drivers/md/dm-io.c - maze/linux - Git at Google

 /*
  * Copyright (C) 2003 Sistina Software
  * Copyright (C) 2006 Red Hat GmbH
  *
  * 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;

 struct dm_io_client {
 	mempool_t *pool;
 	struct bio_set *bios;
 };

 /* FIXME: can we shrink this ? */
 struct io {
 	unsigned long error;
 	atomic_t count;
 	struct task_struct *sleeper;
 	struct dm_io_client *client;
 	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 bios! (FIXME: must reduce this).
  */
 static unsigned _num_ios;
 static mempool_t *_io_pool;

 /*
  * Temporary functions to allow old and new interfaces to co-exist.
  */
 static struct bio_set *bios(struct dm_io_client *client)
 {
 	return client ? client->bios : _bios;
 }

 static mempool_t *io_pool(struct dm_io_client *client)
 {
 	return client ? client->pool : _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);
 		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].bv_len = region;
 }

 static inline unsigned bio_get_region(struct bio *bio)
 {
 	return bio->bi_io_vec[bio->bi_max_vecs].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(io->client));
 			fn(r, context);
 		}
 	}
 }

 static int endio(struct bio *bio, unsigned int done, int error)
 {
 	struct io *io;
 	unsigned region;

 	/* keep going until we've finished */
 	if (bio->bi_size)
 		return 1;

 	if (error && bio_data_dir(bio) == READ)
 		zero_fill_bio(bio);

 	/*
 	 * The bio destructor in bio_put() may use the io object.
 	 */
 	io = bio->bi_private;
 	region = bio_get_region(bio);

 	bio->bi_max_vecs++;
 	bio_put(bio);

 	dec_count(io, region, error);

 	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)
 {
 	struct io *io = bio->bi_private;

 	bio_free(bio, bios(io->client));
 }

 /*-----------------------------------------------------------------
  * 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() and decrement bi_max_vecs
 		 * to hide it from bio_add_page().
 		 */
 		num_bvecs = (remaining / (PAGE_SIZE >> SECTOR_SHIFT)) + 2;
 		bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, bios(io->client));
 		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->bi_max_vecs--;
 		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 reference that we were holding to avoid
 	 * the io being completed too early.
 	 */
 	dec_count(io, 0, 0);
 }

 static int sync_io(struct dm_io_client *client, 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;
 	io.client = client;

 	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;

 	if (error_bits)
 		*error_bits = io.error;

 	return io.error ? -EIO : 0;
 }

 static int async_io(struct dm_io_client *client, 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(client), GFP_NOIO);
 	io->error = 0;
 	atomic_set(&io->count, 1); /* see dispatch_io() */
 	io->sleeper = NULL;
 	io->client = client;
 	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(NULL, 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(NULL, 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(NULL, 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(NULL, 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(NULL, 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(NULL, 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);
	/*
	* Copyright (C) 2003 Sistina Software
	* Copyright (C) 2006 Red Hat GmbH
	*
	* 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;

	struct dm_io_client {
	mempool_t *pool;
	struct bio_set *bios;
	};

	/* FIXME: can we shrink this ? */
	struct io {
	unsigned long error;
	atomic_t count;
	struct task_struct *sleeper;
	struct dm_io_client *client;
	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 bios! (FIXME: must reduce this).
	*/
	static unsigned _num_ios;
	static mempool_t *_io_pool;

	/*
	* Temporary functions to allow old and new interfaces to co-exist.
	*/
	static struct bio_set bios(struct dm_io_client client)
	{
	return client ? client->bios : _bios;
	}

	static mempool_t io_pool(struct dm_io_client client)
	{
	return client ? client->pool : _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);
	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].bv_len = region;
	}

	static inline unsigned bio_get_region(struct bio *bio)
	{
	return bio->bi_io_vec[bio->bi_max_vecs].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(io->client));
	fn(r, context);
	}
	}
	}

	static int endio(struct bio *bio, unsigned int done, int error)
	{
	struct io *io;
	unsigned region;

	/* keep going until we've finished */
	if (bio->bi_size)
	return 1;

	if (error && bio_data_dir(bio) == READ)
	zero_fill_bio(bio);

	/*
	* The bio destructor in bio_put() may use the io object.
	*/
	io = bio->bi_private;
	region = bio_get_region(bio);

	bio->bi_max_vecs++;
	bio_put(bio);

	dec_count(io, region, error);

	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)
	{
	struct io *io = bio->bi_private;

	bio_free(bio, bios(io->client));
	}

	/*-----------------------------------------------------------------
	* 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() and decrement bi_max_vecs
	* to hide it from bio_add_page().
	*/
	num_bvecs = (remaining / (PAGE_SIZE >> SECTOR_SHIFT)) + 2;
	bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, bios(io->client));
	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->bi_max_vecs--;
	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 reference that we were holding to avoid
	* the io being completed too early.
	*/
	dec_count(io, 0, 0);
	}

	static int sync_io(struct dm_io_client *client, 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;
	io.client = client;

	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;

	if (error_bits)
	*error_bits = io.error;

	return io.error ? -EIO : 0;
	}

	static int async_io(struct dm_io_client *client, 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(client), GFP_NOIO);
	io->error = 0;
	atomic_set(&io->count, 1); /* see dispatch_io() */
	io->sleeper = NULL;
	io->client = client;
	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(NULL, 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(NULL, 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(NULL, 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(NULL, 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(NULL, 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(NULL, 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);