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_irq() && !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) */ 790