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|
/*
* 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/string.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/vmalloc.h>
#include "ramzswap_drv.h"
/* Globals */
static int ramzswap_major;
static struct ramzswap *devices;
/*
* 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)
{
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;
}
/*
* 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;
}
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 = 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;
s->bdev_num_reads = rzs_stat64_read(rzs, &rs->bdev_num_reads);
s->bdev_num_writes = rzs_stat64_read(rzs, &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)) {
/*
* No memory is allocated for zero filled pages.
* Simply clear zero page flag.
*/
if (rzs_test_flag(rzs, index, RZS_ZERO)) {
rzs_clear_flag(rzs, index, RZS_ZERO);
rzs_stat_dec(&rzs->stats.pages_zero);
}
return;
}
if (unlikely(rzs_test_flag(rzs, index, RZS_UNCOMPRESSED))) {
clen = PAGE_SIZE;
__free_page(page);
rzs_clear_flag(rzs, index, RZS_UNCOMPRESSED);
rzs_stat_dec(&rzs->stats.pages_expand);
goto out;
}
obj = kmap_atomic(page, KM_USER0) + offset;
clen = xv_get_object_size(obj) - sizeof(struct zobj_header);
kunmap_atomic(obj, KM_USER0);
xv_free(rzs->mem_pool, page, offset);
if (clen <= PAGE_SIZE / 2)
rzs_stat_dec(&rzs->stats.good_compress);
out:
rzs->stats.compr_size -= clen;
rzs_stat_dec(&rzs->stats.pages_stored);
rzs->table[index].page = NULL;
rzs->table[index].offset = 0;
}
static int handle_zero_page(struct bio *bio)
{
void *user_mem;
struct page *page = bio->bi_io_vec[0].bv_page;
user_mem = kmap_atomic(page, KM_USER0);
memset(user_mem, 0, PAGE_SIZE);
kunmap_atomic(user_mem, KM_USER0);
flush_dcache_page(page);
set_bit(BIO_UPTODATE, &bio->bi_flags);
bio_endio(bio, 0);
return 0;
}
static int handle_uncompressed_page(struct ramzswap *rzs, struct bio *bio)
{
u32 index;
struct page *page;
unsigned char *user_mem, *cmem;
page = bio->bi_io_vec[0].bv_page;
index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
user_mem = kmap_atomic(page, KM_USER0);
cmem = kmap_atomic(rzs->table[index].page, KM_USER1) +
rzs->table[index].offset;
memcpy(user_mem, cmem, PAGE_SIZE);
kunmap_atomic(user_mem, KM_USER0);
kunmap_atomic(cmem, KM_USER1);
flush_dcache_page(page);
set_bit(BIO_UPTODATE, &bio->bi_flags);
bio_endio(bio, 0);
return 0;
}
/*
* Called when request page is not present in ramzswap.
* 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;
rzs_stat64_dec(rzs, &rzs->stats.num_reads);
rzs_stat64_inc(rzs, &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;
rzs_stat64_inc(rzs, &rzs->stats.num_reads);
page = bio->bi_io_vec[0].bv_page;
index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
if (rzs_test_flag(rzs, index, RZS_ZERO))
return handle_zero_page(bio);
/* Requested page is not present in compressed area */
if (!rzs->table[index].page)
return handle_ramzswap_fault(rzs, bio);
/* Page is stored uncompressed since it's incompressible */
if (unlikely(rzs_test_flag(rzs, index, RZS_UNCOMPRESSED)))
return handle_uncompressed_page(rzs, bio);
user_mem = kmap_atomic(page, KM_USER0);
clen = PAGE_SIZE;
cmem = kmap_atomic(rzs->table[index].page, KM_USER1) +
rzs->table[index].offset;
ret = lzo1x_decompress_safe(
cmem + sizeof(*zheader),
xv_get_object_size(cmem) - sizeof(*zheader),
user_mem, &clen);
kunmap_atomic(user_mem, KM_USER0);
kunmap_atomic(cmem, KM_USER1);
/* should NEVER happen */
if (unlikely(ret != LZO_E_OK)) {
pr_err("Decompression failed! err=%d, page=%u\n",
ret, index);
rzs_stat64_inc(rzs, &rzs->stats.failed_reads);
goto out;
}
flush_dcache_page(page);
set_bit(BIO_UPTODATE, &bio->bi_flags);
bio_endio(bio, 0);
return 0;
out:
bio_io_error(bio);
return 0;
}
static int ramzswap_write(struct ramzswap *rzs, struct bio *bio)
{
int ret, 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;
rzs_stat64_inc(rzs, &rzs->stats.num_writes);
page = bio->bi_io_vec[0].bv_page;
index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
src = rzs->compress_buffer;
/*
* System swaps to same sector again when the stored page
* is no longer referenced by any process. So, its now safe
* to free the memory that was allocated for this page.
*/
if (rzs->table[index].page || rzs_test_flag(rzs, index, RZS_ZERO))
ramzswap_free_page(rzs, index);
mutex_lock(&rzs->lock);
user_mem = kmap_atomic(page, KM_USER0);
if (page_zero_filled(user_mem)) {
kunmap_atomic(user_mem, KM_USER0);
mutex_unlock(&rzs->lock);
rzs_stat_inc(&rzs->stats.pages_zero);
rzs_set_flag(rzs, index, RZS_ZERO);
set_bit(BIO_UPTODATE, &bio->bi_flags);
bio_endio(bio, 0);
return 0;
}
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);
rzs_stat64_inc(rzs, &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);
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);
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;
rzs_stat_inc(&rzs->stats.pages_stored);
if (clen <= PAGE_SIZE / 2)
rzs_stat_inc(&rzs->stats.good_compress);
mutex_unlock(&rzs->lock);
set_bit(BIO_UPTODATE, &bio->bi_flags);
bio_endio(bio, 0);
return 0;
out:
if (fwd_write_request) {
rzs_stat64_inc(rzs, &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)) {
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)
{
int is_backing_blkdev = 0;
size_t index, num_pages;
unsigned entries_per_page;
unsigned long num_table_pages, entry = 0;
/* Do not accept any new I/O request */
rzs->init_done = 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;
}
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;
}
/* Make sure all pending I/O is finished */
if (bdev)
fsync_bdev(bdev);
ret = ramzswap_ioctl_reset_device(rzs);
break;
default:
pr_info("Invalid ioctl %u\n", cmd);
ret = -ENOTTY;
}
out:
return ret;
}
static struct block_device_operations ramzswap_devops = {
.ioctl = ramzswap_ioctl,
.owner = THIS_MODULE,
};
static int create_device(struct ramzswap *rzs, int device_id)
{
int ret = 0;
mutex_init(&rzs->lock);
spin_lock_init(&rzs->stat64_lock);
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);
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
* or set equal to backing swap device (if provided)
*/
set_capacity(rzs->disk, 0);
blk_queue_physical_block_size(rzs->disk->queue, PAGE_SIZE);
blk_queue_logical_block_size(rzs->disk->queue, PAGE_SIZE);
add_disk(rzs->disk);
rzs->init_done = 0;
out:
return ret;
}
static void destroy_device(struct ramzswap *rzs)
{
if (rzs->disk) {
del_gendisk(rzs->disk);
put_disk(rzs->disk);
}
if (rzs->queue)
blk_cleanup_queue(rzs->queue);
}
static int __init ramzswap_init(void)
{
int ret, dev_id;
if (num_devices > max_num_devices) {
pr_warning("Invalid value for num_devices: %u\n",
num_devices);
ret = -EINVAL;
goto out;
}
ramzswap_major = register_blkdev(0, "ramzswap");
if (ramzswap_major <= 0) {
pr_warning("Unable to get major number\n");
ret = -EBUSY;
goto out;
}
if (!num_devices) {
pr_info("num_devices not specified. Using default: 1\n");
num_devices = 1;
}
/* Allocate the device array and initialize each one */
pr_info("Creating %u devices ...\n", num_devices);
devices = kzalloc(num_devices * sizeof(struct ramzswap), GFP_KERNEL);
if (!devices) {
ret = -ENOMEM;
goto unregister;
}
for (dev_id = 0; dev_id < num_devices; dev_id++) {
ret = create_device(&devices[dev_id], dev_id);
if (ret)
goto free_devices;
}
return 0;
free_devices:
while (dev_id)
destroy_device(&devices[--dev_id]);
unregister:
unregister_blkdev(ramzswap_major, "ramzswap");
out:
return ret;
}
static void __exit ramzswap_exit(void)
{
int i;
struct ramzswap *rzs;
for (i = 0; i < num_devices; i++) {
rzs = &devices[i];
destroy_device(rzs);
if (rzs->init_done)
reset_device(rzs);
}
unregister_blkdev(ramzswap_major, "ramzswap");
kfree(devices);
pr_debug("Cleanup done!\n");
}
module_param(num_devices, uint, 0);
MODULE_PARM_DESC(num_devices, "Number of ramzswap devices");
module_init(ramzswap_init);
module_exit(ramzswap_exit);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
MODULE_DESCRIPTION("Compressed RAM Based Swap Device");
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