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 <linux/blktrace_api.h>
  30 #include <asm/tlbflush.h>
  31
  32 static mempool_t *page_pool, *isa_page_pool;
  33
  34 static void *mempool_alloc_pages_isa(gfp_t gfp_mask, void *data)
  35 {
  36         return mempool_alloc_pages(gfp_mask | GFP_DMA, data);
  37 }
  38
  39 /*
  40  * Virtual_count is not a pure "count".
  41  *  0 means that it is not mapped, and has not been mapped
  42  *    since a TLB flush - it is usable.
  43  *  1 means that there are no users, but it has been mapped
  44  *    since the last TLB flush - so we can't use it.
  45  *  n means that there are (n-1) current users of it.
  46  */
  47 #ifdef CONFIG_HIGHMEM
  48
  49 unsigned long totalhigh_pages __read_mostly;
  50
  51 unsigned int nr_free_highpages (void)
  52 {
  53         pg_data_t *pgdat;
  54         unsigned int pages = 0;
  55
  56         for_each_online_pgdat(pgdat)
  57                 pages += pgdat->node_zones[ZONE_HIGHMEM].free_pages;
  58
  59         return pages;
  60 }
  61
  62 static int pkmap_count[LAST_PKMAP];
  63 static unsigned int last_pkmap_nr;
  64 static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
  65
  66 pte_t * pkmap_page_table;
  67
  68 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
  69
  70 static void flush_all_zero_pkmaps(void)
  71 {
  72         int i;
  73
  74         flush_cache_kmaps();
  75
  76         for (i = 0; i < LAST_PKMAP; i++) {
  77                 struct page *page;
  78
  79                 /*
  80                  * zero means we don't have anything to do,
  81                  * >1 means that it is still in use. Only
  82                  * a count of 1 means that it is free but
  83                  * needs to be unmapped
  84                  */
  85                 if (pkmap_count[i] != 1)
  86                         continue;
  87                 pkmap_count[i] = 0;
  88
  89                 /* sanity check */
  90                 BUG_ON(pte_none(pkmap_page_table[i]));
  91
  92                 /*
  93                  * Don't need an atomic fetch-and-clear op here;
  94                  * no-one has the page mapped, and cannot get at
  95                  * its virtual address (and hence PTE) without first
  96                  * getting the kmap_lock (which is held here).
  97                  * So no dangers, even with speculative execution.
  98                  */
  99                 page = pte_page(pkmap_page_table[i]);
 100                 pte_clear(&init_mm, (unsigned long)page_address(page),
 101                           &pkmap_page_table[i]);
 102
 103                 set_page_address(page, NULL);
 104         }
 105         flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
 106 }
 107
 108 static inline unsigned long map_new_virtual(struct page *page)
 109 {
 110         unsigned long vaddr;
 111         int count;
 112
 113 start:
 114         count = LAST_PKMAP;
 115         /* Find an empty entry */
 116         for (;;) {
 117                 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
 118                 if (!last_pkmap_nr) {
 119                         flush_all_zero_pkmaps();
 120                         count = LAST_PKMAP;
 121                 }
 122                 if (!pkmap_count[last_pkmap_nr])
 123                         break;  /* Found a usable entry */
 124                 if (--count)
 125                         continue;
 126
 127                 /*
 128                  * Sleep for somebody else to unmap their entries
 129                  */
 130                 {
 131                         DECLARE_WAITQUEUE(wait, current);
 132
 133                         __set_current_state(TASK_UNINTERRUPTIBLE);
 134                         add_wait_queue(&pkmap_map_wait, &wait);
 135                         spin_unlock(&kmap_lock);
 136                         schedule();
 137                         remove_wait_queue(&pkmap_map_wait, &wait);
 138                         spin_lock(&kmap_lock);
 139
 140                         /* Somebody else might have mapped it while we slept */
 141                         if (page_address(page))
 142                                 return (unsigned long)page_address(page);
 143
 144                         /* Re-start */
 145                         goto start;
 146                 }
 147         }
 148         vaddr = PKMAP_ADDR(last_pkmap_nr);
 149         set_pte_at(&init_mm, vaddr,
 150                    &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
 151
 152         pkmap_count[last_pkmap_nr] = 1;
 153         set_page_address(page, (void *)vaddr);
 154
 155         return vaddr;
 156 }
 157
 158 void fastcall *kmap_high(struct page *page)
 159 {
 160         unsigned long vaddr;
 161
 162         /*
 163          * For highmem pages, we can't trust "virtual" until
 164          * after we have the lock.
 165          *
 166          * We cannot call this from interrupts, as it may block
 167          */
 168         spin_lock(&kmap_lock);
 169         vaddr = (unsigned long)page_address(page);
 170         if (!vaddr)
 171                 vaddr = map_new_virtual(page);
 172         pkmap_count[PKMAP_NR(vaddr)]++;
 173         BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
 174         spin_unlock(&kmap_lock);
 175         return (void*) vaddr;
 176 }
 177
 178 EXPORT_SYMBOL(kmap_high);
 179
 180 void fastcall kunmap_high(struct page *page)
 181 {
 182         unsigned long vaddr;
 183         unsigned long nr;
 184         int need_wakeup;
 185
 186         spin_lock(&kmap_lock);
 187         vaddr = (unsigned long)page_address(page);
 188         BUG_ON(!vaddr);
 189         nr = PKMAP_NR(vaddr);
 190
 191         /*
 192          * A count must never go down to zero
 193          * without a TLB flush!
 194          */
 195         need_wakeup = 0;
 196         switch (--pkmap_count[nr]) {
 197         case 0:
 198                 BUG();
 199         case 1:
 200                 /*
 201                  * Avoid an unnecessary wake_up() function call.
 202                  * The common case is pkmap_count[] == 1, but
 203                  * no waiters.
 204                  * The tasks queued in the wait-queue are guarded
 205                  * by both the lock in the wait-queue-head and by
 206                  * the kmap_lock.  As the kmap_lock is held here,
 207                  * no need for the wait-queue-head's lock.  Simply
 208                  * test if the queue is empty.
 209                  */
 210                 need_wakeup = waitqueue_active(&pkmap_map_wait);
 211         }
 212         spin_unlock(&kmap_lock);
 213
 214         /* do wake-up, if needed, race-free outside of the spin lock */
 215         if (need_wakeup)
 216                 wake_up(&pkmap_map_wait);
 217 }
 218
 219 EXPORT_SYMBOL(kunmap_high);
 220
 221 #define POOL_SIZE       64
 222
 223 static __init int init_emergency_pool(void)
 224 {
 225         struct sysinfo i;
 226         si_meminfo(&i);
 227         si_swapinfo(&i);
 228
 229         if (!i.totalhigh)
 230                 return 0;
 231
 232         page_pool = mempool_create_page_pool(POOL_SIZE, 0);
 233         BUG_ON(!page_pool);
 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, mempool_alloc_pages_isa,
 275                                        mempool_free_pages, (void *) 0);
 276         BUG_ON(!isa_page_pool);
 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                 dec_zone_page_state(bvec->bv_page, NR_BOUNCE);
 332                 mempool_free(bvec->bv_page, pool);
 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_zone_page_state(to->bv_page, 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         blk_add_trace_bio(q, *bio_orig, BLK_TA_BOUNCE);
 487
 488         /*
 489          * slow path
 490          */
 491         __blk_queue_bounce(q, bio_orig, pool);
 492 }
 493
 494 EXPORT_SYMBOL(blk_queue_bounce);
 495
 496 #if defined(HASHED_PAGE_VIRTUAL)
 497
 498 #define PA_HASH_ORDER   7
 499
 500 /*
 501  * Describes one page->virtual association
 502  */
 503 struct page_address_map {
 504         struct page *page;
 505         void *virtual;
 506         struct list_head list;
 507 };
 508
 509 /*
 510  * page_address_map freelist, allocated from page_address_maps.
 511  */
 512 static struct list_head page_address_pool;      /* freelist */
 513 static spinlock_t pool_lock;                    /* protects page_address_pool */
 514
 515 /*
 516  * Hash table bucket
 517  */
 518 static struct page_address_slot {
 519         struct list_head lh;                    /* List of page_address_maps */
 520         spinlock_t lock;                        /* Protect this bucket's list */
 521 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
 522
 523 static struct page_address_slot *page_slot(struct page *page)
 524 {
 525         return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
 526 }
 527
 528 void *page_address(struct page *page)
 529 {
 530         unsigned long flags;
 531         void *ret;
 532         struct page_address_slot *pas;
 533
 534         if (!PageHighMem(page))
 535                 return lowmem_page_address(page);
 536
 537         pas = page_slot(page);
 538         ret = NULL;
 539         spin_lock_irqsave(&pas->lock, flags);
 540         if (!list_empty(&pas->lh)) {
 541                 struct page_address_map *pam;
 542
 543                 list_for_each_entry(pam, &pas->lh, list) {
 544                         if (pam->page == page) {
 545                                 ret = pam->virtual;
 546                                 goto done;
 547                         }
 548                 }
 549         }
 550 done:
 551         spin_unlock_irqrestore(&pas->lock, flags);
 552         return ret;
 553 }
 554
 555 EXPORT_SYMBOL(page_address);
 556
 557 void set_page_address(struct page *page, void *virtual)
 558 {
 559         unsigned long flags;
 560         struct page_address_slot *pas;
 561         struct page_address_map *pam;
 562
 563         BUG_ON(!PageHighMem(page));
 564
 565         pas = page_slot(page);
 566         if (virtual) {          /* Add */
 567                 BUG_ON(list_empty(&page_address_pool));
 568
 569                 spin_lock_irqsave(&pool_lock, flags);
 570                 pam = list_entry(page_address_pool.next,
 571                                 struct page_address_map, list);
 572                 list_del(&pam->list);
 573                 spin_unlock_irqrestore(&pool_lock, flags);
 574
 575                 pam->page = page;
 576                 pam->virtual = virtual;
 577
 578                 spin_lock_irqsave(&pas->lock, flags);
 579                 list_add_tail(&pam->list, &pas->lh);
 580                 spin_unlock_irqrestore(&pas->lock, flags);
 581         } else {                /* Remove */
 582                 spin_lock_irqsave(&pas->lock, flags);
 583                 list_for_each_entry(pam, &pas->lh, list) {
 584                         if (pam->page == page) {
 585                                 list_del(&pam->list);
 586                                 spin_unlock_irqrestore(&pas->lock, flags);
 587                                 spin_lock_irqsave(&pool_lock, flags);
 588                                 list_add_tail(&pam->list, &page_address_pool);
 589                                 spin_unlock_irqrestore(&pool_lock, flags);
 590                                 goto done;
 591                         }
 592                 }
 593                 spin_unlock_irqrestore(&pas->lock, flags);
 594         }
 595 done:
 596         return;
 597 }
 598
 599 static struct page_address_map page_address_maps[LAST_PKMAP];
 600
 601 void __init page_address_init(void)
 602 {
 603         int i;
 604
 605         INIT_LIST_HEAD(&page_address_pool);
 606         for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)
 607                 list_add(&page_address_maps[i].list, &page_address_pool);
 608         for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
 609                 INIT_LIST_HEAD(&page_address_htable[i].lh);
 610                 spin_lock_init(&page_address_htable[i].lock);
 611         }
 612         spin_lock_init(&pool_lock);
 613 }
 614
 615 #endif  /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */