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Subject[PATCH 3/4] virtual block device driver (ramzswap)
Date
Creates RAM based block devices (/dev/ramzswapX) which can be
used (only) as swap disks. Pages swapped to these are compressed
and stored in memory itself.

The module is called ramzswap.ko. It depends on:
- xvmalloc memory allocator (compiled with this driver)
- lzo_compress.ko
- lzo_decompress.ko

See ramzswap.txt for usage details.

Signed-off-by: Nitin Gupta <ngupta@vflare.org>

---
drivers/staging/Kconfig | 2 +
drivers/staging/Makefile | 1 +
drivers/staging/ramzswap/Kconfig | 21 +
drivers/staging/ramzswap/Makefile | 3 +
drivers/staging/ramzswap/ramzswap_drv.c | 1462 +++++++++++++++++++++++++++++
drivers/staging/ramzswap/ramzswap_drv.h | 173 ++++
drivers/staging/ramzswap/ramzswap_ioctl.h | 50 +
7 files changed, 1712 insertions(+), 0 deletions(-)
diff --git a/drivers/staging/Kconfig b/drivers/staging/Kconfig
index 10d3fcf..5cc55c4 100644
--- a/drivers/staging/Kconfig
+++ b/drivers/staging/Kconfig
@@ -131,5 +131,7 @@ source "drivers/staging/iio/Kconfig"

source "drivers/staging/cowloop/Kconfig"

+source "drivers/staging/ramzswap/Kconfig"
+
endif # !STAGING_EXCLUDE_BUILD
endif # STAGING
diff --git a/drivers/staging/Makefile b/drivers/staging/Makefile
index c30093b..dca5027 100644
--- a/drivers/staging/Makefile
+++ b/drivers/staging/Makefile
@@ -47,3 +47,4 @@ obj-$(CONFIG_RAR_REGISTER) += rar/
obj-$(CONFIG_DX_SEP) += sep/
obj-$(CONFIG_IIO) += iio/
obj-$(CONFIG_COWLOOP) += cowloop/
+obj-$(CONFIG_RAMZSWAP) += ramzswap/
diff --git a/drivers/staging/ramzswap/Kconfig b/drivers/staging/ramzswap/Kconfig
new file mode 100644
index 0000000..24e2569
--- /dev/null
+++ b/drivers/staging/ramzswap/Kconfig
@@ -0,0 +1,21 @@
+config RAMZSWAP
+ tristate "Compressed in-memory swap device (ramzswap)"
+ depends on SWAP
+ select LZO_COMPRESS
+ select LZO_DECOMPRESS
+ default n
+ help
+ Creates virtual block devices which can be used (only) as a swap
+ disks. Pages swapped to these disks are compressed and stored in
+ memory itself.
+
+ See ramzswap.txt for more information.
+ Project home: http://compcache.googlecode.com/
+
+config RAMZSWAP_STATS
+ bool "Enable ramzswap stats"
+ depends on RAMZSWAP
+ default y
+ help
+ Enable statistics collection for ramzswap. This adds only a minimal
+ overhead. In unsure, say Y.
diff --git a/drivers/staging/ramzswap/Makefile b/drivers/staging/ramzswap/Makefile
new file mode 100644
index 0000000..507d7dc
--- /dev/null
+++ b/drivers/staging/ramzswap/Makefile
@@ -0,0 +1,3 @@
+ramzswap-objs := ramzswap_drv.o xvmalloc.o
+
+obj-$(CONFIG_RAMZSWAP) += ramzswap.o
diff --git a/drivers/staging/ramzswap/ramzswap_drv.c b/drivers/staging/ramzswap/ramzswap_drv.c
new file mode 100644
index 0000000..46c387a
--- /dev/null
+++ b/drivers/staging/ramzswap/ramzswap_drv.c
@@ -0,0 +1,1462 @@
+/*
+ * Compressed RAM based swap device
+ *
+ * Copyright (C) 2008, 2009 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/lzo.h>
+#include <linux/mutex.h>
+#include <linux/string.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/vmalloc.h>
+#include <linux/version.h>
+
+#include "ramzswap_drv.h"
+
+/* Globals */
+static int ramzswap_major;
+static struct ramzswap *devices;
+
+/*
+ * Pages that compress to larger than this size are
+ * forwarded to backing swap, if present or stored
+ * uncompressed in memory otherwise.
+ */
+static unsigned int max_zpage_size;
+
+/* 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)
+{
+ u32 pos;
+ u64 *page;
+
+ page = (u64 *)ptr;
+
+ for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) {
+ if (page[pos])
+ return 0;
+ }
+
+ return 1;
+}
+
+/*
+ * memlimit cannot be greater than backing disk size.
+ */
+static void ramzswap_set_memlimit(struct ramzswap *rzs, size_t totalram_bytes)
+{
+ int memlimit_valid = 1;
+
+ if (!rzs->memlimit) {
+ pr_info("Memory limit not set.\n");
+ memlimit_valid = 0;
+ }
+
+ if (rzs->memlimit > rzs->disksize) {
+ pr_info("Memory limit cannot be greater than "
+ "disksize: limit=%zu, disksize=%zu\n",
+ rzs->memlimit, rzs->disksize);
+ memlimit_valid = 0;
+ }
+
+ if (!memlimit_valid) {
+ size_t mempart, disksize;
+ pr_info("Using default: smaller of (%u%% of RAM) and "
+ "(backing disk size).\n",
+ default_memlimit_perc_ram);
+ mempart = default_memlimit_perc_ram * (totalram_bytes / 100);
+ disksize = rzs->disksize;
+ rzs->memlimit = mempart > disksize ? disksize : mempart;
+ }
+
+ if (rzs->memlimit > totalram_bytes / 2) {
+ pr_info(
+ "Its not advisable setting limit more than half of "
+ "size of memory since we expect a 2:1 compression ratio. "
+ "Limit represents amount of *compressed* data we can keep "
+ "in memory!\n"
+ "\tMemory Size: %zu kB\n"
+ "\tLimit you selected: %zu kB\n"
+ "Continuing anyway ...\n",
+ totalram_bytes >> 10, rzs->memlimit >> 10
+ );
+ }
+
+ rzs->memlimit &= PAGE_MASK;
+ BUG_ON(!rzs->memlimit);
+}
+
+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
+ * to indentify it as a swap partition. Prepare such a header
+ * for ramzswap device (ramzswap0) so that swapon can identify
+ * it as swap partition. In case backing swap device is provided,
+ * copy its swap header.
+ */
+static int setup_swap_header(struct ramzswap *rzs, union swap_header *s)
+{
+ int ret = 0;
+ struct page *page;
+ struct address_space *mapping;
+ union swap_header *backing_swap_header;
+
+ /*
+ * There is no backing swap device. Create a swap header
+ * that is acceptable by swapon.
+ */
+ if (!rzs->backing_swap) {
+ s->info.version = 1;
+ s->info.last_page = (rzs->disksize >> PAGE_SHIFT) - 1;
+ s->info.nr_badpages = 0;
+ memcpy(s->magic.magic, "SWAPSPACE2", 10);
+ return 0;
+ }
+
+ /*
+ * We have a backing swap device. Copy its swap header
+ * to ramzswap device header. If this header contains
+ * invalid information (backing device not a swap
+ * partition, etc.), swapon will fail for ramzswap
+ * which is correct behavior - we don't want to swap
+ * over filesystem partition!
+ */
+
+ /* Read the backing swap header (code from sys_swapon) */
+ mapping = rzs->swap_file->f_mapping;
+ if (!mapping->a_ops->readpage) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ page = read_mapping_page(mapping, 0, rzs->swap_file);
+ if (IS_ERR(page)) {
+ ret = PTR_ERR(page);
+ goto out;
+ }
+
+ backing_swap_header = kmap(page);
+ memcpy(s, backing_swap_header, sizeof(*s));
+ if (s->info.nr_badpages) {
+ pr_info("Cannot use backing swap with bad pages (%u)\n",
+ s->info.nr_badpages);
+ ret = -EINVAL;
+ }
+ /*
+ * ramzswap disksize equals number of usable pages in backing
+ * swap. Set last_page in swap header to match this disksize
+ * ('last_page' means 0-based index of last usable swap page).
+ */
+ s->info.last_page = (rzs->disksize >> PAGE_SHIFT) - 1;
+ kunmap(page);
+
+out:
+ return ret;
+}
+
+static void ramzswap_flush_dcache_page(struct page *page)
+{
+#ifdef CONFIG_ARM
+ int flag = 0;
+ /*
+ * Ugly hack to get flush_dcache_page() work on ARM.
+ * page_mapping(page) == NULL after clearing this swap cache flag.
+ * Without clearing this flag, flush_dcache_page() will simply set
+ * "PG_dcache_dirty" bit and return.
+ */
+ if (PageSwapCache(page)) {
+ flag = 1;
+ ClearPageSwapCache(page);
+ }
+#endif
+ flush_dcache_page(page);
+#ifdef CONFIG_ARM
+ if (flag)
+ SetPageSwapCache(page);
+#endif
+}
+
+void ramzswap_ioctl_get_stats(struct ramzswap *rzs,
+ struct ramzswap_ioctl_stats *s)
+{
+ strncpy(s->backing_swap_name, rzs->backing_swap_name,
+ MAX_SWAP_NAME_LEN - 1);
+ s->backing_swap_name[MAX_SWAP_NAME_LEN - 1] = '\0';
+
+ s->disksize = rzs->disksize;
+ s->memlimit = rzs->memlimit;
+
+#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 = rs->num_writes - 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 = rs->num_reads;
+ s->num_writes = rs->num_writes;
+ s->failed_reads = rs->failed_reads;
+ s->failed_writes = rs->failed_writes;
+ s->invalid_io = rs->invalid_io;
+ s->notify_free = 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;
+
+ s->bdev_num_reads = rs->bdev_num_reads;
+ s->bdev_num_writes = rs->bdev_num_writes;
+ }
+#endif /* CONFIG_RAMZSWAP_STATS */
+}
+
+static int add_backing_swap_extent(struct ramzswap *rzs,
+ pgoff_t phy_pagenum,
+ pgoff_t num_pages)
+{
+ unsigned int idx;
+ struct list_head *head;
+ struct page *curr_page, *new_page;
+ unsigned int extents_per_page = PAGE_SIZE /
+ sizeof(struct ramzswap_backing_extent);
+
+ idx = rzs->num_extents % extents_per_page;
+ if (!idx) {
+ new_page = alloc_page(__GFP_ZERO);
+ if (!new_page)
+ return -ENOMEM;
+
+ if (rzs->num_extents) {
+ curr_page = virt_to_page(rzs->curr_extent);
+ head = &curr_page->lru;
+ } else {
+ head = &rzs->backing_swap_extent_list;
+ }
+
+ list_add(&new_page->lru, head);
+ rzs->curr_extent = page_address(new_page);
+ }
+
+ rzs->curr_extent->phy_pagenum = phy_pagenum;
+ rzs->curr_extent->num_pages = num_pages;
+
+ pr_debug("add_extent: idx=%u, phy_pgnum=%lu, num_pgs=%lu, "
+ "pg_last=%lu, curr_ext=%p\n", idx, phy_pagenum, num_pages,
+ phy_pagenum + num_pages - 1, rzs->curr_extent);
+
+ if (idx != extents_per_page - 1)
+ rzs->curr_extent++;
+
+ return 0;
+}
+
+static int setup_backing_swap_extents(struct ramzswap *rzs,
+ struct inode *inode, unsigned long *num_pages)
+{
+ int ret = 0;
+ unsigned blkbits;
+ unsigned blocks_per_page;
+ pgoff_t contig_pages = 0, total_pages = 0;
+ pgoff_t pagenum = 0, prev_pagenum = 0;
+ sector_t probe_block = 0;
+ sector_t last_block;
+
+ blkbits = inode->i_blkbits;
+ blocks_per_page = PAGE_SIZE >> blkbits;
+
+ last_block = i_size_read(inode) >> blkbits;
+ while (probe_block + blocks_per_page <= last_block) {
+ unsigned block_in_page;
+ sector_t first_block;
+
+ first_block = bmap(inode, probe_block);
+ if (first_block == 0)
+ goto bad_bmap;
+
+ /* It must be PAGE_SIZE aligned on-disk */
+ if (first_block & (blocks_per_page - 1)) {
+ probe_block++;
+ goto probe_next;
+ }
+
+ /* All blocks within this page must be contiguous on disk */
+ for (block_in_page = 1; block_in_page < blocks_per_page;
+ block_in_page++) {
+ sector_t block;
+
+ block = bmap(inode, probe_block + block_in_page);
+ if (block == 0)
+ goto bad_bmap;
+ if (block != first_block + block_in_page) {
+ /* Discontiguity */
+ probe_block++;
+ goto probe_next;
+ }
+ }
+
+ /*
+ * We found a PAGE_SIZE length, PAGE_SIZE aligned
+ * run of blocks.
+ */
+ pagenum = first_block >> (PAGE_SHIFT - blkbits);
+
+ if (total_pages && (pagenum != prev_pagenum + 1)) {
+ ret = add_backing_swap_extent(rzs, prev_pagenum -
+ (contig_pages - 1), contig_pages);
+ if (ret < 0)
+ goto out;
+ rzs->num_extents++;
+ contig_pages = 0;
+ }
+ total_pages++;
+ contig_pages++;
+ prev_pagenum = pagenum;
+ probe_block += blocks_per_page;
+
+probe_next:
+ continue;
+ }
+
+ if (contig_pages) {
+ pr_debug("adding last extent: pagenum=%lu, "
+ "contig_pages=%lu\n", pagenum, contig_pages);
+ ret = add_backing_swap_extent(rzs,
+ prev_pagenum - (contig_pages - 1), contig_pages);
+ if (ret < 0)
+ goto out;
+ rzs->num_extents++;
+ }
+ if (!rzs->num_extents) {
+ pr_err("No swap extents found!\n");
+ ret = -EINVAL;
+ }
+
+ if (!ret) {
+ *num_pages = total_pages;
+ pr_info("Found %lu extents containing %luk\n",
+ rzs->num_extents, *num_pages << (PAGE_SHIFT - 10));
+ }
+ goto out;
+
+bad_bmap:
+ pr_err("Backing swapfile has holes\n");
+ ret = -EINVAL;
+out:
+ while (ret && !list_empty(&rzs->backing_swap_extent_list)) {
+ struct page *page;
+ struct list_head *entry = rzs->backing_swap_extent_list.next;
+ page = list_entry(entry, struct page, lru);
+ list_del(entry);
+ __free_page(page);
+ }
+ return ret;
+}
+
+static void map_backing_swap_extents(struct ramzswap *rzs)
+{
+ struct ramzswap_backing_extent *se;
+ struct page *table_page, *se_page;
+ unsigned long num_pages, num_table_pages, entry;
+ unsigned long se_idx, span;
+ unsigned entries_per_page = PAGE_SIZE / sizeof(*rzs->table);
+ unsigned extents_per_page = PAGE_SIZE / sizeof(*se);
+
+ /* True for block device */
+ if (!rzs->num_extents)
+ return;
+
+ se_page = list_entry(rzs->backing_swap_extent_list.next,
+ struct page, lru);
+ se = page_address(se_page);
+ span = se->num_pages;
+ num_pages = rzs->disksize >> PAGE_SHIFT;
+ num_table_pages = DIV_ROUND_UP(num_pages * sizeof(*rzs->table),
+ PAGE_SIZE);
+
+ entry = 0;
+ se_idx = 0;
+ while (num_table_pages--) {
+ table_page = vmalloc_to_page(&rzs->table[entry]);
+ while (span <= entry) {
+ se_idx++;
+ if (se_idx == rzs->num_extents)
+ BUG();
+
+ if (!(se_idx % extents_per_page)) {
+ se_page = list_entry(se_page->lru.next,
+ struct page, lru);
+ se = page_address(se_page);
+ } else
+ se++;
+
+ span += se->num_pages;
+ }
+ table_page->mapping = (struct address_space *)se;
+ table_page->private = se->num_pages - (span - entry);
+ pr_debug("map_table: entry=%lu, span=%lu, map=%p, priv=%lu\n",
+ entry, span, table_page->mapping, table_page->private);
+ entry += entries_per_page;
+ }
+}
+
+/*
+ * Check if value of backing_swap module param is sane.
+ * Claim this device and set ramzswap size equal to
+ * size of this block device.
+ */
+static int setup_backing_swap(struct ramzswap *rzs)
+{
+ int ret = 0;
+ size_t disksize;
+ unsigned long num_pages = 0;
+ struct inode *inode;
+ struct file *swap_file;
+ struct address_space *mapping;
+ struct block_device *bdev = NULL;
+
+ if (!rzs->backing_swap_name[0]) {
+ pr_debug("backing_swap param not given\n");
+ goto out;
+ }
+
+ pr_info("Using backing swap device: %s\n", rzs->backing_swap_name);
+
+ swap_file = filp_open(rzs->backing_swap_name,
+ O_RDWR | O_LARGEFILE, 0);
+ if (IS_ERR(swap_file)) {
+ pr_err("Error opening backing device: %s\n",
+ rzs->backing_swap_name);
+ ret = -EINVAL;
+ goto out;
+ }
+
+ mapping = swap_file->f_mapping;
+ inode = mapping->host;
+
+ if (S_ISBLK(inode->i_mode)) {
+ bdev = I_BDEV(inode);
+ ret = bd_claim(bdev, setup_backing_swap);
+ if (ret < 0) {
+ bdev = NULL;
+ goto bad_param;
+ }
+ disksize = i_size_read(inode);
+ } else if (S_ISREG(inode->i_mode)) {
+ bdev = inode->i_sb->s_bdev;
+ if (IS_SWAPFILE(inode)) {
+ ret = -EBUSY;
+ goto bad_param;
+ }
+ ret = setup_backing_swap_extents(rzs, inode, &num_pages);
+ if (ret < 0)
+ goto bad_param;
+ disksize = num_pages << PAGE_SHIFT;
+ } else {
+ goto bad_param;
+ }
+
+ rzs->swap_file = swap_file;
+ rzs->backing_swap = bdev;
+ rzs->disksize = disksize;
+ BUG_ON(!rzs->disksize);
+
+ return 0;
+
+bad_param:
+ if (bdev)
+ bd_release(bdev);
+ filp_close(swap_file, NULL);
+
+out:
+ rzs->backing_swap = NULL;
+ return ret;
+}
+
+/*
+ * Map logical page number 'pagenum' to physical page number
+ * on backing swap device. For block device, this is a nop.
+ */
+u32 map_backing_swap_page(struct ramzswap *rzs, u32 pagenum)
+{
+ u32 skip_pages, entries_per_page;
+ size_t delta, se_offset, skipped;
+ struct page *table_page, *se_page;
+ struct ramzswap_backing_extent *se;
+
+ if (!rzs->num_extents)
+ return pagenum;
+
+ entries_per_page = PAGE_SIZE / sizeof(*rzs->table);
+
+ table_page = vmalloc_to_page(&rzs->table[pagenum]);
+ se = (struct ramzswap_backing_extent *)table_page->mapping;
+ se_page = virt_to_page(se);
+
+ skip_pages = pagenum - (pagenum / entries_per_page * entries_per_page);
+ se_offset = table_page->private + skip_pages;
+
+ if (se_offset < se->num_pages)
+ return se->phy_pagenum + se_offset;
+
+ skipped = se->num_pages - table_page->private;
+ do {
+ struct ramzswap_backing_extent *se_base;
+ u32 se_entries_per_page = PAGE_SIZE / sizeof(*se);
+
+ /* Get next swap extent */
+ se_base = (struct ramzswap_backing_extent *)
+ page_address(se_page);
+ if (se - se_base == se_entries_per_page - 1) {
+ se_page = list_entry(se_page->lru.next,
+ struct page, lru);
+ se = page_address(se_page);
+ } else {
+ se++;
+ }
+
+ skipped += se->num_pages;
+ } while (skipped < skip_pages);
+
+ delta = skipped - skip_pages;
+ se_offset = se->num_pages - delta;
+
+ return se->phy_pagenum + se_offset;
+}
+
+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)) {
+ if (rzs_test_flag(rzs, index, RZS_ZERO)) {
+ rzs_clear_flag(rzs, index, RZS_ZERO);
+ 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);
+ 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)
+ stat_dec(rzs->stats.good_compress);
+
+out:
+ rzs->stats.compr_size -= clen;
+ stat_dec(rzs->stats.pages_stored);
+
+ rzs->table[index].page = NULL;
+ rzs->table[index].offset = 0;
+}
+
+/*
+ * callback function called when swap_map[offset] == 0
+ * i.e page at this swap offset is no longer used
+ */
+static void ramzswap_free_notify(struct block_device *bdev,
+ unsigned long index)
+{
+ struct ramzswap *rzs = bdev->bd_disk->private_data;
+
+ ramzswap_free_page(rzs, index);
+ stat_inc(rzs->stats.notify_free);
+}
+
+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);
+
+ ramzswap_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);
+
+ ramzswap_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.
+ * Its either in backing swap device (if present) or
+ * 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)
+{
+ /*
+ * Always forward such requests to backing swap
+ * device (if present)
+ */
+ if (rzs->backing_swap) {
+ u32 pagenum;
+ stat_dec(rzs->stats.num_reads);
+ stat_inc(rzs->stats.bdev_num_reads);
+ bio->bi_bdev = rzs->backing_swap;
+
+ /*
+ * In case backing swap is a file, find the right offset within
+ * the file corresponding to logical position 'index'. For block
+ * device, this is a nop.
+ */
+ pagenum = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
+ bio->bi_sector = map_backing_swap_page(rzs, pagenum)
+ << SECTORS_PER_PAGE_SHIFT;
+ return 1;
+ }
+
+ /*
+ * Its unlikely event in case backing dev is
+ * not present
+ */
+ 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;
+
+ stat_inc(rzs->stats.num_reads);
+
+ page = bio->bi_io_vec[0].bv_page;
+ index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
+
+ if (unlikely(!rzs->init_notify_callback) && PageSwapCache(page)) {
+ set_swap_free_notify(bio->bi_bdev, ramzswap_free_notify);
+ rzs->init_notify_callback = 1;
+ }
+
+ 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 its 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);
+ stat_inc(rzs->stats.failed_reads);
+ goto out;
+ }
+
+ ramzswap_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, fwd_write_request = 0;
+ u32 offset, index;
+ size_t clen;
+ struct zobj_header *zheader;
+ struct page *page, *page_store;
+ unsigned char *user_mem, *cmem, *src;
+
+ stat_inc(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)
+ ramzswap_free_page(rzs, index);
+
+ /*
+ * No memory ia allocated for zero filled pages.
+ * Simply clear zero page flag.
+ */
+ if (rzs_test_flag(rzs, index, RZS_ZERO)) {
+ stat_dec(rzs->stats.pages_zero);
+ rzs_clear_flag(rzs, index, RZS_ZERO);
+ }
+
+ 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);
+ 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;
+ }
+
+ if (rzs->backing_swap &&
+ (rzs->stats.compr_size > rzs->memlimit - PAGE_SIZE)) {
+ kunmap_atomic(user_mem, KM_USER0);
+ mutex_unlock(&rzs->lock);
+ fwd_write_request = 1;
+ goto out;
+ }
+
+ 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);
+ stat_inc(rzs->stats.failed_writes);
+ goto out;
+ }
+
+ /*
+ * Page is incompressible. Forward it to backing swap
+ * if present. Otherwise, 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)) {
+ if (rzs->backing_swap) {
+ mutex_unlock(&rzs->lock);
+ fwd_write_request = 1;
+ goto out;
+ }
+
+ 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);
+ stat_inc(rzs->stats.failed_writes);
+ goto out;
+ }
+
+ offset = 0;
+ rzs_set_flag(rzs, index, RZS_UNCOMPRESSED);
+ 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);
+ stat_inc(rzs->stats.failed_writes);
+ if (rzs->backing_swap)
+ fwd_write_request = 1;
+ 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;
+ stat_inc(rzs->stats.pages_stored);
+ if (clen <= PAGE_SIZE / 2)
+ stat_inc(rzs->stats.good_compress);
+
+ mutex_unlock(&rzs->lock);
+
+ set_bit(BIO_UPTODATE, &bio->bi_flags);
+ bio_endio(bio, 0);
+ return 0;
+
+out:
+ if (fwd_write_request) {
+ stat_inc(rzs->stats.bdev_num_writes);
+ bio->bi_bdev = rzs->backing_swap;
+#if 0
+ /*
+ * TODO: We currently have linear mapping of ramzswap and
+ * backing swap sectors. This is not desired since we want
+ * to optimize writes to backing swap to minimize disk seeks
+ * or have effective wear leveling (for SSDs). Also, a
+ * non-linear mapping is required to implement compressed
+ * on-disk swapping.
+ */
+ bio->bi_sector = get_backing_swap_page()
+ << SECTORS_PER_PAGE_SHIFT;
+#endif
+ /*
+ * In case backing swap is a file, find the right offset within
+ * the file corresponding to logical position 'index'. For block
+ * device, this is a nop.
+ */
+ bio->bi_sector = map_backing_swap_page(rzs, index)
+ << SECTORS_PER_PAGE_SHIFT;
+ return 1;
+ }
+
+ 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)) {
+ stat_inc(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)
+{
+ int is_backing_blkdev = 0;
+ size_t index, num_pages;
+ unsigned entries_per_page;
+ unsigned long num_table_pages, entry = 0;
+
+ if (rzs->backing_swap && !rzs->num_extents)
+ is_backing_blkdev = 1;
+
+ num_pages = rzs->disksize >> PAGE_SHIFT;
+
+ /* 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 < num_pages; 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);
+ }
+
+ entries_per_page = PAGE_SIZE / sizeof(*rzs->table);
+ num_table_pages = DIV_ROUND_UP(num_pages * sizeof(*rzs->table),
+ PAGE_SIZE);
+ /*
+ * Set page->mapping to NULL for every table page.
+ * Otherwise, we will hit bad_page() during free.
+ */
+ while (rzs->num_extents && num_table_pages--) {
+ struct page *page;
+ page = vmalloc_to_page(&rzs->table[entry]);
+ page->mapping = NULL;
+ entry += entries_per_page;
+ }
+ vfree(rzs->table);
+ rzs->table = NULL;
+
+ xv_destroy_pool(rzs->mem_pool);
+ rzs->mem_pool = NULL;
+
+ /* Free all swap extent pages */
+ while (!list_empty(&rzs->backing_swap_extent_list)) {
+ struct page *page;
+ struct list_head *entry;
+ entry = rzs->backing_swap_extent_list.next;
+ page = list_entry(entry, struct page, lru);
+ list_del(entry);
+ __free_page(page);
+ }
+ INIT_LIST_HEAD(&rzs->backing_swap_extent_list);
+ rzs->num_extents = 0;
+
+ /* Close backing swap device, if present */
+ if (rzs->backing_swap) {
+ if (is_backing_blkdev)
+ bd_release(rzs->backing_swap);
+ filp_close(rzs->swap_file, NULL);
+ rzs->backing_swap = NULL;
+ }
+
+ /* Reset stats */
+ memset(&rzs->stats, 0, sizeof(rzs->stats));
+
+ rzs->disksize = 0;
+ rzs->memlimit = 0;
+
+ /* Back to uninitialized state */
+ rzs->init_done = 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;
+ }
+
+ ret = setup_backing_swap(rzs);
+ if (ret)
+ goto fail;
+
+ if (rzs->backing_swap)
+ ramzswap_set_memlimit(rzs, totalram_pages << PAGE_SHIFT);
+ else
+ 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));
+
+ map_backing_swap_extents(rzs);
+
+ 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);
+ ret = setup_swap_header(rzs, swap_header);
+ kunmap(page);
+ if (ret) {
+ pr_err("Error setting swap header\n");
+ goto fail;
+ }
+
+ set_capacity(rzs->disk, rzs->disksize >> SECTOR_SHIFT);
+
+ /*
+ * We have ident mapping of sectors for ramzswap and
+ * and the backing swap device. So, this queue flag
+ * should be according to backing dev.
+ */
+ if (!rzs->backing_swap ||
+ blk_queue_nonrot(rzs->backing_swap->bd_disk->queue))
+ 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;
+ }
+
+ /*
+ * Pages that compress to size greater than this are forwarded
+ * to physical swap disk (if backing dev is provided)
+ * TODO: make this configurable
+ */
+ if (rzs->backing_swap)
+ max_zpage_size = max_zpage_size_bdev;
+ else
+ max_zpage_size = max_zpage_size_nobdev;
+ pr_debug("Max compressed page size: %u bytes\n", max_zpage_size);
+
+ 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, memlimit_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_SET_MEMLIMIT_KB:
+ if (rzs->init_done) {
+ /* TODO: allow changing memlimit */
+ ret = -EBUSY;
+ goto out;
+ }
+ if (copy_from_user(&memlimit_kb, (void *)arg,
+ _IOC_SIZE(cmd))) {
+ ret = -EFAULT;
+ goto out;
+ }
+ rzs->memlimit = memlimit_kb << 10;
+ pr_info("Memory limit set to %zu kB\n", memlimit_kb);
+ break;
+
+ case RZSIO_SET_BACKING_SWAP:
+ if (rzs->init_done) {
+ ret = -EBUSY;
+ goto out;
+ }
+
+ if (copy_from_user(&rzs->backing_swap_name, (void *)arg,
+ _IOC_SIZE(cmd))) {
+ ret = -EFAULT;
+ goto out;
+ }
+ rzs->backing_swap_name[MAX_SWAP_NAME_LEN - 1] = '\0';
+ pr_info("Backing swap set to %s\n", rzs->backing_swap_name);
+ 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;
+ }
+ ret = ramzswap_ioctl_reset_device(rzs);
+ /*
+ * Racy! Device has already been swapoff'ed. Bad things
+ * can happen if another swapon is done before this reset.
+ * TODO: A callback from swapoff() will solve this problem.
+ */
+ set_swap_free_notify(bdev, NULL);
+ rzs->init_notify_callback = 0;
+ 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 void create_device(struct ramzswap *rzs, int device_id)
+{
+ mutex_init(&rzs->lock);
+ INIT_LIST_HEAD(&rzs->backing_swap_extent_list);
+
+ rzs->queue = blk_alloc_queue(GFP_KERNEL);
+ if (!rzs->queue) {
+ pr_err("Error allocating disk queue for device %d\n",
+ device_id);
+ return;
+ }
+
+ 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);
+ return;
+ }
+
+ 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
+ * or set equal to backing swap device (if provided)
+ */
+ set_capacity(rzs->disk, 0);
+ add_disk(rzs->disk);
+
+ rzs->init_done = 0;
+
+ return;
+}
+
+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 i;
+
+ if (num_devices > max_num_devices) {
+ pr_warning("Invalid value for num_devices: %u\n",
+ num_devices);
+ return -EINVAL;
+ }
+
+ ramzswap_major = register_blkdev(0, "ramzswap");
+ if (ramzswap_major <= 0) {
+ pr_warning("Unable to get major number\n");
+ return -EBUSY;
+ }
+
+ 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)
+ goto out;
+
+ for (i = 0; i < num_devices; i++)
+ create_device(&devices[i], i);
+
+ return 0;
+
+out:
+ unregister_blkdev(ramzswap_major, "ramzswap");
+ return -ENOMEM;
+}
+
+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");
diff --git a/drivers/staging/ramzswap/ramzswap_drv.h b/drivers/staging/ramzswap/ramzswap_drv.h
new file mode 100644
index 0000000..f7f273f
--- /dev/null
+++ b/drivers/staging/ramzswap/ramzswap_drv.h
@@ -0,0 +1,173 @@
+/*
+ * Compressed RAM based swap device
+ *
+ * Copyright (C) 2008, 2009 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
+ */
+
+#ifndef _RAMZSWAP_DRV_H_
+#define _RAMZSWAP_DRV_H_
+
+#include "ramzswap_ioctl.h"
+#include "xvmalloc.h"
+
+/*
+ * Some arbitrary value. This is just to catch
+ * invalid value for num_devices module parameter.
+ */
+static const unsigned max_num_devices = 32;
+
+/*
+ * Stored at beginning of each compressed object.
+ *
+ * It stores back-reference to table entry which points to this
+ * object. This is required to support memory defragmentation or
+ * migrating compressed pages to backing swap disk.
+ */
+struct zobj_header {
+#if 0
+ u32 table_idx;
+#endif
+};
+
+/*-- Configurable parameters */
+
+/* Default ramzswap disk size: 25% of total RAM */
+static const unsigned default_disksize_perc_ram = 25;
+static const unsigned default_memlimit_perc_ram = 15;
+
+/*
+ * Max compressed page size when backing device is provided.
+ * Pages that compress to size greater than this are sent to
+ * physical swap disk.
+ */
+static const unsigned max_zpage_size_bdev = PAGE_SIZE / 2;
+
+/*
+ * Max compressed page size when there is no backing dev.
+ * Pages that compress to size greater than this are stored
+ * uncompressed in memory.
+ */
+static const unsigned max_zpage_size_nobdev = PAGE_SIZE / 4 * 3;
+
+/*
+ * NOTE: max_zpage_size_{bdev,nobdev} sizes must be
+ * less than or equal to:
+ * XV_MAX_ALLOC_SIZE - sizeof(struct zobj_header)
+ * since otherwise xv_malloc would always return failure.
+ */
+
+/*-- End of configurable params */
+
+#define SECTOR_SHIFT 9
+#define SECTOR_SIZE (1 << SECTOR_SHIFT)
+#define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT)
+#define SECTORS_PER_PAGE (1 << SECTORS_PER_PAGE_SHIFT)
+
+/* Debugging and Stats */
+#if defined(CONFIG_RAMZSWAP_STATS)
+#define stat_inc(stat) ((stat)++)
+#define stat_dec(stat) ((stat)--)
+#else
+#define stat_inc(x)
+#define stat_dec(x)
+#endif
+
+/* Flags for ramzswap pages (table[page_no].flags) */
+enum rzs_pageflags {
+ /* Page is stored uncompressed */
+ RZS_UNCOMPRESSED,
+
+ /* Page consists entirely of zeros */
+ RZS_ZERO,
+
+ __NR_RZS_PAGEFLAGS,
+};
+
+/*-- Data structures */
+
+/*
+ * Allocated for each swap slot, indexed by page no.
+ * These table entries must fit exactly in a page.
+ */
+struct table {
+ struct page *page;
+ u16 offset;
+ u8 count; /* object ref count (not yet used) */
+ u8 flags;
+} __attribute__((aligned(4)));;
+
+/*
+ * Swap extent information in case backing swap is a regular
+ * file. These extent entries must fit exactly in a page.
+ */
+struct ramzswap_backing_extent {
+ pgoff_t phy_pagenum;
+ pgoff_t num_pages;
+} __attribute__((aligned(4)));
+
+struct ramzswap_stats {
+ /* basic stats */
+ size_t compr_size; /* compressed size of pages stored -
+ * needed to enforce memlimit */
+ /* more stats */
+#if defined(CONFIG_RAMZSWAP_STATS)
+ u64 num_reads; /* failed + successful */
+ u64 num_writes; /* --do-- */
+ u64 failed_reads; /* can happen when memory is too low */
+ u64 failed_writes; /* should NEVER! happen */
+ u64 invalid_io; /* non-swap I/O requests */
+ u64 notify_free; /* no. of pages freed by swap free callback */
+ u32 pages_zero; /* no. of zero filled pages */
+ u32 pages_stored; /* no. of pages currently stored */
+ u32 good_compress; /* % of pages with compression ratio<=50% */
+ u32 pages_expand; /* % of incompressible pages */
+ u64 bdev_num_reads; /* no. of reads on backing dev */
+ u64 bdev_num_writes; /* no. of writes on backing dev */
+#endif
+};
+
+struct ramzswap {
+ struct xv_pool *mem_pool;
+ void *compress_workmem;
+ void *compress_buffer;
+ struct table *table;
+ struct mutex lock;
+ struct request_queue *queue;
+ struct gendisk *disk;
+ int init_done;
+ int init_notify_callback;
+ /*
+ * This is limit on compressed data size (stats.compr_size)
+ * Its applicable only when backing swap device is present.
+ */
+ size_t memlimit; /* bytes */
+ /*
+ * This is limit on amount of *uncompressed* worth of data
+ * we can hold. When backing swap device is provided, it is
+ * set equal to device size.
+ */
+ size_t disksize; /* bytes */
+
+ struct ramzswap_stats stats;
+
+ /* backing swap device info */
+ struct ramzswap_backing_extent *curr_extent;
+ struct list_head backing_swap_extent_list;
+ unsigned long num_extents;
+ char backing_swap_name[MAX_SWAP_NAME_LEN];
+ struct block_device *backing_swap;
+ struct file *swap_file;
+};
+
+/*-- */
+
+#endif
+
diff --git a/drivers/staging/ramzswap/ramzswap_ioctl.h b/drivers/staging/ramzswap/ramzswap_ioctl.h
new file mode 100644
index 0000000..a7ce039
--- /dev/null
+++ b/drivers/staging/ramzswap/ramzswap_ioctl.h
@@ -0,0 +1,50 @@
+/*
+ * Compressed RAM based swap device
+ *
+ * Copyright (C) 2008, 2009 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
+ */
+
+#ifndef _RAMZSWAP_IOCTL_H_
+#define _RAMZSWAP_IOCTL_H_
+
+#define MAX_SWAP_NAME_LEN 128
+
+struct ramzswap_ioctl_stats {
+ char backing_swap_name[MAX_SWAP_NAME_LEN];
+ u64 memlimit; /* only applicable if backing swap present */
+ u64 disksize; /* user specified or equal to backing swap
+ * size (if present) */
+ u64 num_reads; /* failed + successful */
+ u64 num_writes; /* --do-- */
+ u64 failed_reads; /* can happen when memory is too low */
+ u64 failed_writes; /* should NEVER! happen */
+ u64 invalid_io; /* non-swap I/O requests */
+ u64 notify_free; /* no. of pages freed by swap free callback */
+ u32 pages_zero; /* no. of zero filled pages */
+ u32 good_compress_pct; /* no. of pages with compression ratio<=50% */
+ u32 pages_expand_pct; /* no. of incompressible pages */
+ u32 pages_stored;
+ u32 pages_used;
+ u64 orig_data_size;
+ u64 compr_data_size;
+ u64 mem_used_total;
+ u64 bdev_num_reads; /* no. of reads on backing dev */
+ u64 bdev_num_writes; /* no. of writes on backing dev */
+} __attribute__ ((packed, aligned(4)));
+
+#define RZSIO_SET_DISKSIZE_KB _IOW('z', 0, size_t)
+#define RZSIO_SET_MEMLIMIT_KB _IOW('z', 1, size_t)
+#define RZSIO_SET_BACKING_SWAP _IOW('z', 2, unsigned char[MAX_SWAP_NAME_LEN])
+#define RZSIO_GET_STATS _IOR('z', 3, struct ramzswap_ioctl_stats)
+#define RZSIO_INIT _IO('z', 4)
+#define RZSIO_RESET _IO('z', 5)
+
+#endif

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