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/pgalloc.h>
  30 #include <asm/tlbflush.h>
  31
  32 static mempool_t *page_pool, *isa_page_pool;
  33
  34 static void *page_pool_alloc(int gfp_mask, void *data)
  35 {
  36         int gfp = gfp_mask | (int) (long) data;
  37
  38         return alloc_page(gfp);
  39 }
  40
  41 static void page_pool_free(void *page, void *data)
  42 {
  43         __free_page(page);
  44 }
  45
  46 /*
  47  * Virtual_count is not a pure "count".
  48  *  0 means that it is not mapped, and has not been mapped
  49  *    since a TLB flush - it is usable.
  50  *  1 means that there are no users, but it has been mapped
  51  *    since the last TLB flush - so we can't use it.
  52  *  n means that there are (n-1) current users of it.
  53  */
  54 #ifdef CONFIG_HIGHMEM
  55 static int pkmap_count[LAST_PKMAP];
  56 static unsigned int last_pkmap_nr;
  57 static spinlock_t kmap_lock __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
  58
  59 pte_t * pkmap_page_table;
  60
  61 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
  62
  63 static void flush_all_zero_pkmaps(void)
  64 {
  65         int i;
  66
  67         flush_cache_kmaps();
  68
  69         for (i = 0; i < LAST_PKMAP; i++) {
  70                 struct page *page;
  71
  72                 /*
  73                  * zero means we don't have anything to do,
  74                  * >1 means that it is still in use. Only
  75                  * a count of 1 means that it is free but
  76                  * needs to be unmapped
  77                  */
  78                 if (pkmap_count[i] != 1)
  79                         continue;
  80                 pkmap_count[i] = 0;
  81
  82                 /* sanity check */
  83                 if (pte_none(pkmap_page_table[i]))
  84                         BUG();
  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(&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(&(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
 143
 144         pkmap_count[last_pkmap_nr] = 1;
 145         set_page_address(page, (void *)vaddr);
 146
 147         return vaddr;
 148 }
 149
 150 void fastcall *kmap_high(struct page *page)
 151 {
 152         unsigned long vaddr;
 153
 154         /*
 155          * For highmem pages, we can't trust "virtual" until
 156          * after we have the lock.
 157          *
 158          * We cannot call this from interrupts, as it may block
 159          */
 160         spin_lock(&kmap_lock);
 161         vaddr = (unsigned long)page_address(page);
 162         if (!vaddr)
 163                 vaddr = map_new_virtual(page);
 164         pkmap_count[PKMAP_NR(vaddr)]++;
 165         if (pkmap_count[PKMAP_NR(vaddr)] < 2)
 166                 BUG();
 167         spin_unlock(&kmap_lock);
 168         return (void*) vaddr;
 169 }
 170
 171 EXPORT_SYMBOL(kmap_high);
 172
 173 void fastcall kunmap_high(struct page *page)
 174 {
 175         unsigned long vaddr;
 176         unsigned long nr;
 177         int need_wakeup;
 178
 179         spin_lock(&kmap_lock);
 180         vaddr = (unsigned long)page_address(page);
 181         if (!vaddr)
 182                 BUG();
 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
 215 #define POOL_SIZE       64
 216
 217 static __init int init_emergency_pool(void)
 218 {
 219         struct sysinfo i;
 220         si_meminfo(&i);
 221         si_swapinfo(&i);
 222
 223         if (!i.totalhigh)
 224                 return 0;
 225
 226         page_pool = mempool_create(POOL_SIZE, page_pool_alloc, page_pool_free, NULL);
 227         if (!page_pool)
 228                 BUG();
 229         printk("highmem bounce pool size: %d pages\n", POOL_SIZE);
 230
 231         return 0;
 232 }
 233
 234 __initcall(init_emergency_pool);
 235
 236 /*
 237  * highmem version, map in to vec
 238  */
 239 static void bounce_copy_vec(struct bio_vec *to, unsigned char *vfrom)
 240 {
 241         unsigned long flags;
 242         unsigned char *vto;
 243
 244         local_irq_save(flags);
 245         vto = kmap_atomic(to->bv_page, KM_BOUNCE_READ);
 246         memcpy(vto + to->bv_offset, vfrom, to->bv_len);
 247         kunmap_atomic(vto, KM_BOUNCE_READ);
 248         local_irq_restore(flags);
 249 }
 250
 251 #else /* CONFIG_HIGHMEM */
 252
 253 #define bounce_copy_vec(to, vfrom)      \
 254         memcpy(page_address((to)->bv_page) + (to)->bv_offset, vfrom, (to)->bv_len)
 255
 256 #endif
 257
 258 #define ISA_POOL_SIZE   16
 259
 260 /*
 261  * gets called "every" time someone init's a queue with BLK_BOUNCE_ISA
 262  * as the max address, so check if the pool has already been created.
 263  */
 264 int init_emergency_isa_pool(void)
 265 {
 266         if (isa_page_pool)
 267                 return 0;
 268
 269         isa_page_pool = mempool_create(ISA_POOL_SIZE, page_pool_alloc, page_pool_free, (void *) __GFP_DMA);
 270         if (!isa_page_pool)
 271                 BUG();
 272
 273         printk("isa bounce pool size: %d pages\n", ISA_POOL_SIZE);
 274         return 0;
 275 }
 276
 277 /*
 278  * Simple bounce buffer support for highmem pages. Depending on the
 279  * queue gfp mask set, *to may or may not be a highmem page. kmap it
 280  * always, it will do the Right Thing
 281  */
 282 static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
 283 {
 284         unsigned char *vfrom;
 285         struct bio_vec *tovec, *fromvec;
 286         int i;
 287
 288         bio_for_each_segment(tovec, to, i) {
 289                 fromvec = from->bi_io_vec + i;
 290
 291                 /*
 292                  * not bounced
 293                  */
 294                 if (tovec->bv_page == fromvec->bv_page)
 295                         continue;
 296
 297                 /*
 298                  * fromvec->bv_offset and fromvec->bv_len might have been
 299                  * modified by the block layer, so use the original copy,
 300                  * bounce_copy_vec already uses tovec->bv_len
 301                  */
 302                 vfrom = page_address(fromvec->bv_page) + tovec->bv_offset;
 303
 304                 bounce_copy_vec(tovec, vfrom);
 305         }
 306 }
 307
 308 static void bounce_end_io(struct bio *bio, mempool_t *pool)
 309 {
 310         struct bio *bio_orig = bio->bi_private;
 311         struct bio_vec *bvec, *org_vec;
 312         int i;
 313
 314         if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
 315                 goto out_eio;
 316
 317         set_bit(BIO_UPTODATE, &bio_orig->bi_flags);
 318
 319         /*
 320          * free up bounce indirect pages used
 321          */
 322         bio_for_each_segment(bvec, bio, i) {
 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 out_eio:
 331         bio_endio(bio_orig, bio_orig->bi_size, 0);
 332         bio_put(bio);
 333 }
 334
 335 static int bounce_end_io_write(struct bio *bio, unsigned int bytes_done,int err)
 336 {
 337         if (bio->bi_size)
 338                 return 1;
 339
 340         bounce_end_io(bio, page_pool);
 341         return 0;
 342 }
 343
 344 static int bounce_end_io_write_isa(struct bio *bio, unsigned int bytes_done, int err)
 345 {
 346         if (bio->bi_size)
 347                 return 1;
 348
 349         bounce_end_io(bio, isa_page_pool);
 350         return 0;
 351 }
 352
 353 static void __bounce_end_io_read(struct bio *bio, mempool_t *pool)
 354 {
 355         struct bio *bio_orig = bio->bi_private;
 356
 357         if (test_bit(BIO_UPTODATE, &bio->bi_flags))
 358                 copy_to_high_bio_irq(bio_orig, bio);
 359
 360         bounce_end_io(bio, pool);
 361 }
 362
 363 static int bounce_end_io_read(struct bio *bio, unsigned int bytes_done, int err)
 364 {
 365         if (bio->bi_size)
 366                 return 1;
 367
 368         __bounce_end_io_read(bio, page_pool);
 369         return 0;
 370 }
 371
 372 static int bounce_end_io_read_isa(struct bio *bio, unsigned int bytes_done, int err)
 373 {
 374         if (bio->bi_size)
 375                 return 1;
 376
 377         __bounce_end_io_read(bio, isa_page_pool);
 378         return 0;
 379 }
 380
 381 static void __blk_queue_bounce(request_queue_t *q, struct bio **bio_orig,
 382                         mempool_t *pool)
 383 {
 384         struct page *page;
 385         struct bio *bio = NULL;
 386         int i, rw = bio_data_dir(*bio_orig);
 387         struct bio_vec *to, *from;
 388
 389         bio_for_each_segment(from, *bio_orig, i) {
 390                 page = from->bv_page;
 391
 392                 /*
 393                  * is destination page below bounce pfn?
 394                  */
 395                 if (page_to_pfn(page) < q->bounce_pfn)
 396                         continue;
 397
 398                 /*
 399                  * irk, bounce it
 400                  */
 401                 if (!bio)
 402                         bio = bio_alloc(GFP_NOIO, (*bio_orig)->bi_vcnt);
 403
 404                 to = bio->bi_io_vec + i;
 405
 406                 to->bv_page = mempool_alloc(pool, q->bounce_gfp);
 407                 to->bv_len = from->bv_len;
 408                 to->bv_offset = from->bv_offset;
 409
 410                 if (rw == WRITE) {
 411                         char *vto, *vfrom;
 412
 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) {
 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) */