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