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                 dec_page_state(nr_bounce);
 329         }
 330
 331         bio_endio(bio_orig, bio_orig->bi_size, err);
 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, err);
 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, err);
 350         return 0;
 351 }
 352
 353 static void __bounce_end_io_read(struct bio *bio, mempool_t *pool, int err)
 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, err);
 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, err);
 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, err);
 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                 inc_page_state(nr_bounce);
 410
 411                 if (rw == WRITE) {
 412                         char *vto, *vfrom;
 413
 414                         flush_dcache_page(from->bv_page);
 415                         vto = page_address(to->bv_page) + to->bv_offset;
 416                         vfrom = kmap(from->bv_page) + from->bv_offset;
 417                         memcpy(vto, vfrom, to->bv_len);
 418                         kunmap(from->bv_page);
 419                 }
 420         }
 421
 422         /*
 423          * no pages bounced
 424          */
 425         if (!bio)
 426                 return;
 427
 428         /*
 429          * at least one page was bounced, fill in possible non-highmem
 430          * pages
 431          */
 432         __bio_for_each_segment(from, *bio_orig, i, 0) {
 433                 to = bio_iovec_idx(bio, i);
 434                 if (!to->bv_page) {
 435                         to->bv_page = from->bv_page;
 436                         to->bv_len = from->bv_len;
 437                         to->bv_offset = from->bv_offset;
 438                 }
 439         }
 440
 441         bio->bi_bdev = (*bio_orig)->bi_bdev;
 442         bio->bi_flags |= (1 << BIO_BOUNCED);
 443         bio->bi_sector = (*bio_orig)->bi_sector;
 444         bio->bi_rw = (*bio_orig)->bi_rw;
 445
 446         bio->bi_vcnt = (*bio_orig)->bi_vcnt;
 447         bio->bi_idx = (*bio_orig)->bi_idx;
 448         bio->bi_size = (*bio_orig)->bi_size;
 449
 450         if (pool == page_pool) {
 451                 bio->bi_end_io = bounce_end_io_write;
 452                 if (rw == READ)
 453                         bio->bi_end_io = bounce_end_io_read;
 454         } else {
 455                 bio->bi_end_io = bounce_end_io_write_isa;
 456                 if (rw == READ)
 457                         bio->bi_end_io = bounce_end_io_read_isa;
 458         }
 459
 460         bio->bi_private = *bio_orig;
 461         *bio_orig = bio;
 462 }
 463
 464 void blk_queue_bounce(request_queue_t *q, struct bio **bio_orig)
 465 {
 466         mempool_t *pool;
 467
 468         /*
 469          * for non-isa bounce case, just check if the bounce pfn is equal
 470          * to or bigger than the highest pfn in the system -- in that case,
 471          * don't waste time iterating over bio segments
 472          */
 473         if (!(q->bounce_gfp & GFP_DMA)) {
 474                 if (q->bounce_pfn >= blk_max_pfn)
 475                         return;
 476                 pool = page_pool;
 477         } else {
 478                 BUG_ON(!isa_page_pool);
 479                 pool = isa_page_pool;
 480         }
 481
 482         /*
 483          * slow path
 484          */
 485         __blk_queue_bounce(q, bio_orig, pool);
 486 }
 487
 488 EXPORT_SYMBOL(blk_queue_bounce);
 489
 490 #if defined(HASHED_PAGE_VIRTUAL)
 491
 492 #define PA_HASH_ORDER   7
 493
 494 /*
 495  * Describes one page->virtual association
 496  */
 497 struct page_address_map {
 498         struct page *page;
 499         void *virtual;
 500         struct list_head list;
 501 };
 502
 503 /*
 504  * page_address_map freelist, allocated from page_address_maps.
 505  */
 506 static struct list_head page_address_pool;      /* freelist */
 507 static spinlock_t pool_lock;                    /* protects page_address_pool */
 508
 509 /*
 510  * Hash table bucket
 511  */
 512 static struct page_address_slot {
 513         struct list_head lh;                    /* List of page_address_maps */
 514         spinlock_t lock;                        /* Protect this bucket's list */
 515 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
 516
 517 static struct page_address_slot *page_slot(struct page *page)
 518 {
 519         return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
 520 }
 521
 522 void *page_address(struct page *page)
 523 {
 524         unsigned long flags;
 525         void *ret;
 526         struct page_address_slot *pas;
 527
 528         if (!PageHighMem(page))
 529                 return lowmem_page_address(page);
 530
 531         pas = page_slot(page);
 532         ret = NULL;
 533         spin_lock_irqsave(&pas->lock, flags);
 534         if (!list_empty(&pas->lh)) {
 535                 struct page_address_map *pam;
 536
 537                 list_for_each_entry(pam, &pas->lh, list) {
 538                         if (pam->page == page) {
 539                                 ret = pam->virtual;
 540                                 goto done;
 541                         }
 542                 }
 543         }
 544 done:
 545         spin_unlock_irqrestore(&pas->lock, flags);
 546         return ret;
 547 }
 548
 549 EXPORT_SYMBOL(page_address);
 550
 551 void set_page_address(struct page *page, void *virtual)
 552 {
 553         unsigned long flags;
 554         struct page_address_slot *pas;
 555         struct page_address_map *pam;
 556
 557         BUG_ON(!PageHighMem(page));
 558
 559         pas = page_slot(page);
 560         if (virtual) {          /* Add */
 561                 BUG_ON(list_empty(&page_address_pool));
 562
 563                 spin_lock_irqsave(&pool_lock, flags);
 564                 pam = list_entry(page_address_pool.next,
 565                                 struct page_address_map, list);
 566                 list_del(&pam->list);
 567                 spin_unlock_irqrestore(&pool_lock, flags);
 568
 569                 pam->page = page;
 570                 pam->virtual = virtual;
 571
 572                 spin_lock_irqsave(&pas->lock, flags);
 573                 list_add_tail(&pam->list, &pas->lh);
 574                 spin_unlock_irqrestore(&pas->lock, flags);
 575         } else {                /* Remove */
 576                 spin_lock_irqsave(&pas->lock, flags);
 577                 list_for_each_entry(pam, &pas->lh, list) {
 578                         if (pam->page == page) {
 579                                 list_del(&pam->list);
 580                                 spin_unlock_irqrestore(&pas->lock, flags);
 581                                 spin_lock_irqsave(&pool_lock, flags);
 582                                 list_add_tail(&pam->list, &page_address_pool);
 583                                 spin_unlock_irqrestore(&pool_lock, flags);
 584                                 goto done;
 585                         }
 586                 }
 587                 spin_unlock_irqrestore(&pas->lock, flags);
 588         }
 589 done:
 590         return;
 591 }
 592
 593 static struct page_address_map page_address_maps[LAST_PKMAP];
 594
 595 void __init page_address_init(void)
 596 {
 597         int i;
 598
 599         INIT_LIST_HEAD(&page_address_pool);
 600         for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)
 601                 list_add(&page_address_maps[i].list, &page_address_pool);
 602         for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
 603                 INIT_LIST_HEAD(&page_address_htable[i].lh);
 604                 spin_lock_init(&page_address_htable[i].lock);
 605         }
 606         spin_lock_init(&pool_lock);
 607 }
 608
 609 #endif  /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */