swapfile.c 44.3 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
/*
 *  linux/mm/swapfile.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *  Swap reorganised 29.12.95, Stephen Tweedie
 */

#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/mman.h>
#include <linux/slab.h>
#include <linux/kernel_stat.h>
#include <linux/swap.h>
#include <linux/vmalloc.h>
#include <linux/pagemap.h>
#include <linux/namei.h>
#include <linux/shm.h>
#include <linux/blkdev.h>
#include <linux/writeback.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/rmap.h>
#include <linux/security.h>
#include <linux/backing-dev.h>
I
Ingo Molnar 已提交
27
#include <linux/mutex.h>
28
#include <linux/capability.h>
L
Linus Torvalds 已提交
29
#include <linux/syscalls.h>
30
#include <linux/memcontrol.h>
L
Linus Torvalds 已提交
31 32 33 34 35

#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <linux/swapops.h>

36
DEFINE_SPINLOCK(swap_lock);
L
Linus Torvalds 已提交
37 38 39 40 41 42 43 44 45 46 47
unsigned int nr_swapfiles;
long total_swap_pages;
static int swap_overflow;

static const char Bad_file[] = "Bad swap file entry ";
static const char Unused_file[] = "Unused swap file entry ";
static const char Bad_offset[] = "Bad swap offset entry ";
static const char Unused_offset[] = "Unused swap offset entry ";

struct swap_list_t swap_list = {-1, -1};

48
static struct swap_info_struct swap_info[MAX_SWAPFILES];
L
Linus Torvalds 已提交
49

I
Ingo Molnar 已提交
50
static DEFINE_MUTEX(swapon_mutex);
L
Linus Torvalds 已提交
51 52 53

/*
 * We need this because the bdev->unplug_fn can sleep and we cannot
54
 * hold swap_lock while calling the unplug_fn. And swap_lock
I
Ingo Molnar 已提交
55
 * cannot be turned into a mutex.
L
Linus Torvalds 已提交
56 57 58 59 60 61 62 63
 */
static DECLARE_RWSEM(swap_unplug_sem);

void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
{
	swp_entry_t entry;

	down_read(&swap_unplug_sem);
H
Hugh Dickins 已提交
64
	entry.val = page_private(page);
L
Linus Torvalds 已提交
65 66 67 68 69 70 71
	if (PageSwapCache(page)) {
		struct block_device *bdev = swap_info[swp_type(entry)].bdev;
		struct backing_dev_info *bdi;

		/*
		 * If the page is removed from swapcache from under us (with a
		 * racy try_to_unuse/swapoff) we need an additional reference
H
Hugh Dickins 已提交
72 73
		 * count to avoid reading garbage from page_private(page) above.
		 * If the WARN_ON triggers during a swapoff it maybe the race
L
Linus Torvalds 已提交
74 75 76 77 78 79
		 * condition and it's harmless. However if it triggers without
		 * swapoff it signals a problem.
		 */
		WARN_ON(page_count(page) <= 1);

		bdi = bdev->bd_inode->i_mapping->backing_dev_info;
M
McMullan, Jason 已提交
80
		blk_run_backing_dev(bdi, page);
L
Linus Torvalds 已提交
81 82 83 84
	}
	up_read(&swap_unplug_sem);
}

85 86 87
#define SWAPFILE_CLUSTER	256
#define LATENCY_LIMIT		256

88
static inline unsigned long scan_swap_map(struct swap_info_struct *si)
L
Linus Torvalds 已提交
89
{
90
	unsigned long offset, last_in_cluster;
91
	int latency_ration = LATENCY_LIMIT;
92

L
Linus Torvalds 已提交
93
	/* 
94 95 96 97 98 99 100 101 102
	 * We try to cluster swap pages by allocating them sequentially
	 * in swap.  Once we've allocated SWAPFILE_CLUSTER pages this
	 * way, however, we resort to first-free allocation, starting
	 * a new cluster.  This prevents us from scattering swap pages
	 * all over the entire swap partition, so that we reduce
	 * overall disk seek times between swap pages.  -- sct
	 * But we do now try to find an empty cluster.  -Andrea
	 */

103
	si->flags += SWP_SCANNING;
104 105 106 107
	if (unlikely(!si->cluster_nr)) {
		si->cluster_nr = SWAPFILE_CLUSTER - 1;
		if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER)
			goto lowest;
108
		spin_unlock(&swap_lock);
109 110 111 112 113 114

		offset = si->lowest_bit;
		last_in_cluster = offset + SWAPFILE_CLUSTER - 1;

		/* Locate the first empty (unaligned) cluster */
		for (; last_in_cluster <= si->highest_bit; offset++) {
L
Linus Torvalds 已提交
115
			if (si->swap_map[offset])
116 117
				last_in_cluster = offset + SWAPFILE_CLUSTER;
			else if (offset == last_in_cluster) {
118
				spin_lock(&swap_lock);
A
Akinobu Mita 已提交
119
				si->cluster_next = offset-SWAPFILE_CLUSTER+1;
120
				goto cluster;
L
Linus Torvalds 已提交
121
			}
122 123 124 125
			if (unlikely(--latency_ration < 0)) {
				cond_resched();
				latency_ration = LATENCY_LIMIT;
			}
126
		}
127
		spin_lock(&swap_lock);
128
		goto lowest;
L
Linus Torvalds 已提交
129
	}
130 131 132 133 134 135

	si->cluster_nr--;
cluster:
	offset = si->cluster_next;
	if (offset > si->highest_bit)
lowest:		offset = si->lowest_bit;
136 137
checks:	if (!(si->flags & SWP_WRITEOK))
		goto no_page;
138 139 140
	if (!si->highest_bit)
		goto no_page;
	if (!si->swap_map[offset]) {
141
		if (offset == si->lowest_bit)
L
Linus Torvalds 已提交
142 143 144
			si->lowest_bit++;
		if (offset == si->highest_bit)
			si->highest_bit--;
145 146
		si->inuse_pages++;
		if (si->inuse_pages == si->pages) {
L
Linus Torvalds 已提交
147 148 149 150
			si->lowest_bit = si->max;
			si->highest_bit = 0;
		}
		si->swap_map[offset] = 1;
151
		si->cluster_next = offset + 1;
152
		si->flags -= SWP_SCANNING;
L
Linus Torvalds 已提交
153 154
		return offset;
	}
155

156
	spin_unlock(&swap_lock);
157
	while (++offset <= si->highest_bit) {
158
		if (!si->swap_map[offset]) {
159
			spin_lock(&swap_lock);
160 161
			goto checks;
		}
162 163 164 165
		if (unlikely(--latency_ration < 0)) {
			cond_resched();
			latency_ration = LATENCY_LIMIT;
		}
166
	}
167
	spin_lock(&swap_lock);
168 169 170
	goto lowest;

no_page:
171
	si->flags -= SWP_SCANNING;
L
Linus Torvalds 已提交
172 173 174 175 176
	return 0;
}

swp_entry_t get_swap_page(void)
{
177 178 179 180
	struct swap_info_struct *si;
	pgoff_t offset;
	int type, next;
	int wrapped = 0;
L
Linus Torvalds 已提交
181

182
	spin_lock(&swap_lock);
L
Linus Torvalds 已提交
183
	if (nr_swap_pages <= 0)
184 185 186 187 188 189 190 191 192 193
		goto noswap;
	nr_swap_pages--;

	for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
		si = swap_info + type;
		next = si->next;
		if (next < 0 ||
		    (!wrapped && si->prio != swap_info[next].prio)) {
			next = swap_list.head;
			wrapped++;
L
Linus Torvalds 已提交
194
		}
195 196 197 198 199 200 201 202

		if (!si->highest_bit)
			continue;
		if (!(si->flags & SWP_WRITEOK))
			continue;

		swap_list.next = next;
		offset = scan_swap_map(si);
203 204
		if (offset) {
			spin_unlock(&swap_lock);
205
			return swp_entry(type, offset);
206
		}
207
		next = swap_list.next;
L
Linus Torvalds 已提交
208
	}
209 210 211

	nr_swap_pages++;
noswap:
212
	spin_unlock(&swap_lock);
213
	return (swp_entry_t) {0};
L
Linus Torvalds 已提交
214 215
}

216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235
swp_entry_t get_swap_page_of_type(int type)
{
	struct swap_info_struct *si;
	pgoff_t offset;

	spin_lock(&swap_lock);
	si = swap_info + type;
	if (si->flags & SWP_WRITEOK) {
		nr_swap_pages--;
		offset = scan_swap_map(si);
		if (offset) {
			spin_unlock(&swap_lock);
			return swp_entry(type, offset);
		}
		nr_swap_pages++;
	}
	spin_unlock(&swap_lock);
	return (swp_entry_t) {0};
}

L
Linus Torvalds 已提交
236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253
static struct swap_info_struct * swap_info_get(swp_entry_t entry)
{
	struct swap_info_struct * p;
	unsigned long offset, type;

	if (!entry.val)
		goto out;
	type = swp_type(entry);
	if (type >= nr_swapfiles)
		goto bad_nofile;
	p = & swap_info[type];
	if (!(p->flags & SWP_USED))
		goto bad_device;
	offset = swp_offset(entry);
	if (offset >= p->max)
		goto bad_offset;
	if (!p->swap_map[offset])
		goto bad_free;
254
	spin_lock(&swap_lock);
L
Linus Torvalds 已提交
255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283
	return p;

bad_free:
	printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
	goto out;
bad_offset:
	printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
	goto out;
bad_device:
	printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
	goto out;
bad_nofile:
	printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
out:
	return NULL;
}	

static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
{
	int count = p->swap_map[offset];

	if (count < SWAP_MAP_MAX) {
		count--;
		p->swap_map[offset] = count;
		if (!count) {
			if (offset < p->lowest_bit)
				p->lowest_bit = offset;
			if (offset > p->highest_bit)
				p->highest_bit = offset;
284 285
			if (p->prio > swap_info[swap_list.next].prio)
				swap_list.next = p - swap_info;
L
Linus Torvalds 已提交
286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303
			nr_swap_pages++;
			p->inuse_pages--;
		}
	}
	return count;
}

/*
 * Caller has made sure that the swapdevice corresponding to entry
 * is still around or has not been recycled.
 */
void swap_free(swp_entry_t entry)
{
	struct swap_info_struct * p;

	p = swap_info_get(entry);
	if (p) {
		swap_entry_free(p, swp_offset(entry));
304
		spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
305 306 307 308
	}
}

/*
309
 * How many references to page are currently swapped out?
L
Linus Torvalds 已提交
310
 */
311
static inline int page_swapcount(struct page *page)
L
Linus Torvalds 已提交
312
{
313 314
	int count = 0;
	struct swap_info_struct *p;
L
Linus Torvalds 已提交
315 316
	swp_entry_t entry;

H
Hugh Dickins 已提交
317
	entry.val = page_private(page);
L
Linus Torvalds 已提交
318 319
	p = swap_info_get(entry);
	if (p) {
320 321
		/* Subtract the 1 for the swap cache itself */
		count = p->swap_map[swp_offset(entry)] - 1;
322
		spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
323
	}
324
	return count;
L
Linus Torvalds 已提交
325 326 327 328 329 330 331 332
}

/*
 * We can use this swap cache entry directly
 * if there are no other references to it.
 */
int can_share_swap_page(struct page *page)
{
333 334 335 336 337 338 339
	int count;

	BUG_ON(!PageLocked(page));
	count = page_mapcount(page);
	if (count <= 1 && PageSwapCache(page))
		count += page_swapcount(page);
	return count == 1;
L
Linus Torvalds 已提交
340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361
}

/*
 * Work out if there are any other processes sharing this
 * swap cache page. Free it if you can. Return success.
 */
int remove_exclusive_swap_page(struct page *page)
{
	int retval;
	struct swap_info_struct * p;
	swp_entry_t entry;

	BUG_ON(PagePrivate(page));
	BUG_ON(!PageLocked(page));

	if (!PageSwapCache(page))
		return 0;
	if (PageWriteback(page))
		return 0;
	if (page_count(page) != 2) /* 2: us + cache */
		return 0;

H
Hugh Dickins 已提交
362
	entry.val = page_private(page);
L
Linus Torvalds 已提交
363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378
	p = swap_info_get(entry);
	if (!p)
		return 0;

	/* Is the only swap cache user the cache itself? */
	retval = 0;
	if (p->swap_map[swp_offset(entry)] == 1) {
		/* Recheck the page count with the swapcache lock held.. */
		write_lock_irq(&swapper_space.tree_lock);
		if ((page_count(page) == 2) && !PageWriteback(page)) {
			__delete_from_swap_cache(page);
			SetPageDirty(page);
			retval = 1;
		}
		write_unlock_irq(&swapper_space.tree_lock);
	}
379
	spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397

	if (retval) {
		swap_free(entry);
		page_cache_release(page);
	}

	return retval;
}

/*
 * Free the swap entry like above, but also try to
 * free the page cache entry if it is the last user.
 */
void free_swap_and_cache(swp_entry_t entry)
{
	struct swap_info_struct * p;
	struct page *page = NULL;

398 399 400
	if (is_migration_entry(entry))
		return;

L
Linus Torvalds 已提交
401 402
	p = swap_info_get(entry);
	if (p) {
403 404 405 406 407 408 409
		if (swap_entry_free(p, swp_offset(entry)) == 1) {
			page = find_get_page(&swapper_space, entry.val);
			if (page && unlikely(TestSetPageLocked(page))) {
				page_cache_release(page);
				page = NULL;
			}
		}
410
		spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
411 412 413 414 415 416 417
	}
	if (page) {
		int one_user;

		BUG_ON(PagePrivate(page));
		one_user = (page_count(page) == 2);
		/* Only cache user (+us), or swap space full? Free it! */
418 419 420
		/* Also recheck PageSwapCache after page is locked (above) */
		if (PageSwapCache(page) && !PageWriteback(page) &&
					(one_user || vm_swap_full())) {
L
Linus Torvalds 已提交
421 422 423 424 425 426 427 428
			delete_from_swap_cache(page);
			SetPageDirty(page);
		}
		unlock_page(page);
		page_cache_release(page);
	}
}

429
#ifdef CONFIG_HIBERNATION
430
/*
431
 * Find the swap type that corresponds to given device (if any).
432
 *
433 434 435 436
 * @offset - number of the PAGE_SIZE-sized block of the device, starting
 * from 0, in which the swap header is expected to be located.
 *
 * This is needed for the suspend to disk (aka swsusp).
437
 */
438
int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
439
{
440
	struct block_device *bdev = NULL;
441 442
	int i;

443 444 445
	if (device)
		bdev = bdget(device);

446 447
	spin_lock(&swap_lock);
	for (i = 0; i < nr_swapfiles; i++) {
448
		struct swap_info_struct *sis = swap_info + i;
449

450
		if (!(sis->flags & SWP_WRITEOK))
451
			continue;
452

453
		if (!bdev) {
454 455 456
			if (bdev_p)
				*bdev_p = sis->bdev;

457 458 459
			spin_unlock(&swap_lock);
			return i;
		}
460 461 462 463 464 465
		if (bdev == sis->bdev) {
			struct swap_extent *se;

			se = list_entry(sis->extent_list.next,
					struct swap_extent, list);
			if (se->start_block == offset) {
466 467 468
				if (bdev_p)
					*bdev_p = sis->bdev;

469 470 471 472
				spin_unlock(&swap_lock);
				bdput(bdev);
				return i;
			}
473 474 475
		}
	}
	spin_unlock(&swap_lock);
476 477 478
	if (bdev)
		bdput(bdev);

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
	return -ENODEV;
}

/*
 * Return either the total number of swap pages of given type, or the number
 * of free pages of that type (depending on @free)
 *
 * This is needed for software suspend
 */
unsigned int count_swap_pages(int type, int free)
{
	unsigned int n = 0;

	if (type < nr_swapfiles) {
		spin_lock(&swap_lock);
		if (swap_info[type].flags & SWP_WRITEOK) {
			n = swap_info[type].pages;
			if (free)
				n -= swap_info[type].inuse_pages;
		}
		spin_unlock(&swap_lock);
	}
	return n;
}
#endif

L
Linus Torvalds 已提交
505
/*
506 507 508
 * No need to decide whether this PTE shares the swap entry with others,
 * just let do_wp_page work it out if a write is requested later - to
 * force COW, vm_page_prot omits write permission from any private vma.
L
Linus Torvalds 已提交
509
 */
510
static int unuse_pte(struct vm_area_struct *vma, pte_t *pte,
L
Linus Torvalds 已提交
511 512
		unsigned long addr, swp_entry_t entry, struct page *page)
{
513 514 515
	if (mem_cgroup_charge(page, vma->vm_mm))
		return -ENOMEM;

516
	inc_mm_counter(vma->vm_mm, anon_rss);
L
Linus Torvalds 已提交
517 518 519 520 521 522 523 524 525 526
	get_page(page);
	set_pte_at(vma->vm_mm, addr, pte,
		   pte_mkold(mk_pte(page, vma->vm_page_prot)));
	page_add_anon_rmap(page, vma, addr);
	swap_free(entry);
	/*
	 * Move the page to the active list so it is not
	 * immediately swapped out again after swapon.
	 */
	activate_page(page);
527
	return 1;
L
Linus Torvalds 已提交
528 529 530 531 532 533 534
}

static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
				unsigned long addr, unsigned long end,
				swp_entry_t entry, struct page *page)
{
	pte_t swp_pte = swp_entry_to_pte(entry);
535
	pte_t *pte;
536
	spinlock_t *ptl;
537
	int ret = 0;
L
Linus Torvalds 已提交
538

539
	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
L
Linus Torvalds 已提交
540 541 542 543 544 545
	do {
		/*
		 * swapoff spends a _lot_ of time in this loop!
		 * Test inline before going to call unuse_pte.
		 */
		if (unlikely(pte_same(*pte, swp_pte))) {
546
			ret = unuse_pte(vma, pte++, addr, entry, page);
547
			break;
L
Linus Torvalds 已提交
548 549
		}
	} while (pte++, addr += PAGE_SIZE, addr != end);
550
	pte_unmap_unlock(pte - 1, ptl);
551
	return ret;
L
Linus Torvalds 已提交
552 553 554 555 556 557 558 559
}

static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
				unsigned long addr, unsigned long end,
				swp_entry_t entry, struct page *page)
{
	pmd_t *pmd;
	unsigned long next;
560
	int ret;
L
Linus Torvalds 已提交
561 562 563 564 565 566

	pmd = pmd_offset(pud, addr);
	do {
		next = pmd_addr_end(addr, end);
		if (pmd_none_or_clear_bad(pmd))
			continue;
567 568 569
		ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
		if (ret)
			return ret;
L
Linus Torvalds 已提交
570 571 572 573 574 575 576 577 578 579
	} while (pmd++, addr = next, addr != end);
	return 0;
}

static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
				unsigned long addr, unsigned long end,
				swp_entry_t entry, struct page *page)
{
	pud_t *pud;
	unsigned long next;
580
	int ret;
L
Linus Torvalds 已提交
581 582 583 584 585 586

	pud = pud_offset(pgd, addr);
	do {
		next = pud_addr_end(addr, end);
		if (pud_none_or_clear_bad(pud))
			continue;
587 588 589
		ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
		if (ret)
			return ret;
L
Linus Torvalds 已提交
590 591 592 593 594 595 596 597 598
	} while (pud++, addr = next, addr != end);
	return 0;
}

static int unuse_vma(struct vm_area_struct *vma,
				swp_entry_t entry, struct page *page)
{
	pgd_t *pgd;
	unsigned long addr, end, next;
599
	int ret;
L
Linus Torvalds 已提交
600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616

	if (page->mapping) {
		addr = page_address_in_vma(page, vma);
		if (addr == -EFAULT)
			return 0;
		else
			end = addr + PAGE_SIZE;
	} else {
		addr = vma->vm_start;
		end = vma->vm_end;
	}

	pgd = pgd_offset(vma->vm_mm, addr);
	do {
		next = pgd_addr_end(addr, end);
		if (pgd_none_or_clear_bad(pgd))
			continue;
617 618 619
		ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
		if (ret)
			return ret;
L
Linus Torvalds 已提交
620 621 622 623 624 625 626 627
	} while (pgd++, addr = next, addr != end);
	return 0;
}

static int unuse_mm(struct mm_struct *mm,
				swp_entry_t entry, struct page *page)
{
	struct vm_area_struct *vma;
628
	int ret = 0;
L
Linus Torvalds 已提交
629 630 631

	if (!down_read_trylock(&mm->mmap_sem)) {
		/*
632 633
		 * Activate page so shrink_cache is unlikely to unmap its
		 * ptes while lock is dropped, so swapoff can make progress.
L
Linus Torvalds 已提交
634
		 */
635
		activate_page(page);
L
Linus Torvalds 已提交
636 637 638 639 640
		unlock_page(page);
		down_read(&mm->mmap_sem);
		lock_page(page);
	}
	for (vma = mm->mmap; vma; vma = vma->vm_next) {
641
		if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
L
Linus Torvalds 已提交
642 643 644
			break;
	}
	up_read(&mm->mmap_sem);
645
	return (ret < 0)? ret: 0;
L
Linus Torvalds 已提交
646 647 648 649 650 651
}

/*
 * Scan swap_map from current position to next entry still in use.
 * Recycle to start on reaching the end, returning 0 when empty.
 */
652 653
static unsigned int find_next_to_unuse(struct swap_info_struct *si,
					unsigned int prev)
L
Linus Torvalds 已提交
654
{
655 656
	unsigned int max = si->max;
	unsigned int i = prev;
L
Linus Torvalds 已提交
657 658 659
	int count;

	/*
660
	 * No need for swap_lock here: we're just looking
L
Linus Torvalds 已提交
661 662
	 * for whether an entry is in use, not modifying it; false
	 * hits are okay, and sys_swapoff() has already prevented new
663
	 * allocations from this area (while holding swap_lock).
L
Linus Torvalds 已提交
664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698
	 */
	for (;;) {
		if (++i >= max) {
			if (!prev) {
				i = 0;
				break;
			}
			/*
			 * No entries in use at top of swap_map,
			 * loop back to start and recheck there.
			 */
			max = prev + 1;
			prev = 0;
			i = 1;
		}
		count = si->swap_map[i];
		if (count && count != SWAP_MAP_BAD)
			break;
	}
	return i;
}

/*
 * We completely avoid races by reading each swap page in advance,
 * and then search for the process using it.  All the necessary
 * page table adjustments can then be made atomically.
 */
static int try_to_unuse(unsigned int type)
{
	struct swap_info_struct * si = &swap_info[type];
	struct mm_struct *start_mm;
	unsigned short *swap_map;
	unsigned short swcount;
	struct page *page;
	swp_entry_t entry;
699
	unsigned int i = 0;
L
Linus Torvalds 已提交
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
	int retval = 0;
	int reset_overflow = 0;
	int shmem;

	/*
	 * When searching mms for an entry, a good strategy is to
	 * start at the first mm we freed the previous entry from
	 * (though actually we don't notice whether we or coincidence
	 * freed the entry).  Initialize this start_mm with a hold.
	 *
	 * A simpler strategy would be to start at the last mm we
	 * freed the previous entry from; but that would take less
	 * advantage of mmlist ordering, which clusters forked mms
	 * together, child after parent.  If we race with dup_mmap(), we
	 * prefer to resolve parent before child, lest we miss entries
	 * duplicated after we scanned child: using last mm would invert
	 * that.  Though it's only a serious concern when an overflowed
	 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
	 */
	start_mm = &init_mm;
	atomic_inc(&init_mm.mm_users);

	/*
	 * Keep on scanning until all entries have gone.  Usually,
	 * one pass through swap_map is enough, but not necessarily:
	 * there are races when an instance of an entry might be missed.
	 */
	while ((i = find_next_to_unuse(si, i)) != 0) {
		if (signal_pending(current)) {
			retval = -EINTR;
			break;
		}

		/* 
		 * Get a page for the entry, using the existing swap
		 * cache page if there is one.  Otherwise, get a clean
		 * page and read the swap into it. 
		 */
		swap_map = &si->swap_map[i];
		entry = swp_entry(type, i);
740 741
		page = read_swap_cache_async(entry,
					GFP_HIGHUSER_MOVABLE, NULL, 0);
L
Linus Torvalds 已提交
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
		if (!page) {
			/*
			 * Either swap_duplicate() failed because entry
			 * has been freed independently, and will not be
			 * reused since sys_swapoff() already disabled
			 * allocation from here, or alloc_page() failed.
			 */
			if (!*swap_map)
				continue;
			retval = -ENOMEM;
			break;
		}

		/*
		 * Don't hold on to start_mm if it looks like exiting.
		 */
		if (atomic_read(&start_mm->mm_users) == 1) {
			mmput(start_mm);
			start_mm = &init_mm;
			atomic_inc(&init_mm.mm_users);
		}

		/*
		 * Wait for and lock page.  When do_swap_page races with
		 * try_to_unuse, do_swap_page can handle the fault much
		 * faster than try_to_unuse can locate the entry.  This
		 * apparently redundant "wait_on_page_locked" lets try_to_unuse
		 * defer to do_swap_page in such a case - in some tests,
		 * do_swap_page and try_to_unuse repeatedly compete.
		 */
		wait_on_page_locked(page);
		wait_on_page_writeback(page);
		lock_page(page);
		wait_on_page_writeback(page);

		/*
		 * Remove all references to entry.
		 * Whenever we reach init_mm, there's no address space
		 * to search, but use it as a reminder to search shmem.
		 */
		shmem = 0;
		swcount = *swap_map;
		if (swcount > 1) {
			if (start_mm == &init_mm)
				shmem = shmem_unuse(entry, page);
			else
				retval = unuse_mm(start_mm, entry, page);
		}
		if (*swap_map > 1) {
			int set_start_mm = (*swap_map >= swcount);
			struct list_head *p = &start_mm->mmlist;
			struct mm_struct *new_start_mm = start_mm;
			struct mm_struct *prev_mm = start_mm;
			struct mm_struct *mm;

			atomic_inc(&new_start_mm->mm_users);
			atomic_inc(&prev_mm->mm_users);
			spin_lock(&mmlist_lock);
800
			while (*swap_map > 1 && !retval && !shmem &&
L
Linus Torvalds 已提交
801 802
					(p = p->next) != &start_mm->mmlist) {
				mm = list_entry(p, struct mm_struct, mmlist);
803
				if (!atomic_inc_not_zero(&mm->mm_users))
L
Linus Torvalds 已提交
804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831
					continue;
				spin_unlock(&mmlist_lock);
				mmput(prev_mm);
				prev_mm = mm;

				cond_resched();

				swcount = *swap_map;
				if (swcount <= 1)
					;
				else if (mm == &init_mm) {
					set_start_mm = 1;
					shmem = shmem_unuse(entry, page);
				} else
					retval = unuse_mm(mm, entry, page);
				if (set_start_mm && *swap_map < swcount) {
					mmput(new_start_mm);
					atomic_inc(&mm->mm_users);
					new_start_mm = mm;
					set_start_mm = 0;
				}
				spin_lock(&mmlist_lock);
			}
			spin_unlock(&mmlist_lock);
			mmput(prev_mm);
			mmput(start_mm);
			start_mm = new_start_mm;
		}
832 833 834 835 836 837 838
		if (shmem) {
			/* page has already been unlocked and released */
			if (shmem > 0)
				continue;
			retval = shmem;
			break;
		}
L
Linus Torvalds 已提交
839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858
		if (retval) {
			unlock_page(page);
			page_cache_release(page);
			break;
		}

		/*
		 * How could swap count reach 0x7fff when the maximum
		 * pid is 0x7fff, and there's no way to repeat a swap
		 * page within an mm (except in shmem, where it's the
		 * shared object which takes the reference count)?
		 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
		 *
		 * If that's wrong, then we should worry more about
		 * exit_mmap() and do_munmap() cases described above:
		 * we might be resetting SWAP_MAP_MAX too early here.
		 * We know "Undead"s can happen, they're okay, so don't
		 * report them; but do report if we reset SWAP_MAP_MAX.
		 */
		if (*swap_map == SWAP_MAP_MAX) {
859
			spin_lock(&swap_lock);
L
Linus Torvalds 已提交
860
			*swap_map = 1;
861
			spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886
			reset_overflow = 1;
		}

		/*
		 * If a reference remains (rare), we would like to leave
		 * the page in the swap cache; but try_to_unmap could
		 * then re-duplicate the entry once we drop page lock,
		 * so we might loop indefinitely; also, that page could
		 * not be swapped out to other storage meanwhile.  So:
		 * delete from cache even if there's another reference,
		 * after ensuring that the data has been saved to disk -
		 * since if the reference remains (rarer), it will be
		 * read from disk into another page.  Splitting into two
		 * pages would be incorrect if swap supported "shared
		 * private" pages, but they are handled by tmpfs files.
		 */
		if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
			struct writeback_control wbc = {
				.sync_mode = WB_SYNC_NONE,
			};

			swap_writepage(page, &wbc);
			lock_page(page);
			wait_on_page_writeback(page);
		}
887 888
		if (PageSwapCache(page))
			delete_from_swap_cache(page);
L
Linus Torvalds 已提交
889 890 891 892

		/*
		 * So we could skip searching mms once swap count went
		 * to 1, we did not mark any present ptes as dirty: must
893
		 * mark page dirty so shrink_page_list will preserve it.
L
Linus Torvalds 已提交
894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914
		 */
		SetPageDirty(page);
		unlock_page(page);
		page_cache_release(page);

		/*
		 * Make sure that we aren't completely killing
		 * interactive performance.
		 */
		cond_resched();
	}

	mmput(start_mm);
	if (reset_overflow) {
		printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
		swap_overflow = 0;
	}
	return retval;
}

/*
915 916 917
 * After a successful try_to_unuse, if no swap is now in use, we know
 * we can empty the mmlist.  swap_lock must be held on entry and exit.
 * Note that mmlist_lock nests inside swap_lock, and an mm must be
L
Linus Torvalds 已提交
918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949
 * added to the mmlist just after page_duplicate - before would be racy.
 */
static void drain_mmlist(void)
{
	struct list_head *p, *next;
	unsigned int i;

	for (i = 0; i < nr_swapfiles; i++)
		if (swap_info[i].inuse_pages)
			return;
	spin_lock(&mmlist_lock);
	list_for_each_safe(p, next, &init_mm.mmlist)
		list_del_init(p);
	spin_unlock(&mmlist_lock);
}

/*
 * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
 * corresponds to page offset `offset'.
 */
sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
{
	struct swap_extent *se = sis->curr_swap_extent;
	struct swap_extent *start_se = se;

	for ( ; ; ) {
		struct list_head *lh;

		if (se->start_page <= offset &&
				offset < (se->start_page + se->nr_pages)) {
			return se->start_block + (offset - se->start_page);
		}
950
		lh = se->list.next;
L
Linus Torvalds 已提交
951
		if (lh == &sis->extent_list)
952
			lh = lh->next;
L
Linus Torvalds 已提交
953 954 955 956 957 958
		se = list_entry(lh, struct swap_extent, list);
		sis->curr_swap_extent = se;
		BUG_ON(se == start_se);		/* It *must* be present */
	}
}

959
#ifdef CONFIG_HIBERNATION
960 961 962 963 964 965 966 967 968 969 970 971 972 973
/*
 * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
 * corresponding to given index in swap_info (swap type).
 */
sector_t swapdev_block(int swap_type, pgoff_t offset)
{
	struct swap_info_struct *sis;

	if (swap_type >= nr_swapfiles)
		return 0;

	sis = swap_info + swap_type;
	return (sis->flags & SWP_WRITEOK) ? map_swap_page(sis, offset) : 0;
}
974
#endif /* CONFIG_HIBERNATION */
975

L
Linus Torvalds 已提交
976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992
/*
 * Free all of a swapdev's extent information
 */
static void destroy_swap_extents(struct swap_info_struct *sis)
{
	while (!list_empty(&sis->extent_list)) {
		struct swap_extent *se;

		se = list_entry(sis->extent_list.next,
				struct swap_extent, list);
		list_del(&se->list);
		kfree(se);
	}
}

/*
 * Add a block range (and the corresponding page range) into this swapdev's
993
 * extent list.  The extent list is kept sorted in page order.
L
Linus Torvalds 已提交
994
 *
995
 * This function rather assumes that it is called in ascending page order.
L
Linus Torvalds 已提交
996 997 998 999 1000 1001 1002 1003 1004
 */
static int
add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
		unsigned long nr_pages, sector_t start_block)
{
	struct swap_extent *se;
	struct swap_extent *new_se;
	struct list_head *lh;

1005 1006
	lh = sis->extent_list.prev;	/* The highest page extent */
	if (lh != &sis->extent_list) {
L
Linus Torvalds 已提交
1007
		se = list_entry(lh, struct swap_extent, list);
1008 1009
		BUG_ON(se->start_page + se->nr_pages != start_page);
		if (se->start_block + se->nr_pages == start_block) {
L
Linus Torvalds 已提交
1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025
			/* Merge it */
			se->nr_pages += nr_pages;
			return 0;
		}
	}

	/*
	 * No merge.  Insert a new extent, preserving ordering.
	 */
	new_se = kmalloc(sizeof(*se), GFP_KERNEL);
	if (new_se == NULL)
		return -ENOMEM;
	new_se->start_page = start_page;
	new_se->nr_pages = nr_pages;
	new_se->start_block = start_block;

1026
	list_add_tail(&new_se->list, &sis->extent_list);
1027
	return 1;
L
Linus Torvalds 已提交
1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049
}

/*
 * A `swap extent' is a simple thing which maps a contiguous range of pages
 * onto a contiguous range of disk blocks.  An ordered list of swap extents
 * is built at swapon time and is then used at swap_writepage/swap_readpage
 * time for locating where on disk a page belongs.
 *
 * If the swapfile is an S_ISBLK block device, a single extent is installed.
 * This is done so that the main operating code can treat S_ISBLK and S_ISREG
 * swap files identically.
 *
 * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
 * extent list operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
 * swapfiles are handled *identically* after swapon time.
 *
 * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
 * and will parse them into an ordered extent list, in PAGE_SIZE chunks.  If
 * some stray blocks are found which do not fall within the PAGE_SIZE alignment
 * requirements, they are simply tossed out - we will never use those blocks
 * for swapping.
 *
1050
 * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon.  This
L
Linus Torvalds 已提交
1051 1052 1053 1054 1055 1056 1057 1058 1059 1060
 * prevents root from shooting her foot off by ftruncating an in-use swapfile,
 * which will scribble on the fs.
 *
 * The amount of disk space which a single swap extent represents varies.
 * Typically it is in the 1-4 megabyte range.  So we can have hundreds of
 * extents in the list.  To avoid much list walking, we cache the previous
 * search location in `curr_swap_extent', and start new searches from there.
 * This is extremely effective.  The average number of iterations in
 * map_swap_page() has been measured at about 0.3 per page.  - akpm.
 */
1061
static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
L
Linus Torvalds 已提交
1062 1063 1064 1065 1066 1067 1068
{
	struct inode *inode;
	unsigned blocks_per_page;
	unsigned long page_no;
	unsigned blkbits;
	sector_t probe_block;
	sector_t last_block;
1069 1070 1071
	sector_t lowest_block = -1;
	sector_t highest_block = 0;
	int nr_extents = 0;
L
Linus Torvalds 已提交
1072 1073 1074 1075 1076
	int ret;

	inode = sis->swap_file->f_mapping->host;
	if (S_ISBLK(inode->i_mode)) {
		ret = add_swap_extent(sis, 0, sis->max, 0);
1077
		*span = sis->pages;
L
Linus Torvalds 已提交
1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121
		goto done;
	}

	blkbits = inode->i_blkbits;
	blocks_per_page = PAGE_SIZE >> blkbits;

	/*
	 * Map all the blocks into the extent list.  This code doesn't try
	 * to be very smart.
	 */
	probe_block = 0;
	page_no = 0;
	last_block = i_size_read(inode) >> blkbits;
	while ((probe_block + blocks_per_page) <= last_block &&
			page_no < sis->max) {
		unsigned block_in_page;
		sector_t first_block;

		first_block = bmap(inode, probe_block);
		if (first_block == 0)
			goto bad_bmap;

		/*
		 * It must be PAGE_SIZE aligned on-disk
		 */
		if (first_block & (blocks_per_page - 1)) {
			probe_block++;
			goto reprobe;
		}

		for (block_in_page = 1; block_in_page < blocks_per_page;
					block_in_page++) {
			sector_t block;

			block = bmap(inode, probe_block + block_in_page);
			if (block == 0)
				goto bad_bmap;
			if (block != first_block + block_in_page) {
				/* Discontiguity */
				probe_block++;
				goto reprobe;
			}
		}

1122 1123 1124 1125 1126 1127 1128 1129
		first_block >>= (PAGE_SHIFT - blkbits);
		if (page_no) {	/* exclude the header page */
			if (first_block < lowest_block)
				lowest_block = first_block;
			if (first_block > highest_block)
				highest_block = first_block;
		}

L
Linus Torvalds 已提交
1130 1131 1132
		/*
		 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
		 */
1133 1134
		ret = add_swap_extent(sis, page_no, 1, first_block);
		if (ret < 0)
L
Linus Torvalds 已提交
1135
			goto out;
1136
		nr_extents += ret;
L
Linus Torvalds 已提交
1137 1138 1139 1140 1141
		page_no++;
		probe_block += blocks_per_page;
reprobe:
		continue;
	}
1142 1143
	ret = nr_extents;
	*span = 1 + highest_block - lowest_block;
L
Linus Torvalds 已提交
1144
	if (page_no == 0)
1145
		page_no = 1;	/* force Empty message */
L
Linus Torvalds 已提交
1146
	sis->max = page_no;
1147
	sis->pages = page_no - 1;
L
Linus Torvalds 已提交
1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168
	sis->highest_bit = page_no - 1;
done:
	sis->curr_swap_extent = list_entry(sis->extent_list.prev,
					struct swap_extent, list);
	goto out;
bad_bmap:
	printk(KERN_ERR "swapon: swapfile has holes\n");
	ret = -EINVAL;
out:
	return ret;
}

#if 0	/* We don't need this yet */
#include <linux/backing-dev.h>
int page_queue_congested(struct page *page)
{
	struct backing_dev_info *bdi;

	BUG_ON(!PageLocked(page));	/* It pins the swap_info_struct */

	if (PageSwapCache(page)) {
H
Hugh Dickins 已提交
1169
		swp_entry_t entry = { .val = page_private(page) };
L
Linus Torvalds 已提交
1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206
		struct swap_info_struct *sis;

		sis = get_swap_info_struct(swp_type(entry));
		bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
	} else
		bdi = page->mapping->backing_dev_info;
	return bdi_write_congested(bdi);
}
#endif

asmlinkage long sys_swapoff(const char __user * specialfile)
{
	struct swap_info_struct * p = NULL;
	unsigned short *swap_map;
	struct file *swap_file, *victim;
	struct address_space *mapping;
	struct inode *inode;
	char * pathname;
	int i, type, prev;
	int err;
	
	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	pathname = getname(specialfile);
	err = PTR_ERR(pathname);
	if (IS_ERR(pathname))
		goto out;

	victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
	putname(pathname);
	err = PTR_ERR(victim);
	if (IS_ERR(victim))
		goto out;

	mapping = victim->f_mapping;
	prev = -1;
1207
	spin_lock(&swap_lock);
L
Linus Torvalds 已提交
1208 1209 1210 1211 1212 1213 1214 1215 1216 1217
	for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
		p = swap_info + type;
		if ((p->flags & SWP_ACTIVE) == SWP_ACTIVE) {
			if (p->swap_file->f_mapping == mapping)
				break;
		}
		prev = type;
	}
	if (type < 0) {
		err = -EINVAL;
1218
		spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1219 1220 1221 1222 1223 1224
		goto out_dput;
	}
	if (!security_vm_enough_memory(p->pages))
		vm_unacct_memory(p->pages);
	else {
		err = -ENOMEM;
1225
		spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239
		goto out_dput;
	}
	if (prev < 0) {
		swap_list.head = p->next;
	} else {
		swap_info[prev].next = p->next;
	}
	if (type == swap_list.next) {
		/* just pick something that's safe... */
		swap_list.next = swap_list.head;
	}
	nr_swap_pages -= p->pages;
	total_swap_pages -= p->pages;
	p->flags &= ~SWP_WRITEOK;
1240
	spin_unlock(&swap_lock);
1241

L
Linus Torvalds 已提交
1242 1243 1244 1245 1246 1247
	current->flags |= PF_SWAPOFF;
	err = try_to_unuse(type);
	current->flags &= ~PF_SWAPOFF;

	if (err) {
		/* re-insert swap space back into swap_list */
1248
		spin_lock(&swap_lock);
L
Linus Torvalds 已提交
1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259
		for (prev = -1, i = swap_list.head; i >= 0; prev = i, i = swap_info[i].next)
			if (p->prio >= swap_info[i].prio)
				break;
		p->next = i;
		if (prev < 0)
			swap_list.head = swap_list.next = p - swap_info;
		else
			swap_info[prev].next = p - swap_info;
		nr_swap_pages += p->pages;
		total_swap_pages += p->pages;
		p->flags |= SWP_WRITEOK;
1260
		spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1261 1262
		goto out_dput;
	}
1263 1264 1265 1266 1267

	/* wait for any unplug function to finish */
	down_write(&swap_unplug_sem);
	up_write(&swap_unplug_sem);

1268
	destroy_swap_extents(p);
I
Ingo Molnar 已提交
1269
	mutex_lock(&swapon_mutex);
1270 1271 1272
	spin_lock(&swap_lock);
	drain_mmlist();

1273 1274 1275
	/* wait for anyone still in scan_swap_map */
	p->highest_bit = 0;		/* cuts scans short */
	while (p->flags >= SWP_SCANNING) {
1276
		spin_unlock(&swap_lock);
1277
		schedule_timeout_uninterruptible(1);
1278
		spin_lock(&swap_lock);
1279 1280
	}

L
Linus Torvalds 已提交
1281 1282 1283 1284 1285 1286
	swap_file = p->swap_file;
	p->swap_file = NULL;
	p->max = 0;
	swap_map = p->swap_map;
	p->swap_map = NULL;
	p->flags = 0;
1287
	spin_unlock(&swap_lock);
I
Ingo Molnar 已提交
1288
	mutex_unlock(&swapon_mutex);
L
Linus Torvalds 已提交
1289 1290 1291 1292 1293 1294 1295
	vfree(swap_map);
	inode = mapping->host;
	if (S_ISBLK(inode->i_mode)) {
		struct block_device *bdev = I_BDEV(inode);
		set_blocksize(bdev, p->old_block_size);
		bd_release(bdev);
	} else {
1296
		mutex_lock(&inode->i_mutex);
L
Linus Torvalds 已提交
1297
		inode->i_flags &= ~S_SWAPFILE;
1298
		mutex_unlock(&inode->i_mutex);
L
Linus Torvalds 已提交
1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316
	}
	filp_close(swap_file, NULL);
	err = 0;

out_dput:
	filp_close(victim, NULL);
out:
	return err;
}

#ifdef CONFIG_PROC_FS
/* iterator */
static void *swap_start(struct seq_file *swap, loff_t *pos)
{
	struct swap_info_struct *ptr = swap_info;
	int i;
	loff_t l = *pos;

I
Ingo Molnar 已提交
1317
	mutex_lock(&swapon_mutex);
L
Linus Torvalds 已提交
1318

1319 1320 1321
	if (!l)
		return SEQ_START_TOKEN;

L
Linus Torvalds 已提交
1322 1323 1324
	for (i = 0; i < nr_swapfiles; i++, ptr++) {
		if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
			continue;
1325
		if (!--l)
L
Linus Torvalds 已提交
1326 1327 1328 1329 1330 1331 1332 1333
			return ptr;
	}

	return NULL;
}

static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
{
1334
	struct swap_info_struct *ptr;
L
Linus Torvalds 已提交
1335 1336
	struct swap_info_struct *endptr = swap_info + nr_swapfiles;

1337 1338 1339 1340 1341 1342 1343 1344
	if (v == SEQ_START_TOKEN)
		ptr = swap_info;
	else {
		ptr = v;
		ptr++;
	}

	for (; ptr < endptr; ptr++) {
L
Linus Torvalds 已提交
1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355
		if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
			continue;
		++*pos;
		return ptr;
	}

	return NULL;
}

static void swap_stop(struct seq_file *swap, void *v)
{
I
Ingo Molnar 已提交
1356
	mutex_unlock(&swapon_mutex);
L
Linus Torvalds 已提交
1357 1358 1359 1360 1361 1362 1363 1364
}

static int swap_show(struct seq_file *swap, void *v)
{
	struct swap_info_struct *ptr = v;
	struct file *file;
	int len;

1365 1366 1367 1368
	if (ptr == SEQ_START_TOKEN) {
		seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
		return 0;
	}
L
Linus Torvalds 已提交
1369 1370

	file = ptr->swap_file;
1371
	len = seq_path(swap, file->f_path.mnt, file->f_path.dentry, " \t\n\\");
1372
	seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
L
Linus Torvalds 已提交
1373
		       len < 40 ? 40 - len : 1, " ",
1374
		       S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
L
Linus Torvalds 已提交
1375 1376 1377 1378 1379 1380 1381
				"partition" : "file\t",
		       ptr->pages << (PAGE_SHIFT - 10),
		       ptr->inuse_pages << (PAGE_SHIFT - 10),
		       ptr->prio);
	return 0;
}

1382
static const struct seq_operations swaps_op = {
L
Linus Torvalds 已提交
1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393
	.start =	swap_start,
	.next =		swap_next,
	.stop =		swap_stop,
	.show =		swap_show
};

static int swaps_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &swaps_op);
}

1394
static const struct file_operations proc_swaps_operations = {
L
Linus Torvalds 已提交
1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430
	.open		= swaps_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= seq_release,
};

static int __init procswaps_init(void)
{
	struct proc_dir_entry *entry;

	entry = create_proc_entry("swaps", 0, NULL);
	if (entry)
		entry->proc_fops = &proc_swaps_operations;
	return 0;
}
__initcall(procswaps_init);
#endif /* CONFIG_PROC_FS */

/*
 * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
 *
 * The swapon system call
 */
asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
{
	struct swap_info_struct * p;
	char *name = NULL;
	struct block_device *bdev = NULL;
	struct file *swap_file = NULL;
	struct address_space *mapping;
	unsigned int type;
	int i, prev;
	int error;
	static int least_priority;
	union swap_header *swap_header = NULL;
	int swap_header_version;
1431 1432
	unsigned int nr_good_pages = 0;
	int nr_extents = 0;
1433
	sector_t span;
L
Linus Torvalds 已提交
1434 1435 1436 1437 1438 1439 1440 1441 1442
	unsigned long maxpages = 1;
	int swapfilesize;
	unsigned short *swap_map;
	struct page *page = NULL;
	struct inode *inode = NULL;
	int did_down = 0;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
1443
	spin_lock(&swap_lock);
L
Linus Torvalds 已提交
1444 1445 1446 1447 1448
	p = swap_info;
	for (type = 0 ; type < nr_swapfiles ; type++,p++)
		if (!(p->flags & SWP_USED))
			break;
	error = -EPERM;
1449
	if (type >= MAX_SWAPFILES) {
1450
		spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470
		goto out;
	}
	if (type >= nr_swapfiles)
		nr_swapfiles = type+1;
	INIT_LIST_HEAD(&p->extent_list);
	p->flags = SWP_USED;
	p->swap_file = NULL;
	p->old_block_size = 0;
	p->swap_map = NULL;
	p->lowest_bit = 0;
	p->highest_bit = 0;
	p->cluster_nr = 0;
	p->inuse_pages = 0;
	p->next = -1;
	if (swap_flags & SWAP_FLAG_PREFER) {
		p->prio =
		  (swap_flags & SWAP_FLAG_PRIO_MASK)>>SWAP_FLAG_PRIO_SHIFT;
	} else {
		p->prio = --least_priority;
	}
1471
	spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504
	name = getname(specialfile);
	error = PTR_ERR(name);
	if (IS_ERR(name)) {
		name = NULL;
		goto bad_swap_2;
	}
	swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
	error = PTR_ERR(swap_file);
	if (IS_ERR(swap_file)) {
		swap_file = NULL;
		goto bad_swap_2;
	}

	p->swap_file = swap_file;
	mapping = swap_file->f_mapping;
	inode = mapping->host;

	error = -EBUSY;
	for (i = 0; i < nr_swapfiles; i++) {
		struct swap_info_struct *q = &swap_info[i];

		if (i == type || !q->swap_file)
			continue;
		if (mapping == q->swap_file->f_mapping)
			goto bad_swap;
	}

	error = -EINVAL;
	if (S_ISBLK(inode->i_mode)) {
		bdev = I_BDEV(inode);
		error = bd_claim(bdev, sys_swapon);
		if (error < 0) {
			bdev = NULL;
R
Rob Landley 已提交
1505
			error = -EINVAL;
L
Linus Torvalds 已提交
1506 1507 1508 1509 1510 1511 1512 1513 1514
			goto bad_swap;
		}
		p->old_block_size = block_size(bdev);
		error = set_blocksize(bdev, PAGE_SIZE);
		if (error < 0)
			goto bad_swap;
		p->bdev = bdev;
	} else if (S_ISREG(inode->i_mode)) {
		p->bdev = inode->i_sb->s_bdev;
1515
		mutex_lock(&inode->i_mutex);
L
Linus Torvalds 已提交
1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533
		did_down = 1;
		if (IS_SWAPFILE(inode)) {
			error = -EBUSY;
			goto bad_swap;
		}
	} else {
		goto bad_swap;
	}

	swapfilesize = i_size_read(inode) >> PAGE_SHIFT;

	/*
	 * Read the swap header.
	 */
	if (!mapping->a_ops->readpage) {
		error = -EINVAL;
		goto bad_swap;
	}
1534
	page = read_mapping_page(mapping, 0, swap_file);
L
Linus Torvalds 已提交
1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546
	if (IS_ERR(page)) {
		error = PTR_ERR(page);
		goto bad_swap;
	}
	kmap(page);
	swap_header = page_address(page);

	if (!memcmp("SWAP-SPACE",swap_header->magic.magic,10))
		swap_header_version = 1;
	else if (!memcmp("SWAPSPACE2",swap_header->magic.magic,10))
		swap_header_version = 2;
	else {
1547
		printk(KERN_ERR "Unable to find swap-space signature\n");
L
Linus Torvalds 已提交
1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569
		error = -EINVAL;
		goto bad_swap;
	}
	
	switch (swap_header_version) {
	case 1:
		printk(KERN_ERR "version 0 swap is no longer supported. "
			"Use mkswap -v1 %s\n", name);
		error = -EINVAL;
		goto bad_swap;
	case 2:
		/* Check the swap header's sub-version and the size of
                   the swap file and bad block lists */
		if (swap_header->info.version != 1) {
			printk(KERN_WARNING
			       "Unable to handle swap header version %d\n",
			       swap_header->info.version);
			error = -EINVAL;
			goto bad_swap;
		}

		p->lowest_bit  = 1;
1570 1571
		p->cluster_next = 1;

L
Linus Torvalds 已提交
1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591
		/*
		 * Find out how many pages are allowed for a single swap
		 * device. There are two limiting factors: 1) the number of
		 * bits for the swap offset in the swp_entry_t type and
		 * 2) the number of bits in the a swap pte as defined by
		 * the different architectures. In order to find the
		 * largest possible bit mask a swap entry with swap type 0
		 * and swap offset ~0UL is created, encoded to a swap pte,
		 * decoded to a swp_entry_t again and finally the swap
		 * offset is extracted. This will mask all the bits from
		 * the initial ~0UL mask that can't be encoded in either
		 * the swp_entry_t or the architecture definition of a
		 * swap pte.
		 */
		maxpages = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0,~0UL)))) - 1;
		if (maxpages > swap_header->info.last_page)
			maxpages = swap_header->info.last_page;
		p->highest_bit = maxpages - 1;

		error = -EINVAL;
1592 1593
		if (!maxpages)
			goto bad_swap;
1594 1595 1596 1597 1598
		if (swapfilesize && maxpages > swapfilesize) {
			printk(KERN_WARNING
			       "Swap area shorter than signature indicates\n");
			goto bad_swap;
		}
1599 1600
		if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
			goto bad_swap;
L
Linus Torvalds 已提交
1601 1602
		if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
			goto bad_swap;
1603

L
Linus Torvalds 已提交
1604 1605 1606 1607 1608 1609 1610 1611
		/* OK, set up the swap map and apply the bad block list */
		if (!(p->swap_map = vmalloc(maxpages * sizeof(short)))) {
			error = -ENOMEM;
			goto bad_swap;
		}

		error = 0;
		memset(p->swap_map, 0, maxpages * sizeof(short));
1612 1613 1614
		for (i = 0; i < swap_header->info.nr_badpages; i++) {
			int page_nr = swap_header->info.badpages[i];
			if (page_nr <= 0 || page_nr >= swap_header->info.last_page)
L
Linus Torvalds 已提交
1615 1616
				error = -EINVAL;
			else
1617
				p->swap_map[page_nr] = SWAP_MAP_BAD;
L
Linus Torvalds 已提交
1618 1619 1620 1621
		}
		nr_good_pages = swap_header->info.last_page -
				swap_header->info.nr_badpages -
				1 /* header page */;
1622
		if (error)
L
Linus Torvalds 已提交
1623 1624
			goto bad_swap;
	}
1625 1626 1627 1628 1629

	if (nr_good_pages) {
		p->swap_map[0] = SWAP_MAP_BAD;
		p->max = maxpages;
		p->pages = nr_good_pages;
1630 1631 1632
		nr_extents = setup_swap_extents(p, &span);
		if (nr_extents < 0) {
			error = nr_extents;
1633
			goto bad_swap;
1634
		}
1635 1636
		nr_good_pages = p->pages;
	}
L
Linus Torvalds 已提交
1637 1638 1639 1640 1641 1642
	if (!nr_good_pages) {
		printk(KERN_WARNING "Empty swap-file\n");
		error = -EINVAL;
		goto bad_swap;
	}

I
Ingo Molnar 已提交
1643
	mutex_lock(&swapon_mutex);
1644
	spin_lock(&swap_lock);
L
Linus Torvalds 已提交
1645 1646 1647
	p->flags = SWP_ACTIVE;
	nr_swap_pages += nr_good_pages;
	total_swap_pages += nr_good_pages;
1648

1649
	printk(KERN_INFO "Adding %uk swap on %s.  "
1650 1651 1652
			"Priority:%d extents:%d across:%lluk\n",
		nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
		nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10));
L
Linus Torvalds 已提交
1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667

	/* insert swap space into swap_list: */
	prev = -1;
	for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
		if (p->prio >= swap_info[i].prio) {
			break;
		}
		prev = i;
	}
	p->next = i;
	if (prev < 0) {
		swap_list.head = swap_list.next = p - swap_info;
	} else {
		swap_info[prev].next = p - swap_info;
	}
1668
	spin_unlock(&swap_lock);
I
Ingo Molnar 已提交
1669
	mutex_unlock(&swapon_mutex);
L
Linus Torvalds 已提交
1670 1671 1672 1673 1674 1675 1676
	error = 0;
	goto out;
bad_swap:
	if (bdev) {
		set_blocksize(bdev, p->old_block_size);
		bd_release(bdev);
	}
1677
	destroy_swap_extents(p);
L
Linus Torvalds 已提交
1678
bad_swap_2:
1679
	spin_lock(&swap_lock);
L
Linus Torvalds 已提交
1680 1681 1682 1683 1684 1685
	swap_map = p->swap_map;
	p->swap_file = NULL;
	p->swap_map = NULL;
	p->flags = 0;
	if (!(swap_flags & SWAP_FLAG_PREFER))
		++least_priority;
1686
	spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699
	vfree(swap_map);
	if (swap_file)
		filp_close(swap_file, NULL);
out:
	if (page && !IS_ERR(page)) {
		kunmap(page);
		page_cache_release(page);
	}
	if (name)
		putname(name);
	if (did_down) {
		if (!error)
			inode->i_flags |= S_SWAPFILE;
1700
		mutex_unlock(&inode->i_mutex);
L
Linus Torvalds 已提交
1701 1702 1703 1704 1705 1706 1707 1708 1709
	}
	return error;
}

void si_swapinfo(struct sysinfo *val)
{
	unsigned int i;
	unsigned long nr_to_be_unused = 0;

1710
	spin_lock(&swap_lock);
L
Linus Torvalds 已提交
1711 1712 1713 1714 1715 1716 1717 1718
	for (i = 0; i < nr_swapfiles; i++) {
		if (!(swap_info[i].flags & SWP_USED) ||
		     (swap_info[i].flags & SWP_WRITEOK))
			continue;
		nr_to_be_unused += swap_info[i].inuse_pages;
	}
	val->freeswap = nr_swap_pages + nr_to_be_unused;
	val->totalswap = total_swap_pages + nr_to_be_unused;
1719
	spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733
}

/*
 * Verify that a swap entry is valid and increment its swap map count.
 *
 * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
 * "permanent", but will be reclaimed by the next swapoff.
 */
int swap_duplicate(swp_entry_t entry)
{
	struct swap_info_struct * p;
	unsigned long offset, type;
	int result = 0;

1734 1735 1736
	if (is_migration_entry(entry))
		return 1;

L
Linus Torvalds 已提交
1737 1738 1739 1740 1741 1742
	type = swp_type(entry);
	if (type >= nr_swapfiles)
		goto bad_file;
	p = type + swap_info;
	offset = swp_offset(entry);

1743
	spin_lock(&swap_lock);
L
Linus Torvalds 已提交
1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754
	if (offset < p->max && p->swap_map[offset]) {
		if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
			p->swap_map[offset]++;
			result = 1;
		} else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
			if (swap_overflow++ < 5)
				printk(KERN_WARNING "swap_dup: swap entry overflow\n");
			p->swap_map[offset] = SWAP_MAP_MAX;
			result = 1;
		}
	}
1755
	spin_unlock(&swap_lock);
L
Linus Torvalds 已提交
1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770
out:
	return result;

bad_file:
	printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
	goto out;
}

struct swap_info_struct *
get_swap_info_struct(unsigned type)
{
	return &swap_info[type];
}

/*
1771
 * swap_lock prevents swap_map being freed. Don't grab an extra
L
Linus Torvalds 已提交
1772 1773 1774 1775
 * reference on the swaphandle, it doesn't matter if it becomes unused.
 */
int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
{
1776
	struct swap_info_struct *si;
H
Hugh Dickins 已提交
1777
	int our_page_cluster = page_cluster;
1778 1779 1780
	pgoff_t target, toff;
	pgoff_t base, end;
	int nr_pages = 0;
L
Linus Torvalds 已提交
1781

H
Hugh Dickins 已提交
1782
	if (!our_page_cluster)	/* no readahead */
L
Linus Torvalds 已提交
1783
		return 0;
1784 1785 1786 1787 1788 1789 1790

	si = &swap_info[swp_type(entry)];
	target = swp_offset(entry);
	base = (target >> our_page_cluster) << our_page_cluster;
	end = base + (1 << our_page_cluster);
	if (!base)		/* first page is swap header */
		base++;
L
Linus Torvalds 已提交
1791

1792
	spin_lock(&swap_lock);
1793 1794 1795 1796 1797 1798 1799 1800 1801
	if (end > si->max)	/* don't go beyond end of map */
		end = si->max;

	/* Count contiguous allocated slots above our target */
	for (toff = target; ++toff < end; nr_pages++) {
		/* Don't read in free or bad pages */
		if (!si->swap_map[toff])
			break;
		if (si->swap_map[toff] == SWAP_MAP_BAD)
L
Linus Torvalds 已提交
1802
			break;
1803 1804 1805
	}
	/* Count contiguous allocated slots below our target */
	for (toff = target; --toff >= base; nr_pages++) {
L
Linus Torvalds 已提交
1806
		/* Don't read in free or bad pages */
1807
		if (!si->swap_map[toff])
L
Linus Torvalds 已提交
1808
			break;
1809
		if (si->swap_map[toff] == SWAP_MAP_BAD)
L
Linus Torvalds 已提交
1810
			break;
1811
	}
1812
	spin_unlock(&swap_lock);
1813 1814 1815 1816 1817 1818 1819

	/*
	 * Indicate starting offset, and return number of pages to get:
	 * if only 1, say 0, since there's then no readahead to be done.
	 */
	*offset = ++toff;
	return nr_pages? ++nr_pages: 0;
L
Linus Torvalds 已提交
1820
}