xref: /openbmc/linux/mm/swapfile.c (revision c60aa176c6de82703f064082b909496fc4fee956)
1 /*
2  *  linux/mm/swapfile.c
3  *
4  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
5  *  Swap reorganised 29.12.95, Stephen Tweedie
6  */
7 
8 #include <linux/mm.h>
9 #include <linux/hugetlb.h>
10 #include <linux/mman.h>
11 #include <linux/slab.h>
12 #include <linux/kernel_stat.h>
13 #include <linux/swap.h>
14 #include <linux/vmalloc.h>
15 #include <linux/pagemap.h>
16 #include <linux/namei.h>
17 #include <linux/shm.h>
18 #include <linux/blkdev.h>
19 #include <linux/random.h>
20 #include <linux/writeback.h>
21 #include <linux/proc_fs.h>
22 #include <linux/seq_file.h>
23 #include <linux/init.h>
24 #include <linux/module.h>
25 #include <linux/rmap.h>
26 #include <linux/security.h>
27 #include <linux/backing-dev.h>
28 #include <linux/mutex.h>
29 #include <linux/capability.h>
30 #include <linux/syscalls.h>
31 #include <linux/memcontrol.h>
32 
33 #include <asm/pgtable.h>
34 #include <asm/tlbflush.h>
35 #include <linux/swapops.h>
36 
37 static DEFINE_SPINLOCK(swap_lock);
38 static unsigned int nr_swapfiles;
39 long nr_swap_pages;
40 long total_swap_pages;
41 static int swap_overflow;
42 static int least_priority;
43 
44 static const char Bad_file[] = "Bad swap file entry ";
45 static const char Unused_file[] = "Unused swap file entry ";
46 static const char Bad_offset[] = "Bad swap offset entry ";
47 static const char Unused_offset[] = "Unused swap offset entry ";
48 
49 static struct swap_list_t swap_list = {-1, -1};
50 
51 static struct swap_info_struct swap_info[MAX_SWAPFILES];
52 
53 static DEFINE_MUTEX(swapon_mutex);
54 
55 /*
56  * We need this because the bdev->unplug_fn can sleep and we cannot
57  * hold swap_lock while calling the unplug_fn. And swap_lock
58  * cannot be turned into a mutex.
59  */
60 static DECLARE_RWSEM(swap_unplug_sem);
61 
62 void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
63 {
64 	swp_entry_t entry;
65 
66 	down_read(&swap_unplug_sem);
67 	entry.val = page_private(page);
68 	if (PageSwapCache(page)) {
69 		struct block_device *bdev = swap_info[swp_type(entry)].bdev;
70 		struct backing_dev_info *bdi;
71 
72 		/*
73 		 * If the page is removed from swapcache from under us (with a
74 		 * racy try_to_unuse/swapoff) we need an additional reference
75 		 * count to avoid reading garbage from page_private(page) above.
76 		 * If the WARN_ON triggers during a swapoff it maybe the race
77 		 * condition and it's harmless. However if it triggers without
78 		 * swapoff it signals a problem.
79 		 */
80 		WARN_ON(page_count(page) <= 1);
81 
82 		bdi = bdev->bd_inode->i_mapping->backing_dev_info;
83 		blk_run_backing_dev(bdi, page);
84 	}
85 	up_read(&swap_unplug_sem);
86 }
87 
88 /*
89  * swapon tell device that all the old swap contents can be discarded,
90  * to allow the swap device to optimize its wear-levelling.
91  */
92 static int discard_swap(struct swap_info_struct *si)
93 {
94 	struct swap_extent *se;
95 	int err = 0;
96 
97 	list_for_each_entry(se, &si->extent_list, list) {
98 		sector_t start_block = se->start_block << (PAGE_SHIFT - 9);
99 		pgoff_t nr_blocks = se->nr_pages << (PAGE_SHIFT - 9);
100 
101 		if (se->start_page == 0) {
102 			/* Do not discard the swap header page! */
103 			start_block += 1 << (PAGE_SHIFT - 9);
104 			nr_blocks -= 1 << (PAGE_SHIFT - 9);
105 			if (!nr_blocks)
106 				continue;
107 		}
108 
109 		err = blkdev_issue_discard(si->bdev, start_block,
110 						nr_blocks, GFP_KERNEL);
111 		if (err)
112 			break;
113 
114 		cond_resched();
115 	}
116 	return err;		/* That will often be -EOPNOTSUPP */
117 }
118 
119 /*
120  * swap allocation tell device that a cluster of swap can now be discarded,
121  * to allow the swap device to optimize its wear-levelling.
122  */
123 static void discard_swap_cluster(struct swap_info_struct *si,
124 				 pgoff_t start_page, pgoff_t nr_pages)
125 {
126 	struct swap_extent *se = si->curr_swap_extent;
127 	int found_extent = 0;
128 
129 	while (nr_pages) {
130 		struct list_head *lh;
131 
132 		if (se->start_page <= start_page &&
133 		    start_page < se->start_page + se->nr_pages) {
134 			pgoff_t offset = start_page - se->start_page;
135 			sector_t start_block = se->start_block + offset;
136 			pgoff_t nr_blocks = se->nr_pages - offset;
137 
138 			if (nr_blocks > nr_pages)
139 				nr_blocks = nr_pages;
140 			start_page += nr_blocks;
141 			nr_pages -= nr_blocks;
142 
143 			if (!found_extent++)
144 				si->curr_swap_extent = se;
145 
146 			start_block <<= PAGE_SHIFT - 9;
147 			nr_blocks <<= PAGE_SHIFT - 9;
148 			if (blkdev_issue_discard(si->bdev, start_block,
149 							nr_blocks, GFP_NOIO))
150 				break;
151 		}
152 
153 		lh = se->list.next;
154 		if (lh == &si->extent_list)
155 			lh = lh->next;
156 		se = list_entry(lh, struct swap_extent, list);
157 	}
158 }
159 
160 static int wait_for_discard(void *word)
161 {
162 	schedule();
163 	return 0;
164 }
165 
166 #define SWAPFILE_CLUSTER	256
167 #define LATENCY_LIMIT		256
168 
169 static inline unsigned long scan_swap_map(struct swap_info_struct *si)
170 {
171 	unsigned long offset;
172 	unsigned long scan_base;
173 	unsigned long last_in_cluster = 0;
174 	int latency_ration = LATENCY_LIMIT;
175 	int found_free_cluster = 0;
176 
177 	/*
178 	 * We try to cluster swap pages by allocating them sequentially
179 	 * in swap.  Once we've allocated SWAPFILE_CLUSTER pages this
180 	 * way, however, we resort to first-free allocation, starting
181 	 * a new cluster.  This prevents us from scattering swap pages
182 	 * all over the entire swap partition, so that we reduce
183 	 * overall disk seek times between swap pages.  -- sct
184 	 * But we do now try to find an empty cluster.  -Andrea
185 	 * And we let swap pages go all over an SSD partition.  Hugh
186 	 */
187 
188 	si->flags += SWP_SCANNING;
189 	scan_base = offset = si->cluster_next;
190 
191 	if (unlikely(!si->cluster_nr--)) {
192 		if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
193 			si->cluster_nr = SWAPFILE_CLUSTER - 1;
194 			goto checks;
195 		}
196 		if (si->flags & SWP_DISCARDABLE) {
197 			/*
198 			 * Start range check on racing allocations, in case
199 			 * they overlap the cluster we eventually decide on
200 			 * (we scan without swap_lock to allow preemption).
201 			 * It's hardly conceivable that cluster_nr could be
202 			 * wrapped during our scan, but don't depend on it.
203 			 */
204 			if (si->lowest_alloc)
205 				goto checks;
206 			si->lowest_alloc = si->max;
207 			si->highest_alloc = 0;
208 		}
209 		spin_unlock(&swap_lock);
210 
211 		/*
212 		 * If seek is expensive, start searching for new cluster from
213 		 * start of partition, to minimize the span of allocated swap.
214 		 * But if seek is cheap, search from our current position, so
215 		 * that swap is allocated from all over the partition: if the
216 		 * Flash Translation Layer only remaps within limited zones,
217 		 * we don't want to wear out the first zone too quickly.
218 		 */
219 		if (!(si->flags & SWP_SOLIDSTATE))
220 			scan_base = offset = si->lowest_bit;
221 		last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
222 
223 		/* Locate the first empty (unaligned) cluster */
224 		for (; last_in_cluster <= si->highest_bit; offset++) {
225 			if (si->swap_map[offset])
226 				last_in_cluster = offset + SWAPFILE_CLUSTER;
227 			else if (offset == last_in_cluster) {
228 				spin_lock(&swap_lock);
229 				offset -= SWAPFILE_CLUSTER - 1;
230 				si->cluster_next = offset;
231 				si->cluster_nr = SWAPFILE_CLUSTER - 1;
232 				found_free_cluster = 1;
233 				goto checks;
234 			}
235 			if (unlikely(--latency_ration < 0)) {
236 				cond_resched();
237 				latency_ration = LATENCY_LIMIT;
238 			}
239 		}
240 
241 		offset = si->lowest_bit;
242 		last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
243 
244 		/* Locate the first empty (unaligned) cluster */
245 		for (; last_in_cluster < scan_base; offset++) {
246 			if (si->swap_map[offset])
247 				last_in_cluster = offset + SWAPFILE_CLUSTER;
248 			else if (offset == last_in_cluster) {
249 				spin_lock(&swap_lock);
250 				offset -= SWAPFILE_CLUSTER - 1;
251 				si->cluster_next = offset;
252 				si->cluster_nr = SWAPFILE_CLUSTER - 1;
253 				found_free_cluster = 1;
254 				goto checks;
255 			}
256 			if (unlikely(--latency_ration < 0)) {
257 				cond_resched();
258 				latency_ration = LATENCY_LIMIT;
259 			}
260 		}
261 
262 		offset = scan_base;
263 		spin_lock(&swap_lock);
264 		si->cluster_nr = SWAPFILE_CLUSTER - 1;
265 		si->lowest_alloc = 0;
266 	}
267 
268 checks:
269 	if (!(si->flags & SWP_WRITEOK))
270 		goto no_page;
271 	if (!si->highest_bit)
272 		goto no_page;
273 	if (offset > si->highest_bit)
274 		scan_base = offset = si->lowest_bit;
275 	if (si->swap_map[offset])
276 		goto scan;
277 
278 	if (offset == si->lowest_bit)
279 		si->lowest_bit++;
280 	if (offset == si->highest_bit)
281 		si->highest_bit--;
282 	si->inuse_pages++;
283 	if (si->inuse_pages == si->pages) {
284 		si->lowest_bit = si->max;
285 		si->highest_bit = 0;
286 	}
287 	si->swap_map[offset] = 1;
288 	si->cluster_next = offset + 1;
289 	si->flags -= SWP_SCANNING;
290 
291 	if (si->lowest_alloc) {
292 		/*
293 		 * Only set when SWP_DISCARDABLE, and there's a scan
294 		 * for a free cluster in progress or just completed.
295 		 */
296 		if (found_free_cluster) {
297 			/*
298 			 * To optimize wear-levelling, discard the
299 			 * old data of the cluster, taking care not to
300 			 * discard any of its pages that have already
301 			 * been allocated by racing tasks (offset has
302 			 * already stepped over any at the beginning).
303 			 */
304 			if (offset < si->highest_alloc &&
305 			    si->lowest_alloc <= last_in_cluster)
306 				last_in_cluster = si->lowest_alloc - 1;
307 			si->flags |= SWP_DISCARDING;
308 			spin_unlock(&swap_lock);
309 
310 			if (offset < last_in_cluster)
311 				discard_swap_cluster(si, offset,
312 					last_in_cluster - offset + 1);
313 
314 			spin_lock(&swap_lock);
315 			si->lowest_alloc = 0;
316 			si->flags &= ~SWP_DISCARDING;
317 
318 			smp_mb();	/* wake_up_bit advises this */
319 			wake_up_bit(&si->flags, ilog2(SWP_DISCARDING));
320 
321 		} else if (si->flags & SWP_DISCARDING) {
322 			/*
323 			 * Delay using pages allocated by racing tasks
324 			 * until the whole discard has been issued. We
325 			 * could defer that delay until swap_writepage,
326 			 * but it's easier to keep this self-contained.
327 			 */
328 			spin_unlock(&swap_lock);
329 			wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
330 				wait_for_discard, TASK_UNINTERRUPTIBLE);
331 			spin_lock(&swap_lock);
332 		} else {
333 			/*
334 			 * Note pages allocated by racing tasks while
335 			 * scan for a free cluster is in progress, so
336 			 * that its final discard can exclude them.
337 			 */
338 			if (offset < si->lowest_alloc)
339 				si->lowest_alloc = offset;
340 			if (offset > si->highest_alloc)
341 				si->highest_alloc = offset;
342 		}
343 	}
344 	return offset;
345 
346 scan:
347 	spin_unlock(&swap_lock);
348 	while (++offset <= si->highest_bit) {
349 		if (!si->swap_map[offset]) {
350 			spin_lock(&swap_lock);
351 			goto checks;
352 		}
353 		if (unlikely(--latency_ration < 0)) {
354 			cond_resched();
355 			latency_ration = LATENCY_LIMIT;
356 		}
357 	}
358 	offset = si->lowest_bit;
359 	while (++offset < scan_base) {
360 		if (!si->swap_map[offset]) {
361 			spin_lock(&swap_lock);
362 			goto checks;
363 		}
364 		if (unlikely(--latency_ration < 0)) {
365 			cond_resched();
366 			latency_ration = LATENCY_LIMIT;
367 		}
368 	}
369 	spin_lock(&swap_lock);
370 
371 no_page:
372 	si->flags -= SWP_SCANNING;
373 	return 0;
374 }
375 
376 swp_entry_t get_swap_page(void)
377 {
378 	struct swap_info_struct *si;
379 	pgoff_t offset;
380 	int type, next;
381 	int wrapped = 0;
382 
383 	spin_lock(&swap_lock);
384 	if (nr_swap_pages <= 0)
385 		goto noswap;
386 	nr_swap_pages--;
387 
388 	for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
389 		si = swap_info + type;
390 		next = si->next;
391 		if (next < 0 ||
392 		    (!wrapped && si->prio != swap_info[next].prio)) {
393 			next = swap_list.head;
394 			wrapped++;
395 		}
396 
397 		if (!si->highest_bit)
398 			continue;
399 		if (!(si->flags & SWP_WRITEOK))
400 			continue;
401 
402 		swap_list.next = next;
403 		offset = scan_swap_map(si);
404 		if (offset) {
405 			spin_unlock(&swap_lock);
406 			return swp_entry(type, offset);
407 		}
408 		next = swap_list.next;
409 	}
410 
411 	nr_swap_pages++;
412 noswap:
413 	spin_unlock(&swap_lock);
414 	return (swp_entry_t) {0};
415 }
416 
417 swp_entry_t get_swap_page_of_type(int type)
418 {
419 	struct swap_info_struct *si;
420 	pgoff_t offset;
421 
422 	spin_lock(&swap_lock);
423 	si = swap_info + type;
424 	if (si->flags & SWP_WRITEOK) {
425 		nr_swap_pages--;
426 		offset = scan_swap_map(si);
427 		if (offset) {
428 			spin_unlock(&swap_lock);
429 			return swp_entry(type, offset);
430 		}
431 		nr_swap_pages++;
432 	}
433 	spin_unlock(&swap_lock);
434 	return (swp_entry_t) {0};
435 }
436 
437 static struct swap_info_struct * swap_info_get(swp_entry_t entry)
438 {
439 	struct swap_info_struct * p;
440 	unsigned long offset, type;
441 
442 	if (!entry.val)
443 		goto out;
444 	type = swp_type(entry);
445 	if (type >= nr_swapfiles)
446 		goto bad_nofile;
447 	p = & swap_info[type];
448 	if (!(p->flags & SWP_USED))
449 		goto bad_device;
450 	offset = swp_offset(entry);
451 	if (offset >= p->max)
452 		goto bad_offset;
453 	if (!p->swap_map[offset])
454 		goto bad_free;
455 	spin_lock(&swap_lock);
456 	return p;
457 
458 bad_free:
459 	printk(KERN_ERR "swap_free: %s%08lx\n", Unused_offset, entry.val);
460 	goto out;
461 bad_offset:
462 	printk(KERN_ERR "swap_free: %s%08lx\n", Bad_offset, entry.val);
463 	goto out;
464 bad_device:
465 	printk(KERN_ERR "swap_free: %s%08lx\n", Unused_file, entry.val);
466 	goto out;
467 bad_nofile:
468 	printk(KERN_ERR "swap_free: %s%08lx\n", Bad_file, entry.val);
469 out:
470 	return NULL;
471 }
472 
473 static int swap_entry_free(struct swap_info_struct *p, unsigned long offset)
474 {
475 	int count = p->swap_map[offset];
476 
477 	if (count < SWAP_MAP_MAX) {
478 		count--;
479 		p->swap_map[offset] = count;
480 		if (!count) {
481 			if (offset < p->lowest_bit)
482 				p->lowest_bit = offset;
483 			if (offset > p->highest_bit)
484 				p->highest_bit = offset;
485 			if (p->prio > swap_info[swap_list.next].prio)
486 				swap_list.next = p - swap_info;
487 			nr_swap_pages++;
488 			p->inuse_pages--;
489 		}
490 	}
491 	return count;
492 }
493 
494 /*
495  * Caller has made sure that the swapdevice corresponding to entry
496  * is still around or has not been recycled.
497  */
498 void swap_free(swp_entry_t entry)
499 {
500 	struct swap_info_struct * p;
501 
502 	p = swap_info_get(entry);
503 	if (p) {
504 		swap_entry_free(p, swp_offset(entry));
505 		spin_unlock(&swap_lock);
506 	}
507 }
508 
509 /*
510  * How many references to page are currently swapped out?
511  */
512 static inline int page_swapcount(struct page *page)
513 {
514 	int count = 0;
515 	struct swap_info_struct *p;
516 	swp_entry_t entry;
517 
518 	entry.val = page_private(page);
519 	p = swap_info_get(entry);
520 	if (p) {
521 		/* Subtract the 1 for the swap cache itself */
522 		count = p->swap_map[swp_offset(entry)] - 1;
523 		spin_unlock(&swap_lock);
524 	}
525 	return count;
526 }
527 
528 /*
529  * We can write to an anon page without COW if there are no other references
530  * to it.  And as a side-effect, free up its swap: because the old content
531  * on disk will never be read, and seeking back there to write new content
532  * later would only waste time away from clustering.
