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* Compressed RAM based swap 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 "ramzswap"
#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
#include <linux/module.h>
#include <linux/kernel.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/swap.h>
#include <linux/swapops.h>
#include <linux/vmalloc.h>
#include "ramzswap_drv.h"
/* Globals */
static int ramzswap_major;
static struct ramzswap *devices;
/* Module params (documentation at end) */
static unsigned int num_devices;
static int rzs_test_flag(struct ramzswap *rzs, u32 index,
enum rzs_pageflags flag)
{
return rzs->table[index].flags & BIT(flag);
}
static void rzs_set_flag(struct ramzswap *rzs, u32 index,
enum rzs_pageflags flag)
{
rzs->table[index].flags |= BIT(flag);
}
static void rzs_clear_flag(struct ramzswap *rzs, u32 index,
enum rzs_pageflags flag)
{
rzs->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 ramzswap_set_disksize(struct ramzswap *rzs, size_t totalram_bytes)
{
if (!rzs->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
);
rzs->disksize = default_disksize_perc_ram *
(totalram_bytes / 100);
}
if (rzs->disksize > 2 * (totalram_bytes)) {
pr_info(
"There is little point creating a ramzswap of greater than "
"twice the size of memory since we expect a 2:1 compression "
"ratio. Note that ramzswap uses about 0.1%% of the size of "
"the swap device when not in use so a huge ramzswap is "
"wasteful.\n"
"\tMemory Size: %zu kB\n"
"\tSize you selected: %zu kB\n"
"Continuing anyway ...\n",
totalram_bytes >> 10, rzs->disksize
);
}
rzs->disksize &= PAGE_MASK;
}
/*
* Swap header (1st page of swap device) contains information
* about a swap file/partition. Prepare such a header for the
* given ramzswap device so that swapon can identify it as a
* swap partition.
*/
static void setup_swap_header(struct ramzswap *rzs, union swap_header *s)
{
s->info.version = 1;
s->info.last_page = (rzs->disksize >> PAGE_SHIFT) - 1;
s->info.nr_badpages = 0;
memcpy(s->magic.magic, "SWAPSPACE2", 10);
}
static void ramzswap_ioctl_get_stats(struct ramzswap *rzs,
struct ramzswap_ioctl_stats *s)
{
s->disksize = rzs->disksize;
#if defined(CONFIG_RAMZSWAP_STATS)
{
struct ramzswap_stats *rs = &rzs->stats;
size_t succ_writes, mem_used;
unsigned int good_compress_perc = 0, no_compress_perc = 0;
mem_used = xv_get_total_size_bytes(rzs->mem_pool)
+ (rs->pages_expand << PAGE_SHIFT);
succ_writes = rzs_stat64_read(rzs, &rs->num_writes) -
rzs_stat64_read(rzs, &rs->failed_writes);
if (succ_writes && rs->pages_stored) {
good_compress_perc = rs->good_compress * 100
/ rs->pages_stored;
no_compress_perc = rs->pages_expand * 100
/ rs->pages_stored;
}
s->num_reads = rzs_stat64_read(rzs, &rs->num_reads);
s->num_writes = rzs_stat64_read(rzs, &rs->num_writes);
s->failed_reads = rzs_stat64_read(rzs, &rs->failed_reads);
s->failed_writes = rzs_stat64_read(rzs, &rs->failed_writes);
s->invalid_io = rzs_stat64_read(rzs, &rs->invalid_io);
s->notify_free = rzs_stat64_read(rzs, &rs->notify_free);
s->pages_zero = rs->pages_zero;
s->good_compress_pct = good_compress_perc;
s->pages_expand_pct = no_compress_perc;
s->pages_stored = rs->pages_stored;
s->pages_used = mem_used >> PAGE_SHIFT;
s->orig_data_size = rs->pages_stored << PAGE_SHIFT;
s->compr_data_size = rs->compr_size;
s->mem_used_total = mem_used;
}
#endif /* CONFIG_RAMZSWAP_STATS */
}
static void ramzswap_free_page(struct ramzswap *rzs, size_t index)
{
u32 clen;
void *obj;
struct page *page = rzs->table[index].page;
u32 offset = rzs->table[index].offset;
if (unlikely(!page)) {
/*
* No memory is allocated for zero filled pages.
* Simply clear zero page flag.
*/
if (rzs_test_flag(rzs, index, RZS_ZERO)) {
rzs_clear_flag(rzs, index, RZS_ZERO);
rzs_stat_dec(&rzs->stats.pages_zero);
}
return;
}
if (unlikely(rzs_test_flag(rzs, index, RZS_UNCOMPRESSED))) {
clen = PAGE_SIZE;
__free_page(page);
rzs_clear_flag(rzs, index, RZS_UNCOMPRESSED);
rzs_stat_dec(&rzs->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(rzs->mem_pool, page, offset);
if (clen <= PAGE_SIZE / 2)
rzs_stat_dec(&rzs->stats.good_compress);
out:
rzs->stats.compr_size -= clen;
rzs_stat_dec(&rzs->stats.pages_stored);
rzs->table[index].page = NULL;
rzs->table[index].offset = 0;
}
static int handle_zero_page(struct bio *bio)
{
void *user_mem;
struct page *page = bio->bi_io_vec[0].bv_page;
user_mem = kmap_atomic(page, KM_USER0);
memset(user_mem, 0, PAGE_SIZE);
kunmap_atomic(user_mem, KM_USER0);
flush_dcache_page(page);
set_bit(BIO_UPTODATE, &bio->bi_flags);
bio_endio(bio, 0);
return 0;
}
static int handle_uncompressed_page(struct ramzswap *rzs, struct bio *bio)
{
u32 index;
struct page *page;
unsigned char *user_mem, *cmem;
page = bio->bi_io_vec[0].bv_page;
index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
user_mem = kmap_atomic(page, KM_USER0);
cmem = kmap_atomic(rzs->table[index].page, KM_USER1) +
rzs->table[index].offset;
memcpy(user_mem, cmem, PAGE_SIZE);
kunmap_atomic(user_mem, KM_USER0);
kunmap_atomic(cmem, KM_USER1);
flush_dcache_page(page);
set_bit(BIO_UPTODATE, &bio->bi_flags);
bio_endio(bio, 0);
return 0;
}
/*
* Called when request page is not present in ramzswap.
* This is an attempt to read before any previous write
* to this location - this happens due to readahead when
* swap device is read from user-space (e.g. during swapon)
*/
static int handle_ramzswap_fault(struct ramzswap *rzs, struct bio *bio)
{
pr_debug("Read before write on swap device: "
"sector=%lu, size=%u, offset=%u\n",
(ulong)(bio->bi_sector), bio->bi_size,
bio->bi_io_vec[0].bv_offset);
/* Do nothing. Just return success */
set_bit(BIO_UPTODATE, &bio->bi_flags);
bio_endio(bio, 0);
return 0;
}
static int ramzswap_read(struct ramzswap *rzs, struct bio *bio)
{
int ret;
u32 index;
size_t clen;
struct page *page;
struct zobj_header *zheader;
unsigned char *user_mem, *cmem;
rzs_stat64_inc(rzs, &rzs->stats.num_reads);
page = bio->bi_io_vec[0].bv_page;
index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
if (rzs_test_flag(rzs, index, RZS_ZERO))
return handle_zero_page(bio);
/* Requested page is not present in compressed area */
if (!rzs->table[index].page)
return handle_ramzswap_fault(rzs, bio);
/* Page is stored uncompressed since it's incompressible */
if (unlikely(rzs_test_flag(rzs, index, RZS_UNCOMPRESSED)))
return handle_uncompressed_page(rzs, bio);
user_mem = kmap_atomic(page, KM_USER0);
clen = PAGE_SIZE;
cmem = kmap_atomic(rzs->table[index].page, KM_USER1) +
rzs->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 */
if (unlikely(ret != LZO_E_OK)) {
pr_err("Decompression failed! err=%d, page=%u\n",
ret, index);
rzs_stat64_inc(rzs, &rzs->stats.failed_reads);
goto out;
}
flush_dcache_page(page);
set_bit(BIO_UPTODATE, &bio->bi_flags);
bio_endio(bio, 0);
return 0;
out:
bio_io_error(bio);
return 0;
}
static int ramzswap_write(struct ramzswap *rzs, struct bio *bio)
{
int ret;
u32 offset, index;
size_t clen;
struct zobj_header *zheader;
struct page *page, *page_store;
unsigned char *user_mem, *cmem, *src;
rzs_stat64_inc(rzs, &rzs->stats.num_writes);
page = bio->bi_io_vec[0].bv_page;
index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
src = rzs->compress_buffer;
mutex_lock(&rzs->lock);
user_mem = kmap_atomic(page, KM_USER0);
if (page_zero_filled(user_mem)) {
kunmap_atomic(user_mem, KM_USER0);
mutex_unlock(&rzs->lock);
rzs_stat_inc(&rzs->stats.pages_zero);
rzs_set_flag(rzs, index, RZS_ZERO);
set_bit(BIO_UPTODATE, &bio->bi_flags);
bio_endio(bio, 0);
return 0;
}
ret = lzo1x_1_compress(user_mem, PAGE_SIZE, src, &clen,
rzs->compress_workmem);
kunmap_atomic(user_mem, KM_USER0);
if (unlikely(ret != LZO_E_OK)) {
mutex_unlock(&rzs->lock);
pr_err("Compression failed! err=%d\n", ret);
rzs_stat64_inc(rzs, &rzs->stats.failed_writes);
goto out;
}
/*
* Page is incompressible. Store it as-is (uncompressed)
* since we do not want to return too many swap 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(&rzs->lock);
pr_info("Error allocating memory for incompressible "
"page: %u\n", index);
rzs_stat64_inc(rzs, &rzs->stats.failed_writes);
goto out;
}
offset = 0;
rzs_set_flag(rzs, index, RZS_UNCOMPRESSED);
rzs_stat_inc(&rzs->stats.pages_expand);
rzs->table[index].page = page_store;
src = kmap_atomic(page, KM_USER0);
goto memstore;
}
if (xv_malloc(rzs->mem_pool, clen + sizeof(*zheader),
&rzs->table[index].page, &offset,
GFP_NOIO | __GFP_HIGHMEM)) {
mutex_unlock(&rzs->lock);
pr_info("Error allocating memory for compressed "
"page: %u, size=%zu\n", index, clen);
rzs_stat64_inc(rzs, &rzs->stats.failed_writes);
goto out;
}
memstore:
rzs->table[index].offset = offset;
cmem = kmap_atomic(rzs->table[index].page, KM_USER1) +
rzs->table[index].offset;
#if 0
/* Back-reference needed for memory defragmentation */
if (!rzs_test_flag(rzs, index, RZS_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(rzs_test_flag(rzs, index, RZS_UNCOMPRESSED)))
kunmap_atomic(src, KM_USER0);
/* Update stats */
rzs->stats.compr_size += clen;
rzs_stat_inc(&rzs->stats.pages_stored);
if (clen <= PAGE_SIZE / 2)
rzs_stat_inc(&rzs->stats.good_compress);
mutex_unlock(&rzs->lock);
set_bit(BIO_UPTODATE, &bio->bi_flags);
bio_endio(bio, 0);
return 0;
out:
bio_io_error(bio);
return 0;
}
/*
* Check if request is within bounds and page aligned.
*/
static inline int valid_swap_request(struct ramzswap *rzs, struct bio *bio)
{
if (unlikely(
(bio->bi_sector >= (rzs->disksize >> SECTOR_SHIFT)) ||
(bio->bi_sector & (SECTORS_PER_PAGE - 1)) ||
(bio->bi_vcnt != 1) ||
(bio->bi_size != PAGE_SIZE) ||
(bio->bi_io_vec[0].bv_offset != 0))) {
return 0;
}
/* swap request is valid */
return 1;
}
/*
* Handler function for all ramzswap I/O requests.
*/
static int ramzswap_make_request(struct request_queue *queue, struct bio *bio)
{
int ret = 0;
struct ramzswap *rzs = queue->queuedata;
if (unlikely(!rzs->init_done)) {
bio_io_error(bio);
return 0;
}
if (!valid_swap_request(rzs, bio)) {
rzs_stat64_inc(rzs, &rzs->stats.invalid_io);
bio_io_error(bio);
return 0;
}
switch (bio_data_dir(bio)) {
case READ:
ret = ramzswap_read(rzs, bio);
break;
case WRITE:
ret = ramzswap_write(rzs, bio);
break;
}
return ret;
}
static void reset_device(struct ramzswap *rzs)
{
size_t index;
/* Do not accept any new I/O request */
rzs->init_done = 0;
/* Free various per-device buffers */
kfree(rzs->compress_workmem);
free_pages((unsigned long)rzs->compress_buffer, 1);
rzs->compress_workmem = NULL;
rzs->compress_buffer = NULL;
/* Free all pages that are still in this ramzswap device */
for (index = 0; index < rzs->disksize >> PAGE_SHIFT; index++) {
struct page *page;
u16 offset;
page = rzs->table[index].page;
offset = rzs->table[index].offset;
if (!page)
continue;
if (unlikely(rzs_test_flag(rzs, index, RZS_UNCOMPRESSED)))
__free_page(page);
else
xv_free(rzs->mem_pool, page, offset);
}
vfree(rzs->table);
rzs->table = NULL;
xv_destroy_pool(rzs->mem_pool);
rzs->mem_pool = NULL;
/* Reset stats */
memset(&rzs->stats, 0, sizeof(rzs->stats));
rzs->disksize = 0;
}
static int ramzswap_ioctl_init_device(struct ramzswap *rzs)
{
int ret;
size_t num_pages;
struct page *page;
union swap_header *swap_header;
if (rzs->init_done) {
pr_info("Device already initialized!\n");
return -EBUSY;
}
ramzswap_set_disksize(rzs, totalram_pages << PAGE_SHIFT);
rzs->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
if (!rzs->compress_workmem) {
pr_err("Error allocating compressor working memory!\n");
ret = -ENOMEM;
goto fail;
}
rzs->compress_buffer = (void *)__get_free_pages(__GFP_ZERO, 1);
if (!rzs->compress_buffer) {
pr_err("Error allocating compressor buffer space\n");
ret = -ENOMEM;
goto fail;
}
num_pages = rzs->disksize >> PAGE_SHIFT;
rzs->table = vmalloc(num_pages * sizeof(*rzs->table));
if (!rzs->table) {
pr_err("Error allocating ramzswap address table\n");
/* To prevent accessing table entries during cleanup */
rzs->disksize = 0;
ret = -ENOMEM;
goto fail;
}
memset(rzs->table, 0, num_pages * sizeof(*rzs->table));
page = alloc_page(__GFP_ZERO);
if (!page) {
pr_err("Error allocating swap header page\n");
ret = -ENOMEM;
goto fail;
}
rzs->table[0].page = page;
rzs_set_flag(rzs, 0, RZS_UNCOMPRESSED);
swap_header = kmap(page);
setup_swap_header(rzs, swap_header);
kunmap(page);
set_capacity(rzs->disk, rzs->disksize >> SECTOR_SHIFT);
/* ramzswap devices sort of resembles non-rotational disks */
queue_flag_set_unlocked(QUEUE_FLAG_NONROT, rzs->disk->queue);
rzs->mem_pool = xv_create_pool();
if (!rzs->mem_pool) {
pr_err("Error creating memory pool\n");
ret = -ENOMEM;
goto fail;
}
rzs->init_done = 1;
pr_debug("Initialization done!\n");
return 0;
fail:
reset_device(rzs);
pr_err("Initialization failed: err=%d\n", ret);
return ret;
}
static int ramzswap_ioctl_reset_device(struct ramzswap *rzs)
{
if (rzs->init_done)
reset_device(rzs);
return 0;
}
static int ramzswap_ioctl(struct block_device *bdev, fmode_t mode,
unsigned int cmd, unsigned long arg)
{
int ret = 0;
size_t disksize_kb;
struct ramzswap *rzs = bdev->bd_disk->private_data;
switch (cmd) {
case RZSIO_SET_DISKSIZE_KB:
if (rzs->init_done) {
ret = -EBUSY;
goto out;
}
if (copy_from_user(&disksize_kb, (void *)arg,
_IOC_SIZE(cmd))) {
ret = -EFAULT;
goto out;
}
rzs->disksize = disksize_kb << 10;
pr_info("Disk size set to %zu kB\n", disksize_kb);
break;
case RZSIO_GET_STATS:
{
struct ramzswap_ioctl_stats *stats;
if (!rzs->init_done) {
ret = -ENOTTY;
goto out;
}
stats = kzalloc(sizeof(*stats), GFP_KERNEL);
if (!stats) {
ret = -ENOMEM;
goto out;
}
ramzswap_ioctl_get_stats(rzs, stats);
if (copy_to_user((void *)arg, stats, sizeof(*stats))) {
kfree(stats);
ret = -EFAULT;
goto out;
}
kfree(stats);
break;
}
case RZSIO_INIT:
ret = ramzswap_ioctl_init_device(rzs);
break;
case RZSIO_RESET:
/* Do not reset an active device! */
if (bdev->bd_holders) {
ret = -EBUSY;
goto out;
}
/* Make sure all pending I/O is finished */
if (bdev)
fsync_bdev(bdev);
ret = ramzswap_ioctl_reset_device(rzs);
break;
default:
pr_info("Invalid ioctl %u\n", cmd);
ret = -ENOTTY;
}
out:
return ret;
}
void ramzswap_slot_free_notify(struct block_device *bdev, unsigned long index)
{
struct ramzswap *rzs;
rzs = bdev->bd_disk->private_data;
ramzswap_free_page(rzs, index);
rzs_stat64_inc(rzs, &rzs->stats.notify_free);
return;
}
static struct block_device_operations ramzswap_devops = {
.ioctl = ramzswap_ioctl,
.swap_slot_free_notify = ramzswap_slot_free_notify,
.owner = THIS_MODULE
};
static int create_device(struct ramzswap *rzs, int device_id)
{
int ret = 0;
mutex_init(&rzs->lock);
spin_lock_init(&rzs->stat64_lock);
rzs->queue = blk_alloc_queue(GFP_KERNEL);
if (!rzs->queue) {
pr_err("Error allocating disk queue for device %d\n",
device_id);
ret = -ENOMEM;
goto out;
}
blk_queue_make_request(rzs->queue, ramzswap_make_request);
rzs->queue->queuedata = rzs;
/* gendisk structure */
rzs->disk = alloc_disk(1);
if (!rzs->disk) {
blk_cleanup_queue(rzs->queue);
pr_warning("Error allocating disk structure for device %d\n",
device_id);
ret = -ENOMEM;
goto out;
}
rzs->disk->major = ramzswap_major;
rzs->disk->first_minor = device_id;
rzs->disk->fops = &ramzswap_devops;
rzs->disk->queue = rzs->queue;
rzs->disk->private_data = rzs;
snprintf(rzs->disk->disk_name, 16, "ramzswap%d", device_id);
/* Actual capacity set using RZSIO_SET_DISKSIZE_KB ioctl */
set_capacity(rzs->disk, 0);
blk_queue_physical_block_size(rzs->disk->queue, PAGE_SIZE);
blk_queue_logical_block_size(rzs->disk->queue, PAGE_SIZE);
add_disk(rzs->disk);
rzs->init_done = 0;
out:
return ret;
}
static void destroy_device(struct ramzswap *rzs)
{
if (rzs->disk) {
del_gendisk(rzs->disk);
put_disk(rzs->disk);
}
if (rzs->queue)
blk_cleanup_queue(rzs->queue);
}
static int __init ramzswap_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;
}
ramzswap_major = register_blkdev(0, "ramzswap");
if (ramzswap_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 ramzswap), 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]);
unregister:
unregister_blkdev(ramzswap_major, "ramzswap");
out:
return ret;
}
static void __exit ramzswap_exit(void)
{
int i;
struct ramzswap *rzs;
for (i = 0; i < num_devices; i++) {
rzs = &devices[i];
destroy_device(rzs);
if (rzs->init_done)
reset_device(rzs);
}
unregister_blkdev(ramzswap_major, "ramzswap");
kfree(devices);
pr_debug("Cleanup done!\n");
}
module_param(num_devices, uint, 0);
MODULE_PARM_DESC(num_devices, "Number of ramzswap devices");
module_init(ramzswap_init);
module_exit(ramzswap_exit);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
MODULE_DESCRIPTION("Compressed RAM Based Swap Device");
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