Merge branch 'stable-3.14' of git://git.infradead.org/users/pcmoore/selinux into...
[platform/adaptation/renesas_rcar/renesas_kernel.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/page_cgroup.h>
21
22 #include <asm/pgtable.h>
23
24 /*
25  * swapper_space is a fiction, retained to simplify the path through
26  * vmscan's shrink_page_list.
27  */
28 static const struct address_space_operations swap_aops = {
29         .writepage      = swap_writepage,
30         .set_page_dirty = swap_set_page_dirty,
31         .migratepage    = migrate_page,
32 };
33
34 static struct backing_dev_info swap_backing_dev_info = {
35         .name           = "swap",
36         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK | BDI_CAP_SWAP_BACKED,
37 };
38
39 struct address_space swapper_spaces[MAX_SWAPFILES] = {
40         [0 ... MAX_SWAPFILES - 1] = {
41                 .page_tree      = RADIX_TREE_INIT(GFP_ATOMIC|__GFP_NOWARN),
42                 .a_ops          = &swap_aops,
43                 .backing_dev_info = &swap_backing_dev_info,
44         }
45 };
46
47 #define INC_CACHE_INFO(x)       do { swap_cache_info.x++; } while (0)
48
49 static struct {
50         unsigned long add_total;
51         unsigned long del_total;
52         unsigned long find_success;
53         unsigned long find_total;
54 } swap_cache_info;
55
56 unsigned long total_swapcache_pages(void)
57 {
58         int i;
59         unsigned long ret = 0;
60
61         for (i = 0; i < MAX_SWAPFILES; i++)
62                 ret += swapper_spaces[i].nrpages;
63         return ret;
64 }
65
66 static atomic_t swapin_readahead_hits = ATOMIC_INIT(4);
67
68 void show_swap_cache_info(void)
69 {
70         printk("%lu pages in swap cache\n", total_swapcache_pages());
71         printk("Swap cache stats: add %lu, delete %lu, find %lu/%lu\n",
72                 swap_cache_info.add_total, swap_cache_info.del_total,
73                 swap_cache_info.find_success, swap_cache_info.find_total);
74         printk("Free swap  = %ldkB\n",
75                 get_nr_swap_pages() << (PAGE_SHIFT - 10));
76         printk("Total swap = %lukB\n", total_swap_pages << (PAGE_SHIFT - 10));
77 }
78
79 /*
80  * __add_to_swap_cache resembles add_to_page_cache_locked on swapper_space,
81  * but sets SwapCache flag and private instead of mapping and index.
82  */
83 int __add_to_swap_cache(struct page *page, swp_entry_t entry)
84 {
85         int error;
86         struct address_space *address_space;
87
88         VM_BUG_ON_PAGE(!PageLocked(page), page);
89         VM_BUG_ON_PAGE(PageSwapCache(page), page);
90         VM_BUG_ON_PAGE(!PageSwapBacked(page), page);
91
92         page_cache_get(page);
93         SetPageSwapCache(page);
94         set_page_private(page, entry.val);
95
96         address_space = swap_address_space(entry);
97         spin_lock_irq(&address_space->tree_lock);
98         error = radix_tree_insert(&address_space->page_tree,
99                                         entry.val, page);
100         if (likely(!error)) {
101                 address_space->nrpages++;
102                 __inc_zone_page_state(page, NR_FILE_PAGES);
103                 INC_CACHE_INFO(add_total);
104         }
105         spin_unlock_irq(&address_space->tree_lock);
106
107         if (unlikely(error)) {
108                 /*
109                  * Only the context which have set SWAP_HAS_CACHE flag
110                  * would call add_to_swap_cache().
111                  * So add_to_swap_cache() doesn't returns -EEXIST.
112                  */
113                 VM_BUG_ON(error == -EEXIST);
114                 set_page_private(page, 0UL);
115                 ClearPageSwapCache(page);
116                 page_cache_release(page);
117         }
118
119         return error;
120 }
121
122
123 int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
124 {
125         int error;
126
127         error = radix_tree_maybe_preload(gfp_mask);
128         if (!error) {
129                 error = __add_to_swap_cache(page, entry);
130                 radix_tree_preload_end();
131         }
132         return error;
133 }
134
135 /*
136  * This must be called only on pages that have
137  * been verified to be in the swap cache.
138  */
139 void __delete_from_swap_cache(struct page *page)
140 {
141         swp_entry_t entry;
142         struct address_space *address_space;
143
144         VM_BUG_ON_PAGE(!PageLocked(page), page);
145         VM_BUG_ON_PAGE(!PageSwapCache(page), page);
146         VM_BUG_ON_PAGE(PageWriteback(page), page);
147
148         entry.val = page_private(page);
149         address_space = swap_address_space(entry);
150         radix_tree_delete(&address_space->page_tree, page_private(page));
151         set_page_private(page, 0);
152         ClearPageSwapCache(page);
153         address_space->nrpages--;
154         __dec_zone_page_state(page, NR_FILE_PAGES);
155         INC_CACHE_INFO(del_total);
156 }
157
158 /**
159  * add_to_swap - allocate swap space for a page
160  * @page: page we want to move to swap
161  *
162  * Allocate swap space for the page and add the page to the
163  * swap cache.  Caller needs to hold the page lock. 
164  */
165 int add_to_swap(struct page *page, struct list_head *list)
166 {
167         swp_entry_t entry;
168         int err;
169
170         VM_BUG_ON_PAGE(!PageLocked(page), page);
171         VM_BUG_ON_PAGE(!PageUptodate(page), page);
172
173         entry = get_swap_page();
174         if (!entry.val)
175                 return 0;
176
177         if (unlikely(PageTransHuge(page)))
178                 if (unlikely(split_huge_page_to_list(page, list))) {
179                         swapcache_free(entry, NULL);
180                         return 0;
181                 }
182
183         /*
184          * Radix-tree node allocations from PF_MEMALLOC contexts could
185          * completely exhaust the page allocator. __GFP_NOMEMALLOC
186          * stops emergency reserves from being allocated.
187          *
188          * TODO: this could cause a theoretical memory reclaim
189          * deadlock in the swap out path.
190          */
191         /*
192          * Add it to the swap cache and mark it dirty
193          */
194         err = add_to_swap_cache(page, entry,
195                         __GFP_HIGH|__GFP_NOMEMALLOC|__GFP_NOWARN);
196
197         if (!err) {     /* Success */
198                 SetPageDirty(page);
199                 return 1;
200         } else {        /* -ENOMEM radix-tree allocation failure */
201                 /*
202                  * add_to_swap_cache() doesn't return -EEXIST, so we can safely
203                  * clear SWAP_HAS_CACHE flag.
204                  */
205                 swapcache_free(entry, NULL);
206                 return 0;
207         }
208 }
209
210 /*
211  * This must be called only on pages that have
212  * been verified to be in the swap cache and locked.
213  * It will never put the page into the free list,
214  * the caller has a reference on the page.
215  */
216 void delete_from_swap_cache(struct page *page)
217 {
218         swp_entry_t entry;
219         struct address_space *address_space;
220
221         entry.val = page_private(page);
222
223         address_space = swap_address_space(entry);
224         spin_lock_irq(&address_space->tree_lock);
225         __delete_from_swap_cache(page);
226         spin_unlock_irq(&address_space->tree_lock);
227
228         swapcache_free(entry, page);
229         page_cache_release(page);
230 }
231
232 /* 
233  * If we are the only user, then try to free up the swap cache. 
234  * 
235  * Its ok to check for PageSwapCache without the page lock
236  * here because we are going to recheck again inside
237  * try_to_free_swap() _with_ the lock.
238  *                                      - Marcelo
239  */
240 static inline void free_swap_cache(struct page *page)
241 {
242         if (PageSwapCache(page) && !page_mapped(page) && trylock_page(page)) {
243                 try_to_free_swap(page);
244                 unlock_page(page);
245         }
246 }
247
248 /* 
249  * Perform a free_page(), also freeing any swap cache associated with
250  * this page if it is the last user of the page.