533  */
534 int reuse_swap_page(struct page *page)
535 {
536 	int count;
537 
538 	VM_BUG_ON(!PageLocked(page));
539 	count = page_mapcount(page);
540 	if (count <= 1 && PageSwapCache(page)) {
541 		count += page_swapcount(page);
542 		if (count == 1 && !PageWriteback(page)) {
543 			delete_from_swap_cache(page);
544 			SetPageDirty(page);
545 		}
546 	}
547 	return count == 1;
548 }
549 
550 /*
551  * If swap is getting full, or if there are no more mappings of this page,
552  * then try_to_free_swap is called to free its swap space.
553  */
554 int try_to_free_swap(struct page *page)
555 {
556 	VM_BUG_ON(!PageLocked(page));
557 
558 	if (!PageSwapCache(page))
559 		return 0;
560 	if (PageWriteback(page))
561 		return 0;
562 	if (page_swapcount(page))
563 		return 0;
564 
565 	delete_from_swap_cache(page);
566 	SetPageDirty(page);
567 	return 1;
568 }
569 
570 /*
571  * Free the swap entry like above, but also try to
572  * free the page cache entry if it is the last user.
573  */
574 void free_swap_and_cache(swp_entry_t entry)
575 {
576 	struct swap_info_struct * p;
577 	struct page *page = NULL;
578 
579 	if (is_migration_entry(entry))
580 		return;
581 
582 	p = swap_info_get(entry);
583 	if (p) {
584 		if (swap_entry_free(p, swp_offset(entry)) == 1) {
585 			page = find_get_page(&swapper_space, entry.val);
586 			if (page && !trylock_page(page)) {
587 				page_cache_release(page);
588 				page = NULL;
589 			}
590 		}
591 		spin_unlock(&swap_lock);
592 	}
593 	if (page) {
594 		/*
595 		 * Not mapped elsewhere, or swap space full? Free it!
596 		 * Also recheck PageSwapCache now page is locked (above).
597 		 */
598 		if (PageSwapCache(page) && !PageWriteback(page) &&
599 				(!page_mapped(page) || vm_swap_full())) {
600 			delete_from_swap_cache(page);
601 			SetPageDirty(page);
602 		}
603 		unlock_page(page);
604 		page_cache_release(page);
605 	}
606 }
607 
608 #ifdef CONFIG_HIBERNATION
609 /*
610  * Find the swap type that corresponds to given device (if any).
611  *
612  * @offset - number of the PAGE_SIZE-sized block of the device, starting
613  * from 0, in which the swap header is expected to be located.
614  *
615  * This is needed for the suspend to disk (aka swsusp).
616  */
617 int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
618 {
619 	struct block_device *bdev = NULL;
620 	int i;
621 
622 	if (device)
623 		bdev = bdget(device);
624 
625 	spin_lock(&swap_lock);
626 	for (i = 0; i < nr_swapfiles; i++) {
627 		struct swap_info_struct *sis = swap_info + i;
628 
629 		if (!(sis->flags & SWP_WRITEOK))
630 			continue;
631 
632 		if (!bdev) {
633 			if (bdev_p)
634 				*bdev_p = sis->bdev;
635 
636 			spin_unlock(&swap_lock);
637 			return i;
638 		}
639 		if (bdev == sis->bdev) {
640 			struct swap_extent *se;
641 
642 			se = list_entry(sis->extent_list.next,
643 					struct swap_extent, list);
644 			if (se->start_block == offset) {
645 				if (bdev_p)
646 					*bdev_p = sis->bdev;
647 
648 				spin_unlock(&swap_lock);
649 				bdput(bdev);
650 				return i;
651 			}
652 		}
653 	}
654 	spin_unlock(&swap_lock);
655 	if (bdev)
656 		bdput(bdev);
657 
658 	return -ENODEV;
659 }
660 
661 /*
662  * Return either the total number of swap pages of given type, or the number
663  * of free pages of that type (depending on @free)
664  *
665  * This is needed for software suspend
666  */
667 unsigned int count_swap_pages(int type, int free)
668 {
669 	unsigned int n = 0;
670 
671 	if (type < nr_swapfiles) {
672 		spin_lock(&swap_lock);
673 		if (swap_info[type].flags & SWP_WRITEOK) {
674 			n = swap_info[type].pages;
675 			if (free)
676 				n -= swap_info[type].inuse_pages;
677 		}
678 		spin_unlock(&swap_lock);
679 	}
680 	return n;
681 }
682 #endif
683 
684 /*
685  * No need to decide whether this PTE shares the swap entry with others,
686  * just let do_wp_page work it out if a write is requested later - to
687  * force COW, vm_page_prot omits write permission from any private vma.
688  */
689 static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
690 		unsigned long addr, swp_entry_t entry, struct page *page)
691 {
692 	spinlock_t *ptl;
693 	pte_t *pte;
694 	int ret = 1;
695 
696 	if (mem_cgroup_charge(page, vma->vm_mm, GFP_KERNEL))
697 		ret = -ENOMEM;
698 
699 	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
700 	if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) {
701 		if (ret > 0)
702 			mem_cgroup_uncharge_page(page);
703 		ret = 0;
704 		goto out;
705 	}
706 
707 	inc_mm_counter(vma->vm_mm, anon_rss);
708 	get_page(page);
709 	set_pte_at(vma->vm_mm, addr, pte,
710 		   pte_mkold(mk_pte(page, vma->vm_page_prot)));
711 	page_add_anon_rmap(page, vma, addr);
712 	swap_free(entry);
713 	/*
714 	 * Move the page to the active list so it is not
715 	 * immediately swapped out again after swapon.
716 	 */
717 	activate_page(page);
718 out:
719 	pte_unmap_unlock(pte, ptl);
720 	return ret;
721 }
722 
723 static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
724 				unsigned long addr, unsigned long end,
725 				swp_entry_t entry, struct page *page)
726 {
727 	pte_t swp_pte = swp_entry_to_pte(entry);
728 	pte_t *pte;
729 	int ret = 0;
730 
731 	/*
732 	 * We don't actually need pte lock while scanning for swp_pte: since
733 	 * we hold page lock and mmap_sem, swp_pte cannot be inserted into the
734 	 * page table while we're scanning; though it could get zapped, and on
735 	 * some architectures (e.g. x86_32 with PAE) we might catch a glimpse
736 	 * of unmatched parts which look like swp_pte, so unuse_pte must
737 	 * recheck under pte lock.  Scanning without pte lock lets it be
738 	 * preemptible whenever CONFIG_PREEMPT but not CONFIG_HIGHPTE.
739 	 */
740 	pte = pte_offset_map(pmd, addr);
741 	do {
742 		/*
743 		 * swapoff spends a _lot_ of time in this loop!
744 		 * Test inline before going to call unuse_pte.
745 		 */
746 		if (unlikely(pte_same(*pte, swp_pte))) {
747 			pte_unmap(pte);
748 			ret = unuse_pte(vma, pmd, addr, entry, page);
749 			if (ret)
750 				goto out;
751 			pte = pte_offset_map(pmd, addr);
752 		}
753 	} while (pte++, addr += PAGE_SIZE, addr != end);
754 	pte_unmap(pte - 1);
755 out:
756 	return ret;
757 }
758 
759 static inline int unuse_pmd_range(struct vm_area_struct *vma, pud_t *pud,
760 				unsigned long addr, unsigned long end,
761 				swp_entry_t entry, struct page *page)
762 {
763 	pmd_t *pmd;
764 	unsigned long next;
765 	int ret;
766 
767 	pmd = pmd_offset(pud, addr);
768 	do {
769 		next = pmd_addr_end(addr, end);
770 		if (pmd_none_or_clear_bad(pmd))
771 			continue;
772 		ret = unuse_pte_range(vma, pmd, addr, next, entry, page);
773 		if (ret)
774 			return ret;
775 	} while (pmd++, addr = next, addr != end);
776 	return 0;
777 }
778 
779 static inline int unuse_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
780 				unsigned long addr, unsigned long end,
781 				swp_entry_t entry, struct page *page)
782 {
783 	pud_t *pud;
784 	unsigned long next;
785 	int ret;
786 
787 	pud = pud_offset(pgd, addr);
788 	do {
789 		next = pud_addr_end(addr, end);
790 		if (pud_none_or_clear_bad(pud))
791 			continue;
792 		ret = unuse_pmd_range(vma, pud, addr, next, entry, page);
793 		if (ret)
794 			return ret;
795 	} while (pud++, addr = next, addr != end);
796 	return 0;
797 }
798 
799 static int unuse_vma(struct vm_area_struct *vma,
800 				swp_entry_t entry, struct page *page)
801 {
802 	pgd_t *pgd;
803 	unsigned long addr, end, next;
804 	int ret;
805 
806 	if (page->mapping) {
807 		addr = page_address_in_vma(page, vma);
808 		if (addr == -EFAULT)
809 			return 0;
810 		else
811 			end = addr + PAGE_SIZE;
812 	} else {
813 		addr = vma->vm_start;
814 		end = vma->vm_end;
815 	}
816 
817 	pgd = pgd_offset(vma->vm_mm, addr);
818 	do {
819 		next = pgd_addr_end(addr, end);
820 		if (pgd_none_or_clear_bad(pgd))
821 			continue;
822 		ret = unuse_pud_range(vma, pgd, addr, next, entry, page);
823 		if (ret)
824 			return ret;
825 	} while (pgd++, addr = next, addr != end);
826 	return 0;
827 }
828 
829 static int unuse_mm(struct mm_struct *mm,
830 				swp_entry_t entry, struct page *page)
831 {
832 	struct vm_area_struct *vma;
833 	int ret = 0;
834 
835 	if (!down_read_trylock(&mm->mmap_sem)) {
836 		/*
837 		 * Activate page so shrink_inactive_list is unlikely to unmap
838 		 * its ptes while lock is dropped, so swapoff can make progress.
839 		 */
840 		activate_page(page);
841 		unlock_page(page);
842 		down_read(&mm->mmap_sem);
843 		lock_page(page);
844 	}
845 	for (vma = mm->mmap; vma; vma = vma->vm_next) {
846 		if (vma->anon_vma && (ret = unuse_vma(vma, entry, page)))
847 			break;
848 	}
849 	up_read(&mm->mmap_sem);
850 	return (ret < 0)? ret: 0;
851 }
852 
853 /*
854  * Scan swap_map from current position to next entry still in use.
855  * Recycle to start on reaching the end, returning 0 when empty.
856  */
857 static unsigned int find_next_to_unuse(struct swap_info_struct *si,
858 					unsigned int prev)
859 {
860 	unsigned int max = si->max;
861 	unsigned int i = prev;
862 	int count;
863 
864 	/*
865 	 * No need for swap_lock here: we're just looking
866 	 * for whether an entry is in use, not modifying it; false
867 	 * hits are okay, and sys_swapoff() has already prevented new
868 	 * allocations from this area (while holding swap_lock).
869 	 */
870 	for (;;) {
871 		if (++i >= max) {
872 			if (!prev) {
873 				i = 0;
874 				break;
875 			}
876 			/*
877 			 * No entries in use at top of swap_map,
878 			 * loop back to start and recheck there.
879 			 */
880 			max = prev + 1;
881 			prev = 0;
882 			i = 1;
883 		}
884 		count = si->swap_map[i];
885 		if (count && count != SWAP_MAP_BAD)
886 			break;
887 	}
888 	return i;
889 }
890 
891 /*
892  * We completely avoid races by reading each swap page in advance,
893  * and then search for the process using it.  All the necessary
894  * page table adjustments can then be made atomically.
895  */
896 static int try_to_unuse(unsigned int type)
897 {
898 	struct swap_info_struct * si = &swap_info[type];
899 	struct mm_struct *start_mm;
900 	unsigned short *swap_map;
901 	unsigned short swcount;
902 	struct page *page;
903 	swp_entry_t entry;
904 	unsigned int i = 0;
905 	int retval = 0;
906 	int reset_overflow = 0;
907 	int shmem;
908 
909 	/*
910 	 * When searching mms for an entry, a good strategy is to
911 	 * start at the first mm we freed the previous entry from
912 	 * (though actually we don't notice whether we or coincidence
913 	 * freed the entry).  Initialize this start_mm with a hold.
914 	 *
915 	 * A simpler strategy would be to start at the last mm we
916 	 * freed the previous entry from; but that would take less
917 	 * advantage of mmlist ordering, which clusters forked mms
918 	 * together, child after parent.  If we race with dup_mmap(), we
919 	 * prefer to resolve parent before child, lest we miss entries
920 	 * duplicated after we scanned child: using last mm would invert
921 	 * that.  Though it's only a serious concern when an overflowed
922 	 * swap count is reset from SWAP_MAP_MAX, preventing a rescan.
923 	 */
924 	start_mm = &init_mm;
925 	atomic_inc(&init_mm.mm_users);
926 
927 	/*
928 	 * Keep on scanning until all entries have gone.  Usually,
929 	 * one pass through swap_map is enough, but not necessarily:
930 	 * there are races when an instance of an entry might be missed.
931 	 */
932 	while ((i = find_next_to_unuse(si, i)) != 0) {
933 		if (signal_pending(current)) {
934 			retval = -EINTR;
935 			break;
936 		}
937 
938 		/*
939 		 * Get a page for the entry, using the existing swap
940 		 * cache page if there is one.  Otherwise, get a clean
941 		 * page and read the swap into it.
942 		 */
943 		swap_map = &si->swap_map[i];
944 		entry = swp_entry(type, i);
945 		page = read_swap_cache_async(entry,
946 					GFP_HIGHUSER_MOVABLE, NULL, 0);
947 		if (!page) {
948 			/*
949 			 * Either swap_duplicate() failed because entry
950 			 * has been freed independently, and will not be
951 			 * reused since sys_swapoff() already disabled
952 			 * allocation from here, or alloc_page() failed.
953 			 */
954 			if (!*swap_map)
955 				continue;
956 			retval = -ENOMEM;
957 			break;
958 		}
959 
960 		/*
961 		 * Don't hold on to start_mm if it looks like exiting.
962 		 */
963 		if (atomic_read(&start_mm->mm_users) == 1) {
964 			mmput(start_mm);
965 			start_mm = &init_mm;
966 			atomic_inc(&init_mm.mm_users);
967 		}
968 
969 		/*
970 		 * Wait for and lock page.  When do_swap_page races with
971 		 * try_to_unuse, do_swap_page can handle the fault much
972 		 * faster than try_to_unuse can locate the entry.  This
973 		 * apparently redundant "wait_on_page_locked" lets try_to_unuse
974 		 * defer to do_swap_page in such a case - in some tests,
975 		 * do_swap_page and try_to_unuse repeatedly compete.
976 		 */
977 		wait_on_page_locked(page);
978 		wait_on_page_writeback(page);
979 		lock_page(page);
980 		wait_on_page_writeback(page);
981 
982 		/*
983 		 * Remove all references to entry.
984 		 * Whenever we reach init_mm, there's no address space
985 		 * to search, but use it as a reminder to search shmem.
986 		 */
987 		shmem = 0;
988 		swcount = *swap_map;
989 		if (swcount > 1) {
990 			if (start_mm == &init_mm)
991 				shmem = shmem_unuse(entry, page);
992 			else
993 				retval = unuse_mm(start_mm, entry, page);
994 		}
995 		if (*swap_map > 1) {
996 			int set_start_mm = (*swap_map >= swcount);
997 			struct list_head *p = &start_mm->mmlist;
998 			struct mm_struct *new_start_mm = start_mm;
999 			struct mm_struct *prev_mm = start_mm;
1000 			struct mm_struct *mm;
1001 
1002 			atomic_inc(&new_start_mm->mm_users);
1003 			atomic_inc(&prev_mm->mm_users);
1004 			spin_lock(&mmlist_lock);
1005 			while (*swap_map > 1 && !retval && !shmem &&
1006 					(p = p->next) != &start_mm->mmlist) {
1007 				mm = list_entry(p, struct mm_struct, mmlist);
1008 				if (!atomic_inc_not_zero(&mm->mm_users))
1009 					continue;
1010 				spin_unlock(&mmlist_lock);
1011 				mmput(prev_mm);
1012 				prev_mm = mm;
1013 
1014 				cond_resched();
1015 
1016 				swcount = *swap_map;
1017 				if (swcount <= 1)
1018 					;
1019 				else if (mm == &init_mm) {
1020 					set_start_mm = 1;
1021 					shmem = shmem_unuse(entry, page);
1022 				} else
1023 					retval = unuse_mm(mm, entry, page);
1024 				if (set_start_mm && *swap_map < swcount) {
1025 					mmput(new_start_mm);
1026 					atomic_inc(&mm->mm_users);
1027 					new_start_mm = mm;
1028 					set_start_mm = 0;
1029 				}
1030 				spin_lock(&mmlist_lock);
1031 			}
1032 			spin_unlock(&mmlist_lock);
1033 			mmput(prev_mm);
1034 			mmput(start_mm);
1035 			start_mm = new_start_mm;
1036 		}
1037 		if (shmem) {
1038 			/* page has already been unlocked and released */
1039 			if (shmem > 0)
1040 				continue;
1041 			retval = shmem;
1042 			break;
1043 		}
1044 		if (retval) {
1045 			unlock_page(page);
1046 			page_cache_release(page);
1047 			break;
1048 		}
1049 
1050 		/*
1051 		 * How could swap count reach 0x7fff when the maximum
1052 		 * pid is 0x7fff, and there's no way to repeat a swap
1053 		 * page within an mm (except in shmem, where it's the
1054 		 * shared object which takes the reference count)?
1055 		 * We believe SWAP_MAP_MAX cannot occur in Linux 2.4.
1056 		 *
1057 		 * If that's wrong, then we should worry more about
1058 		 * exit_mmap() and do_munmap() cases described above:
1059 		 * we might be resetting SWAP_MAP_MAX too early here.
1060 		 * We know "Undead"s can happen, they're okay, so don't
1061 		 * report them; but do report if we reset SWAP_MAP_MAX.
1062 		 */
1063 		if (*swap_map == SWAP_MAP_MAX) {
1064 			spin_lock(&swap_lock);
1065 			*swap_map = 1;
1066 			spin_unlock(&swap_lock);
1067 			reset_overflow = 1;
1068 		}
1069 
1070 		/*
1071 		 * If a reference remains (rare), we would like to leave
1072 		 * the page in the swap cache; but try_to_unmap could
1073 		 * then re-duplicate the entry once we drop page lock,
1074 		 * so we might loop indefinitely; also, that page could
1075 		 * not be swapped out to other storage meanwhile.  So:
1076 		 * delete from cache even if there's another reference,
1077 		 * after ensuring that the data has been saved to disk -
1078 		 * since if the reference remains (rarer), it will be
1079 		 * read from disk into another page.  Splitting into two
1080 		 * pages would be incorrect if swap supported "shared
1081 		 * private" pages, but they are handled by tmpfs files.
1082 		 */
1083 		if ((*swap_map > 1) && PageDirty(page) && PageSwapCache(page)) {
1084 			struct writeback_control wbc = {
1085 				.sync_mode = WB_SYNC_NONE,
1086 			};
1087 
1088 			swap_writepage(page, &wbc);
1089 			lock_page(page);
1090 			wait_on_page_writeback(page);
1091 		}
1092 
1093 		/*
1094 		 * It is conceivable that a racing task removed this page from
1095 		 * swap cache just before we acquired the page lock at the top,
1096 		 * or while we dropped it in unuse_mm().  The page might even
1097 		 * be back in swap cache on another swap area: that we must not
1098 		 * delete, since it may not have been written out to swap yet.
1099 		 */
1100 		if (PageSwapCache(page) &&
1101 		    likely(page_private(page) == entry.val))
1102 			delete_from_swap_cache(page);
1103 
1104 		/*
1105 		 * So we could skip searching mms once swap count went
1106 		 * to 1, we did not mark any present ptes as dirty: must
1107 		 * mark page dirty so shrink_page_list will preserve it.
1108 		 */
1109 		SetPageDirty(page);
1110 		unlock_page(page);
1111 		page_cache_release(page);
1112 
1113 		/*
1114 		 * Make sure that we aren't completely killing
1115 		 * interactive performance.
1116 		 */
1117 		cond_resched();
1118 	}
1119 
1120 	mmput(start_mm);
1121 	if (reset_overflow) {
1122 		printk(KERN_WARNING "swapoff: cleared swap entry overflow\n");
1123 		swap_overflow = 0;
1124 	}
1125 	return retval;
1126 }
1127 
1128 /*
1129  * After a successful try_to_unuse, if no swap is now in use, we know
1130  * we can empty the mmlist.  swap_lock must be held on entry and exit.
1131  * Note that mmlist_lock nests inside swap_lock, and an mm must be
1132  * added to the mmlist just after page_duplicate - before would be racy.
1133  */
1134 static void drain_mmlist(void)
1135 {
1136 	struct list_head *p, *next;
1137 	unsigned int i;
1138 
1139 	for (i = 0; i < nr_swapfiles; i++)
1140 		if (swap_info[i].inuse_pages)
1141 			return;
1142 	spin_lock(&mmlist_lock);
1143 	list_for_each_safe(p, next, &init_mm.mmlist)
1144 		list_del_init(p);
1145 	spin_unlock(&mmlist_lock);
1146 }
1147 
1148 /*
1149  * Use this swapdev's extent info to locate the (PAGE_SIZE) block which
1150  * corresponds to page offset `offset'.
1151  */
1152 sector_t map_swap_page(struct swap_info_struct *sis, pgoff_t offset)
1153 {
1154 	struct swap_extent *se = sis->curr_swap_extent;
1155 	struct swap_extent *start_se = se;
1156 
1157 	for ( ; ; ) {
1158 		struct list_head *lh;
1159 
1160 		if (se->start_page <= offset &&
1161 				offset < (se->start_page + se->nr_pages)) {
1162 			return se->start_block + (offset - se->start_page);
1163 		}
1164 		lh = se->list.next;
1165 		if (lh == &sis->extent_list)
1166 			lh = lh->next;
1167 		se = list_entry(lh, struct swap_extent, list);
1168 		sis->curr_swap_extent = se;
1169 		BUG_ON(se == start_se);		/* It *must* be present */
1170 	}
1171 }
1172 
1173 #ifdef CONFIG_HIBERNATION
1174 /*
1175  * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
1176  * corresponding to given index in swap_info (swap type).
1177  */
1178 sector_t swapdev_block(int swap_type, pgoff_t offset)
1179 {
1180 	struct swap_info_struct *sis;
1181 
1182 	if (swap_type >= nr_swapfiles)
1183 		return 0;
1184 
1185 	sis = swap_info + swap_type;
1186 	return (sis->flags & SWP_WRITEOK) ? map_swap_page(sis, offset) : 0;
1187 }
1188 #endif /* CONFIG_HIBERNATION */
1189 
1190 /*
1191  * Free all of a swapdev's extent information
1192  */
1193 static void destroy_swap_extents(struct swap_info_struct *sis)
1194 {
1195 	while (!list_empty(&sis->extent_list)) {
1196 		struct swap_extent *se;
1197 
1198 		se = list_entry(sis->extent_list.next,
1199 				struct swap_extent, list);
1200 		list_del(&se->list);
1201 		kfree(se);
1202 	}
1203 }
1204 
1205 /*
1206  * Add a block range (and the corresponding page range) into this swapdev's
1207  * extent list.  The extent list is kept sorted in page order.
1208  *
1209  * This function rather assumes that it is called in ascending page order.
1210  */
1211 static int
1212 add_swap_extent(struct swap_info_struct *sis, unsigned long start_page,
1213 		unsigned long nr_pages, sector_t start_block)
1214 {
1215 	struct swap_extent *se;
1216 	struct swap_extent *new_se;
1217 	struct list_head *lh;
1218 
1219 	lh = sis->extent_list.prev;	/* The highest page extent */
1220 	if (lh != &sis->extent_list) {
1221 		se = list_entry(lh, struct swap_extent, list);
1222 		BUG_ON(se->start_page + se->nr_pages != start_page);
1223 		if (se->start_block + se->nr_pages == start_block) {
1224 			/* Merge it */
1225 			se->nr_pages += nr_pages;
1226 			return 0;
1227 		}
1228 	}
1229 
1230 	/*
1231 	 * No merge.  Insert a new extent, preserving ordering.
1232 	 */
1233 	new_se = kmalloc(sizeof(*se), GFP_KERNEL);
1234 	if (new_se == NULL)
1235 		return -ENOMEM;
1236 	new_se->start_page = start_page;
1237 	new_se->nr_pages = nr_pages;
1238 	new_se->start_block = start_block;
1239 
1240 	list_add_tail(&new_se->list, &sis->extent_list);
1241 	return 1;
1242 }
1243 
1244 /*
1245  * A `swap extent' is a simple thing which maps a contiguous range of pages
1246  * onto a contiguous range of disk blocks.  An ordered list of swap extents
1247  * is built at swapon time and is then used at swap_writepage/swap_readpage
1248  * time for locating where on disk a page belongs.
1249  *
1250  * If the swapfile is an S_ISBLK block device, a single extent is installed.
1251  * This is done so that the main operating code can treat S_ISBLK and S_ISREG
1252  * swap files identically.
1253  *
1254  * Whether the swapdev is an S_ISREG file or an S_ISBLK blockdev, the swap
1255  * extent list operates in PAGE_SIZE disk blocks.  Both S_ISREG and S_ISBLK
1256  * swapfiles are handled *identically* after swapon time.
1257  *
1258  * For S_ISREG swapfiles, setup_swap_extents() will walk all the file's blocks
1259  * and will parse them into an ordered extent list, in PAGE_SIZE chunks.  If
1260  * some stray blocks are found which do not fall within the PAGE_SIZE alignment
1261  * requirements, they are simply tossed out - we will never use those blocks
1262  * for swapping.
1263  *
1264  * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon.  This
1265  * prevents root from shooting her foot off by ftruncating an in-use swapfile,
1266  * which will scribble on the fs.
1267  *
1268  * The amount of disk space which a single swap extent represents varies.
1269  * Typically it is in the 1-4 megabyte range.  So we can have hundreds of
1270  * extents in the list.  To avoid much list walking, we cache the previous
1271  * search location in `curr_swap_extent', and start new searches from there.
1272  * This is extremely effective.  The average number of iterations in
1273  * map_swap_page() has been measured at about 0.3 per page.  - akpm.
1274  */
1275 static int setup_swap_extents(struct swap_info_struct *sis, sector_t *span)
1276 {
1277 	struct inode *inode;
1278 	unsigned blocks_per_page;
1279 	unsigned long page_no;
1280 	unsigned blkbits;
1281 	sector_t probe_block;
1282 	sector_t last_block;
1283 	sector_t lowest_block = -1;
1284 	sector_t highest_block = 0;
1285 	int nr_extents = 0;
1286 	int ret;
1287 
1288 	inode = sis->swap_file->f_mapping->host;
1289 	if (S_ISBLK(inode->i_mode)) {
1290 		ret = add_swap_extent(sis, 0, sis->max, 0);
1291 		*span = sis->pages;
1292 		goto done;
1293 	}
1294 
1295 	blkbits = inode->i_blkbits;
1296 	blocks_per_page = PAGE_SIZE >> blkbits;
1297 
1298 	/*
1299 	 * Map all the blocks into the extent list.  This code doesn't try
1300 	 * to be very smart.
1301 	 */
1302 	probe_block = 0;
1303 	page_no = 0;
1304 	last_block = i_size_read(inode) >> blkbits;
1305 	while ((probe_block + blocks_per_page) <= last_block &&
1306 			page_no < sis->max) {
1307 		unsigned block_in_page;
1308 		sector_t first_block;
1309 
1310 		first_block = bmap(inode, probe_block);
1311 		if (first_block == 0)
1312 			goto bad_bmap;
1313 
1314 		/*
1315 		 * It must be PAGE_SIZE aligned on-disk
1316 		 */
1317 		if (first_block & (blocks_per_page - 1)) {
1318 			probe_block++;
1319 			goto reprobe;
1320 		}
1321 
1322 		for (block_in_page = 1; block_in_page < blocks_per_page;
1323 					block_in_page++) {
1324 			sector_t block;
1325 
1326 			block = bmap(inode, probe_block + block_in_page);
1327 			if (block == 0)
1328 				goto bad_bmap;
1329 			if (block != first_block + block_in_page) {
1330 				/* Discontiguity */
1331 				probe_block++;
1332 				goto reprobe;
1333 			}
1334 		}
1335 
1336 		first_block >>= (PAGE_SHIFT - blkbits);
1337 		if (page_no) {	/* exclude the header page */
1338 			if (first_block < lowest_block)
1339 				lowest_block = first_block;
1340 			if (first_block > highest_block)
1341 				highest_block = first_block;
1342 		}
1343 
1344 		/*
1345 		 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
1346 		 */
1347 		ret = add_swap_extent(sis, page_no, 1, first_block);
1348 		if (ret < 0)
1349 			goto out;
1350 		nr_extents += ret;
1351 		page_no++;
1352 		probe_block += blocks_per_page;
1353 reprobe:
1354 		continue;
1355 	}
1356 	ret = nr_extents;
1357 	*span = 1 + highest_block - lowest_block;
1358 	if (page_no == 0)
1359 		page_no = 1;	/* force Empty message */
1360 	sis->max = page_no;
1361 	sis->pages = page_no - 1;
1362 	sis->highest_bit = page_no - 1;
1363 done:
1364 	sis->curr_swap_extent = list_entry(sis->extent_list.prev,
1365 					struct swap_extent, list);
1366 	goto out;
1367 bad_bmap:
1368 	printk(KERN_ERR "swapon: swapfile has holes\n");
1369 	ret = -EINVAL;
1370 out:
1371 	return ret;
1372 }
1373 
1374 #if 0	/* We don't need this yet */
1375 #include <linux/backing-dev.h>
1376 int page_queue_congested(struct page *page)
1377 {
1378 	struct backing_dev_info *bdi;
1379 
1380 	VM_BUG_ON(!PageLocked(page));	/* It pins the swap_info_struct */
1381 
1382 	if (PageSwapCache(page)) {
1383 		swp_entry_t entry = { .val = page_private(page) };
1384 		struct swap_info_struct *sis;
1385 
1386 		sis = get_swap_info_struct(swp_type(entry));
1387 		bdi = sis->bdev->bd_inode->i_mapping->backing_dev_info;
1388 	} else
1389 		bdi = page->mapping->backing_dev_info;
1390 	return bdi_write_congested(bdi);
1391 }
1392 #endif
1393 
1394 asmlinkage long sys_swapoff(const char __user * specialfile)
1395 {
1396 	struct swap_info_struct * p = NULL;
1397 	unsigned short *swap_map;
1398 	struct file *swap_file, *victim;
1399 	struct address_space *mapping;
1400 	struct inode *inode;
1401 	char * pathname;
1402 	int i, type, prev;
1403 	int err;
1404 
1405 	if (!capable(CAP_SYS_ADMIN))
1406 		return -EPERM;
1407 
1408 	pathname = getname(specialfile);
1409 	err = PTR_ERR(pathname);
1410 	if (IS_ERR(pathname))
1411 		goto out;
1412 
1413 	victim = filp_open(pathname, O_RDWR|O_LARGEFILE, 0);
1414 	putname(pathname);
1415 	err = PTR_ERR(victim);
1416 	if (IS_ERR(victim))
1417 		goto out;
1418 
1419 	mapping = victim->f_mapping;
1420 	prev = -1;
1421 	spin_lock(&swap_lock);
1422 	for (type = swap_list.head; type >= 0; type = swap_info[type].next) {
1423 		p = swap_info + type;
1424 		if (p->flags & SWP_WRITEOK) {
1425 			if (p->swap_file->f_mapping == mapping)
1426 				break;
1427 		}
1428 		prev = type;
1429 	}
1430 	if (type < 0) {
1431 		err = -EINVAL;
1432 		spin_unlock(&swap_lock);
1433 		goto out_dput;
1434 	}
1435 	if (!security_vm_enough_memory(p->pages))
1436 		vm_unacct_memory(p->pages);
1437 	else {
1438 		err = -ENOMEM;
1439 		spin_unlock(&swap_lock);
1440 		goto out_dput;
1441 	}
1442 	if (prev < 0) {
1443 		swap_list.head = p->next;
1444 	} else {
1445 		swap_info[prev].next = p->next;
1446 	}
1447 	if (type == swap_list.next) {
1448 		/* just pick something that's safe... */
1449 		swap_list.next = swap_list.head;
1450 	}
1451 	if (p->prio < 0) {
1452 		for (i = p->next; i >= 0; i = swap_info[i].next)
1453 			swap_info[i].prio = p->prio--;
1454 		least_priority++;
1455 	}
1456 	nr_swap_pages -= p->pages;
1457 	total_swap_pages -= p->pages;
1458 	p->flags &= ~SWP_WRITEOK;
1459 	spin_unlock(&swap_lock);
1460 
1461 	current->flags |= PF_SWAPOFF;
1462 	err = try_to_unuse(type);
1463 	current->flags &= ~PF_SWAPOFF;
1464 
1465 	if (err) {
1466 		/* re-insert swap space back into swap_list */
1467 		spin_lock(&swap_lock);
1468 		if (p->prio < 0)
1469 			p->prio = --least_priority;
1470 		prev = -1;
1471 		for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1472 			if (p->prio >= swap_info[i].prio)
1473 				break;
1474 			prev = i;
1475 		}
1476 		p->next = i;
1477 		if (prev < 0)
1478 			swap_list.head = swap_list.next = p - swap_info;
1479 		else
1480 			swap_info[prev].next = p - swap_info;
1481 		nr_swap_pages += p->pages;
1482 		total_swap_pages += p->pages;
1483 		p->flags |= SWP_WRITEOK;
1484 		spin_unlock(&swap_lock);
1485 		goto out_dput;
1486 	}
1487 
1488 	/* wait for any unplug function to finish */
1489 	down_write(&swap_unplug_sem);
1490 	up_write(&swap_unplug_sem);
1491 
1492 	destroy_swap_extents(p);
1493 	mutex_lock(&swapon_mutex);
1494 	spin_lock(&swap_lock);
1495 	drain_mmlist();
1496 
1497 	/* wait for anyone still in scan_swap_map */
1498 	p->highest_bit = 0;		/* cuts scans short */
1499 	while (p->flags >= SWP_SCANNING) {
1500 		spin_unlock(&swap_lock);
1501 		schedule_timeout_uninterruptible(1);
1502 		spin_lock(&swap_lock);
1503 	}
1504 
1505 	swap_file = p->swap_file;
1506 	p->swap_file = NULL;
1507 	p->max = 0;
1508 	swap_map = p->swap_map;
1509 	p->swap_map = NULL;
1510 	p->flags = 0;
1511 	spin_unlock(&swap_lock);
1512 	mutex_unlock(&swapon_mutex);
1513 	vfree(swap_map);
1514 	inode = mapping->host;
1515 	if (S_ISBLK(inode->i_mode)) {
1516 		struct block_device *bdev = I_BDEV(inode);
1517 		set_blocksize(bdev, p->old_block_size);
1518 		bd_release(bdev);
1519 	} else {
1520 		mutex_lock(&inode->i_mutex);
1521 		inode->i_flags &= ~S_SWAPFILE;
1522 		mutex_unlock(&inode->i_mutex);
1523 	}
1524 	filp_close(swap_file, NULL);
1525 	err = 0;
1526 
1527 out_dput:
1528 	filp_close(victim, NULL);
1529 out:
1530 	return err;
1531 }
1532 
1533 #ifdef CONFIG_PROC_FS
1534 /* iterator */
1535 static void *swap_start(struct seq_file *swap, loff_t *pos)
1536 {
1537 	struct swap_info_struct *ptr = swap_info;
1538 	int i;
1539 	loff_t l = *pos;
1540 
1541 	mutex_lock(&swapon_mutex);
1542 
1543 	if (!l)
1544 		return SEQ_START_TOKEN;
1545 
1546 	for (i = 0; i < nr_swapfiles; i++, ptr++) {
1547 		if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1548 			continue;
1549 		if (!--l)
1550 			return ptr;
1551 	}
1552 
1553 	return NULL;
1554 }
1555 
1556 static void *swap_next(struct seq_file *swap, void *v, loff_t *pos)
1557 {
1558 	struct swap_info_struct *ptr;
1559 	struct swap_info_struct *endptr = swap_info + nr_swapfiles;
1560 
1561 	if (v == SEQ_START_TOKEN)
1562 		ptr = swap_info;
1563 	else {
1564 		ptr = v;
1565 		ptr++;
1566 	}
1567 
1568 	for (; ptr < endptr; ptr++) {
1569 		if (!(ptr->flags & SWP_USED) || !ptr->swap_map)
1570 			continue;
1571 		++*pos;
1572 		return ptr;
1573 	}
1574 
1575 	return NULL;
1576 }
1577 
1578 static void swap_stop(struct seq_file *swap, void *v)
1579 {
1580 	mutex_unlock(&swapon_mutex);
1581 }
1582 
1583 static int swap_show(struct seq_file *swap, void *v)
1584 {
1585 	struct swap_info_struct *ptr = v;
1586 	struct file *file;
1587 	int len;
1588 
1589 	if (ptr == SEQ_START_TOKEN) {
1590 		seq_puts(swap,"Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");
1591 		return 0;
1592 	}
1593 
1594 	file = ptr->swap_file;
1595 	len = seq_path(swap, &file->f_path, " \t\n\\");
