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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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/module.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>
Jens Axboe2056a782006-03-23 20:00:26 +010029#include <linux/blktrace_api.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070030#include <asm/tlbflush.h>
31
Linus Torvalds1da177e2005-04-16 15:20:36 -070032/*
33 * Virtual_count is not a pure "count".
34 * 0 means that it is not mapped, and has not been mapped
35 * since a TLB flush - it is usable.
36 * 1 means that there are no users, but it has been mapped
37 * since the last TLB flush - so we can't use it.
38 * n means that there are (n-1) current users of it.
39 */
40#ifdef CONFIG_HIGHMEM
Al Viro260b2362005-10-21 03:22:44 -040041
Christoph Lameterc1f60a52006-09-25 23:31:11 -070042unsigned long totalhigh_pages __read_mostly;
43
44unsigned int nr_free_highpages (void)
45{
46 pg_data_t *pgdat;
47 unsigned int pages = 0;
48
Mel Gorman2a1e2742007-07-17 04:03:12 -070049 for_each_online_pgdat(pgdat) {
Christoph Lameterd23ad422007-02-10 01:43:02 -080050 pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM],
51 NR_FREE_PAGES);
Mel Gorman2a1e2742007-07-17 04:03:12 -070052 if (zone_movable_is_highmem())
53 pages += zone_page_state(
54 &pgdat->node_zones[ZONE_MOVABLE],
55 NR_FREE_PAGES);
56 }
Christoph Lameterc1f60a52006-09-25 23:31:11 -070057
58 return pages;
59}
60
Linus Torvalds1da177e2005-04-16 15:20:36 -070061static int pkmap_count[LAST_PKMAP];
62static unsigned int last_pkmap_nr;
63static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
64
65pte_t * pkmap_page_table;
66
67static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
68
69static void flush_all_zero_pkmaps(void)
70{
71 int i;
72
73 flush_cache_kmaps();
74
75 for (i = 0; i < LAST_PKMAP; i++) {
76 struct page *page;
77
78 /*
79 * zero means we don't have anything to do,
80 * >1 means that it is still in use. Only
81 * a count of 1 means that it is free but
82 * needs to be unmapped
83 */
84 if (pkmap_count[i] != 1)
85 continue;
86 pkmap_count[i] = 0;
87
88 /* sanity check */
Eric Sesterhenn75babca2006-04-02 13:47:35 +020089 BUG_ON(pte_none(pkmap_page_table[i]));
Linus Torvalds1da177e2005-04-16 15:20:36 -070090
91 /*
92 * Don't need an atomic fetch-and-clear op here;
93 * no-one has the page mapped, and cannot get at
94 * its virtual address (and hence PTE) without first
95 * getting the kmap_lock (which is held here).
96 * So no dangers, even with speculative execution.
97 */
98 page = pte_page(pkmap_page_table[i]);
99 pte_clear(&init_mm, (unsigned long)page_address(page),
100 &pkmap_page_table[i]);
101
102 set_page_address(page, NULL);
103 }
104 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
105}
106
Jeremy Fitzhardingece6234b2007-05-02 19:27:15 +0200107/* Flush all unused kmap mappings in order to remove stray
108 mappings. */
109void kmap_flush_unused(void)
110{
111 spin_lock(&kmap_lock);
112 flush_all_zero_pkmaps();
113 spin_unlock(&kmap_lock);
114}
115
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116static inline unsigned long map_new_virtual(struct page *page)
117{
118 unsigned long vaddr;
119 int count;
120
121start:
122 count = LAST_PKMAP;
123 /* Find an empty entry */
124 for (;;) {
125 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
126 if (!last_pkmap_nr) {
127 flush_all_zero_pkmaps();
128 count = LAST_PKMAP;
129 }
130 if (!pkmap_count[last_pkmap_nr])
131 break; /* Found a usable entry */
132 if (--count)
133 continue;
134
135 /*
136 * Sleep for somebody else to unmap their entries
137 */
138 {
139 DECLARE_WAITQUEUE(wait, current);
140
141 __set_current_state(TASK_UNINTERRUPTIBLE);
142 add_wait_queue(&pkmap_map_wait, &wait);
143 spin_unlock(&kmap_lock);
144 schedule();
145 remove_wait_queue(&pkmap_map_wait, &wait);
146 spin_lock(&kmap_lock);
147
148 /* Somebody else might have mapped it while we slept */
149 if (page_address(page))
150 return (unsigned long)page_address(page);
151
152 /* Re-start */
153 goto start;
154 }
155 }
156 vaddr = PKMAP_ADDR(last_pkmap_nr);
157 set_pte_at(&init_mm, vaddr,
158 &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
159
160 pkmap_count[last_pkmap_nr] = 1;
161 set_page_address(page, (void *)vaddr);
162
163 return vaddr;
164}
165
Harvey Harrison920c7a52008-02-04 22:29:26 -0800166void *kmap_high(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700167{
168 unsigned long vaddr;
169
170 /*
171 * For highmem pages, we can't trust "virtual" until
172 * after we have the lock.
173 *
174 * We cannot call this from interrupts, as it may block
175 */
176 spin_lock(&kmap_lock);
177 vaddr = (unsigned long)page_address(page);
178 if (!vaddr)
179 vaddr = map_new_virtual(page);
180 pkmap_count[PKMAP_NR(vaddr)]++;
Eric Sesterhenn75babca2006-04-02 13:47:35 +0200181 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182 spin_unlock(&kmap_lock);
183 return (void*) vaddr;
184}
185
186EXPORT_SYMBOL(kmap_high);
187
Harvey Harrison920c7a52008-02-04 22:29:26 -0800188void kunmap_high(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189{
190 unsigned long vaddr;
191 unsigned long nr;
192 int need_wakeup;
193
194 spin_lock(&kmap_lock);
195 vaddr = (unsigned long)page_address(page);
Eric Sesterhenn75babca2006-04-02 13:47:35 +0200196 BUG_ON(!vaddr);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700197 nr = PKMAP_NR(vaddr);
198
199 /*
200 * A count must never go down to zero
201 * without a TLB flush!
202 */
203 need_wakeup = 0;
204 switch (--pkmap_count[nr]) {
205 case 0:
206 BUG();
207 case 1:
208 /*
209 * Avoid an unnecessary wake_up() function call.
210 * The common case is pkmap_count[] == 1, but
211 * no waiters.
212 * The tasks queued in the wait-queue are guarded
213 * by both the lock in the wait-queue-head and by
214 * the kmap_lock. As the kmap_lock is held here,
215 * no need for the wait-queue-head's lock. Simply
216 * test if the queue is empty.
217 */
218 need_wakeup = waitqueue_active(&pkmap_map_wait);
219 }
220 spin_unlock(&kmap_lock);
221
222 /* do wake-up, if needed, race-free outside of the spin lock */
223 if (need_wakeup)
224 wake_up(&pkmap_map_wait);
225}
226
227EXPORT_SYMBOL(kunmap_high);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700228#endif
229
Linus Torvalds1da177e2005-04-16 15:20:36 -0700230#if defined(HASHED_PAGE_VIRTUAL)
231
232#define PA_HASH_ORDER 7
233
234/*
235 * Describes one page->virtual association
236 */
237struct page_address_map {
238 struct page *page;
239 void *virtual;
240 struct list_head list;
241};
242
243/*
244 * page_address_map freelist, allocated from page_address_maps.
245 */
246static struct list_head page_address_pool; /* freelist */
247static spinlock_t pool_lock; /* protects page_address_pool */
248
249/*
250 * Hash table bucket
251 */
252static struct page_address_slot {
253 struct list_head lh; /* List of page_address_maps */
254 spinlock_t lock; /* Protect this bucket's list */
255} ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
256
257static struct page_address_slot *page_slot(struct page *page)
258{
259 return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
260}
261
262void *page_address(struct page *page)
263{
264 unsigned long flags;
265 void *ret;
266 struct page_address_slot *pas;
267
268 if (!PageHighMem(page))
269 return lowmem_page_address(page);
270
271 pas = page_slot(page);
272 ret = NULL;
273 spin_lock_irqsave(&pas->lock, flags);
274 if (!list_empty(&pas->lh)) {
275 struct page_address_map *pam;
276
277 list_for_each_entry(pam, &pas->lh, list) {
278 if (pam->page == page) {
279 ret = pam->virtual;
280 goto done;
281 }
282 }
283 }
284done:
285 spin_unlock_irqrestore(&pas->lock, flags);
286 return ret;
287}
288
289EXPORT_SYMBOL(page_address);
290
291void set_page_address(struct page *page, void *virtual)
292{
293 unsigned long flags;
294 struct page_address_slot *pas;
295 struct page_address_map *pam;
296
297 BUG_ON(!PageHighMem(page));
298
299 pas = page_slot(page);
300 if (virtual) { /* Add */
301 BUG_ON(list_empty(&page_address_pool));
302
303 spin_lock_irqsave(&pool_lock, flags);
304 pam = list_entry(page_address_pool.next,
305 struct page_address_map, list);
306 list_del(&pam->list);
307 spin_unlock_irqrestore(&pool_lock, flags);
308
309 pam->page = page;
310 pam->virtual = virtual;
311
312 spin_lock_irqsave(&pas->lock, flags);
313 list_add_tail(&pam->list, &pas->lh);
314 spin_unlock_irqrestore(&pas->lock, flags);
315 } else { /* Remove */
316 spin_lock_irqsave(&pas->lock, flags);
317 list_for_each_entry(pam, &pas->lh, list) {
318 if (pam->page == page) {
319 list_del(&pam->list);
320 spin_unlock_irqrestore(&pas->lock, flags);
321 spin_lock_irqsave(&pool_lock, flags);
322 list_add_tail(&pam->list, &page_address_pool);
323 spin_unlock_irqrestore(&pool_lock, flags);
324 goto done;
325 }
326 }
327 spin_unlock_irqrestore(&pas->lock, flags);
328 }
329done:
330 return;
331}
332
333static struct page_address_map page_address_maps[LAST_PKMAP];
334
335void __init page_address_init(void)
336{
337 int i;
338
339 INIT_LIST_HEAD(&page_address_pool);
340 for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)
341 list_add(&page_address_maps[i].list, &page_address_pool);
342 for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
343 INIT_LIST_HEAD(&page_address_htable[i].lh);
344 spin_lock_init(&page_address_htable[i].lock);
345 }
346 spin_lock_init(&pool_lock);
347}
348
349#endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */