[mirror_ubuntu-zesty-kernel.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 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);
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
1da177e4 LT	35	static unsigned int pages_to_ios(unsigned int pages)
	36	{
	37	return 4 * pages; /* too many ? */
	38	}
	39
	40	static int resize_pool(unsigned int new_ios)
	41	{
	42	int r = 0;
	43
	44	if (_io_pool) {
	45	if (new_ios == 0) {
	46	/* free off the pool */
	47	mempool_destroy(_io_pool);
	48	_io_pool = NULL;
	49	bioset_free(_bios);
	50
	51	} else {
	52	/* resize the pool */
	53	r = mempool_resize(_io_pool, new_ios, GFP_KERNEL);
	54	}
	55
	56	} else {
	57	/* create new pool */
0eaae62a MD	58	_io_pool = mempool_create_kmalloc_pool(new_ios,
0eaae62a MD	59	sizeof(struct io));
1da177e4 LT	60	if (!_io_pool)
	61	return -ENOMEM;
	62
	63	_bios = bioset_create(16, 16, 4);
	64	if (!_bios) {
	65	mempool_destroy(_io_pool);
	66	_io_pool = NULL;
	67	return -ENOMEM;
	68	}
	69	}
	70
	71	if (!r)
	72	_num_ios = new_ios;
	73
	74	return r;
	75	}
	76
	77	int dm_io_get(unsigned int num_pages)
	78	{
	79	return resize_pool(_num_ios + pages_to_ios(num_pages));
	80	}
	81
	82	void dm_io_put(unsigned int num_pages)
	83	{
	84	resize_pool(_num_ios - pages_to_ios(num_pages));
	85	}
	86
	87	/*-----------------------------------------------------------------
	88	* We need to keep track of which region a bio is doing io for.
	89	* In order to save a memory allocation we store this the last
	90	* bvec which we know is unused (blech).
	91	* XXX This is ugly and can OOPS with some configs... find another way.
	92	---------------------------------------------------------------/
	93	static inline void bio_set_region(struct bio *bio, unsigned region)
	94	{
	95	bio->bi_io_vec[bio->bi_max_vecs - 1].bv_len = region;
	96	}
	97
	98	static inline unsigned bio_get_region(struct bio *bio)
	99	{
	100	return bio->bi_io_vec[bio->bi_max_vecs - 1].bv_len;
	101	}
	102
	103	/*-----------------------------------------------------------------
	104	* We need an io object to keep track of the number of bios that
	105	* have been dispatched for a particular io.
	106	---------------------------------------------------------------/
	107	static void dec_count(struct io *io, unsigned int region, int error)
	108	{
	109	if (error)
	110	set_bit(region, &io->error);
	111
	112	if (atomic_dec_and_test(&io->count)) {
	113	if (io->sleeper)
	114	wake_up_process(io->sleeper);
	115
	116	else {
	117	int r = io->error;
	118	io_notify_fn fn = io->callback;
	119	void *context = io->context;
	120
	121	mempool_free(io, _io_pool);
	122	fn(r, context);
	123	}
124	}
125	}
126
127	static int endio(struct bio *bio, unsigned int done, int error)
128	{
129	struct io io = (struct io ) bio->bi_private;
130
131	/* keep going until we've finished */
132	if (bio->bi_size)
133	return 1;
134
135	if (error && bio_data_dir(bio) == READ)
136	zero_fill_bio(bio);
137
138	dec_count(io, bio_get_region(bio), error);
139	bio_put(bio);
140
141	return 0;
142	}
143
144	/*-----------------------------------------------------------------
145	* These little objects provide an abstraction for getting a new
146	* destination page for io.
147	---------------------------------------------------------------/
148	struct dpages {
149	void (get_page)(struct dpages dp,
150	struct page *p, unsigned long len, unsigned *offset);
151	void (next_page)(struct dpages dp);
152
153	unsigned context_u;
154	void *context_ptr;
155	};
156
157	/*
158	* Functions for getting the pages from a list.
159	*/
160	static void list_get_page(struct dpages *dp,
161	struct page *p, unsigned long len, unsigned *offset)
162	{
163	unsigned o = dp->context_u;
164	struct page_list pl = (struct page_list ) dp->context_ptr;
165
166	*p = pl->page;
167	*len = PAGE_SIZE - o;
168	*offset = o;
169	}
170
171	static void list_next_page(struct dpages *dp)
172	{
173	struct page_list pl = (struct page_list ) dp->context_ptr;
174	dp->context_ptr = pl->next;
175	dp->context_u = 0;
176	}
177
178	static void list_dp_init(struct dpages dp, struct page_list pl, unsigned offset)
179	{
180	dp->get_page = list_get_page;
181	dp->next_page = list_next_page;
182	dp->context_u = offset;
183	dp->context_ptr = pl;
184	}
185
186	/*
187	* Functions for getting the pages from a bvec.
188	*/
189	static void bvec_get_page(struct dpages *dp,
190	struct page *p, unsigned long len, unsigned *offset)
191	{
192	struct bio_vec bvec = (struct bio_vec ) dp->context_ptr;
193	*p = bvec->bv_page;
194	*len = bvec->bv_len;
195	*offset = bvec->bv_offset;
196	}
197
198	static void bvec_next_page(struct dpages *dp)
199	{
200	struct bio_vec bvec = (struct bio_vec ) dp->context_ptr;
201	dp->context_ptr = bvec + 1;
202	}
203
204	static void bvec_dp_init(struct dpages dp, struct bio_vec bvec)
205	{
206	dp->get_page = bvec_get_page;
207	dp->next_page = bvec_next_page;
208	dp->context_ptr = bvec;
209	}
210
211	static void vm_get_page(struct dpages *dp,
212	struct page *p, unsigned long len, unsigned *offset)
213	{
214	*p = vmalloc_to_page(dp->context_ptr);
215	*offset = dp->context_u;
216	*len = PAGE_SIZE - dp->context_u;
217	}
218
219	static void vm_next_page(struct dpages *dp)
220	{
221	dp->context_ptr += PAGE_SIZE - dp->context_u;
222	dp->context_u = 0;
223	}
224
225	static void vm_dp_init(struct dpages dp, void data)
226	{
227	dp->get_page = vm_get_page;
228	dp->next_page = vm_next_page;
229	dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
230	dp->context_ptr = data;
231	}
232
3676347a PO	233	static void dm_bio_destructor(struct bio *bio)
	234	{
	235	bio_free(bio, _bios);
	236	}
	237
1da177e4 LT	238	/*-----------------------------------------------------------------
	239	* IO routines that accept a list of pages.
	240	---------------------------------------------------------------/
	241	static void do_region(int rw, unsigned int region, struct io_region *where,
	242	struct dpages dp, struct io io)
	243	{
	244	struct bio *bio;
	245	struct page *page;
	246	unsigned long len;
	247	unsigned offset;
	248	unsigned num_bvecs;
	249	sector_t remaining = where->count;
	250
	251	while (remaining) {
	252	/*
	253	* Allocate a suitably sized bio, we add an extra
	254	* bvec for bio_get/set_region().
	255	*/
	256	num_bvecs = (remaining / (PAGE_SIZE >> 9)) + 2;
	257	bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, _bios);
	258	bio->bi_sector = where->sector + (where->count - remaining);
	259	bio->bi_bdev = where->bdev;
	260	bio->bi_end_io = endio;
	261	bio->bi_private = io;
3676347a	262	bio->bi_destructor = dm_bio_destructor;
1da177e4 LT	263	bio_set_region(bio, region);
	264
	265	/*
	266	* Try and add as many pages as possible.
	267	*/
	268	while (remaining) {
	269	dp->get_page(dp, &page, &len, &offset);
	270	len = min(len, to_bytes(remaining));
	271	if (!bio_add_page(bio, page, len, offset))
	272	break;
	273
	274	offset = 0;
	275	remaining -= to_sector(len);
	276	dp->next_page(dp);
	277	}
	278
	279	atomic_inc(&io->count);
	280	submit_bio(rw, bio);
	281	}
	282	}
	283
	284	static void dispatch_io(int rw, unsigned int num_regions,
	285	struct io_region where, struct dpages dp,
	286	struct io *io, int sync)
	287	{
	288	int i;
	289	struct dpages old_pages = *dp;
	290
	291	if (sync)
	292	rw \|= (1 << BIO_RW_SYNC);
	293
	294	/*
	295	* For multiple regions we need to be careful to rewind
	296	* the dp object for each call to do_region.
	297	*/
	298	for (i = 0; i < num_regions; i++) {
	299	*dp = old_pages;
	300	if (where[i].count)
	301	do_region(rw, i, where + i, dp, io);
	302	}
	303
	304	/*
	305	* Drop the extra refence that we were holding to avoid
	306	* the io being completed too early.
	307	*/
	308	dec_count(io, 0, 0);
	309	}
	310
	311	static int sync_io(unsigned int num_regions, struct io_region *where,
	312	int rw, struct dpages dp, unsigned long error_bits)
	313	{
	314	struct io io;
	315
	316	if (num_regions > 1 && rw != WRITE) {
	317	WARN_ON(1);
	318	return -EIO;
	319	}
	320
	321	io.error = 0;
	322	atomic_set(&io.count, 1); /* see dispatch_io() */
	323	io.sleeper = current;
	324
	325	dispatch_io(rw, num_regions, where, dp, &io, 1);
	326
327	while (1) {
328	set_current_state(TASK_UNINTERRUPTIBLE);
329
330	if (!atomic_read(&io.count) \|\| signal_pending(current))
331	break;
332
333	io_schedule();
334	}
335	set_current_state(TASK_RUNNING);
336
337	if (atomic_read(&io.count))
338	return -EINTR;
339
340	*error_bits = io.error;
341	return io.error ? -EIO : 0;
342	}
343
344	static int async_io(unsigned int num_regions, struct io_region *where, int rw,
345	struct dpages dp, io_notify_fn fn, void context)
346	{
347	struct io *io;
348
349	if (num_regions > 1 && rw != WRITE) {
350	WARN_ON(1);
351	fn(1, context);
352	return -EIO;
353	}
354
355	io = mempool_alloc(_io_pool, GFP_NOIO);
356	io->error = 0;
357	atomic_set(&io->count, 1); /* see dispatch_io() */
358	io->sleeper = NULL;
359	io->callback = fn;
360	io->context = context;
361
362	dispatch_io(rw, num_regions, where, dp, io, 0);
363	return 0;
364	}
365
366	int dm_io_sync(unsigned int num_regions, struct io_region *where, int rw,
367	struct page_list *pl, unsigned int offset,
368	unsigned long *error_bits)
369	{
370	struct dpages dp;
371	list_dp_init(&dp, pl, offset);
372	return sync_io(num_regions, where, rw, &dp, error_bits);
373	}
374
375	int dm_io_sync_bvec(unsigned int num_regions, struct io_region *where, int rw,
376	struct bio_vec bvec, unsigned long error_bits)
377	{
378	struct dpages dp;
379	bvec_dp_init(&dp, bvec);
380	return sync_io(num_regions, where, rw, &dp, error_bits);
381	}
382
383	int dm_io_sync_vm(unsigned int num_regions, struct io_region *where, int rw,
384	void data, unsigned long error_bits)
385	{
386	struct dpages dp;
387	vm_dp_init(&dp, data);
388	return sync_io(num_regions, where, rw, &dp, error_bits);
389	}
390
391	int dm_io_async(unsigned int num_regions, struct io_region *where, int rw,
392	struct page_list *pl, unsigned int offset,
393	io_notify_fn fn, void *context)
394	{
395	struct dpages dp;
396	list_dp_init(&dp, pl, offset);
397	return async_io(num_regions, where, rw, &dp, fn, context);
398	}
399
400	int dm_io_async_bvec(unsigned int num_regions, struct io_region *where, int rw,
401	struct bio_vec bvec, io_notify_fn fn, void context)
402	{
403	struct dpages dp;
404	bvec_dp_init(&dp, bvec);
405	return async_io(num_regions, where, rw, &dp, fn, context);
406	}
407
408	int dm_io_async_vm(unsigned int num_regions, struct io_region *where, int rw,
409	void data, io_notify_fn fn, void context)
410	{
411	struct dpages dp;
412	vm_dp_init(&dp, data);
413	return async_io(num_regions, where, rw, &dp, fn, context);
414	}
415
416	EXPORT_SYMBOL(dm_io_get);
417	EXPORT_SYMBOL(dm_io_put);
418	EXPORT_SYMBOL(dm_io_sync);
419	EXPORT_SYMBOL(dm_io_async);
420	EXPORT_SYMBOL(dm_io_sync_bvec);
421	EXPORT_SYMBOL(dm_io_async_bvec);
422	EXPORT_SYMBOL(dm_io_sync_vm);
423	EXPORT_SYMBOL(dm_io_async_vm);