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