rmap.c 21.8 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244
/*
 * mm/rmap.c - physical to virtual reverse mappings
 *
 * Copyright 2001, Rik van Riel <riel@conectiva.com.br>
 * Released under the General Public License (GPL).
 *
 * Simple, low overhead reverse mapping scheme.
 * Please try to keep this thing as modular as possible.
 *
 * Provides methods for unmapping each kind of mapped page:
 * the anon methods track anonymous pages, and
 * the file methods track pages belonging to an inode.
 *
 * Original design by Rik van Riel <riel@conectiva.com.br> 2001
 * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004
 * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004
 * Contributions by Hugh Dickins <hugh@veritas.com> 2003, 2004
 */

/*
 * Lock ordering in mm:
 *
 * inode->i_sem	(while writing or truncating, not reading or faulting)
 *   inode->i_alloc_sem
 *
 * When a page fault occurs in writing from user to file, down_read
 * of mmap_sem nests within i_sem; in sys_msync, i_sem nests within
 * down_read of mmap_sem; i_sem and down_write of mmap_sem are never
 * taken together; in truncation, i_sem is taken outermost.
 *
 * mm->mmap_sem
 *   page->flags PG_locked (lock_page)
 *     mapping->i_mmap_lock
 *       anon_vma->lock
 *         mm->page_table_lock
 *           zone->lru_lock (in mark_page_accessed)
 *           swap_list_lock (in swap_free etc's swap_info_get)
 *             mmlist_lock (in mmput, drain_mmlist and others)
 *             swap_device_lock (in swap_duplicate, swap_info_get)
 *             mapping->private_lock (in __set_page_dirty_buffers)
 *             inode_lock (in set_page_dirty's __mark_inode_dirty)
 *               sb_lock (within inode_lock in fs/fs-writeback.c)
 *               mapping->tree_lock (widely used, in set_page_dirty,
 *                         in arch-dependent flush_dcache_mmap_lock,
 *                         within inode_lock in __sync_single_inode)
 */

#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/rmap.h>
#include <linux/rcupdate.h>

#include <asm/tlbflush.h>

//#define RMAP_DEBUG /* can be enabled only for debugging */

kmem_cache_t *anon_vma_cachep;

static inline void validate_anon_vma(struct vm_area_struct *find_vma)
{
#ifdef RMAP_DEBUG
	struct anon_vma *anon_vma = find_vma->anon_vma;
	struct vm_area_struct *vma;
	unsigned int mapcount = 0;
	int found = 0;

	list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
		mapcount++;
		BUG_ON(mapcount > 100000);
		if (vma == find_vma)
			found = 1;
	}
	BUG_ON(!found);
#endif
}

/* This must be called under the mmap_sem. */
int anon_vma_prepare(struct vm_area_struct *vma)
{
	struct anon_vma *anon_vma = vma->anon_vma;

	might_sleep();
	if (unlikely(!anon_vma)) {
		struct mm_struct *mm = vma->vm_mm;
		struct anon_vma *allocated, *locked;

		anon_vma = find_mergeable_anon_vma(vma);
		if (anon_vma) {
			allocated = NULL;
			locked = anon_vma;
			spin_lock(&locked->lock);
		} else {
			anon_vma = anon_vma_alloc();
			if (unlikely(!anon_vma))
				return -ENOMEM;
			allocated = anon_vma;
			locked = NULL;
		}

		/* page_table_lock to protect against threads */
		spin_lock(&mm->page_table_lock);
		if (likely(!vma->anon_vma)) {
			vma->anon_vma = anon_vma;
			list_add(&vma->anon_vma_node, &anon_vma->head);
			allocated = NULL;
		}
		spin_unlock(&mm->page_table_lock);

		if (locked)
			spin_unlock(&locked->lock);
		if (unlikely(allocated))
			anon_vma_free(allocated);
	}
	return 0;
}

void __anon_vma_merge(struct vm_area_struct *vma, struct vm_area_struct *next)
{
	BUG_ON(vma->anon_vma != next->anon_vma);
	list_del(&next->anon_vma_node);
}

void __anon_vma_link(struct vm_area_struct *vma)
{
	struct anon_vma *anon_vma = vma->anon_vma;

	if (anon_vma) {
		list_add(&vma->anon_vma_node, &anon_vma->head);
		validate_anon_vma(vma);
	}
}

void anon_vma_link(struct vm_area_struct *vma)
{
	struct anon_vma *anon_vma = vma->anon_vma;

	if (anon_vma) {
		spin_lock(&anon_vma->lock);
		list_add(&vma->anon_vma_node, &anon_vma->head);
		validate_anon_vma(vma);
		spin_unlock(&anon_vma->lock);
	}
}

void anon_vma_unlink(struct vm_area_struct *vma)
{
	struct anon_vma *anon_vma = vma->anon_vma;
	int empty;

	if (!anon_vma)
		return;

	spin_lock(&anon_vma->lock);
	validate_anon_vma(vma);
	list_del(&vma->anon_vma_node);

	/* We must garbage collect the anon_vma if it's empty */
	empty = list_empty(&anon_vma->head);
	spin_unlock(&anon_vma->lock);

	if (empty)
		anon_vma_free(anon_vma);
}

static void anon_vma_ctor(void *data, kmem_cache_t *cachep, unsigned long flags)
{
	if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
						SLAB_CTOR_CONSTRUCTOR) {
		struct anon_vma *anon_vma = data;

		spin_lock_init(&anon_vma->lock);
		INIT_LIST_HEAD(&anon_vma->head);
	}
}

void __init anon_vma_init(void)
{
	anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
			0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor, NULL);
}

/*
 * Getting a lock on a stable anon_vma from a page off the LRU is
 * tricky: page_lock_anon_vma rely on RCU to guard against the races.
 */
static struct anon_vma *page_lock_anon_vma(struct page *page)
{
	struct anon_vma *anon_vma = NULL;
	unsigned long anon_mapping;

	rcu_read_lock();
	anon_mapping = (unsigned long) page->mapping;
	if (!(anon_mapping & PAGE_MAPPING_ANON))
		goto out;
	if (!page_mapped(page))
		goto out;

	anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
	spin_lock(&anon_vma->lock);
out:
	rcu_read_unlock();
	return anon_vma;
}

/*
 * At what user virtual address is page expected in vma?
 */
static inline unsigned long
vma_address(struct page *page, struct vm_area_struct *vma)
{
	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
	unsigned long address;

	address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
	if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
		/* page should be within any vma from prio_tree_next */
		BUG_ON(!PageAnon(page));
		return -EFAULT;
	}
	return address;
}

/*
 * At what user virtual address is page expected in vma? checking that the
 * page matches the vma: currently only used by unuse_process, on anon pages.
 */
unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
{
	if (PageAnon(page)) {
		if ((void *)vma->anon_vma !=
		    (void *)page->mapping - PAGE_MAPPING_ANON)
			return -EFAULT;
	} else if (page->mapping && !(vma->vm_flags & VM_NONLINEAR)) {
		if (vma->vm_file->f_mapping != page->mapping)
			return -EFAULT;
	} else
		return -EFAULT;
	return vma_address(page, vma);
}

N
Nikita Danilov 已提交
245 246 247 248 249
/*
 * Check that @page is mapped at @address into @mm.
 *
 * On success returns with mapped pte and locked mm->page_table_lock.
 */
250 251
pte_t *page_check_address(struct page *page, struct mm_struct *mm,
			  unsigned long address)
N
Nikita Danilov 已提交
252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280
{
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

	/*
	 * We need the page_table_lock to protect us from page faults,
	 * munmap, fork, etc...
	 */
	spin_lock(&mm->page_table_lock);
	pgd = pgd_offset(mm, address);
	if (likely(pgd_present(*pgd))) {
		pud = pud_offset(pgd, address);
		if (likely(pud_present(*pud))) {
			pmd = pmd_offset(pud, address);
			if (likely(pmd_present(*pmd))) {
				pte = pte_offset_map(pmd, address);
				if (likely(pte_present(*pte) &&
					   page_to_pfn(page) == pte_pfn(*pte)))
					return pte;
				pte_unmap(pte);
			}
		}
	}
	spin_unlock(&mm->page_table_lock);
	return ERR_PTR(-ENOENT);
}

L
Linus Torvalds 已提交
281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298
/*
 * Subfunctions of page_referenced: page_referenced_one called
 * repeatedly from either page_referenced_anon or page_referenced_file.
 */
static int page_referenced_one(struct page *page,
	struct vm_area_struct *vma, unsigned int *mapcount, int ignore_token)
{
	struct mm_struct *mm = vma->vm_mm;
	unsigned long address;
	pte_t *pte;
	int referenced = 0;

	if (!get_mm_counter(mm, rss))
		goto out;
	address = vma_address(page, vma);
	if (address == -EFAULT)
		goto out;

N
Nikita Danilov 已提交
299 300 301 302
	pte = page_check_address(page, mm, address);
	if (!IS_ERR(pte)) {
		if (ptep_clear_flush_young(vma, address, pte))
			referenced++;
L
Linus Torvalds 已提交
303

N
Nikita Danilov 已提交
304 305
		if (mm != current->mm && !ignore_token && has_swap_token(mm))
			referenced++;
L
Linus Torvalds 已提交
306

N
Nikita Danilov 已提交
307 308 309 310
		(*mapcount)--;
		pte_unmap(pte);
		spin_unlock(&mm->page_table_lock);
	}
L
Linus Torvalds 已提交
311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526
out:
	return referenced;
}

static int page_referenced_anon(struct page *page, int ignore_token)
{
	unsigned int mapcount;
	struct anon_vma *anon_vma;
	struct vm_area_struct *vma;
	int referenced = 0;

	anon_vma = page_lock_anon_vma(page);
	if (!anon_vma)
		return referenced;

	mapcount = page_mapcount(page);
	list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
		referenced += page_referenced_one(page, vma, &mapcount,
							ignore_token);
		if (!mapcount)
			break;
	}
	spin_unlock(&anon_vma->lock);
	return referenced;
}

/**
 * page_referenced_file - referenced check for object-based rmap
 * @page: the page we're checking references on.
 *
 * For an object-based mapped page, find all the places it is mapped and
 * check/clear the referenced flag.  This is done by following the page->mapping
 * pointer, then walking the chain of vmas it holds.  It returns the number
 * of references it found.
 *
 * This function is only called from page_referenced for object-based pages.
 */
static int page_referenced_file(struct page *page, int ignore_token)
{
	unsigned int mapcount;
	struct address_space *mapping = page->mapping;
	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
	struct vm_area_struct *vma;
	struct prio_tree_iter iter;
	int referenced = 0;

	/*
	 * The caller's checks on page->mapping and !PageAnon have made
	 * sure that this is a file page: the check for page->mapping
	 * excludes the case just before it gets set on an anon page.
	 */
	BUG_ON(PageAnon(page));

	/*
	 * The page lock not only makes sure that page->mapping cannot
	 * suddenly be NULLified by truncation, it makes sure that the
	 * structure at mapping cannot be freed and reused yet,
	 * so we can safely take mapping->i_mmap_lock.
	 */
	BUG_ON(!PageLocked(page));

	spin_lock(&mapping->i_mmap_lock);

	/*
	 * i_mmap_lock does not stabilize mapcount at all, but mapcount
	 * is more likely to be accurate if we note it after spinning.
	 */
	mapcount = page_mapcount(page);

	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
		if ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE))
				  == (VM_LOCKED|VM_MAYSHARE)) {
			referenced++;
			break;
		}
		referenced += page_referenced_one(page, vma, &mapcount,
							ignore_token);
		if (!mapcount)
			break;
	}

	spin_unlock(&mapping->i_mmap_lock);
	return referenced;
}

/**
 * page_referenced - test if the page was referenced
 * @page: the page to test
 * @is_locked: caller holds lock on the page
 *
 * Quick test_and_clear_referenced for all mappings to a page,
 * returns the number of ptes which referenced the page.
 */
int page_referenced(struct page *page, int is_locked, int ignore_token)
{
	int referenced = 0;

	if (!swap_token_default_timeout)
		ignore_token = 1;

	if (page_test_and_clear_young(page))
		referenced++;

	if (TestClearPageReferenced(page))
		referenced++;

	if (page_mapped(page) && page->mapping) {
		if (PageAnon(page))
			referenced += page_referenced_anon(page, ignore_token);
		else if (is_locked)
			referenced += page_referenced_file(page, ignore_token);
		else if (TestSetPageLocked(page))
			referenced++;
		else {
			if (page->mapping)
				referenced += page_referenced_file(page,
								ignore_token);
			unlock_page(page);
		}
	}
	return referenced;
}

/**
 * page_add_anon_rmap - add pte mapping to an anonymous page
 * @page:	the page to add the mapping to
 * @vma:	the vm area in which the mapping is added
 * @address:	the user virtual address mapped
 *
 * The caller needs to hold the mm->page_table_lock.
 */
void page_add_anon_rmap(struct page *page,
	struct vm_area_struct *vma, unsigned long address)
{
	struct anon_vma *anon_vma = vma->anon_vma;
	pgoff_t index;

	BUG_ON(PageReserved(page));
	BUG_ON(!anon_vma);

	inc_mm_counter(vma->vm_mm, anon_rss);

	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
	index = (address - vma->vm_start) >> PAGE_SHIFT;
	index += vma->vm_pgoff;
	index >>= PAGE_CACHE_SHIFT - PAGE_SHIFT;

	if (atomic_inc_and_test(&page->_mapcount)) {
		page->index = index;
		page->mapping = (struct address_space *) anon_vma;
		inc_page_state(nr_mapped);
	}
	/* else checking page index and mapping is racy */
}

/**
 * page_add_file_rmap - add pte mapping to a file page
 * @page: the page to add the mapping to
 *
 * The caller needs to hold the mm->page_table_lock.
 */
void page_add_file_rmap(struct page *page)
{
	BUG_ON(PageAnon(page));
	if (!pfn_valid(page_to_pfn(page)) || PageReserved(page))
		return;

	if (atomic_inc_and_test(&page->_mapcount))
		inc_page_state(nr_mapped);
}

/**
 * page_remove_rmap - take down pte mapping from a page
 * @page: page to remove mapping from
 *
 * Caller needs to hold the mm->page_table_lock.
 */
void page_remove_rmap(struct page *page)
{
	BUG_ON(PageReserved(page));

	if (atomic_add_negative(-1, &page->_mapcount)) {
		BUG_ON(page_mapcount(page) < 0);
		/*
		 * It would be tidy to reset the PageAnon mapping here,
		 * but that might overwrite a racing page_add_anon_rmap
		 * which increments mapcount after us but sets mapping
		 * before us: so leave the reset to free_hot_cold_page,
		 * and remember that it's only reliable while mapped.
		 * Leaving it set also helps swapoff to reinstate ptes
		 * faster for those pages still in swapcache.
		 */
		if (page_test_and_clear_dirty(page))
			set_page_dirty(page);
		dec_page_state(nr_mapped);
	}
}

/*
 * Subfunctions of try_to_unmap: try_to_unmap_one called
 * repeatedly from either try_to_unmap_anon or try_to_unmap_file.
 */
static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma)
{
	struct mm_struct *mm = vma->vm_mm;
	unsigned long address;
	pte_t *pte;
	pte_t pteval;
	int ret = SWAP_AGAIN;

	if (!get_mm_counter(mm, rss))
		goto out;
	address = vma_address(page, vma);
	if (address == -EFAULT)
		goto out;

N
Nikita Danilov 已提交
527 528 529
	pte = page_check_address(page, mm, address);
	if (IS_ERR(pte))
		goto out;
L
Linus Torvalds 已提交
530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567

	/*
	 * If the page is mlock()d, we cannot swap it out.
	 * If it's recently referenced (perhaps page_referenced
	 * skipped over this mm) then we should reactivate it.
	 */
	if ((vma->vm_flags & (VM_LOCKED|VM_RESERVED)) ||
			ptep_clear_flush_young(vma, address, pte)) {
		ret = SWAP_FAIL;
		goto out_unmap;
	}

	/* Nuke the page table entry. */
	flush_cache_page(vma, address, page_to_pfn(page));
	pteval = ptep_clear_flush(vma, address, pte);

	/* Move the dirty bit to the physical page now the pte is gone. */
	if (pte_dirty(pteval))
		set_page_dirty(page);

	if (PageAnon(page)) {
		swp_entry_t entry = { .val = page->private };
		/*
		 * Store the swap location in the pte.
		 * See handle_pte_fault() ...
		 */
		BUG_ON(!PageSwapCache(page));
		swap_duplicate(entry);
		if (list_empty(&mm->mmlist)) {
			spin_lock(&mmlist_lock);
			list_add(&mm->mmlist, &init_mm.mmlist);
			spin_unlock(&mmlist_lock);
		}
		set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
		BUG_ON(pte_file(*pte));
		dec_mm_counter(mm, anon_rss);
	}

