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 EXPORT_SYMBOL(totalhigh_pages); 44 45 unsigned int nr_free_highpages (void) 46 { 47 pg_data_t *pgdat; 48 unsigned int pages = 0; 49 50 for_each_online_pgdat(pgdat) { 51 pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM], 52 NR_FREE_PAGES); 53 if (zone_movable_is_highmem()) 54 pages += zone_page_state( 55 &pgdat->node_zones[ZONE_MOVABLE], 56 NR_FREE_PAGES); 57 } 58 59 return pages; 60 } 61 62 static int pkmap_count[LAST_PKMAP]; 63 static unsigned int last_pkmap_nr; 64 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock); 65 66 pte_t * pkmap_page_table; 67 68 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait); 69 70 static void flush_all_zero_pkmaps(void) 71 { 72 int i; 73 74 flush_cache_kmaps(); 75 76 for (i = 0; i < LAST_PKMAP; i++) { 77 struct page *page; 78 79 /* 80 * zero means we don't have anything to do, 81 * >1 means that it is still in use. Only 82 * a count of 1 means that it is free but 83 * needs to be unmapped 84 */ 85 if (pkmap_count[i] != 1) 86 continue; 87 pkmap_count[i] = 0; 88 89 /* sanity check */ 90 BUG_ON(pte_none(pkmap_page_table[i])); 91 92 /* 93 * Don't need an atomic fetch-and-clear op here; 94 * no-one has the page mapped, and cannot get at 95 * its virtual address (and hence PTE) without first 96 * getting the kmap_lock (which is held here). 97 * So no dangers, even with speculative execution. 98 */ 99 page = pte_page(pkmap_page_table[i]); 100 pte_clear(&init_mm, (unsigned long)page_address(page), 101 &pkmap_page_table[i]); 102 103 set_page_address(page, NULL); 104 } 105 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP)); 106 } 107 108 /** 109 * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings 110 */ 111 void kmap_flush_unused(void) 112 { 113 spin_lock(&kmap_lock); 114 flush_all_zero_pkmaps(); 115 spin_unlock(&kmap_lock); 116 } 117 118 static inline unsigned long map_new_virtual(struct page *page) 119 { 120 unsigned long vaddr; 121 int count; 122 123 start: 124 count = LAST_PKMAP; 125 /* Find an empty entry */ 126 for (;;) { 127 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK; 128 if (!last_pkmap_nr) { 129 flush_all_zero_pkmaps(); 130 count = LAST_PKMAP; 131 } 132 if (!pkmap_count[last_pkmap_nr]) 133 break; /* Found a usable entry */ 134 if (--count) 135 continue; 136 137 /* 138 * Sleep for somebody else to unmap their entries 139 */ 140 { 141 DECLARE_WAITQUEUE(wait, current); 142 143 __set_current_state(TASK_UNINTERRUPTIBLE); 144 add_wait_queue(&pkmap_map_wait, &wait); 145 spin_unlock(&kmap_lock); 146 schedule(); 147 remove_wait_queue(&pkmap_map_wait, &wait); 148 spin_lock(&kmap_lock); 149 150 /* Somebody else might have mapped it while we slept */ 151 if (page_address(page)) 152 return (unsigned long)page_address(page); 153 154 /* Re-start */ 155 goto start; 156 } 157 } 158 vaddr = PKMAP_ADDR(last_pkmap_nr); 159 set_pte_at(&init_mm, vaddr, 160 &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot)); 161 162 pkmap_count[last_pkmap_nr] = 1; 163 set_page_address(page, (void *)vaddr); 164 165 return vaddr; 166 } 167 168 /** 169 * kmap_high - map a highmem page into memory 170 * @page: &struct page to map 171 * 172 * Returns the page's virtual memory address. 173 * 174 * We cannot call this from interrupts, as it may block. 175 */ 176 void *kmap_high(struct page *page) 177 { 178 unsigned long vaddr; 179 180 /* 181 * For highmem pages, we can't trust "virtual" until 182 * after we have the lock. 183 */ 184 spin_lock(&kmap_lock); 185 vaddr = (unsigned long)page_address(page); 186 if (!vaddr) 187 vaddr = map_new_virtual(page); 188 pkmap_count[PKMAP_NR(vaddr)]++; 189 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2); 190 spin_unlock(&kmap_lock); 191 return (void*) vaddr; 192 } 193 194 EXPORT_SYMBOL(kmap_high); 195 196 /** 197 * kunmap_high - map a highmem page into memory 198 * @page: &struct page to unmap 199 */ 200 void kunmap_high(struct page *page) 201 { 202 unsigned long vaddr; 203 unsigned long nr; 204 int need_wakeup; 205 206 spin_lock(&kmap_lock); 207 vaddr = (unsigned long)page_address(page); 208 BUG_ON(!vaddr); 209 nr = PKMAP_NR(vaddr); 210 211 /* 212 * A count must never go down to zero 213 * without a TLB flush! 214 */ 215 need_wakeup = 0; 216 switch (--pkmap_count[nr]) { 217 case 0: 218 BUG(); 219 case 1: 220 /* 221 * Avoid an unnecessary wake_up() function call. 222 * The common case is pkmap_count[] == 1, but 223 * no waiters. 224 * The tasks queued in the wait-queue are guarded 225 * by both the lock in the wait-queue-head and by 226 * the kmap_lock. As the kmap_lock is held here, 227 * no need for the wait-queue-head's lock. Simply 228 * test if the queue is empty. 229 */ 230 need_wakeup = waitqueue_active(&pkmap_map_wait); 231 } 232 spin_unlock(&kmap_lock); 233 234 /* do wake-up, if needed, race-free outside of the spin lock */ 235 if (need_wakeup) 236 wake_up(&pkmap_map_wait); 237 } 238 239 EXPORT_SYMBOL(kunmap_high); 240 #endif 241 242 #if defined(HASHED_PAGE_VIRTUAL) 243 244 #define PA_HASH_ORDER 7 245 246 /* 247 * Describes one page->virtual association 248 */ 249 struct page_address_map { 250 struct page *page; 251 void *virtual; 252 struct list_head list; 253 }; 254 255 /* 256 * page_address_map freelist, allocated from page_address_maps. 257 */ 258 static struct list_head page_address_pool; /* freelist */ 259 static spinlock_t pool_lock; /* protects page_address_pool */ 260 261 /* 262 * Hash table bucket 263 */ 264 static struct page_address_slot { 265 struct list_head lh; /* List of page_address_maps */ 266 spinlock_t lock; /* Protect this bucket's list */ 267 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER]; 268 269 static struct page_address_slot *page_slot(struct page *page) 270 { 271 return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)]; 272 } 273 274 /** 275 * page_address - get the mapped virtual address of a page 276 * @page: &struct page to get the virtual address of 277 * 278 * Returns the page's virtual address. 279 */ 280 void *page_address(struct page *page) 281 { 282 unsigned long flags; 283 void *ret; 284 struct page_address_slot *pas; 285 286 if (!PageHighMem(page)) 287 return lowmem_page_address(page); 288 289 pas = page_slot(page); 290 ret = NULL; 291 spin_lock_irqsave(&pas->lock, flags); 292 if (!list_empty(&pas->lh)) { 293 struct page_address_map *pam; 294 295 list_for_each_entry(pam, &pas->lh, list) { 296 if (pam->page == page) { 297 ret = pam->virtual; 298 goto done; 299 } 300 } 301 } 302 done: 303 spin_unlock_irqrestore(&pas->lock, flags); 304 return ret; 305 } 306 307 EXPORT_SYMBOL(page_address); 308 309 /** 310 * set_page_address - set a page's virtual address 311 * @page: &struct page to set 312 * @virtual: virtual address to use 313 */ 314 void set_page_address(struct page *page, void *virtual) 315 { 316 unsigned long flags; 317 struct page_address_slot *pas; 318 struct page_address_map *pam; 319 320 BUG_ON(!PageHighMem(page)); 321 322 pas = page_slot(page); 323 if (virtual) { /* Add */ 324 BUG_ON(list_empty(&page_address_pool)); 325 326 spin_lock_irqsave(&pool_lock, flags); 327 pam = list_entry(page_address_pool.next, 328 struct page_address_map, list); 329 list_del(&pam->list); 330 spin_unlock_irqrestore(&pool_lock, flags); 331 332 pam->page = page; 333 pam->virtual = virtual; 334 335 spin_lock_irqsave(&pas->lock, flags); 336 list_add_tail(&pam->list, &pas->lh); 337 spin_unlock_irqrestore(&pas->lock, flags); 338 } else { /* Remove */ 339 spin_lock_irqsave(&pas->lock, flags); 340 list_for_each_entry(pam, &pas->lh, list) { 341 if (pam->page == page) { 342 list_del(&pam->list); 343 spin_unlock_irqrestore(&pas->lock, flags); 344 spin_lock_irqsave(&pool_lock, flags); 345 list_add_tail(&pam->list, &page_address_pool); 346 spin_unlock_irqrestore(&pool_lock, flags); 347 goto done; 348 } 349 } 350 spin_unlock_irqrestore(&pas->lock, flags); 351 } 352 done: 353 return; 354 } 355 356 static struct page_address_map page_address_maps[LAST_PKMAP]; 357 358 void __init page_address_init(void) 359 { 360 int i; 361 362 INIT_LIST_HEAD(&page_address_pool); 363 for (i = 0; i < ARRAY_SIZE(page_address_maps); i++) 364 list_add(&page_address_maps[i].list, &page_address_pool); 365 for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) { 366 INIT_LIST_HEAD(&page_address_htable[i].lh); 367 spin_lock_init(&page_address_htable[i].lock); 368 } 369 spin_lock_init(&pool_lock); 370 } 371 372 #endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */ 373