[linux.git] / drivers / md / dm-io.c

/*
 * 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 void *alloc_io(gfp_t gfp_mask, void *pool_data)
{
	return kmalloc(sizeof(struct io), gfp_mask);
}

static void free_io(void *element, void *pool_data)
{
	kfree(element);
}

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(new_ios, alloc_io, free_io, NULL);
		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);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Copyright (C) 2003 Sistina Software
	3	*
	4	* This file is released under the GPL.
	5	*/
	6
	7	#include "dm-io.h"
	8
	9	#include <linux/bio.h>
	10	#include <linux/mempool.h>
	11	#include <linux/module.h>
	12	#include <linux/sched.h>
	13	#include <linux/slab.h>
	14
	15	static struct bio_set *_bios;
	16
	17	/* FIXME: can we shrink this ? */
	18	struct io {
	19	unsigned long error;
	20	atomic_t count;
	21	struct task_struct *sleeper;
	22	io_notify_fn callback;
	23	void *context;
	24	};
	25
	26	/*
	27	* io contexts are only dynamically allocated for asynchronous
	28	* io. Since async io is likely to be the majority of io we'll
	29	* have the same number of io contexts as buffer heads ! (FIXME:
	30	* must reduce this).
	31	*/
	32	static unsigned _num_ios;
	33	static mempool_t *_io_pool;
	34
dd0fc66f	35	static void alloc_io(gfp_t gfp_mask, void pool_data)
1da177e4 LT	36	{
	37	return kmalloc(sizeof(struct io), gfp_mask);
	38	}
	39
	40	static void free_io(void element, void pool_data)
	41	{
	42	kfree(element);
	43	}
	44
	45	static unsigned int pages_to_ios(unsigned int pages)
	46	{
	47	return 4 * pages; /* too many ? */
	48	}
	49
	50	static int resize_pool(unsigned int new_ios)
	51	{
	52	int r = 0;
	53
	54	if (_io_pool) {
	55	if (new_ios == 0) {
	56	/* free off the pool */
	57	mempool_destroy(_io_pool);
	58	_io_pool = NULL;
	59	bioset_free(_bios);
	60
	61	} else {
	62	/* resize the pool */
	63	r = mempool_resize(_io_pool, new_ios, GFP_KERNEL);
	64	}
	65
	66	} else {
	67	/* create new pool */
	68	_io_pool = mempool_create(new_ios, alloc_io, free_io, NULL);
	69	if (!_io_pool)
	70	return -ENOMEM;
	71
	72	_bios = bioset_create(16, 16, 4);
	73	if (!_bios) {
	74	mempool_destroy(_io_pool);
	75	_io_pool = NULL;
	76	return -ENOMEM;
	77	}
	78	}
	79
	80	if (!r)
	81	_num_ios = new_ios;
	82
	83	return r;
	84	}
	85
	86	int dm_io_get(unsigned int num_pages)
	87	{
	88	return resize_pool(_num_ios + pages_to_ios(num_pages));
	89	}
	90
	91	void dm_io_put(unsigned int num_pages)
	92	{
	93	resize_pool(_num_ios - pages_to_ios(num_pages));
	94	}
	95
	96	/*-----------------------------------------------------------------
	97	* We need to keep track of which region a bio is doing io for.
	98	* In order to save a memory allocation we store this the last
	99	* bvec which we know is unused (blech).
100	* XXX This is ugly and can OOPS with some configs... find another way.
101	---------------------------------------------------------------/
102	static inline void bio_set_region(struct bio *bio, unsigned region)
103	{
104	bio->bi_io_vec[bio->bi_max_vecs - 1].bv_len = region;
105	}
106
107	static inline unsigned bio_get_region(struct bio *bio)
108	{
109	return bio->bi_io_vec[bio->bi_max_vecs - 1].bv_len;
110	}
111
112	/*-----------------------------------------------------------------
113	* We need an io object to keep track of the number of bios that
114	* have been dispatched for a particular io.
115	---------------------------------------------------------------/
116	static void dec_count(struct io *io, unsigned int region, int error)
117	{
118	if (error)
119	set_bit(region, &io->error);
120
121	if (atomic_dec_and_test(&io->count)) {
122	if (io->sleeper)
123	wake_up_process(io->sleeper);
124
125	else {
126	int r = io->error;
127	io_notify_fn fn = io->callback;
128	void *context = io->context;
129
130	mempool_free(io, _io_pool);
131	fn(r, context);
132	}
133	}
134	}
135
136	static int endio(struct bio *bio, unsigned int done, int error)
137	{
138	struct io io = (struct io ) bio->bi_private;
139
140	/* keep going until we've finished */
141	if (bio->bi_size)
142	return 1;
143
144	if (error && bio_data_dir(bio) == READ)
145	zero_fill_bio(bio);
146
147	dec_count(io, bio_get_region(bio), error);
148	bio_put(bio);
149
150	return 0;
151	}
152
153	/*-----------------------------------------------------------------
154	* These little objects provide an abstraction for getting a new
155	* destination page for io.
156	---------------------------------------------------------------/
157	struct dpages {
158	void (get_page)(struct dpages dp,
159	struct page *p, unsigned long len, unsigned *offset);
160	void (next_page)(struct dpages dp);
161
162	unsigned context_u;
163	void *context_ptr;
164	};
165
166	/*
167	* Functions for getting the pages from a list.
168	*/
169	static void list_get_page(struct dpages *dp,
170	struct page *p, unsigned long len, unsigned *offset)
171	{
172	unsigned o = dp->context_u;
173	struct page_list pl = (struct page_list ) dp->context_ptr;
174
175	*p = pl->page;
176	*len = PAGE_SIZE - o;
177	*offset = o;
178	}
179
180	static void list_next_page(struct dpages *dp)
181	{
182	struct page_list pl = (struct page_list ) dp->context_ptr;
183	dp->context_ptr = pl->next;
184	dp->context_u = 0;
185	}
186
187	static void list_dp_init(struct dpages dp, struct page_list pl, unsigned offset)
188	{
189	dp->get_page = list_get_page;
190	dp->next_page = list_next_page;
191	dp->context_u = offset;
192	dp->context_ptr = pl;
193	}
194
195	/*
196	* Functions for getting the pages from a bvec.
197	*/
198	static void bvec_get_page(struct dpages *dp,
199	struct page *p, unsigned long len, unsigned *offset)
200	{
201	struct bio_vec bvec = (struct bio_vec ) dp->context_ptr;
202	*p = bvec->bv_page;
203	*len = bvec->bv_len;
204	*offset = bvec->bv_offset;
205	}
206
207	static void bvec_next_page(struct dpages *dp)
208	{
209	struct bio_vec bvec = (struct bio_vec ) dp->context_ptr;
210	dp->context_ptr = bvec + 1;
211	}
212
213	static void bvec_dp_init(struct dpages dp, struct bio_vec bvec)
214	{
215	dp->get_page = bvec_get_page;
216	dp->next_page = bvec_next_page;
217	dp->context_ptr = bvec;
218	}
219
220	static void vm_get_page(struct dpages *dp,
221	struct page *p, unsigned long len, unsigned *offset)
222	{
223	*p = vmalloc_to_page(dp->context_ptr);
224	*offset = dp->context_u;
225	*len = PAGE_SIZE - dp->context_u;
226	}
227
228	static void vm_next_page(struct dpages *dp)
229	{
230	dp->context_ptr += PAGE_SIZE - dp->context_u;
231	dp->context_u = 0;
232	}
233
234	static void vm_dp_init(struct dpages dp, void data)
235	{
236	dp->get_page = vm_get_page;
237	dp->next_page = vm_next_page;
238	dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
239	dp->context_ptr = data;
240	}
241
3676347a PO	242	static void dm_bio_destructor(struct bio *bio)
	243	{
	244	bio_free(bio, _bios);
	245	}
	246
1da177e4 LT	247	/*-----------------------------------------------------------------
	248	* IO routines that accept a list of pages.
	249	---------------------------------------------------------------/
	250	static void do_region(int rw, unsigned int region, struct io_region *where,
	251	struct dpages dp, struct io io)
	252	{
	253	struct bio *bio;
	254	struct page *page;
	255	unsigned long len;
	256	unsigned offset;
	257	unsigned num_bvecs;
	258	sector_t remaining = where->count;
	259
	260	while (remaining) {
	261	/*
	262	* Allocate a suitably sized bio, we add an extra
	263	* bvec for bio_get/set_region().
	264	*/
	265	num_bvecs = (remaining / (PAGE_SIZE >> 9)) + 2;
	266	bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, _bios);
	267	bio->bi_sector = where->sector + (where->count - remaining);
	268	bio->bi_bdev = where->bdev;
	269	bio->bi_end_io = endio;
	270	bio->bi_private = io;
3676347a	271	bio->bi_destructor = dm_bio_destructor;
1da177e4 LT	272	bio_set_region(bio, region);
	273
	274	/*
	275	* Try and add as many pages as possible.
	276	*/
	277	while (remaining) {
	278	dp->get_page(dp, &page, &len, &offset);
	279	len = min(len, to_bytes(remaining));
	280	if (!bio_add_page(bio, page, len, offset))
	281	break;
	282
	283	offset = 0;
	284	remaining -= to_sector(len);
	285	dp->next_page(dp);
	286	}
	287
	288	atomic_inc(&io->count);
	289	submit_bio(rw, bio);
	290	}
	291	}
	292
	293	static void dispatch_io(int rw, unsigned int num_regions,
	294	struct io_region where, struct dpages dp,
	295	struct io *io, int sync)
	296	{
	297	int i;
	298	struct dpages old_pages = *dp;
	299
	300	if (sync)
	301	rw \|= (1 << BIO_RW_SYNC);
	302
	303	/*
	304	* For multiple regions we need to be careful to rewind
	305	* the dp object for each call to do_region.
	306	*/
	307	for (i = 0; i < num_regions; i++) {
	308	*dp = old_pages;
	309	if (where[i].count)
	310	do_region(rw, i, where + i, dp, io);
	311	}
	312
	313	/*
	314	* Drop the extra refence that we were holding to avoid
	315	* the io being completed too early.
	316	*/
	317	dec_count(io, 0, 0);
	318	}
	319
	320	static int sync_io(unsigned int num_regions, struct io_region *where,
	321	int rw, struct dpages dp, unsigned long error_bits)
	322	{
	323	struct io io;
	324
	325	if (num_regions > 1 && rw != WRITE) {
	326	WARN_ON(1);
	327	return -EIO;
	328	}
	329
	330	io.error = 0;
	331	atomic_set(&io.count, 1); /* see dispatch_io() */
	332	io.sleeper = current;
	333
	334	dispatch_io(rw, num_regions, where, dp, &io, 1);
	335
336	while (1) {
337	set_current_state(TASK_UNINTERRUPTIBLE);
338
339	if (!atomic_read(&io.count) \|\| signal_pending(current))
340	break;
341
342	io_schedule();
343	}
344	set_current_state(TASK_RUNNING);
345
346	if (atomic_read(&io.count))
347	return -EINTR;
348
349	*error_bits = io.error;
350	return io.error ? -EIO : 0;
351	}
352
353	static int async_io(unsigned int num_regions, struct io_region *where, int rw,
354	struct dpages dp, io_notify_fn fn, void context)
355	{
356	struct io *io;
357
358	if (num_regions > 1 && rw != WRITE) {
359	WARN_ON(1);
360	fn(1, context);
361	return -EIO;
362	}
363
364	io = mempool_alloc(_io_pool, GFP_NOIO);
365	io->error = 0;
366	atomic_set(&io->count, 1); /* see dispatch_io() */
367	io->sleeper = NULL;
368	io->callback = fn;
369	io->context = context;
370
371	dispatch_io(rw, num_regions, where, dp, io, 0);
372	return 0;
373	}
374
375	int dm_io_sync(unsigned int num_regions, struct io_region *where, int rw,
376	struct page_list *pl, unsigned int offset,
377	unsigned long *error_bits)
378	{
379	struct dpages dp;
380	list_dp_init(&dp, pl, offset);
381	return sync_io(num_regions, where, rw, &dp, error_bits);
382	}
383
384	int dm_io_sync_bvec(unsigned int num_regions, struct io_region *where, int rw,
385	struct bio_vec bvec, unsigned long error_bits)
386	{
387	struct dpages dp;
388	bvec_dp_init(&dp, bvec);
389	return sync_io(num_regions, where, rw, &dp, error_bits);
390	}
391
392	int dm_io_sync_vm(unsigned int num_regions, struct io_region *where, int rw,
393	void data, unsigned long error_bits)
394	{
395	struct dpages dp;
396	vm_dp_init(&dp, data);
397	return sync_io(num_regions, where, rw, &dp, error_bits);
398	}
399
400	int dm_io_async(unsigned int num_regions, struct io_region *where, int rw,
401	struct page_list *pl, unsigned int offset,
402	io_notify_fn fn, void *context)
403	{
404	struct dpages dp;
405	list_dp_init(&dp, pl, offset);
406	return async_io(num_regions, where, rw, &dp, fn, context);
407	}
408
409	int dm_io_async_bvec(unsigned int num_regions, struct io_region *where, int rw,
410	struct bio_vec bvec, io_notify_fn fn, void context)
411	{
412	struct dpages dp;
413	bvec_dp_init(&dp, bvec);
414	return async_io(num_regions, where, rw, &dp, fn, context);
415	}
416
417	int dm_io_async_vm(unsigned int num_regions, struct io_region *where, int rw,
418	void data, io_notify_fn fn, void context)
419	{
420	struct dpages dp;
421	vm_dp_init(&dp, data);
422	return async_io(num_regions, where, rw, &dp, fn, context);
423	}
424
425	EXPORT_SYMBOL(dm_io_get);
426	EXPORT_SYMBOL(dm_io_put);
427	EXPORT_SYMBOL(dm_io_sync);
428	EXPORT_SYMBOL(dm_io_async);
429	EXPORT_SYMBOL(dm_io_sync_bvec);
430	EXPORT_SYMBOL(dm_io_async_bvec);
431	EXPORT_SYMBOL(dm_io_sync_vm);
432	EXPORT_SYMBOL(dm_io_async_vm);