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/drivers/staging/zram/zram_drv.c

https://bitbucket.org/wisechild/galaxy-nexus
C | 732 lines | 537 code | 143 blank | 52 comment | 51 complexity | b061b07ce824f04f240ed520d2f72225 MD5 | raw file
Possible License(s): GPL-2.0, LGPL-2.0, AGPL-1.0
  1/*
  2 * Compressed RAM block device
  3 *
  4 * Copyright (C) 2008, 2009, 2010  Nitin Gupta
  5 *
  6 * This code is released using a dual license strategy: BSD/GPL
  7 * You can choose the licence that better fits your requirements.
  8 *
  9 * Released under the terms of 3-clause BSD License
 10 * Released under the terms of GNU General Public License Version 2.0
 11 *
 12 * Project home: http://compcache.googlecode.com
 13 */
 14
 15#define KMSG_COMPONENT "zram"
 16#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
 17
 18#ifdef CONFIG_ZRAM_DEBUG
 19#define DEBUG
 20#endif
 21
 22#include <linux/module.h>
 23#include <linux/kernel.h>
 24#include <linux/bio.h>
 25#include <linux/bitops.h>
 26#include <linux/blkdev.h>
 27#include <linux/buffer_head.h>
 28#include <linux/device.h>
 29#include <linux/genhd.h>
 30#include <linux/highmem.h>
 31#include <linux/slab.h>
 32#include <linux/lzo.h>
 33#include <linux/string.h>
 34#include <linux/vmalloc.h>
 35
 36#include "zram_drv.h"
 37
 38/* Globals */
 39static int zram_major;
 40struct zram *devices;
 41
 42/* Module params (documentation at end) */
 43unsigned int num_devices;
 44
 45static void zram_stat_inc(u32 *v)
 46{
 47	*v = *v + 1;
 48}
 49
 50static void zram_stat_dec(u32 *v)
 51{
 52	*v = *v - 1;
 53}
 54
 55static void zram_stat64_add(struct zram *zram, u64 *v, u64 inc)
 56{
 57	spin_lock(&zram->stat64_lock);
 58	*v = *v + inc;
 59	spin_unlock(&zram->stat64_lock);
 60}
 61
 62static void zram_stat64_sub(struct zram *zram, u64 *v, u64 dec)
 63{
 64	spin_lock(&zram->stat64_lock);
 65	*v = *v - dec;
 66	spin_unlock(&zram->stat64_lock);
 67}
 68
 69static void zram_stat64_inc(struct zram *zram, u64 *v)
 70{
 71	zram_stat64_add(zram, v, 1);
 72}
 73
 74static int zram_test_flag(struct zram *zram, u32 index,
 75			enum zram_pageflags flag)
 76{
 77	return zram->table[index].flags & BIT(flag);
 78}
 79
 80static void zram_set_flag(struct zram *zram, u32 index,
 81			enum zram_pageflags flag)
 82{
 83	zram->table[index].flags |= BIT(flag);
 84}
 85
 86static void zram_clear_flag(struct zram *zram, u32 index,
 87			enum zram_pageflags flag)
 88{
 89	zram->table[index].flags &= ~BIT(flag);
 90}
 91
 92static int page_zero_filled(void *ptr)
 93{
 94	unsigned int pos;
 95	unsigned long *page;
 96
 97	page = (unsigned long *)ptr;
 98
 99	for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) {
100		if (page[pos])
101			return 0;
102	}
103
104	return 1;
105}
106
107static void zram_set_disksize(struct zram *zram, size_t totalram_bytes)
108{
109	if (!zram->disksize) {
110		pr_info(
111		"disk size not provided. You can use disksize_kb module "
112		"param to specify size.\nUsing default: (%u%% of RAM).\n",
113		default_disksize_perc_ram
114		);
115		zram->disksize = default_disksize_perc_ram *
116					(totalram_bytes / 100);
117	}
118
119	if (zram->disksize > 2 * (totalram_bytes)) {
120		pr_info(
121		"There is little point creating a zram of greater than "
122		"twice the size of memory since we expect a 2:1 compression "
123		"ratio. Note that zram uses about 0.1%% of the size of "
124		"the disk when not in use so a huge zram is "
125		"wasteful.\n"
126		"\tMemory Size: %zu kB\n"
127		"\tSize you selected: %llu kB\n"
128		"Continuing anyway ...\n",
129		totalram_bytes >> 10, zram->disksize
130		);
131	}
132
133	zram->disksize &= PAGE_MASK;
134}
135
136static void zram_free_page(struct zram *zram, size_t index)
137{
138	u32 clen;
139	void *obj;
140
141	struct page *page = zram->table[index].page;
142	u32 offset = zram->table[index].offset;
143
144	if (unlikely(!page)) {
145		/*
146		 * No memory is allocated for zero filled pages.
147		 * Simply clear zero page flag.
148		 */
149		if (zram_test_flag(zram, index, ZRAM_ZERO)) {
150			zram_clear_flag(zram, index, ZRAM_ZERO);
151			zram_stat_dec(&zram->stats.pages_zero);
152		}
153		return;
154	}
155
156	if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
157		clen = PAGE_SIZE;
158		__free_page(page);
159		zram_clear_flag(zram, index, ZRAM_UNCOMPRESSED);
160		zram_stat_dec(&zram->stats.pages_expand);
161		goto out;
162	}
163
164	obj = kmap_atomic(page, KM_USER0) + offset;
165	clen = xv_get_object_size(obj) - sizeof(struct zobj_header);
166	kunmap_atomic(obj, KM_USER0);
167
168	xv_free(zram->mem_pool, page, offset);
169	if (clen <= PAGE_SIZE / 2)
170		zram_stat_dec(&zram->stats.good_compress);
171
172out:
173	zram_stat64_sub(zram, &zram->stats.compr_size, clen);
174	zram_stat_dec(&zram->stats.pages_stored);
175
176	zram->table[index].page = NULL;
177	zram->table[index].offset = 0;
178}
179
180static void handle_zero_page(struct page *page)
181{
182	void *user_mem;
183
184	user_mem = kmap_atomic(page, KM_USER0);
185	memset(user_mem, 0, PAGE_SIZE);
186	kunmap_atomic(user_mem, KM_USER0);
187
188	flush_dcache_page(page);
189}
190
191static void handle_uncompressed_page(struct zram *zram,
192				struct page *page, u32 index)
193{
194	unsigned char *user_mem, *cmem;
195
196	user_mem = kmap_atomic(page, KM_USER0);
197	cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
198			zram->table[index].offset;
199
200	memcpy(user_mem, cmem, PAGE_SIZE);
201	kunmap_atomic(user_mem, KM_USER0);
202	kunmap_atomic(cmem, KM_USER1);
203
204	flush_dcache_page(page);
205}
206
207static void zram_read(struct zram *zram, struct bio *bio)
208{
209
210	int i;
211	u32 index;
212	struct bio_vec *bvec;
213
214	zram_stat64_inc(zram, &zram->stats.num_reads);
215	index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
216
217	bio_for_each_segment(bvec, bio, i) {
218		int ret;
219		size_t clen;
220		struct page *page;
221		struct zobj_header *zheader;
222		unsigned char *user_mem, *cmem;
223
224		page = bvec->bv_page;
225
226		if (zram_test_flag(zram, index, ZRAM_ZERO)) {
227			handle_zero_page(page);
228			index++;
229			continue;
230		}
231
232		/* Requested page is not present in compressed area */
233		if (unlikely(!zram->table[index].page)) {
234			pr_debug("Read before write: sector=%lu, size=%u",
235				(ulong)(bio->bi_sector), bio->bi_size);
236			handle_zero_page(page);
237			index++;
238			continue;
239		}
240
241		/* Page is stored uncompressed since it's incompressible */
242		if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
243			handle_uncompressed_page(zram, page, index);
244			index++;
245			continue;
246		}
247
248		user_mem = kmap_atomic(page, KM_USER0);
249		clen = PAGE_SIZE;
250
251		cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
252				zram->table[index].offset;
253
254		ret = lzo1x_decompress_safe(
255			cmem + sizeof(*zheader),
256			xv_get_object_size(cmem) - sizeof(*zheader),
257			user_mem, &clen);
258
259		kunmap_atomic(user_mem, KM_USER0);
260		kunmap_atomic(cmem, KM_USER1);
261
262		/* Should NEVER happen. Return bio error if it does. */
263		if (unlikely(ret != LZO_E_OK)) {
264			pr_err("Decompression failed! err=%d, page=%u\n",
265				ret, index);
266			zram_stat64_inc(zram, &zram->stats.failed_reads);
267			goto out;
268		}
269
270		flush_dcache_page(page);
271		index++;
272	}
273
274	set_bit(BIO_UPTODATE, &bio->bi_flags);
275	bio_endio(bio, 0);
276	return;
277
278out:
279	bio_io_error(bio);
280}
281
282static void zram_write(struct zram *zram, struct bio *bio)
283{
284	int i;
285	u32 index;
286	struct bio_vec *bvec;
287
288	zram_stat64_inc(zram, &zram->stats.num_writes);
289	index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
290
291	bio_for_each_segment(bvec, bio, i) {
292		int ret;
293		u32 offset;
294		size_t clen;
295		struct zobj_header *zheader;
296		struct page *page, *page_store;
297		unsigned char *user_mem, *cmem, *src;
298
299		page = bvec->bv_page;
300		src = zram->compress_buffer;
301
302		/*
303		 * System overwrites unused sectors. Free memory associated
304		 * with this sector now.
305		 */
306		if (zram->table[index].page ||
307				zram_test_flag(zram, index, ZRAM_ZERO))
308			zram_free_page(zram, index);
309
310		mutex_lock(&zram->lock);
311
312		user_mem = kmap_atomic(page, KM_USER0);
313		if (page_zero_filled(user_mem)) {
314			kunmap_atomic(user_mem, KM_USER0);
315			mutex_unlock(&zram->lock);
316			zram_stat_inc(&zram->stats.pages_zero);
317			zram_set_flag(zram, index, ZRAM_ZERO);
318			index++;
319			continue;
320		}
321
322		ret = lzo1x_1_compress(user_mem, PAGE_SIZE, src, &clen,
323					zram->compress_workmem);
324
325		kunmap_atomic(user_mem, KM_USER0);
326
327		if (unlikely(ret != LZO_E_OK)) {
328			mutex_unlock(&zram->lock);
329			pr_err("Compression failed! err=%d\n", ret);
330			zram_stat64_inc(zram, &zram->stats.failed_writes);
331			goto out;
332		}
333
334		/*
335		 * Page is incompressible. Store it as-is (uncompressed)
336		 * since we do not want to return too many disk write
337		 * errors which has side effect of hanging the system.
338		 */
339		if (unlikely(clen > max_zpage_size)) {
340			clen = PAGE_SIZE;
341			page_store = alloc_page(GFP_NOIO | __GFP_HIGHMEM);
342			if (unlikely(!page_store)) {
343				mutex_unlock(&zram->lock);
344				pr_info("Error allocating memory for "
345					"incompressible page: %u\n", index);
346				zram_stat64_inc(zram,
347					&zram->stats.failed_writes);
348				goto out;
349			}
350
351			offset = 0;
352			zram_set_flag(zram, index, ZRAM_UNCOMPRESSED);
353			zram_stat_inc(&zram->stats.pages_expand);
354			zram->table[index].page = page_store;
355			src = kmap_atomic(page, KM_USER0);
356			goto memstore;
357		}
358
359		if (xv_malloc(zram->mem_pool, clen + sizeof(*zheader),
360				&zram->table[index].page, &offset,
361				GFP_NOIO | __GFP_HIGHMEM)) {
362			mutex_unlock(&zram->lock);
363			pr_info("Error allocating memory for compressed "
364				"page: %u, size=%zu\n", index, clen);
365			zram_stat64_inc(zram, &zram->stats.failed_writes);
366			goto out;
367		}
368
369memstore:
370		zram->table[index].offset = offset;
371
372		cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
373				zram->table[index].offset;
374
375#if 0
376		/* Back-reference needed for memory defragmentation */
377		if (!zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)) {
378			zheader = (struct zobj_header *)cmem;
379			zheader->table_idx = index;
380			cmem += sizeof(*zheader);
381		}
382#endif
383
384		memcpy(cmem, src, clen);
385
386		kunmap_atomic(cmem, KM_USER1);
387		if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)))
388			kunmap_atomic(src, KM_USER0);
389
390		/* Update stats */
391		zram_stat64_add(zram, &zram->stats.compr_size, clen);
392		zram_stat_inc(&zram->stats.pages_stored);
393		if (clen <= PAGE_SIZE / 2)
394			zram_stat_inc(&zram->stats.good_compress);
395
396		mutex_unlock(&zram->lock);
397		index++;
398	}
399
400	set_bit(BIO_UPTODATE, &bio->bi_flags);
401	bio_endio(bio, 0);
402	return;
403
404out:
405	bio_io_error(bio);
406}
407
408/*
409 * Check if request is within bounds and page aligned.
410 */
411static inline int valid_io_request(struct zram *zram, struct bio *bio)
412{
413	if (unlikely(
414		(bio->bi_sector >= (zram->disksize >> SECTOR_SHIFT)) ||
415		(bio->bi_sector & (SECTORS_PER_PAGE - 1)) ||
416		(bio->bi_size & (PAGE_SIZE - 1)))) {
417
418		return 0;
419	}
420
421	/* I/O request is valid */
422	return 1;
423}
424
425/*
426 * Handler function for all zram I/O requests.
427 */
428static int zram_make_request(struct request_queue *queue, struct bio *bio)
429{
430	struct zram *zram = queue->queuedata;
431
432	if (!valid_io_request(zram, bio)) {
433		zram_stat64_inc(zram, &zram->stats.invalid_io);
434		bio_io_error(bio);
435		return 0;
436	}
437
438	if (unlikely(!zram->init_done) && zram_init_device(zram)) {
439		bio_io_error(bio);
440		return 0;
441	}
442
443	switch (bio_data_dir(bio)) {
444	case READ:
445		zram_read(zram, bio);
446		break;
447
448	case WRITE:
449		zram_write(zram, bio);
450		break;
451	}
452
453	return 0;
454}
455
456void zram_reset_device(struct zram *zram)
457{
458	size_t index;
459
460	mutex_lock(&zram->init_lock);
461	zram->init_done = 0;
462
463	/* Free various per-device buffers */
464	kfree(zram->compress_workmem);
465	free_pages((unsigned long)zram->compress_buffer, 1);
466
467	zram->compress_workmem = NULL;
468	zram->compress_buffer = NULL;
469
470	/* Free all pages that are still in this zram device */
471	for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) {
472		struct page *page;
473		u16 offset;
474
475		page = zram->table[index].page;
476		offset = zram->table[index].offset;
477
478		if (!page)
479			continue;
480
481		if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)))
482			__free_page(page);
483		else
484			xv_free(zram->mem_pool, page, offset);
485	}
486
487	vfree(zram->table);
488	zram->table = NULL;
489
490	xv_destroy_pool(zram->mem_pool);
491	zram->mem_pool = NULL;
492
493	/* Reset stats */
494	memset(&zram->stats, 0, sizeof(zram->stats));
495
496	zram->disksize = 0;
497	mutex_unlock(&zram->init_lock);
498}
499
500int zram_init_device(struct zram *zram)
501{
502	int ret;
503	size_t num_pages;
504
505	mutex_lock(&zram->init_lock);
506
507	if (zram->init_done) {
508		mutex_unlock(&zram->init_lock);
509		return 0;
510	}
511
512	zram_set_disksize(zram, totalram_pages << PAGE_SHIFT);
513
514	zram->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
515	if (!zram->compress_workmem) {
516		pr_err("Error allocating compressor working memory!\n");
517		ret = -ENOMEM;
518		goto fail;
519	}
520
521	zram->compress_buffer = (void *)__get_free_pages(__GFP_ZERO, 1);
522	if (!zram->compress_buffer) {
523		pr_err("Error allocating compressor buffer space\n");
524		ret = -ENOMEM;
525		goto fail;
526	}
527
528	num_pages = zram->disksize >> PAGE_SHIFT;
529	zram->table = vzalloc(num_pages * sizeof(*zram->table));
530	if (!zram->table) {
531		pr_err("Error allocating zram address table\n");
532		/* To prevent accessing table entries during cleanup */
533		zram->disksize = 0;
534		ret = -ENOMEM;
535		goto fail;
536	}
537
538	set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
539
540	/* zram devices sort of resembles non-rotational disks */
541	queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
542
543	zram->mem_pool = xv_create_pool();
544	if (!zram->mem_pool) {
545		pr_err("Error creating memory pool\n");
546		ret = -ENOMEM;
547		goto fail;
548	}
549
550	zram->init_done = 1;
551	mutex_unlock(&zram->init_lock);
552
553	pr_debug("Initialization done!\n");
554	return 0;
555
556fail:
557	mutex_unlock(&zram->init_lock);
558	zram_reset_device(zram);
559
560	pr_err("Initialization failed: err=%d\n", ret);
561	return ret;
562}
563
564void zram_slot_free_notify(struct block_device *bdev, unsigned long index)
565{
566	struct zram *zram;
567
568	zram = bdev->bd_disk->private_data;
569	zram_free_page(zram, index);
570	zram_stat64_inc(zram, &zram->stats.notify_free);
571}
572
573static const struct block_device_operations zram_devops = {
574	.swap_slot_free_notify = zram_slot_free_notify,
575	.owner = THIS_MODULE
576};
577
578static int create_device(struct zram *zram, int device_id)
579{
580	int ret = 0;
581
582	mutex_init(&zram->lock);
583	mutex_init(&zram->init_lock);
584	spin_lock_init(&zram->stat64_lock);
585
586	zram->queue = blk_alloc_queue(GFP_KERNEL);
587	if (!zram->queue) {
588		pr_err("Error allocating disk queue for device %d\n",
589			device_id);
590		ret = -ENOMEM;
591		goto out;
592	}
593
594	blk_queue_make_request(zram->queue, zram_make_request);
595	zram->queue->queuedata = zram;
596
597	 /* gendisk structure */
598	zram->disk = alloc_disk(1);
599	if (!zram->disk) {
600		blk_cleanup_queue(zram->queue);
601		pr_warning("Error allocating disk structure for device %d\n",
602			device_id);
603		ret = -ENOMEM;
604		goto out;
605	}
606
607	zram->disk->major = zram_major;
608	zram->disk->first_minor = device_id;
609	zram->disk->fops = &zram_devops;
610	zram->disk->queue = zram->queue;
611	zram->disk->private_data = zram;
612	snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
613
614	/* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
615	set_capacity(zram->disk, 0);
616
617	/*
618	 * To ensure that we always get PAGE_SIZE aligned
619	 * and n*PAGE_SIZED sized I/O requests.
620	 */
621	blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
622	blk_queue_logical_block_size(zram->disk->queue,
623					ZRAM_LOGICAL_BLOCK_SIZE);
624	blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
625	blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
626
627	add_disk(zram->disk);
628
629	ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
630				&zram_disk_attr_group);
631	if (ret < 0) {
632		pr_warning("Error creating sysfs group");
633		goto out;
634	}
635
636	zram->init_done = 0;
637
638out:
639	return ret;
640}
641
642static void destroy_device(struct zram *zram)
643{
644	sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
645			&zram_disk_attr_group);
646
647	if (zram->disk) {
648		del_gendisk(zram->disk);
649		put_disk(zram->disk);
650	}
651
652	if (zram->queue)
653		blk_cleanup_queue(zram->queue);
654}
655
656static int __init zram_init(void)
657{
658	int ret, dev_id;
659
660	if (num_devices > max_num_devices) {
661		pr_warning("Invalid value for num_devices: %u\n",
662				num_devices);
663		ret = -EINVAL;
664		goto out;
665	}
666
667	zram_major = register_blkdev(0, "zram");
668	if (zram_major <= 0) {
669		pr_warning("Unable to get major number\n");
670		ret = -EBUSY;
671		goto out;
672	}
673
674	if (!num_devices) {
675		pr_info("num_devices not specified. Using default: 1\n");
676		num_devices = 1;
677	}
678
679	/* Allocate the device array and initialize each one */
680	pr_info("Creating %u devices ...\n", num_devices);
681	devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
682	if (!devices) {
683		ret = -ENOMEM;
684		goto unregister;
685	}
686
687	for (dev_id = 0; dev_id < num_devices; dev_id++) {
688		ret = create_device(&devices[dev_id], dev_id);
689		if (ret)
690			goto free_devices;
691	}
692
693	return 0;
694
695free_devices:
696	while (dev_id)
697		destroy_device(&devices[--dev_id]);
698	kfree(devices);
699unregister:
700	unregister_blkdev(zram_major, "zram");
701out:
702	return ret;
703}
704
705static void __exit zram_exit(void)
706{
707	int i;
708	struct zram *zram;
709
710	for (i = 0; i < num_devices; i++) {
711		zram = &devices[i];
712
713		destroy_device(zram);
714		if (zram->init_done)
715			zram_reset_device(zram);
716	}
717
718	unregister_blkdev(zram_major, "zram");
719
720	kfree(devices);
721	pr_debug("Cleanup done!\n");
722}
723
724module_param(num_devices, uint, 0);
725MODULE_PARM_DESC(num_devices, "Number of zram devices");
726
727module_init(zram_init);
728module_exit(zram_exit);
729
730MODULE_LICENSE("Dual BSD/GPL");
731MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
732MODULE_DESCRIPTION("Compressed RAM Block Device");