xref: /openbmc/linux/mm/highmem.c (revision d5cb9783536a41df9f9cba5b0a1d78047ed787f7)
1 /*
2  * High memory handling common code and variables.
3  *
4  * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
5  *          Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
6  *
7  *
8  * Redesigned the x86 32-bit VM architecture to deal with
9  * 64-bit physical space. With current x86 CPUs this
10  * means up to 64 Gigabytes physical RAM.
11  *
12  * Rewrote high memory support to move the page cache into
13  * high memory. Implemented permanent (schedulable) kmaps
14  * based on Linus' idea.
15  *
16  * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
17  */
18 
19 #include <linux/mm.h>
20 #include <linux/module.h>
21 #include <linux/swap.h>
22 #include <linux/bio.h>
23 #include <linux/pagemap.h>
24 #include <linux/mempool.h>
25 #include <linux/blkdev.h>
26 #include <linux/init.h>
27 #include <linux/hash.h>
28 #include <linux/highmem.h>
29 #include <asm/tlbflush.h>
30 
31 static mempool_t *page_pool, *isa_page_pool;
32 
33 static void *page_pool_alloc_isa(gfp_t gfp_mask, void *data)
34 {
35 	return alloc_page(gfp_mask | GFP_DMA);
36 }
37 
38 static void page_pool_free(void *page, void *data)
39 {
40 	__free_page(page);
41 }
42 
43 /*
44  * Virtual_count is not a pure "count".
45  *  0 means that it is not mapped, and has not been mapped
46  *    since a TLB flush - it is usable.
47  *  1 means that there are no users, but it has been mapped
48  *    since the last TLB flush - so we can't use it.
49  *  n means that there are (n-1) current users of it.
50  */
51 #ifdef CONFIG_HIGHMEM
52 
53 static void *page_pool_alloc(gfp_t gfp_mask, void *data)
54 {
55 	return alloc_page(gfp_mask);
56 }
57 
58 static int pkmap_count[LAST_PKMAP];
59 static unsigned int last_pkmap_nr;
60 static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
61 
62 pte_t * pkmap_page_table;
63 
64 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
65 
66 static void flush_all_zero_pkmaps(void)
67 {
68 	int i;
69 
70 	flush_cache_kmaps();
71 
72 	for (i = 0; i < LAST_PKMAP; i++) {
73 		struct page *page;
74 
75 		/*
76 		 * zero means we don't have anything to do,
77 		 * >1 means that it is still in use. Only
78 		 * a count of 1 means that it is free but
79 		 * needs to be unmapped
80 		 */
81 		if (pkmap_count[i] != 1)
82 			continue;
83 		pkmap_count[i] = 0;
84 
85 		/* sanity check */
86 		if (pte_none(pkmap_page_table[i]))
87 			BUG();
88 
89 		/*
90 		 * Don't need an atomic fetch-and-clear op here;
91 		 * no-one has the page mapped, and cannot get at
92 		 * its virtual address (and hence PTE) without first
93 		 * getting the kmap_lock (which is held here).
94 		 * So no dangers, even with speculative execution.
95 		 */
96 		page = pte_page(pkmap_page_table[i]);
97 		pte_clear(&init_mm, (unsigned long)page_address(page),
98 			  &pkmap_page_table[i]);
99 
100 		set_page_address(page, NULL);
101 	}
102 	flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
103 }
104 
105 static inline unsigned long map_new_virtual(struct page *page)
106 {
107 	unsigned long vaddr;
108 	int count;
109 
110 start:
111 	count = LAST_PKMAP;
112 	/* Find an empty entry */
113 	for (;;) {
114 		last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
115 		if (!last_pkmap_nr) {
116 			flush_all_zero_pkmaps();
117 			count = LAST_PKMAP;
118 		}
119 		if (!pkmap_count[last_pkmap_nr])
120 			break;	/* Found a usable entry */
121 		if (--count)
122 			continue;
123 
124 		/*
125 		 * Sleep for somebody else to unmap their entries
126 		 */
127 		{
128 			DECLARE_WAITQUEUE(wait, current);
129 
130 			__set_current_state(TASK_UNINTERRUPTIBLE);
131 			add_wait_queue(&pkmap_map_wait, &wait);
132 			spin_unlock(&kmap_lock);
133 			schedule();
134 			remove_wait_queue(&pkmap_map_wait, &wait);
135 			spin_lock(&kmap_lock);
136 
137 			/* Somebody else might have mapped it while we slept */
138 			if (page_address(page))
139 				return (unsigned long)page_address(page);
140 
141 			/* Re-start */
142 			goto start;
143 		}
144 	}
145 	vaddr = PKMAP_ADDR(last_pkmap_nr);
146 	set_pte_at(&init_mm, vaddr,
147 		   &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
148 
149 	pkmap_count[last_pkmap_nr] = 1;
150 	set_page_address(page, (void *)vaddr);
151 
152 	return vaddr;
153 }
154 
155 void fastcall *kmap_high(struct page *page)
156 {
157 	unsigned long vaddr;
158 
159 	/*
160 	 * For highmem pages, we can't trust "virtual" until
161 	 * after we have the lock.
162 	 *
163 	 * We cannot call this from interrupts, as it may block
164 	 */
165 	spin_lock(&kmap_lock);
166 	vaddr = (unsigned long)page_address(page);
167 	if (!vaddr)
168 		vaddr = map_new_virtual(page);
169 	pkmap_count[PKMAP_NR(vaddr)]++;
170 	if (pkmap_count[PKMAP_NR(vaddr)] < 2)
171 		BUG();
172 	spin_unlock(&kmap_lock);
173 	return (void*) vaddr;
174 }
175 
176 EXPORT_SYMBOL(kmap_high);
177 
178 void fastcall kunmap_high(struct page *page)
179 {
180 	unsigned long vaddr;
181 	unsigned long nr;
182 	int need_wakeup;
183 
184 	spin_lock(&kmap_lock);
185 	vaddr = (unsigned long)page_address(page);
186 	if (!vaddr)
187 		BUG();
188 	nr = PKMAP_NR(vaddr);
189 
190 	/*
191 	 * A count must never go down to zero
192 	 * without a TLB flush!
193 	 */
194 	need_wakeup = 0;
195 	switch (--pkmap_count[nr]) {
196 	case 0:
197 		BUG();
198 	case 1:
199 		/*
200 		 * Avoid an unnecessary wake_up() function call.
201 		 * The common case is pkmap_count[] == 1, but
202 		 * no waiters.
203 		 * The tasks queued in the wait-queue are guarded
204 		 * by both the lock in the wait-queue-head and by
205 		 * the kmap_lock.  As the kmap_lock is held here,
206 		 * no need for the wait-queue-head's lock.  Simply
207 		 * test if the queue is empty.
208 		 */
209 		need_wakeup = waitqueue_active(&pkmap_map_wait);
210 	}
211 	spin_unlock(&kmap_lock);
212 
213 	/* do wake-up, if needed, race-free outside of the spin lock */
214 	if (need_wakeup)
215 		wake_up(&pkmap_map_wait);
216 }
217 
218 EXPORT_SYMBOL(kunmap_high);
219 
220 #define POOL_SIZE	64
221 
222 static __init int init_emergency_pool(void)
223 {
224 	struct sysinfo i;
225 	si_meminfo(&i);
226 	si_swapinfo(&i);
227 
228 	if (!i.totalhigh)
229 		return 0;
230 
231 	page_pool = mempool_create(POOL_SIZE, page_pool_alloc, page_pool_free, NULL);
232 	if (!page_pool)
233 		BUG();
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, page_pool_alloc_isa, page_pool_free, NULL);
275 	if (!isa_page_pool)
276 		BUG();
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 		mempool_free(bvec->bv_page, pool);
332 		dec_page_state(nr_bounce);
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_page_state(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 	/*
487 	 * slow path
488 	 */
489 	__blk_queue_bounce(q, bio_orig, pool);
490 }
491 
492 EXPORT_SYMBOL(blk_queue_bounce);
493 
494 #if defined(HASHED_PAGE_VIRTUAL)
495 
496 #define PA_HASH_ORDER	7
497 
498 /*
499  * Describes one page->virtual association
500  */
501 struct page_address_map {
502 	struct page *page;
503 	void *virtual;
504 	struct list_head list;
505 };
506 
507 /*
508  * page_address_map freelist, allocated from page_address_maps.
509  */
510 static struct list_head page_address_pool;	/* freelist */
511 static spinlock_t pool_lock;			/* protects page_address_pool */
512 
513 /*
514  * Hash table bucket
515  */
516 static struct page_address_slot {
517 	struct list_head lh;			/* List of page_address_maps */
518 	spinlock_t lock;			/* Protect this bucket's list */
519 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
520 
521 static struct page_address_slot *page_slot(struct page *page)
522 {
523 	return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
524 }
525 
526 void *page_address(struct page *page)
527 {
528 	unsigned long flags;
529 	void *ret;
530 	struct page_address_slot *pas;
531 
532 	if (!PageHighMem(page))
533 		return lowmem_page_address(page);
534 
535 	pas = page_slot(page);
536 	ret = NULL;
537 	spin_lock_irqsave(&pas->lock, flags);
538 	if (!list_empty(&pas->lh)) {
539 		struct page_address_map *pam;
540 
541 		list_for_each_entry(pam, &pas->lh, list) {
542 			if (pam->page == page) {
543 				ret = pam->virtual;
544 				goto done;
545 			}
546 		}
547 	}
548 done:
549 	spin_unlock_irqrestore(&pas->lock, flags);
550 	return ret;
551 }
552 
553 EXPORT_SYMBOL(page_address);
554 
555 void set_page_address(struct page *page, void *virtual)
556 {
557 	unsigned long flags;
558 	struct page_address_slot *pas;
559 	struct page_address_map *pam;
560 
561 	BUG_ON(!PageHighMem(page));
562 
563 	pas = page_slot(page);
564 	if (virtual) {		/* Add */
565 		BUG_ON(list_empty(&page_address_pool));
566 
567 		spin_lock_irqsave(&pool_lock, flags);
568 		pam = list_entry(page_address_pool.next,
569 				struct page_address_map, list);
570 		list_del(&pam->list);
571 		spin_unlock_irqrestore(&pool_lock, flags);
572 
573 		pam->page = page;
574 		pam->virtual = virtual;
575 
576 		spin_lock_irqsave(&pas->lock, flags);
577 		list_add_tail(&pam->list, &pas->lh);
578 		spin_unlock_irqrestore(&pas->lock, flags);
579 	} else {		/* Remove */
580 		spin_lock_irqsave(&pas->lock, flags);
581 		list_for_each_entry(pam, &pas->lh, list) {
582 			if (pam->page == page) {
583 				list_del(&pam->list);
584 				spin_unlock_irqrestore(&pas->lock, flags);
585 				spin_lock_irqsave(&pool_lock, flags);
586 				list_add_tail(&pam->list, &page_address_pool);
587 				spin_unlock_irqrestore(&pool_lock, flags);
588 				goto done;
589 			}
590 		}
591 		spin_unlock_irqrestore(&pas->lock, flags);
592 	}
593 done:
594 	return;
595 }
596 
597 static struct page_address_map page_address_maps[LAST_PKMAP];
598 
599 void __init page_address_init(void)
600 {
601 	int i;
602 
603 	INIT_LIST_HEAD(&page_address_pool);
604 	for (i = 0; i < ARRAY_SIZE(page_address_maps); i++)
605 		list_add(&page_address_maps[i].list, &page_address_pool);
606 	for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
607 		INIT_LIST_HEAD(&page_address_htable[i].lh);
608 		spin_lock_init(&page_address_htable[i].lock);
609 	}
610 	spin_lock_init(&pool_lock);
611 }
612 
613 #endif	/* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */
614