original development tree for Linux kernel GTP module; now long in mainline.
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/*
* fs/logfs/dev_bdev.c - Device access methods for block devices
*
* As should be obvious for Linux kernel code, license is GPLv2
*
* Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
*/
#include "logfs.h"
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/buffer_head.h>
#include <linux/gfp.h>
#include <linux/prefetch.h>
#define PAGE_OFS(ofs) ((ofs) & (PAGE_SIZE-1))
static int sync_request(struct page *page, struct block_device *bdev, int rw)
{
struct bio bio;
struct bio_vec bio_vec;
bio_init(&bio);
bio.bi_max_vecs = 1;
bio.bi_io_vec = &bio_vec;
bio_vec.bv_page = page;
bio_vec.bv_len = PAGE_SIZE;
bio_vec.bv_offset = 0;
bio.bi_vcnt = 1;
bio.bi_size = PAGE_SIZE;
bio.bi_bdev = bdev;
bio.bi_sector = page->index * (PAGE_SIZE >> 9);
return submit_bio_wait(rw, &bio);
}
static int bdev_readpage(void *_sb, struct page *page)
{
struct super_block *sb = _sb;
struct block_device *bdev = logfs_super(sb)->s_bdev;
int err;
err = sync_request(page, bdev, READ);
if (err) {
ClearPageUptodate(page);
SetPageError(page);
} else {
SetPageUptodate(page);
ClearPageError(page);
}
unlock_page(page);
return err;
}
static DECLARE_WAIT_QUEUE_HEAD(wq);
static void writeseg_end_io(struct bio *bio, int err)
{
const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
struct super_block *sb = bio->bi_private;
struct logfs_super *super = logfs_super(sb);
struct page *page;
BUG_ON(!uptodate); /* FIXME: Retry io or write elsewhere */
BUG_ON(err);
BUG_ON(bio->bi_vcnt == 0);
do {
page = bvec->bv_page;
if (--bvec >= bio->bi_io_vec)
prefetchw(&bvec->bv_page->flags);
end_page_writeback(page);
page_cache_release(page);
} while (bvec >= bio->bi_io_vec);
bio_put(bio);
if (atomic_dec_and_test(&super->s_pending_writes))
wake_up(&wq);
}
static int __bdev_writeseg(struct super_block *sb, u64 ofs, pgoff_t index,
size_t nr_pages)
{
struct logfs_super *super = logfs_super(sb);
struct address_space *mapping = super->s_mapping_inode->i_mapping;
struct bio *bio;
struct page *page;
unsigned int max_pages;
int i;
max_pages = min(nr_pages, (size_t) bio_get_nr_vecs(super->s_bdev));
bio = bio_alloc(GFP_NOFS, max_pages);
BUG_ON(!bio);
for (i = 0; i < nr_pages; i++) {
if (i >= max_pages) {
/* Block layer cannot split bios :( */
bio->bi_vcnt = i;
bio->bi_size = i * PAGE_SIZE;
bio->bi_bdev = super->s_bdev;
bio->bi_sector = ofs >> 9;
bio->bi_private = sb;
bio->bi_end_io = writeseg_end_io;
atomic_inc(&super->s_pending_writes);
submit_bio(WRITE, bio);
ofs += i * PAGE_SIZE;
index += i;
nr_pages -= i;
i = 0;
bio = bio_alloc(GFP_NOFS, max_pages);
BUG_ON(!bio);
}
page = find_lock_page(mapping, index + i);
BUG_ON(!page);
bio->bi_io_vec[i].bv_page = page;
bio->bi_io_vec[i].bv_len = PAGE_SIZE;
bio->bi_io_vec[i].bv_offset = 0;
BUG_ON(PageWriteback(page));
set_page_writeback(page);
unlock_page(page);
}
bio->bi_vcnt = nr_pages;
bio->bi_size = nr_pages * PAGE_SIZE;
bio->bi_bdev = super->s_bdev;
bio->bi_sector = ofs >> 9;
bio->bi_private = sb;
bio->bi_end_io = writeseg_end_io;
atomic_inc(&super->s_pending_writes);
submit_bio(WRITE, bio);
return 0;
}
static void bdev_writeseg(struct super_block *sb, u64 ofs, size_t len)
{
struct logfs_super *super = logfs_super(sb);
int head;
BUG_ON(super->s_flags & LOGFS_SB_FLAG_RO);
if (len == 0) {
/* This can happen when the object fit perfectly into a
* segment, the segment gets written per sync and subsequently
* closed.
*/
return;
}
head = ofs & (PAGE_SIZE - 1);
if (head) {
ofs -= head;
len += head;
}
len = PAGE_ALIGN(len);
__bdev_writeseg(sb, ofs, ofs >> PAGE_SHIFT, len >> PAGE_SHIFT);
}
static void erase_end_io(struct bio *bio, int err)
{
const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
struct super_block *sb = bio->bi_private;
struct logfs_super *super = logfs_super(sb);
BUG_ON(!uptodate); /* FIXME: Retry io or write elsewhere */
BUG_ON(err);
BUG_ON(bio->bi_vcnt == 0);
bio_put(bio);
if (atomic_dec_and_test(&super->s_pending_writes))
wake_up(&wq);
}
static int do_erase(struct super_block *sb, u64 ofs, pgoff_t index,
size_t nr_pages)
{
struct logfs_super *super = logfs_super(sb);
struct bio *bio;
unsigned int max_pages;
int i;
max_pages = min(nr_pages, (size_t) bio_get_nr_vecs(super->s_bdev));
bio = bio_alloc(GFP_NOFS, max_pages);
BUG_ON(!bio);
for (i = 0; i < nr_pages; i++) {
if (i >= max_pages) {
/* Block layer cannot split bios :( */
bio->bi_vcnt = i;
bio->bi_size = i * PAGE_SIZE;
bio->bi_bdev = super->s_bdev;
bio->bi_sector = ofs >> 9;
bio->bi_private = sb;
bio->bi_end_io = erase_end_io;
atomic_inc(&super->s_pending_writes);
submit_bio(WRITE, bio);
ofs += i * PAGE_SIZE;
index += i;
nr_pages -= i;
i = 0;
bio = bio_alloc(GFP_NOFS, max_pages);
BUG_ON(!bio);
}
bio->bi_io_vec[i].bv_page = super->s_erase_page;
bio->bi_io_vec[i].bv_len = PAGE_SIZE;
bio->bi_io_vec[i].bv_offset = 0;
}
bio->bi_vcnt = nr_pages;
bio->bi_size = nr_pages * PAGE_SIZE;
bio->bi_bdev = super->s_bdev;
bio->bi_sector = ofs >> 9;
bio->bi_private = sb;
bio->bi_end_io = erase_end_io;
atomic_inc(&super->s_pending_writes);
submit_bio(WRITE, bio);
return 0;
}
static int bdev_erase(struct super_block *sb, loff_t to, size_t len,
int ensure_write)
{
struct logfs_super *super = logfs_super(sb);
BUG_ON(to & (PAGE_SIZE - 1));
BUG_ON(len & (PAGE_SIZE - 1));
if (super->s_flags & LOGFS_SB_FLAG_RO)
return -EROFS;
if (ensure_write) {
/*
* Object store doesn't care whether erases happen or not.
* But for the journal they are required. Otherwise a scan
* can find an old commit entry and assume it is the current
* one, travelling back in time.
*/
do_erase(sb, to, to >> PAGE_SHIFT, len >> PAGE_SHIFT);
}
return 0;
}
static void bdev_sync(struct super_block *sb)
{
struct logfs_super *super = logfs_super(sb);
wait_event(wq, atomic_read(&super->s_pending_writes) == 0);
}
static struct page *bdev_find_first_sb(struct super_block *sb, u64 *ofs)
{
struct logfs_super *super = logfs_super(sb);
struct address_space *mapping = super->s_mapping_inode->i_mapping;
filler_t *filler = bdev_readpage;
*ofs = 0;
return read_cache_page(mapping, 0, filler, sb);
}
static struct page *bdev_find_last_sb(struct super_block *sb, u64 *ofs)
{
struct logfs_super *super = logfs_super(sb);
struct address_space *mapping = super->s_mapping_inode->i_mapping;
filler_t *filler = bdev_readpage;
u64 pos = (super->s_bdev->bd_inode->i_size & ~0xfffULL) - 0x1000;
pgoff_t index = pos >> PAGE_SHIFT;
*ofs = pos;
return read_cache_page(mapping, index, filler, sb);
}
static int bdev_write_sb(struct super_block *sb, struct page *page)
{
struct block_device *bdev = logfs_super(sb)->s_bdev;
/* Nothing special to do for block devices. */
return sync_request(page, bdev, WRITE);
}
static void bdev_put_device(struct logfs_super *s)
{
blkdev_put(s->s_bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
}
static int bdev_can_write_buf(struct super_block *sb, u64 ofs)
{
return 0;
}
static const struct logfs_device_ops bd_devops = {
.find_first_sb = bdev_find_first_sb,
.find_last_sb = bdev_find_last_sb,
.write_sb = bdev_write_sb,
.readpage = bdev_readpage,
.writeseg = bdev_writeseg,
.erase = bdev_erase,
.can_write_buf = bdev_can_write_buf,
.sync = bdev_sync,
.put_device = bdev_put_device,
};
int logfs_get_sb_bdev(struct logfs_super *p, struct file_system_type *type,
const char *devname)
{
struct block_device *bdev;
bdev = blkdev_get_by_path(devname, FMODE_READ|FMODE_WRITE|FMODE_EXCL,
type);
if (IS_ERR(bdev))
return PTR_ERR(bdev);
if (MAJOR(bdev->bd_dev) == MTD_BLOCK_MAJOR) {
int mtdnr = MINOR(bdev->bd_dev);
blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
return logfs_get_sb_mtd(p, mtdnr);
}
p->s_bdev = bdev;
p->s_mtd = NULL;
p->s_devops = &bd_devops;
return 0;
}