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(int gfp_mask, void *data)
  34 {
  35         int gfp = gfp_mask | (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 spinlock_t kmap_lock __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
  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(&pkmap_page_table[i]);
  94
  95                 set_page_address(page, NULL);
  96         }
  97         flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
  98 }
  99
 100 static inline unsigned long map_new_virtual(struct page *page)
 101 {
 102         unsigned long vaddr;
 103         int count;
 104
 105 start:
 106         count = LAST_PKMAP;
 107         /* Find an empty entry */
 108         for (;;) {
 109                 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
 110                 if (!last_pkmap_nr) {
 111                         flush_all_zero_pkmaps();
 112                         count = LAST_PKMAP;
 113                 }
 114                 if (!pkmap_count[last_pkmap_nr])
 115                         break;  /* Found a usable entry */
 116                 if (--count)
 117                         continue;
 118
 119                 /*
 120                  * Sleep for somebody else to unmap their entries
 121                  */
 122                 {
 123                         DECLARE_WAITQUEUE(wait, current);
 124
 125                         __set_current_state(TASK_UNINTERRUPTIBLE);
 126                         add_wait_queue(&pkmap_map_wait, &wait);
 127                         spin_unlock(&kmap_lock);
 128                         schedule();
 129                         remove_wait_queue(&pkmap_map_wait, &wait);
 130                         spin_lock(&kmap_lock);
 131
 132                         /* Somebody else might have mapped it while we slept */
 133                         if (page_address(page))
 134                                 return (unsigned long)page_address(page);
 135
 136                         /* Re-start */
 137                         goto start;
 138                 }
 139         }
 140         vaddr = PKMAP_ADDR(last_pkmap_nr);
 141         set_pte(&(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
 142
 143         pkmap_count[last_pkmap_nr] = 1;
 144         set_page_address(page, (void *)vaddr);
 145
 146         return vaddr;
 147 }
 148
 149 void fastcall *kmap_high(struct page *page)
 150 {
 151         unsigned long vaddr;
 152
 153         /*
 154          * For highmem pages, we can't trust "virtual" until
 155          * after we have the lock.
 156          *
 157          * We cannot call this from interrupts, as it may block
 158          */
 159         spin_lock(&kmap_lock);
 160         vaddr = (unsigned long)page_address(page);
 161         if (!vaddr)
 162                 vaddr = map_new_virtual(page);
 163         pkmap_count[PKMAP_NR(vaddr)]++;
 164         if (pkmap_count[PKMAP_NR(vaddr)] < 2)
 165                 BUG();
 166         spin_unlock(&kmap_lock);
 167         return (void*) vaddr;
 168 }
 169
 170 EXPORT_SYMBOL(kmap_high);
 171
 172 void fastcall kunmap_high(struct page *page)
 173 {
 174         unsigned long vaddr;
 175         unsigned long nr;
 176         int need_wakeup;
 177
 178         spin_lock(&kmap_lock);
 179         vaddr = (unsigned long)page_address(page);
 180         if (!vaddr)
 181                 BUG();
 182         nr = PKMAP_NR(vaddr);
 183
 184         /*
 185          * A count must never go down to zero
 186          * without a TLB flush!
 187          */
 188         need_wakeup = 0;
 189         switch (--pkmap_count[nr]) {
 190         case 0:
 191                 BUG();
 192         case 1:
 193                 /*
 194                  * Avoid an unnecessary wake_up() function call.
 195                  * The common case is pkmap_count[] == 1, but
 196                  * no waiters.
 197                  * The tasks queued in the wait-queue are guarded
 198                  * by both the lock in the wait-queue-head and by
 199                  * the kmap_lock.  As the kmap_lock is held here,
 200                  * no need for the wait-queue-head's lock.  Simply
 201                  * test if the queue is empty.
 202                  */
 203                 need_wakeup = waitqueue_active(&pkmap_map_wait);
 204         }
 205         spin_unlock(&kmap_lock);
 206
 207         /* do wake-up, if needed, race-free outside of the spin lock */
 208         if (need_wakeup)
 209                 wake_up(&pkmap_map_wait);
 210 }
 211
 212 EXPORT_SYMBOL(kunmap_high);
 213
 214 #define POOL_SIZE       64
 215
 216 static __init int init_emergency_pool(void)
 217 {
 218         struct sysinfo i;
 219         si_meminfo(&i);
 220         si_swapinfo(&i);
 221
 222         if (!i.totalhigh)
 223                 return 0;
 224
 225         page_pool = mempool_create(POOL_SIZE, page_pool_alloc, page_pool_free, NULL);
 226         if (!page_pool)
 227                 BUG();
 228         printk("highmem bounce pool size: %d pages\n", POOL_SIZE);
 229
 230         return 0;
 231 }
 232
 233 __initcall(init_emergency_pool);
 234
 235 /*
 236  * highmem version, map in to vec
 237  */
 238 static void bounce_copy_vec(struct bio_vec *to, unsigned char *vfrom)
 239 {
 240         unsigned long flags;
 241         unsigned char *vto;
 242
 243         local_irq_save(flags);
 244         vto = kmap_atomic(to->bv_page, KM_BOUNCE_READ);
 245         memcpy(vto + to->bv_offset, vfrom, to->bv_len);
 246         kunmap_atomic(vto, KM_BOUNCE_READ);
 247         local_irq_restore(flags);
 248 }
 249
 250 #else /* CONFIG_HIGHMEM */
 251
 252 #define bounce_copy_vec(to, vfrom)      \
 253         memcpy(page_address((to)->bv_page) + (to)->bv_offset, vfrom, (to)->bv_len)
 254
 255 #endif
 256
 257 #define ISA_POOL_SIZE   16
 258
 259 /*
 260  * gets called "every" time someone init's a queue with BLK_BOUNCE_ISA
 261  * as the max address, so check if the pool has already been created.
 262  */
 263 int init_emergency_isa_pool(void)
 264 {
 265         if (isa_page_pool)
 266                 return 0;
 267
 268         isa_page_pool = mempool_create(ISA_POOL_SIZE, page_pool_alloc, page_pool_free, (void *) __GFP_DMA);
 269         if (!isa_page_pool)
 270                 BUG();
 271
 272         printk("isa bounce pool size: %d pages\n", ISA_POOL_SIZE);
 273         return 0;
 274 }
 275
 276 /*
 277  * Simple bounce buffer support for highmem pages. Depending on the
 278  * queue gfp mask set, *to may or may not be a highmem page. kmap it
 279  * always, it will do the Right Thing
 280  */
 281 static void copy_to_high_bio_irq(struct bio *to, struct bio *from)
 282 {
 283         unsigned char *vfrom;
 284         struct bio_vec *tovec, *fromvec;
 285         int i;
 286
 287         bio_for_each_segment(tovec, to, i) {
 288                 fromvec = from->bi_io_vec + i;
 289
 290                 /*
 291                  * not bounced
 292                  */
 293                 if (tovec->bv_page == fromvec->bv_page)
 294                         continue;
 295
 296                 /*
 297                  * fromvec->bv_offset and fromvec->bv_len might have been
 298                  * modified by the block layer, so use the original copy,
 299                  * bounce_copy_vec already uses tovec->bv_len
 300                  */
 301                 vfrom = page_address(fromvec->bv_page) + tovec->bv_offset;
 302
 303                 bounce_copy_vec(tovec, vfrom);
 304         }
 305 }
 306
 307 static void bounce_end_io(struct bio *bio, mempool_t *pool)
 308 {
 309         struct bio *bio_orig = bio->bi_private;
 310         struct bio_vec *bvec, *org_vec;
 311         int i;
 312
 313         if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
 314                 goto out_eio;
 315
 316         set_bit(BIO_UPTODATE, &bio_orig->bi_flags);
 317
 318         /*
 319          * free up bounce indirect pages used
 320          */
 321         bio_for_each_segment(bvec, bio, i) {
 322                 org_vec = bio_orig->bi_io_vec + i;
 323                 if (bvec->bv_page == org_vec->bv_page)
 324                         continue;
 325
 326                 mempool_free(bvec->bv_page, pool);
 327         }
 328
 329 out_eio:
 330         bio_endio(bio_orig, bio_orig->bi_size, 0);
 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);
 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);
 349         return 0;
 350 }
 351
 352 static void __bounce_end_io_read(struct bio *bio, mempool_t *pool)
 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);
 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);
 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);
 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                         vto = page_address(to->bv_page) + to->bv_offset;
 413                         vfrom = kmap(from->bv_page) + from->bv_offset;
 414                         memcpy(vto, vfrom, to->bv_len);
 415                         kunmap(from->bv_page);
 416                 }
 417         }
 418
 419         /*
 420          * no pages bounced
 421          */
 422         if (!bio)
 423                 return;
 424
 425         /*
 426          * at least one page was bounced, fill in possible non-highmem
 427          * pages
 428          */
 429         bio_for_each_segment(from, *bio_orig, i) {
 430                 to = bio_iovec_idx(bio, i);
 431                 if (!to->bv_page) {
 432                         to->bv_page = from->bv_page;
 433                         to->bv_len = from->bv_len;
 434                         to->bv_offset = from->bv_offset;
 435                 }
 436         }
 437
 438         bio->bi_bdev = (*bio_orig)->bi_bdev;
 439         bio->bi_flags |= (1 << BIO_BOUNCED);
 440         bio->bi_sector = (*bio_orig)->bi_sector;
 441         bio->bi_rw = (*bio_orig)->bi_rw;
 442
 443         bio->bi_vcnt = (*bio_orig)->bi_vcnt;
 444         bio->bi_idx = (*bio_orig)->bi_idx;
 445         bio->bi_size = (*bio_orig)->bi_size;
 446
 447         if (pool == page_pool) {
 448                 bio->bi_end_io = bounce_end_io_write;
 449                 if (rw == READ)
 450                         bio->bi_end_io = bounce_end_io_read;
 451         } else {
 452                 bio->bi_end_io = bounce_end_io_write_isa;
 453                 if (rw == READ)
 454                         bio->bi_end_io = bounce_end_io_read_isa;
 455         }
 456
 457         bio->bi_private = *bio_orig;
 458         *bio_orig = bio;
 459 }
 460
 461 void blk_queue_bounce(request_queue_t *q, struct bio **bio_orig)
 462 {
 463         mempool_t *pool;
 464
 465         /*
 466          * for non-isa bounce case, just check if the bounce pfn is equal
 467          * to or bigger than the highest pfn in the system -- in that case,
 468          * don't waste time iterating over bio segments
 469          */
 470         if (!(q->bounce_gfp & GFP_DMA)) {
 471                 if (q->bounce_pfn >= blk_max_pfn)
 472                         return;
 473                 pool = page_pool;
 474         } else {
 475                 BUG_ON(!isa_page_pool);
 476                 pool = isa_page_pool;
 477         }
 478
 479         /*
 480          * slow path
 481          */
 482         __blk_queue_bounce(q, bio_orig, pool);
 483 }
 484
 485 EXPORT_SYMBOL(blk_queue_bounce);
 486
 487 #if defined(HASHED_PAGE_VIRTUAL)
 488
 489 #define PA_HASH_ORDER   7
 490
 491 /*
 492  * Describes one page->virtual association
 493  */
 494 struct page_address_map {
 495         struct page *page;
 496         void *virtual;
 497         struct list_head list;
 498 };
 499
 500 /*
 501  * page_address_map freelist, allocated from page_address_maps.
 502  */
 503 static struct list_head page_address_pool;      /* freelist */
 504 static spinlock_t pool_lock;                    /* protects page_address_pool */
 505
 506 /*
 507  * Hash table bucket
 508  */
 509 static struct page_address_slot {
 510         struct list_head lh;                    /* List of page_address_maps */
 511         spinlock_t lock;                        /* Protect this bucket's list */
 512 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
 513
 514 static struct page_address_slot *page_slot(struct page *page)
 515 {
 516         return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
 517 }
 518
 519 void *page_address(struct page *page)
 520 {
 521         unsigned long flags;
 522         void *ret;
 523         struct page_address_slot *pas;
 524
 525         if (!PageHighMem(page))
 526                 return lowmem_page_address(page);
 527
 528         pas = page_slot(page);
 529         ret = NULL;
 530         spin_lock_irqsave(&pas->lock, flags);
 531         if (!list_empty(&pas->lh)) {
 532                 struct page_address_map *pam;
 533
 534                 list_for_each_entry(pam, &pas->lh, list) {
 535                         if (pam->page == page) {
 536                                 ret = pam->virtual;
 537                                 goto done;
 538                         }
 539                 }
 540         }
 541 done:
 542         spin_unlock_irqrestore(&pas->lock, flags);
 543         return ret;
 544 }
 545
 546 EXPORT_SYMBOL(page_address);
 547
 548 void set_page_address(struct page *page, void *virtual)
 549 {
 550         unsigned long flags;
 551         struct page_address_slot *pas;
 552         struct page_address_map *pam;
 553
 554         BUG_ON(!PageHighMem(page));
 555
 556         pas = page_slot(page);
 557         if (virtual) {          /* Add */
 558                 BUG_ON(list_empty(&page_address_pool));
 559
 560                 spin_lock_irqsave(&pool_lock, flags);
 561                 pam = list_entry(page_address_pool.next,
 562                                 struct page_address_map, list);
 563                 list_del(&pam->list);
 564                 spin_unlock_irqrestore(&pool_lock, flags);
 565
 566                 pam->page = page;
 567                 pam->virtual = virtual;
 568
 569                 spin_lock_irqsave(&pas->lock, flags);
 570                 list_add_tail(&pam->list, &pas->lh);
 571                 spin_unlock_irqrestore(&pas->lock, flags);
 572         } else {                /* Remove */
 573                 spin_lock_irqsave(&pas->lock, flags);
 574                 list_for_each_entry(pam, &pas->lh, list) {
 575                         if (pam->page == page) {
 576                                 list_del(&pam->list);
 577                                 spin_unlock_irqrestore(&pas->lock, flags);
 578                                 spin_lock_irqsave(&pool_lock, flags);
 579                                 list_add_tail(&pam->list, &page_address_pool);
 580                                 spin_unlock_irqrestore(&pool_lock, flags);
 581                                 goto done;
 582                         }
 583                 }
 584                 spin_unlock_irqrestore(&pas->lock, flags);
 585         }
 586 done:
 587         return;
 588 }
 589
 590 static struct page_address_map page_address_maps[LAST_PKMAP];
 591
 592 void __init page_address_init(void)
 593 {
 594         int i;
 595
 596         INIT_LIST_HEAD(&page_address_pool);
 597         for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)
 598                 list_add(&page_address_maps[i].list, &page_address_pool);
 599         for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
 600                 INIT_LIST_HEAD(&page_address_htable[i].lh);
 601                 spin_lock_init(&page_address_htable[i].lock);
 602         }
 603         spin_lock_init(&pool_lock);
 604 }
 605
 606 #endif  /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */