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|
/*
* Compressed RAM block device
*
* Copyright (C) 2008, 2009, 2010 Nitin Gupta
*
* This code is released using a dual license strategy: BSD/GPL
* You can choose the licence that better fits your requirements.
*
* Released under the terms of 3-clause BSD License
* Released under the terms of GNU General Public License Version 2.0
*
* Project home: http://compcache.googlecode.com
*/
#define KMSG_COMPONENT "zram"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/bio.h>
#include <linux/bitops.h>
#include <linux/blkdev.h>
#include <linux/buffer_head.h>
#include <linux/device.h>
#include <linux/genhd.h>
#include <linux/highmem.h>
#include <linux/slab.h>
#include <linux/lzo.h>
#include <linux/string.h>
#include <linux/vmalloc.h>
#include "zram_drv.h"
/* Globals */
static int zram_major;
struct zram *devices;
/* Module params (documentation at end) */
unsigned int num_devices;
static void zram_stat_inc(u32 *v)
{
*v = *v + 1;
}
static void zram_stat_dec(u32 *v)
{
*v = *v - 1;
}
static void zram_stat64_add(struct zram *zram, u64 *v, u64 inc)
{
spin_lock(&zram->stat64_lock);
*v = *v + inc;
spin_unlock(&zram->stat64_lock);
}
static void zram_stat64_sub(struct zram *zram, u64 *v, u64 dec)
{
spin_lock(&zram->stat64_lock);
*v = *v - dec;
spin_unlock(&zram->stat64_lock);
}
static void zram_stat64_inc(struct zram *zram, u64 *v)
{
zram_stat64_add(zram, v, 1);
}
static int zram_test_flag(struct zram *zram, u32 index,
enum zram_pageflags flag)
{
return zram->table[index].flags & BIT(flag);
}
static void zram_set_flag(struct zram *zram, u32 index,
enum zram_pageflags flag)
{
zram->table[index].flags |= BIT(flag);
}
static void zram_clear_flag(struct zram *zram, u32 index,
enum zram_pageflags flag)
{
zram->table[index].flags &= ~BIT(flag);
}
static int page_zero_filled(void *ptr)
{
unsigned int pos;
unsigned long *page;
page = (unsigned long *)ptr;
for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) {
if (page[pos])
return 0;
}
return 1;
}
static void zram_set_disksize(struct zram *zram, size_t totalram_bytes)
{
if (!zram->disksize) {
pr_info(
"disk size not provided. You can use disksize_kb module "
"param to specify size.\nUsing default: (%u%% of RAM).\n",
default_disksize_perc_ram
);
zram->disksize = default_disksize_perc_ram *
(totalram_bytes / 100);
}
if (zram->disksize > 2 * (totalram_bytes)) {
pr_info(
"There is little point creating a zram of greater than "
"twice the size of memory since we expect a 2:1 compression "
"ratio. Note that zram uses about 0.1%% of the size of "
"the disk when not in use so a huge zram is "
"wasteful.\n"
"\tMemory Size: %zu kB\n"
"\tSize you selected: %llu kB\n"
"Continuing anyway ...\n",
totalram_bytes >> 10, zram->disksize
);
}
zram->disksize &= PAGE_MASK;
}
static void zram_free_page(struct zram *zram, size_t index)
{
u32 clen;
void *obj;
struct page *page = zram->table[index].page;
u32 offset = zram->table[index].offset;
if (unlikely(!page)) {
/*
* No memory is allocated for zero filled pages.
* Simply clear zero page flag.
*/
if (zram_test_flag(zram, index, ZRAM_ZERO)) {
zram_clear_flag(zram, index, ZRAM_ZERO);
zram_stat_dec(&zram->stats.pages_zero);
}
return;
}
if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
clen = PAGE_SIZE;
__free_page(page);
zram_clear_flag(zram, index, ZRAM_UNCOMPRESSED);
zram_stat_dec(&zram->stats.pages_expand);
goto out;
}
obj = kmap_atomic(page, KM_USER0) + offset;
clen = xv_get_object_size(obj) - sizeof(struct zobj_header);
kunmap_atomic(obj, KM_USER0);
xv_free(zram->mem_pool, page, offset);
if (clen <= PAGE_SIZE / 2)
zram_stat_dec(&zram->stats.good_compress);
out:
zram_stat64_sub(zram, &zram->stats.compr_size, clen);
zram_stat_dec(&zram->stats.pages_stored);
zram->table[index].page = NULL;
zram->table[index].offset = 0;
}
static void handle_zero_page(struct page *page)
{
void *user_mem;
user_mem = kmap_atomic(page, KM_USER0);
memset(user_mem, 0, PAGE_SIZE);
kunmap_atomic(user_mem, KM_USER0);
flush_dcache_page(page);
}
static void handle_uncompressed_page(struct zram *zram,
struct page *page, u32 index)
{
unsigned char *user_mem, *cmem;
user_mem = kmap_atomic(page, KM_USER0);
cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
zram->table[index].offset;
memcpy(user_mem, cmem, PAGE_SIZE);
kunmap_atomic(user_mem, KM_USER0);
kunmap_atomic(cmem, KM_USER1);
flush_dcache_page(page);
}
static void zram_read(struct zram *zram, struct bio *bio)
{
int i;
u32 index;
struct bio_vec *bvec;
if (unlikely(!zram->init_done)) {
bio_endio(bio, -ENXIO);
return;
}
zram_stat64_inc(zram, &zram->stats.num_reads);
index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
bio_for_each_segment(bvec, bio, i) {
int ret;
size_t clen;
struct page *page;
struct zobj_header *zheader;
unsigned char *user_mem, *cmem;
page = bvec->bv_page;
if (zram_test_flag(zram, index, ZRAM_ZERO)) {
handle_zero_page(page);
continue;
}
/* Requested page is not present in compressed area */
if (unlikely(!zram->table[index].page)) {
pr_debug("Read before write: sector=%lu, size=%u",
(ulong)(bio->bi_sector), bio->bi_size);
/* Do nothing */
continue;
}
/* Page is stored uncompressed since it's incompressible */
if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
handle_uncompressed_page(zram, page, index);
continue;
}
user_mem = kmap_atomic(page, KM_USER0);
clen = PAGE_SIZE;
cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
zram->table[index].offset;
ret = lzo1x_decompress_safe(
cmem + sizeof(*zheader),
xv_get_object_size(cmem) - sizeof(*zheader),
user_mem, &clen);
kunmap_atomic(user_mem, KM_USER0);
kunmap_atomic(cmem, KM_USER1);
/* Should NEVER happen. Return bio error if it does. */
if (unlikely(ret != LZO_E_OK)) {
pr_err("Decompression failed! err=%d, page=%u\n",
ret, index);
zram_stat64_inc(zram, &zram->stats.failed_reads);
goto out;
}
flush_dcache_page(page);
index++;
}
set_bit(BIO_UPTODATE, &bio->bi_flags);
bio_endio(bio, 0);
return;
out:
bio_io_error(bio);
}
static void zram_write(struct zram *zram, struct bio *bio)
{
int i, ret;
u32 index;
struct bio_vec *bvec;
if (unlikely(!zram->init_done)) {
ret = zram_init_device(zram);
if (ret)
goto out;
}
zram_stat64_inc(zram, &zram->stats.num_writes);
index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
bio_for_each_segment(bvec, bio, i) {
u32 offset;
size_t clen;
struct zobj_header *zheader;
struct page *page, *page_store;
unsigned char *user_mem, *cmem, *src;
page = bvec->bv_page;
src = zram->compress_buffer;
/*
* System overwrites unused sectors. Free memory associated
* with this sector now.
*/
if (zram->table[index].page ||
zram_test_flag(zram, index, ZRAM_ZERO))
zram_free_page(zram, index);
mutex_lock(&zram->lock);
user_mem = kmap_atomic(page, KM_USER0);
if (page_zero_filled(user_mem)) {
kunmap_atomic(user_mem, KM_USER0);
mutex_unlock(&zram->lock);
zram_stat_inc(&zram->stats.pages_zero);
zram_set_flag(zram, index, ZRAM_ZERO);
continue;
}
ret = lzo1x_1_compress(user_mem, PAGE_SIZE, src, &clen,
zram->compress_workmem);
kunmap_atomic(user_mem, KM_USER0);
if (unlikely(ret != LZO_E_OK)) {
mutex_unlock(&zram->lock);
pr_err("Compression failed! err=%d\n", ret);
zram_stat64_inc(zram, &zram->stats.failed_writes);
goto out;
}
/*
* Page is incompressible. Store it as-is (uncompressed)
* since we do not want to return too many disk write
* errors which has side effect of hanging the system.
*/
if (unlikely(clen > max_zpage_size)) {
clen = PAGE_SIZE;
page_store = alloc_page(GFP_NOIO | __GFP_HIGHMEM);
if (unlikely(!page_store)) {
mutex_unlock(&zram->lock);
pr_info("Error allocating memory for "
"incompressible page: %u\n", index);
zram_stat64_inc(zram,
&zram->stats.failed_writes);
goto out;
}
offset = 0;
zram_set_flag(zram, index, ZRAM_UNCOMPRESSED);
zram_stat_inc(&zram->stats.pages_expand);
zram->table[index].page = page_store;
src = kmap_atomic(page, KM_USER0);
goto memstore;
}
if (xv_malloc(zram->mem_pool, clen + sizeof(*zheader),
&zram->table[index].page, &offset,
GFP_NOIO | __GFP_HIGHMEM)) {
mutex_unlock(&zram->lock);
pr_info("Error allocating memory for compressed "
"page: %u, size=%zu\n", index, clen);
zram_stat64_inc(zram, &zram->stats.failed_writes);
goto out;
}
memstore:
zram->table[index].offset = offset;
cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
zram->table[index].offset;
#if 0
/* Back-reference needed for memory defragmentation */
if (!zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)) {
zheader = (struct zobj_header *)cmem;
zheader->table_idx = index;
cmem += sizeof(*zheader);
}
#endif
memcpy(cmem, src, clen);
kunmap_atomic(cmem, KM_USER1);
if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)))
kunmap_atomic(src, KM_USER0);
/* Update stats */
zram_stat64_add(zram, &zram->stats.compr_size, clen);
zram_stat_inc(&zram->stats.pages_stored);
if (clen <= PAGE_SIZE / 2)
zram_stat_inc(&zram->stats.good_compress);
mutex_unlock(&zram->lock);
index++;
}
set_bit(BIO_UPTODATE, &bio->bi_flags);
bio_endio(bio, 0);
return;
out:
bio_io_error(bio);
}
/*
* Check if request is within bounds and page aligned.
*/
static inline int valid_io_request(struct zram *zram, struct bio *bio)
{
if (unlikely(
(bio->bi_sector >= (zram->disksize >> SECTOR_SHIFT)) ||
(bio->bi_sector & (SECTORS_PER_PAGE - 1)) ||
(bio->bi_size & (PAGE_SIZE - 1)))) {
return 0;
}
/* I/O request is valid */
return 1;
}
/*
* Handler function for all zram I/O requests.
*/
static int zram_make_request(struct request_queue *queue, struct bio *bio)
{
struct zram *zram = queue->queuedata;
if (!valid_io_request(zram, bio)) {
zram_stat64_inc(zram, &zram->stats.invalid_io);
bio_io_error(bio);
return 0;
}
switch (bio_data_dir(bio)) {
case READ:
zram_read(zram, bio);
break;
case WRITE:
zram_write(zram, bio);
break;
}
return 0;
}
void zram_reset_device(struct zram *zram)
{
size_t index;
mutex_lock(&zram->init_lock);
zram->init_done = 0;
/* Free various per-device buffers */
kfree(zram->compress_workmem);
free_pages((unsigned long)zram->compress_buffer, 1);
zram->compress_workmem = NULL;
zram->compress_buffer = NULL;
/* Free all pages that are still in this zram device */
for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) {
struct page *page;
u16 offset;
page = zram->table[index].page;
offset = zram->table[index].offset;
if (!page)
continue;
if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)))
__free_page(page);
else
xv_free(zram->mem_pool, page, offset);
}
vfree(zram->table);
zram->table = NULL;
xv_destroy_pool(zram->mem_pool);
zram->mem_pool = NULL;
/* Reset stats */
memset(&zram->stats, 0, sizeof(zram->stats));
zram->disksize = 0;
mutex_unlock(&zram->init_lock);
}
int zram_init_device(struct zram *zram)
{
int ret;
size_t num_pages;
mutex_lock(&zram->init_lock);
if (zram->init_done) {
mutex_unlock(&zram->init_lock);
return 0;
}
zram_set_disksize(zram, totalram_pages << PAGE_SHIFT);
zram->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
if (!zram->compress_workmem) {
pr_err("Error allocating compressor working memory!\n");
ret = -ENOMEM;
goto fail;
}
zram->compress_buffer = (void *)__get_free_pages(__GFP_ZERO, 1);
if (!zram->compress_buffer) {
pr_err("Error allocating compressor buffer space\n");
ret = -ENOMEM;
goto fail;
}
num_pages = zram->disksize >> PAGE_SHIFT;
zram->table = vzalloc(num_pages * sizeof(*zram->table));
if (!zram->table) {
pr_err("Error allocating zram address table\n");
/* To prevent accessing table entries during cleanup */
zram->disksize = 0;
ret = -ENOMEM;
goto fail;
}
set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
/* zram devices sort of resembles non-rotational disks */
queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
zram->mem_pool = xv_create_pool();
if (!zram->mem_pool) {
pr_err("Error creating memory pool\n");
ret = -ENOMEM;
goto fail;
}
zram->init_done = 1;
mutex_unlock(&zram->init_lock);
pr_debug("Initialization done!\n");
return 0;
fail:
mutex_unlock(&zram->init_lock);
zram_reset_device(zram);
pr_err("Initialization failed: err=%d\n", ret);
return ret;
}
void zram_slot_free_notify(struct block_device *bdev, unsigned long index)
{
struct zram *zram;
zram = bdev->bd_disk->private_data;
zram_free_page(zram, index);
zram_stat64_inc(zram, &zram->stats.notify_free);
}
static const struct block_device_operations zram_devops = {
.swap_slot_free_notify = zram_slot_free_notify,
.owner = THIS_MODULE
};
static int create_device(struct zram *zram, int device_id)
{
int ret = 0;
mutex_init(&zram->lock);
mutex_init(&zram->init_lock);
spin_lock_init(&zram->stat64_lock);
zram->queue = blk_alloc_queue(GFP_KERNEL);
if (!zram->queue) {
pr_err("Error allocating disk queue for device %d\n",
device_id);
ret = -ENOMEM;
goto out;
}
blk_queue_make_request(zram->queue, zram_make_request);
zram->queue->queuedata = zram;
/* gendisk structure */
zram->disk = alloc_disk(1);
if (!zram->disk) {
blk_cleanup_queue(zram->queue);
pr_warning("Error allocating disk structure for device %d\n",
device_id);
ret = -ENOMEM;
goto out;
}
zram->disk->major = zram_major;
zram->disk->first_minor = device_id;
zram->disk->fops = &zram_devops;
zram->disk->queue = zram->queue;
zram->disk->private_data = zram;
snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
/* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
set_capacity(zram->disk, 0);
/*
* To ensure that we always get PAGE_SIZE aligned
* and n*PAGE_SIZED sized I/O requests.
*/
blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
blk_queue_logical_block_size(zram->disk->queue, PAGE_SIZE);
blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
add_disk(zram->disk);
ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
&zram_disk_attr_group);
if (ret < 0) {
pr_warning("Error creating sysfs group");
goto out;
}
zram->init_done = 0;
out:
return ret;
}
static void destroy_device(struct zram *zram)
{
sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
&zram_disk_attr_group);
if (zram->disk) {
del_gendisk(zram->disk);
put_disk(zram->disk);
}
if (zram->queue)
blk_cleanup_queue(zram->queue);
}
static int __init zram_init(void)
{
int ret, dev_id;
if (num_devices > max_num_devices) {
pr_warning("Invalid value for num_devices: %u\n",
num_devices);
ret = -EINVAL;
goto out;
}
zram_major = register_blkdev(0, "zram");
if (zram_major <= 0) {
pr_warning("Unable to get major number\n");
ret = -EBUSY;
goto out;
}
if (!num_devices) {
pr_info("num_devices not specified. Using default: 1\n");
num_devices = 1;
}
/* Allocate the device array and initialize each one */
pr_info("Creating %u devices ...\n", num_devices);
devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
if (!devices) {
ret = -ENOMEM;
goto unregister;
}
for (dev_id = 0; dev_id < num_devices; dev_id++) {
ret = create_device(&devices[dev_id], dev_id);
if (ret)
goto free_devices;
}
return 0;
free_devices:
while (dev_id)
destroy_device(&devices[--dev_id]);
kfree(devices);
unregister:
unregister_blkdev(zram_major, "zram");
out:
return ret;
}
static void __exit zram_exit(void)
{
int i;
struct zram *zram;
for (i = 0; i < num_devices; i++) {
zram = &devices[i];
destroy_device(zram);
if (zram->init_done)
zram_reset_device(zram);
}
unregister_blkdev(zram_major, "zram");
kfree(devices);
pr_debug("Cleanup done!\n");
}
module_param(num_devices, uint, 0);
MODULE_PARM_DESC(num_devices, "Number of zram devices");
module_init(zram_init);
module_exit(zram_exit);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
MODULE_DESCRIPTION("Compressed RAM Block Device");
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