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