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_isa(gfp_t gfp_mask, void *data)
  34 {
  35         return alloc_page(gfp_mask | GFP_DMA);
  36 }
  37
  38 static void page_pool_free(void *page, void *data)
  39 {
  40         __free_page(page);
  41 }
  42
  43 /*
  44  * Virtual_count is not a pure "count".
  45  *  0 means that it is not mapped, and has not been mapped
  46  *    since a TLB flush - it is usable.
  47  *  1 means that there are no users, but it has been mapped
  48  *    since the last TLB flush - so we can't use it.
  49  *  n means that there are (n-1) current users of it.
  50  */
  51 #ifdef CONFIG_HIGHMEM
  52
  53 static void *page_pool_alloc(gfp_t gfp_mask, void *data)
  54 {
  55         return alloc_page(gfp_mask);
  56 }
  57
  58 static int pkmap_count[LAST_PKMAP];
  59 static unsigned int last_pkmap_nr;
  60 static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
  61
  62 pte_t * pkmap_page_table;
  63
  64 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
  65
  66 static void flush_all_zero_pkmaps(void)
  67 {
  68         int i;
  69
  70         flush_cache_kmaps();
  71
  72         for (i = 0; i < LAST_PKMAP; i++) {
  73                 struct page *page;
  74
  75                 /*
  76                  * zero means we don't have anything to do,
  77                  * >1 means that it is still in use. Only
  78                  * a count of 1 means that it is free but
  79                  * needs to be unmapped
  80                  */
  81                 if (pkmap_count[i] != 1)
  82                         continue;
  83                 pkmap_count[i] = 0;
  84
  85                 /* sanity check */
  86                 if (pte_none(pkmap_page_table[i]))
  87                         BUG();
  88
  89                 /*
  90                  * Don't need an atomic fetch-and-clear op here;
  91                  * no-one has the page mapped, and cannot get at
  92                  * its virtual address (and hence PTE) without first
  93                  * getting the kmap_lock (which is held here).
  94                  * So no dangers, even with speculative execution.
  95                  */
  96                 page = pte_page(pkmap_page_table[i]);
  97                 pte_clear(&init_mm, (unsigned long)page_address(page),
  98                           &pkmap_page_table[i]);
  99
 100                 set_page_address(page, NULL);
 101         }
 102         flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
 103 }
 104
 105 static inline unsigned long map_new_virtual(struct page *page)
 106 {
 107         unsigned long vaddr;
 108         int count;
 109
 110 start:
 111         count = LAST_PKMAP;
 112         /* Find an empty entry */
 113         for (;;) {
 114                 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
 115                 if (!last_pkmap_nr) {
 116                         flush_all_zero_pkmaps();
 117                         count = LAST_PKMAP;
 118                 }
 119                 if (!pkmap_count[last_pkmap_nr])
 120                         break;  /* Found a usable entry */
 121                 if (--count)
 122                         continue;
 123
 124                 /*
 125                  * Sleep for somebody else to unmap their entries
 126                  */
 127                 {
 128                         DECLARE_WAITQUEUE(wait, current);
 129
 130                         __set_current_state(TASK_UNINTERRUPTIBLE);
 131                         add_wait_queue(&pkmap_map_wait, &wait);
 132                         spin_unlock(&kmap_lock);
 133                         schedule();
 134                         remove_wait_queue(&pkmap_map_wait, &wait);
 135                         spin_lock(&kmap_lock);
 136
 137                         /* Somebody else might have mapped it while we slept */
 138                         if (page_address(page))
 139                                 return (unsigned long)page_address(page);
 140
 141                         /* Re-start */
 142                         goto start;
 143                 }
 144         }
 145         vaddr = PKMAP_ADDR(last_pkmap_nr);
 146         set_pte_at(&init_mm, vaddr,
 147                    &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
 148
 149         pkmap_count[last_pkmap_nr] = 1;
 150         set_page_address(page, (void *)vaddr);
 151
 152         return vaddr;
 153 }
 154
 155 void fastcall *kmap_high(struct page *page)
 156 {
 157         unsigned long vaddr;
 158
 159         /*
 160          * For highmem pages, we can't trust "virtual" until
 161          * after we have the lock.
 162          *
 163          * We cannot call this from interrupts, as it may block
 164          */
 165         spin_lock(&kmap_lock);
 166         vaddr = (unsigned long)page_address(page);
 167         if (!vaddr)
 168                 vaddr = map_new_virtual(page);
 169         pkmap_count[PKMAP_NR(vaddr)]++;
 170         if (pkmap_count[PKMAP_NR(vaddr)] < 2)
 171                 BUG();
 172         spin_unlock(&kmap_lock);
 173         return (void*) vaddr;
 174 }
 175
 176 EXPORT_SYMBOL(kmap_high);
 177
 178 void fastcall kunmap_high(struct page *page)
 179 {
 180         unsigned long vaddr;
 181         unsigned long nr;
 182         int need_wakeup;
 183
 184         spin_lock(&kmap_lock);
 185         vaddr = (unsigned long)page_address(page);
 186         if (!vaddr)
 187                 BUG();
 188         nr = PKMAP_NR(vaddr);
 189
 190         /*
 191          * A count must never go down to zero
 192          * without a TLB flush!
 193          */
 194         need_wakeup = 0;
 195         switch (--pkmap_count[nr]) {
 196         case 0:
 197                 BUG();
 198         case 1:
 199                 /*
 200                  * Avoid an unnecessary wake_up() function call.
 201                  * The common case is pkmap_count[] == 1, but
 202                  * no waiters.
 203                  * The tasks queued in the wait-queue are guarded
 204                  * by both the lock in the wait-queue-head and by
 205                  * the kmap_lock.  As the kmap_lock is held here,
 206                  * no need for the wait-queue-head's lock.  Simply
 207                  * test if the queue is empty.
 208                  */
 209                 need_wakeup = waitqueue_active(&pkmap_map_wait);
 210         }
 211         spin_unlock(&kmap_lock);
 212
 213         /* do wake-up, if needed, race-free outside of the spin lock */
 214         if (need_wakeup)
 215                 wake_up(&pkmap_map_wait);
 216 }
 217
 218 EXPORT_SYMBOL(kunmap_high);
 219
 220 #define POOL_SIZE       64
 221
 222 static __init int init_emergency_pool(void)
 223 {
 224         struct sysinfo i;
 225         si_meminfo(&i);
 226         si_swapinfo(&i);
 227
 228         if (!i.totalhigh)
 229                 return 0;
 230
 231         page_pool = mempool_create(POOL_SIZE, page_pool_alloc, page_pool_free, NULL);
 232         if (!page_pool)
 233                 BUG();
 234         printk("highmem bounce pool size: %d pages\n", POOL_SIZE);
 235
 236         return 0;
 237 }
 238
 239 __initcall(init_emergency_pool);
 240
 241 /*
 242  * highmem version, map in to vec
 243  */
 244 static void bounce_copy_vec(struct bio_vec *to, unsigned char *vfrom)
 245 {
 246         unsigned long flags;
 247         unsigned char *vto;
 248
 249         local_irq_save(flags);
 250         vto = kmap_atomic(to->bv_page, KM_BOUNCE_READ);
 251         memcpy(vto + to->bv_offset, vfrom, to->bv_len);
 252         kunmap_atomic(vto, KM_BOUNCE_READ);
 253         local_irq_restore(flags);
 254 }
 255
 256 #else /* CONFIG_HIGHMEM */
 257
 258 #define bounce_copy_vec(to, vfrom)      \
 259         memcpy(page_address((to)->bv_page) + (to)->bv_offset, vfrom, (to)->bv_len)
 260
 261 #endif
 262
 263 #define ISA_POOL_SIZE   16
 264
 265 /*
 266  * gets called "every" time someone init's a queue with BLK_BOUNCE_ISA
 267  * as the max address, so check if the pool has already been created.