1596 	seq_printf(swap, "%*s%s\t%u\t%u\t%d\n",
1597 			len < 40 ? 40 - len : 1, " ",
1598 			S_ISBLK(file->f_path.dentry->d_inode->i_mode) ?
1599 				"partition" : "file\t",
1600 			ptr->pages << (PAGE_SHIFT - 10),
1601 			ptr->inuse_pages << (PAGE_SHIFT - 10),
1602 			ptr->prio);
1603 	return 0;
1604 }
1605 
1606 static const struct seq_operations swaps_op = {
1607 	.start =	swap_start,
1608 	.next =		swap_next,
1609 	.stop =		swap_stop,
1610 	.show =		swap_show
1611 };
1612 
1613 static int swaps_open(struct inode *inode, struct file *file)
1614 {
1615 	return seq_open(file, &swaps_op);
1616 }
1617 
1618 static const struct file_operations proc_swaps_operations = {
1619 	.open		= swaps_open,
1620 	.read		= seq_read,
1621 	.llseek		= seq_lseek,
1622 	.release	= seq_release,
1623 };
1624 
1625 static int __init procswaps_init(void)
1626 {
1627 	proc_create("swaps", 0, NULL, &proc_swaps_operations);
1628 	return 0;
1629 }
1630 __initcall(procswaps_init);
1631 #endif /* CONFIG_PROC_FS */
1632 
1633 #ifdef MAX_SWAPFILES_CHECK
1634 static int __init max_swapfiles_check(void)
1635 {
1636 	MAX_SWAPFILES_CHECK();
1637 	return 0;
1638 }
1639 late_initcall(max_swapfiles_check);
1640 #endif
1641 
1642 /*
1643  * Written 01/25/92 by Simmule Turner, heavily changed by Linus.
1644  *
1645  * The swapon system call
1646  */
1647 asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
1648 {
1649 	struct swap_info_struct * p;
1650 	char *name = NULL;
1651 	struct block_device *bdev = NULL;
1652 	struct file *swap_file = NULL;
1653 	struct address_space *mapping;
1654 	unsigned int type;
1655 	int i, prev;
1656 	int error;
1657 	union swap_header *swap_header = NULL;
1658 	unsigned int nr_good_pages = 0;
1659 	int nr_extents = 0;
1660 	sector_t span;
1661 	unsigned long maxpages = 1;
1662 	unsigned long swapfilepages;
1663 	unsigned short *swap_map = NULL;
1664 	struct page *page = NULL;
1665 	struct inode *inode = NULL;
1666 	int did_down = 0;
1667 
1668 	if (!capable(CAP_SYS_ADMIN))
1669 		return -EPERM;
1670 	spin_lock(&swap_lock);
1671 	p = swap_info;
1672 	for (type = 0 ; type < nr_swapfiles ; type++,p++)
1673 		if (!(p->flags & SWP_USED))
1674 			break;
1675 	error = -EPERM;
1676 	if (type >= MAX_SWAPFILES) {
1677 		spin_unlock(&swap_lock);
1678 		goto out;
1679 	}
1680 	if (type >= nr_swapfiles)
1681 		nr_swapfiles = type+1;
1682 	memset(p, 0, sizeof(*p));
1683 	INIT_LIST_HEAD(&p->extent_list);
1684 	p->flags = SWP_USED;
1685 	p->next = -1;
1686 	spin_unlock(&swap_lock);
1687 	name = getname(specialfile);
1688 	error = PTR_ERR(name);
1689 	if (IS_ERR(name)) {
1690 		name = NULL;
1691 		goto bad_swap_2;
1692 	}
1693 	swap_file = filp_open(name, O_RDWR|O_LARGEFILE, 0);
1694 	error = PTR_ERR(swap_file);
1695 	if (IS_ERR(swap_file)) {
1696 		swap_file = NULL;
1697 		goto bad_swap_2;
1698 	}
1699 
1700 	p->swap_file = swap_file;
1701 	mapping = swap_file->f_mapping;
1702 	inode = mapping->host;
1703 
1704 	error = -EBUSY;
1705 	for (i = 0; i < nr_swapfiles; i++) {
1706 		struct swap_info_struct *q = &swap_info[i];
1707 
1708 		if (i == type || !q->swap_file)
1709 			continue;
1710 		if (mapping == q->swap_file->f_mapping)
1711 			goto bad_swap;
1712 	}
1713 
1714 	error = -EINVAL;
1715 	if (S_ISBLK(inode->i_mode)) {
1716 		bdev = I_BDEV(inode);
1717 		error = bd_claim(bdev, sys_swapon);
1718 		if (error < 0) {
1719 			bdev = NULL;
1720 			error = -EINVAL;
1721 			goto bad_swap;
1722 		}
1723 		p->old_block_size = block_size(bdev);
1724 		error = set_blocksize(bdev, PAGE_SIZE);
1725 		if (error < 0)
1726 			goto bad_swap;
1727 		p->bdev = bdev;
1728 	} else if (S_ISREG(inode->i_mode)) {
1729 		p->bdev = inode->i_sb->s_bdev;
1730 		mutex_lock(&inode->i_mutex);
1731 		did_down = 1;
1732 		if (IS_SWAPFILE(inode)) {
1733 			error = -EBUSY;
1734 			goto bad_swap;
1735 		}
1736 	} else {
1737 		goto bad_swap;
1738 	}
1739 
1740 	swapfilepages = i_size_read(inode) >> PAGE_SHIFT;
1741 
1742 	/*
1743 	 * Read the swap header.
1744 	 */
1745 	if (!mapping->a_ops->readpage) {
1746 		error = -EINVAL;
1747 		goto bad_swap;
1748 	}
1749 	page = read_mapping_page(mapping, 0, swap_file);
1750 	if (IS_ERR(page)) {
1751 		error = PTR_ERR(page);
1752 		goto bad_swap;
1753 	}
1754 	swap_header = kmap(page);
1755 
1756 	if (memcmp("SWAPSPACE2", swap_header->magic.magic, 10)) {
1757 		printk(KERN_ERR "Unable to find swap-space signature\n");
1758 		error = -EINVAL;
1759 		goto bad_swap;
1760 	}
1761 
1762 	/* swap partition endianess hack... */
1763 	if (swab32(swap_header->info.version) == 1) {
1764 		swab32s(&swap_header->info.version);
1765 		swab32s(&swap_header->info.last_page);
1766 		swab32s(&swap_header->info.nr_badpages);
1767 		for (i = 0; i < swap_header->info.nr_badpages; i++)
1768 			swab32s(&swap_header->info.badpages[i]);
1769 	}
1770 	/* Check the swap header's sub-version */
1771 	if (swap_header->info.version != 1) {
1772 		printk(KERN_WARNING
1773 		       "Unable to handle swap header version %d\n",
1774 		       swap_header->info.version);
1775 		error = -EINVAL;
1776 		goto bad_swap;
1777 	}
1778 
1779 	p->lowest_bit  = 1;
1780 	p->cluster_next = 1;
1781 
1782 	/*
1783 	 * Find out how many pages are allowed for a single swap
1784 	 * device. There are two limiting factors: 1) the number of
1785 	 * bits for the swap offset in the swp_entry_t type and
1786 	 * 2) the number of bits in the a swap pte as defined by
1787 	 * the different architectures. In order to find the
1788 	 * largest possible bit mask a swap entry with swap type 0
1789 	 * and swap offset ~0UL is created, encoded to a swap pte,
1790 	 * decoded to a swp_entry_t again and finally the swap
1791 	 * offset is extracted. This will mask all the bits from
1792 	 * the initial ~0UL mask that can't be encoded in either
1793 	 * the swp_entry_t or the architecture definition of a
1794 	 * swap pte.
1795 	 */
1796 	maxpages = swp_offset(pte_to_swp_entry(
1797 			swp_entry_to_pte(swp_entry(0, ~0UL)))) - 1;
1798 	if (maxpages > swap_header->info.last_page)
1799 		maxpages = swap_header->info.last_page;
1800 	p->highest_bit = maxpages - 1;
1801 
1802 	error = -EINVAL;
1803 	if (!maxpages)
1804 		goto bad_swap;
1805 	if (swapfilepages && maxpages > swapfilepages) {
1806 		printk(KERN_WARNING
1807 		       "Swap area shorter than signature indicates\n");
1808 		goto bad_swap;
1809 	}
1810 	if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
1811 		goto bad_swap;
1812 	if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
1813 		goto bad_swap;
1814 
1815 	/* OK, set up the swap map and apply the bad block list */
1816 	swap_map = vmalloc(maxpages * sizeof(short));
1817 	if (!swap_map) {
1818 		error = -ENOMEM;
1819 		goto bad_swap;
1820 	}
1821 
1822 	memset(swap_map, 0, maxpages * sizeof(short));
1823 	for (i = 0; i < swap_header->info.nr_badpages; i++) {
1824 		int page_nr = swap_header->info.badpages[i];
1825 		if (page_nr <= 0 || page_nr >= swap_header->info.last_page) {
1826 			error = -EINVAL;
1827 			goto bad_swap;
1828 		}
1829 		swap_map[page_nr] = SWAP_MAP_BAD;
1830 	}
1831 	nr_good_pages = swap_header->info.last_page -
1832 			swap_header->info.nr_badpages -
1833 			1 /* header page */;
1834 
1835 	if (nr_good_pages) {
1836 		swap_map[0] = SWAP_MAP_BAD;
1837 		p->max = maxpages;
1838 		p->pages = nr_good_pages;
1839 		nr_extents = setup_swap_extents(p, &span);
1840 		if (nr_extents < 0) {
1841 			error = nr_extents;
1842 			goto bad_swap;
1843 		}
1844 		nr_good_pages = p->pages;
1845 	}
1846 	if (!nr_good_pages) {
1847 		printk(KERN_WARNING "Empty swap-file\n");
1848 		error = -EINVAL;
1849 		goto bad_swap;
1850 	}
1851 
1852 	if (blk_queue_nonrot(bdev_get_queue(p->bdev))) {
1853 		p->flags |= SWP_SOLIDSTATE;
1854 		srandom32((u32)get_seconds());
1855 		p->cluster_next = 1 + (random32() % p->highest_bit);
1856 	}
1857 	if (discard_swap(p) == 0)
1858 		p->flags |= SWP_DISCARDABLE;
1859 
1860 	mutex_lock(&swapon_mutex);
1861 	spin_lock(&swap_lock);
1862 	if (swap_flags & SWAP_FLAG_PREFER)
1863 		p->prio =
1864 		  (swap_flags & SWAP_FLAG_PRIO_MASK) >> SWAP_FLAG_PRIO_SHIFT;
1865 	else
1866 		p->prio = --least_priority;
1867 	p->swap_map = swap_map;
1868 	p->flags |= SWP_WRITEOK;
1869 	nr_swap_pages += nr_good_pages;
1870 	total_swap_pages += nr_good_pages;
1871 
1872 	printk(KERN_INFO "Adding %uk swap on %s.  "
1873 			"Priority:%d extents:%d across:%lluk %s%s\n",
1874 		nr_good_pages<<(PAGE_SHIFT-10), name, p->prio,
1875 		nr_extents, (unsigned long long)span<<(PAGE_SHIFT-10),
1876 		(p->flags & SWP_SOLIDSTATE) ? "SS" : "",
1877 		(p->flags & SWP_DISCARDABLE) ? "D" : "");
1878 
1879 	/* insert swap space into swap_list: */
1880 	prev = -1;
1881 	for (i = swap_list.head; i >= 0; i = swap_info[i].next) {
1882 		if (p->prio >= swap_info[i].prio) {
1883 			break;
1884 		}
1885 		prev = i;
1886 	}
1887 	p->next = i;
1888 	if (prev < 0) {
1889 		swap_list.head = swap_list.next = p - swap_info;
1890 	} else {
1891 		swap_info[prev].next = p - swap_info;
1892 	}
1893 	spin_unlock(&swap_lock);
1894 	mutex_unlock(&swapon_mutex);
1895 	error = 0;
1896 	goto out;
1897 bad_swap:
1898 	if (bdev) {
1899 		set_blocksize(bdev, p->old_block_size);
1900 		bd_release(bdev);
1901 	}
1902 	destroy_swap_extents(p);
1903 bad_swap_2:
1904 	spin_lock(&swap_lock);
1905 	p->swap_file = NULL;
1906 	p->flags = 0;
1907 	spin_unlock(&swap_lock);
1908 	vfree(swap_map);
1909 	if (swap_file)
1910 		filp_close(swap_file, NULL);
1911 out:
1912 	if (page && !IS_ERR(page)) {
1913 		kunmap(page);
1914 		page_cache_release(page);
1915 	}
1916 	if (name)
1917 		putname(name);
1918 	if (did_down) {
1919 		if (!error)
1920 			inode->i_flags |= S_SWAPFILE;
1921 		mutex_unlock(&inode->i_mutex);
1922 	}
1923 	return error;
1924 }
1925 
1926 void si_swapinfo(struct sysinfo *val)
1927 {
1928 	unsigned int i;
1929 	unsigned long nr_to_be_unused = 0;
1930 
1931 	spin_lock(&swap_lock);
1932 	for (i = 0; i < nr_swapfiles; i++) {
1933 		if (!(swap_info[i].flags & SWP_USED) ||
1934 		     (swap_info[i].flags & SWP_WRITEOK))
1935 			continue;
1936 		nr_to_be_unused += swap_info[i].inuse_pages;
1937 	}
1938 	val->freeswap = nr_swap_pages + nr_to_be_unused;
1939 	val->totalswap = total_swap_pages + nr_to_be_unused;
1940 	spin_unlock(&swap_lock);
1941 }
1942 
1943 /*
1944  * Verify that a swap entry is valid and increment its swap map count.
1945  *
1946  * Note: if swap_map[] reaches SWAP_MAP_MAX the entries are treated as
1947  * "permanent", but will be reclaimed by the next swapoff.
1948  */
1949 int swap_duplicate(swp_entry_t entry)
1950 {
1951 	struct swap_info_struct * p;
1952 	unsigned long offset, type;
1953 	int result = 0;
1954 
1955 	if (is_migration_entry(entry))
1956 		return 1;
1957 
1958 	type = swp_type(entry);
1959 	if (type >= nr_swapfiles)
1960 		goto bad_file;
1961 	p = type + swap_info;
1962 	offset = swp_offset(entry);
1963 
1964 	spin_lock(&swap_lock);
1965 	if (offset < p->max && p->swap_map[offset]) {
1966 		if (p->swap_map[offset] < SWAP_MAP_MAX - 1) {
1967 			p->swap_map[offset]++;
1968 			result = 1;
1969 		} else if (p->swap_map[offset] <= SWAP_MAP_MAX) {
1970 			if (swap_overflow++ < 5)
1971 				printk(KERN_WARNING "swap_dup: swap entry overflow\n");
1972 			p->swap_map[offset] = SWAP_MAP_MAX;
1973 			result = 1;
1974 		}
1975 	}
1976 	spin_unlock(&swap_lock);
1977 out:
1978 	return result;
1979 
1980 bad_file:
1981 	printk(KERN_ERR "swap_dup: %s%08lx\n", Bad_file, entry.val);
1982 	goto out;
1983 }
1984 
1985 struct swap_info_struct *
1986 get_swap_info_struct(unsigned type)
1987 {
1988 	return &swap_info[type];
1989 }
1990 
1991 /*
1992  * swap_lock prevents swap_map being freed. Don't grab an extra
1993  * reference on the swaphandle, it doesn't matter if it becomes unused.
1994  */
1995 int valid_swaphandles(swp_entry_t entry, unsigned long *offset)
1996 {
1997 	struct swap_info_struct *si;
1998 	int our_page_cluster = page_cluster;
1999 	pgoff_t target, toff;
2000 	pgoff_t base, end;
2001 	int nr_pages = 0;
2002 
2003 	if (!our_page_cluster)	/* no readahead */
2004 		return 0;
2005 
2006 	si = &swap_info[swp_type(entry)];
2007 	target = swp_offset(entry);
2008 	base = (target >> our_page_cluster) << our_page_cluster;
2009 	end = base + (1 << our_page_cluster);
2010 	if (!base)		/* first page is swap header */
2011 		base++;
2012 
2013 	spin_lock(&swap_lock);
2014 	if (end > si->max)	/* don't go beyond end of map */
2015 		end = si->max;
2016 
2017 	/* Count contiguous allocated slots above our target */
2018 	for (toff = target; ++toff < end; nr_pages++) {
2019 		/* Don't read in free or bad pages */
2020 		if (!si->swap_map[toff])
2021 			break;
2022 		if (si->swap_map[toff] == SWAP_MAP_BAD)
2023 			break;
2024 	}
2025 	/* Count contiguous allocated slots below our target */
2026 	for (toff = target; --toff >= base; nr_pages++) {
2027 		/* Don't read in free or bad pages */
2028 		if (!si->swap_map[toff])
2029 			break;
2030 		if (si->swap_map[toff] == SWAP_MAP_BAD)
2031 			break;
2032 	}
2033 	spin_unlock(&swap_lock);
2034 
2035 	/*
2036 	 * Indicate starting offset, and return number of pages to get:
2037 	 * if only 1, say 0, since there's then no readahead to be done.
2038 	 */
2039 	*offset = ++toff;
2040 	return nr_pages? ++nr_pages: 0;
2041 }
2042