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 static void flush_all_zero_pkmaps(void) 98 { 99 int i; 100 int need_flush = 0; 101 102 flush_cache_kmaps(); 103 104 for (i = 0; i < LAST_PKMAP; i++) { 105 struct page *page; 106 107 /* 108 * zero means we don't have anything to do, 109 * >1 means that it is still in use. Only 110 * a count of 1 means that it is free but 111 * needs to be unmapped 112 */ 113 if (pkmap_count[i] != 1) 114 continue; 115 pkmap_count[i] = 0; 116 117 /* sanity check */ 118 BUG_ON(pte_none(pkmap_page_table[i])); 119 120 /* 121 * Don't need an atomic fetch-and-clear op here; 122 * no-one has the page mapped, and cannot get at 123 * its virtual address (and hence PTE) without first 124 * getting the kmap_lock (which is held here). 125 * So no dangers, even with speculative execution. 126 */ 127 page = pte_page(pkmap_page_table[i]); 128 pte_clear(&init_mm, (unsigned long)page_address(page), 129 &pkmap_page_table[i]); 130 131 set_page_address(page, NULL); 132 need_flush = 1; 133 } 134 if (need_flush) 135 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP)); 136 } 137 138 /** 139 * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings 140 */ 141 void kmap_flush_unused(void) 142 { 143 lock_kmap(); 144 flush_all_zero_pkmaps(); 145 unlock_kmap(); 146 } 147 148 static inline unsigned long map_new_virtual(struct page *page) 149 { 150 unsigned long vaddr; 151 int count; 152 153 start: 154 count = LAST_PKMAP; 155 /* Find an empty entry */ 156 for (;;) { 157 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK; 158 if (!last_pkmap_nr) { 159 flush_all_zero_pkmaps(); 160 count = LAST_PKMAP; 161 } 162 if (!pkmap_count[last_pkmap_nr]) 163 break; /* Found a usable entry */ 164 if (--count) 165 continue; 166 167 /* 168 * Sleep for somebody else to unmap their entries 169 */ 170 { 171 DECLARE_WAITQUEUE(wait, current); 172 173 __set_current_state(TASK_UNINTERRUPTIBLE); 174 add_wait_queue(&pkmap_map_wait, &wait); 175 unlock_kmap(); 176 schedule(); 177 remove_wait_queue(&pkmap_map_wait, &wait); 178 lock_kmap(); 179 180 /* Somebody else might have mapped it while we slept */ 181 if (page_address(page)) 182 return (unsigned long)page_address(page); 183 184 /* Re-start */ 185 goto start; 186 } 187 } 188 vaddr = PKMAP_ADDR(last_pkmap_nr); 189 set_pte_at(&init_mm, vaddr, 190 &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot)); 191 192 pkmap_count[last_pkmap_nr] = 1; 193 set_page_address(page, (void *)vaddr); 194 195 return vaddr; 196 } 197 198 /** 199 * kmap_high - map a highmem page into memory 200 * @page: &struct page to map 201 * 202 * Returns the page's virtual memory address. 203 * 204 * We cannot call this from interrupts, as it may block. 205 */ 206 void *kmap_high(struct page *page) 207 { 208 unsigned long vaddr; 209 210 /* 211 * For highmem pages, we can't trust "virtual" until 212 * after we have the lock. 213 */ 214 lock_kmap(); 215 vaddr = (unsigned long)page_address(page); 216 if (!vaddr) 217 vaddr = map_new_virtual(page); 218 pkmap_count[PKMAP_NR(vaddr)]++; 219 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2); 220 unlock_kmap(); 221 return (void*) vaddr; 222 } 223 224 EXPORT_SYMBOL(kmap_high); 225 226 #ifdef ARCH_NEEDS_KMAP_HIGH_GET 227 /** 228 * kmap_high_get - pin a highmem page into memory 229 * @page: &struct page to pin 230 * 231 * Returns the page's current virtual memory address, or NULL if no mapping 232 * exists. If and only if a non null address is returned then a 233 * matching call to kunmap_high() is necessary. 234 * 235 * This can be called from any context. 236 */ 237 void *kmap_high_get(struct page *page) 238 { 239 unsigned long vaddr, flags; 240 241 lock_kmap_any(flags); 242 vaddr = (unsigned long)page_address(page); 243 if (vaddr) { 244 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1); 245 pkmap_count[PKMAP_NR(vaddr)]++; 246 } 247 unlock_kmap_any(flags); 248 return (void*) vaddr; 249 } 250 #endif 251 252 /** 253 * kunmap_high - unmap a highmem page into memory 254 * @page: &struct page to unmap 255 * 256 * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called 257 * only from user context. 258 */ 259 void kunmap_high(struct page *page) 260 { 261 unsigned long vaddr; 262 unsigned long nr; 263 unsigned long flags; 264 int need_wakeup; 265 266 lock_kmap_any(flags); 267 vaddr = (unsigned long)page_address(page); 268 BUG_ON(!vaddr); 269 nr = PKMAP_NR(vaddr); 270 271 /* 272 * A count must never go down to zero 273 * without a TLB flush! 274 */ 275 need_wakeup = 0; 276 switch (--pkmap_count[nr]) { 277 case 0: 278 BUG(); 279 case 1: 280 /* 281 * Avoid an unnecessary wake_up() function call. 282 * The common case is pkmap_count[] == 1, but 283 * no waiters. 284 * The tasks queued in the wait-queue are guarded 285 * by both the lock in the wait-queue-head and by 286 * the kmap_lock. As the kmap_lock is held here, 287 * no need for the wait-queue-head's lock. Simply 288 * test if the queue is empty. 289 */ 290 need_wakeup = waitqueue_active(&pkmap_map_wait); 291 } 292 unlock_kmap_any(flags); 293 294 /* do wake-up, if needed, race-free outside of the spin lock */ 295 if (need_wakeup) 296 wake_up(&pkmap_map_wait); 297 } 298 299 EXPORT_SYMBOL(kunmap_high); 300 #endif 301 302 #if defined(HASHED_PAGE_VIRTUAL) 303 304 #define PA_HASH_ORDER 7 305 306 /* 307 * Describes one page->virtual association 308 */ 309 struct page_address_map { 310 struct page *page; 311 void *virtual; 312 struct list_head list; 313 }; 314 315 /* 316 * page_address_map freelist, allocated from page_address_maps. 317 */ 318 static struct list_head page_address_pool; /* freelist */ 319 static spinlock_t pool_lock; /* protects page_address_pool */ 320 321 /* 322 * Hash table bucket 323 */ 324 static struct page_address_slot { 325 struct list_head lh; /* List of page_address_maps */ 326 spinlock_t lock; /* Protect this bucket's list */ 327 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER]; 328 329 static struct page_address_slot *page_slot(const struct page *page) 330 { 331 return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)]; 332 } 333 334 /** 335 * page_address - get the mapped virtual address of a page 336 * @page: &struct page to get the virtual address of 337 * 338 * Returns the page's virtual address. 339 */ 340 void *page_address(const struct page *page) 341 { 342 unsigned long flags; 343 void *ret; 344 struct page_address_slot *pas; 345 346 if (!PageHighMem(page)) 347 return lowmem_page_address(page); 348 349 pas = page_slot(page); 350 ret = NULL; 351 spin_lock_irqsave(&pas->lock, flags); 352 if (!list_empty(&pas->lh)) { 353 struct page_address_map *pam; 354 355 list_for_each_entry(pam, &pas->lh, list) { 356 if (pam->page == page) { 357 ret = pam->virtual; 358 goto done; 359 } 360 } 361 } 362 done: 363 spin_unlock_irqrestore(&pas->lock, flags); 364 return ret; 365 } 366 367 EXPORT_SYMBOL(page_address); 368 369 /** 370 * set_page_address - set a page's virtual address 371 * @page: &struct page to set 372 * @virtual: virtual address to use 373 */ 374 void set_page_address(struct page *page, void *virtual) 375 { 376 unsigned long flags; 377 struct page_address_slot *pas; 378 struct page_address_map *pam; 379 380 BUG_ON(!PageHighMem(page)); 381 382 pas = page_slot(page); 383 if (virtual) { /* Add */ 384 BUG_ON(list_empty(&page_address_pool)); 385 386 spin_lock_irqsave(&pool_lock, flags); 387 pam = list_entry(page_address_pool.next, 388 struct page_address_map, list); 389 list_del(&pam->list); 390 spin_unlock_irqrestore(&pool_lock, flags); 391 392 pam->page = page; 393 pam->virtual = virtual; 394 395 spin_lock_irqsave(&pas->lock, flags); 396 list_add_tail(&pam->list, &pas->lh); 397 spin_unlock_irqrestore(&pas->lock, flags); 398 } else { /* Remove */ 399 spin_lock_irqsave(&pas->lock, flags); 400 list_for_each_entry(pam, &pas->lh, list) { 401 if (pam->page == page) { 402 list_del(&pam->list); 403 spin_unlock_irqrestore(&pas->lock, flags); 404 spin_lock_irqsave(&pool_lock, flags); 405 list_add_tail(&pam->list, &page_address_pool); 406 spin_unlock_irqrestore(&pool_lock, flags); 407 goto done; 408 } 409 } 410 spin_unlock_irqrestore(&pas->lock, flags); 411 } 412 done: 413 return; 414 } 415 416 static struct page_address_map page_address_maps[LAST_PKMAP]; 417 418 void __init page_address_init(void) 419 { 420 int i; 421 422 INIT_LIST_HEAD(&page_address_pool); 423 for (i = 0; i < ARRAY_SIZE(page_address_maps); i++) 424 list_add(&page_address_maps[i].list, &page_address_pool); 425 for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) { 426 INIT_LIST_HEAD(&page_address_htable[i].lh); 427 spin_lock_init(&page_address_htable[i].lock); 428 } 429 spin_lock_init(&pool_lock); 430 } 431 432 #endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */ 433