Char: istallion, remove hangup bottomhalf
[wrt350n-kernel.git] / mm / highmem.c
blob35d47733cde43af70c61a996c78ef54ca5e20e02
1 /*
2 * High memory handling common code and variables.
4 * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
5 * Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
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.
12 * Rewrote high memory support to move the page cache into
13 * high memory. Implemented permanent (schedulable) kmaps
14 * based on Linus' idea.
16 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
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>
29 #include <linux/blktrace_api.h>
30 #include <asm/tlbflush.h>
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.
40 #ifdef CONFIG_HIGHMEM
42 unsigned long totalhigh_pages __read_mostly;
44 unsigned int nr_free_highpages (void)
46 pg_data_t *pgdat;
47 unsigned int pages = 0;
49 for_each_online_pgdat(pgdat) {
50 pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM],
51 NR_FREE_PAGES);
52 if (zone_movable_is_highmem())
53 pages += zone_page_state(
54 &pgdat->node_zones[ZONE_MOVABLE],
55 NR_FREE_PAGES);
58 return pages;
61 static int pkmap_count[LAST_PKMAP];
62 static unsigned int last_pkmap_nr;
63 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
65 pte_t * pkmap_page_table;
67 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
69 static void flush_all_zero_pkmaps(void)
71 int i;
73 flush_cache_kmaps();
75 for (i = 0; i < LAST_PKMAP; i++) {
76 struct page *page;
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
84 if (pkmap_count[i] != 1)
85 continue;
86 pkmap_count[i] = 0;
88 /* sanity check */
89 BUG_ON(pte_none(pkmap_page_table[i]));
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.
98 page = pte_page(pkmap_page_table[i]);
99 pte_clear(&init_mm, (unsigned long)page_address(page),
100 &pkmap_page_table[i]);
102 set_page_address(page, NULL);
104 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
107 /* Flush all unused kmap mappings in order to remove stray
108 mappings. */
109 void kmap_flush_unused(void)
111 spin_lock(&kmap_lock);
112 flush_all_zero_pkmaps();
113 spin_unlock(&kmap_lock);
116 static inline unsigned long map_new_virtual(struct page *page)
118 unsigned long vaddr;
119 int count;
121 start:
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;
130 if (!pkmap_count[last_pkmap_nr])
131 break; /* Found a usable entry */
132 if (--count)
133 continue;
136 * Sleep for somebody else to unmap their entries
139 DECLARE_WAITQUEUE(wait, current);
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);
148 /* Somebody else might have mapped it while we slept */
149 if (page_address(page))
150 return (unsigned long)page_address(page);
152 /* Re-start */
153 goto start;
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));
160 pkmap_count[last_pkmap_nr] = 1;
161 set_page_address(page, (void *)vaddr);
163 return vaddr;
166 void *kmap_high(struct page *page)
168 unsigned long vaddr;
171 * For highmem pages, we can't trust "virtual" until
172 * after we have the lock.
174 * We cannot call this from interrupts, as it may block
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)]++;
181 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
182 spin_unlock(&kmap_lock);
183 return (void*) vaddr;
186 EXPORT_SYMBOL(kmap_high);
188 void kunmap_high(struct page *page)
190 unsigned long vaddr;
191 unsigned long nr;
192 int need_wakeup;
194 spin_lock(&kmap_lock);
195 vaddr = (unsigned long)page_address(page);
196 BUG_ON(!vaddr);
197 nr = PKMAP_NR(vaddr);
200 * A count must never go down to zero
201 * without a TLB flush!
203 need_wakeup = 0;
204 switch (--pkmap_count[nr]) {
205 case 0:
206 BUG();
207 case 1:
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.
218 need_wakeup = waitqueue_active(&pkmap_map_wait);
220 spin_unlock(&kmap_lock);
222 /* do wake-up, if needed, race-free outside of the spin lock */
223 if (need_wakeup)
224 wake_up(&pkmap_map_wait);
227 EXPORT_SYMBOL(kunmap_high);
228 #endif
230 #if defined(HASHED_PAGE_VIRTUAL)
232 #define PA_HASH_ORDER 7
235 * Describes one page->virtual association
237 struct page_address_map {
238 struct page *page;
239 void *virtual;
240 struct list_head list;
244 * page_address_map freelist, allocated from page_address_maps.
246 static struct list_head page_address_pool; /* freelist */
247 static spinlock_t pool_lock; /* protects page_address_pool */
250 * Hash table bucket
252 static 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];
257 static struct page_address_slot *page_slot(struct page *page)
259 return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
262 void *page_address(struct page *page)
264 unsigned long flags;
265 void *ret;
266 struct page_address_slot *pas;
268 if (!PageHighMem(page))
269 return lowmem_page_address(page);
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;
277 list_for_each_entry(pam, &pas->lh, list) {
278 if (pam->page == page) {
279 ret = pam->virtual;
280 goto done;
284 done:
285 spin_unlock_irqrestore(&pas->lock, flags);
286 return ret;
289 EXPORT_SYMBOL(page_address);
291 void set_page_address(struct page *page, void *virtual)
293 unsigned long flags;
294 struct page_address_slot *pas;
295 struct page_address_map *pam;
297 BUG_ON(!PageHighMem(page));
299 pas = page_slot(page);
300 if (virtual) { /* Add */
301 BUG_ON(list_empty(&page_address_pool));
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);
309 pam->page = page;
310 pam->virtual = virtual;
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;
327 spin_unlock_irqrestore(&pas->lock, flags);
329 done:
330 return;
333 static struct page_address_map page_address_maps[LAST_PKMAP];
335 void __init page_address_init(void)
337 int i;
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);
346 spin_lock_init(&pool_lock);
349 #endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */