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/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> 31 32 /* 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 41 42 unsigned long totalhigh_pages __read_mostly; 43 44 unsigned int nr_free_highpages (void) 45 { 46 pg_data_t *pgdat; 47 unsigned int pages = 0; 48 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); 56 } 57 58 return pages; 59 } 60 61 static int pkmap_count[LAST_PKMAP]; 62 static unsigned int last_pkmap_nr; 63 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock); 64 65 pte_t * pkmap_page_table; 66 67 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait); 68 69 static 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 */ 89 BUG_ON(pte_none(pkmap_page_table[i])); 90 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 } 106 107 /* Flush all unused kmap mappings in order to remove stray 108 mappings. */ 109 void kmap_flush_unused(void) 110 { 111 spin_lock(&kmap_lock); 112 flush_all_zero_pkmaps(); 113 spin_unlock(&kmap_lock); 114 } 115 116 static inline unsigned long map_new_virtual(struct page *page) 117 { 118 unsigned long vaddr; 119 int count; 120 121 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; 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 } 165 166 void *kmap_high(struct page *page) 167 { 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)]++; 181 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2); 182 spin_unlock(&kmap_lock); 183 return (void*) vaddr; 184 } 185 186 EXPORT_SYMBOL(kmap_high); 187 188 void kunmap_high(struct page *page) 189 { 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); 196 BUG_ON(!vaddr); 197 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 } 226 227 EXPORT_SYMBOL(kunmap_high); 228 #endif 229 230 #if defined(HASHED_PAGE_VIRTUAL) 231 232 #define PA_HASH_ORDER 7 233 234 /* 235 * Describes one page->virtual association 236 */ 237 struct 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 */ 246 static struct list_head page_address_pool; /* freelist */ 247 static spinlock_t pool_lock; /* protects page_address_pool */ 248 249 /* 250 * Hash table bucket 251 */ 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]; 256 257 static struct page_address_slot *page_slot(struct page *page) 258 { 259 return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)]; 260 } 261 262 void *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 } 284 done: 285 spin_unlock_irqrestore(&pas->lock, flags); 286 return ret; 287 } 288 289 EXPORT_SYMBOL(page_address); 290 291 void 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 } 329 done: 330 return; 331 } 332 333 static struct page_address_map page_address_maps[LAST_PKMAP]; 334 335 void __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) */ 350