mm/highmem.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * High memory handling common code and variables.
   4  *
   5  * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
   6  *          Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
   7  *
   8  *
   9  * Redesigned the x86 32-bit VM architecture to deal with
  10  * 64-bit physical space. With current x86 CPUs this
  11  * means up to 64 Gigabytes physical RAM.
  12  *
  13  * Rewrote high memory support to move the page cache into
  14  * high memory. Implemented permanent (schedulable) kmaps
  15  * based on Linus' idea.
  16  *
  17  * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
  18  */
  19
  20 #include <linux/mm.h>
  21 #include <linux/export.h>
  22 #include <linux/swap.h>
  23 #include <linux/bio.h>
  24 #include <linux/pagemap.h>
  25 #include <linux/mempool.h>
  26 #include <linux/blkdev.h>
  27 #include <linux/init.h>
  28 #include <linux/hash.h>
  29 #include <linux/highmem.h>
  30 #include <linux/kgdb.h>
  31 #include <asm/tlbflush.h>
  32 #include <linux/vmalloc.h>
  33
  34 /*
  35  * Virtual_count is not a pure "count".
  36  *  0 means that it is not mapped, and has not been mapped
  37  *    since a TLB flush - it is usable.
  38  *  1 means that there are no users, but it has been mapped
  39  *    since the last TLB flush - so we can't use it.
  40  *  n means that there are (n-1) current users of it.
  41  */
  42 #ifdef CONFIG_HIGHMEM
  43
  44 /*
  45  * Architecture with aliasing data cache may define the following family of
  46  * helper functions in its asm/highmem.h to control cache color of virtual
  47  * addresses where physical memory pages are mapped by kmap.
  48  */
  49 #ifndef get_pkmap_color
  50
  51 /*
  52  * Determine color of virtual address where the page should be mapped.
  53  */
  54 static inline unsigned int get_pkmap_color(struct page *page)
  55 {
  56         return 0;
  57 }
  58 #define get_pkmap_color get_pkmap_color
  59
  60 /*
  61  * Get next index for mapping inside PKMAP region for page with given color.
  62  */
  63 static inline unsigned int get_next_pkmap_nr(unsigned int color)
  64 {
  65         static unsigned int last_pkmap_nr;
  66
  67         last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
  68         return last_pkmap_nr;
  69 }
  70
  71 /*
  72  * Determine if page index inside PKMAP region (pkmap_nr) of given color
  73  * has wrapped around PKMAP region end. When this happens an attempt to
  74  * flush all unused PKMAP slots is made.
  75  */
  76 static inline int no_more_pkmaps(unsigned int pkmap_nr, unsigned int color)
  77 {
  78         return pkmap_nr == 0;
  79 }
  80
  81 /*
  82  * Get the number of PKMAP entries of the given color. If no free slot is
  83  * found after checking that many entries, kmap will sleep waiting for
  84  * someone to call kunmap and free PKMAP slot.
  85  */
  86 static inline int get_pkmap_entries_count(unsigned int color)
  87 {
  88         return LAST_PKMAP;
  89 }
  90
  91 /*
  92  * Get head of a wait queue for PKMAP entries of the given color.
  93  * Wait queues for different mapping colors should be independent to avoid
  94  * unnecessary wakeups caused by freeing of slots of other colors.
  95  */
  96 static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color)
  97 {
  98         static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
  99
 100         return &pkmap_map_wait;
 101 }
 102 #endif
 103
 104 atomic_long_t _totalhigh_pages __read_mostly;
 105 EXPORT_SYMBOL(_totalhigh_pages);
 106
 107 unsigned int __nr_free_highpages(void)
 108 {
 109         struct zone *zone;
 110         unsigned int pages = 0;
 111
 112         for_each_populated_zone(zone) {
 113                 if (is_highmem(zone))
 114                         pages += zone_page_state(zone, NR_FREE_PAGES);
 115         }
 116
 117         return pages;
 118 }
 119
 120 static int pkmap_count[LAST_PKMAP];
 121 static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
 122
 123 pte_t *pkmap_page_table;
 124
 125 /*
 126  * Most architectures have no use for kmap_high_get(), so let's abstract
 127  * the disabling of IRQ out of the locking in that case to save on a
 128  * potential useless overhead.
 129  */
 130 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
 131 #define lock_kmap()             spin_lock_irq(&kmap_lock)
 132 #define unlock_kmap()           spin_unlock_irq(&kmap_lock)
 133 #define lock_kmap_any(flags)    spin_lock_irqsave(&kmap_lock, flags)
 134 #define unlock_kmap_any(flags)  spin_unlock_irqrestore(&kmap_lock, flags)
 135 #else
 136 #define lock_kmap()             spin_lock(&kmap_lock)
 137 #define unlock_kmap()           spin_unlock(&kmap_lock)
 138 #define lock_kmap_any(flags)    \
 139                 do { spin_lock(&kmap_lock); (void)(flags); } while (0)
 140 #define unlock_kmap_any(flags)  \
 141                 do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
 142 #endif
 143
 144 struct page *__kmap_to_page(void *vaddr)
 145 {
 146         unsigned long addr = (unsigned long)vaddr;
 147
 148         if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) {
 149                 int i = PKMAP_NR(addr);
 150
 151                 return pte_page(pkmap_page_table[i]);
 152         }
 153
 154         return virt_to_page(addr);
 155 }
 156 EXPORT_SYMBOL(__kmap_to_page);
 157
 158 static void flush_all_zero_pkmaps(void)
 159 {
 160         int i;
 161         int need_flush = 0;
 162
 163         flush_cache_kmaps();
 164
 165         for (i = 0; i < LAST_PKMAP; i++) {
 166                 struct page *page;
 167
 168                 /*
 169                  * zero means we don't have anything to do,
 170                  * >1 means that it is still in use. Only
 171                  * a count of 1 means that it is free but
 172                  * needs to be unmapped
 173                  */
 174                 if (pkmap_count[i] != 1)
 175                         continue;
 176                 pkmap_count[i] = 0;
 177
 178                 /* sanity check */
 179                 BUG_ON(pte_none(pkmap_page_table[i]));
 180
 181                 /*
 182                  * Don't need an atomic fetch-and-clear op here;
 183                  * no-one has the page mapped, and cannot get at
 184                  * its virtual address (and hence PTE) without first
 185                  * getting the kmap_lock (which is held here).
 186                  * So no dangers, even with speculative execution.
 187                  */
 188                 page = pte_page(pkmap_page_table[i]);
 189                 pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]);
 190
 191                 set_page_address(page, NULL);
 192                 need_flush = 1;
 193         }
 194         if (need_flush)
 195                 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
 196 }
 197
 198 void __kmap_flush_unused(void)
 199 {
 200         lock_kmap();
 201         flush_all_zero_pkmaps();
 202         unlock_kmap();
 203 }
 204
 205 static inline unsigned long map_new_virtual(struct page *page)
 206 {
 207         unsigned long vaddr;
 208         int count;
 209         unsigned int last_pkmap_nr;
 210         unsigned int color = get_pkmap_color(page);
 211
 212 start:
 213         count = get_pkmap_entries_count(color);
 214         /* Find an empty entry */
 215         for (;;) {
 216                 last_pkmap_nr = get_next_pkmap_nr(color);
 217                 if (no_more_pkmaps(last_pkmap_nr, color)) {
 218                         flush_all_zero_pkmaps();
 219                         count = get_pkmap_entries_count(color);
 220                 }
 221                 if (!pkmap_count[last_pkmap_nr])
 222                         break;  /* Found a usable entry */
 223                 if (--count)
 224                         continue;
 225
 226                 /*
 227                  * Sleep for somebody else to unmap their entries
 228                  */
 229                 {
 230                         DECLARE_WAITQUEUE(wait, current);
 231                         wait_queue_head_t *pkmap_map_wait =
 232                                 get_pkmap_wait_queue_head(color);
 233
 234                         __set_current_state(TASK_UNINTERRUPTIBLE);
 235                         add_wait_queue(pkmap_map_wait, &wait);
 236                         unlock_kmap();
 237                         schedule();
 238                         remove_wait_queue(pkmap_map_wait, &wait);
 239                         lock_kmap();
 240
 241                         /* Somebody else might have mapped it while we slept */
 242                         if (page_address(page))
 243                                 return (unsigned long)page_address(page);
 244
 245                         /* Re-start */
 246                         goto start;
 247                 }
 248         }
 249         vaddr = PKMAP_ADDR(last_pkmap_nr);
 250         set_pte_at(&init_mm, vaddr,
 251                    &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
 252
 253         pkmap_count[last_pkmap_nr] = 1;
 254         set_page_address(page, (void *)vaddr);
 255
 256         return vaddr;
 257 }
 258
 259 /**
 260  * kmap_high - map a highmem page into memory
 261  * @page: &struct page to map
 262  *
 263  * Returns the page's virtual memory address.
 264  *
 265  * We cannot call this from interrupts, as it may block.
 266  */
 267 void *kmap_high(struct page *page)
 268 {
 269         unsigned long vaddr;
 270
 271         /*
 272          * For highmem pages, we can't trust "virtual" until
 273          * after we have the lock.
 274          */
 275         lock_kmap();
 276         vaddr = (unsigned long)page_address(page);
 277         if (!vaddr)
 278                 vaddr = map_new_virtual(page);
 279         pkmap_count[PKMAP_NR(vaddr)]++;
 280         BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
 281         unlock_kmap();
 282         return (void *) vaddr;
 283 }
 284 EXPORT_SYMBOL(kmap_high);
 285
 286 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
 287 /**
 288  * kmap_high_get - pin a highmem page into memory
 289  * @page: &struct page to pin
 290  *
 291  * Returns the page's current virtual memory address, or NULL if no mapping
 292  * exists.  If and only if a non null address is returned then a
 293  * matching call to kunmap_high() is necessary.
 294  *
 295  * This can be called from any context.
 296  */
 297 void *kmap_high_get(struct page *page)
 298 {
 299         unsigned long vaddr, flags;
 300
 301         lock_kmap_any(flags);
 302         vaddr = (unsigned long)page_address(page);
 303         if (vaddr) {
 304                 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
 305                 pkmap_count[PKMAP_NR(vaddr)]++;
 306         }
 307         unlock_kmap_any(flags);
 308         return (void *) vaddr;
 309 }
 310 #endif
 311
 312 /**
 313  * kunmap_high - unmap a highmem page into memory
 314  * @page: &struct page to unmap
 315  *
 316  * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
 317  * only from user context.
 318  */
 319 void kunmap_high(struct page *page)
 320 {
 321         unsigned long vaddr;
 322         unsigned long nr;
 323         unsigned long flags;
 324         int need_wakeup;
 325         unsigned int color = get_pkmap_color(page);
 326         wait_queue_head_t *pkmap_map_wait;
 327
 328         lock_kmap_any(flags);
 329         vaddr = (unsigned long)page_address(page);
 330         BUG_ON(!vaddr);
 331         nr = PKMAP_NR(vaddr);
 332
 333         /*
 334          * A count must never go down to zero
 335          * without a TLB flush!
 336          */
 337         need_wakeup = 0;
 338         switch (--pkmap_count[nr]) {
 339         case 0:
 340                 BUG();
 341         case 1:
 342                 /*
 343                  * Avoid an unnecessary wake_up() function call.
 344                  * The common case is pkmap_count[] == 1, but
 345                  * no waiters.
 346                  * The tasks queued in the wait-queue are guarded
 347                  * by both the lock in the wait-queue-head and by
 348                  * the kmap_lock.  As the kmap_lock is held here,
 349                  * no need for the wait-queue-head's lock.  Simply
 350                  * test if the queue is empty.
 351                  */
 352                 pkmap_map_wait = get_pkmap_wait_queue_head(color);
 353                 need_wakeup = waitqueue_active(pkmap_map_wait);
 354         }
 355         unlock_kmap_any(flags);
 356
 357         /* do wake-up, if needed, race-free outside of the spin lock */
 358         if (need_wakeup)
 359                 wake_up(pkmap_map_wait);
 360 }
 361 EXPORT_SYMBOL(kunmap_high);
 362
 363 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 364 void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
 365                 unsigned start2, unsigned end2)
 366 {
 367         unsigned int i;
 368
 369         BUG_ON(end1 > page_size(page) || end2 > page_size(page));
 370
 371         if (start1 >= end1)
 372                 start1 = end1 = 0;
 373         if (start2 >= end2)
 374                 start2 = end2 = 0;
 375
 376         for (i = 0; i < compound_nr(page); i++) {
 377                 void *kaddr = NULL;
 378
 379                 if (start1 >= PAGE_SIZE) {
 380                         start1 -= PAGE_SIZE;
 381                         end1 -= PAGE_SIZE;
 382                 } else {
 383                         unsigned this_end = min_t(unsigned, end1, PAGE_SIZE);
 384
 385                         if (end1 > start1) {
 386                                 kaddr = kmap_atomic(page + i);
 387                                 memset(kaddr + start1, 0, this_end - start1);
 388                         }
 389                         end1 -= this_end;
 390                         start1 = 0;
 391                 }
 392
 393                 if (start2 >= PAGE_SIZE) {
 394                         start2 -= PAGE_SIZE;
 395                         end2 -= PAGE_SIZE;
 396                 } else {
 397                         unsigned this_end = min_t(unsigned, end2, PAGE_SIZE);
 398
 399                         if (end2 > start2) {
 400                                 if (!kaddr)
 401                                         kaddr = kmap_atomic(page + i);
 402                                 memset(kaddr + start2, 0, this_end - start2);
 403                         }
 404                         end2 -= this_end;
 405                         start2 = 0;
 406                 }
 407
 408                 if (kaddr) {
 409                         kunmap_atomic(kaddr);
 410                         flush_dcache_page(page + i);
 411                 }
 412
 413                 if (!end1 && !end2)
 414                         break;
 415         }
 416
 417         BUG_ON((start1 | start2 | end1 | end2) != 0);
 418 }
 419 EXPORT_SYMBOL(zero_user_segments);
 420 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 421 #endif /* CONFIG_HIGHMEM */
 422
 423 #ifdef CONFIG_KMAP_LOCAL
 424
 425 #include <asm/kmap_size.h>
 426
 427 /*
 428  * With DEBUG_KMAP_LOCAL the stack depth is doubled and every second
 429  * slot is unused which acts as a guard page
 430  */
 431 #ifdef CONFIG_DEBUG_KMAP_LOCAL
 432 # define KM_INCR        2
 433 #else
 434 # define KM_INCR        1
 435 #endif
 436
 437 static inline int kmap_local_idx_push(void)
 438 {
 439         WARN_ON_ONCE(in_hardirq() && !irqs_disabled());
 440         current->kmap_ctrl.idx += KM_INCR;
 441         BUG_ON(current->kmap_ctrl.idx >= KM_MAX_IDX);
 442         return current->kmap_ctrl.idx - 1;
 443 }
 444
 445 static inline int kmap_local_idx(void)
 446 {
 447         return current->kmap_ctrl.idx - 1;
 448 }
 449
 450 static inline void kmap_local_idx_pop(void)
 451 {
 452         current->kmap_ctrl.idx -= KM_INCR;
 453         BUG_ON(current->kmap_ctrl.idx < 0);
 454 }
 455
 456 #ifndef arch_kmap_local_post_map
 457 # define arch_kmap_local_post_map(vaddr, pteval)        do { } while (0)
 458 #endif
 459
 460 #ifndef arch_kmap_local_pre_unmap
 461 # define arch_kmap_local_pre_unmap(vaddr)               do { } while (0)
 462 #endif
 463
 464 #ifndef arch_kmap_local_post_unmap
 465 # define arch_kmap_local_post_unmap(vaddr)              do { } while (0)
 466 #endif
 467
 468 #ifndef arch_kmap_local_map_idx
 469 #define arch_kmap_local_map_idx(idx, pfn)       kmap_local_calc_idx(idx)
 470 #endif
 471
 472 #ifndef arch_kmap_local_unmap_idx
 473 #define arch_kmap_local_unmap_idx(idx, vaddr)   kmap_local_calc_idx(idx)
 474 #endif
 475
 476 #ifndef arch_kmap_local_high_get
 477 static inline void *arch_kmap_local_high_get(struct page *page)
 478 {
 479         return NULL;
 480 }
 481 #endif
 482
 483 #ifndef arch_kmap_local_set_pte
 484 #define arch_kmap_local_set_pte(mm, vaddr, ptep, ptev)  \
 485         set_pte_at(mm, vaddr, ptep, ptev)
 486 #endif
 487
 488 /* Unmap a local mapping which was obtained by kmap_high_get() */
 489 static inline bool kmap_high_unmap_local(unsigned long vaddr)
 490 {
 491 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
 492         if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
 493                 kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
 494                 return true;
 495         }
 496 #endif
 497         return false;
 498 }
 499
 500 static inline int kmap_local_calc_idx(int idx)
 501 {
 502         return idx + KM_MAX_IDX * smp_processor_id();
 503 }
 504
 505 static pte_t *__kmap_pte;
 506
 507 static pte_t *kmap_get_pte(void)
 508 {
 509         if (!__kmap_pte)
 510                 __kmap_pte = virt_to_kpte(__fix_to_virt(FIX_KMAP_BEGIN));
 511         return __kmap_pte;
 512 }
 513
 514 void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot)
 515 {
 516         pte_t pteval, *kmap_pte = kmap_get_pte();
 517         unsigned long vaddr;
 518         int idx;
 519
 520         /*
 521          * Disable migration so resulting virtual address is stable
 522          * across preemption.
 523          */
 524         migrate_disable();
 525         preempt_disable();
 526         idx = arch_kmap_local_map_idx(kmap_local_idx_push(), pfn);
 527         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 528         BUG_ON(!pte_none(*(kmap_pte - idx)));
 529         pteval = pfn_pte(pfn, prot);
 530         arch_kmap_local_set_pte(&init_mm, vaddr, kmap_pte - idx, pteval);
 531         arch_kmap_local_post_map(vaddr, pteval);
 532         current->kmap_ctrl.pteval[kmap_local_idx()] = pteval;
 533         preempt_enable();
 534
 535         return (void *)vaddr;
 536 }
 537 EXPORT_SYMBOL_GPL(__kmap_local_pfn_prot);
 538
 539 void *__kmap_local_page_prot(struct page *page, pgprot_t prot)
 540 {
 541         void *kmap;
 542
 543         /*
 544          * To broaden the usage of the actual kmap_local() machinery always map
 545          * pages when debugging is enabled and the architecture has no problems
 546          * with alias mappings.
 547          */
 548         if (!IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) && !PageHighMem(page))
 549                 return page_address(page);
 550
 551         /* Try kmap_high_get() if architecture has it enabled */
 552         kmap = arch_kmap_local_high_get(page);
 553         if (kmap)
 554                 return kmap;
 555
 556         return __kmap_local_pfn_prot(page_to_pfn(page), prot);
 557 }
 558 EXPORT_SYMBOL(__kmap_local_page_prot);
 559
 560 void kunmap_local_indexed(void *vaddr)
 561 {
 562         unsigned long addr = (unsigned long) vaddr & PAGE_MASK;
 563         pte_t *kmap_pte = kmap_get_pte();
 564         int idx;
 565
 566         if (addr < __fix_to_virt(FIX_KMAP_END) ||
 567             addr > __fix_to_virt(FIX_KMAP_BEGIN)) {
 568                 if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP)) {
 569                         /* This _should_ never happen! See above. */
 570                         WARN_ON_ONCE(1);
 571                         return;
 572                 }
 573                 /*
 574                  * Handle mappings which were obtained by kmap_high_get()
 575                  * first as the virtual address of such mappings is below
 576                  * PAGE_OFFSET. Warn for all other addresses which are in
 577                  * the user space part of the virtual address space.
 578                  */
 579                 if (!kmap_high_unmap_local(addr))
 580                         WARN_ON_ONCE(addr < PAGE_OFFSET);
 581                 return;
 582         }
 583
 584         preempt_disable();
 585         idx = arch_kmap_local_unmap_idx(kmap_local_idx(), addr);
 586         WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
 587
 588         arch_kmap_local_pre_unmap(addr);
 589         pte_clear(&init_mm, addr, kmap_pte - idx);
 590         arch_kmap_local_post_unmap(addr);
 591         current->kmap_ctrl.pteval[kmap_local_idx()] = __pte(0);
 592         kmap_local_idx_pop();
 593         preempt_enable();
 594         migrate_enable();
 595 }
 596 EXPORT_SYMBOL(kunmap_local_indexed);
 597
 598 /*
 599  * Invoked before switch_to(). This is safe even when during or after
 600  * clearing the maps an interrupt which needs a kmap_local happens because
 601  * the task::kmap_ctrl.idx is not modified by the unmapping code so a
 602  * nested kmap_local will use the next unused index and restore the index
 603  * on unmap. The already cleared kmaps of the outgoing task are irrelevant
 604  * because the interrupt context does not know about them. The same applies
 605  * when scheduling back in for an interrupt which happens before the
 606  * restore is complete.
 607  */
 608 void __kmap_local_sched_out(void)
 609 {
 610         struct task_struct *tsk = current;
 611         pte_t *kmap_pte = kmap_get_pte();
 612         int i;
 613
 614         /* Clear kmaps */
 615         for (i = 0; i < tsk->kmap_ctrl.idx; i++) {
 616                 pte_t pteval = tsk->kmap_ctrl.pteval[i];
 617                 unsigned long addr;
 618                 int idx;
 619
 620                 /* With debug all even slots are unmapped and act as guard */
 621                 if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL) && !(i & 0x01)) {
 622                         WARN_ON_ONCE(!pte_none(pteval));
 623                         continue;
 624                 }
 625                 if (WARN_ON_ONCE(pte_none(pteval)))
 626                         continue;
 627
 628                 /*
 629                  * This is a horrible hack for XTENSA to calculate the
 630                  * coloured PTE index. Uses the PFN encoded into the pteval
 631                  * and the map index calculation because the actual mapped
 632                  * virtual address is not stored in task::kmap_ctrl.
 633                  * For any sane architecture this is optimized out.
 634                  */
 635                 idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));
 636
 637                 addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 638                 arch_kmap_local_pre_unmap(addr);
 639                 pte_clear(&init_mm, addr, kmap_pte - idx);
 640                 arch_kmap_local_post_unmap(addr);
 641         }
 642 }
 643
 644 void __kmap_local_sched_in(void)
 645 {
 646         struct task_struct *tsk = current;
 647         pte_t *kmap_pte = kmap_get_pte();
 648         int i;
 649
 650         /* Restore kmaps */
 651         for (i = 0; i < tsk->kmap_ctrl.idx; i++) {
 652                 pte_t pteval = tsk->kmap_ctrl.pteval[i];
 653                 unsigned long addr;
 654                 int idx;
 655
 656                 /* With debug all even slots are unmapped and act as guard */
 657                 if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL) && !(i & 0x01)) {
 658                         WARN_ON_ONCE(!pte_none(pteval));
 659                         continue;
 660                 }
 661                 if (WARN_ON_ONCE(pte_none(pteval)))
 662                         continue;
 663
 664                 /* See comment in __kmap_local_sched_out() */
 665                 idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));
 666                 addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 667                 set_pte_at(&init_mm, addr, kmap_pte - idx, pteval);
 668                 arch_kmap_local_post_map(addr, pteval);
 669         }
 670 }
 671
 672 void kmap_local_fork(struct task_struct *tsk)
 673 {
 674         if (WARN_ON_ONCE(tsk->kmap_ctrl.idx))
 675                 memset(&tsk->kmap_ctrl, 0, sizeof(tsk->kmap_ctrl));
 676 }
 677
 678 #endif
 679
 680 #if defined(HASHED_PAGE_VIRTUAL)
 681
 682 #define PA_HASH_ORDER   7
 683
 684 /*
 685  * Describes one page->virtual association
 686  */
 687 struct page_address_map {
 688         struct page *page;
 689         void *virtual;
 690         struct list_head list;
 691 };
 692
 693 static struct page_address_map page_address_maps[LAST_PKMAP];
 694
 695 /*
 696  * Hash table bucket
 697  */
 698 static struct page_address_slot {
 699         struct list_head lh;                    /* List of page_address_maps */
 700         spinlock_t lock;                        /* Protect this bucket's list */
 701 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
 702
 703 static struct page_address_slot *page_slot(const struct page *page)
 704 {
 705         return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
 706 }
 707
 708 /**
 709  * page_address - get the mapped virtual address of a page
 710  * @page: &struct page to get the virtual address of
 711  *
 712  * Returns the page's virtual address.
 713  */
 714 void *page_address(const struct page *page)
 715 {
 716         unsigned long flags;
 717         void *ret;
 718         struct page_address_slot *pas;
 719
 720         if (!PageHighMem(page))
 721                 return lowmem_page_address(page);
 722
 723         pas = page_slot(page);
 724         ret = NULL;
 725         spin_lock_irqsave(&pas->lock, flags);
 726         if (!list_empty(&pas->lh)) {
 727                 struct page_address_map *pam;
 728
 729                 list_for_each_entry(pam, &pas->lh, list) {
 730                         if (pam->page == page) {
 731                                 ret = pam->virtual;
 732                                 goto done;
 733                         }
 734                 }
 735         }
 736 done:
 737         spin_unlock_irqrestore(&pas->lock, flags);
 738         return ret;
 739 }
 740 EXPORT_SYMBOL(page_address);
 741
 742 /**
 743  * set_page_address - set a page's virtual address
 744  * @page: &struct page to set
 745  * @virtual: virtual address to use
 746  */
 747 void set_page_address(struct page *page, void *virtual)
 748 {
 749         unsigned long flags;
 750         struct page_address_slot *pas;
 751         struct page_address_map *pam;
 752
 753         BUG_ON(!PageHighMem(page));
 754
 755         pas = page_slot(page);
 756         if (virtual) {          /* Add */
 757                 pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
 758                 pam->page = page;
 759                 pam->virtual = virtual;
 760
 761                 spin_lock_irqsave(&pas->lock, flags);
 762                 list_add_tail(&pam->list, &pas->lh);
 763                 spin_unlock_irqrestore(&pas->lock, flags);
 764         } else {                /* Remove */
 765                 spin_lock_irqsave(&pas->lock, flags);
 766                 list_for_each_entry(pam, &pas->lh, list) {
 767                         if (pam->page == page) {
 768                                 list_del(&pam->list);
 769                                 spin_unlock_irqrestore(&pas->lock, flags);
 770                                 goto done;
 771                         }
 772                 }
 773                 spin_unlock_irqrestore(&pas->lock, flags);
 774         }
 775 done:
 776         return;
 777 }
 778
 779 void __init page_address_init(void)
 780 {
 781         int i;
 782
 783         for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
 784                 INIT_LIST_HEAD(&page_address_htable[i].lh);
 785                 spin_lock_init(&page_address_htable[i].lock);
 786         }
 787 }
 788
 789 #endif  /* defined(HASHED_PAGE_VIRTUAL) */