[net-next-2.6.git] / drivers / md / dm-io.c

/*
 * Copyright (C) 2003 Sistina Software
 * Copyright (C) 2006 Red Hat GmbH
 *
 * This file is released under the GPL.
 */

#include "dm.h"

#include <linux/device-mapper.h>

#include <linux/bio.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/dm-io.h>

#define DM_MSG_PREFIX "io"

#define DM_IO_MAX_REGIONS	BITS_PER_LONG

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

/*
 * Aligning 'struct io' reduces the number of bits required to store
 * its address.  Refer to store_io_and_region_in_bio() below.
 */
struct io {
	unsigned long error_bits;
	unsigned long eopnotsupp_bits;
	atomic_t count;
	struct task_struct *sleeper;
	struct dm_io_client *client;
	io_notify_fn callback;
	void *context;
} __attribute__((aligned(DM_IO_MAX_REGIONS)));

static struct kmem_cache *_dm_io_cache;

/*
 * 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 int pages_to_ios(unsigned int pages)
{
	return 4 * pages;	/* too many ? */
}

/*
 * Create a client with mempool and bioset.
 */
struct dm_io_client *dm_io_client_create(unsigned num_pages)
{
	unsigned ios = pages_to_ios(num_pages);
	struct dm_io_client *client;

	client = kmalloc(sizeof(*client), GFP_KERNEL);
	if (!client)
		return ERR_PTR(-ENOMEM);

	client->pool = mempool_create_slab_pool(ios, _dm_io_cache);
	if (!client->pool)
		goto bad;

	client->bios = bioset_create(16, 0);
	if (!client->bios)
		goto bad;

	return client;

   bad:
	if (client->pool)
		mempool_destroy(client->pool);
	kfree(client);
	return ERR_PTR(-ENOMEM);
}
EXPORT_SYMBOL(dm_io_client_create);

int dm_io_client_resize(unsigned num_pages, struct dm_io_client *client)
{
	return mempool_resize(client->pool, pages_to_ios(num_pages),
			      GFP_KERNEL);
}
EXPORT_SYMBOL(dm_io_client_resize);

void dm_io_client_destroy(struct dm_io_client *client)
{
	mempool_destroy(client->pool);
	bioset_free(client->bios);
	kfree(client);
}
EXPORT_SYMBOL(dm_io_client_destroy);

/*-----------------------------------------------------------------
 * We need to keep track of which region a bio is doing io for.
 * To avoid a memory allocation to store just 5 or 6 bits, we
 * ensure the 'struct io' pointer is aligned so enough low bits are
 * always zero and then combine it with the region number directly in
 * bi_private.
 *---------------------------------------------------------------*/
static void store_io_and_region_in_bio(struct bio *bio, struct io *io,
				       unsigned region)
{
	if (unlikely(!IS_ALIGNED((unsigned long)io, DM_IO_MAX_REGIONS))) {
		DMCRIT("Unaligned struct io pointer %p", io);
		BUG();
	}

	bio->bi_private = (void *)((unsigned long)io | region);
}

static void retrieve_io_and_region_from_bio(struct bio *bio, struct io **io,
				       unsigned *region)
{
	unsigned long val = (unsigned long)bio->bi_private;

	*io = (void *)(val & -(unsigned long)DM_IO_MAX_REGIONS);
	*region = val & (DM_IO_MAX_REGIONS - 1);
}

/*-----------------------------------------------------------------
 * 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_bits);
		if (error == -EOPNOTSUPP)
			set_bit(region, &io->eopnotsupp_bits);
	}

	if (atomic_dec_and_test(&io->count)) {
		if (io->sleeper)
			wake_up_process(io->sleeper);

		else {
			unsigned long r = io->error_bits;
			io_notify_fn fn = io->callback;
			void *context = io->context;

			mempool_free(io, io->client->pool);
			fn(r, context);
		}
	}
}

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

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

	/*
	 * The bio destructor in bio_put() may use the io object.
	 */
	retrieve_io_and_region_from_bio(bio, &io, &region);

	bio_put(bio);

	dec_count(io, region, error);
}

/*-----------------------------------------------------------------
 * 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;
}

/*
 * Functions for getting the pages from a VMA.
 */
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)
{
	unsigned region;
	struct io *io;

	retrieve_io_and_region_from_bio(bio, &io, &region);

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

/*
 * Functions for getting the pages from kernel memory.
 */
static void km_get_page(struct dpages *dp, struct page **p, unsigned long *len,
			unsigned *offset)
{
	*p = virt_to_page(dp->context_ptr);
	*offset = dp->context_u;
	*len = PAGE_SIZE - dp->context_u;
}

static void km_next_page(struct dpages *dp)
{
	dp->context_ptr += PAGE_SIZE - dp->context_u;
	dp->context_u = 0;
}

static void km_dp_init(struct dpages *dp, void *data)
{
	dp->get_page = km_get_page;
	dp->next_page = km_next_page;
	dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
	dp->context_ptr = data;
}

/*-----------------------------------------------------------------
 * IO routines that accept a list of pages.
 *---------------------------------------------------------------*/
static void do_region(int rw, unsigned region, struct dm_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;

	/*
	 * where->count may be zero if rw holds a write barrier and we
	 * need to send a zero-sized barrier.
	 */
	do {
		/*
		 * Allocate a suitably sized-bio.
		 */
		num_bvecs = dm_sector_div_up(remaining,
					     (PAGE_SIZE >> SECTOR_SHIFT));
		num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev), num_bvecs);
		bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
		bio->bi_sector = where->sector + (where->count - remaining);
		bio->bi_bdev = where->bdev;
		bio->bi_end_io = endio;
		bio->bi_destructor = dm_bio_destructor;
		store_io_and_region_in_bio(bio, io, 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);
	} while (remaining);
}

static void dispatch_io(int rw, unsigned int num_regions,
			struct dm_io_region *where, struct dpages *dp,
			struct io *io, int sync)
{
	int i;
	struct dpages old_pages = *dp;

	BUG_ON(num_regions > DM_IO_MAX_REGIONS);

	if (sync)
		rw |= REQ_SYNC | REQ_UNPLUG;

	/*
	 * 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 || (rw & REQ_HARDBARRIER))
			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 dm_io_region *where, int rw, struct dpages *dp,
		   unsigned long *error_bits)
{
	/*
	 * gcc <= 4.3 can't do the alignment for stack variables, so we must
	 * align it on our own.
	 * volatile prevents the optimizer from removing or reusing
	 * "io_" field from the stack frame (allowed in ANSI C).
	 */
	volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1];
	struct io *io = (struct io *)PTR_ALIGN(&io_, __alignof__(struct io));

	if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
		WARN_ON(1);
		return -EIO;
	}

retry:
	io->error_bits = 0;
	io->eopnotsupp_bits = 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))
			break;

		io_schedule();
	}
	set_current_state(TASK_RUNNING);

	if (io->eopnotsupp_bits && (rw & REQ_HARDBARRIER)) {
		rw &= ~REQ_HARDBARRIER;
		goto retry;
	}

	if (error_bits)
		*error_bits = io->error_bits;

	return io->error_bits ? -EIO : 0;
}

static int async_io(struct dm_io_client *client, unsigned int num_regions,
		    struct dm_io_region *where, int rw, struct dpages *dp,
		    io_notify_fn fn, void *context)
{
	struct io *io;

	if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
		WARN_ON(1);
		fn(1, context);
		return -EIO;
	}

	io = mempool_alloc(client->pool, GFP_NOIO);
	io->error_bits = 0;
	io->eopnotsupp_bits = 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;
}

static int dp_init(struct dm_io_request *io_req, struct dpages *dp)
{
	/* Set up dpages based on memory type */
	switch (io_req->mem.type) {
	case DM_IO_PAGE_LIST:
		list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
		break;

	case DM_IO_BVEC:
		bvec_dp_init(dp, io_req->mem.ptr.bvec);
		break;

	case DM_IO_VMA:
		vm_dp_init(dp, io_req->mem.ptr.vma);
		break;

	case DM_IO_KMEM:
		km_dp_init(dp, io_req->mem.ptr.addr);
		break;

	default:
		return -EINVAL;
	}

	return 0;
}

/*
 * New collapsed (a)synchronous interface.
 *
 * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
 * the queue with blk_unplug() some time later or set REQ_SYNC in
io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
 * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
 */
int dm_io(struct dm_io_request *io_req, unsigned num_regions,
	  struct dm_io_region *where, unsigned long *sync_error_bits)
{
	int r;
	struct dpages dp;

	r = dp_init(io_req, &dp);
	if (r)
		return r;

	if (!io_req->notify.fn)
		return sync_io(io_req->client, num_regions, where,
			       io_req->bi_rw, &dp, sync_error_bits);

	return async_io(io_req->client, num_regions, where, io_req->bi_rw,
			&dp, io_req->notify.fn, io_req->notify.context);
}
EXPORT_SYMBOL(dm_io);

int __init dm_io_init(void)
{
	_dm_io_cache = KMEM_CACHE(io, 0);
	if (!_dm_io_cache)
		return -ENOMEM;

	return 0;
}

void dm_io_exit(void)
{
	kmem_cache_destroy(_dm_io_cache);
	_dm_io_cache = NULL;
}
Commit	Line	Data
1da177e4 LT	1	/*
1da177e4 LT	2	* Copyright (C) 2003 Sistina Software
891ce207	3	* Copyright (C) 2006 Red Hat GmbH
1da177e4 LT	4	*
	5	* This file is released under the GPL.
	6	*/
	7
952b3557 MP	8	#include "dm.h"
952b3557 MP	9
586e80e6	10	#include <linux/device-mapper.h>
1da177e4 LT	11
	12	#include <linux/bio.h>
	13	#include <linux/mempool.h>
	14	#include <linux/module.h>
	15	#include <linux/sched.h>
	16	#include <linux/slab.h>
a765e20e	17	#include <linux/dm-io.h>
1da177e4	18
f1e53987 MP	19	#define DM_MSG_PREFIX "io"
	20
	21	#define DM_IO_MAX_REGIONS BITS_PER_LONG
	22
891ce207 HM	23	struct dm_io_client {
	24	mempool_t *pool;
	25	struct bio_set *bios;
	26	};
	27
f1e53987 MP	28	/*
	29	* Aligning 'struct io' reduces the number of bits required to store
	30	* its address. Refer to store_io_and_region_in_bio() below.
	31	*/
1da177e4	32	struct io {
e01fd7ee	33	unsigned long error_bits;
5af443a7	34	unsigned long eopnotsupp_bits;
1da177e4 LT	35	atomic_t count;
1da177e4 LT	36	struct task_struct *sleeper;
891ce207	37	struct dm_io_client *client;
1da177e4 LT	38	io_notify_fn callback;
1da177e4 LT	39	void *context;
f1e53987	40	} __attribute__((aligned(DM_IO_MAX_REGIONS)));
1da177e4	41
952b3557 MP	42	static struct kmem_cache *_dm_io_cache;
952b3557 MP	43
1da177e4 LT	44	/*
	45	* io contexts are only dynamically allocated for asynchronous
	46	* io. Since async io is likely to be the majority of io we'll
891ce207	47	* have the same number of io contexts as bios! (FIXME: must reduce this).
1da177e4	48	*/
891ce207	49
1da177e4 LT	50	static unsigned int pages_to_ios(unsigned int pages)
	51	{
	52	return 4 * pages; /* too many ? */
	53	}
	54
c8b03afe HM	55	/*
	56	* Create a client with mempool and bioset.
	57	*/
	58	struct dm_io_client *dm_io_client_create(unsigned num_pages)
	59	{
	60	unsigned ios = pages_to_ios(num_pages);
	61	struct dm_io_client *client;
	62
	63	client = kmalloc(sizeof(*client), GFP_KERNEL);
	64	if (!client)
	65	return ERR_PTR(-ENOMEM);
	66
952b3557	67	client->pool = mempool_create_slab_pool(ios, _dm_io_cache);
c8b03afe HM	68	if (!client->pool)
	69	goto bad;
	70
bb799ca0	71	client->bios = bioset_create(16, 0);
c8b03afe HM	72	if (!client->bios)
	73	goto bad;
	74
	75	return client;
	76
	77	bad:
	78	if (client->pool)
	79	mempool_destroy(client->pool);
	80	kfree(client);
	81	return ERR_PTR(-ENOMEM);
	82	}
	83	EXPORT_SYMBOL(dm_io_client_create);
	84
	85	int dm_io_client_resize(unsigned num_pages, struct dm_io_client *client)
	86	{
	87	return mempool_resize(client->pool, pages_to_ios(num_pages),
	88	GFP_KERNEL);
	89	}
	90	EXPORT_SYMBOL(dm_io_client_resize);
	91
	92	void dm_io_client_destroy(struct dm_io_client *client)
	93	{
	94	mempool_destroy(client->pool);
	95	bioset_free(client->bios);
	96	kfree(client);
	97	}
	98	EXPORT_SYMBOL(dm_io_client_destroy);
	99
1da177e4 LT	100	/*-----------------------------------------------------------------
1da177e4 LT	101	* We need to keep track of which region a bio is doing io for.
f1e53987 MP	102	* To avoid a memory allocation to store just 5 or 6 bits, we
	103	* ensure the 'struct io' pointer is aligned so enough low bits are
	104	* always zero and then combine it with the region number directly in
	105	* bi_private.
1da177e4	106	---------------------------------------------------------------/
f1e53987 MP	107	static void store_io_and_region_in_bio(struct bio bio, struct io io,
f1e53987 MP	108	unsigned region)
1da177e4	109	{
f1e53987 MP	110	if (unlikely(!IS_ALIGNED((unsigned long)io, DM_IO_MAX_REGIONS))) {
	111	DMCRIT("Unaligned struct io pointer %p", io);
	112	BUG();
	113	}
	114
	115	bio->bi_private = (void *)((unsigned long)io \| region);
1da177e4 LT	116	}
1da177e4 LT	117
f1e53987 MP	118	static void retrieve_io_and_region_from_bio(struct bio bio, struct io *io,
f1e53987 MP	119	unsigned *region)
1da177e4	120	{
f1e53987 MP	121	unsigned long val = (unsigned long)bio->bi_private;
	122
	123	io = (void )(val & -(unsigned long)DM_IO_MAX_REGIONS);
	124	*region = val & (DM_IO_MAX_REGIONS - 1);
1da177e4 LT	125	}
	126
	127	/*-----------------------------------------------------------------
	128	* We need an io object to keep track of the number of bios that
	129	* have been dispatched for a particular io.
	130	---------------------------------------------------------------/
	131	static void dec_count(struct io *io, unsigned int region, int error)
	132	{
5af443a7	133	if (error) {
e01fd7ee	134	set_bit(region, &io->error_bits);
5af443a7 MP	135	if (error == -EOPNOTSUPP)
	136	set_bit(region, &io->eopnotsupp_bits);
	137	}
1da177e4 LT	138
	139	if (atomic_dec_and_test(&io->count)) {
	140	if (io->sleeper)
	141	wake_up_process(io->sleeper);
	142
	143	else {
e01fd7ee	144	unsigned long r = io->error_bits;
1da177e4 LT	145	io_notify_fn fn = io->callback;
	146	void *context = io->context;
	147
bf17ce3a	148	mempool_free(io, io->client->pool);
1da177e4 LT	149	fn(r, context);
	150	}
	151	}
	152	}
	153
6712ecf8	154	static void endio(struct bio *bio, int error)
1da177e4	155	{
c897feb3 HM	156	struct io *io;
c897feb3 HM	157	unsigned region;
1da177e4	158
1da177e4 LT	159	if (error && bio_data_dir(bio) == READ)
	160	zero_fill_bio(bio);
	161
c897feb3 HM	162	/*
	163	* The bio destructor in bio_put() may use the io object.
	164	*/
f1e53987	165	retrieve_io_and_region_from_bio(bio, &io, &region);
c897feb3	166
1da177e4 LT	167	bio_put(bio);
1da177e4 LT	168
c897feb3	169	dec_count(io, region, error);
1da177e4 LT	170	}
	171
	172	/*-----------------------------------------------------------------
	173	* These little objects provide an abstraction for getting a new
	174	* destination page for io.
	175	---------------------------------------------------------------/
	176	struct dpages {
	177	void (get_page)(struct dpages dp,
	178	struct page *p, unsigned long len, unsigned *offset);
	179	void (next_page)(struct dpages dp);
	180
	181	unsigned context_u;
	182	void *context_ptr;
	183	};
	184
	185	/*
	186	* Functions for getting the pages from a list.
	187	*/
	188	static void list_get_page(struct dpages *dp,
	189	struct page *p, unsigned long len, unsigned *offset)
	190	{
	191	unsigned o = dp->context_u;
	192	struct page_list pl = (struct page_list ) dp->context_ptr;
	193
	194	*p = pl->page;
	195	*len = PAGE_SIZE - o;
	196	*offset = o;
	197	}
	198
	199	static void list_next_page(struct dpages *dp)
	200	{
	201	struct page_list pl = (struct page_list ) dp->context_ptr;
	202	dp->context_ptr = pl->next;
	203	dp->context_u = 0;
	204	}
	205
	206	static void list_dp_init(struct dpages dp, struct page_list pl, unsigned offset)
	207	{
	208	dp->get_page = list_get_page;
	209	dp->next_page = list_next_page;
	210	dp->context_u = offset;
	211	dp->context_ptr = pl;
	212	}
	213
	214	/*
	215	* Functions for getting the pages from a bvec.
	216	*/
	217	static void bvec_get_page(struct dpages *dp,
	218	struct page *p, unsigned long len, unsigned *offset)
	219	{
	220	struct bio_vec bvec = (struct bio_vec ) dp->context_ptr;
	221	*p = bvec->bv_page;
	222	*len = bvec->bv_len;
	223	*offset = bvec->bv_offset;
	224	}
	225
	226	static void bvec_next_page(struct dpages *dp)
	227	{
	228	struct bio_vec bvec = (struct bio_vec ) dp->context_ptr;
	229	dp->context_ptr = bvec + 1;
	230	}
	231
	232	static void bvec_dp_init(struct dpages dp, struct bio_vec bvec)
	233	{
234	dp->get_page = bvec_get_page;
235	dp->next_page = bvec_next_page;
236	dp->context_ptr = bvec;
237	}
238
c8b03afe HM	239	/*
	240	* Functions for getting the pages from a VMA.
	241	*/
1da177e4 LT	242	static void vm_get_page(struct dpages *dp,
	243	struct page *p, unsigned long len, unsigned *offset)
	244	{
	245	*p = vmalloc_to_page(dp->context_ptr);
	246	*offset = dp->context_u;
	247	*len = PAGE_SIZE - dp->context_u;
	248	}
	249
	250	static void vm_next_page(struct dpages *dp)
	251	{
	252	dp->context_ptr += PAGE_SIZE - dp->context_u;
	253	dp->context_u = 0;
	254	}
	255
	256	static void vm_dp_init(struct dpages dp, void data)
	257	{
	258	dp->get_page = vm_get_page;
	259	dp->next_page = vm_next_page;
	260	dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
	261	dp->context_ptr = data;
	262	}
	263
3676347a PO	264	static void dm_bio_destructor(struct bio *bio)
3676347a PO	265	{
f1e53987 MP	266	unsigned region;
	267	struct io *io;
	268
	269	retrieve_io_and_region_from_bio(bio, &io, &region);
891ce207	270
bf17ce3a	271	bio_free(bio, io->client->bios);
3676347a PO	272	}
3676347a PO	273
c8b03afe HM	274	/*
	275	* Functions for getting the pages from kernel memory.
	276	*/
	277	static void km_get_page(struct dpages dp, struct page p, unsigned long len,
	278	unsigned *offset)
	279	{
	280	*p = virt_to_page(dp->context_ptr);
	281	*offset = dp->context_u;
	282	*len = PAGE_SIZE - dp->context_u;
	283	}
	284
	285	static void km_next_page(struct dpages *dp)
	286	{
	287	dp->context_ptr += PAGE_SIZE - dp->context_u;
	288	dp->context_u = 0;
	289	}
	290
	291	static void km_dp_init(struct dpages dp, void data)
	292	{
	293	dp->get_page = km_get_page;
	294	dp->next_page = km_next_page;
	295	dp->context_u = ((unsigned long) data) & (PAGE_SIZE - 1);
	296	dp->context_ptr = data;
	297	}
	298
1da177e4 LT	299	/*-----------------------------------------------------------------
	300	* IO routines that accept a list of pages.
	301	---------------------------------------------------------------/
22a1ceb1	302	static void do_region(int rw, unsigned region, struct dm_io_region *where,
1da177e4 LT	303	struct dpages dp, struct io io)
	304	{
	305	struct bio *bio;
	306	struct page *page;
	307	unsigned long len;
	308	unsigned offset;
	309	unsigned num_bvecs;
	310	sector_t remaining = where->count;
	311
12fc0f49 MP	312	/*
	313	* where->count may be zero if rw holds a write barrier and we
	314	* need to send a zero-sized barrier.
	315	*/
	316	do {
1da177e4	317	/*
f1e53987	318	* Allocate a suitably sized-bio.
1da177e4	319	*/
596f138e JN	320	num_bvecs = dm_sector_div_up(remaining,
596f138e JN	321	(PAGE_SIZE >> SECTOR_SHIFT));
f1e53987	322	num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev), num_bvecs);
bf17ce3a	323	bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
1da177e4 LT	324	bio->bi_sector = where->sector + (where->count - remaining);
	325	bio->bi_bdev = where->bdev;
	326	bio->bi_end_io = endio;
3676347a	327	bio->bi_destructor = dm_bio_destructor;
f1e53987	328	store_io_and_region_in_bio(bio, io, region);
1da177e4 LT	329
	330	/*
	331	* Try and add as many pages as possible.
	332	*/
	333	while (remaining) {
	334	dp->get_page(dp, &page, &len, &offset);
	335	len = min(len, to_bytes(remaining));
	336	if (!bio_add_page(bio, page, len, offset))
	337	break;
	338
	339	offset = 0;
	340	remaining -= to_sector(len);
	341	dp->next_page(dp);
	342	}
	343
	344	atomic_inc(&io->count);
	345	submit_bio(rw, bio);
12fc0f49	346	} while (remaining);
1da177e4 LT	347	}
	348
	349	static void dispatch_io(int rw, unsigned int num_regions,
22a1ceb1	350	struct dm_io_region where, struct dpages dp,
1da177e4 LT	351	struct io *io, int sync)
	352	{
	353	int i;
	354	struct dpages old_pages = *dp;
	355
f1e53987 MP	356	BUG_ON(num_regions > DM_IO_MAX_REGIONS);
f1e53987 MP	357
1da177e4	358	if (sync)
7b6d91da	359	rw \|= REQ_SYNC \| REQ_UNPLUG;
1da177e4 LT	360
	361	/*
	362	* For multiple regions we need to be careful to rewind
	363	* the dp object for each call to do_region.
	364	*/
	365	for (i = 0; i < num_regions; i++) {
	366	*dp = old_pages;
7b6d91da	367	if (where[i].count \|\| (rw & REQ_HARDBARRIER))
1da177e4 LT	368	do_region(rw, i, where + i, dp, io);
	369	}
	370
	371	/*
f00b16ad	372	* Drop the extra reference that we were holding to avoid
1da177e4 LT	373	* the io being completed too early.
	374	*/
	375	dec_count(io, 0, 0);
	376	}
	377
891ce207	378	static int sync_io(struct dm_io_client *client, unsigned int num_regions,
22a1ceb1	379	struct dm_io_region where, int rw, struct dpages dp,
891ce207	380	unsigned long *error_bits)
1da177e4	381	{
f1e53987 MP	382	/*
	383	* gcc <= 4.3 can't do the alignment for stack variables, so we must
	384	* align it on our own.
	385	* volatile prevents the optimizer from removing or reusing
	386	* "io_" field from the stack frame (allowed in ANSI C).
	387	*/
	388	volatile char io_[sizeof(struct io) + __alignof__(struct io) - 1];
	389	struct io io = (struct io )PTR_ALIGN(&io_, __alignof__(struct io));
1da177e4	390
7ff14a36	391	if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
1da177e4 LT	392	WARN_ON(1);
	393	return -EIO;
	394	}
	395
51aa3228	396	retry:
f1e53987 MP	397	io->error_bits = 0;
	398	io->eopnotsupp_bits = 0;
	399	atomic_set(&io->count, 1); /* see dispatch_io() */
	400	io->sleeper = current;
	401	io->client = client;
1da177e4	402
f1e53987	403	dispatch_io(rw, num_regions, where, dp, io, 1);
1da177e4 LT	404
	405	while (1) {
	406	set_current_state(TASK_UNINTERRUPTIBLE);
	407
f1e53987	408	if (!atomic_read(&io->count))
1da177e4 LT	409	break;
	410
	411	io_schedule();
	412	}
	413	set_current_state(TASK_RUNNING);
	414
7b6d91da CH	415	if (io->eopnotsupp_bits && (rw & REQ_HARDBARRIER)) {
7b6d91da CH	416	rw &= ~REQ_HARDBARRIER;
51aa3228 MP	417	goto retry;
	418	}
	419
891ce207	420	if (error_bits)
f1e53987	421	*error_bits = io->error_bits;
891ce207	422
f1e53987	423	return io->error_bits ? -EIO : 0;
1da177e4 LT	424	}
1da177e4 LT	425
891ce207	426	static int async_io(struct dm_io_client *client, unsigned int num_regions,
22a1ceb1	427	struct dm_io_region where, int rw, struct dpages dp,
891ce207	428	io_notify_fn fn, void *context)
1da177e4 LT	429	{
	430	struct io *io;
	431
7ff14a36	432	if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
1da177e4 LT	433	WARN_ON(1);
	434	fn(1, context);
	435	return -EIO;
	436	}
	437
bf17ce3a	438	io = mempool_alloc(client->pool, GFP_NOIO);
e01fd7ee	439	io->error_bits = 0;
5af443a7	440	io->eopnotsupp_bits = 0;
1da177e4 LT	441	atomic_set(&io->count, 1); /* see dispatch_io() */
1da177e4 LT	442	io->sleeper = NULL;
891ce207	443	io->client = client;
1da177e4 LT	444	io->callback = fn;
	445	io->context = context;
	446
	447	dispatch_io(rw, num_regions, where, dp, io, 0);
	448	return 0;
	449	}
	450
c8b03afe HM	451	static int dp_init(struct dm_io_request io_req, struct dpages dp)
	452	{
	453	/* Set up dpages based on memory type */
	454	switch (io_req->mem.type) {
	455	case DM_IO_PAGE_LIST:
	456	list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
	457	break;
	458
	459	case DM_IO_BVEC:
	460	bvec_dp_init(dp, io_req->mem.ptr.bvec);
	461	break;
	462
	463	case DM_IO_VMA:
	464	vm_dp_init(dp, io_req->mem.ptr.vma);
	465	break;
	466
	467	case DM_IO_KMEM:
	468	km_dp_init(dp, io_req->mem.ptr.addr);
	469	break;
	470
	471	default:
	472	return -EINVAL;
	473	}
	474
	475	return 0;
	476	}
	477
	478	/*
7ff14a36 MP	479	* New collapsed (a)synchronous interface.
	480	*
	481	* If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
7b6d91da CH	482	* the queue with blk_unplug() some time later or set REQ_SYNC in
7b6d91da CH	483	io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
7ff14a36	484	* the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
c8b03afe HM	485	*/
c8b03afe HM	486	int dm_io(struct dm_io_request *io_req, unsigned num_regions,
22a1ceb1	487	struct dm_io_region where, unsigned long sync_error_bits)
c8b03afe HM	488	{
	489	int r;
	490	struct dpages dp;
	491
	492	r = dp_init(io_req, &dp);
	493	if (r)
	494	return r;
	495
	496	if (!io_req->notify.fn)
	497	return sync_io(io_req->client, num_regions, where,
	498	io_req->bi_rw, &dp, sync_error_bits);
	499
	500	return async_io(io_req->client, num_regions, where, io_req->bi_rw,
	501	&dp, io_req->notify.fn, io_req->notify.context);
	502	}
	503	EXPORT_SYMBOL(dm_io);
952b3557 MP	504
	505	int __init dm_io_init(void)
	506	{
	507	_dm_io_cache = KMEM_CACHE(io, 0);
	508	if (!_dm_io_cache)
	509	return -ENOMEM;
	510
	511	return 0;
	512	}
	513
	514	void dm_io_exit(void)
	515	{
	516	kmem_cache_destroy(_dm_io_cache);
	517	_dm_io_cache = NULL;
	518	}