/*
* Copyright (C) 2003 Sistina Software
*
* This file is released under the GPL.
*/
#include "dm-io.h"
#include <linux/bio.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
static struct bio_set *_bios;
/* FIXME: can we shrink this ? */
struct io {
unsigned long error;
atomic_t count;
struct task_struct *sleeper;
io_notify_fn callback;
void *context;
};
/*
* io contexts are only dynamically allocated for asynchronous
* io. Since async io is likely to be the majority of io we'll
* have the same number of io contexts as buffer heads ! (FIXME:
* must reduce this).
*/
static unsigned _num_ios;
static mempool_t *_io_pool;
static unsigned int pages_to_ios(unsigned int pages)
{
return 4 * pages; /* too many ? */
}
static int resize_pool(unsigned int new_ios)
{
int r = 0;
if (_io_pool) {
if (new_ios == 0) {
/* free off the pool */
mempool_destroy(_io_pool);
_io_pool = NULL;
bioset_free(_bios);
} else {
/* resize the pool */
r = mempool_resize(_io_pool, new_ios, GFP_KERNEL);
}
} else {
/* create new pool */
_io_pool = mempool_create_kmalloc_pool(new_ios,
sizeof(struct io));
if (!_io_pool)
return -ENOMEM;
_bios = bioset_create(16, 16, 4);
if (!_bios) {
mempool_destroy(_io_pool);
_io_pool = NULL;
return -ENOMEM;
}
}
if (!r)
_num_ios = new_ios;
return r;
}
int dm_io_get(unsigned int num_pages)
{
return resize_pool(_num_ios + pages_to_ios(num_pages));
}
void dm_io_put(unsigned int num_pages)
{
resize_pool(_num_ios - pages_to_ios(num_pages));
}
/*-----------------------------------------------------------------
* We need to keep track of which region a bio is doing io for.
* In order to save a memory allocation we store this the last
* bvec which we know is unused (blech).
* XXX This is ugly and can OOPS with some configs... find another way.
*---------------------------------------------------------------*/
static inline void bio_set_region(struct bio *bio, unsigned region)
{
bio->bi_io_vec[bio->bi_max_vecs - 1].bv_len = region;
}
static inline unsigned bio_get_region(struct bio *bio)
{
return bio->bi_io_vec[bio->bi_max_vecs - 1].bv_len;
}
/*-----------------------------------------------------------------
* We need an io object to keep track of the number of bios that
* have been dispatched for a particular io.
*---------------------------------------------------------------*/
static void dec_count(struct io *io, unsigned int region, int error)
{
if (error)
set_bit(region, &io->error);
if (atomic_dec_and_test(&io->count)) {
if (io->sleeper)
wake_up_process(io->sleeper);
else {
int r = io->error;
io_notify_fn fn = io->callback;
void *context = io->context;
mempool_free(io, _io_pool);
fn(r, context);
}
}
}
static int endio(struct bio *bio, unsigned int done, int error)
{
struct io *io = (struct io *) bio->bi_private;
/* keep going until we've finished */
if (bio->bi_size)
return 1;
if (error && bio_data_dir(bio) == READ)
zero_fill_bio(bio);
dec_count(io, bio_get_region(bio), error);
bio_put(bio);
return 0;
}
/*-----------------------------------------------------------------
* These little objects provide an abstraction for getting a new
* destination page for io.
*---------------------------------------------------------------*/
struct dpages {
void (*get_page)(struct dpages *dp,
struct page **p, unsigned long *len, unsigned *offset);
void (*next_page)(struct dpages *dp);
unsigned context_u;
void *context_ptr;
};
/*
* Functions for getting the pages from a list.
*/
static void list_get_page(struct dpages *dp,
struct page **p, unsigned long *len, unsigned *offset)
{
unsigned o = dp->context_u;
struct page_list *pl = (struct page_list *) dp->context_ptr;
*p = pl->page;
*len = PAGE_SIZE - o;
*offset = o;
}
static void list_next_page(struct dpages *dp)
{
struct page_list *pl = (struct page_list *) dp->context_ptr;
dp->context_ptr = pl->next;
dp->context_u = 0;
}
static void list_dp_init(struct dpages *dp, struct page_list *pl, unsigned offset)
{
dp->get_page = list_get_page;
dp->next_page = list_next_page;
dp->context_u = offset;
dp->context_ptr = pl;
}
/*
* Functions for getting the pages from a bvec.
*/
static void bvec_get_page(struct dpages *dp,
struct page **p, unsigned long *len, unsigned *offset)
{
struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
*p = bvec->bv_page;
*len = bvec->bv_len;
*offset = bvec->bv_offset;
}
static void bvec_next_page(struct dpages *dp)
{
struct bio_vec *bvec = (struct bio_vec *) dp->context_ptr;
dp->context_ptr = bvec + 1;
}
static void bvec_dp_init(struct dpages *dp, struct bio_vec *bvec)
{
dp->get_page = bvec_get_page;
dp->next_page = bvec_next_page;
dp->context_ptr = bvec;
}
static void vm_get_page(struct dpages *dp,
struct page **p, unsigned long *len, unsigned *offset)
{
*p = vmalloc_to_page(dp->context_ptr);
*offset = dp->context_u;
*len = PAGE_SIZE - dp->context_u;
}
static void vm_next_page(struct dpages *dp)
{
dp->context_ptr += PAGE_SIZE - dp->context_u;
dp->context_u = 0;
}
static void vm_dp_init(struct dpages *dp, void *data)
{
dp->get_page = vm_get_page;
dp->next_page = vm_next_page;
dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
dp->context_ptr = data;
}
static void dm_bio_destructor(struct bio *bio)
{
bio_free(bio, _bios);
}
/*-----------------------------------------------------------------
* IO routines that accept a list of pages.
*---------------------------------------------------------------*/
static void do_region(int rw, unsigned int region, struct io_region *where,
struct dpages *dp, struct io *io)
{
struct bio *bio;
struct page *page;
unsigned long len;
unsigned offset;
unsigned num_bvecs;
sector_t remaining = where->count;
while (remaining) {
/*
* Allocate a suitably sized bio, we add an extra
* bvec for bio_get/set_region().
*/
num_bvecs = (remaining / (PAGE_SIZE >> 9)) + 2;
bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, _bios);
bio->bi_sector = where->sector + (where->count - remaining);
bio->bi_bdev = where->bdev;
bio->bi_end_io = endio;
bio->bi_private = io;
bio->bi_destructor = dm_bio_destructor;
bio_set_region(bio, region);
/*
* Try and add as many pages as possible.
*/
while (remaining) {
dp->get_page(dp, &page, &len, &offset);
len = min(len, to_bytes(remaining));
if (!bio_add_page(bio, page, len, offset))
break;
offset = 0;
remaining -= to_sector(len);
dp->next_page(dp);
}
atomic_inc(&io->count);
submit_bio(rw, bio);
}
}
static void dispatch_io(int rw, unsigned int num_regions,
struct io_region *where, struct dpages *dp,
struct io *io, int sync)
{
int i;
struct dpages old_pages = *dp;
if (sync)
rw |= (1 << BIO_RW_SYNC);
/*
* For multiple regions we need to be careful to rewind
* the dp object for each call to do_region.
*/
for (i = 0; i < num_regions; i++) {
*dp = old_pages;
if (where[i].count)
do_region(rw, i, where + i, dp, io);
}
/*
* Drop the extra refence that we were holding to avoid
* the io being completed too early.
*/
dec_count(io, 0, 0);
}
static int sync_io(unsigned int num_regions, struct io_region *where,
int rw, struct dpages *dp, unsigned long *error_bits)
{
struct io io;
if (num_regions > 1 && rw != WRITE) {
WARN_ON(1);
return -EIO;
}
io.error = 0;
atomic_set(&io.count, 1); /* see dispatch_io() */
io.sleeper = current;
dispatch_io(rw, num_regions, where, dp, &io, 1);
while (1) {
set_current_state(TASK_UNINTERRUPTIBLE);
if (!atomic_read(&io.count) || signal_pending(current))
break;
io_schedule();
}
set_current_state(TASK_RUNNING);
if (atomic_read(&io.count))
return -EINTR;
*error_bits = io.error;
return io.error ? -EIO : 0;
}
static int async_io(unsigned int num_regions, struct io_region *where, int rw,
struct dpages *dp, io_notify_fn fn, void *context)
{
struct io *io;
if (num_regions > 1 && rw != WRITE) {
WARN_ON(1);
fn(1, context);
return -EIO;
}
io = mempool_alloc(_io_pool, GFP_NOIO);
io->error = 0;
atomic_set(&io->count, 1); /* see dispatch_io() */
io->sleeper = NULL;
io->callback = fn;
io->context = context;
dispatch_io(rw, num_regions, where, dp, io, 0);
return 0;
}
int dm_io_sync(unsigned int num_regions, struct io_region *where, int rw,
struct page_list *pl, unsigned int offset,
unsigned long *error_bits)
{
struct dpages dp;
list_dp_init(&dp, pl, offset);
return sync_io(num_regions, where, rw, &dp, error_bits);
}
int dm_io_sync_bvec(unsigned int num_regions, struct io_region *where, int rw,
struct bio_vec *bvec, unsigned long *error_bits)
{
struct dpages dp;
bvec_dp_init(&dp, bvec);
return sync_io(num_regions, where, rw, &dp, error_bits);
}
int dm_io_sync_vm(unsigned int num_regions, struct io_region *where, int rw,
void *data, unsigned long *error_bits)
{
struct dpages dp;
vm_dp_init(&dp, data);
return sync_io(num_regions, where, rw, &dp, error_bits);
}
int dm_io_async(unsigned int num_regions, struct io_region *where, int rw,
struct page_list *pl, unsigned int offset,
io_notify_fn fn, void *context)
{
struct dpages dp;
list_dp_init(&dp, pl, offset);
return async_io(num_regions, where, rw, &dp, fn, context);
}
int dm_io_async_bvec(unsigned int num_regions, struct io_region *where, int rw,
struct bio_vec *bvec, io_notify_fn fn, void *context)
{
struct dpages dp;
bvec_dp_init(&dp, bvec);
return async_io(num_regions, where, rw, &dp, fn, context);
}
int dm_io_async_vm(unsigned int num_regions, struct io_region *where, int rw,
void *data, io_notify_fn fn, void *context)
{
struct dpages dp;
vm_dp_init(&dp, data);
return async_io(num_regions, where, rw, &dp, fn, context);
}
EXPORT_SYMBOL(dm_io_get);
EXPORT_SYMBOL(dm_io_put);
EXPORT_SYMBOL(dm_io_sync);
EXPORT_SYMBOL(dm_io_async);
EXPORT_SYMBOL(dm_io_sync_bvec);
EXPORT_SYMBOL(dm_io_async_bvec);
EXPORT_SYMBOL(dm_io_sync_vm);
EXPORT_SYMBOL(dm_io_async_vm);
