Staging: ramzswap: Remove backing swap support

[mirror_ubuntu-hirsute-kernel.git] / drivers / staging / ramzswap / ramzswap_drv.c

/*
 * 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;

        /*
         * System swaps to same sector again when the stored page
         * is no longer referenced by any process. So, its now safe
         * to free the memory that was allocated for this page.
         */
        if (rzs->table[index].page || rzs_test_flag(rzs, index, RZS_ZERO))
                ramzswap_free_page(rzs, index);

        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;
}

static struct block_device_operations ramzswap_devops = {
        .ioctl = ramzswap_ioctl,
        .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");