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