mm/highmem.c

   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 <asm/tlbflush.h>
  30
  31 /*
  32  * Virtual_count is not a pure "count".
  33  *  0 means that it is not mapped, and has not been mapped
  34  *    since a TLB flush - it is usable.
  35  *  1 means that there are no users, but it has been mapped
  36  *    since the last TLB flush - so we can't use it.
  37  *  n means that there are (n-1) current users of it.
  38  */
  39 #ifdef CONFIG_HIGHMEM
  40
  41 unsigned long totalhigh_pages __read_mostly;
  42 EXPORT_SYMBOL(totalhigh_pages);
  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 /*
  70  * Most architectures have no use for kmap_high_get(), so let's abstract
  71  * the disabling of IRQ out of the locking in that case to save on a
  72  * potential useless overhead.
  73  */
  74 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
  75 #define lock_kmap()             spin_lock_irq(&kmap_lock)
  76 #define unlock_kmap()           spin_unlock_irq(&kmap_lock)
  77 #define lock_kmap_any(flags)    spin_lock_irqsave(&kmap_lock, flags)
  78 #define unlock_kmap_any(flags)  spin_unlock_irqrestore(&kmap_lock, flags)
  79 #else
  80 #define lock_kmap()             spin_lock(&kmap_lock)
  81 #define unlock_kmap()           spin_unlock(&kmap_lock)
  82 #define lock_kmap_any(flags)    \
  83                 do { spin_lock(&kmap_lock); (void)(flags); } while (0)
  84 #define unlock_kmap_any(flags)  \
  85                 do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
  86 #endif
  87
  88 static void flush_all_zero_pkmaps(void)
  89 {
  90         int i;
  91         int need_flush = 0;
  92
  93         flush_cache_kmaps();
  94
  95         for (i = 0; i < LAST_PKMAP; i++) {
  96                 struct page *page;
  97
  98                 /*
  99                  * zero means we don't have anything to do,
 100                  * >1 means that it is still in use. Only
 101                  * a count of 1 means that it is free but
 102                  * needs to be unmapped
 103                  */
 104                 if (pkmap_count[i] != 1)
 105                         continue;
 106                 pkmap_count[i] = 0;
 107
 108                 /* sanity check */
 109                 BUG_ON(pte_none(pkmap_page_table[i]));
 110
 111                 /*
 112                  * Don't need an atomic fetch-and-clear op here;
 113                  * no-one has the page mapped, and cannot get at
 114                  * its virtual address (and hence PTE) without first
 115                  * getting the kmap_lock (which is held here).
 116                  * So no dangers, even with speculative execution.
 117                  */
 118                 page = pte_page(pkmap_page_table[i]);
 119                 pte_clear(&init_mm, (unsigned long)page_address(page),
 120                           &pkmap_page_table[i]);
 121
 122                 set_page_address(page, NULL);
 123                 need_flush = 1;
 124         }
 125         if (need_flush)
 126                 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
 127 }
 128
 129 /**
 130  * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
 131  */
 132 void kmap_flush_unused(void)
 133 {
 134         lock_kmap();
 135         flush_all_zero_pkmaps();
 136         unlock_kmap();
 137 }
 138
 139 static inline unsigned long map_new_virtual(struct page *page)
 140 {
 141         unsigned long vaddr;
 142         int count;
 143
 144 start:
 145         count = LAST_PKMAP;
 146         /* Find an empty entry */
 147         for (;;) {
 148                 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
 149                 if (!last_pkmap_nr) {
 150                         flush_all_zero_pkmaps();
 151                         count = LAST_PKMAP;
 152                 }
 153                 if (!pkmap_count[last_pkmap_nr])
 154                         break;  /* Found a usable entry */
 155                 if (--count)
 156                         continue;
 157
 158                 /*
 159                  * Sleep for somebody else to unmap their entries
 160                  */
 161                 {
 162                         DECLARE_WAITQUEUE(wait, current);
 163
 164                         __set_current_state(TASK_UNINTERRUPTIBLE);
 165                         add_wait_queue(&pkmap_map_wait, &wait);
 166                         unlock_kmap();
 167                         schedule();
 168                         remove_wait_queue(&pkmap_map_wait, &wait);
 169                         lock_kmap();
 170
 171                         /* Somebody else might have mapped it while we slept */
 172                         if (page_address(page))
 173                                 return (unsigned long)page_address(page);
 174
 175                         /* Re-start */
 176                         goto start;
 177                 }
 178         }
 179         vaddr = PKMAP_ADDR(last_pkmap_nr);
 180         set_pte_at(&init_mm, vaddr,
 181                    &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
 182
 183         pkmap_count[last_pkmap_nr] = 1;
 184         set_page_address(page, (void *)vaddr);
 185
 186         return vaddr;
 187 }
 188
 189 /**
 190  * kmap_high - map a highmem page into memory
 191  * @page: &struct page to map
 192  *
 193  * Returns the page's virtual memory address.
 194  *
 195  * We cannot call this from interrupts, as it may block.
 196  */
 197 void *kmap_high(struct page *page)
 198 {
 199         unsigned long vaddr;
 200
 201         /*
 202          * For highmem pages, we can't trust "virtual" until
 203          * after we have the lock.
 204          */
 205         lock_kmap();
 206         vaddr = (unsigned long)page_address(page);
 207         if (!vaddr)
 208                 vaddr = map_new_virtual(page);
 209         pkmap_count[PKMAP_NR(vaddr)]++;
 210         BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
 211         unlock_kmap();
 212         return (void*) vaddr;
 213 }
 214
 215 EXPORT_SYMBOL(kmap_high);
 216
 217 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
 218 /**
 219  * kmap_high_get - pin a highmem page into memory
 220  * @page: &struct page to pin
 221  *
 222  * Returns the page's current virtual memory address, or NULL if no mapping
 223  * exists.  When and only when a non null address is returned then a
 224  * matching call to kunmap_high() is necessary.
 225  *
 226  * This can be called from any context.
 227  */
 228 void *kmap_high_get(struct page *page)
 229 {
 230         unsigned long vaddr, flags;
 231
 232         lock_kmap_any(flags);
 233         vaddr = (unsigned long)page_address(page);
 234         if (vaddr) {
 235                 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
 236                 pkmap_count[PKMAP_NR(vaddr)]++;
 237         }
 238         unlock_kmap_any(flags);
 239         return (void*) vaddr;
 240 }
 241 #endif
 242
 243 /**
 244  * kunmap_high - map a highmem page into memory
 245  * @page: &struct page to unmap
 246  *
 247  * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
 248  * only from user context.
 249  */
 250 void kunmap_high(struct page *page)
 251 {
 252         unsigned long vaddr;
 253         unsigned long nr;
 254         unsigned long flags;
 255         int need_wakeup;
 256
 257         lock_kmap_any(flags);
 258         vaddr = (unsigned long)page_address(page);
 259         BUG_ON(!vaddr);
 260         nr = PKMAP_NR(vaddr);
 261
 262         /*
 263          * A count must never go down to zero
 264          * without a TLB flush!
 265          */
 266         need_wakeup = 0;
 267         switch (--pkmap_count[nr]) {
 268         case 0:
 269                 BUG();
 270         case 1:
 271                 /*
 272                  * Avoid an unnecessary wake_up() function call.
 273                  * The common case is pkmap_count[] == 1, but
 274                  * no waiters.
 275                  * The tasks queued in the wait-queue are guarded
 276                  * by both the lock in the wait-queue-head and by
 277                  * the kmap_lock.  As the kmap_lock is held here,
 278                  * no need for the wait-queue-head's lock.  Simply
 279                  * test if the queue is empty.
 280                  */
 281                 need_wakeup = waitqueue_active(&pkmap_map_wait);
 282         }
 283         unlock_kmap_any(flags);
 284
 285         /* do wake-up, if needed, race-free outside of the spin lock */
 286         if (need_wakeup)
 287                 wake_up(&pkmap_map_wait);
 288 }
 289
 290 EXPORT_SYMBOL(kunmap_high);
 291 #endif
 292
 293 #if defined(HASHED_PAGE_VIRTUAL)
 294
 295 #define PA_HASH_ORDER   7
 296
 297 /*
 298  * Describes one page->virtual association
 299  */
 300 struct page_address_map {
 301         struct page *page;
 302         void *virtual;
 303         struct list_head list;
 304 };
 305
 306 /*
 307  * page_address_map freelist, allocated from page_address_maps.
 308  */
 309 static struct list_head page_address_pool;      /* freelist */
 310 static spinlock_t pool_lock;                    /* protects page_address_pool */
 311
 312 /*
 313  * Hash table bucket
 314  */
 315 static struct page_address_slot {
 316         struct list_head lh;                    /* List of page_address_maps */
 317         spinlock_t lock;                        /* Protect this bucket's list */
 318 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
 319
 320 static struct page_address_slot *page_slot(struct page *page)
 321 {
 322         return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
 323 }
 324
 325 /**
 326  * page_address - get the mapped virtual address of a page
 327  * @page: &struct page to get the virtual address of
 328  *
 329  * Returns the page's virtual address.