251  */
252 void free_page_and_swap_cache(struct page *page)
253 {
254         free_swap_cache(page);
255         page_cache_release(page);
256 }
257
258 /*
259  * Passed an array of pages, drop them all from swapcache and then release
260  * them.  They are removed from the LRU and freed if this is their last use.
261  */
262 void free_pages_and_swap_cache(struct page **pages, int nr)
263 {
264         struct page **pagep = pages;
265
266         lru_add_drain();
267         while (nr) {
268                 int todo = min(nr, PAGEVEC_SIZE);
269                 int i;
270
271                 for (i = 0; i < todo; i++)
272                         free_swap_cache(pagep[i]);
273                 release_pages(pagep, todo, 0);
274                 pagep += todo;
275                 nr -= todo;
276         }
277 }
278
279 /*
280  * Lookup a swap entry in the swap cache. A found page will be returned
281  * unlocked and with its refcount incremented - we rely on the kernel
282  * lock getting page table operations atomic even if we drop the page
283  * lock before returning.
284  */
285 struct page * lookup_swap_cache(swp_entry_t entry)
286 {
287         struct page *page;
288
289         page = find_get_page(swap_address_space(entry), entry.val);
290
291         if (page) {
292                 INC_CACHE_INFO(find_success);
293                 if (TestClearPageReadahead(page))
294                         atomic_inc(&swapin_readahead_hits);
295         }
296
297         INC_CACHE_INFO(find_total);
298         return page;
299 }
300
301 /* 
302  * Locate a page of swap in physical memory, reserving swap cache space
303  * and reading the disk if it is not already cached.
304  * A failure return means that either the page allocation failed or that
305  * the swap entry is no longer in use.
306  */
307 struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
308                         struct vm_area_struct *vma, unsigned long addr)
309 {
310         struct page *found_page, *new_page = NULL;
311         int err;
312
313         do {
314                 /*
315                  * First check the swap cache.  Since this is normally
316                  * called after lookup_swap_cache() failed, re-calling
317                  * that would confuse statistics.
318                  */
319                 found_page = find_get_page(swap_address_space(entry),
320                                         entry.val);
321                 if (found_page)
322                         break;
323
324                 /*
325                  * Get a new page to read into from swap.
326                  */
327                 if (!new_page) {
328                         new_page = alloc_page_vma(gfp_mask, vma, addr);
329                         if (!new_page)
330                                 break;          /* Out of memory */
331                 }
332
333                 /*
334                  * call radix_tree_preload() while we can wait.
335                  */
336                 err = radix_tree_maybe_preload(gfp_mask & GFP_KERNEL);
337                 if (err)
338                         break;
339
340                 /*
341                  * Swap entry may have been freed since our caller observed it.
342                  */
343                 err = swapcache_prepare(entry);
344                 if (err == -EEXIST) {
345                         radix_tree_preload_end();
346                         /*
347                          * We might race against get_swap_page() and stumble
348                          * across a SWAP_HAS_CACHE swap_map entry whose page
349                          * has not been brought into the swapcache yet, while
350                          * the other end is scheduled away waiting on discard
351                          * I/O completion at scan_swap_map().
352                          *
353                          * In order to avoid turning this transitory state
354                          * into a permanent loop around this -EEXIST case
355                          * if !CONFIG_PREEMPT and the I/O completion happens
356                          * to be waiting on the CPU waitqueue where we are now
357                          * busy looping, we just conditionally invoke the
358                          * scheduler here, if there are some more important
359                          * tasks to run.
360                          */
361                         cond_resched();
362                         continue;
363                 }
364                 if (err) {              /* swp entry is obsolete ? */
365                         radix_tree_preload_end();
366                         break;
367                 }
368
369                 /* May fail (-ENOMEM) if radix-tree node allocation failed. */
370                 __set_page_locked(new_page);
371                 SetPageSwapBacked(new_page);
372                 err = __add_to_swap_cache(new_page, entry);
373                 if (likely(!err)) {
374                         radix_tree_preload_end();
375                         /*
376                          * Initiate read into locked page and return.
377                          */
378                         lru_cache_add_anon(new_page);
379                         swap_readpage(new_page);
380                         return new_page;
381                 }
382                 radix_tree_preload_end();
383                 ClearPageSwapBacked(new_page);
384                 __clear_page_locked(new_page);
385                 /*
386                  * add_to_swap_cache() doesn't return -EEXIST, so we can safely
387                  * clear SWAP_HAS_CACHE flag.
388                  */
389                 swapcache_free(entry, NULL);
390         } while (err != -ENOMEM);
391
392         if (new_page)
393                 page_cache_release(new_page);
394         return found_page;
395 }
396
397 static unsigned long swapin_nr_pages(unsigned long offset)
398 {
399         static unsigned long prev_offset;
400         unsigned int pages, max_pages, last_ra;
401         static atomic_t last_readahead_pages;
402
403         max_pages = 1 << ACCESS_ONCE(page_cluster);
404         if (max_pages <= 1)
405                 return 1;
406
407         /*
408          * This heuristic has been found to work well on both sequential and
409          * random loads, swapping to hard disk or to SSD: please don't ask
410          * what the "+ 2" means, it just happens to work well, that's all.
411          */
412         pages = atomic_xchg(&swapin_readahead_hits, 0) + 2;
413         if (pages == 2) {
414                 /*
415                  * We can have no readahead hits to judge by: but must not get
416                  * stuck here forever, so check for an adjacent offset instead
417                  * (and don't even bother to check whether swap type is same).
418                  */
419                 if (offset != prev_offset + 1 && offset != prev_offset - 1)
420                         pages = 1;
421                 prev_offset = offset;
422         } else {
423                 unsigned int roundup = 4;
424                 while (roundup < pages)
425                         roundup <<= 1;
426                 pages = roundup;
427         }
428
429         if (pages > max_pages)
430                 pages = max_pages;
431
432         /* Don't shrink readahead too fast */
433         last_ra = atomic_read(&last_readahead_pages) / 2;
434         if (pages < last_ra)
435                 pages = last_ra;
436         atomic_set(&last_readahead_pages, pages);
437
438         return pages;
439 }
440
441 /**
442  * swapin_readahead - swap in pages in hope we need them soon
443  * @entry: swap entry of this memory
444  * @gfp_mask: memory allocation flags
445  * @vma: user vma this address belongs to
446  * @addr: target address for mempolicy
447  *
448  * Returns the struct page for entry and addr, after queueing swapin.
449  *
450  * Primitive swap readahead code. We simply read an aligned block of
451  * (1 << page_cluster) entries in the swap area. This method is chosen
452  * because it doesn't cost us any seek time.  We also make sure to queue
453  * the 'original' request together with the readahead ones...
454  *
455  * This has been extended to use the NUMA policies from the mm triggering
456  * the readahead.
457  *
458  * Caller must hold down_read on the vma->vm_mm if vma is not NULL.
459  */
460 struct page *swapin_readahead(swp_entry_t entry, gfp_t gfp_mask,
461                         struct vm_area_struct *vma, unsigned long addr)
462 {
463         struct page *page;
464         unsigned long entry_offset = swp_offset(entry);
465         unsigned long offset = entry_offset;
466         unsigned long start_offset, end_offset;
467         unsigned long mask;
468         struct blk_plug plug;
469
470         mask = swapin_nr_pages(offset) - 1;
471         if (!mask)
472                 goto skip;
473
474         /* Read a page_cluster sized and aligned cluster around offset. */
475         start_offset = offset & ~mask;
476         end_offset = offset | mask;
477         if (!start_offset)      /* First page is swap header. */
478                 start_offset++;
479
480         blk_start_plug(&plug);
481         for (offset = start_offset; offset <= end_offset ; offset++) {
482                 /* Ok, do the async read-ahead now */
483                 page = read_swap_cache_async(swp_entry(swp_type(entry), offset),
484                                                 gfp_mask, vma, addr);
485                 if (!page)
486                         continue;
487                 if (offset != entry_offset)
488                         SetPageReadahead(page);
489                 page_cache_release(page);
490         }
491         blk_finish_plug(&plug);
492
493         lru_add_drain();        /* Push any new pages onto the LRU now */
494 skip:
495         return read_swap_cache_async(entry, gfp_mask, vma, addr);
496 }