Staging: Rename ramzswap files to zram

Related changes:
 - Modify revelant Kconfig and Makefile accordingly.
 - Change include filenames in code.
 - Remove dependency on CONFIG_SWAP in Kconfig as zram usage
is no longer limited to swap disks.

Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 805 insertions, 0 deletions

diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
new file mode 100644
index 0000000..e9b064c
--- /dev/null
+++ b/drivers/staging/zram/zram_drv.c
@@ -0,0 +1,805 @@
+/*
+ * 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 "zram_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;
+}
+
+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 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 ramzswap *rzs,
+				struct page *page, u32 index)
+{
+	unsigned char *user_mem, *cmem;
+
+	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);
+}
+
+static int ramzswap_read(struct ramzswap *rzs, struct bio *bio)
+{
+
+	int i;
+	u32 index;
+	struct bio_vec *bvec;
+
+	rzs_stat64_inc(rzs, &rzs->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 (rzs_test_flag(rzs, index, RZS_ZERO)) {
+			handle_zero_page(page);
+			continue;
+		}
+
+		/* Requested page is not present in compressed area */
+		if (unlikely(!rzs->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(rzs_test_flag(rzs, index, RZS_UNCOMPRESSED))) {
+			handle_uncompressed_page(rzs, page, index);
+			continue;
+		}
+
+		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. Return bio error if it does. */
+		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);
+		index++;
+	}
+
+	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 i;
+	u32 index;
+	struct bio_vec *bvec;
+
+	rzs_stat64_inc(rzs, &rzs->stats.num_writes);
+
+	index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
+
+	bio_for_each_segment(bvec, bio, i) {
+		int ret;
+		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 = rzs->compress_buffer;
+
+		/*
+		 * System overwrites unused sectors. Free memory associated
+		 * with this sector now.
+		 */
+		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);
+			continue;
+		}
+
+		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);
+		index++;
+	}
+
+	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_io_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_size & (PAGE_SIZE - 1)))) {
+
+		return 0;
+	}
+
+	/* I/O 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_io_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;
+
+	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));
+
+	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);
+}
+
+static const 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);
+
+	/*
+	 * To ensure that we always get PAGE_SIZE aligned
+	 * and n*PAGE_SIZED sized I/O requests.
+	 */
+	blk_queue_physical_block_size(rzs->disk->queue, PAGE_SIZE);
+	blk_queue_logical_block_size(rzs->disk->queue, PAGE_SIZE);
+	blk_queue_io_min(rzs->disk->queue, PAGE_SIZE);
+	blk_queue_io_opt(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");