mm/sparse.c: fix typo in online_mem_sections
[linux-2.6-microblaze.git] / mm / swap_state.c
1 /*
2  *  linux/mm/swap_state.c
3  *
4  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
5  *  Swap reorganised 29.12.95, Stephen Tweedie
6  *
7  *  Rewritten to use page cache, (C) 1998 Stephen Tweedie
8  */
9 #include <linux/mm.h>
10 #include <linux/gfp.h>
11 #include <linux/kernel_stat.h>
12 #include <linux/swap.h>
13 #include <linux/swapops.h>
14 #include <linux/init.h>
15 #include <linux/pagemap.h>
16 #include <linux/backing-dev.h>
17 #include <linux/blkdev.h>
18 #include <linux/pagevec.h>
19 #include <linux/migrate.h>
20 #include <linux/vmalloc.h>
21 #include <linux/swap_slots.h>
22 #include <linux/huge_mm.h>
23
24 #include <asm/pgtable.h>
25
26 /*
27  * swapper_space is a fiction, retained to simplify the path through
28  * vmscan's shrink_page_list.
29  */
30 static const struct address_space_operations swap_aops = {
31         .writepage      = swap_writepage,
32         .set_page_dirty = swap_set_page_dirty,
33 #ifdef CONFIG_MIGRATION
34         .migratepage    = migrate_page,
35 #endif
36 };
37
38 struct address_space *swapper_spaces[MAX_SWAPFILES];
39 static unsigned int nr_swapper_spaces[MAX_SWAPFILES];
40 bool swap_vma_readahead = true;
41
42 #define SWAP_RA_MAX_ORDER_DEFAULT       3
43
44 static int swap_ra_max_order = SWAP_RA_MAX_ORDER_DEFAULT;
45
46 #define SWAP_RA_WIN_SHIFT       (PAGE_SHIFT / 2)
47 #define SWAP_RA_HITS_MASK       ((1UL << SWAP_RA_WIN_SHIFT) - 1)
48 #define SWAP_RA_HITS_MAX        SWAP_RA_HITS_MASK
49 #define SWAP_RA_WIN_MASK        (~PAGE_MASK & ~SWAP_RA_HITS_MASK)
50
51 #define SWAP_RA_HITS(v)         ((v) & SWAP_RA_HITS_MASK)
52 #define SWAP_RA_WIN(v)          (((v) & SWAP_RA_WIN_MASK) >> SWAP_RA_WIN_SHIFT)
53 #define SWAP_RA_ADDR(v)         ((v) & PAGE_MASK)
54
55 #define SWAP_RA_VAL(addr, win, hits)                            \
56         (((addr) & PAGE_MASK) |                                 \
57          (((win) << SWAP_RA_WIN_SHIFT) & SWAP_RA_WIN_MASK) |    \
58          ((hits) & SWAP_RA_HITS_MASK))
59
60 /* Initial readahead hits is 4 to start up with a small window */
61 #define GET_SWAP_RA_VAL(vma)                                    \
62         (atomic_long_read(&(vma)->swap_readahead_info) ? : 4)
63
64 #define INC_CACHE_INFO(x)       do { swap_cache_info.x++; } while (0)
65 #define ADD_CACHE_INFO(x, nr)   do { swap_cache_info.x += (nr); } while (0)
66
67 static struct {
68         unsigned long add_total;
69         unsigned long del_total;
70         unsigned long find_success;
71         unsigned long find_total;
72 } swap_cache_info;
73
74 unsigned long total_swapcache_pages(void)
75 {
76         unsigned int i, j, nr;
77         unsigned long ret = 0;
78         struct address_space *spaces;
79
80         rcu_read_lock();
81         for (i = 0; i < MAX_SWAPFILES; i++) {
82                 /*
83                  * The corresponding entries in nr_swapper_spaces and
84                  * swapper_spaces will be reused only after at least
85                  * one grace period.  So it is impossible for them
86                  * belongs to different usage.
87                  */
88                 nr = nr_swapper_spaces[i];
89                 spaces = rcu_dereference(swapper_spaces[i]);
90                 if (!nr || !spaces)
91                         continue;
92                 for (j = 0; j < nr; j++)
93                         ret += spaces[j].nrpages;
94         }
95         rcu_read_unlock();
96         return ret;
97 }
98
99 static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);
100
101 void show_swap_cache_info(void)
102 {
103         printk("%lu pages in swap cache\n", total_swapcache_pages());
104         printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
105                 swap_cache_info.add_total, swap_cache_info.del_total,
106                 swap_cache_info.find_success, swap_cache_info.find_total);
107         printk("Free swap  = %ldkB\n",
108                 get_nr_swap_pages() << (PAGE_SHIFT - 10));
109         printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
110 }
111
112 /*
113  * __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
114  * but sets SwapCache flag and private instead of mapping and index.
115  */
116 int __add_to_swap_cache(struct page *page, swp_entry_t entry)
117 {
118         int error, i, nr = hpage_nr_pages(page);
119         struct address_space *address_space;
120         pgoff_t idx = swp_offset(entry);
121
122         VM_BUG_ON_PAGE(!PageLocked(page), page);
123         VM_BUG_ON_PAGE(PageSwapCache(page), page);
124         VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
125
126         page_ref_add(page, nr);
127         SetPageSwapCache(page);
128
129         address_space = swap_address_space(entry);
130         spin_lock_irq(&address_space->tree_lock);
131         for (i = 0; i < nr; i++) {
132                 set_page_private(page + i, entry.val + i);
133                 error = radix_tree_insert(&address_space->page_tree,
134                                           idx + i, page + i);
135                 if (unlikely(error))
136                         break;
137         }
138         if (likely(!error)) {
139                 address_space->nrpages += nr;
140                 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, nr);
141                 ADD_CACHE_INFO(add_total, nr);
142         } else {
143                 /*
144                  * Only the context which have set SWAP_HAS_CACHE flag
145                  * would call add_to_swap_cache().
146                  * So add_to_swap_cache() doesn't returns -EEXIST.
147                  */
148                 VM_BUG_ON(error == -EEXIST);
149                 set_page_private(page + i, 0UL);
150                 while (i--) {
151                         radix_tree_delete(&address_space->page_tree, idx + i);
152                         set_page_private(page + i, 0UL);
153                 }
154                 ClearPageSwapCache(page);
155                 page_ref_sub(page, nr);
156         }
157         spin_unlock_irq(&address_space->tree_lock);
158
159         return error;
160 }
161
162
163 int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
164 {
165         int error;
166
167         error = radix_tree_maybe_preload_order(gfp_mask, compound_order(page));
168         if (!error) {
169                 error = __add_to_swap_cache(page, entry);
170                 radix_tree_preload_end();
171         }
172         return error;
173 }
174
175 /*
176  * This must be called only on pages that have
177  * been verified to be in the swap cache.
178  */
179 void __delete_from_swap_cache(struct page *page)
180 {
181         struct address_space *address_space;
182         int i, nr = hpage_nr_pages(page);
183         swp_entry_t entry;
184         pgoff_t idx;
185
186         VM_BUG_ON_PAGE(!PageLocked(page), page);
187         VM_BUG_ON_PAGE(!PageSwapCache(page), page);
188         VM_BUG_ON_PAGE(PageWriteback(page), page);
189
190         entry.val = page_private(page);
191         address_space = swap_address_space(entry);
192         idx = swp_offset(entry);
193         for (i = 0; i < nr; i++) {
194                 radix_tree_delete(&address_space->page_tree, idx + i);
195                 set_page_private(page + i, 0);
196         }
197         ClearPageSwapCache(page);
198         address_space->nrpages -= nr;
199         __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
200         ADD_CACHE_INFO(del_total, nr);
201 }
202
203 /**
204  * add_to_swap - allocate swap space for a page
205  * @page: page we want to move to swap
206  *
207  * Allocate swap space for the page and add the page to the
208  * swap cache.  Caller needs to hold the page lock. 
209  */
210 int add_to_swap(struct page *page)
211 {
212         swp_entry_t entry;
213         int err;
214
215         VM_BUG_ON_PAGE(!PageLocked(page), page);
216         VM_BUG_ON_PAGE(!PageUptodate(page), page);
217
218         entry = get_swap_page(page);
219         if (!entry.val)
220                 return 0;
221
222         if (mem_cgroup_try_charge_swap(page, entry))
223                 goto fail;
224
225         /*
226          * Radix-tree node allocations from PF_MEMALLOC contexts could
227          * completely exhaust the page allocator. __GFP_NOMEMALLOC
228          * stops emergency reserves from being allocated.
229          *
230          * TODO: this could cause a theoretical memory reclaim
231          * deadlock in the swap out path.
232          */
233         /*
234          * Add it to the swap cache.
235          */
236         err = add_to_swap_cache(page, entry,
237                         __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN);
238         /* -ENOMEM radix-tree allocation failure */
239         if (err)
240                 /*
241                  * add_to_swap_cache() doesn't return -EEXIST, so we can safely
242                  * clear SWAP_HAS_CACHE flag.
243                  */
244                 goto fail;
245
246         return 1;
247
248 fail:
249         put_swap_page(page, entry);
250         return 0;
251 }
252
253 /*
254  * This must be called only on pages that have
255  * been verified to be in the swap cache and locked.
256  * It will never put the page into the free list,
257  * the caller has a reference on the page.
258  */
259 void delete_from_swap_cache(struct page *page)
260 {
261         swp_entry_t entry;
262         struct address_space *address_space;
263
264         entry.val = page_private(page);
265
266         address_space = swap_address_space(entry);
267         spin_lock_irq(&address_space->tree_lock);
268         __delete_from_swap_cache(page);
269         spin_unlock_irq(&address_space->tree_lock);
270
271         put_swap_page(page, entry);
272         page_ref_sub(page, hpage_nr_pages(page));
273 }
274
275 /* 
276  * If we are the only user, then try to free up the swap cache. 
277  * 
278  * Its ok to check for PageSwapCache without the page lock
279  * here because we are going to recheck again inside
280  * try_to_free_swap() _with_ the lock.
281  *                                      - Marcelo
282  */
283 static inline void free_swap_cache(struct page *page)
284 {
285         if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) {
286                 try_to_free_swap(page);
287                 unlock_page(page);
288         }
289 }
290
291 /* 
292  * Perform a free_page(), also freeing any swap cache associated with
293  * this page if it is the last user of the page.
294  */
295 void free_page_and_swap_cache(struct page *page)
296 {
297         free_swap_cache(page);
298         if (!is_huge_zero_page(page))
299                 put_page(page);
300 }
301
302 /*
303  * Passed an array of pages, drop them all from swapcache and then release
304  * them.  They are removed from the LRU and freed if this is their last use.
305  */
306 void free_pages_and_swap_cache(struct page **pages, int nr)
307 {
308         struct page **pagep = pages;
309         int i;
310
311         lru_add_drain();
312         for (i = 0; i < nr; i++)
313                 free_swap_cache(pagep[i]);
314         release_pages(pagep, nr, false);
315 }
316
317 /*
318  * Lookup a swap entry in the swap cache. A found page will be returned
319  * unlocked and with its refcount incremented - we rely on the kernel
320  * lock getting page table operations atomic even if we drop the page
321  * lock before returning.
322  */
323 struct page *lookup_swap_cache(swp_entry_t entry, struct vm_area_struct *vma,
324                                unsigned long addr)
325 {
326         struct page *page;
327         unsigned long ra_info;
328         int win, hits, readahead;
329
330         page = find_get_page(swap_address_space(entry), swp_offset(entry));
331
332         INC_CACHE_INFO(find_total);
333         if (page) {
334                 INC_CACHE_INFO(find_success);
335                 if (unlikely(PageTransCompound(page)))
336                         return page;
337                 readahead = TestClearPageReadahead(page);
338                 if (vma) {
339                         ra_info = GET_SWAP_RA_VAL(vma);
340                         win = SWAP_RA_WIN(ra_info);
341                         hits = SWAP_RA_HITS(ra_info);
342                         if (readahead)
343                                 hits = min_t(int, hits + 1, SWAP_RA_HITS_MAX);
344                         atomic_long_set(&vma->swap_readahead_info,
345                                         SWAP_RA_VAL(addr, win, hits));
346                 }
347                 if (readahead) {
348                         count_vm_event(SWAP_RA_HIT);
349                         if (!vma)
350                                 atomic_inc(&swapin_readahead_hits);
351                 }
352         }
353         return page;
354 }
355
356 struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
357                         struct vm_area_struct *vma, unsigned long addr,
358                         bool *new_page_allocated)
359 {
360         struct page *found_page, *new_page = NULL;
361         struct address_space *swapper_space = swap_address_space(entry);
362         int err;
363         *new_page_allocated = false;
364
365         do {
366                 /*
367                  * First check the swap cache.  Since this is normally
368                  * called after lookup_swap_cache() failed, re-calling
369                  * that would confuse statistics.
370                  */
371                 found_page = find_get_page(swapper_space, swp_offset(entry));
372                 if (found_page)
373                         break;
374
375                 /*
376                  * Just skip read ahead for unused swap slot.
377                  * During swap_off when swap_slot_cache is disabled,
378                  * we have to handle the race between putting
379                  * swap entry in swap cache and marking swap slot
380                  * as SWAP_HAS_CACHE.  That's done in later part of code or
381                  * else swap_off will be aborted if we return NULL.
382                  */
383                 if (!__swp_swapcount(entry) && swap_slot_cache_enabled)
384                         break;
385
386                 /*
387                  * Get a new page to read into from swap.
388                  */
389                 if (!new_page) {
390                         new_page = alloc_page_vma(gfp_mask, vma, addr);
391                         if (!new_page)
392                                 break;          /* Out of memory */
393                 }
394
395                 /*
396                  * call radix_tree_preload() while we can wait.
397                  */
398                 err = radix_tree_maybe_preload(gfp_mask & GFP_KERNEL);
399                 if (err)
400                         break;
401
402                 /*
403                  * Swap entry may have been freed since our caller observed it.
404                  */
405                 err = swapcache_prepare(entry);
406                 if (err == -EEXIST) {
407                         radix_tree_preload_end();
408                         /*
409                          * We might race against get_swap_page() and stumble
410                          * across a SWAP_HAS_CACHE swap_map entry whose page
411                          * has not been brought into the swapcache yet.
412                          */
413                         cond_resched();
414                         continue;
415                 }
416                 if (err) {              /* swp entry is obsolete ? */
417                         radix_tree_preload_end();
418                         break;
419                 }
420
421                 /* May fail (-ENOMEM) if radix-tree node allocation failed. */
422                 __SetPageLocked(new_page);
423                 __SetPageSwapBacked(new_page);
424                 err = __add_to_swap_cache(new_page, entry);
425                 if (likely(!err)) {
426                         radix_tree_preload_end();
427                         /*
428                          * Initiate read into locked page and return.
429                          */
430                         lru_cache_add_anon(new_page);
431                         *new_page_allocated = true;
432                         return new_page;
433                 }
434                 radix_tree_preload_end();
435                 __ClearPageLocked(new_page);
436                 /*
437                  * add_to_swap_cache() doesn't return -EEXIST, so we can safely
438                  * clear SWAP_HAS_CACHE flag.
439                  */
440                 put_swap_page(new_page, entry);
441         } while (err != -ENOMEM);
442
443         if (new_page)
444                 put_page(new_page);
445         return found_page;
446 }
447
448 /*
449  * Locate a page of swap in physical memory, reserving swap cache space
450  * and reading the disk if it is not already cached.
451  * A failure return means that either the page allocation failed or that
452  * the swap entry is no longer in use.
453  */
454 struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
455                 struct vm_area_struct *vma, unsigned long addr, bool do_poll)
456 {
457         bool page_was_allocated;
458         struct page *retpage = __read_swap_cache_async(entry, gfp_mask,
459                         vma, addr, &page_was_allocated);
460
461         if (page_was_allocated)
462                 swap_readpage(retpage, do_poll);
463
464         return retpage;
465 }
466
467 static unsigned int __swapin_nr_pages(unsigned long prev_offset,
468                                       unsigned long offset,
469                                       int hits,
470                                       int max_pages,
471                                       int prev_win)
472 {
473         unsigned int pages, last_ra;
474
475         /*
476          * This heuristic has been found to work well on both sequential and
477          * random loads, swapping to hard disk or to SSD: please don't ask
478          * what the "+ 2" means, it just happens to work well, that's all.
479          */
480         pages = hits + 2;
481         if (pages == 2) {
482                 /*
483                  * We can have no readahead hits to judge by: but must not get
484                  * stuck here forever, so check for an adjacent offset instead
485                  * (and don't even bother to check whether swap type is same).
486                  */
487                 if (offset != prev_offset + 1 && offset != prev_offset - 1)
488                         pages = 1;
489         } else {
490                 unsigned int roundup = 4;
491                 while (roundup < pages)
492                         roundup <<= 1;
493                 pages = roundup;
494         }
495
496         if (pages > max_pages)
497                 pages = max_pages;
498
499         /* Don't shrink readahead too fast */
500         last_ra = prev_win / 2;
501         if (pages < last_ra)
502                 pages = last_ra;
503
504         return pages;
505 }
506
507 static unsigned long swapin_nr_pages(unsigned long offset)
508 {
509         static unsigned long prev_offset;
510         unsigned int hits, pages, max_pages;
511         static atomic_t last_readahead_pages;
512
513         max_pages = 1 << READ_ONCE(page_cluster);
514         if (max_pages <= 1)
515                 return 1;
516
517         hits = atomic_xchg(&swapin_readahead_hits, 0);
518         pages = __swapin_nr_pages(prev_offset, offset, hits, max_pages,
519                                   atomic_read(&last_readahead_pages));
520         if (!hits)
521                 prev_offset = offset;
522         atomic_set(&last_readahead_pages, pages);
523
524         return pages;
525 }
526
527 /**
528  * swapin_readahead - swap in pages in hope we need them soon
529  * @entry: swap entry of this memory
530  * @gfp_mask: memory allocation flags
531  * @vma: user vma this address belongs to
532  * @addr: target address for mempolicy
533  *
534  * Returns the struct page for entry and addr, after queueing swapin.
535  *
536  * Primitive swap readahead code. We simply read an aligned block of
537  * (1 << page_cluster) entries in the swap area. This method is chosen
538  * because it doesn't cost us any seek time.  We also make sure to queue
539  * the 'original' request together with the readahead ones...
540  *
541  * This has been extended to use the NUMA policies from the mm triggering
542  * the readahead.
543  *
544  * Caller must hold down_read on the vma->vm_mm if vma is not NULL.
545  */
546 struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
547                         struct vm_area_struct *vma, unsigned long addr)
548 {
549         struct page *page;
550         unsigned long entry_offset = swp_offset(entry);
551         unsigned long offset = entry_offset;
552         unsigned long start_offset, end_offset;
553         unsigned long mask;
554         struct blk_plug plug;
555         bool do_poll = true, page_allocated;
556
557         mask = swapin_nr_pages(offset) - 1;
558         if (!mask)
559                 goto skip;
560
561         do_poll = false;
562         /* Read a page_cluster sized and aligned cluster around offset. */
563         start_offset = offset & ~mask;
564         end_offset = offset | mask;
565         if (!start_offset)      /* First page is swap header. */
566                 start_offset++;
567
568         blk_start_plug(&plug);
569         for (offset = start_offset; offset <= end_offset ; offset++) {
570                 /* Ok, do the async read-ahead now */
571                 page = __read_swap_cache_async(
572                         swp_entry(swp_type(entry), offset),
573                         gfp_mask, vma, addr, &page_allocated);
574                 if (!page)
575                         continue;
576                 if (page_allocated) {
577                         swap_readpage(page, false);
578                         if (offset != entry_offset &&
579                             likely(!PageTransCompound(page))) {
580                                 SetPageReadahead(page);
581                                 count_vm_event(SWAP_RA);
582                         }
583                 }
584                 put_page(page);
585         }
586         blk_finish_plug(&plug);
587
588         lru_add_drain();        /* Push any new pages onto the LRU now */
589 skip:
590         return read_swap_cache_async(entry, gfp_mask, vma, addr, do_poll);
591 }
592
593 int init_swap_address_space(unsigned int type, unsigned long nr_pages)
594 {
595         struct address_space *spaces, *space;
596         unsigned int i, nr;
597
598         nr = DIV_ROUND_UP(nr_pages, SWAP_ADDRESS_SPACE_PAGES);
599         spaces = kvzalloc(sizeof(struct address_space) * nr, GFP_KERNEL);
600         if (!spaces)
601                 return -ENOMEM;
602         for (i = 0; i < nr; i++) {
603                 space = spaces + i;
604                 INIT_RADIX_TREE(&space->page_tree, GFP_ATOMIC|__GFP_NOWARN);
605                 atomic_set(&space->i_mmap_writable, 0);
606                 space->a_ops = &swap_aops;
607                 /* swap cache doesn't use writeback related tags */
608                 mapping_set_no_writeback_tags(space);
609                 spin_lock_init(&space->tree_lock);
610         }
611         nr_swapper_spaces[type] = nr;
612         rcu_assign_pointer(swapper_spaces[type], spaces);
613
614         return 0;
615 }
616
617 void exit_swap_address_space(unsigned int type)
618 {
619         struct address_space *spaces;
620
621         spaces = swapper_spaces[type];
622         nr_swapper_spaces[type] = 0;
623         rcu_assign_pointer(swapper_spaces[type], NULL);
624         synchronize_rcu();
625         kvfree(spaces);
626 }
627
628 static inline void swap_ra_clamp_pfn(struct vm_area_struct *vma,
629                                      unsigned long faddr,
630                                      unsigned long lpfn,
631                                      unsigned long rpfn,
632                                      unsigned long *start,
633                                      unsigned long *end)
634 {
635         *start = max3(lpfn, PFN_DOWN(vma->vm_start),
636                       PFN_DOWN(faddr & PMD_MASK));
637         *end = min3(rpfn, PFN_DOWN(vma->vm_end),
638                     PFN_DOWN((faddr & PMD_MASK) + PMD_SIZE));
639 }
640
641 struct page *swap_readahead_detect(struct vm_fault *vmf,
642                                    struct vma_swap_readahead *swap_ra)
643 {
644         struct vm_area_struct *vma = vmf->vma;
645         unsigned long swap_ra_info;
646         struct page *page;
647         swp_entry_t entry;
648         unsigned long faddr, pfn, fpfn;
649         unsigned long start, end;
650         pte_t *pte;
651         unsigned int max_win, hits, prev_win, win, left;
652 #ifndef CONFIG_64BIT
653         pte_t *tpte;
654 #endif
655
656         faddr = vmf->address;
657         entry = pte_to_swp_entry(vmf->orig_pte);
658         if ((unlikely(non_swap_entry(entry))))
659                 return NULL;
660         page = lookup_swap_cache(entry, vma, faddr);
661         if (page)
662                 return page;
663
664         max_win = 1 << READ_ONCE(swap_ra_max_order);
665         if (max_win == 1) {
666                 swap_ra->win = 1;
667                 return NULL;
668         }
669
670         fpfn = PFN_DOWN(faddr);
671         swap_ra_info = GET_SWAP_RA_VAL(vma);
672         pfn = PFN_DOWN(SWAP_RA_ADDR(swap_ra_info));
673         prev_win = SWAP_RA_WIN(swap_ra_info);
674         hits = SWAP_RA_HITS(swap_ra_info);
675         swap_ra->win = win = __swapin_nr_pages(pfn, fpfn, hits,
676                                                max_win, prev_win);
677         atomic_long_set(&vma->swap_readahead_info,
678                         SWAP_RA_VAL(faddr, win, 0));
679
680         if (win == 1)
681                 return NULL;
682
683         /* Copy the PTEs because the page table may be unmapped */
684         if (fpfn == pfn + 1)
685                 swap_ra_clamp_pfn(vma, faddr, fpfn, fpfn + win, &start, &end);
686         else if (pfn == fpfn + 1)
687                 swap_ra_clamp_pfn(vma, faddr, fpfn - win + 1, fpfn + 1,
688                                   &start, &end);
689         else {
690                 left = (win - 1) / 2;
691                 swap_ra_clamp_pfn(vma, faddr, fpfn - left, fpfn + win - left,
692                                   &start, &end);
693         }
694         swap_ra->nr_pte = end - start;
695         swap_ra->offset = fpfn - start;
696         pte = vmf->pte - swap_ra->offset;
697 #ifdef CONFIG_64BIT
698         swap_ra->ptes = pte;
699 #else
700         tpte = swap_ra->ptes;
701         for (pfn = start; pfn != end; pfn++)
702                 *tpte++ = *pte++;
703 #endif
704
705         return NULL;
706 }
707
708 struct page *do_swap_page_readahead(swp_entry_t fentry, gfp_t gfp_mask,
709                                     struct vm_fault *vmf,
710                                     struct vma_swap_readahead *swap_ra)
711 {
712         struct blk_plug plug;
713         struct vm_area_struct *vma = vmf->vma;
714         struct page *page;
715         pte_t *pte, pentry;
716         swp_entry_t entry;
717         unsigned int i;
718         bool page_allocated;
719
720         if (swap_ra->win == 1)
721                 goto skip;
722
723         blk_start_plug(&plug);
724         for (i = 0, pte = swap_ra->ptes; i < swap_ra->nr_pte;
725              i++, pte++) {
726                 pentry = *pte;
727                 if (pte_none(pentry))
728                         continue;
729                 if (pte_present(pentry))
730                         continue;
731                 entry = pte_to_swp_entry(pentry);
732                 if (unlikely(non_swap_entry(entry)))
733                         continue;
734                 page = __read_swap_cache_async(entry, gfp_mask, vma,
735                                                vmf->address, &page_allocated);
736                 if (!page)
737                         continue;
738                 if (page_allocated) {
739                         swap_readpage(page, false);
740                         if (i != swap_ra->offset &&
741                             likely(!PageTransCompound(page))) {
742                                 SetPageReadahead(page);
743                                 count_vm_event(SWAP_RA);
744                         }
745                 }
746                 put_page(page);
747         }
748         blk_finish_plug(&plug);
749         lru_add_drain();
750 skip:
751         return read_swap_cache_async(fentry, gfp_mask, vma, vmf->address,
752                                      swap_ra->win == 1);
753 }
754
755 #ifdef CONFIG_SYSFS
756 static ssize_t vma_ra_enabled_show(struct kobject *kobj,
757                                      struct kobj_attribute *attr, char *buf)
758 {
759         return sprintf(buf, "%s\n", swap_vma_readahead ? "true" : "false");
760 }
761 static ssize_t vma_ra_enabled_store(struct kobject *kobj,
762                                       struct kobj_attribute *attr,
763                                       const char *buf, size_t count)
764 {
765         if (!strncmp(buf, "true", 4) || !strncmp(buf, "1", 1))
766                 swap_vma_readahead = true;
767         else if (!strncmp(buf, "false", 5) || !strncmp(buf, "0", 1))
768                 swap_vma_readahead = false;
769         else
770                 return -EINVAL;
771
772         return count;
773 }
774 static struct kobj_attribute vma_ra_enabled_attr =
775         __ATTR(vma_ra_enabled, 0644, vma_ra_enabled_show,
776                vma_ra_enabled_store);
777
778 static ssize_t vma_ra_max_order_show(struct kobject *kobj,
779                                      struct kobj_attribute *attr, char *buf)
780 {
781         return sprintf(buf, "%d\n", swap_ra_max_order);
782 }
783 static ssize_t vma_ra_max_order_store(struct kobject *kobj,
784                                       struct kobj_attribute *attr,
785                                       const char *buf, size_t count)
786 {
787         int err, v;
788
789         err = kstrtoint(buf, 10, &v);
790         if (err || v > SWAP_RA_ORDER_CEILING || v <= 0)
791                 return -EINVAL;
792
793         swap_ra_max_order = v;
794
795         return count;
796 }
797 static struct kobj_attribute vma_ra_max_order_attr =
798         __ATTR(vma_ra_max_order, 0644, vma_ra_max_order_show,
799                vma_ra_max_order_store);
800
801 static struct attribute *swap_attrs[] = {
802         &vma_ra_enabled_attr.attr,
803         &vma_ra_max_order_attr.attr,
804         NULL,
805 };
806
807 static struct attribute_group swap_attr_group = {
808         .attrs = swap_attrs,
809 };
810
811 static int __init swap_init_sysfs(void)
812 {
813         int err;
814         struct kobject *swap_kobj;
815
816         swap_kobj = kobject_create_and_add("swap", mm_kobj);
817         if (!swap_kobj) {
818                 pr_err("failed to create swap kobject\n");
819                 return -ENOMEM;
820         }
821         err = sysfs_create_group(swap_kobj, &swap_attr_group);
822         if (err) {
823                 pr_err("failed to register swap group\n");
824                 goto delete_obj;
825         }
826         return 0;
827
828 delete_obj:
829         kobject_put(swap_kobj);
830         return err;
831 }
832 subsys_initcall(swap_init_sysfs);
833 #endif