mm: memcg: only check for PageSwapCache when uncharging anon
[linux-3.10.git] / mm / highmem.c
1 /*
2  * High memory handling common code and variables.
3  *
4  * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
5  *          Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
6  *
7  *
8  * Redesigned the x86 32-bit VM architecture to deal with
9  * 64-bit physical space. With current x86 CPUs this
10  * means up to 64 Gigabytes physical RAM.
11  *
12  * Rewrote high memory support to move the page cache into
13  * high memory. Implemented permanent (schedulable) kmaps
14  * based on Linus' idea.
15  *
16  * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
17  */
18
19 #include <linux/mm.h>
20 #include <linux/export.h>
21 #include <linux/swap.h>
22 #include <linux/bio.h>
23 #include <linux/pagemap.h>
24 #include <linux/mempool.h>
25 #include <linux/blkdev.h>
26 #include <linux/init.h>
27 #include <linux/hash.h>
28 #include <linux/highmem.h>
29 #include <linux/kgdb.h>
30 #include <asm/tlbflush.h>
31
32
33 #if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32)
34 DEFINE_PER_CPU(int, __kmap_atomic_idx);
35 #endif
36
37 /*
38  * Virtual_count is not a pure "count".
39  *  0 means that it is not mapped, and has not been mapped
40  *    since a TLB flush - it is usable.
41  *  1 means that there are no users, but it has been mapped
42  *    since the last TLB flush - so we can't use it.
43  *  n means that there are (n-1) current users of it.
44  */
45 #ifdef CONFIG_HIGHMEM
46
47 unsigned long totalhigh_pages __read_mostly;
48 EXPORT_SYMBOL(totalhigh_pages);
49
50
51 EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);
52
53 unsigned int nr_free_highpages (void)
54 {
55         pg_data_t *pgdat;
56         unsigned int pages = 0;
57
58         for_each_online_pgdat(pgdat) {
59                 pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM],
60                         NR_FREE_PAGES);
61                 if (zone_movable_is_highmem())
62                         pages += zone_page_state(
63                                         &pgdat->node_zones[ZONE_MOVABLE],
64                                         NR_FREE_PAGES);
65         }
66
67         return pages;
68 }
69
70 static int pkmap_count[LAST_PKMAP];
71 static unsigned int last_pkmap_nr;
72 static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
73
74 pte_t * pkmap_page_table;
75
76 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
77
78 /*
79  * Most architectures have no use for kmap_high_get(), so let's abstract
80  * the disabling of IRQ out of the locking in that case to save on a
81  * potential useless overhead.
82  */
83 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
84 #define lock_kmap()             spin_lock_irq(&kmap_lock)
85 #define unlock_kmap()           spin_unlock_irq(&kmap_lock)
86 #define lock_kmap_any(flags)    spin_lock_irqsave(&kmap_lock, flags)
87 #define unlock_kmap_any(flags)  spin_unlock_irqrestore(&kmap_lock, flags)
88 #else
89 #define lock_kmap()             spin_lock(&kmap_lock)
90 #define unlock_kmap()           spin_unlock(&kmap_lock)
91 #define lock_kmap_any(flags)    \
92                 do { spin_lock(&kmap_lock); (void)(flags); } while (0)
93 #define unlock_kmap_any(flags)  \
94                 do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
95 #endif
96
97 struct page *kmap_to_page(void *vaddr)
98 {
99         unsigned long addr = (unsigned long)vaddr;
100
101         if (addr >= PKMAP_ADDR(0) && addr <= PKMAP_ADDR(LAST_PKMAP)) {
102                 int i = (addr - PKMAP_ADDR(0)) >> PAGE_SHIFT;
103                 return pte_page(pkmap_page_table[i]);
104         }
105
106         return virt_to_page(addr);
107 }
108
109 static void flush_all_zero_pkmaps(void)
110 {
111         int i;
112         int need_flush = 0;
113
114         flush_cache_kmaps();
115
116         for (i = 0; i < LAST_PKMAP; i++) {
117                 struct page *page;
118
119                 /*
120                  * zero means we don't have anything to do,
121                  * >1 means that it is still in use. Only
122                  * a count of 1 means that it is free but
123                  * needs to be unmapped
124                  */
125                 if (pkmap_count[i] != 1)
126                         continue;
127                 pkmap_count[i] = 0;
128
129                 /* sanity check */
130                 BUG_ON(pte_none(pkmap_page_table[i]));
131
132                 /*
133                  * Don't need an atomic fetch-and-clear op here;
134                  * no-one has the page mapped, and cannot get at
135                  * its virtual address (and hence PTE) without first
136                  * getting the kmap_lock (which is held here).
137                  * So no dangers, even with speculative execution.
138                  */
139                 page = pte_page(pkmap_page_table[i]);
140                 pte_clear(&init_mm, (unsigned long)page_address(page),
141                           &pkmap_page_table[i]);
142
143                 set_page_address(page, NULL);
144                 need_flush = 1;
145         }
146         if (need_flush)
147                 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
148 }
149
150 /**
151  * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
152  */
153 void kmap_flush_unused(void)
154 {
155         lock_kmap();
156         flush_all_zero_pkmaps();
157         unlock_kmap();
158 }
159
160 static inline unsigned long map_new_virtual(struct page *page)
161 {
162         unsigned long vaddr;
163         int count;
164
165 start:
166         count = LAST_PKMAP;
167         /* Find an empty entry */
168         for (;;) {
169                 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
170                 if (!last_pkmap_nr) {
171                         flush_all_zero_pkmaps();
172                         count = LAST_PKMAP;
173                 }
174                 if (!pkmap_count[last_pkmap_nr])
175                         break;  /* Found a usable entry */
176                 if (--count)
177                         continue;
178
179                 /*
180                  * Sleep for somebody else to unmap their entries
181                  */
182                 {
183                         DECLARE_WAITQUEUE(wait, current);
184
185                         __set_current_state(TASK_UNINTERRUPTIBLE);
186                         add_wait_queue(&pkmap_map_wait, &wait);
187                         unlock_kmap();
188                         schedule();
189                         remove_wait_queue(&pkmap_map_wait, &wait);
190                         lock_kmap();
191
192                         /* Somebody else might have mapped it while we slept */
193                         if (page_address(page))
194                                 return (unsigned long)page_address(page);
195
196                         /* Re-start */
197                         goto start;
198                 }
199         }
200         vaddr = PKMAP_ADDR(last_pkmap_nr);
201         set_pte_at(&init_mm, vaddr,
202                    &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
203
204         pkmap_count[last_pkmap_nr] = 1;
205         set_page_address(page, (void *)vaddr);
206
207         return vaddr;
208 }
209
210 /**
211  * kmap_high - map a highmem page into memory
212  * @page: &struct page to map
213  *
214  * Returns the page's virtual memory address.
215  *
216  * We cannot call this from interrupts, as it may block.
217  */
218 void *kmap_high(struct page *page)
219 {
220         unsigned long vaddr;
221
222         /*
223          * For highmem pages, we can't trust "virtual" until
224          * after we have the lock.
225          */
226         lock_kmap();
227         vaddr = (unsigned long)page_address(page);
228         if (!vaddr)
229                 vaddr = map_new_virtual(page);
230         pkmap_count[PKMAP_NR(vaddr)]++;
231         BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
232         unlock_kmap();
233         return (void*) vaddr;
234 }
235
236 EXPORT_SYMBOL(kmap_high);
237
238 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
239 /**
240  * kmap_high_get - pin a highmem page into memory
241  * @page: &struct page to pin
242  *
243  * Returns the page's current virtual memory address, or NULL if no mapping
244  * exists.  If and only if a non null address is returned then a
245  * matching call to kunmap_high() is necessary.
246  *
247  * This can be called from any context.
248  */
249 void *kmap_high_get(struct page *page)
250 {
251         unsigned long vaddr, flags;
252
253         lock_kmap_any(flags);
254         vaddr = (unsigned long)page_address(page);
255         if (vaddr) {
256                 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
257                 pkmap_count[PKMAP_NR(vaddr)]++;
258         }
259         unlock_kmap_any(flags);
260         return (void*) vaddr;
261 }
262 #endif
263
264 /**
265  * kunmap_high - unmap a highmem page into memory
266  * @page: &struct page to unmap
267  *
268  * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
269  * only from user context.
270  */
271 void kunmap_high(struct page *page)
272 {
273         unsigned long vaddr;
274         unsigned long nr;
275         unsigned long flags;
276         int need_wakeup;
277
278         lock_kmap_any(flags);
279         vaddr = (unsigned long)page_address(page);
280         BUG_ON(!vaddr);
281         nr = PKMAP_NR(vaddr);
282
283         /*
284          * A count must never go down to zero
285          * without a TLB flush!
286          */
287         need_wakeup = 0;
288         switch (--pkmap_count[nr]) {
289         case 0:
290                 BUG();
291         case 1:
292                 /*
293                  * Avoid an unnecessary wake_up() function call.
294                  * The common case is pkmap_count[] == 1, but
295                  * no waiters.
296                  * The tasks queued in the wait-queue are guarded
297                  * by both the lock in the wait-queue-head and by
298                  * the kmap_lock.  As the kmap_lock is held here,
299                  * no need for the wait-queue-head's lock.  Simply
300                  * test if the queue is empty.
301                  */
302                 need_wakeup = waitqueue_active(&pkmap_map_wait);
303         }
304         unlock_kmap_any(flags);
305
306         /* do wake-up, if needed, race-free outside of the spin lock */
307         if (need_wakeup)
308                 wake_up(&pkmap_map_wait);
309 }
310
311 EXPORT_SYMBOL(kunmap_high);
312 #endif
313
314 #if defined(HASHED_PAGE_VIRTUAL)
315
316 #define PA_HASH_ORDER   7
317
318 /*
319  * Describes one page->virtual association
320  */
321 struct page_address_map {
322         struct page *page;
323         void *virtual;
324         struct list_head list;
325 };
326
327 /*
328  * page_address_map freelist, allocated from page_address_maps.
329  */
330 static struct list_head page_address_pool;      /* freelist */
331 static spinlock_t pool_lock;                    /* protects page_address_pool */
332
333 /*
334  * Hash table bucket
335  */
336 static struct page_address_slot {
337         struct list_head lh;                    /* List of page_address_maps */
338         spinlock_t lock;                        /* Protect this bucket's list */
339 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
340
341 static struct page_address_slot *page_slot(const struct page *page)
342 {
343         return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
344 }
345
346 /**
347  * page_address - get the mapped virtual address of a page
348  * @page: &struct page to get the virtual address of
349  *
350  * Returns the page's virtual address.
351  */
352 void *page_address(const struct page *page)
353 {
354         unsigned long flags;
355         void *ret;
356         struct page_address_slot *pas;
357
358         if (!PageHighMem(page))
359                 return lowmem_page_address(page);
360
361         pas = page_slot(page);
362         ret = NULL;
363         spin_lock_irqsave(&pas->lock, flags);
364         if (!list_empty(&pas->lh)) {
365                 struct page_address_map *pam;
366
367                 list_for_each_entry(pam, &pas->lh, list) {
368                         if (pam->page == page) {
369                                 ret = pam->virtual;
370                                 goto done;
371                         }
372                 }
373         }
374 done:
375         spin_unlock_irqrestore(&pas->lock, flags);
376         return ret;
377 }
378
379 EXPORT_SYMBOL(page_address);
380
381 /**
382  * set_page_address - set a page's virtual address
383  * @page: &struct page to set
384  * @virtual: virtual address to use
385  */
386 void set_page_address(struct page *page, void *virtual)
387 {
388         unsigned long flags;
389         struct page_address_slot *pas;
390         struct page_address_map *pam;
391
392         BUG_ON(!PageHighMem(page));
393
394         pas = page_slot(page);
395         if (virtual) {          /* Add */
396                 BUG_ON(list_empty(&page_address_pool));
397
398                 spin_lock_irqsave(&pool_lock, flags);
399                 pam = list_entry(page_address_pool.next,
400                                 struct page_address_map, list);
401                 list_del(&pam->list);
402                 spin_unlock_irqrestore(&pool_lock, flags);
403
404                 pam->page = page;
405                 pam->virtual = virtual;
406
407                 spin_lock_irqsave(&pas->lock, flags);
408                 list_add_tail(&pam->list, &pas->lh);
409                 spin_unlock_irqrestore(&pas->lock, flags);
410         } else {                /* Remove */
411                 spin_lock_irqsave(&pas->lock, flags);
412                 list_for_each_entry(pam, &pas->lh, list) {
413                         if (pam->page == page) {
414                                 list_del(&pam->list);
415                                 spin_unlock_irqrestore(&pas->lock, flags);
416                                 spin_lock_irqsave(&pool_lock, flags);
417                                 list_add_tail(&pam->list, &page_address_pool);
418                                 spin_unlock_irqrestore(&pool_lock, flags);
419                                 goto done;
420                         }
421                 }
422                 spin_unlock_irqrestore(&pas->lock, flags);
423         }
424 done:
425         return;
426 }
427
428 static struct page_address_map page_address_maps[LAST_PKMAP];
429
430 void __init page_address_init(void)
431 {
432         int i;
433
434         INIT_LIST_HEAD(&page_address_pool);
435         for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)
436                 list_add(&page_address_maps[i].list, &page_address_pool);
437         for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
438                 INIT_LIST_HEAD(&page_address_htable[i].lh);
439                 spin_lock_init(&page_address_htable[i].lock);
440         }
441         spin_lock_init(&pool_lock);
442 }
443
444 #endif  /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */