git.oblomov.eu Git - linux-2.6/blob - 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 static mempool_t *page_pool, *isa_page_pool;
  32
  33 static void *page_pool_alloc(unsigned int __nocast gfp_mask, void *data)
  34 {
  35         unsigned int gfp = gfp_mask | (unsigned int) (long) data;
  36
  37         return alloc_page(gfp);
  38 }
  39
  40 static void page_pool_free(void *page, void *data)
  41 {
  42         __free_page(page);
  43 }
  44
  45 /*
  46  * Virtual_count is not a pure "count".
  47  *  0 means that it is not mapped, and has not been mapped
  48  *    since a TLB flush - it is usable.
  49  *  1 means that there are no users, but it has been mapped
  50  *    since the last TLB flush - so we can't use it.
  51  *  n means that there are (n-1) current users of it.
  52  */
  53 #ifdef CONFIG_HIGHMEM
  54 static int pkmap_count[LAST_PKMAP];
  55 static unsigned int last_pkmap_nr;
  56 static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
  57
  58 pte_t * pkmap_page_table;
  59
  60 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
  61
  62 static void flush_all_zero_pkmaps(void)
  63 {
  64         int i;
  65
  66         flush_cache_kmaps();
  67
  68         for (i = 0; i < LAST_PKMAP; i++) {
  69                 struct page *page;
  70
  71                 /*
  72                  * zero means we don't have anything to do,
  73                  * >1 means that it is still in use. Only
  74                  * a count of 1 means that it is free but
  75                  * needs to be unmapped
  76                  */
  77                 if (pkmap_count[i] != 1)
  78                         continue;
  79                 pkmap_count[i] = 0;
  80
  81                 /* sanity check */
  82                 if (pte_none(pkmap_page_table[i]))
  83                         BUG();
  84
  85                 /*
  86                  * Don't need an atomic fetch-and-clear op here;
  87                  * no-one has the page mapped, and cannot get at
  88                  * its virtual address (and hence PTE) without first
  89                  * getting the kmap_lock (which is held here).
  90                  * So no dangers, even with speculative execution.
  91                  */
  92                 page = pte_page(pkmap_page_table[i]);
  93                 pte_clear(&init_mm, (unsigned long)page_address(page),
  94                           &pkmap_page_table[i]);
  95
  96                 set_page_address(page, NULL);
  97         }
  98         flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
  99 }
 100
 101 static inline unsigned long map_new_virtual(struct page *page)
 102 {
 103         unsigned long vaddr;
 104         int count;
 105
 106 start:
 107         count = LAST_PKMAP;
 108         /* Find an empty entry */
 109         for (;;) {
 110                 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
 111                 if (!last_pkmap_nr) {
 112                         flush_all_zero_pkmaps();
 113                         count = LAST_PKMAP;
 114                 }
 115                 if (!pkmap_count[last_pkmap_nr])
 116                         break;  /* Found a usable entry */
 117                 if (--count)
 118                         continue;
 119
 120                 /*
 121                  * Sleep for somebody else to unmap their entries
 122                  */
 123                 {
 124                         DECLARE_WAITQUEUE(wait, current);
 125
 126                         __set_current_state(TASK_UNINTERRUPTIBLE);
 127                         add_wait_queue(&pkmap_map_wait, &wait);
 128                         spin_unlock(&kmap_lock);
 129                         schedule();
 130                         remove_wait_queue(&pkmap_map_wait, &wait);
 131                         spin_lock(&kmap_lock);
 132
 133                         /* Somebody else might have mapped it while we slept */
 134                         if (page_address(page))
 135                                 return (unsigned long)page_address(page);
 136
 137                         /* Re-start */
 138                         goto start;
 139                 }
 140         }
 141         vaddr = PKMAP_ADDR(last_pkmap_nr);
 142         set_pte_at(&init_mm, vaddr,
 143                    &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
 144
 145         pkmap_count[last_pkmap_nr] = 1;
 146         set_page_address(page, (void *)vaddr);
 147
 148         return vaddr;
 149 }
 150
 151 void fastcall *kmap_high(struct page *page)
 152 {
 153         unsigned long vaddr;
 154
 155         /*
 156          * For highmem pages, we can't trust "virtual" until
 157          * after we have the lock.
 158          *
 159          * We cannot call this from interrupts, as it may block
 160          */
 161         spin_lock(&kmap_lock);
 162         vaddr = (unsigned long)page_address(page);
 163         if (!vaddr)
 164                 vaddr = map_new_virtual(page);
 165         pkmap_count[PKMAP_NR(vaddr)]++;
 166         if (pkmap_count[PKMAP_NR(vaddr)] < 2)
 167                 BUG();
 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         if (!vaddr)
 183                 BUG();
 184         nr = PKMAP_NR(vaddr);
 185
 186         /*
 187          * A count must never go down to zero
 188          * without a TLB flush!
 189          */
 190         need_wakeup = 0;
 191         switch (--pkmap_count[nr]) {
 192         case 0:
 193                 BUG();
 194         case 1:
 195                 /*
 196                  * Avoid an unnecessary wake_up() function call.
 197                  * The common case is pkmap_count[] == 1, but
 198                  * no waiters.
 199                  * The tasks queued in the wait-queue are guarded
 200                  * by both the lock in the wait-queue-head and by
 201                  * the kmap_lock.  As the kmap_lock is held here,
 202                  * no need for the wait-queue-head's lock.  Simply
 203                  * test if the queue is empty.
 204                  */
 205                 need_wakeup = waitqueue_active(&pkmap_map_wait);
 206         }
 207         spin_unlock(&kmap_lock);
 208
 209         /* do wake-up, if needed, race-free outside of the spin lock */
 210         if (need_wakeup)
 211                 wake_up(&pkmap_map_wait);
 212 }
 213
 214 EXPORT_SYMBOL(kunmap_high);
 215
 216 #define POOL_SIZE       64
 217
 218 static __init int init_emergency_pool(void)
 219 {
 220         struct sysinfo i;
 221         si_meminfo(&i);
 222         si_swapinfo(&i);
 223
 224         if (!i.totalhigh)
 225                 return 0;
 226
 227         page_pool = mempool_create(POOL_SIZE, page_pool_alloc, page_pool_free, NULL);
 228         if (!page_pool)
 229                 BUG();
 230         printk("highmem bounce pool size: %d pages\n", POOL_SIZE);
 231
 232         return 0;
 233 }
 234
 235 __initcall(init_emergency_pool);
 236
 237 /*
 238  * highmem version, map in to vec
 239  */
 240 static void bounce_copy_vec(struct bio_vec *to, unsigned char *vfrom)
 241 {
 242         unsigned long flags;
 243         unsigned char *vto;
 244
 245         local_irq_save(flags);
 246         vto = kmap_atomic(to->bv_page, KM_BOUNCE_READ);
 247         memcpy(vto + to->bv_offset, vfrom, to->bv_len);
 248         kunmap_atomic(vto, KM_BOUNCE_READ);
 249         local_irq_restore(flags);
 250 }
 251
 252 #else /* CONFIG_HIGHMEM */
 253
 254 #define bounce_copy_vec(to, vfrom)      \
 255         memcpy(page_address((to)->bv_page) + (to)->bv_offset, vfrom, (to)->bv_len)
 256
 257 #endif
 258
 259 #define ISA_POOL_SIZE   16
 260
 261 /*
 262  * gets called "every" time someone init's a queue with BLK_BOUNCE_ISA
 263  * as the max address, so check if the pool has already been created.
 264  */
 265 int init_emergency_isa_pool(void)
 266 {
 267         if (isa_page_pool)
 268                 return 0;
 269
 270         isa_page_pool = mempool_create(ISA_POOL_SIZE, page_pool_alloc, page_pool_free, (void *) __GFP_DMA);
 271         if (!isa_page_pool)
 272                 BUG();
 273
 274         printk("isa bounce pool size: %d pages\n", ISA_POOL_SIZE);
 275         return 0;
 276 }
 277
 278 /*
 279  * Simple bounce buffer support for highmem pages. Depending on the
 280  * queue gfp mask set, *to may or may not be a highmem page. kmap it
 281  * always, it will do the Right Thing
 282  */
 283 static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
 284 {
 285         unsigned char *vfrom;
 286         struct bio_vec *tovec, *fromvec;
 287         int i;
 288
 289         __bio_for_each_segment(tovec, to, i, 0) {
 290                 fromvec = from->bi_io_vec + i;
 291
 292                 /*
 293                  * not bounced
 294                  */
 295                 if (tovec->bv_page == fromvec->bv_page)
 296                         continue;
 297
 298                 /*
 299                  * fromvec->bv_offset and fromvec->bv_len might have been
 300                  * modified by the block layer, so use the original copy,
 301                  * bounce_copy_vec already uses tovec->bv_len
 302                  */
 303                 vfrom = page_address(fromvec->bv_page) + tovec->bv_offset;
 304
 305                 flush_dcache_page(tovec->bv_page);
 306                 bounce_copy_vec(tovec, vfrom);
 307         }
 308 }
 309
 310 static void bounce_end_io(struct bio *bio, mempool_t *pool, int err)
 311 {
 312         struct bio *bio_orig = bio->bi_private;
 313         struct bio_vec *bvec, *org_vec;
 314         int i;
 315
 316         if (test_bit(BIO_EOPNOTSUPP, &bio->bi_flags))
 317                 set_bit(BIO_EOPNOTSUPP, &bio_orig->bi_flags);
 318
 319         /*
 320          * free up bounce indirect pages used
 321          */
 322         __bio_for_each_segment(bvec, bio, i, 0) {
 323                 org_vec = bio_orig->bi_io_vec + i;
 324                 if (bvec->bv_page == org_vec->bv_page)
 325                         continue;
 326
 327                 mempool_free(bvec->bv_page, pool);
 328         }
 329
 330         bio_endio(bio_orig, bio_orig->bi_size, err);
 331         bio_put(bio);
 332 }
 333
 334 static int bounce_end_io_write(struct bio *bio, unsigned int bytes_done,int err)
 335 {
 336         if (bio->bi_size)
 337                 return 1;
 338
 339         bounce_end_io(bio, page_pool, err);
 340         return 0;
 341 }
 342
 343 static int bounce_end_io_write_isa(struct bio *bio, unsigned int bytes_done, int err)
 344 {
 345         if (bio->bi_size)
 346                 return 1;
 347
 348         bounce_end_io(bio, isa_page_pool, err);
 349         return 0;
 350 }
 351
 352 static void __bounce_end_io_read(struct bio *bio, mempool_t *pool, int err)
 353 {
 354         struct bio *bio_orig = bio->bi_private;
 355
 356         if (test_bit(BIO_UPTODATE, &bio->bi_flags))
 357                 copy_to_high_bio_irq(bio_orig, bio);
 358
 359         bounce_end_io(bio, pool, err);
 360 }
 361
 362 static int bounce_end_io_read(struct bio *bio, unsigned int bytes_done, int err)
 363 {
 364         if (bio->bi_size)
 365                 return 1;
 366
 367         __bounce_end_io_read(bio, page_pool, err);
 368         return 0;
 369 }
 370
 371 static int bounce_end_io_read_isa(struct bio *bio, unsigned int bytes_done, int err)
 372 {
 373         if (bio->bi_size)
 374                 return 1;
 375
 376         __bounce_end_io_read(bio, isa_page_pool, err);
 377         return 0;
 378 }
 379
 380 static void __blk_queue_bounce(request_queue_t *q, struct bio **bio_orig,
 381                         mempool_t *pool)
 382 {
 383         struct page *page;
 384         struct bio *bio = NULL;
 385         int i, rw = bio_data_dir(*bio_orig);
 386         struct bio_vec *to, *from;
 387
 388         bio_for_each_segment(from, *bio_orig, i) {
 389                 page = from->bv_page;
 390
 391                 /*
 392                  * is destination page below bounce pfn?
 393                  */
 394                 if (page_to_pfn(page) < q->bounce_pfn)
 395                         continue;
 396
 397                 /*
 398                  * irk, bounce it
 399                  */
 400                 if (!bio)
 401                         bio = bio_alloc(GFP_NOIO, (*bio_orig)->bi_vcnt);
 402
 403                 to = bio->bi_io_vec + i;
 404
 405                 to->bv_page = mempool_alloc(pool, q->bounce_gfp);
 406                 to->bv_len = from->bv_len;
 407                 to->bv_offset = from->bv_offset;
 408
 409                 if (rw == WRITE) {
 410                         char *vto, *vfrom;
 411
 412                         flush_dcache_page(from->bv_page);
 413                         vto = page_address(to->bv_page) + to->bv_offset;
 414                         vfrom = kmap(from->bv_page) + from->bv_offset;
 415                         memcpy(vto, vfrom, to->bv_len);
 416                         kunmap(from->bv_page);
 417                 }
 418         }
 419
 420         /*
 421          * no pages bounced
 422          */
 423         if (!bio)
 424                 return;
 425
 426         /*
 427          * at least one page was bounced, fill in possible non-highmem
 428          * pages
 429          */
 430         __bio_for_each_segment(from, *bio_orig, i, 0) {
 431                 to = bio_iovec_idx(bio, i);
 432                 if (!to->bv_page) {
 433                         to->bv_page = from->bv_page;
 434                         to->bv_len = from->bv_len;
 435                         to->bv_offset = from->bv_offset;
 436                 }
 437         }
 438
 439         bio->bi_bdev = (*bio_orig)->bi_bdev;
 440         bio->bi_flags |= (1 << BIO_BOUNCED);
 441         bio->bi_sector = (*bio_orig)->bi_sector;
 442         bio->bi_rw = (*bio_orig)->bi_rw;
 443
 444         bio->bi_vcnt = (*bio_orig)->bi_vcnt;
 445         bio->bi_idx = (*bio_orig)->bi_idx;
 446         bio->bi_size = (*bio_orig)->bi_size;
 447
 448         if (pool == page_pool) {
 449                 bio->bi_end_io = bounce_end_io_write;
 450                 if (rw == READ)
 451                         bio->bi_end_io = bounce_end_io_read;
 452         } else {
 453                 bio->bi_end_io = bounce_end_io_write_isa;
 454                 if (rw == READ)
 455                         bio->bi_end_io = bounce_end_io_read_isa;
 456         }
 457
 458         bio->bi_private = *bio_orig;
 459         *bio_orig = bio;
 460 }
 461
 462 void blk_queue_bounce(request_queue_t *q, struct bio **bio_orig)
 463 {
 464         mempool_t *pool;
 465
 466         /*
 467          * for non-isa bounce case, just check if the bounce pfn is equal
 468          * to or bigger than the highest pfn in the system -- in that case,
 469          * don't waste time iterating over bio segments
 470          */
 471         if (!(q->bounce_gfp & GFP_DMA)) {
 472                 if (q->bounce_pfn >= blk_max_pfn)
 473                         return;
 474                 pool = page_pool;
 475         } else {
 476                 BUG_ON(!isa_page_pool);
 477                 pool = isa_page_pool;
 478         }
 479
 480         /*
 481          * slow path
 482          */
 483         __blk_queue_bounce(q, bio_orig, pool);
 484 }
 485
 486 EXPORT_SYMBOL(blk_queue_bounce);
 487
 488 #if defined(HASHED_PAGE_VIRTUAL)
 489
 490 #define PA_HASH_ORDER   7
 491
 492 /*
 493  * Describes one page->virtual association
 494  */
 495 struct page_address_map {
 496         struct page *page;
 497         void *virtual;
 498         struct list_head list;
 499 };
 500
 501 /*
 502  * page_address_map freelist, allocated from page_address_maps.
 503  */
 504 static struct list_head page_address_pool;      /* freelist */
 505 static spinlock_t pool_lock;                    /* protects page_address_pool */
 506
 507 /*
 508  * Hash table bucket
 509  */
 510 static struct page_address_slot {
 511         struct list_head lh;                    /* List of page_address_maps */
 512         spinlock_t lock;                        /* Protect this bucket's list */
 513 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
 514
 515 static struct page_address_slot *page_slot(struct page *page)
 516 {
 517         return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
 518 }
 519
 520 void *page_address(struct page *page)
 521 {
 522         unsigned long flags;
 523         void *ret;
 524         struct page_address_slot *pas;
 525
 526         if (!PageHighMem(page))
 527                 return lowmem_page_address(page);
 528
 529         pas = page_slot(page);
 530         ret = NULL;
 531         spin_lock_irqsave(&pas->lock, flags);
 532         if (!list_empty(&pas->lh)) {
 533                 struct page_address_map *pam;
 534
 535                 list_for_each_entry(pam, &pas->lh, list) {
 536                         if (pam->page == page) {
 537                                 ret = pam->virtual;
 538                                 goto done;
 539                         }
 540                 }
 541         }
 542 done:
 543         spin_unlock_irqrestore(&pas->lock, flags);
 544         return ret;
 545 }
 546
 547 EXPORT_SYMBOL(page_address);
 548
 549 void set_page_address(struct page *page, void *virtual)
 550 {
 551         unsigned long flags;
 552         struct page_address_slot *pas;
 553         struct page_address_map *pam;
 554
 555         BUG_ON(!PageHighMem(page));
 556
 557         pas = page_slot(page);
 558         if (virtual) {          /* Add */
 559                 BUG_ON(list_empty(&page_address_pool));
 560
 561                 spin_lock_irqsave(&pool_lock, flags);
 562                 pam = list_entry(page_address_pool.next,
 563                                 struct page_address_map, list);
 564                 list_del(&pam->list);
 565                 spin_unlock_irqrestore(&pool_lock, flags);
 566
 567                 pam->page = page;
 568                 pam->virtual = virtual;
 569
 570                 spin_lock_irqsave(&pas->lock, flags);
 571                 list_add_tail(&pam->list, &pas->lh);
 572                 spin_unlock_irqrestore(&pas->lock, flags);
 573         } else {                /* Remove */
 574                 spin_lock_irqsave(&pas->lock, flags);
 575                 list_for_each_entry(pam, &pas->lh, list) {
 576                         if (pam->page == page) {
 577                                 list_del(&pam->list);
 578                                 spin_unlock_irqrestore(&pas->lock, flags);
 579                                 spin_lock_irqsave(&pool_lock, flags);
 580                                 list_add_tail(&pam->list, &page_address_pool);
 581                                 spin_unlock_irqrestore(&pool_lock, flags);
 582                                 goto done;
 583                         }
 584                 }
 585                 spin_unlock_irqrestore(&pas->lock, flags);
 586         }
 587 done:
 588         return;
 589 }
 590
 591 static struct page_address_map page_address_maps[LAST_PKMAP];
 592
 593 void __init page_address_init(void)
 594 {
 595         int i;
 596
 597         INIT_LIST_HEAD(&page_address_pool);
 598         for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)
 599                 list_add(&page_address_maps[i].list, &page_address_pool);
 600         for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
 601                 INIT_LIST_HEAD(&page_address_htable[i].lh);
 602                 spin_lock_init(&page_address_htable[i].lock);
 603         }
 604         spin_lock_init(&pool_lock);
 605 }
 606
 607 #endif  /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */