 120	 * put_anon_vma() against the acquire barrier implied by
 121	 * down_read_trylock() from folio_lock_anon_vma_read(). This orders:
 122	 *
 123	 * folio_lock_anon_vma_read()	VS	put_anon_vma()
 124	 *   down_read_trylock()		  atomic_dec_and_test()
 125	 *   LOCK				  MB
 126	 *   atomic_read()			  rwsem_is_locked()
 127	 *
 128	 * LOCK should suffice since the actual taking of the lock must
 129	 * happen _before_ what follows.
 130	 */
 131	might_sleep();
 132	if (rwsem_is_locked(&anon_vma->root->rwsem)) {
 133		anon_vma_lock_write(anon_vma);
 134		anon_vma_unlock_write(anon_vma);
 135	}
 136
 137	kmem_cache_free(anon_vma_cachep, anon_vma);
 138}
 139
 140static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp)
 141{
 142	return kmem_cache_alloc(anon_vma_chain_cachep, gfp);
 143}
 144
 145static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain)
 146{
 147	kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain);
 148}
 149
 150static void anon_vma_chain_link(struct vm_area_struct *vma,
 151				struct anon_vma_chain *avc,
 152				struct anon_vma *anon_vma)
 153{
 154	avc->vma = vma;
 155	avc->anon_vma = anon_vma;
 156	list_add(&avc->same_vma, &vma->anon_vma_chain);
 157	anon_vma_interval_tree_insert(avc, &anon_vma->rb_root);
 158}
 159
 160/**
 161 * __anon_vma_prepare - attach an anon_vma to a memory region
 162 * @vma: the memory region in question
 163 *
 164 * This makes sure the memory mapping described by 'vma' has
 165 * an 'anon_vma' attached to it, so that we can associate the
 166 * anonymous pages mapped into it with that anon_vma.
 167 *
 168 * The common case will be that we already have one, which
 169 * is handled inline by anon_vma_prepare(). But if
 170 * not we either need to find an adjacent mapping that we
 171 * can re-use the anon_vma from (very common when the only
 172 * reason for splitting a vma has been mprotect()), or we
 173 * allocate a new one.
 174 *
 175 * Anon-vma allocations are very subtle, because we may have
 176 * optimistically looked up an anon_vma in folio_lock_anon_vma_read()
 177 * and that may actually touch the rwsem even in the newly
 178 * allocated vma (it depends on RCU to make sure that the
 179 * anon_vma isn't actually destroyed).
 180 *
 181 * As a result, we need to do proper anon_vma locking even
 182 * for the new allocation. At the same time, we do not want
 183 * to do any locking for the common case of already having
 184 * an anon_vma.
 185 *
 186 * This must be called with the mmap_lock held for reading.
 187 */
 188int __anon_vma_prepare(struct vm_area_struct *vma)
 189{
 190	struct mm_struct *mm = vma->vm_mm;
 191	struct anon_vma *anon_vma, *allocated;
 192	struct anon_vma_chain *avc;
 193
 194	might_sleep();
 
 
 
 
 
 
 
 195
 196	avc = anon_vma_chain_alloc(GFP_KERNEL);
 197	if (!avc)
 198		goto out_enomem;
 199
 200	anon_vma = find_mergeable_anon_vma(vma);
 201	allocated = NULL;
 202	if (!anon_vma) {
 203		anon_vma = anon_vma_alloc();
 204		if (unlikely(!anon_vma))
 205			goto out_enomem_free_avc;
 206		anon_vma->num_children++; /* self-parent link for new root */
 207		allocated = anon_vma;
 208	}
 209
 210	anon_vma_lock_write(anon_vma);
 211	/* page_table_lock to protect against threads */
 212	spin_lock(&mm->page_table_lock);
 213	if (likely(!vma->anon_vma)) {
 214		vma->anon_vma = anon_vma;
 215		anon_vma_chain_link(vma, avc, anon_vma);
 216		anon_vma->num_active_vmas++;
 217		allocated = NULL;
 218		avc = NULL;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 219	}
 220	spin_unlock(&mm->page_table_lock);
 221	anon_vma_unlock_write(anon_vma);
 222
 223	if (unlikely(allocated))
 224		put_anon_vma(allocated);
 225	if (unlikely(avc))
 226		anon_vma_chain_free(avc);
 227
 228	return 0;
 229
 230 out_enomem_free_avc:
 231	anon_vma_chain_free(avc);
 232 out_enomem:
 233	return -ENOMEM;
 234}
 235
 236/*
 237 * This is a useful helper function for locking the anon_vma root as
 238 * we traverse the vma->anon_vma_chain, looping over anon_vma's that
 239 * have the same vma.
 240 *
 241 * Such anon_vma's should have the same root, so you'd expect to see
 242 * just a single mutex_lock for the whole traversal.
 243 */
 244static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma)
 245{
 246	struct anon_vma *new_root = anon_vma->root;
 247	if (new_root != root) {
 248		if (WARN_ON_ONCE(root))
 249			up_write(&root->rwsem);
 250		root = new_root;
 251		down_write(&root->rwsem);
 252	}
 253	return root;
 254}
 255
 256static inline void unlock_anon_vma_root(struct anon_vma *root)
 257{
 258	if (root)
 259		up_write(&root->rwsem);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 260}
 261
 262/*
 263 * Attach the anon_vmas from src to dst.
 264 * Returns 0 on success, -ENOMEM on failure.
 265 *
 266 * anon_vma_clone() is called by vma_expand(), vma_merge(), __split_vma(),
 267 * copy_vma() and anon_vma_fork(). The first four want an exact copy of src,
 268 * while the last one, anon_vma_fork(), may try to reuse an existing anon_vma to
 269 * prevent endless growth of anon_vma. Since dst->anon_vma is set to NULL before
 270 * call, we can identify this case by checking (!dst->anon_vma &&
 271 * src->anon_vma).
 272 *
 273 * If (!dst->anon_vma && src->anon_vma) is true, this function tries to find
 274 * and reuse existing anon_vma which has no vmas and only one child anon_vma.
 275 * This prevents degradation of anon_vma hierarchy to endless linear chain in
 276 * case of constantly forking task. On the other hand, an anon_vma with more
 277 * than one child isn't reused even if there was no alive vma, thus rmap
 278 * walker has a good chance of avoiding scanning the whole hierarchy when it
 279 * searches where page is mapped.
 280 */
 281int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src)
 282{
 283	struct anon_vma_chain *avc, *pavc;
 284	struct anon_vma *root = NULL;
 285
 286	list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) {
 287		struct anon_vma *anon_vma;
 288
 289		avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN);
 290		if (unlikely(!avc)) {
 291			unlock_anon_vma_root(root);
 292			root = NULL;
 293			avc = anon_vma_chain_alloc(GFP_KERNEL);
 294			if (!avc)
 295				goto enomem_failure;
 296		}
 297		anon_vma = pavc->anon_vma;
 298		root = lock_anon_vma_root(root, anon_vma);
 299		anon_vma_chain_link(dst, avc, anon_vma);
 300
 301		/*
 302		 * Reuse existing anon_vma if it has no vma and only one
 303		 * anon_vma child.
 304		 *
 305		 * Root anon_vma is never reused:
 306		 * it has self-parent reference and at least one child.
 307		 */
 308		if (!dst->anon_vma && src->anon_vma &&
 309		    anon_vma->num_children < 2 &&
 310		    anon_vma->num_active_vmas == 0)
 311			dst->anon_vma = anon_vma;
 312	}
 313	if (dst->anon_vma)
 314		dst->anon_vma->num_active_vmas++;
 315	unlock_anon_vma_root(root);
 316	return 0;
 317
 318 enomem_failure:
 319	/*
 320	 * dst->anon_vma is dropped here otherwise its num_active_vmas can
 321	 * be incorrectly decremented in unlink_anon_vmas().
 322	 * We can safely do this because callers of anon_vma_clone() don't care
 323	 * about dst->anon_vma if anon_vma_clone() failed.
 324	 */
 325	dst->anon_vma = NULL;
 326	unlink_anon_vmas(dst);
 327	return -ENOMEM;
 328}
 329
 330/*
 331 * Attach vma to its own anon_vma, as well as to the anon_vmas that
 332 * the corresponding VMA in the parent process is attached to.
 333 * Returns 0 on success, non-zero on failure.
 334 */
 335int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma)
 336{
 337	struct anon_vma_chain *avc;
 338	struct anon_vma *anon_vma;
 339	int error;
 340
 341	/* Don't bother if the parent process has no anon_vma here. */
 342	if (!pvma->anon_vma)
 343		return 0;
 344
 345	/* Drop inherited anon_vma, we'll reuse existing or allocate new. */
 346	vma->anon_vma = NULL;
 347
 348	/*
 349	 * First, attach the new VMA to the parent VMA's anon_vmas,
 350	 * so rmap can find non-COWed pages in child processes.
 351	 */
 352	error = anon_vma_clone(vma, pvma);
 353	if (error)
 354		return error;
 355
 356	/* An existing anon_vma has been reused, all done then. */
 357	if (vma->anon_vma)
 358		return 0;
 359
 360	/* Then add our own anon_vma. */
 361	anon_vma = anon_vma_alloc();
 362	if (!anon_vma)
 363		goto out_error;
 364	anon_vma->num_active_vmas++;
 365	avc = anon_vma_chain_alloc(GFP_KERNEL);
 366	if (!avc)
 367		goto out_error_free_anon_vma;
 368
 369	/*
 370	 * The root anon_vma's rwsem is the lock actually used when we
 371	 * lock any of the anon_vmas in this anon_vma tree.
 372	 */
 373	anon_vma->root = pvma->anon_vma->root;
 374	anon_vma->parent = pvma->anon_vma;
 375	/*
 376	 * With refcounts, an anon_vma can stay around longer than the
 377	 * process it belongs to. The root anon_vma needs to be pinned until
 378	 * this anon_vma is freed, because the lock lives in the root.
 379	 */
 380	get_anon_vma(anon_vma->root);
 381	/* Mark this anon_vma as the one where our new (COWed) pages go. */
 382	vma->anon_vma = anon_vma;
 383	anon_vma_lock_write(anon_vma);
 384	anon_vma_chain_link(vma, avc, anon_vma);
 385	anon_vma->parent->num_children++;
 386	anon_vma_unlock_write(anon_vma);
 387
 388	return 0;
 389
 390 out_error_free_anon_vma:
 391	put_anon_vma(anon_vma);
 392 out_error:
 393	unlink_anon_vmas(vma);
 394	return -ENOMEM;
 395}
 396
 397void unlink_anon_vmas(struct vm_area_struct *vma)
 398{
 399	struct anon_vma_chain *avc, *next;
 400	struct anon_vma *root = NULL;
 401
 402	/*
 403	 * Unlink each anon_vma chained to the VMA.  This list is ordered
 404	 * from newest to oldest, ensuring the root anon_vma gets freed last.
 405	 */
 406	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
 407		struct anon_vma *anon_vma = avc->anon_vma;
 408
 409		root = lock_anon_vma_root(root, anon_vma);
 410		anon_vma_interval_tree_remove(avc, &anon_vma->rb_root);
 411
 412		/*
 413		 * Leave empty anon_vmas on the list - we'll need
 414		 * to free them outside the lock.
 415		 */
 416		if (RB_EMPTY_ROOT(&anon_vma->rb_root.rb_root)) {
 417			anon_vma->parent->num_children--;
 418			continue;
 419		}
 420
 421		list_del(&avc->same_vma);
 422		anon_vma_chain_free(avc);
 423	}
 424	if (vma->anon_vma) {
 425		vma->anon_vma->num_active_vmas--;
 426
 427		/*
 428		 * vma would still be needed after unlink, and anon_vma will be prepared
 429		 * when handle fault.
 430		 */
 431		vma->anon_vma = NULL;
 432	}
 433	unlock_anon_vma_root(root);
 434
 435	/*
 436	 * Iterate the list once more, it now only contains empty and unlinked
 437	 * anon_vmas, destroy them. Could not do before due to __put_anon_vma()
 438	 * needing to write-acquire the anon_vma->root->rwsem.
 439	 */
 440	list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) {
 441		struct anon_vma *anon_vma = avc->anon_vma;
 442
 443		VM_WARN_ON(anon_vma->num_children);
 444		VM_WARN_ON(anon_vma->num_active_vmas);
 445		put_anon_vma(anon_vma);
 446
 447		list_del(&avc->same_vma);
 448		anon_vma_chain_free(avc);
 449	}
 450}
 451
 452static void anon_vma_ctor(void *data)
 453{
 454	struct anon_vma *anon_vma = data;
 455
 456	init_rwsem(&anon_vma->rwsem);
 457	atomic_set(&anon_vma->refcount, 0);
 458	anon_vma->rb_root = RB_ROOT_CACHED;
 459}
 460
 461void __init anon_vma_init(void)
 462{
 463	anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
 464			0, SLAB_TYPESAFE_BY_RCU|SLAB_PANIC|SLAB_ACCOUNT,
 465			anon_vma_ctor);
 466	anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain,
 467			SLAB_PANIC|SLAB_ACCOUNT);
 468}
 469
 470/*
 471 * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
 472 *
 473 * Since there is no serialization what so ever against folio_remove_rmap_*()
 474 * the best this function can do is return a refcount increased anon_vma
 475 * that might have been relevant to this page.
 476 *
 477 * The page might have been remapped to a different anon_vma or the anon_vma
 478 * returned may already be freed (and even reused).
 479 *
 480 * In case it was remapped to a different anon_vma, the new anon_vma will be a
 481 * child of the old anon_vma, and the anon_vma lifetime rules will therefore
 482 * ensure that any anon_vma obtained from the page will still be valid for as
 483 * long as we observe page_mapped() [ hence all those page_mapped() tests ].
 484 *
 485 * All users of this function must be very careful when walking the anon_vma
 486 * chain and verify that the page in question is indeed mapped in it
 487 * [ something equivalent to page_mapped_in_vma() ].
 488 *
 489 * Since anon_vma's slab is SLAB_TYPESAFE_BY_RCU and we know from
 490 * folio_remove_rmap_*() that the anon_vma pointer from page->mapping is valid
 491 * if there is a mapcount, we can dereference the anon_vma after observing
 492 * those.
 493 *
 494 * NOTE: the caller should normally hold folio lock when calling this.  If
 495 * not, the caller needs to double check the anon_vma didn't change after
 496 * taking the anon_vma lock for either read or write (UFFDIO_MOVE can modify it
 497 * concurrently without folio lock protection). See folio_lock_anon_vma_read()
 498 * which has already covered that, and comment above remap_pages().
 499 */
 500struct anon_vma *folio_get_anon_vma(struct folio *folio)
 501{
 502	struct anon_vma *anon_vma = NULL;
 503	unsigned long anon_mapping;
 504
 505	rcu_read_lock();
 506	anon_mapping = (unsigned long)READ_ONCE(folio->mapping);
 507	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
 508		goto out;
 509	if (!folio_mapped(folio))
 510		goto out;
 511
 512	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
 513	if (!atomic_inc_not_zero(&anon_vma->refcount)) {
 514		anon_vma = NULL;
 515		goto out;
 516	}
 517
 518	/*
 519	 * If this folio is still mapped, then its anon_vma cannot have been
 520	 * freed.  But if it has been unmapped, we have no security against the
 521	 * anon_vma structure being freed and reused (for another anon_vma:
 522	 * SLAB_TYPESAFE_BY_RCU guarantees that - so the atomic_inc_not_zero()
 523	 * above cannot corrupt).
 524	 */
 525	if (!folio_mapped(folio)) {
 526		rcu_read_unlock();
 527		put_anon_vma(anon_vma);
 528		return NULL;
 529	}
 530out:
 531	rcu_read_unlock();
 532
 533	return anon_vma;
 534}
 535
 536/*
 537 * Similar to folio_get_anon_vma() except it locks the anon_vma.
 538 *
 539 * Its a little more complex as it tries to keep the fast path to a single
 540 * atomic op -- the trylock. If we fail the trylock, we fall back to getting a
 541 * reference like with folio_get_anon_vma() and then block on the mutex
 542 * on !rwc->try_lock case.
 543 */
 544struct anon_vma *folio_lock_anon_vma_read(struct folio *folio,
 545					  struct rmap_walk_control *rwc)
 546{
 547	struct anon_vma *anon_vma = NULL;
 548	struct anon_vma *root_anon_vma;
 549	unsigned long anon_mapping;
 550
 551retry:
 552	rcu_read_lock();
 553	anon_mapping = (unsigned long)READ_ONCE(folio->mapping);
 554	if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
 555		goto out;
 556	if (!folio_mapped(folio))
 557		goto out;
 558
 559	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
 560	root_anon_vma = READ_ONCE(anon_vma->root);
 561	if (down_read_trylock(&root_anon_vma->rwsem)) {
 562		/*
 563		 * folio_move_anon_rmap() might have changed the anon_vma as we
 564		 * might not hold the folio lock here.
 565		 */
 566		if (unlikely((unsigned long)READ_ONCE(folio->mapping) !=
 567			     anon_mapping)) {
 568			up_read(&root_anon_vma->rwsem);
 569			rcu_read_unlock();
 570			goto retry;
 571		}
 572
 573		/*
 574		 * If the folio is still mapped, then this anon_vma is still
 575		 * its anon_vma, and holding the mutex ensures that it will
 576		 * not go away, see anon_vma_free().
 577		 */
 578		if (!folio_mapped(folio)) {
 579			up_read(&root_anon_vma->rwsem);
 580			anon_vma = NULL;
 581		}
 582		goto out;
 583	}
 584
 585	if (rwc && rwc->try_lock) {
 586		anon_vma = NULL;
 587		rwc->contended = true;
 588		goto out;
 589	}
 590
 591	/* trylock failed, we got to sleep */
 592	if (!atomic_inc_not_zero(&anon_vma->refcount)) {
 593		anon_vma = NULL;
 594		goto out;
 595	}
 596
 597	if (!folio_mapped(folio)) {
 598		rcu_read_unlock();
 599		put_anon_vma(anon_vma);
 600		return NULL;
 
 601	}
 602
 603	/* we pinned the anon_vma, its safe to sleep */
 604	rcu_read_unlock();
 605	anon_vma_lock_read(anon_vma);
 606
 607	/*
 608	 * folio_move_anon_rmap() might have changed the anon_vma as we might
 609	 * not hold the folio lock here.
 610	 */
 611	if (unlikely((unsigned long)READ_ONCE(folio->mapping) !=
 612		     anon_mapping)) {
 613		anon_vma_unlock_read(anon_vma);
 614		put_anon_vma(anon_vma);
 615		anon_vma = NULL;
 616		goto retry;
 617	}
 618
 619	if (atomic_dec_and_test(&anon_vma->refcount)) {
 620		/*
 621		 * Oops, we held the last refcount, release the lock
 622		 * and bail -- can't simply use put_anon_vma() because
 623		 * we'll deadlock on the anon_vma_lock_write() recursion.
 624		 */
 625		anon_vma_unlock_read(anon_vma);
 626		__put_anon_vma(anon_vma);
 627		anon_vma = NULL;
 628	}
 629
 630	return anon_vma;
 631
 632out:
 633	rcu_read_unlock();
 634	return anon_vma;
 635}
 636
 637#ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
 638/*
 639 * Flush TLB entries for recently unmapped pages from remote CPUs. It is
 640 * important if a PTE was dirty when it was unmapped that it's flushed
 641 * before any IO is initiated on the page to prevent lost writes. Similarly,
 642 * it must be flushed before freeing to prevent data leakage.
 643 */
 644void try_to_unmap_flush(void)
 645{
 646	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
 647
 648	if (!tlb_ubc->flush_required)
 649		return;
 650
 651	arch_tlbbatch_flush(&tlb_ubc->arch);
 652	tlb_ubc->flush_required = false;
 653	tlb_ubc->writable = false;
 654}
 655
 656/* Flush iff there are potentially writable TLB entries that can race with IO */
 657void try_to_unmap_flush_dirty(void)
 658{
 659	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
 660
 661	if (tlb_ubc->writable)
 662		try_to_unmap_flush();
 663}
 664
 665/*
 666 * Bits 0-14 of mm->tlb_flush_batched record pending generations.
 667 * Bits 16-30 of mm->tlb_flush_batched bit record flushed generations.
 668 */
 669#define TLB_FLUSH_BATCH_FLUSHED_SHIFT	16
 670#define TLB_FLUSH_BATCH_PENDING_MASK			\
 671	((1 << (TLB_FLUSH_BATCH_FLUSHED_SHIFT - 1)) - 1)
 672#define TLB_FLUSH_BATCH_PENDING_LARGE			\
 673	(TLB_FLUSH_BATCH_PENDING_MASK / 2)
 674
 675static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval,
 676				      unsigned long uaddr)
 677{
 678	struct tlbflush_unmap_batch *tlb_ubc = &current->tlb_ubc;
 679	int batch;
 680	bool writable = pte_dirty(pteval);
 681
 682	if (!pte_accessible(mm, pteval))
 683		return;
 684
 685	arch_tlbbatch_add_pending(&tlb_ubc->arch, mm, uaddr);
 686	tlb_ubc->flush_required = true;
 687
 688	/*
 689	 * Ensure compiler does not re-order the setting of tlb_flush_batched
 690	 * before the PTE is cleared.
 691	 */
 692	barrier();
 693	batch = atomic_read(&mm->tlb_flush_batched);
 694retry:
 695	if ((batch & TLB_FLUSH_BATCH_PENDING_MASK) > TLB_FLUSH_BATCH_PENDING_LARGE) {
 696		/*
 697		 * Prevent `pending' from catching up with `flushed' because of
 698		 * overflow.  Reset `pending' and `flushed' to be 1 and 0 if
 699		 * `pending' becomes large.
 700		 */
 701		if (!atomic_try_cmpxchg(&mm->tlb_flush_batched, &batch, 1))
 702			goto retry;
 703	} else {
 704		atomic_inc(&mm->tlb_flush_batched);
 705	}
 706
 707	/*
 708	 * If the PTE was dirty then it's best to assume it's writable. The
 709	 * caller must use try_to_unmap_flush_dirty() or try_to_unmap_flush()
 710	 * before the page is queued for IO.
 711	 */
 712	if (writable)
 713		tlb_ubc->writable = true;
 714}
 715
 716/*
 717 * Returns true if the TLB flush should be deferred to the end of a batch of
 718 * unmap operations to reduce IPIs.
 
 719 */
 720static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
 
 721{
 722	if (!(flags & TTU_BATCH_FLUSH))
 723		return false;
 724
 725	return arch_tlbbatch_should_defer(mm);
 726}
 727
 728/*
 729 * Reclaim unmaps pages under the PTL but do not flush the TLB prior to
 730 * releasing the PTL if TLB flushes are batched. It's possible for a parallel
 731 * operation such as mprotect or munmap to race between reclaim unmapping
 732 * the page and flushing the page. If this race occurs, it potentially allows
 733 * access to data via a stale TLB entry. Tracking all mm's that have TLB
 734 * batching in flight would be expensive during reclaim so instead track
 735 * whether TLB batching occurred in the past and if so then do a flush here
 736 * if required. This will cost one additional flush per reclaim cycle paid
 737 * by the first operation at risk such as mprotect and mumap.
 738 *
 739 * This must be called under the PTL so that an access to tlb_flush_batched
 740 * that is potentially a "reclaim vs mprotect/munmap/etc" race will synchronise
 741 * via the PTL.
 742 */
 743void flush_tlb_batched_pending(struct mm_struct *mm)
 744{
 745	int batch = atomic_read(&mm->tlb_flush_batched);
 746	int pending = batch & TLB_FLUSH_BATCH_PENDING_MASK;
 747	int flushed = batch >> TLB_FLUSH_BATCH_FLUSHED_SHIFT;
 748
 749	if (pending != flushed) {
 750		arch_flush_tlb_batched_pending(mm);
 751		/*
 752		 * If the new TLB flushing is pending during flushing, leave
 753		 * mm->tlb_flush_batched as is, to avoid losing flushing.
 754		 */
 755		atomic_cmpxchg(&mm->tlb_flush_batched, batch,
 756			       pending | (pending << TLB_FLUSH_BATCH_FLUSHED_SHIFT));
 757	}
 758}
 759#else
 760static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval,
 761				      unsigned long uaddr)
 762{
 763}
 764
 765static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
 766{
 767	return false;
 768}
 769#endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */
 770
 771/*
 772 * At what user virtual address is page expected in vma?
 773 * Caller should check the page is actually part of the vma.
 774 */
 775unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
 776{
 777	struct folio *folio = page_folio(page);
 778	if (folio_test_anon(folio)) {
 779		struct anon_vma *page__anon_vma = folio_anon_vma(folio);
 780		/*
 781		 * Note: swapoff's unuse_vma() is more efficient with this
 782		 * check, and needs it to match anon_vma when KSM is active.
 783		 */
 784		if (!vma->anon_vma || !page__anon_vma ||
 785		    vma->anon_vma->root != page__anon_vma->root)
 786			return -EFAULT;
 787	} else if (!vma->vm_file) {
 788		return -EFAULT;
 789	} else if (vma->vm_file->f_mapping != folio->mapping) {
 
 
 790		return -EFAULT;
 791	}
 792
 793	return vma_address(page, vma);
 794}
 795
 796/*
 797 * Returns the actual pmd_t* where we expect 'address' to be mapped from, or
 798 * NULL if it doesn't exist.  No guarantees / checks on what the pmd_t*
 799 * represents.
 
 
 
 
 800 */
 801pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
 
 802{
 803	pgd_t *pgd;
 804	p4d_t *p4d;
 805	pud_t *pud;
 806	pmd_t *pmd = NULL;
 
 
 
 
 
 
 
 
 807
 808	pgd = pgd_offset(mm, address);
 809	if (!pgd_present(*pgd))
 810		goto out;
 811
 812	p4d = p4d_offset(pgd, address);
 813	if (!p4d_present(*p4d))
 814		goto out;
 815
 816	pud = pud_offset(p4d, address);
 817	if (!pud_present(*pud))
 818		goto out;
 819
 820	pmd = pmd_offset(pud, address);
 821out:
 822	return pmd;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 823}
 824
 825struct folio_referenced_arg {
 826	int mapcount;
 827	int referenced;
 828	unsigned long vm_flags;
 829	struct mem_cgroup *memcg;
 830};
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 831
 832/*
 833 * arg: folio_referenced_arg will be passed
 
 834 */
 835static bool folio_referenced_one(struct folio *folio,
 836		struct vm_area_struct *vma, unsigned long address, void *arg)
 
 837{
 838	struct folio_referenced_arg *pra = arg;
 839	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
 840	int referenced = 0;
 841	unsigned long start = address, ptes = 0;
 842
 843	while (page_vma_mapped_walk(&pvmw)) {
 844		address = pvmw.address;
 
 
 
 
 
 
 
 
 
 
 
 
 845
 846		if (vma->vm_flags & VM_LOCKED) {
 847			if (!folio_test_large(folio) || !pvmw.pte) {
 848				/* Restore the mlock which got missed */
 849				mlock_vma_folio(folio, vma);
 850				page_vma_mapped_walk_done(&pvmw);
 851				pra->vm_flags |= VM_LOCKED;
 852				return false; /* To break the loop */
 853			}
 854			/*
 855			 * For large folio fully mapped to VMA, will
 856			 * be handled after the pvmw loop.
 857			 *
 858			 * For large folio cross VMA boundaries, it's
 859			 * expected to be picked  by page reclaim. But
 860			 * should skip reference of pages which are in
 861			 * the range of VM_LOCKED vma. As page reclaim
 862			 * should just count the reference of pages out
 863			 * the range of VM_LOCKED vma.
 864			 */
 865			ptes++;
 866			pra->mapcount--;
 867			continue;
 868		}
 869
 870		if (pvmw.pte) {
 871			if (lru_gen_enabled() &&
 872			    pte_young(ptep_get(pvmw.pte))) {
 873				lru_gen_look_around(&pvmw);
 874				referenced++;
 875			}
 
 
 
 
 
 
 
 
 
 876
 877			if (ptep_clear_flush_young_notify(vma, address,
 878						pvmw.pte))
 879				referenced++;
 880		} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
 881			if (pmdp_clear_flush_young_notify(vma, address,
 882						pvmw.pmd))
 883				referenced++;
 884		} else {
 885			/* unexpected pmd-mapped folio? */
 886			WARN_ON_ONCE(1);
 887		}
 888
 889		pra->mapcount--;
 890	}
 891
 892	if ((vma->vm_flags & VM_LOCKED) &&
 893			folio_test_large(folio) &&
 894			folio_within_vma(folio, vma)) {
 895		unsigned long s_align, e_align;
 896
 897		s_align = ALIGN_DOWN(start, PMD_SIZE);
 898		e_align = ALIGN_DOWN(start + folio_size(folio) - 1, PMD_SIZE);
 899
 900		/* folio doesn't cross page table boundary and fully mapped */
 901		if ((s_align == e_align) && (ptes == folio_nr_pages(folio))) {
 902			/* Restore the mlock which got missed */
 903			mlock_vma_folio(folio, vma);
 904			pra->vm_flags |= VM_LOCKED;
 905			return false; /* To break the loop */
 906		}
 
 907	}
 908
 909	if (referenced)
 910		folio_clear_idle(folio);
 911	if (folio_test_clear_young(folio))
 
 912		referenced++;
 913
 914	if (referenced) {
 915		pra->referenced++;
 916		pra->vm_flags |= vma->vm_flags & ~VM_LOCKED;
 917	}
 918
 919	if (!pra->mapcount)
 920		return false; /* To break the loop */
 921
 922	return true;
 923}
 924
 925static bool invalid_folio_referenced_vma(struct vm_area_struct *vma, void *arg)
 
 
 926{
 927	struct folio_referenced_arg *pra = arg;
 928	struct mem_cgroup *memcg = pra->memcg;
 
 
 929
 930	/*
 931	 * Ignore references from this mapping if it has no recency. If the
 932	 * folio has been used in another mapping, we will catch it; if this
 933	 * other mapping is already gone, the unmap path will have set the
 934	 * referenced flag or activated the folio in zap_pte_range().
 935	 */
 936	if (!vma_has_recency(vma))
 937		return true;
 938
 939	/*
 940	 * If we are reclaiming on behalf of a cgroup, skip counting on behalf
 941	 * of references from different cgroups.
 942	 */
 943	if (memcg && !mm_match_cgroup(vma->vm_mm, memcg))
 944		return true;
 
 
 
 
 
 
 
 
 
 
 
 
 945
 946	return false;
 
 947}
 948
 949/**
 950 * folio_referenced() - Test if the folio was referenced.
 951 * @folio: The folio to test.
 952 * @is_locked: Caller holds lock on the folio.
 953 * @memcg: target memory cgroup
 954 * @vm_flags: A combination of all the vma->vm_flags which referenced the folio.
 955 *
 956 * Quick test_and_clear_referenced for all mappings of a folio,
 957 *
 958 * Return: The number of mappings which referenced the folio. Return -1 if
 959 * the function bailed out due to rmap lock contention.
 960 */
 961int folio_referenced(struct folio *folio, int is_locked,
 962		     struct mem_cgroup *memcg, unsigned long *vm_flags)
 963{
 964	int we_locked = 0;
 965	struct folio_referenced_arg pra = {
 966		.mapcount = folio_mapcount(folio),
 967		.memcg = memcg,
 968	};
 969	struct rmap_walk_control rwc = {
 970		.rmap_one = folio_referenced_one,
 971		.arg = (void *)&pra,
 972		.anon_lock = folio_lock_anon_vma_read,
 973		.try_lock = true,
 974		.invalid_vma = invalid_folio_referenced_vma,
 975	};
 976
 977	*vm_flags = 0;
 978	if (!pra.mapcount)
 979		return 0;
 
 
 
 980
 981	if (!folio_raw_mapping(folio))
 982		return 0;
 983
 984	if (!is_locked && (!folio_test_anon(folio) || folio_test_ksm(folio))) {
 985		we_locked = folio_trylock(folio);
 986		if (!we_locked)
 987			return 1;
 988	}
 989
 990	rmap_walk(folio, &rwc);
 991	*vm_flags = pra.vm_flags;
 992
 993	if (we_locked)
 994		folio_unlock(folio);
 995
 996	return rwc.contended ? -1 : pra.referenced;
 997}
 998
 999static int page_vma_mkclean_one(struct page_vma_mapped_walk *pvmw)
1000{
1001	int cleaned = 0;
1002	struct vm_area_struct *vma = pvmw->vma;
1003	struct mmu_notifier_range range;
1004	unsigned long address = pvmw->address;
1005
1006	/*
1007	 * We have to assume the worse case ie pmd for invalidation. Note that
1008	 * the folio can not be freed from this function.
1009	 */
1010	mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_PAGE, 0,
1011				vma->vm_mm, address, vma_address_end(pvmw));
1012	mmu_notifier_invalidate_range_start(&range);
1013
1014	while (page_vma_mapped_walk(pvmw)) {
1015		int ret = 0;
1016
1017		address = pvmw->address;
1018		if (pvmw->pte) {
1019			pte_t *pte = pvmw->pte;
1020			pte_t entry = ptep_get(pte);
1021
1022			if (!pte_dirty(entry) && !pte_write(entry))
1023				continue;
1024
1025			flush_cache_page(vma, address, pte_pfn(entry));
1026			entry = ptep_clear_flush(vma, address, pte);
1027			entry = pte_wrprotect(entry);
1028			entry = pte_mkclean(entry);
1029			set_pte_at(vma->vm_mm, address, pte, entry);
1030			ret = 1;
1031		} else {
1032#ifdef CONFIG_TRANSPARENT_HUGEPAGE
1033			pmd_t *pmd = pvmw->pmd;
1034			pmd_t entry;
1035
1036			if (!pmd_dirty(*pmd) && !pmd_write(*pmd))
1037				continue;
1038
1039			flush_cache_range(vma, address,
1040					  address + HPAGE_PMD_SIZE);
1041			entry = pmdp_invalidate(vma, address, pmd);
1042			entry = pmd_wrprotect(entry);
1043			entry = pmd_mkclean(entry);
1044			set_pmd_at(vma->vm_mm, address, pmd, entry);
1045			ret = 1;
1046#else
1047			/* unexpected pmd-mapped folio? */
1048			WARN_ON_ONCE(1);
1049#endif
1050		}
1051
1052		if (ret)
1053			cleaned++;
1054	}
1055
1056	mmu_notifier_invalidate_range_end(&range);
1057
1058	return cleaned;
1059}
1060
1061static bool page_mkclean_one(struct folio *folio, struct vm_area_struct *vma,
1062			     unsigned long address, void *arg)
 
 
 
 
 
 
 
 
 
 
 
 
1063{
1064	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, PVMW_SYNC);
1065	int *cleaned = arg;
1066
1067	*cleaned += page_vma_mkclean_one(&pvmw);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1068
1069	return true;
 
 
 
 
1070}
1071
1072static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg)
 
1073{
1074	if (vma->vm_flags & VM_SHARED)
1075		return false;
 
 
1076
1077	return true;
1078}
1079
1080int folio_mkclean(struct folio *folio)
1081{
1082	int cleaned = 0;
1083	struct address_space *mapping;
1084	struct rmap_walk_control rwc = {
1085		.arg = (void *)&cleaned,
1086		.rmap_one = page_mkclean_one,
1087		.invalid_vma = invalid_mkclean_vma,
1088	};
1089
1090	BUG_ON(!folio_test_locked(folio));
 
1091
1092	if (!folio_mapped(folio))
1093		return 0;
 
 
 
 
 
1094
1095	mapping = folio_mapping(folio);
1096	if (!mapping)
1097		return 0;
1098
1099	rmap_walk(folio, &rwc);
1100
1101	return cleaned;
1102}
1103EXPORT_SYMBOL_GPL(folio_mkclean);
1104
1105/**
1106 * pfn_mkclean_range - Cleans the PTEs (including PMDs) mapped with range of
1107 *                     [@pfn, @pfn + @nr_pages) at the specific offset (@pgoff)
1108 *                     within the @vma of shared mappings. And since clean PTEs
1109 *                     should also be readonly, write protects them too.
1110 * @pfn: start pfn.
1111 * @nr_pages: number of physically contiguous pages srarting with @pfn.
1112 * @pgoff: page offset that the @pfn mapped with.
1113 * @vma: vma that @pfn mapped within.
1114 *
1115 * Returns the number of cleaned PTEs (including PMDs).
1116 */
1117int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff,
1118		      struct vm_area_struct *vma)
1119{
1120	struct page_vma_mapped_walk pvmw = {
1121		.pfn		= pfn,
1122		.nr_pages	= nr_pages,
1123		.pgoff		= pgoff,
1124		.vma		= vma,
1125		.flags		= PVMW_SYNC,
1126	};
1127
1128	if (invalid_mkclean_vma(vma, NULL))
1129		return 0;
1130
1131	pvmw.address = vma_pgoff_address(pgoff, nr_pages, vma);
1132	VM_BUG_ON_VMA(pvmw.address == -EFAULT, vma);
1133
1134	return page_vma_mkclean_one(&pvmw);
1135}
1136
1137int folio_total_mapcount(struct folio *folio)
1138{
1139	int mapcount = folio_entire_mapcount(folio);
1140	int nr_pages;
1141	int i;
 
1142
1143	/* In the common case, avoid the loop when no pages mapped by PTE */
1144	if (folio_nr_pages_mapped(folio) == 0)
1145		return mapcount;
1146	/*
1147	 * Add all the PTE mappings of those pages mapped by PTE.
1148	 * Limit the loop to folio_nr_pages_mapped()?
1149	 * Perhaps: given all the raciness, that may be a good or a bad idea.
1150	 */
1151	nr_pages = folio_nr_pages(folio);
1152	for (i = 0; i < nr_pages; i++)
1153		mapcount += atomic_read(&folio_page(folio, i)->_mapcount);
1154
1155	/* But each of those _mapcounts was based on -1 */
1156	mapcount += nr_pages;
1157	return mapcount;
 
 
 
 
 
 
 
 
1158}
1159
1160static __always_inline unsigned int __folio_add_rmap(struct folio *folio,
1161		struct page *page, int nr_pages, enum rmap_level level,
1162		int *nr_pmdmapped)
1163{
1164	atomic_t *mapped = &folio->_nr_pages_mapped;
1165	int first, nr = 0;
1166
1167	__folio_rmap_sanity_checks(folio, page, nr_pages, level);
1168
1169	switch (level) {
1170	case RMAP_LEVEL_PTE:
1171		do {
1172			first = atomic_inc_and_test(&page->_mapcount);
1173			if (first && folio_test_large(folio)) {
1174				first = atomic_inc_return_relaxed(mapped);
1175				first = (first < ENTIRELY_MAPPED);
1176			}
1177
1178			if (first)
1179				nr++;
1180		} while (page++, --nr_pages > 0);
1181		break;
1182	case RMAP_LEVEL_PMD:
1183		first = atomic_inc_and_test(&folio->_entire_mapcount);
1184		if (first) {
1185			nr = atomic_add_return_relaxed(ENTIRELY_MAPPED, mapped);
1186			if (likely(nr < ENTIRELY_MAPPED + ENTIRELY_MAPPED)) {
1187				*nr_pmdmapped = folio_nr_pages(folio);
1188				nr = *nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
1189				/* Raced ahead of a remove and another add? */
1190				if (unlikely(nr < 0))
1191					nr = 0;
1192			} else {
1193				/* Raced ahead of a remove of ENTIRELY_MAPPED */
1194				nr = 0;
1195			}
1196		}
1197		break;
1198	}
1199	return nr;
 
1200}
 
1201
1202/**
1203 * folio_move_anon_rmap - move a folio to our anon_vma
1204 * @folio:	The folio to move to our anon_vma
1205 * @vma:	The vma the folio belongs to
 
1206 *
1207 * When a folio belongs exclusively to one process after a COW event,
1208 * that folio can be moved into the anon_vma that belongs to just that
1209 * process, so the rmap code will not search the parent or sibling processes.
 
1210 */
1211void folio_move_anon_rmap(struct folio *folio, struct vm_area_struct *vma)
 
1212{
1213	void *anon_vma = vma->anon_vma;
1214
1215	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
1216	VM_BUG_ON_VMA(!anon_vma, vma);
 
1217
1218	anon_vma += PAGE_MAPPING_ANON;
1219	/*
1220	 * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
1221	 * simultaneously, so a concurrent reader (eg folio_referenced()'s
1222	 * folio_test_anon()) will not see one without the other.
1223	 */
1224	WRITE_ONCE(folio->mapping, anon_vma);
1225}
1226
1227/**
1228 * __folio_set_anon - set up a new anonymous rmap for a folio
1229 * @folio:	The folio to set up the new anonymous rmap for.
1230 * @vma:	VM area to add the folio to.
1231 * @address:	User virtual address of the mapping
1232 * @exclusive:	Whether the folio is exclusive to the process.
1233 */
1234static void __folio_set_anon(struct folio *folio, struct vm_area_struct *vma,
1235			     unsigned long address, bool exclusive)
1236{
1237	struct anon_vma *anon_vma = vma->anon_vma;
1238
1239	BUG_ON(!anon_vma);
1240
 
 
 
1241	/*
1242	 * If the folio isn't exclusive to this vma, we must use the _oldest_
1243	 * possible anon_vma for the folio mapping!
 
1244	 */
1245	if (!exclusive)
1246		anon_vma = anon_vma->root;
1247
1248	/*
1249	 * page_idle does a lockless/optimistic rmap scan on folio->mapping.
1250	 * Make sure the compiler doesn't split the stores of anon_vma and
1251	 * the PAGE_MAPPING_ANON type identifier, otherwise the rmap code
1252	 * could mistake the mapping for a struct address_space and crash.
1253	 */
1254	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
1255	WRITE_ONCE(folio->mapping, (struct address_space *) anon_vma);
1256	folio->index = linear_page_index(vma, address);
1257}
1258
1259/**
1260 * __page_check_anon_rmap - sanity check anonymous rmap addition
1261 * @folio:	The folio containing @page.
1262 * @page:	the page to check the mapping of
1263 * @vma:	the vm area in which the mapping is added
1264 * @address:	the user virtual address mapped
1265 */
1266static void __page_check_anon_rmap(struct folio *folio, struct page *page,
1267	struct vm_area_struct *vma, unsigned long address)
1268{
 
1269	/*
1270	 * The page's anon-rmap details (mapping and index) are guaranteed to
1271	 * be set up correctly at this point.
1272	 *
1273	 * We have exclusion against folio_add_anon_rmap_*() because the caller
1274	 * always holds the page locked.
 
1275	 *
1276	 * We have exclusion against folio_add_new_anon_rmap because those pages
1277	 * are initially only visible via the pagetables, and the pte is locked
1278	 * over the call to folio_add_new_anon_rmap.
1279	 */
1280	VM_BUG_ON_FOLIO(folio_anon_vma(folio)->root != vma->anon_vma->root,
1281			folio);
1282	VM_BUG_ON_PAGE(page_to_pgoff(page) != linear_page_index(vma, address),
1283		       page);
1284}
1285
1286static __always_inline void __folio_add_anon_rmap(struct folio *folio,
1287		struct page *page, int nr_pages, struct vm_area_struct *vma,
1288		unsigned long address, rmap_t flags, enum rmap_level level)
1289{
1290	int i, nr, nr_pmdmapped = 0;
1291
1292	nr = __folio_add_rmap(folio, page, nr_pages, level, &nr_pmdmapped);
1293	if (nr_pmdmapped)
1294		__lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr_pmdmapped);
1295	if (nr)
1296		__lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr);
1297
1298	if (unlikely(!folio_test_anon(folio))) {
1299		VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio);
1300		/*
1301		 * For a PTE-mapped large folio, we only know that the single
1302		 * PTE is exclusive. Further, __folio_set_anon() might not get
1303		 * folio->index right when not given the address of the head
1304		 * page.
1305		 */
1306		VM_WARN_ON_FOLIO(folio_test_large(folio) &&
1307				 level != RMAP_LEVEL_PMD, folio);
1308		__folio_set_anon(folio, vma, address,
1309				 !!(flags & RMAP_EXCLUSIVE));
1310	} else if (likely(!folio_test_ksm(folio))) {
1311		__page_check_anon_rmap(folio, page, vma, address);
1312	}
1313
1314	if (flags & RMAP_EXCLUSIVE) {
1315		switch (level) {
1316		case RMAP_LEVEL_PTE:
1317			for (i = 0; i < nr_pages; i++)
1318				SetPageAnonExclusive(page + i);
1319			break;
1320		case RMAP_LEVEL_PMD:
1321			SetPageAnonExclusive(page);
1322			break;
1323		}
1324	}
1325	for (i = 0; i < nr_pages; i++) {
1326		struct page *cur_page = page + i;
1327
1328		/* While PTE-mapping a THP we have a PMD and a PTE mapping. */
1329		VM_WARN_ON_FOLIO((atomic_read(&cur_page->_mapcount) > 0 ||
1330				  (folio_test_large(folio) &&
1331				   folio_entire_mapcount(folio) > 1)) &&
1332				 PageAnonExclusive(cur_page), folio);
1333	}
1334
1335	/*
1336	 * For large folio, only mlock it if it's fully mapped to VMA. It's
1337	 * not easy to check whether the large folio is fully mapped to VMA
1338	 * here. Only mlock normal 4K folio and leave page reclaim to handle
1339	 * large folio.
1340	 */
1341	if (!folio_test_large(folio))
1342		mlock_vma_folio(folio, vma);
1343}
1344
1345/**
1346 * folio_add_anon_rmap_ptes - add PTE mappings to a page range of an anon folio
1347 * @folio:	The folio to add the mappings to
1348 * @page:	The first page to add
1349 * @nr_pages:	The number of pages which will be mapped
1350 * @vma:	The vm area in which the mappings are added
1351 * @address:	The user virtual address of the first page to map
1352 * @flags:	The rmap flags
1353 *
1354 * The page range of folio is defined by [first_page, first_page + nr_pages)
1355 *
1356 * The caller needs to hold the page table lock, and the page must be locked in
1357 * the anon_vma case: to serialize mapping,index checking after setting,
1358 * and to ensure that an anon folio is not being upgraded racily to a KSM folio
1359 * (but KSM folios are never downgraded).
1360 */
1361void folio_add_anon_rmap_ptes(struct folio *folio, struct page *page,
1362		int nr_pages, struct vm_area_struct *vma, unsigned long address,
1363		rmap_t flags)
1364{
1365	__folio_add_anon_rmap(folio, page, nr_pages, vma, address, flags,
1366			      RMAP_LEVEL_PTE);
1367}
1368
1369/**
1370 * folio_add_anon_rmap_pmd - add a PMD mapping to a page range of an anon folio
1371 * @folio:	The folio to add the mapping to
1372 * @page:	The first page to add
1373 * @vma:	The vm area in which the mapping is added
1374 * @address:	The user virtual address of the first page to map
1375 * @flags:	The rmap flags
1376 *
1377 * The page range of folio is defined by [first_page, first_page + HPAGE_PMD_NR)
1378 *
1379 * The caller needs to hold the page table lock, and the page must be locked in
1380 * the anon_vma case: to serialize mapping,index checking after setting.
1381 */
1382void folio_add_anon_rmap_pmd(struct folio *folio, struct page *page,
1383		struct vm_area_struct *vma, unsigned long address, rmap_t flags)
1384{
1385#ifdef CONFIG_TRANSPARENT_HUGEPAGE
1386	__folio_add_anon_rmap(folio, page, HPAGE_PMD_NR, vma, address, flags,
1387			      RMAP_LEVEL_PMD);
1388#else
1389	WARN_ON_ONCE(true);
1390#endif
 
 
 
1391}
1392
1393/**
1394 * folio_add_new_anon_rmap - Add mapping to a new anonymous folio.
1395 * @folio:	The folio to add the mapping to.
1396 * @vma:	the vm area in which the mapping is added
1397 * @address:	the user virtual address mapped
1398 *
1399 * Like folio_add_anon_rmap_*() but must only be called on *new* folios.
1400 * This means the inc-and-test can be bypassed.
1401 * The folio does not have to be locked.
1402 *
1403 * If the folio is pmd-mappable, it is accounted as a THP.  As the folio
1404 * is new, it's assumed to be mapped exclusively by a single process.
1405 */
1406void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
1407		unsigned long address)
1408{
1409	int nr = folio_nr_pages(folio);
1410
1411	VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
1412	VM_BUG_ON_VMA(address < vma->vm_start ||
1413			address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
1414	__folio_set_swapbacked(folio);
1415	__folio_set_anon(folio, vma, address, true);
1416
1417	if (likely(!folio_test_large(folio))) {
1418		/* increment count (starts at -1) */
1419		atomic_set(&folio->_mapcount, 0);
1420		SetPageAnonExclusive(&folio->page);
1421	} else if (!folio_test_pmd_mappable(folio)) {
1422		int i;
1423
1424		for (i = 0; i < nr; i++) {
1425			struct page *page = folio_page(folio, i);
1426
1427			/* increment count (starts at -1) */
1428			atomic_set(&page->_mapcount, 0);
1429			SetPageAnonExclusive(page);
1430		}
1431
1432		atomic_set(&folio->_nr_pages_mapped, nr);
1433	} else {
1434		/* increment count (starts at -1) */
1435		atomic_set(&folio->_entire_mapcount, 0);
1436		atomic_set(&folio->_nr_pages_mapped, ENTIRELY_MAPPED);
1437		SetPageAnonExclusive(&folio->page);
1438		__lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr);
1439	}
1440
1441	__lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr);
1442}
1443
1444static __always_inline void __folio_add_file_rmap(struct folio *folio,
1445		struct page *page, int nr_pages, struct vm_area_struct *vma,
1446		enum rmap_level level)
 
 
 
 
1447{
1448	int nr, nr_pmdmapped = 0;
1449
1450	VM_WARN_ON_FOLIO(folio_test_anon(folio), folio);
1451
1452	nr = __folio_add_rmap(folio, page, nr_pages, level, &nr_pmdmapped);
1453	if (nr_pmdmapped)
1454		__lruvec_stat_mod_folio(folio, folio_test_swapbacked(folio) ?
1455			NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED, nr_pmdmapped);
1456	if (nr)
1457		__lruvec_stat_mod_folio(folio, NR_FILE_MAPPED, nr);
1458
1459	/* See comments in folio_add_anon_rmap_*() */
1460	if (!folio_test_large(folio))
1461		mlock_vma_folio(folio, vma);
1462}
1463
1464/**
1465 * folio_add_file_rmap_ptes - add PTE mappings to a page range of a folio
1466 * @folio:	The folio to add the mappings to
1467 * @page:	The first page to add
1468 * @nr_pages:	The number of pages that will be mapped using PTEs
1469 * @vma:	The vm area in which the mappings are added
1470 *
1471 * The page range of the folio is defined by [page, page + nr_pages)
1472 *
1473 * The caller needs to hold the page table lock.
1474 */
1475void folio_add_file_rmap_ptes(struct folio *folio, struct page *page,
1476		int nr_pages, struct vm_area_struct *vma)
1477{
1478	__folio_add_file_rmap(folio, page, nr_pages, vma, RMAP_LEVEL_PTE);
1479}
 
1480
1481/**
1482 * folio_add_file_rmap_pmd - add a PMD mapping to a page range of a folio
1483 * @folio:	The folio to add the mapping to
1484 * @page:	The first page to add
1485 * @vma:	The vm area in which the mapping is added
1486 *
1487 * The page range of the folio is defined by [page, page + HPAGE_PMD_NR)
1488 *
1489 * The caller needs to hold the page table lock.
1490 */
1491void folio_add_file_rmap_pmd(struct folio *folio, struct page *page,
1492		struct vm_area_struct *vma)
1493{
1494#ifdef CONFIG_TRANSPARENT_HUGEPAGE
1495	__folio_add_file_rmap(folio, page, HPAGE_PMD_NR, vma, RMAP_LEVEL_PMD);
1496#else
1497	WARN_ON_ONCE(true);
1498#endif
1499}
1500
1501static __always_inline void __folio_remove_rmap(struct folio *folio,
1502		struct page *page, int nr_pages, struct vm_area_struct *vma,
1503		enum rmap_level level)
1504{
1505	atomic_t *mapped = &folio->_nr_pages_mapped;
1506	int last, nr = 0, nr_pmdmapped = 0;
1507	enum node_stat_item idx;
1508
1509	__folio_rmap_sanity_checks(folio, page, nr_pages, level);
1510
1511	switch (level) {
1512	case RMAP_LEVEL_PTE:
1513		do {
1514			last = atomic_add_negative(-1, &page->_mapcount);
1515			if (last && folio_test_large(folio)) {
1516				last = atomic_dec_return_relaxed(mapped);
1517				last = (last < ENTIRELY_MAPPED);
1518			}
1519
1520			if (last)
1521				nr++;
1522		} while (page++, --nr_pages > 0);
1523		break;
1524	case RMAP_LEVEL_PMD:
1525		last = atomic_add_negative(-1, &folio->_entire_mapcount);
1526		if (last) {
1527			nr = atomic_sub_return_relaxed(ENTIRELY_MAPPED, mapped);
1528			if (likely(nr < ENTIRELY_MAPPED)) {
1529				nr_pmdmapped = folio_nr_pages(folio);
1530				nr = nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED);
1531				/* Raced ahead of another remove and an add? */
1532				if (unlikely(nr < 0))
1533					nr = 0;
1534			} else {
1535				/* An add of ENTIRELY_MAPPED raced ahead */
1536				nr = 0;
1537			}
1538		}
1539		break;
1540	}
1541
1542	if (nr_pmdmapped) {
1543		if (folio_test_anon(folio))
1544			idx = NR_ANON_THPS;
1545		else if (folio_test_swapbacked(folio))
1546			idx = NR_SHMEM_PMDMAPPED;
1547		else
1548			idx = NR_FILE_PMDMAPPED;
1549		__lruvec_stat_mod_folio(folio, idx, -nr_pmdmapped);
 
 
 
1550	}
1551	if (nr) {
1552		idx = folio_test_anon(folio) ? NR_ANON_MAPPED : NR_FILE_MAPPED;
1553		__lruvec_stat_mod_folio(folio, idx, -nr);
1554
1555		/*
1556		 * Queue anon large folio for deferred split if at least one
1557		 * page of the folio is unmapped and at least one page
1558		 * is still mapped.
1559		 */
1560		if (folio_test_large(folio) && folio_test_anon(folio))
1561			if (level == RMAP_LEVEL_PTE || nr < nr_pmdmapped)
1562				deferred_split_folio(folio);
1563	}
1564
1565	/*
1566	 * It would be tidy to reset folio_test_anon mapping when fully
1567	 * unmapped, but that might overwrite a racing folio_add_anon_rmap_*()
1568	 * which increments mapcount after us but sets mapping before us:
1569	 * so leave the reset to free_pages_prepare, and remember that
1570	 * it's only reliable while mapped.
 
 
1571	 */
1572
1573	munlock_vma_folio(folio, vma);
1574}
1575
1576/**
1577 * folio_remove_rmap_ptes - remove PTE mappings from a page range of a folio
1578 * @folio:	The folio to remove the mappings from
1579 * @page:	The first page to remove
1580 * @nr_pages:	The number of pages that will be removed from the mapping
1581 * @vma:	The vm area from which the mappings are removed
1582 *
1583 * The page range of the folio is defined by [page, page + nr_pages)
1584 *
1585 * The caller needs to hold the page table lock.
1586 */
1587void folio_remove_rmap_ptes(struct folio *folio, struct page *page,
1588		int nr_pages, struct vm_area_struct *vma)
1589{
1590	__folio_remove_rmap(folio, page, nr_pages, vma, RMAP_LEVEL_PTE);
1591}
1592
1593/**
1594 * folio_remove_rmap_pmd - remove a PMD mapping from a page range of a folio
1595 * @folio:	The folio to remove the mapping from
1596 * @page:	The first page to remove
1597 * @vma:	The vm area from which the mapping is removed
1598 *
1599 * The page range of the folio is defined by [page, page + HPAGE_PMD_NR)
1600 *
1601 * The caller needs to hold the page table lock.
1602 */
1603void folio_remove_rmap_pmd(struct folio *folio, struct page *page,
1604		struct vm_area_struct *vma)
1605{
1606#ifdef CONFIG_TRANSPARENT_HUGEPAGE
1607	__folio_remove_rmap(folio, page, HPAGE_PMD_NR, vma, RMAP_LEVEL_PMD);
1608#else
1609	WARN_ON_ONCE(true);
1610#endif
1611}
1612
1613/*
1614 * @arg: enum ttu_flags will be passed to this argument
 
1615 */
1616static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
1617		     unsigned long address, void *arg)
1618{
1619	struct mm_struct *mm = vma->vm_mm;
1620	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
1621	pte_t pteval;
1622	struct page *subpage;
1623	bool anon_exclusive, ret = true;
1624	struct mmu_notifier_range range;
1625	enum ttu_flags flags = (enum ttu_flags)(long)arg;
1626	unsigned long pfn;
1627	unsigned long hsz = 0;
1628
1629	/*
1630	 * When racing against e.g. zap_pte_range() on another cpu,
1631	 * in between its ptep_get_and_clear_full() and folio_remove_rmap_*(),
1632	 * try_to_unmap() may return before page_mapped() has become false,
1633	 * if page table locking is skipped: use TTU_SYNC to wait for that.
1634	 */
1635	if (flags & TTU_SYNC)
1636		pvmw.flags = PVMW_SYNC;
1637
1638	if (flags & TTU_SPLIT_HUGE_PMD)
1639		split_huge_pmd_address(vma, address, false, folio);
1640
1641	/*
1642	 * For THP, we have to assume the worse case ie pmd for invalidation.
1643	 * For hugetlb, it could be much worse if we need to do pud
1644	 * invalidation in the case of pmd sharing.
1645	 *
1646	 * Note that the folio can not be freed in this function as call of
1647	 * try_to_unmap() must hold a reference on the folio.
1648	 */
1649	range.end = vma_address_end(&pvmw);
1650	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
1651				address, range.end);
1652	if (folio_test_hugetlb(folio)) {
1653		/*
1654		 * If sharing is possible, start and end will be adjusted
1655		 * accordingly.
1656		 */
1657		adjust_range_if_pmd_sharing_possible(vma, &range.start,
1658						     &range.end);
1659
1660		/* We need the huge page size for set_huge_pte_at() */
1661		hsz = huge_page_size(hstate_vma(vma));
1662	}
1663	mmu_notifier_invalidate_range_start(&range);
1664
1665	while (page_vma_mapped_walk(&pvmw)) {
1666		/* Unexpected PMD-mapped THP? */
1667		VM_BUG_ON_FOLIO(!pvmw.pte, folio);
1668
1669		/*
1670		 * If the folio is in an mlock()d vma, we must not swap it out.
1671		 */
1672		if (!(flags & TTU_IGNORE_MLOCK) &&
1673		    (vma->vm_flags & VM_LOCKED)) {
1674			/* Restore the mlock which got missed */
1675			if (!folio_test_large(folio))
1676				mlock_vma_folio(folio, vma);
1677			page_vma_mapped_walk_done(&pvmw);
1678			ret = false;
1679			break;
1680		}
 
1681
1682		pfn = pte_pfn(ptep_get(pvmw.pte));
1683		subpage = folio_page(folio, pfn - folio_pfn(folio));
1684		address = pvmw.address;
1685		anon_exclusive = folio_test_anon(folio) &&
1686				 PageAnonExclusive(subpage);
1687
1688		if (folio_test_hugetlb(folio)) {
1689			bool anon = folio_test_anon(folio);
 
1690
1691			/*
1692			 * The try_to_unmap() is only passed a hugetlb page
1693			 * in the case where the hugetlb page is poisoned.
1694			 */
1695			VM_BUG_ON_PAGE(!PageHWPoison(subpage), subpage);
1696			/*
1697			 * huge_pmd_unshare may unmap an entire PMD page.
1698			 * There is no way of knowing exactly which PMDs may
1699			 * be cached for this mm, so we must flush them all.
1700			 * start/end were already adjusted above to cover this
1701			 * range.
1702			 */
1703			flush_cache_range(vma, range.start, range.end);
1704
1705			/*
1706			 * To call huge_pmd_unshare, i_mmap_rwsem must be
1707			 * held in write mode.  Caller needs to explicitly
1708			 * do this outside rmap routines.
1709			 *
1710			 * We also must hold hugetlb vma_lock in write mode.
1711			 * Lock order dictates acquiring vma_lock BEFORE
1712			 * i_mmap_rwsem.  We can only try lock here and fail
1713			 * if unsuccessful.
1714			 */
1715			if (!anon) {
1716				VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
1717				if (!hugetlb_vma_trylock_write(vma)) {
1718					page_vma_mapped_walk_done(&pvmw);
1719					ret = false;
1720					break;
1721				}
1722				if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) {
1723					hugetlb_vma_unlock_write(vma);
1724					flush_tlb_range(vma,
1725						range.start, range.end);
1726					/*
1727					 * The ref count of the PMD page was
1728					 * dropped which is part of the way map
1729					 * counting is done for shared PMDs.
1730					 * Return 'true' here.  When there is
1731					 * no other sharing, huge_pmd_unshare
1732					 * returns false and we will unmap the
1733					 * actual page and drop map count
1734					 * to zero.
1735					 */
1736					page_vma_mapped_walk_done(&pvmw);
1737					break;
1738				}
1739				hugetlb_vma_unlock_write(vma);
1740			}
1741			pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
1742		} else {
1743			flush_cache_page(vma, address, pfn);
1744			/* Nuke the page table entry. */
1745			if (should_defer_flush(mm, flags)) {
1746				/*
1747				 * We clear the PTE but do not flush so potentially
1748				 * a remote CPU could still be writing to the folio.
1749				 * If the entry was previously clean then the
1750				 * architecture must guarantee that a clear->dirty
1751				 * transition on a cached TLB entry is written through
1752				 * and traps if the PTE is unmapped.
1753				 */
1754				pteval = ptep_get_and_clear(mm, address, pvmw.pte);
1755
1756				set_tlb_ubc_flush_pending(mm, pteval, address);
1757			} else {
1758				pteval = ptep_clear_flush(vma, address, pvmw.pte);
1759			}
1760		}
1761
1762		/*
1763		 * Now the pte is cleared. If this pte was uffd-wp armed,
1764		 * we may want to replace a none pte with a marker pte if
1765		 * it's file-backed, so we don't lose the tracking info.
1766		 */
1767		pte_install_uffd_wp_if_needed(vma, address, pvmw.pte, pteval);
1768
1769		/* Set the dirty flag on the folio now the pte is gone. */
1770		if (pte_dirty(pteval))
1771			folio_mark_dirty(folio);
1772
1773		/* Update high watermark before we lower rss */
1774		update_hiwater_rss(mm);
1775
1776		if (PageHWPoison(subpage) && (flags & TTU_HWPOISON)) {
1777			pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
1778			if (folio_test_hugetlb(folio)) {
1779				hugetlb_count_sub(folio_nr_pages(folio), mm);
1780				set_huge_pte_at(mm, address, pvmw.pte, pteval,
1781						hsz);
1782			} else {
1783				dec_mm_counter(mm, mm_counter(&folio->page));
1784				set_pte_at(mm, address, pvmw.pte, pteval);
1785			}
1786
1787		} else if (pte_unused(pteval) && !userfaultfd_armed(vma)) {
1788			/*
1789			 * The guest indicated that the page content is of no
1790			 * interest anymore. Simply discard the pte, vmscan
1791			 * will take care of the rest.
1792			 * A future reference will then fault in a new zero
1793			 * page. When userfaultfd is active, we must not drop
1794			 * this page though, as its main user (postcopy
1795			 * migration) will not expect userfaults on already
1796			 * copied pages.
1797			 */
1798			dec_mm_counter(mm, mm_counter(&folio->page));
1799		} else if (folio_test_anon(folio)) {
1800			swp_entry_t entry = page_swap_entry(subpage);
1801			pte_t swp_pte;
1802			/*
1803			 * Store the swap location in the pte.
1804			 * See handle_pte_fault() ...
1805			 */
1806			if (unlikely(folio_test_swapbacked(folio) !=
1807					folio_test_swapcache(folio))) {
1808				WARN_ON_ONCE(1);
1809				ret = false;
1810				page_vma_mapped_walk_done(&pvmw);
1811				break;
1812			}
1813
1814			/* MADV_FREE page check */
1815			if (!folio_test_swapbacked(folio)) {
1816				int ref_count, map_count;
1817
1818				/*
1819				 * Synchronize with gup_pte_range():
1820				 * - clear PTE; barrier; read refcount
1821				 * - inc refcount; barrier; read PTE
1822				 */
1823				smp_mb();
1824
1825				ref_count = folio_ref_count(folio);
1826				map_count = folio_mapcount(folio);
1827
1828				/*
1829				 * Order reads for page refcount and dirty flag
1830				 * (see comments in __remove_mapping()).
1831				 */
1832				smp_rmb();
1833
1834				/*
1835				 * The only page refs must be one from isolation
1836				 * plus the rmap(s) (dropped by discard:).
1837				 */
1838				if (ref_count == 1 + map_count &&
1839				    !folio_test_dirty(folio)) {
1840					dec_mm_counter(mm, MM_ANONPAGES);
1841					goto discard;
1842				}
1843
1844				/*
1845				 * If the folio was redirtied, it cannot be
1846				 * discarded. Remap the page to page table.
1847				 */
1848				set_pte_at(mm, address, pvmw.pte, pteval);
1849				folio_set_swapbacked(folio);
1850				ret = false;
1851				page_vma_mapped_walk_done(&pvmw);
1852				break;
1853			}
1854
1855			if (swap_duplicate(entry) < 0) {
1856				set_pte_at(mm, address, pvmw.pte, pteval);
1857				ret = false;
1858				page_vma_mapped_walk_done(&pvmw);
1859				break;
1860			}
1861			if (arch_unmap_one(mm, vma, address, pteval) < 0) {
1862				swap_free(entry);
1863				set_pte_at(mm, address, pvmw.pte, pteval);
1864				ret = false;
1865				page_vma_mapped_walk_done(&pvmw);
1866				break;
1867			}
1868
1869			/* See folio_try_share_anon_rmap(): clear PTE first. */
1870			if (anon_exclusive &&
1871			    folio_try_share_anon_rmap_pte(folio, subpage)) {
1872				swap_free(entry);
1873				set_pte_at(mm, address, pvmw.pte, pteval);
1874				ret = false;
1875				page_vma_mapped_walk_done(&pvmw);
1876				break;
1877			}
1878			if (list_empty(&mm->mmlist)) {
1879				spin_lock(&mmlist_lock);
1880				if (list_empty(&mm->mmlist))
1881					list_add(&mm->mmlist, &init_mm.mmlist);
1882				spin_unlock(&mmlist_lock);
1883			}
1884			dec_mm_counter(mm, MM_ANONPAGES);
1885			inc_mm_counter(mm, MM_SWAPENTS);
1886			swp_pte = swp_entry_to_pte(entry);
1887			if (anon_exclusive)
1888				swp_pte = pte_swp_mkexclusive(swp_pte);
1889			if (pte_soft_dirty(pteval))
1890				swp_pte = pte_swp_mksoft_dirty(swp_pte);
1891			if (pte_uffd_wp(pteval))
1892				swp_pte = pte_swp_mkuffd_wp(swp_pte);
1893			set_pte_at(mm, address, pvmw.pte, swp_pte);
1894		} else {
1895			/*
1896			 * This is a locked file-backed folio,
1897			 * so it cannot be removed from the page
1898			 * cache and replaced by a new folio before
1899			 * mmu_notifier_invalidate_range_end, so no
1900			 * concurrent thread might update its page table
1901			 * to point at a new folio while a device is
1902			 * still using this folio.
1903			 *
1904			 * See Documentation/mm/mmu_notifier.rst
1905			 */
1906			dec_mm_counter(mm, mm_counter_file(&folio->page));
 
1907		}
1908discard:
1909		if (unlikely(folio_test_hugetlb(folio)))
1910			hugetlb_remove_rmap(folio);
1911		else
1912			folio_remove_rmap_pte(folio, subpage, vma);
1913		if (vma->vm_flags & VM_LOCKED)
1914			mlock_drain_local();
1915		folio_put(folio);
1916	}
1917
1918	mmu_notifier_invalidate_range_end(&range);
 
1919
 
 
 
1920	return ret;
1921}
1922
1923static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg)
1924{
1925	return vma_is_temporary_stack(vma);
1926}
1927
1928static int folio_not_mapped(struct folio *folio)
1929{
1930	return !folio_mapped(folio);
1931}
1932
1933/**
1934 * try_to_unmap - Try to remove all page table mappings to a folio.
1935 * @folio: The folio to unmap.
1936 * @flags: action and flags
1937 *
1938 * Tries to remove all the page table entries which are mapping this
1939 * folio.  It is the caller's responsibility to check if the folio is
1940 * still mapped if needed (use TTU_SYNC to prevent accounting races).
1941 *
1942 * Context: Caller must hold the folio lock.
1943 */
1944void try_to_unmap(struct folio *folio, enum ttu_flags flags)
1945{
1946	struct rmap_walk_control rwc = {
1947		.rmap_one = try_to_unmap_one,
1948		.arg = (void *)flags,
1949		.done = folio_not_mapped,
1950		.anon_lock = folio_lock_anon_vma_read,
1951	};
1952
1953	if (flags & TTU_RMAP_LOCKED)
1954		rmap_walk_locked(folio, &rwc);
1955	else
1956		rmap_walk(folio, &rwc);
1957}
1958
1959/*
1960 * @arg: enum ttu_flags will be passed to this argument.
1961 *
1962 * If TTU_SPLIT_HUGE_PMD is specified any PMD mappings will be split into PTEs
1963 * containing migration entries.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1964 */
1965static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
1966		     unsigned long address, void *arg)
 
 
 
1967{
1968	struct mm_struct *mm = vma->vm_mm;
1969	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
 
 
 
1970	pte_t pteval;
1971	struct page *subpage;
1972	bool anon_exclusive, ret = true;
1973	struct mmu_notifier_range range;
1974	enum ttu_flags flags = (enum ttu_flags)(long)arg;
1975	unsigned long pfn;
1976	unsigned long hsz = 0;
 
 
 
 
 
 
 
1977
1978	/*
1979	 * When racing against e.g. zap_pte_range() on another cpu,
1980	 * in between its ptep_get_and_clear_full() and folio_remove_rmap_*(),
1981	 * try_to_migrate() may return before page_mapped() has become false,
1982	 * if page table locking is skipped: use TTU_SYNC to wait for that.
1983	 */
1984	if (flags & TTU_SYNC)
1985		pvmw.flags = PVMW_SYNC;
1986
1987	/*
1988	 * unmap_page() in mm/huge_memory.c is the only user of migration with
1989	 * TTU_SPLIT_HUGE_PMD and it wants to freeze.
1990	 */
1991	if (flags & TTU_SPLIT_HUGE_PMD)
1992		split_huge_pmd_address(vma, address, true, folio);
1993
1994	/*
1995	 * For THP, we have to assume the worse case ie pmd for invalidation.
1996	 * For hugetlb, it could be much worse if we need to do pud
1997	 * invalidation in the case of pmd sharing.
1998	 *
1999	 * Note that the page can not be free in this function as call of
2000	 * try_to_unmap() must hold a reference on the page.
2001	 */
2002	range.end = vma_address_end(&pvmw);
2003	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
2004				address, range.end);
2005	if (folio_test_hugetlb(folio)) {
2006		/*
2007		 * If sharing is possible, start and end will be adjusted
2008		 * accordingly.
2009		 */
2010		adjust_range_if_pmd_sharing_possible(vma, &range.start,
2011						     &range.end);
2012
2013		/* We need the huge page size for set_huge_pte_at() */
2014		hsz = huge_page_size(hstate_vma(vma));
2015	}
2016	mmu_notifier_invalidate_range_start(&range);
2017
2018	while (page_vma_mapped_walk(&pvmw)) {
2019#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
2020		/* PMD-mapped THP migration entry */
2021		if (!pvmw.pte) {
2022			subpage = folio_page(folio,
2023				pmd_pfn(*pvmw.pmd) - folio_pfn(folio));
2024			VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) ||
2025					!folio_test_pmd_mappable(folio), folio);
2026
2027			if (set_pmd_migration_entry(&pvmw, subpage)) {
2028				ret = false;
2029				page_vma_mapped_walk_done(&pvmw);
2030				break;
2031			}
2032			continue;
2033		}
2034#endif
2035
2036		/* Unexpected PMD-mapped THP? */
2037		VM_BUG_ON_FOLIO(!pvmw.pte, folio);
2038
2039		pfn = pte_pfn(ptep_get(pvmw.pte));
 
 
 
 
2040
2041		if (folio_is_zone_device(folio)) {
2042			/*
2043			 * Our PTE is a non-present device exclusive entry and
2044			 * calculating the subpage as for the common case would
2045			 * result in an invalid pointer.
2046			 *
2047			 * Since only PAGE_SIZE pages can currently be
2048			 * migrated, just set it to page. This will need to be
2049			 * changed when hugepage migrations to device private
2050			 * memory are supported.
2051			 */
2052			VM_BUG_ON_FOLIO(folio_nr_pages(folio) > 1, folio);
2053			subpage = &folio->page;
2054		} else {
2055			subpage = folio_page(folio, pfn - folio_pfn(folio));
2056		}
2057		address = pvmw.address;
2058		anon_exclusive = folio_test_anon(folio) &&
2059				 PageAnonExclusive(subpage);
2060
2061		if (folio_test_hugetlb(folio)) {
2062			bool anon = folio_test_anon(folio);
2063
2064			/*
2065			 * huge_pmd_unshare may unmap an entire PMD page.
2066			 * There is no way of knowing exactly which PMDs may
2067			 * be cached for this mm, so we must flush them all.
2068			 * start/end were already adjusted above to cover this
2069			 * range.
2070			 */
2071			flush_cache_range(vma, range.start, range.end);
2072
2073			/*
2074			 * To call huge_pmd_unshare, i_mmap_rwsem must be
2075			 * held in write mode.  Caller needs to explicitly
2076			 * do this outside rmap routines.
2077			 *
2078			 * We also must hold hugetlb vma_lock in write mode.
2079			 * Lock order dictates acquiring vma_lock BEFORE
2080			 * i_mmap_rwsem.  We can only try lock here and
2081			 * fail if unsuccessful.
2082			 */
2083			if (!anon) {
2084				VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
2085				if (!hugetlb_vma_trylock_write(vma)) {
2086					page_vma_mapped_walk_done(&pvmw);
2087					ret = false;
2088					break;
2089				}
2090				if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) {
2091					hugetlb_vma_unlock_write(vma);
2092					flush_tlb_range(vma,
2093						range.start, range.end);
2094
2095					/*
2096					 * The ref count of the PMD page was
2097					 * dropped which is part of the way map
2098					 * counting is done for shared PMDs.
2099					 * Return 'true' here.  When there is
2100					 * no other sharing, huge_pmd_unshare
2101					 * returns false and we will unmap the
2102					 * actual page and drop map count
2103					 * to zero.
2104					 */
2105					page_vma_mapped_walk_done(&pvmw);
2106					break;
2107				}
2108				hugetlb_vma_unlock_write(vma);
2109			}
2110			/* Nuke the hugetlb page table entry */
2111			pteval = huge_ptep_clear_flush(vma, address, pvmw.pte);
2112		} else {
2113			flush_cache_page(vma, address, pfn);
2114			/* Nuke the page table entry. */
2115			if (should_defer_flush(mm, flags)) {
2116				/*
2117				 * We clear the PTE but do not flush so potentially
2118				 * a remote CPU could still be writing to the folio.
2119				 * If the entry was previously clean then the
2120				 * architecture must guarantee that a clear->dirty
2121				 * transition on a cached TLB entry is written through
2122				 * and traps if the PTE is unmapped.
2123				 */
2124				pteval = ptep_get_and_clear(mm, address, pvmw.pte);
2125
2126				set_tlb_ubc_flush_pending(mm, pteval, address);
2127			} else {
2128				pteval = ptep_clear_flush(vma, address, pvmw.pte);
2129			}
2130		}
2131
2132		/* Set the dirty flag on the folio now the pte is gone. */
2133		if (pte_dirty(pteval))
2134			folio_mark_dirty(folio);
2135
2136		/* Update high watermark before we lower rss */
2137		update_hiwater_rss(mm);
 
 
 
 
 
 
 
 
2138
2139		if (folio_is_device_private(folio)) {
2140			unsigned long pfn = folio_pfn(folio);
2141			swp_entry_t entry;
2142			pte_t swp_pte;
2143
2144			if (anon_exclusive)
2145				WARN_ON_ONCE(folio_try_share_anon_rmap_pte(folio,
2146									   subpage));
2147
2148			/*
2149			 * Store the pfn of the page in a special migration
2150			 * pte. do_swap_page() will wait until the migration
2151			 * pte is removed and then restart fault handling.
2152			 */
2153			entry = pte_to_swp_entry(pteval);
2154			if (is_writable_device_private_entry(entry))
2155				entry = make_writable_migration_entry(pfn);
2156			else if (anon_exclusive)
2157				entry = make_readable_exclusive_migration_entry(pfn);
2158			else
2159				entry = make_readable_migration_entry(pfn);
2160			swp_pte = swp_entry_to_pte(entry);
2161
2162			/*
2163			 * pteval maps a zone device page and is therefore
2164			 * a swap pte.
2165			 */
2166			if (pte_swp_soft_dirty(pteval))
2167				swp_pte = pte_swp_mksoft_dirty(swp_pte);
2168			if (pte_swp_uffd_wp(pteval))
2169				swp_pte = pte_swp_mkuffd_wp(swp_pte);
2170			set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte);
2171			trace_set_migration_pte(pvmw.address, pte_val(swp_pte),
2172						compound_order(&folio->page));
2173			/*
2174			 * No need to invalidate here it will synchronize on
2175			 * against the special swap migration pte.
2176			 */
2177		} else if (PageHWPoison(subpage)) {
2178			pteval = swp_entry_to_pte(make_hwpoison_entry(subpage));
2179			if (folio_test_hugetlb(folio)) {
2180				hugetlb_count_sub(folio_nr_pages(folio), mm);
2181				set_huge_pte_at(mm, address, pvmw.pte, pteval,
2182						hsz);
2183			} else {
2184				dec_mm_counter(mm, mm_counter(&folio->page));
2185				set_pte_at(mm, address, pvmw.pte, pteval);
2186			}
2187
2188		} else if (pte_unused(pteval) && !userfaultfd_armed(vma)) {
2189			/*
2190			 * The guest indicated that the page content is of no
2191			 * interest anymore. Simply discard the pte, vmscan
2192			 * will take care of the rest.
2193			 * A future reference will then fault in a new zero
2194			 * page. When userfaultfd is active, we must not drop
2195			 * this page though, as its main user (postcopy
2196			 * migration) will not expect userfaults on already
2197			 * copied pages.
2198			 */
2199			dec_mm_counter(mm, mm_counter(&folio->page));
2200		} else {
2201			swp_entry_t entry;
2202			pte_t swp_pte;
2203
2204			if (arch_unmap_one(mm, vma, address, pteval) < 0) {
2205				if (folio_test_hugetlb(folio))
2206					set_huge_pte_at(mm, address, pvmw.pte,
2207							pteval, hsz);
2208				else
2209					set_pte_at(mm, address, pvmw.pte, pteval);
2210				ret = false;
2211				page_vma_mapped_walk_done(&pvmw);
2212				break;
2213			}
2214			VM_BUG_ON_PAGE(pte_write(pteval) && folio_test_anon(folio) &&
2215				       !anon_exclusive, subpage);
2216
2217			/* See folio_try_share_anon_rmap_pte(): clear PTE first. */
2218			if (folio_test_hugetlb(folio)) {
2219				if (anon_exclusive &&
2220				    hugetlb_try_share_anon_rmap(folio)) {
2221					set_huge_pte_at(mm, address, pvmw.pte,
2222							pteval, hsz);
2223					ret = false;
2224					page_vma_mapped_walk_done(&pvmw);
2225					break;
2226				}
2227			} else if (anon_exclusive &&
2228				   folio_try_share_anon_rmap_pte(folio, subpage)) {
2229				set_pte_at(mm, address, pvmw.pte, pteval);
2230				ret = false;
2231				page_vma_mapped_walk_done(&pvmw);
2232				break;
2233			}
2234
2235			/*
2236			 * Store the pfn of the page in a special migration
2237			 * pte. do_swap_page() will wait until the migration
2238			 * pte is removed and then restart fault handling.
2239			 */
2240			if (pte_write(pteval))
2241				entry = make_writable_migration_entry(
2242							page_to_pfn(subpage));
2243			else if (anon_exclusive)
2244				entry = make_readable_exclusive_migration_entry(
2245							page_to_pfn(subpage));
2246			else
2247				entry = make_readable_migration_entry(
2248							page_to_pfn(subpage));
2249			if (pte_young(pteval))
2250				entry = make_migration_entry_young(entry);
2251			if (pte_dirty(pteval))
2252				entry = make_migration_entry_dirty(entry);
2253			swp_pte = swp_entry_to_pte(entry);
2254			if (pte_soft_dirty(pteval))
2255				swp_pte = pte_swp_mksoft_dirty(swp_pte);
2256			if (pte_uffd_wp(pteval))
2257				swp_pte = pte_swp_mkuffd_wp(swp_pte);
2258			if (folio_test_hugetlb(folio))
2259				set_huge_pte_at(mm, address, pvmw.pte, swp_pte,
2260						hsz);
2261			else
2262				set_pte_at(mm, address, pvmw.pte, swp_pte);
2263			trace_set_migration_pte(address, pte_val(swp_pte),
2264						compound_order(&folio->page));
2265			/*
2266			 * No need to invalidate here it will synchronize on
2267			 * against the special swap migration pte.
2268			 */
2269		}
2270
2271		if (unlikely(folio_test_hugetlb(folio)))
2272			hugetlb_remove_rmap(folio);
2273		else
2274			folio_remove_rmap_pte(folio, subpage, vma);
2275		if (vma->vm_flags & VM_LOCKED)
2276			mlock_drain_local();
2277		folio_put(folio);
2278	}
2279
2280	mmu_notifier_invalidate_range_end(&range);
2281
2282	return ret;
2283}
2284
2285/**
2286 * try_to_migrate - try to replace all page table mappings with swap entries
2287 * @folio: the folio to replace page table entries for
2288 * @flags: action and flags
2289 *
2290 * Tries to remove all the page table entries which are mapping this folio and
2291 * replace them with special swap entries. Caller must hold the folio lock.
 
 
 
 
 
 
 
2292 */
2293void try_to_migrate(struct folio *folio, enum ttu_flags flags)
2294{
2295	struct rmap_walk_control rwc = {
2296		.rmap_one = try_to_migrate_one,
2297		.arg = (void *)flags,
2298		.done = folio_not_mapped,
2299		.anon_lock = folio_lock_anon_vma_read,
2300	};
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2301
2302	/*
2303	 * Migration always ignores mlock and only supports TTU_RMAP_LOCKED and
2304	 * TTU_SPLIT_HUGE_PMD, TTU_SYNC, and TTU_BATCH_FLUSH flags.
 
2305	 */
2306	if (WARN_ON_ONCE(flags & ~(TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD |
2307					TTU_SYNC | TTU_BATCH_FLUSH)))
2308		return;
 
 
 
 
 
 
 
 
 
2309
2310	if (folio_is_zone_device(folio) &&
2311	    (!folio_is_device_private(folio) && !folio_is_device_coherent(folio)))
2312		return;
 
2313
2314	/*
2315	 * During exec, a temporary VMA is setup and later moved.
2316	 * The VMA is moved under the anon_vma lock but not the
2317	 * page tables leading to a race where migration cannot
2318	 * find the migration ptes. Rather than increasing the
2319	 * locking requirements of exec(), migration skips
2320	 * temporary VMAs until after exec() completes.
2321	 */
2322	if (!folio_test_ksm(folio) && folio_test_anon(folio))
2323		rwc.invalid_vma = invalid_migration_vma;
 
 
2324
2325	if (flags & TTU_RMAP_LOCKED)
2326		rmap_walk_locked(folio, &rwc);
2327	else
2328		rmap_walk(folio, &rwc);
2329}
2330
2331#ifdef CONFIG_DEVICE_PRIVATE
2332struct make_exclusive_args {
2333	struct mm_struct *mm;
2334	unsigned long address;
2335	void *owner;
2336	bool valid;
2337};
2338
2339static bool page_make_device_exclusive_one(struct folio *folio,
2340		struct vm_area_struct *vma, unsigned long address, void *priv)
2341{
2342	struct mm_struct *mm = vma->vm_mm;
2343	DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0);
2344	struct make_exclusive_args *args = priv;
2345	pte_t pteval;
2346	struct page *subpage;
2347	bool ret = true;
2348	struct mmu_notifier_range range;
2349	swp_entry_t entry;
2350	pte_t swp_pte;
2351	pte_t ptent;
2352
2353	mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0,
2354				      vma->vm_mm, address, min(vma->vm_end,
2355				      address + folio_size(folio)),
2356				      args->owner);
2357	mmu_notifier_invalidate_range_start(&range);
2358
2359	while (page_vma_mapped_walk(&pvmw)) {
2360		/* Unexpected PMD-mapped THP? */
2361		VM_BUG_ON_FOLIO(!pvmw.pte, folio);
2362
2363		ptent = ptep_get(pvmw.pte);
2364		if (!pte_present(ptent)) {
2365			ret = false;
2366			page_vma_mapped_walk_done(&pvmw);
2367			break;
2368		}
 
 
 
2369
2370		subpage = folio_page(folio,
2371				pte_pfn(ptent) - folio_pfn(folio));
2372		address = pvmw.address;
2373
2374		/* Nuke the page table entry. */
2375		flush_cache_page(vma, address, pte_pfn(ptent));
2376		pteval = ptep_clear_flush(vma, address, pvmw.pte);
2377
2378		/* Set the dirty flag on the folio now the pte is gone. */
2379		if (pte_dirty(pteval))
2380			folio_mark_dirty(folio);
2381
2382		/*
2383		 * Check that our target page is still mapped at the expected
2384		 * address.
2385		 */
2386		if (args->mm == mm && args->address == address &&
2387		    pte_write(pteval))
2388			args->valid = true;
2389
2390		/*
2391		 * Store the pfn of the page in a special migration
2392		 * pte. do_swap_page() will wait until the migration
2393		 * pte is removed and then restart fault handling.
2394		 */
2395		if (pte_write(pteval))
2396			entry = make_writable_device_exclusive_entry(
2397							page_to_pfn(subpage));
2398		else
2399			entry = make_readable_device_exclusive_entry(
2400							page_to_pfn(subpage));
2401		swp_pte = swp_entry_to_pte(entry);
2402		if (pte_soft_dirty(pteval))
2403			swp_pte = pte_swp_mksoft_dirty(swp_pte);
2404		if (pte_uffd_wp(pteval))
2405			swp_pte = pte_swp_mkuffd_wp(swp_pte);
2406
2407		set_pte_at(mm, address, pvmw.pte, swp_pte);
2408
2409		/*
2410		 * There is a reference on the page for the swap entry which has
2411		 * been removed, so shouldn't take another.
2412		 */
2413		folio_remove_rmap_pte(folio, subpage, vma);
2414	}
2415
2416	mmu_notifier_invalidate_range_end(&range);
2417
2418	return ret;
2419}
2420
2421/**
2422 * folio_make_device_exclusive - Mark the folio exclusively owned by a device.
2423 * @folio: The folio to replace page table entries for.
2424 * @mm: The mm_struct where the folio is expected to be mapped.
2425 * @address: Address where the folio is expected to be mapped.
2426 * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier callbacks
2427 *
2428 * Tries to remove all the page table entries which are mapping this
2429 * folio and replace them with special device exclusive swap entries to
2430 * grant a device exclusive access to the folio.
2431 *
2432 * Context: Caller must hold the folio lock.
2433 * Return: false if the page is still mapped, or if it could not be unmapped
2434 * from the expected address. Otherwise returns true (success).
2435 */
2436static bool folio_make_device_exclusive(struct folio *folio,
2437		struct mm_struct *mm, unsigned long address, void *owner)
2438{
2439	struct make_exclusive_args args = {
2440		.mm = mm,
2441		.address = address,
2442		.owner = owner,
2443		.valid = false,
2444	};
2445	struct rmap_walk_control rwc = {
2446		.rmap_one = page_make_device_exclusive_one,
2447		.done = folio_not_mapped,
2448		.anon_lock = folio_lock_anon_vma_read,
2449		.arg = &args,
2450	};
2451
2452	/*
2453	 * Restrict to anonymous folios for now to avoid potential writeback
2454	 * issues.
2455	 */
2456	if (!folio_test_anon(folio))
2457		return false;
2458
2459	rmap_walk(folio, &rwc);
 
2460
2461	return args.valid && !folio_mapcount(folio);
 
 
 
 
 
 
 
 
2462}
2463
2464/**
2465 * make_device_exclusive_range() - Mark a range for exclusive use by a device
2466 * @mm: mm_struct of associated target process
2467 * @start: start of the region to mark for exclusive device access
2468 * @end: end address of region
2469 * @pages: returns the pages which were successfully marked for exclusive access
2470 * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier to allow filtering
2471 *
2472 * Returns: number of pages found in the range by GUP. A page is marked for
2473 * exclusive access only if the page pointer is non-NULL.
2474 *
2475 * This function finds ptes mapping page(s) to the given address range, locks
2476 * them and replaces mappings with special swap entries preventing userspace CPU
2477 * access. On fault these entries are replaced with the original mapping after
2478 * calling MMU notifiers.
2479 *
2480 * A driver using this to program access from a device must use a mmu notifier
2481 * critical section to hold a device specific lock during programming. Once
2482 * programming is complete it should drop the page lock and reference after
2483 * which point CPU access to the page will revoke the exclusive access.
2484 */
2485int make_device_exclusive_range(struct mm_struct *mm, unsigned long start,
2486				unsigned long end, struct page **pages,
2487				void *owner)
2488{
2489	long npages = (end - start) >> PAGE_SHIFT;
2490	long i;
2491
2492	npages = get_user_pages_remote(mm, start, npages,
2493				       FOLL_GET | FOLL_WRITE | FOLL_SPLIT_PMD,
2494				       pages, NULL);
2495	if (npages < 0)
2496		return npages;
2497
2498	for (i = 0; i < npages; i++, start += PAGE_SIZE) {
2499		struct folio *folio = page_folio(pages[i]);
2500		if (PageTail(pages[i]) || !folio_trylock(folio)) {
2501			folio_put(folio);
2502			pages[i] = NULL;
2503			continue;
2504		}
2505
2506		if (!folio_make_device_exclusive(folio, mm, start, owner)) {
2507			folio_unlock(folio);
2508			folio_put(folio);
2509			pages[i] = NULL;
2510		}
2511	}
2512
2513	return npages;
2514}
2515EXPORT_SYMBOL_GPL(make_device_exclusive_range);
2516#endif
2517
2518void __put_anon_vma(struct anon_vma *anon_vma)
2519{
2520	struct anon_vma *root = anon_vma->root;
2521
2522	anon_vma_free(anon_vma);
2523	if (root != anon_vma && atomic_dec_and_test(&root->refcount))
2524		anon_vma_free(root);
 
 
2525}
2526
2527static struct anon_vma *rmap_walk_anon_lock(struct folio *folio,
2528					    struct rmap_walk_control *rwc)
 
 
 
 
 
2529{
2530	struct anon_vma *anon_vma;
2531
2532	if (rwc->anon_lock)
2533		return rwc->anon_lock(folio, rwc);
2534
2535	/*
2536	 * Note: remove_migration_ptes() cannot use folio_lock_anon_vma_read()
2537	 * because that depends on page_mapped(); but not all its usages
2538	 * are holding mmap_lock. Users without mmap_lock are required to
2539	 * take a reference count to prevent the anon_vma disappearing
2540	 */
2541	anon_vma = folio_anon_vma(folio);
2542	if (!anon_vma)
2543		return NULL;
2544
2545	if (anon_vma_trylock_read(anon_vma))
2546		goto out;
2547
2548	if (rwc->try_lock) {
2549		anon_vma = NULL;
2550		rwc->contended = true;
2551		goto out;
2552	}
2553
2554	anon_vma_lock_read(anon_vma);
2555out:
2556	return anon_vma;
2557}
2558
2559/*
2560 * rmap_walk_anon - do something to anonymous page using the object-based
2561 * rmap method
2562 * @folio: the folio to be handled
2563 * @rwc: control variable according to each walk type
2564 * @locked: caller holds relevant rmap lock
2565 *
2566 * Find all the mappings of a folio using the mapping pointer and the vma
2567 * chains contained in the anon_vma struct it points to.
2568 */
2569static void rmap_walk_anon(struct folio *folio,
2570		struct rmap_walk_control *rwc, bool locked)
2571{
2572	struct anon_vma *anon_vma;
2573	pgoff_t pgoff_start, pgoff_end;
2574	struct anon_vma_chain *avc;
2575
2576	if (locked) {
2577		anon_vma = folio_anon_vma(folio);
2578		/* anon_vma disappear under us? */
2579		VM_BUG_ON_FOLIO(!anon_vma, folio);
2580	} else {
2581		anon_vma = rmap_walk_anon_lock(folio, rwc);
2582	}
2583	if (!anon_vma)
2584		return;
2585
2586	pgoff_start = folio_pgoff(folio);
2587	pgoff_end = pgoff_start + folio_nr_pages(folio) - 1;
2588	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
2589			pgoff_start, pgoff_end) {
2590		struct vm_area_struct *vma = avc->vma;
2591		unsigned long address = vma_address(&folio->page, vma);
2592
2593		VM_BUG_ON_VMA(address == -EFAULT, vma);
2594		cond_resched();
2595
2596		if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
2597			continue;
2598
2599		if (!rwc->rmap_one(folio, vma, address, rwc->arg))
2600			break;
2601		if (rwc->done && rwc->done(folio))
2602			break;
2603	}
2604
2605	if (!locked)
2606		anon_vma_unlock_read(anon_vma);
2607}
2608
2609/*
2610 * rmap_walk_file - do something to file page using the object-based rmap method
2611 * @folio: the folio to be handled
2612 * @rwc: control variable according to each walk type
2613 * @locked: caller holds relevant rmap lock
2614 *
2615 * Find all the mappings of a folio using the mapping pointer and the vma chains
2616 * contained in the address_space struct it points to.
2617 */
2618static void rmap_walk_file(struct folio *folio,
2619		struct rmap_walk_control *rwc, bool locked)
2620{
2621	struct address_space *mapping = folio_mapping(folio);
2622	pgoff_t pgoff_start, pgoff_end;
2623	struct vm_area_struct *vma;
2624
2625	/*
2626	 * The page lock not only makes sure that page->mapping cannot
2627	 * suddenly be NULLified by truncation, it makes sure that the
2628	 * structure at mapping cannot be freed and reused yet,
2629	 * so we can safely take mapping->i_mmap_rwsem.
2630	 */
2631	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
2632
2633	if (!mapping)
2634		return;
2635
2636	pgoff_start = folio_pgoff(folio);
2637	pgoff_end = pgoff_start + folio_nr_pages(folio) - 1;
2638	if (!locked) {
2639		if (i_mmap_trylock_read(mapping))
2640			goto lookup;
2641
2642		if (rwc->try_lock) {
2643			rwc->contended = true;
2644			return;
2645		}
2646
2647		i_mmap_lock_read(mapping);
2648	}
2649lookup:
2650	vma_interval_tree_foreach(vma, &mapping->i_mmap,
2651			pgoff_start, pgoff_end) {
2652		unsigned long address = vma_address(&folio->page, vma);
2653
2654		VM_BUG_ON_VMA(address == -EFAULT, vma);
2655		cond_resched();
2656
2657		if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg))
2658			continue;
2659
2660		if (!rwc->rmap_one(folio, vma, address, rwc->arg))
2661			goto done;
2662		if (rwc->done && rwc->done(folio))
2663			goto done;
2664	}
2665
2666done:
2667	if (!locked)
2668		i_mmap_unlock_read(mapping);
 
 
 
2669}
2670
2671void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc)
 
2672{
2673	if (unlikely(folio_test_ksm(folio)))
2674		rmap_walk_ksm(folio, rwc);
2675	else if (folio_test_anon(folio))
2676		rmap_walk_anon(folio, rwc, false);
2677	else
2678		rmap_walk_file(folio, rwc, false);
2679}
2680
2681/* Like rmap_walk, but caller holds relevant rmap lock */
2682void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc)
2683{
2684	/* no ksm support for now */
2685	VM_BUG_ON_FOLIO(folio_test_ksm(folio), folio);
2686	if (folio_test_anon(folio))
2687		rmap_walk_anon(folio, rwc, true);
2688	else
2689		rmap_walk_file(folio, rwc, true);
2690}
 
2691
2692#ifdef CONFIG_HUGETLB_PAGE
2693/*
2694 * The following two functions are for anonymous (private mapped) hugepages.
2695 * Unlike common anonymous pages, anonymous hugepages have no accounting code
2696 * and no lru code, because we handle hugepages differently from common pages.
2697 */
2698void hugetlb_add_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
2699		unsigned long address, rmap_t flags)
2700{
2701	VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
2702	VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
 
2703
2704	atomic_inc(&folio->_entire_mapcount);
2705	if (flags & RMAP_EXCLUSIVE)
2706		SetPageAnonExclusive(&folio->page);
2707	VM_WARN_ON_FOLIO(folio_entire_mapcount(folio) > 1 &&
2708			 PageAnonExclusive(&folio->page), folio);
 
 
 
2709}
2710
2711void hugetlb_add_new_anon_rmap(struct folio *folio,
2712		struct vm_area_struct *vma, unsigned long address)
2713{
2714	VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio);
 
2715
 
 
 
 
 
 
 
 
 
 
 
2716	BUG_ON(address < vma->vm_start || address >= vma->vm_end);
2717	/* increment count (starts at -1) */
2718	atomic_set(&folio->_entire_mapcount, 0);
2719	folio_clear_hugetlb_restore_reserve(folio);
2720	__folio_set_anon(folio, vma, address, true);
2721	SetPageAnonExclusive(&folio->page);
2722}
2723#endif /* CONFIG_HUGETLB_PAGE */