 268  */
 269 int init_emergency_isa_pool(void)
 270 {
 271         if (isa_page_pool)
 272                 return 0;
 273
 274         isa_page_pool = mempool_create(ISA_POOL_SIZE, page_pool_alloc_isa, page_pool_free, NULL);
 275         if (!isa_page_pool)
 276                 BUG();
 277
 278         printk("isa bounce pool size: %d pages\n", ISA_POOL_SIZE);
 279         return 0;
 280 }
 281
 282 /*
 283  * Simple bounce buffer support for highmem pages. Depending on the
 284  * queue gfp mask set, *to may or may not be a highmem page. kmap it
 285  * always, it will do the Right Thing
 286  */
 287 static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
 288 {
 289         unsigned char *vfrom;
 290         struct bio_vec *tovec, *fromvec;
 291         int i;
 292
 293         __bio_for_each_segment(tovec, to, i, 0) {
 294                 fromvec = from->bi_io_vec + i;
 295
 296                 /*
 297                  * not bounced
 298                  */
 299                 if (tovec->bv_page == fromvec->bv_page)
 300                         continue;
 301
 302                 /*
 303                  * fromvec->bv_offset and fromvec->bv_len might have been
 304                  * modified by the block layer, so use the original copy,
 305                  * bounce_copy_vec already uses tovec->bv_len
 306                  */
 307                 vfrom = page_address(fromvec->bv_page) + tovec->bv_offset;
 308
 309                 flush_dcache_page(tovec->bv_page);
 310                 bounce_copy_vec(tovec, vfrom);
 311         }
 312 }
 313
 314 static void bounce_end_io(struct bio *bio, mempool_t *pool, int err)
 315 {
 316         struct bio *bio_orig = bio->bi_private;
 317         struct bio_vec *bvec, *org_vec;
 318         int i;
 319
 320         if (test_bit(BIO_EOPNOTSUPP, &bio->bi_flags))
 321                 set_bit(BIO_EOPNOTSUPP, &bio_orig->bi_flags);
 322
 323         /*
 324          * free up bounce indirect pages used
 325          */
 326         __bio_for_each_segment(bvec, bio, i, 0) {
 327                 org_vec = bio_orig->bi_io_vec + i;
 328                 if (bvec->bv_page == org_vec->bv_page)
 329                         continue;
 330
 331                 mempool_free(bvec->bv_page, pool);
 332                 dec_page_state(nr_bounce);
 333         }
 334
 335         bio_endio(bio_orig, bio_orig->bi_size, err);
 336         bio_put(bio);
 337 }
 338
 339 static int bounce_end_io_write(struct bio *bio, unsigned int bytes_done,int err)
 340 {
 341         if (bio->bi_size)
 342                 return 1;
 343
 344         bounce_end_io(bio, page_pool, err);
 345         return 0;
 346 }
 347
 348 static int bounce_end_io_write_isa(struct bio *bio, unsigned int bytes_done, int err)
 349 {
 350         if (bio->bi_size)
 351                 return 1;
 352
 353         bounce_end_io(bio, isa_page_pool, err);
 354         return 0;
 355 }
 356
 357 static void __bounce_end_io_read(struct bio *bio, mempool_t *pool, int err)
 358 {
 359         struct bio *bio_orig = bio->bi_private;
 360
 361         if (test_bit(BIO_UPTODATE, &bio->bi_flags))
 362                 copy_to_high_bio_irq(bio_orig, bio);
 363
 364         bounce_end_io(bio, pool, err);
 365 }
 366
 367 static int bounce_end_io_read(struct bio *bio, unsigned int bytes_done, int err)
 368 {
 369         if (bio->bi_size)
 370                 return 1;
 371
 372         __bounce_end_io_read(bio, page_pool, err);
 373         return 0;
 374 }
 375
 376 static int bounce_end_io_read_isa(struct bio *bio, unsigned int bytes_done, int err)
 377 {
 378         if (bio->bi_size)
 379                 return 1;
 380
 381         __bounce_end_io_read(bio, isa_page_pool, err);
 382         return 0;
 383 }
 384
 385 static void __blk_queue_bounce(request_queue_t *q, struct bio **bio_orig,
 386                         mempool_t *pool)
 387 {
 388         struct page *page;
 389         struct bio *bio = NULL;
 390         int i, rw = bio_data_dir(*bio_orig);
 391         struct bio_vec *to, *from;
 392
 393         bio_for_each_segment(from, *bio_orig, i) {
 394                 page = from->bv_page;
 395
 396                 /*
 397                  * is destination page below bounce pfn?
 398                  */
 399                 if (page_to_pfn(page) < q->bounce_pfn)
 400                         continue;
 401
 402                 /*
 403                  * irk, bounce it
 404                  */
 405                 if (!bio)
 406                         bio = bio_alloc(GFP_NOIO, (*bio_orig)->bi_vcnt);
 407
 408                 to = bio->bi_io_vec + i;
 409
 410                 to->bv_page = mempool_alloc(pool, q->bounce_gfp);
 411                 to->bv_len = from->bv_len;
 412                 to->bv_offset = from->bv_offset;
 413                 inc_page_state(nr_bounce);
 414
 415                 if (rw == WRITE) {
 416                         char *vto, *vfrom;
 417
 418                         flush_dcache_page(from->bv_page);
 419                         vto = page_address(to->bv_page) + to->bv_offset;
 420                         vfrom = kmap(from->bv_page) + from->bv_offset;
 421                         memcpy(vto, vfrom, to->bv_len);
 422                         kunmap(from->bv_page);
 423                 }
 424         }
 425
 426         /*
 427          * no pages bounced
 428          */
 429         if (!bio)
 430                 return;
 431
 432         /*
 433          * at least one page was bounced, fill in possible non-highmem
 434          * pages
 435          */
 436         __bio_for_each_segment(from, *bio_orig, i, 0) {
 437                 to = bio_iovec_idx(bio, i);
 438                 if (!to->bv_page) {
 439                         to->bv_page = from->bv_page;
 440                         to->bv_len = from->bv_len;
 441                         to->bv_offset = from->bv_offset;
 442                 }
 443         }
 444
 445         bio->bi_bdev = (*bio_orig)->bi_bdev;
 446         bio->bi_flags |= (1 << BIO_BOUNCED);
 447         bio->bi_sector = (*bio_orig)->bi_sector;
 448         bio->bi_rw = (*bio_orig)->bi_rw;
 449
 450         bio->bi_vcnt = (*bio_orig)->bi_vcnt;
 451         bio->bi_idx = (*bio_orig)->bi_idx;
 452         bio->bi_size = (*bio_orig)->bi_size;
 453
 454         if (pool == page_pool) {
 455                 bio->bi_end_io = bounce_end_io_write;
 456                 if (rw == READ)
 457                         bio->bi_end_io = bounce_end_io_read;
 458         } else {
 459                 bio->bi_end_io = bounce_end_io_write_isa;
 460                 if (rw == READ)
 461                         bio->bi_end_io = bounce_end_io_read_isa;
 462         }
 463
 464         bio->bi_private = *bio_orig;
 465         *bio_orig = bio;
 466 }
 467
 468 void blk_queue_bounce(request_queue_t *q, struct bio **bio_orig)
 469 {
 470         mempool_t *pool;
 471
 472         /*
 473          * for non-isa bounce case, just check if the bounce pfn is equal
 474          * to or bigger than the highest pfn in the system -- in that case,
 475          * don't waste time iterating over bio segments
 476          */
 477         if (!(q->bounce_gfp & GFP_DMA)) {
 478                 if (q->bounce_pfn >= blk_max_pfn)
 479                         return;
 480                 pool = page_pool;
 481         } else {
 482                 BUG_ON(!isa_page_pool);
 483                 pool = isa_page_pool;
 484         }
 485
 486         /*
 487          * slow path
 488          */
 489         __blk_queue_bounce(q, bio_orig, pool);
 490 }
 491
 492 EXPORT_SYMBOL(blk_queue_bounce);
 493
 494 #if defined(HASHED_PAGE_VIRTUAL)
 495
 496 #define PA_HASH_ORDER   7
 497
 498 /*
 499  * Describes one page->virtual association
 500  */
 501 struct page_address_map {
 502         struct page *page;
 503         void *virtual;
 504         struct list_head list;
 505 };
 506
 507 /*
 508  * page_address_map freelist, allocated from page_address_maps.
 509  */
 510 static struct list_head page_address_pool;      /* freelist */
 511 static spinlock_t pool_lock;                    /* protects page_address_pool */
 512
 513 /*
 514  * Hash table bucket
 515  */
 516 static struct page_address_slot {
 517         struct list_head lh;                    /* List of page_address_maps */
 518         spinlock_t lock;                        /* Protect this bucket's list */
 519 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
 520
 521 static struct page_address_slot *page_slot(struct page *page)
 522 {
 523         return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
 524 }
 525
 526 void *page_address(struct page *page)
 527 {
 528         unsigned long flags;
 529         void *ret;
 530         struct page_address_slot *pas;
 531
 532         if (!PageHighMem(page))
 533                 return lowmem_page_address(page);
 534
 535         pas = page_slot(page);
 536         ret = NULL;
 537         spin_lock_irqsave(&pas->lock, flags);
 538         if (!list_empty(&pas->lh)) {
 539                 struct page_address_map *pam;
 540
 541                 list_for_each_entry(pam, &pas->lh, list) {
 542                         if (pam->page == page) {
 543                                 ret = pam->virtual;
 544                                 goto done;
 545                         }
 546                 }
 547         }
 548 done:
 549         spin_unlock_irqrestore(&pas->lock, flags);
 550         return ret;
 551 }
 552
 553 EXPORT_SYMBOL(page_address);
 554
 555 void set_page_address(struct page *page, void *virtual)
 556 {
 557         unsigned long flags;
 558         struct page_address_slot *pas;
 559         struct page_address_map *pam;
 560
 561         BUG_ON(!PageHighMem(page));
 562
 563         pas = page_slot(page);
 564         if (virtual) {          /* Add */
 565                 BUG_ON(list_empty(&page_address_pool));
 566
 567                 spin_lock_irqsave(&pool_lock, flags);
 568                 pam = list_entry(page_address_pool.next,
 569                                 struct page_address_map, list);
 570                 list_del(&pam->list);
 571                 spin_unlock_irqrestore(&pool_lock, flags);
 572
 573                 pam->page = page;
 574                 pam->virtual = virtual;
 575
 576                 spin_lock_irqsave(&pas->lock, flags);
 577                 list_add_tail(&pam->list, &pas->lh);
 578                 spin_unlock_irqrestore(&pas->lock, flags);
 579         } else {                /* Remove */
 580                 spin_lock_irqsave(&pas->lock, flags);
 581                 list_for_each_entry(pam, &pas->lh, list) {
 582                         if (pam->page == page) {
 583                                 list_del(&pam->list);
 584                                 spin_unlock_irqrestore(&pas->lock, flags);
 585                                 spin_lock_irqsave(&pool_lock, flags);
 586                                 list_add_tail(&pam->list, &page_address_pool);
 587                                 spin_unlock_irqrestore(&pool_lock, flags);
 588                                 goto done;
 589                         }
 590                 }
 591                 spin_unlock_irqrestore(&pas->lock, flags);
 592         }
 593 done:
 594         return;
 595 }
 596
 597 static struct page_address_map page_address_maps[LAST_PKMAP];
 598
 599 void __init page_address_init(void)
 600 {
 601         int i;
 602
 603         INIT_LIST_HEAD(&page_address_pool);
 604         for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)
 605                 list_add(&page_address_maps[i].list, &page_address_pool);
 606         for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
 607                 INIT_LIST_HEAD(&page_address_htable[i].lh);
 608                 spin_lock_init(&page_address_htable[i].lock);
 609         }
 610         spin_lock_init(&pool_lock);
 611 }
 612
 613 #endif  /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */