Initial import

1 files changed, 1322 insertions, 0 deletions

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
new file mode 100644
index 000000000..6e134f475
--- /dev/null
+++ b/drivers/block/zram/zram_drv.c
@@ -0,0 +1,1322 @@
+/*
+ * Compressed RAM block device
+ *
+ * Copyright (C) 2008, 2009, 2010  Nitin Gupta
+ *               2012, 2013 Minchan Kim
+ *
+ * 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
+ *
+ */
+
+#define KMSG_COMPONENT "zram"
+#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
+
+#ifdef CONFIG_ZRAM_DEBUG
+#define DEBUG
+#endif
+
+#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/string.h>
+#include <linux/vmalloc.h>
+#include <linux/err.h>
+
+#include "zram_drv.h"
+
+/* Globals */
+static int zram_major;
+static struct zram *zram_devices;
+static const char *default_compressor = "lzo";
+
+/* Module params (documentation at end) */
+static unsigned int num_devices = 1;
+
+static inline void deprecated_attr_warn(const char *name)
+{
+	pr_warn_once("%d (%s) Attribute %s (and others) will be removed. %s\n",
+			task_pid_nr(current),
+			current->comm,
+			name,
+			"See zram documentation.");
+}
+
+#define ZRAM_ATTR_RO(name)						\
+static ssize_t name##_show(struct device *d,		\
+				struct device_attribute *attr, char *b)	\
+{									\
+	struct zram *zram = dev_to_zram(d);				\
+									\
+	deprecated_attr_warn(__stringify(name));			\
+	return scnprintf(b, PAGE_SIZE, "%llu\n",			\
+		(u64)atomic64_read(&zram->stats.name));			\
+}									\
+static DEVICE_ATTR_RO(name);
+
+static inline bool init_done(struct zram *zram)
+{
+	return zram->disksize;
+}
+
+static inline struct zram *dev_to_zram(struct device *dev)
+{
+	return (struct zram *)dev_to_disk(dev)->private_data;
+}
+
+static ssize_t compact_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	unsigned long nr_migrated;
+	struct zram *zram = dev_to_zram(dev);
+	struct zram_meta *meta;
+
+	down_read(&zram->init_lock);
+	if (!init_done(zram)) {
+		up_read(&zram->init_lock);
+		return -EINVAL;
+	}
+
+	meta = zram->meta;
+	nr_migrated = zs_compact(meta->mem_pool);
+	atomic64_add(nr_migrated, &zram->stats.num_migrated);
+	up_read(&zram->init_lock);
+
+	return len;
+}
+
+static ssize_t disksize_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct zram *zram = dev_to_zram(dev);
+
+	return scnprintf(buf, PAGE_SIZE, "%llu\n", zram->disksize);
+}
+
+static ssize_t initstate_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	u32 val;
+	struct zram *zram = dev_to_zram(dev);
+
+	down_read(&zram->init_lock);
+	val = init_done(zram);
+	up_read(&zram->init_lock);
+
+	return scnprintf(buf, PAGE_SIZE, "%u\n", val);
+}
+
+static ssize_t orig_data_size_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct zram *zram = dev_to_zram(dev);
+
+	deprecated_attr_warn("orig_data_size");
+	return scnprintf(buf, PAGE_SIZE, "%llu\n",
+		(u64)(atomic64_read(&zram->stats.pages_stored)) << PAGE_SHIFT);
+}
+
+static ssize_t mem_used_total_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	u64 val = 0;
+	struct zram *zram = dev_to_zram(dev);
+
+	deprecated_attr_warn("mem_used_total");
+	down_read(&zram->init_lock);
+	if (init_done(zram)) {
+		struct zram_meta *meta = zram->meta;
+		val = zs_get_total_pages(meta->mem_pool);
+	}
+	up_read(&zram->init_lock);
+
+	return scnprintf(buf, PAGE_SIZE, "%llu\n", val << PAGE_SHIFT);
+}
+
+static ssize_t max_comp_streams_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	int val;
+	struct zram *zram = dev_to_zram(dev);
+
+	down_read(&zram->init_lock);
+	val = zram->max_comp_streams;
+	up_read(&zram->init_lock);
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", val);
+}
+
+static ssize_t mem_limit_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	u64 val;
+	struct zram *zram = dev_to_zram(dev);
+
+	deprecated_attr_warn("mem_limit");
+	down_read(&zram->init_lock);
+	val = zram->limit_pages;
+	up_read(&zram->init_lock);
+
+	return scnprintf(buf, PAGE_SIZE, "%llu\n", val << PAGE_SHIFT);
+}
+
+static ssize_t mem_limit_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	u64 limit;
+	char *tmp;
+	struct zram *zram = dev_to_zram(dev);
+
+	limit = memparse(buf, &tmp);
+	if (buf == tmp) /* no chars parsed, invalid input */
+		return -EINVAL;
+
+	down_write(&zram->init_lock);
+	zram->limit_pages = PAGE_ALIGN(limit) >> PAGE_SHIFT;
+	up_write(&zram->init_lock);
+
+	return len;
+}
+
+static ssize_t mem_used_max_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	u64 val = 0;
+	struct zram *zram = dev_to_zram(dev);
+
+	deprecated_attr_warn("mem_used_max");
+	down_read(&zram->init_lock);
+	if (init_done(zram))
+		val = atomic_long_read(&zram->stats.max_used_pages);
+	up_read(&zram->init_lock);
+
+	return scnprintf(buf, PAGE_SIZE, "%llu\n", val << PAGE_SHIFT);
+}
+
+static ssize_t mem_used_max_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	int err;
+	unsigned long val;
+	struct zram *zram = dev_to_zram(dev);
+
+	err = kstrtoul(buf, 10, &val);
+	if (err || val != 0)
+		return -EINVAL;
+
+	down_read(&zram->init_lock);
+	if (init_done(zram)) {
+		struct zram_meta *meta = zram->meta;
+		atomic_long_set(&zram->stats.max_used_pages,
+				zs_get_total_pages(meta->mem_pool));
+	}
+	up_read(&zram->init_lock);
+
+	return len;
+}
+
+static ssize_t max_comp_streams_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	int num;
+	struct zram *zram = dev_to_zram(dev);
+	int ret;
+
+	ret = kstrtoint(buf, 0, &num);
+	if (ret < 0)
+		return ret;
+	if (num < 1)
+		return -EINVAL;
+
+	down_write(&zram->init_lock);
+	if (init_done(zram)) {
+		if (!zcomp_set_max_streams(zram->comp, num)) {
+			pr_info("Cannot change max compression streams\n");
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+
+	zram->max_comp_streams = num;
+	ret = len;
+out:
+	up_write(&zram->init_lock);
+	return ret;
+}
+
+static ssize_t comp_algorithm_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	size_t sz;
+	struct zram *zram = dev_to_zram(dev);
+
+	down_read(&zram->init_lock);
+	sz = zcomp_available_show(zram->compressor, buf);
+	up_read(&zram->init_lock);
+
+	return sz;
+}
+
+static ssize_t comp_algorithm_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	struct zram *zram = dev_to_zram(dev);
+	down_write(&zram->init_lock);
+	if (init_done(zram)) {
+		up_write(&zram->init_lock);
+		pr_info("Can't change algorithm for initialized device\n");
+		return -EBUSY;
+	}
+	strlcpy(zram->compressor, buf, sizeof(zram->compressor));
+	up_write(&zram->init_lock);
+	return len;
+}
+
+/* flag operations needs meta->tb_lock */
+static int zram_test_flag(struct zram_meta *meta, u32 index,
+			enum zram_pageflags flag)
+{
+	return meta->table[index].value & BIT(flag);
+}
+
+static void zram_set_flag(struct zram_meta *meta, u32 index,
+			enum zram_pageflags flag)
+{
+	meta->table[index].value |= BIT(flag);
+}
+
+static void zram_clear_flag(struct zram_meta *meta, u32 index,
+			enum zram_pageflags flag)
+{
+	meta->table[index].value &= ~BIT(flag);
+}
+
+static size_t zram_get_obj_size(struct zram_meta *meta, u32 index)
+{
+	return meta->table[index].value & (BIT(ZRAM_FLAG_SHIFT) - 1);
+}
+
+static void zram_set_obj_size(struct zram_meta *meta,
+					u32 index, size_t size)
+{
+	unsigned long flags = meta->table[index].value >> ZRAM_FLAG_SHIFT;
+
+	meta->table[index].value = (flags << ZRAM_FLAG_SHIFT) | size;
+}
+
+static inline int is_partial_io(struct bio_vec *bvec)
+{
+	return bvec->bv_len != PAGE_SIZE;
+}
+
+/*
+ * Check if request is within bounds and aligned on zram logical blocks.
+ */
+static inline int valid_io_request(struct zram *zram,
+		sector_t start, unsigned int size)
+{
+	u64 end, bound;
+
+	/* unaligned request */
+	if (unlikely(start & (ZRAM_SECTOR_PER_LOGICAL_BLOCK - 1)))
+		return 0;
+	if (unlikely(size & (ZRAM_LOGICAL_BLOCK_SIZE - 1)))
+		return 0;
+
+	end = start + (size >> SECTOR_SHIFT);
+	bound = zram->disksize >> SECTOR_SHIFT;
+	/* out of range range */
+	if (unlikely(start >= bound || end > bound || start > end))
+		return 0;
+
+	/* I/O request is valid */
+	return 1;
+}
+
+static void zram_meta_free(struct zram_meta *meta, u64 disksize)
+{
+	size_t num_pages = disksize >> PAGE_SHIFT;
+	size_t index;
+
+	/* Free all pages that are still in this zram device */
+	for (index = 0; index < num_pages; index++) {
+		unsigned long handle = meta->table[index].handle;
+
+		if (!handle)
+			continue;
+
+		zs_free(meta->mem_pool, handle);
+	}
+
+	zs_destroy_pool(meta->mem_pool);
+	vfree(meta->table);
+	kfree(meta);
+}
+
+static struct zram_meta *zram_meta_alloc(int device_id, u64 disksize)
+{
+	size_t num_pages;
+	char pool_name[8];
+	struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL);
+
+	if (!meta)
+		return NULL;
+
+	num_pages = disksize >> PAGE_SHIFT;
+	meta->table = vzalloc(num_pages * sizeof(*meta->table));
+	if (!meta->table) {
+		pr_err("Error allocating zram address table\n");
+		goto out_error;
+	}
+
+	snprintf(pool_name, sizeof(pool_name), "zram%d", device_id);
+	meta->mem_pool = zs_create_pool(pool_name, GFP_NOIO | __GFP_HIGHMEM);
+	if (!meta->mem_pool) {
+		pr_err("Error creating memory pool\n");
+		goto out_error;
+	}
+
+	return meta;
+
+out_error:
+	vfree(meta->table);
+	kfree(meta);
+	return NULL;
+}
+
+static inline bool zram_meta_get(struct zram *zram)
+{
+	if (atomic_inc_not_zero(&zram->refcount))
+		return true;
+	return false;
+}
+
+static inline void zram_meta_put(struct zram *zram)
+{
+	atomic_dec(&zram->refcount);
+}
+
+static void update_position(u32 *index, int *offset, struct bio_vec *bvec)
+{
+	if (*offset + bvec->bv_len >= PAGE_SIZE)
+		(*index)++;
+	*offset = (*offset + bvec->bv_len) % PAGE_SIZE;
+}
+
+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 handle_zero_page(struct bio_vec *bvec)
+{
+	struct page *page = bvec->bv_page;
+	void *user_mem;
+
+	user_mem = kmap_atomic(page);
+	if (is_partial_io(bvec))
+		memset(user_mem + bvec->bv_offset, 0, bvec->bv_len);
+	else
+		clear_page(user_mem);
+	kunmap_atomic(user_mem);
+
+	flush_dcache_page(page);
+}
+
+
+/*
+ * To protect concurrent access to the same index entry,
+ * caller should hold this table index entry's bit_spinlock to
+ * indicate this index entry is accessing.
+ */
+static void zram_free_page(struct zram *zram, size_t index)
+{
+	struct zram_meta *meta = zram->meta;
+	unsigned long handle = meta->table[index].handle;
+
+	if (unlikely(!handle)) {
+		/*
+		 * No memory is allocated for zero filled pages.
+		 * Simply clear zero page flag.
+		 */
+		if (zram_test_flag(meta, index, ZRAM_ZERO)) {
+			zram_clear_flag(meta, index, ZRAM_ZERO);
+			atomic64_dec(&zram->stats.zero_pages);
+		}
+		return;
+	}
+
+	zs_free(meta->mem_pool, handle);
+
+	atomic64_sub(zram_get_obj_size(meta, index),
+			&zram->stats.compr_data_size);
+	atomic64_dec(&zram->stats.pages_stored);
+
+	meta->table[index].handle = 0;
+	zram_set_obj_size(meta, index, 0);
+}
+
+static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
+{
+	int ret = 0;
+	unsigned char *cmem;
+	struct zram_meta *meta = zram->meta;
+	unsigned long handle;
+	size_t size;
+
+	bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
+	handle = meta->table[index].handle;
+	size = zram_get_obj_size(meta, index);
+
+	if (!handle || zram_test_flag(meta, index, ZRAM_ZERO)) {
+		bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
+		clear_page(mem);
+		return 0;
+	}
+
+	cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);
+	if (size == PAGE_SIZE)
+		copy_page(mem, cmem);
+	else
+		ret = zcomp_decompress(zram->comp, cmem, size, mem);
+	zs_unmap_object(meta->mem_pool, handle);
+	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
+
+	/* Should NEVER happen. Return bio error if it does. */
+	if (unlikely(ret)) {
+		pr_err("Decompression failed! err=%d, page=%u\n", ret, index);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
+			  u32 index, int offset)
+{
+	int ret;
+	struct page *page;
+	unsigned char *user_mem, *uncmem = NULL;
+	struct zram_meta *meta = zram->meta;
+	page = bvec->bv_page;
+
+	bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
+	if (unlikely(!meta->table[index].handle) ||
+			zram_test_flag(meta, index, ZRAM_ZERO)) {
+		bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
+		handle_zero_page(bvec);
+		return 0;
+	}
+	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
+
+	if (is_partial_io(bvec))
+		/* Use  a temporary buffer to decompress the page */
+		uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
+
+	user_mem = kmap_atomic(page);
+	if (!is_partial_io(bvec))
+		uncmem = user_mem;
+
+	if (!uncmem) {
+		pr_info("Unable to allocate temp memory\n");
+		ret = -ENOMEM;
+		goto out_cleanup;
+	}
+
+	ret = zram_decompress_page(zram, uncmem, index);
+	/* Should NEVER happen. Return bio error if it does. */
+	if (unlikely(ret))
+		goto out_cleanup;
+
+	if (is_partial_io(bvec))
+		memcpy(user_mem + bvec->bv_offset, uncmem + offset,
+				bvec->bv_len);
+
+	flush_dcache_page(page);
+	ret = 0;
+out_cleanup:
+	kunmap_atomic(user_mem);
+	if (is_partial_io(bvec))
+		kfree(uncmem);
+	return ret;
+}
+
+static inline void update_used_max(struct zram *zram,
+					const unsigned long pages)
+{
+	unsigned long old_max, cur_max;
+
+	old_max = atomic_long_read(&zram->stats.max_used_pages);
+
+	do {
+		cur_max = old_max;
+		if (pages > cur_max)
+			old_max = atomic_long_cmpxchg(
+				&zram->stats.max_used_pages, cur_max, pages);
+	} while (old_max != cur_max);
+}
+
+static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
+			   int offset)
+{
+	int ret = 0;
+	size_t clen;
+	unsigned long handle;
+	struct page *page;
+	unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
+	struct zram_meta *meta = zram->meta;
+	struct zcomp_strm *zstrm;
+	bool locked = false;
+	unsigned long alloced_pages;
+
+	page = bvec->bv_page;
+	if (is_partial_io(bvec)) {
+		/*
+		 * This is a partial IO. We need to read the full page
+		 * before to write the changes.
+		 */
+		uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
+		if (!uncmem) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		ret = zram_decompress_page(zram, uncmem, index);
+		if (ret)
+			goto out;
+	}
+
+	zstrm = zcomp_strm_find(zram->comp);
+	locked = true;
+	user_mem = kmap_atomic(page);
+
+	if (is_partial_io(bvec)) {
+		memcpy(uncmem + offset, user_mem + bvec->bv_offset,
+		       bvec->bv_len);
+		kunmap_atomic(user_mem);
+		user_mem = NULL;
+	} else {
+		uncmem = user_mem;
+	}
+
+	if (page_zero_filled(uncmem)) {
+		if (user_mem)
+			kunmap_atomic(user_mem);
+		/* Free memory associated with this sector now. */
+		bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
+		zram_free_page(zram, index);
+		zram_set_flag(meta, index, ZRAM_ZERO);
+		bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
+
+		atomic64_inc(&zram->stats.zero_pages);
+		ret = 0;
+		goto out;
+	}
+
+	ret = zcomp_compress(zram->comp, zstrm, uncmem, &clen);
+	if (!is_partial_io(bvec)) {
+		kunmap_atomic(user_mem);
+		user_mem = NULL;
+		uncmem = NULL;
+	}
+
+	if (unlikely(ret)) {
+		pr_err("Compression failed! err=%d\n", ret);
+		goto out;
+	}
+	src = zstrm->buffer;
+	if (unlikely(clen > max_zpage_size)) {
+		clen = PAGE_SIZE;
+		if (is_partial_io(bvec))
+			src = uncmem;
+	}
+
+	handle = zs_malloc(meta->mem_pool, clen);
+	if (!handle) {
+		pr_info("Error allocating memory for compressed page: %u, size=%zu\n",
+			index, clen);
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	alloced_pages = zs_get_total_pages(meta->mem_pool);
+	if (zram->limit_pages && alloced_pages > zram->limit_pages) {
+		zs_free(meta->mem_pool, handle);
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	update_used_max(zram, alloced_pages);
+
+	cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
+
+	if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
+		src = kmap_atomic(page);
+		copy_page(cmem, src);
+		kunmap_atomic(src);
+	} else {
+		memcpy(cmem, src, clen);
+	}
+
+	zcomp_strm_release(zram->comp, zstrm);
+	locked = false;
+	zs_unmap_object(meta->mem_pool, handle);
+
+	/*
+	 * Free memory associated with this sector
+	 * before overwriting unused sectors.
+	 */
+	bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
+	zram_free_page(zram, index);
+
+	meta->table[index].handle = handle;
+	zram_set_obj_size(meta, index, clen);
+	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
+
+	/* Update stats */
+	atomic64_add(clen, &zram->stats.compr_data_size);
+	atomic64_inc(&zram->stats.pages_stored);
+out:
+	if (locked)
+		zcomp_strm_release(zram->comp, zstrm);
+	if (is_partial_io(bvec))
+		kfree(uncmem);
+	return ret;
+}
+
+static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index,
+			int offset, int rw)
+{
+	unsigned long start_time = jiffies;
+	int ret;
+
+	generic_start_io_acct(rw, bvec->bv_len >> SECTOR_SHIFT,
+			&zram->disk->part0);
+
+	if (rw == READ) {
+		atomic64_inc(&zram->stats.num_reads);
+		ret = zram_bvec_read(zram, bvec, index, offset);
+	} else {
+		atomic64_inc(&zram->stats.num_writes);
+		ret = zram_bvec_write(zram, bvec, index, offset);
+	}
+
+	generic_end_io_acct(rw, &zram->disk->part0, start_time);
+
+	if (unlikely(ret)) {
+		if (rw == READ)
+			atomic64_inc(&zram->stats.failed_reads);
+		else
+			atomic64_inc(&zram->stats.failed_writes);
+	}
+
+	return ret;
+}
+
+/*
+ * zram_bio_discard - handler on discard request
+ * @index: physical block index in PAGE_SIZE units
+ * @offset: byte offset within physical block
+ */
+static void zram_bio_discard(struct zram *zram, u32 index,
+			     int offset, struct bio *bio)
+{
+	size_t n = bio->bi_iter.bi_size;
+	struct zram_meta *meta = zram->meta;
+
+	/*
+	 * zram manages data in physical block size units. Because logical block
+	 * size isn't identical with physical block size on some arch, we
+	 * could get a discard request pointing to a specific offset within a
+	 * certain physical block.  Although we can handle this request by
+	 * reading that physiclal block and decompressing and partially zeroing
+	 * and re-compressing and then re-storing it, this isn't reasonable
+	 * because our intent with a discard request is to save memory.  So
+	 * skipping this logical block is appropriate here.
+	 */
+	if (offset) {
+		if (n <= (PAGE_SIZE - offset))
+			return;
+
+		n -= (PAGE_SIZE - offset);
+		index++;
+	}
+
+	while (n >= PAGE_SIZE) {
+		bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
+		zram_free_page(zram, index);
+		bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
+		atomic64_inc(&zram->stats.notify_free);
+		index++;
+		n -= PAGE_SIZE;
+	}
+}
+
+static void zram_reset_device(struct zram *zram)
+{
+	struct zram_meta *meta;
+	struct zcomp *comp;
+	u64 disksize;
+
+	down_write(&zram->init_lock);
+
+	zram->limit_pages = 0;
+
+	if (!init_done(zram)) {
+		up_write(&zram->init_lock);
+		return;
+	}
+
+	meta = zram->meta;
+	comp = zram->comp;
+	disksize = zram->disksize;
+	/*
+	 * Refcount will go down to 0 eventually and r/w handler
+	 * cannot handle further I/O so it will bail out by
+	 * check zram_meta_get.
+	 */
+	zram_meta_put(zram);
+	/*
+	 * We want to free zram_meta in process context to avoid
+	 * deadlock between reclaim path and any other locks.
+	 */
+	wait_event(zram->io_done, atomic_read(&zram->refcount) == 0);
+
+	/* Reset stats */
+	memset(&zram->stats, 0, sizeof(zram->stats));
+	zram->disksize = 0;
+	zram->max_comp_streams = 1;
+
+	set_capacity(zram->disk, 0);
+	part_stat_set_all(&zram->disk->part0, 0);
+
+	up_write(&zram->init_lock);
+	/* I/O operation under all of CPU are done so let's free */
+	zram_meta_free(meta, disksize);
+	zcomp_destroy(comp);
+}
+
+static ssize_t disksize_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	u64 disksize;
+	struct zcomp *comp;
+	struct zram_meta *meta;
+	struct zram *zram = dev_to_zram(dev);
+	int err;
+
+	disksize = memparse(buf, NULL);
+	if (!disksize)
+		return -EINVAL;
+
+	disksize = PAGE_ALIGN(disksize);
+	meta = zram_meta_alloc(zram->disk->first_minor, disksize);
+	if (!meta)
+		return -ENOMEM;
+
+	comp = zcomp_create(zram->compressor, zram->max_comp_streams);
+	if (IS_ERR(comp)) {
+		pr_info("Cannot initialise %s compressing backend\n",
+				zram->compressor);
+		err = PTR_ERR(comp);
+		goto out_free_meta;
+	}
+
+	down_write(&zram->init_lock);
+	if (init_done(zram)) {
+		pr_info("Cannot change disksize for initialized device\n");
+		err = -EBUSY;
+		goto out_destroy_comp;
+	}
+
+	init_waitqueue_head(&zram->io_done);
+	atomic_set(&zram->refcount, 1);
+	zram->meta = meta;
+	zram->comp = comp;
+	zram->disksize = disksize;
+	set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
+	up_write(&zram->init_lock);
+
+	/*
+	 * Revalidate disk out of the init_lock to avoid lockdep splat.
+	 * It's okay because disk's capacity is protected by init_lock
+	 * so that revalidate_disk always sees up-to-date capacity.
+	 */
+	revalidate_disk(zram->disk);
+
+	return len;
+
+out_destroy_comp:
+	up_write(&zram->init_lock);
+	zcomp_destroy(comp);
+out_free_meta:
+	zram_meta_free(meta, disksize);
+	return err;
+}
+
+static ssize_t reset_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	int ret;
+	unsigned short do_reset;
+	struct zram *zram;
+	struct block_device *bdev;
+
+	zram = dev_to_zram(dev);
+	bdev = bdget_disk(zram->disk, 0);
+
+	if (!bdev)
+		return -ENOMEM;
+
+	mutex_lock(&bdev->bd_mutex);
+	/* Do not reset an active device! */
+	if (bdev->bd_openers) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	ret = kstrtou16(buf, 10, &do_reset);
+	if (ret)
+		goto out;
+
+	if (!do_reset) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* Make sure all pending I/O is finished */
+	fsync_bdev(bdev);
+	zram_reset_device(zram);
+
+	mutex_unlock(&bdev->bd_mutex);
+	revalidate_disk(zram->disk);
+	bdput(bdev);
+
+	return len;
+
+out:
+	mutex_unlock(&bdev->bd_mutex);
+	bdput(bdev);
+	return ret;
+}
+
+static void __zram_make_request(struct zram *zram, struct bio *bio)
+{
+	int offset, rw;
+	u32 index;
+	struct bio_vec bvec;
+	struct bvec_iter iter;
+
+	index = bio->bi_iter.bi_sector >> SECTORS_PER_PAGE_SHIFT;
+	offset = (bio->bi_iter.bi_sector &
+		  (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT;
+
+	if (unlikely(bio->bi_rw & REQ_DISCARD)) {
+		zram_bio_discard(zram, index, offset, bio);
+		bio_endio(bio, 0);
+		return;
+	}
+
+	rw = bio_data_dir(bio);
+	bio_for_each_segment(bvec, bio, iter) {
+		int max_transfer_size = PAGE_SIZE - offset;
+
+		if (bvec.bv_len > max_transfer_size) {
+			/*
+			 * zram_bvec_rw() can only make operation on a single
+			 * zram page. Split the bio vector.
+			 */
+			struct bio_vec bv;
+
+			bv.bv_page = bvec.bv_page;
+			bv.bv_len = max_transfer_size;
+			bv.bv_offset = bvec.bv_offset;
+
+			if (zram_bvec_rw(zram, &bv, index, offset, rw) < 0)
+				goto out;
+
+			bv.bv_len = bvec.bv_len - max_transfer_size;
+			bv.bv_offset += max_transfer_size;
+			if (zram_bvec_rw(zram, &bv, index + 1, 0, rw) < 0)
+				goto out;
+		} else
+			if (zram_bvec_rw(zram, &bvec, index, offset, rw) < 0)
+				goto out;
+
+		update_position(&index, &offset, &bvec);
+	}
+
+	set_bit(BIO_UPTODATE, &bio->bi_flags);
+	bio_endio(bio, 0);
+	return;
+
+out:
+	bio_io_error(bio);
+}
+
+/*
+ * Handler function for all zram I/O requests.
+ */
+static void zram_make_request(struct request_queue *queue, struct bio *bio)
+{
+	struct zram *zram = queue->queuedata;
+
+	if (unlikely(!zram_meta_get(zram)))
+		goto error;
+
+	if (!valid_io_request(zram, bio->bi_iter.bi_sector,
+					bio->bi_iter.bi_size)) {
+		atomic64_inc(&zram->stats.invalid_io);
+		goto put_zram;
+	}
+
+	__zram_make_request(zram, bio);
+	zram_meta_put(zram);
+	return;
+put_zram:
+	zram_meta_put(zram);
+error:
+	bio_io_error(bio);
+}
+
+static void zram_slot_free_notify(struct block_device *bdev,
+				unsigned long index)
+{
+	struct zram *zram;
+	struct zram_meta *meta;
+
+	zram = bdev->bd_disk->private_data;
+	meta = zram->meta;
+
+	bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
+	zram_free_page(zram, index);
+	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
+	atomic64_inc(&zram->stats.notify_free);
+}
+
+static int zram_rw_page(struct block_device *bdev, sector_t sector,
+		       struct page *page, int rw)
+{
+	int offset, err = -EIO;
+	u32 index;
+	struct zram *zram;
+	struct bio_vec bv;
+
+	zram = bdev->bd_disk->private_data;
+	if (unlikely(!zram_meta_get(zram)))
+		goto out;
+
+	if (!valid_io_request(zram, sector, PAGE_SIZE)) {
+		atomic64_inc(&zram->stats.invalid_io);
+		err = -EINVAL;
+		goto put_zram;
+	}
+
+	index = sector >> SECTORS_PER_PAGE_SHIFT;
+	offset = sector & (SECTORS_PER_PAGE - 1) << SECTOR_SHIFT;
+
+	bv.bv_page = page;
+	bv.bv_len = PAGE_SIZE;
+	bv.bv_offset = 0;
+
+	err = zram_bvec_rw(zram, &bv, index, offset, rw);
+put_zram:
+	zram_meta_put(zram);
+out:
+	/*
+	 * If I/O fails, just return error(ie, non-zero) without
+	 * calling page_endio.
+	 * It causes resubmit the I/O with bio request by upper functions
+	 * of rw_page(e.g., swap_readpage, __swap_writepage) and
+	 * bio->bi_end_io does things to handle the error
+	 * (e.g., SetPageError, set_page_dirty and extra works).
+	 */
+	if (err == 0)
+		page_endio(page, rw, 0);
+	return err;
+}
+
+static const struct block_device_operations zram_devops = {
+	.swap_slot_free_notify = zram_slot_free_notify,
+	.rw_page = zram_rw_page,
+	.owner = THIS_MODULE
+};
+
+static DEVICE_ATTR_WO(compact);
+static DEVICE_ATTR_RW(disksize);
+static DEVICE_ATTR_RO(initstate);
+static DEVICE_ATTR_WO(reset);
+static DEVICE_ATTR_RO(orig_data_size);
+static DEVICE_ATTR_RO(mem_used_total);
+static DEVICE_ATTR_RW(mem_limit);
+static DEVICE_ATTR_RW(mem_used_max);
+static DEVICE_ATTR_RW(max_comp_streams);
+static DEVICE_ATTR_RW(comp_algorithm);
+
+static ssize_t io_stat_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct zram *zram = dev_to_zram(dev);
+	ssize_t ret;
+
+	down_read(&zram->init_lock);
+	ret = scnprintf(buf, PAGE_SIZE,
+			"%8llu %8llu %8llu %8llu\n",
+			(u64)atomic64_read(&zram->stats.failed_reads),
+			(u64)atomic64_read(&zram->stats.failed_writes),
+			(u64)atomic64_read(&zram->stats.invalid_io),
+			(u64)atomic64_read(&zram->stats.notify_free));
+	up_read(&zram->init_lock);
+
+	return ret;
+}
+
+static ssize_t mm_stat_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct zram *zram = dev_to_zram(dev);
+	u64 orig_size, mem_used = 0;
+	long max_used;
+	ssize_t ret;
+
+	down_read(&zram->init_lock);
+	if (init_done(zram))
+		mem_used = zs_get_total_pages(zram->meta->mem_pool);
+
+	orig_size = atomic64_read(&zram->stats.pages_stored);
+	max_used = atomic_long_read(&zram->stats.max_used_pages);
+
+	ret = scnprintf(buf, PAGE_SIZE,
+			"%8llu %8llu %8llu %8lu %8ld %8llu %8llu\n",
+			orig_size << PAGE_SHIFT,
+			(u64)atomic64_read(&zram->stats.compr_data_size),
+			mem_used << PAGE_SHIFT,
+			zram->limit_pages << PAGE_SHIFT,
+			max_used << PAGE_SHIFT,
+			(u64)atomic64_read(&zram->stats.zero_pages),
+			(u64)atomic64_read(&zram->stats.num_migrated));
+	up_read(&zram->init_lock);
+
+	return ret;
+}
+
+static DEVICE_ATTR_RO(io_stat);
+static DEVICE_ATTR_RO(mm_stat);
+ZRAM_ATTR_RO(num_reads);
+ZRAM_ATTR_RO(num_writes);
+ZRAM_ATTR_RO(failed_reads);
+ZRAM_ATTR_RO(failed_writes);
+ZRAM_ATTR_RO(invalid_io);
+ZRAM_ATTR_RO(notify_free);
+ZRAM_ATTR_RO(zero_pages);
+ZRAM_ATTR_RO(compr_data_size);
+
+static struct attribute *zram_disk_attrs[] = {
+	&dev_attr_disksize.attr,
+	&dev_attr_initstate.attr,
+	&dev_attr_reset.attr,
+	&dev_attr_num_reads.attr,
+	&dev_attr_num_writes.attr,
+	&dev_attr_failed_reads.attr,
+	&dev_attr_failed_writes.attr,
+	&dev_attr_compact.attr,
+	&dev_attr_invalid_io.attr,
+	&dev_attr_notify_free.attr,
+	&dev_attr_zero_pages.attr,
+	&dev_attr_orig_data_size.attr,
+	&dev_attr_compr_data_size.attr,
+	&dev_attr_mem_used_total.attr,
+	&dev_attr_mem_limit.attr,
+	&dev_attr_mem_used_max.attr,
+	&dev_attr_max_comp_streams.attr,
+	&dev_attr_comp_algorithm.attr,
+	&dev_attr_io_stat.attr,
+	&dev_attr_mm_stat.attr,
+	NULL,
+};
+
+static struct attribute_group zram_disk_attr_group = {
+	.attrs = zram_disk_attrs,
+};
+
+static int create_device(struct zram *zram, int device_id)
+{
+	struct request_queue *queue;
+	int ret = -ENOMEM;
+
+	init_rwsem(&zram->init_lock);
+
+	queue = blk_alloc_queue(GFP_KERNEL);
+	if (!queue) {
+		pr_err("Error allocating disk queue for device %d\n",
+			device_id);
+		goto out;
+	}
+
+	blk_queue_make_request(queue, zram_make_request);
+
+	 /* gendisk structure */
+	zram->disk = alloc_disk(1);
+	if (!zram->disk) {
+		pr_warn("Error allocating disk structure for device %d\n",
+			device_id);
+		ret = -ENOMEM;
+		goto out_free_queue;
+	}
+
+	zram->disk->major = zram_major;
+	zram->disk->first_minor = device_id;
+	zram->disk->fops = &zram_devops;
+	zram->disk->queue = queue;
+	zram->disk->queue->queuedata = zram;
+	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);
+	/* zram devices sort of resembles non-rotational disks */
+	queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
+	queue_flag_clear_unlocked(QUEUE_FLAG_ADD_RANDOM, zram->disk->queue);
+	/*
+	 * 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,
+					ZRAM_LOGICAL_BLOCK_SIZE);
+	blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
+	blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
+	zram->disk->queue->limits.discard_granularity = PAGE_SIZE;
+	zram->disk->queue->limits.max_discard_sectors = UINT_MAX;
+	/*
+	 * zram_bio_discard() will clear all logical blocks if logical block
+	 * size is identical with physical block size(PAGE_SIZE). But if it is
+	 * different, we will skip discarding some parts of logical blocks in
+	 * the part of the request range which isn't aligned to physical block
+	 * size.  So we can't ensure that all discarded logical blocks are
+	 * zeroed.
+	 */
+	if (ZRAM_LOGICAL_BLOCK_SIZE == PAGE_SIZE)
+		zram->disk->queue->limits.discard_zeroes_data = 1;
+	else
+		zram->disk->queue->limits.discard_zeroes_data = 0;
+	queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, zram->disk->queue);
+
+	add_disk(zram->disk);
+
+	ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
+				&zram_disk_attr_group);
+	if (ret < 0) {
+		pr_warn("Error creating sysfs group");
+		goto out_free_disk;
+	}
+	strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
+	zram->meta = NULL;
+	zram->max_comp_streams = 1;
+	return 0;
+
+out_free_disk:
+	del_gendisk(zram->disk);
+	put_disk(zram->disk);
+out_free_queue:
+	blk_cleanup_queue(queue);
+out:
+	return ret;
+}
+
+static void destroy_devices(unsigned int nr)
+{
+	struct zram *zram;
+	unsigned int i;
+
+	for (i = 0; i < nr; i++) {
+		zram = &zram_devices[i];
+		/*
+		 * Remove sysfs first, so no one will perform a disksize
+		 * store while we destroy the devices
+		 */
+		sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
+				&zram_disk_attr_group);
+
+		zram_reset_device(zram);
+
+		blk_cleanup_queue(zram->disk->queue);
+		del_gendisk(zram->disk);
+		put_disk(zram->disk);
+	}
+
+	kfree(zram_devices);
+	unregister_blkdev(zram_major, "zram");
+	pr_info("Destroyed %u device(s)\n", nr);
+}
+
+static int __init zram_init(void)
+{
+	int ret, dev_id;
+
+	if (num_devices > max_num_devices) {
+		pr_warn("Invalid value for num_devices: %u\n",
+				num_devices);
+		return -EINVAL;
+	}
+
+	zram_major = register_blkdev(0, "zram");
+	if (zram_major <= 0) {
+		pr_warn("Unable to get major number\n");
+		return -EBUSY;
+	}
+
+	/* Allocate the device array and initialize each one */
+	zram_devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
+	if (!zram_devices) {
+		unregister_blkdev(zram_major, "zram");
+		return -ENOMEM;
+	}
+
+	for (dev_id = 0; dev_id < num_devices; dev_id++) {
+		ret = create_device(&zram_devices[dev_id], dev_id);
+		if (ret)
+			goto out_error;
+	}
+
+	pr_info("Created %u device(s)\n", num_devices);
+	return 0;
+
+out_error:
+	destroy_devices(dev_id);
+	return ret;
+}
+
+static void __exit zram_exit(void)
+{
+	destroy_devices(num_devices);
+}
+
+module_init(zram_init);
+module_exit(zram_exit);
+
+module_param(num_devices, uint, 0);
+MODULE_PARM_DESC(num_devices, "Number of zram devices");
+
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
+MODULE_DESCRIPTION("Compressed RAM Block Device");