568
	dec_mm_counter(mm, rss);
L
Linus Torvalds 已提交
569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607
	page_remove_rmap(page);
	page_cache_release(page);

out_unmap:
	pte_unmap(pte);
	spin_unlock(&mm->page_table_lock);
out:
	return ret;
}

/*
 * objrmap doesn't work for nonlinear VMAs because the assumption that
 * offset-into-file correlates with offset-into-virtual-addresses does not hold.
 * Consequently, given a particular page and its ->index, we cannot locate the
 * ptes which are mapping that page without an exhaustive linear search.
 *
 * So what this code does is a mini "virtual scan" of each nonlinear VMA which
 * maps the file to which the target page belongs.  The ->vm_private_data field
 * holds the current cursor into that scan.  Successive searches will circulate
 * around the vma's virtual address space.
 *
 * So as more replacement pressure is applied to the pages in a nonlinear VMA,
 * more scanning pressure is placed against them as well.   Eventually pages
 * will become fully unmapped and are eligible for eviction.
 *
 * For very sparsely populated VMAs this is a little inefficient - chances are
 * there there won't be many ptes located within the scan cluster.  In this case
 * maybe we could scan further - to the end of the pte page, perhaps.
 */
#define CLUSTER_SIZE	min(32*PAGE_SIZE, PMD_SIZE)
#define CLUSTER_MASK	(~(CLUSTER_SIZE - 1))

static void try_to_unmap_cluster(unsigned long cursor,
	unsigned int *mapcount, struct vm_area_struct *vma)
{
	struct mm_struct *mm = vma->vm_mm;
	pgd_t *pgd;
	pud_t *pud;
	pmd_t *pmd;
608
	pte_t *pte, *original_pte;
L
Linus Torvalds 已提交
609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639
	pte_t pteval;
	struct page *page;
	unsigned long address;
	unsigned long end;
	unsigned long pfn;

	/*
	 * We need the page_table_lock to protect us from page faults,
	 * munmap, fork, etc...
	 */
	spin_lock(&mm->page_table_lock);

	address = (vma->vm_start + cursor) & CLUSTER_MASK;
	end = address + CLUSTER_SIZE;
	if (address < vma->vm_start)
		address = vma->vm_start;
	if (end > vma->vm_end)
		end = vma->vm_end;

	pgd = pgd_offset(mm, address);
	if (!pgd_present(*pgd))
		goto out_unlock;

	pud = pud_offset(pgd, address);
	if (!pud_present(*pud))
		goto out_unlock;

	pmd = pmd_offset(pud, address);
	if (!pmd_present(*pmd))
		goto out_unlock;

640
	for (original_pte = pte = pte_offset_map(pmd, address);
L
Linus Torvalds 已提交
641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675
			address < end; pte++, address += PAGE_SIZE) {

		if (!pte_present(*pte))
			continue;

		pfn = pte_pfn(*pte);
		if (!pfn_valid(pfn))
			continue;

		page = pfn_to_page(pfn);
		BUG_ON(PageAnon(page));
		if (PageReserved(page))
			continue;

		if (ptep_clear_flush_young(vma, address, pte))
			continue;

		/* Nuke the page table entry. */
		flush_cache_page(vma, address, pfn);
		pteval = ptep_clear_flush(vma, address, pte);

		/* If nonlinear, store the file page offset in the pte. */
		if (page->index != linear_page_index(vma, address))
			set_pte_at(mm, address, pte, pgoff_to_pte(page->index));

		/* Move the dirty bit to the physical page now the pte is gone. */
		if (pte_dirty(pteval))
			set_page_dirty(page);

		page_remove_rmap(page);
		page_cache_release(page);
		dec_mm_counter(mm, rss);
		(*mapcount)--;
	}

676
	pte_unmap(original_pte);
L
Linus Torvalds 已提交
677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827
out_unlock:
	spin_unlock(&mm->page_table_lock);
}

static int try_to_unmap_anon(struct page *page)
{
	struct anon_vma *anon_vma;
	struct vm_area_struct *vma;
	int ret = SWAP_AGAIN;

	anon_vma = page_lock_anon_vma(page);
	if (!anon_vma)
		return ret;

	list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
		ret = try_to_unmap_one(page, vma);
		if (ret == SWAP_FAIL || !page_mapped(page))
			break;
	}
	spin_unlock(&anon_vma->lock);
	return ret;
}

/**
 * try_to_unmap_file - unmap file page using the object-based rmap method
 * @page: the page to unmap
 *
 * Find all the mappings of a page using the mapping pointer and the vma chains
 * contained in the address_space struct it points to.
 *
 * This function is only called from try_to_unmap for object-based pages.
 */
static int try_to_unmap_file(struct page *page)
{
	struct address_space *mapping = page->mapping;
	pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
	struct vm_area_struct *vma;
	struct prio_tree_iter iter;
	int ret = SWAP_AGAIN;
	unsigned long cursor;
	unsigned long max_nl_cursor = 0;
	unsigned long max_nl_size = 0;
	unsigned int mapcount;

	spin_lock(&mapping->i_mmap_lock);
	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
		ret = try_to_unmap_one(page, vma);
		if (ret == SWAP_FAIL || !page_mapped(page))
			goto out;
	}

	if (list_empty(&mapping->i_mmap_nonlinear))
		goto out;

	list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
						shared.vm_set.list) {
		if (vma->vm_flags & (VM_LOCKED|VM_RESERVED))
			continue;
		cursor = (unsigned long) vma->vm_private_data;
		if (cursor > max_nl_cursor)
			max_nl_cursor = cursor;
		cursor = vma->vm_end - vma->vm_start;
		if (cursor > max_nl_size)
			max_nl_size = cursor;
	}

	if (max_nl_size == 0) {	/* any nonlinears locked or reserved */
		ret = SWAP_FAIL;
		goto out;
	}

	/*
	 * We don't try to search for this page in the nonlinear vmas,
	 * and page_referenced wouldn't have found it anyway.  Instead
	 * just walk the nonlinear vmas trying to age and unmap some.
	 * The mapcount of the page we came in with is irrelevant,
	 * but even so use it as a guide to how hard we should try?
	 */
	mapcount = page_mapcount(page);
	if (!mapcount)
		goto out;
	cond_resched_lock(&mapping->i_mmap_lock);

	max_nl_size = (max_nl_size + CLUSTER_SIZE - 1) & CLUSTER_MASK;
	if (max_nl_cursor == 0)
		max_nl_cursor = CLUSTER_SIZE;

	do {
		list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
						shared.vm_set.list) {
			if (vma->vm_flags & (VM_LOCKED|VM_RESERVED))
				continue;
			cursor = (unsigned long) vma->vm_private_data;
			while (get_mm_counter(vma->vm_mm, rss) &&
				cursor < max_nl_cursor &&
				cursor < vma->vm_end - vma->vm_start) {
				try_to_unmap_cluster(cursor, &mapcount, vma);
				cursor += CLUSTER_SIZE;
				vma->vm_private_data = (void *) cursor;
				if ((int)mapcount <= 0)
					goto out;
			}
			vma->vm_private_data = (void *) max_nl_cursor;
		}
		cond_resched_lock(&mapping->i_mmap_lock);
		max_nl_cursor += CLUSTER_SIZE;
	} while (max_nl_cursor <= max_nl_size);

	/*
	 * Don't loop forever (perhaps all the remaining pages are
	 * in locked vmas).  Reset cursor on all unreserved nonlinear
	 * vmas, now forgetting on which ones it had fallen behind.
	 */
	list_for_each_entry(vma, &mapping->i_mmap_nonlinear,
						shared.vm_set.list) {
		if (!(vma->vm_flags & VM_RESERVED))
			vma->vm_private_data = NULL;
	}
out:
	spin_unlock(&mapping->i_mmap_lock);
	return ret;
}

/**
 * try_to_unmap - try to remove all page table mappings to a page
 * @page: the page to get unmapped
 *
 * Tries to remove all the page table entries which are mapping this
 * page, used in the pageout path.  Caller must hold the page lock.
 * Return values are:
 *
 * SWAP_SUCCESS	- we succeeded in removing all mappings
 * SWAP_AGAIN	- we missed a mapping, try again later
 * SWAP_FAIL	- the page is unswappable
 */
int try_to_unmap(struct page *page)
{
	int ret;

	BUG_ON(PageReserved(page));
	BUG_ON(!PageLocked(page));

	if (PageAnon(page))
		ret = try_to_unmap_anon(page);
	else
		ret = try_to_unmap_file(page);

	if (!page_mapped(page))
		ret = SWAP_SUCCESS;
	return ret;
}
N
Nikita Danilov 已提交
828