 330  */
 331 void *page_address(struct page *page)
 332 {
 333         unsigned long flags;
 334         void *ret;
 335         struct page_address_slot *pas;
 336
 337         if (!PageHighMem(page))
 338                 return lowmem_page_address(page);
 339
 340         pas = page_slot(page);
 341         ret = NULL;
 342         spin_lock_irqsave(&pas->lock, flags);
 343         if (!list_empty(&pas->lh)) {
 344                 struct page_address_map *pam;
 345
 346                 list_for_each_entry(pam, &pas->lh, list) {
 347                         if (pam->page == page) {
 348                                 ret = pam->virtual;
 349                                 goto done;
 350                         }
 351                 }
 352         }
 353 done:
 354         spin_unlock_irqrestore(&pas->lock, flags);
 355         return ret;
 356 }
 357
 358 EXPORT_SYMBOL(page_address);
 359
 360 /**
 361  * set_page_address - set a page's virtual address
 362  * @page: &struct page to set
 363  * @virtual: virtual address to use
 364  */
 365 void set_page_address(struct page *page, void *virtual)
 366 {
 367         unsigned long flags;
 368         struct page_address_slot *pas;
 369         struct page_address_map *pam;
 370
 371         BUG_ON(!PageHighMem(page));
 372
 373         pas = page_slot(page);
 374         if (virtual) {          /* Add */
 375                 BUG_ON(list_empty(&page_address_pool));
 376
 377                 spin_lock_irqsave(&pool_lock, flags);
 378                 pam = list_entry(page_address_pool.next,
 379                                 struct page_address_map, list);
 380                 list_del(&pam->list);
 381                 spin_unlock_irqrestore(&pool_lock, flags);
 382
 383                 pam->page = page;
 384                 pam->virtual = virtual;
 385
 386                 spin_lock_irqsave(&pas->lock, flags);
 387                 list_add_tail(&pam->list, &pas->lh);
 388                 spin_unlock_irqrestore(&pas->lock, flags);
 389         } else {                /* Remove */
 390                 spin_lock_irqsave(&pas->lock, flags);
 391                 list_for_each_entry(pam, &pas->lh, list) {
 392                         if (pam->page == page) {
 393                                 list_del(&pam->list);
 394                                 spin_unlock_irqrestore(&pas->lock, flags);
 395                                 spin_lock_irqsave(&pool_lock, flags);
 396                                 list_add_tail(&pam->list, &page_address_pool);
 397                                 spin_unlock_irqrestore(&pool_lock, flags);
 398                                 goto done;
 399                         }
 400                 }
 401                 spin_unlock_irqrestore(&pas->lock, flags);
 402         }
 403 done:
 404         return;
 405 }
 406
 407 static struct page_address_map page_address_maps[LAST_PKMAP];
 408
 409 void __init page_address_init(void)
 410 {
 411         int i;
 412
 413         INIT_LIST_HEAD(&page_address_pool);
 414         for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)
 415                 list_add(&page_address_maps[i].list, &page_address_pool);
 416         for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
 417                 INIT_LIST_HEAD(&page_address_htable[i].lh);
 418                 spin_lock_init(&page_address_htable[i].lock);
 419         }
 420         spin_lock_init(&pool_lock);
 421 }
 422
 423 #endif  /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */
 424
 425 #if defined(CONFIG_DEBUG_HIGHMEM) && defined(CONFIG_TRACE_IRQFLAGS_SUPPORT)
 426
 427 void debug_kmap_atomic(enum km_type type)
 428 {
 429         static unsigned warn_count = 10;
 430
 431         if (unlikely(warn_count == 0))
 432                 return;
 433
 434         if (unlikely(in_interrupt())) {
 435                 if (in_irq()) {
 436                         if (type != KM_IRQ0 && type != KM_IRQ1 &&
 437                             type != KM_BIO_SRC_IRQ && type != KM_BIO_DST_IRQ &&
 438                             type != KM_BOUNCE_READ) {
 439                                 WARN_ON(1);
 440                                 warn_count--;
 441                         }
 442                 } else if (!irqs_disabled()) {  /* softirq */
 443                         if (type != KM_IRQ0 && type != KM_IRQ1 &&
 444                             type != KM_SOFTIRQ0 && type != KM_SOFTIRQ1 &&
 445                             type != KM_SKB_SUNRPC_DATA &&
 446                             type != KM_SKB_DATA_SOFTIRQ &&
 447                             type != KM_BOUNCE_READ) {
 448                                 WARN_ON(1);
 449                                 warn_count--;
 450                         }
 451                 }
 452         }
 453
 454         if (type == KM_IRQ0 || type == KM_IRQ1 || type == KM_BOUNCE_READ ||
 455                         type == KM_BIO_SRC_IRQ || type == KM_BIO_DST_IRQ) {
 456                 if (!irqs_disabled()) {
 457                         WARN_ON(1);
 458                         warn_count--;
 459                 }
 460         } else if (type == KM_SOFTIRQ0 || type == KM_SOFTIRQ1) {
 461                 if (irq_count() == 0 && !irqs_disabled()) {
 462                         WARN_ON(1);
 463                         warn_count--;
 464                 }
 465         }
 466 }
 467
 468 #endif