[deliverable/linux.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/completion.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;
	atomic_t count;
	struct dm_io_client *client;
	io_notify_fn callback;
	void *context;
	void *vma_invalidate_address;
	unsigned long vma_invalidate_size;
} __attribute__((aligned(DM_IO_MAX_REGIONS)));

static struct kmem_cache *_dm_io_cache;

/*
 * Create a client with mempool and bioset.
 */
struct dm_io_client *dm_io_client_create(void)
{
	struct dm_io_client *client;
	unsigned min_ios = dm_get_reserved_bio_based_ios();

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

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

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

	return client;

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

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 complete_io(struct io *io)
{
	unsigned long error_bits = io->error_bits;
	io_notify_fn fn = io->callback;
	void *context = io->context;

	if (io->vma_invalidate_size)
		invalidate_kernel_vmap_range(io->vma_invalidate_address,
					     io->vma_invalidate_size);

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

static void dec_count(struct io *io, unsigned int region, int error)
{
	if (error)
		set_bit(region, &io->error_bits);

	if (atomic_dec_and_test(&io->count))
		complete_io(io);
}

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

	if (bio->bi_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);

	error = bio->bi_error;
	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;

	void *vma_invalidate_address;
	unsigned long vma_invalidate_size;
};

/*
 * 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 bio_get_page(struct dpages *dp, struct page **p,
			 unsigned long *len, unsigned *offset)
{
	struct bio_vec *bvec = dp->context_ptr;
	*p = bvec->bv_page;
	*len = bvec->bv_len - dp->context_u;
	*offset = bvec->bv_offset + dp->context_u;
}

static void bio_next_page(struct dpages *dp)
{
	struct bio_vec *bvec = dp->context_ptr;
	dp->context_ptr = bvec + 1;
	dp->context_u = 0;
}

static void bio_dp_init(struct dpages *dp, struct bio *bio)
{
	dp->get_page = bio_get_page;
	dp->next_page = bio_next_page;
	dp->context_ptr = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
	dp->context_u = bio->bi_iter.bi_bvec_done;
}

/*
 * 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 = offset_in_page(data);
	dp->context_ptr = data;
}

/*
 * 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 = offset_in_page(data);
	dp->context_ptr = data;
}

/*-----------------------------------------------------------------
 * IO routines that accept a list of pages.
 *---------------------------------------------------------------*/
static void do_region(int op, int op_flags, 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;
	struct request_queue *q = bdev_get_queue(where->bdev);
	unsigned short logical_block_size = queue_logical_block_size(q);
	sector_t num_sectors;
	unsigned int uninitialized_var(special_cmd_max_sectors);

	/*
	 * Reject unsupported discard and write same requests.
	 */
	if (op == REQ_OP_DISCARD)
		special_cmd_max_sectors = q->limits.max_discard_sectors;
	else if (op == REQ_OP_WRITE_SAME)
		special_cmd_max_sectors = q->limits.max_write_same_sectors;
	if ((op == REQ_OP_DISCARD || op == REQ_OP_WRITE_SAME) &&
	    special_cmd_max_sectors == 0) {
		dec_count(io, region, -EOPNOTSUPP);
		return;
	}

	/*
	 * where->count may be zero if op holds a flush and we need to
	 * send a zero-sized flush.
	 */
	do {
		/*
		 * Allocate a suitably sized-bio.
		 */
		if ((op == REQ_OP_DISCARD) || (op == REQ_OP_WRITE_SAME))
			num_bvecs = 1;
		else
			num_bvecs = min_t(int, BIO_MAX_PAGES,
					  dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));

		bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
		bio->bi_iter.bi_sector = where->sector + (where->count - remaining);
		bio->bi_bdev = where->bdev;
		bio->bi_end_io = endio;
		bio_set_op_attrs(bio, op, op_flags);
		store_io_and_region_in_bio(bio, io, region);

		if (op == REQ_OP_DISCARD) {
			num_sectors = min_t(sector_t, special_cmd_max_sectors, remaining);
			bio->bi_iter.bi_size = num_sectors << SECTOR_SHIFT;
			remaining -= num_sectors;
		} else if (op == REQ_OP_WRITE_SAME) {
			/*
			 * WRITE SAME only uses a single page.
			 */
			dp->get_page(dp, &page, &len, &offset);
			bio_add_page(bio, page, logical_block_size, offset);
			num_sectors = min_t(sector_t, special_cmd_max_sectors, remaining);
			bio->bi_iter.bi_size = num_sectors << SECTOR_SHIFT;

			offset = 0;
			remaining -= num_sectors;
			dp->next_page(dp);
		} else while (remaining) {
			/*
			 * Try and add as many pages as possible.
			 */
			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(bio);
	} while (remaining);
}

static void dispatch_io(int op, int op_flags, 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)
		op_flags |= REQ_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 || (op_flags & REQ_PREFLUSH))
			do_region(op, op_flags, 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);
}

struct sync_io {
	unsigned long error_bits;
	struct completion wait;
};

static void sync_io_complete(unsigned long error, void *context)
{
	struct sync_io *sio = context;

	sio->error_bits = error;
	complete(&sio->wait);
}

static int sync_io(struct dm_io_client *client, unsigned int num_regions,
		   struct dm_io_region *where, int op, int op_flags,
		   struct dpages *dp, unsigned long *error_bits)
{
	struct io *io;
	struct sync_io sio;

	if (num_regions > 1 && !op_is_write(op)) {
		WARN_ON(1);
		return -EIO;
	}

	init_completion(&sio.wait);

	io = mempool_alloc(client->pool, GFP_NOIO);
	io->error_bits = 0;
	atomic_set(&io->count, 1); /* see dispatch_io() */
	io->client = client;
	io->callback = sync_io_complete;
	io->context = &sio;

	io->vma_invalidate_address = dp->vma_invalidate_address;
	io->vma_invalidate_size = dp->vma_invalidate_size;

	dispatch_io(op, op_flags, num_regions, where, dp, io, 1);

	wait_for_completion_io(&sio.wait);

	if (error_bits)
		*error_bits = sio.error_bits;

	return sio.error_bits ? -EIO : 0;
}

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

	if (num_regions > 1 && !op_is_write(op)) {
		WARN_ON(1);
		fn(1, context);
		return -EIO;
	}

	io = mempool_alloc(client->pool, GFP_NOIO);
	io->error_bits = 0;
	atomic_set(&io->count, 1); /* see dispatch_io() */
	io->client = client;
	io->callback = fn;
	io->context = context;

	io->vma_invalidate_address = dp->vma_invalidate_address;
	io->vma_invalidate_size = dp->vma_invalidate_size;

	dispatch_io(op, op_flags, num_regions, where, dp, io, 0);
	return 0;
}

static int dp_init(struct dm_io_request *io_req, struct dpages *dp,
		   unsigned long size)
{
	/* Set up dpages based on memory type */

	dp->vma_invalidate_address = NULL;
	dp->vma_invalidate_size = 0;

	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_BIO:
		bio_dp_init(dp, io_req->mem.ptr.bio);
		break;

	case DM_IO_VMA:
		flush_kernel_vmap_range(io_req->mem.ptr.vma, size);
		if (io_req->bi_op == REQ_OP_READ) {
			dp->vma_invalidate_address = io_req->mem.ptr.vma;
			dp->vma_invalidate_size = size;
		}
		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, (unsigned long)where->count << SECTOR_SHIFT);
	if (r)
		return r;

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

	return async_io(io_req->client, num_regions, where, io_req->bi_op,
			io_req->bi_op_flags, &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
	1	/*
	2	* Copyright (C) 2003 Sistina Software
	3	* Copyright (C) 2006 Red Hat GmbH
	4	*
	5	* This file is released under the GPL.
	6	*/
	7
	8	#include "dm.h"
	9
	10	#include <linux/device-mapper.h>
	11
	12	#include <linux/bio.h>
	13	#include <linux/completion.h>
	14	#include <linux/mempool.h>
	15	#include <linux/module.h>
	16	#include <linux/sched.h>
	17	#include <linux/slab.h>
	18	#include <linux/dm-io.h>
	19
	20	#define DM_MSG_PREFIX "io"
	21
	22	#define DM_IO_MAX_REGIONS BITS_PER_LONG
	23
	24	struct dm_io_client {
	25	mempool_t *pool;
	26	struct bio_set *bios;
	27	};
	28
	29	/*
	30	* Aligning 'struct io' reduces the number of bits required to store
	31	* its address. Refer to store_io_and_region_in_bio() below.
	32	*/
	33	struct io {
	34	unsigned long error_bits;
	35	atomic_t count;
	36	struct dm_io_client *client;
	37	io_notify_fn callback;
	38	void *context;
	39	void *vma_invalidate_address;
	40	unsigned long vma_invalidate_size;
	41	} __attribute__((aligned(DM_IO_MAX_REGIONS)));
	42
	43	static struct kmem_cache *_dm_io_cache;
	44
	45	/*
	46	* Create a client with mempool and bioset.
	47	*/
	48	struct dm_io_client *dm_io_client_create(void)
	49	{
	50	struct dm_io_client *client;
	51	unsigned min_ios = dm_get_reserved_bio_based_ios();
	52
	53	client = kmalloc(sizeof(*client), GFP_KERNEL);
	54	if (!client)
	55	return ERR_PTR(-ENOMEM);
	56
	57	client->pool = mempool_create_slab_pool(min_ios, _dm_io_cache);
	58	if (!client->pool)
	59	goto bad;
	60
	61	client->bios = bioset_create(min_ios, 0);
	62	if (!client->bios)
	63	goto bad;
	64
	65	return client;
	66
	67	bad:
	68	mempool_destroy(client->pool);
	69	kfree(client);
	70	return ERR_PTR(-ENOMEM);
	71	}
	72	EXPORT_SYMBOL(dm_io_client_create);
	73
	74	void dm_io_client_destroy(struct dm_io_client *client)
	75	{
	76	mempool_destroy(client->pool);
	77	bioset_free(client->bios);
	78	kfree(client);
	79	}
	80	EXPORT_SYMBOL(dm_io_client_destroy);
	81
	82	/*-----------------------------------------------------------------
	83	* We need to keep track of which region a bio is doing io for.
	84	* To avoid a memory allocation to store just 5 or 6 bits, we
	85	* ensure the 'struct io' pointer is aligned so enough low bits are
	86	* always zero and then combine it with the region number directly in
	87	* bi_private.
	88	---------------------------------------------------------------/
	89	static void store_io_and_region_in_bio(struct bio bio, struct io io,
	90	unsigned region)
	91	{
	92	if (unlikely(!IS_ALIGNED((unsigned long)io, DM_IO_MAX_REGIONS))) {
	93	DMCRIT("Unaligned struct io pointer %p", io);
	94	BUG();
	95	}
	96
	97	bio->bi_private = (void *)((unsigned long)io \| region);
	98	}
	99
	100	static void retrieve_io_and_region_from_bio(struct bio bio, struct io *io,
	101	unsigned *region)
	102	{
	103	unsigned long val = (unsigned long)bio->bi_private;
	104
	105	io = (void )(val & -(unsigned long)DM_IO_MAX_REGIONS);
	106	*region = val & (DM_IO_MAX_REGIONS - 1);
	107	}
	108
	109	/*-----------------------------------------------------------------
	110	* We need an io object to keep track of the number of bios that
	111	* have been dispatched for a particular io.
	112	---------------------------------------------------------------/
	113	static void complete_io(struct io *io)
	114	{
	115	unsigned long error_bits = io->error_bits;
	116	io_notify_fn fn = io->callback;
	117	void *context = io->context;
	118
	119	if (io->vma_invalidate_size)
	120	invalidate_kernel_vmap_range(io->vma_invalidate_address,
	121	io->vma_invalidate_size);
	122
	123	mempool_free(io, io->client->pool);
	124	fn(error_bits, context);
	125	}
	126
	127	static void dec_count(struct io *io, unsigned int region, int error)
	128	{
	129	if (error)
	130	set_bit(region, &io->error_bits);
	131
	132	if (atomic_dec_and_test(&io->count))
	133	complete_io(io);
	134	}
	135
	136	static void endio(struct bio *bio)
	137	{
	138	struct io *io;
	139	unsigned region;
	140	int error;
	141
	142	if (bio->bi_error && bio_data_dir(bio) == READ)
	143	zero_fill_bio(bio);
	144
	145	/*
	146	* The bio destructor in bio_put() may use the io object.
	147	*/
	148	retrieve_io_and_region_from_bio(bio, &io, &region);
	149
	150	error = bio->bi_error;
	151	bio_put(bio);
	152
	153	dec_count(io, region, error);
	154	}
	155
	156	/*-----------------------------------------------------------------
	157	* These little objects provide an abstraction for getting a new
	158	* destination page for io.
	159	---------------------------------------------------------------/
	160	struct dpages {
	161	void (get_page)(struct dpages dp,
	162	struct page *p, unsigned long len, unsigned *offset);
	163	void (next_page)(struct dpages dp);
	164
	165	unsigned context_u;
	166	void *context_ptr;
	167
	168	void *vma_invalidate_address;
	169	unsigned long vma_invalidate_size;
	170	};
	171
	172	/*
	173	* Functions for getting the pages from a list.
	174	*/
	175	static void list_get_page(struct dpages *dp,
	176	struct page *p, unsigned long len, unsigned *offset)
	177	{
	178	unsigned o = dp->context_u;
	179	struct page_list pl = (struct page_list ) dp->context_ptr;
	180
	181	*p = pl->page;
	182	*len = PAGE_SIZE - o;
	183	*offset = o;
	184	}
	185
	186	static void list_next_page(struct dpages *dp)
	187	{
	188	struct page_list pl = (struct page_list ) dp->context_ptr;
	189	dp->context_ptr = pl->next;
	190	dp->context_u = 0;
	191	}
	192
	193	static void list_dp_init(struct dpages dp, struct page_list pl, unsigned offset)
	194	{
	195	dp->get_page = list_get_page;
	196	dp->next_page = list_next_page;
	197	dp->context_u = offset;
	198	dp->context_ptr = pl;
	199	}
	200
	201	/*
	202	* Functions for getting the pages from a bvec.
	203	*/
	204	static void bio_get_page(struct dpages dp, struct page *p,
	205	unsigned long len, unsigned offset)
	206	{
	207	struct bio_vec *bvec = dp->context_ptr;
	208	*p = bvec->bv_page;
	209	*len = bvec->bv_len - dp->context_u;
	210	*offset = bvec->bv_offset + dp->context_u;
	211	}
	212
	213	static void bio_next_page(struct dpages *dp)
	214	{
	215	struct bio_vec *bvec = dp->context_ptr;
	216	dp->context_ptr = bvec + 1;
	217	dp->context_u = 0;
	218	}
	219
	220	static void bio_dp_init(struct dpages dp, struct bio bio)
	221	{
	222	dp->get_page = bio_get_page;
	223	dp->next_page = bio_next_page;
	224	dp->context_ptr = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
	225	dp->context_u = bio->bi_iter.bi_bvec_done;
	226	}
	227
	228	/*
	229	* Functions for getting the pages from a VMA.
	230	*/
	231	static void vm_get_page(struct dpages *dp,
	232	struct page *p, unsigned long len, unsigned *offset)
	233	{
	234	*p = vmalloc_to_page(dp->context_ptr);
	235	*offset = dp->context_u;
	236	*len = PAGE_SIZE - dp->context_u;
	237	}
	238
	239	static void vm_next_page(struct dpages *dp)
	240	{
	241	dp->context_ptr += PAGE_SIZE - dp->context_u;
	242	dp->context_u = 0;
	243	}
	244
	245	static void vm_dp_init(struct dpages dp, void data)
	246	{
	247	dp->get_page = vm_get_page;
	248	dp->next_page = vm_next_page;
	249	dp->context_u = offset_in_page(data);
	250	dp->context_ptr = data;
	251	}
	252
	253	/*
	254	* Functions for getting the pages from kernel memory.
	255	*/
	256	static void km_get_page(struct dpages dp, struct page p, unsigned long len,
	257	unsigned *offset)
	258	{
	259	*p = virt_to_page(dp->context_ptr);
	260	*offset = dp->context_u;
	261	*len = PAGE_SIZE - dp->context_u;
	262	}
	263
	264	static void km_next_page(struct dpages *dp)
	265	{
	266	dp->context_ptr += PAGE_SIZE - dp->context_u;
	267	dp->context_u = 0;
	268	}
	269
	270	static void km_dp_init(struct dpages dp, void data)
	271	{
	272	dp->get_page = km_get_page;
	273	dp->next_page = km_next_page;
	274	dp->context_u = offset_in_page(data);
	275	dp->context_ptr = data;
	276	}
	277
	278	/*-----------------------------------------------------------------
	279	* IO routines that accept a list of pages.
	280	---------------------------------------------------------------/
	281	static void do_region(int op, int op_flags, unsigned region,
	282	struct dm_io_region where, struct dpages dp,
	283	struct io *io)
	284	{
	285	struct bio *bio;
	286	struct page *page;
	287	unsigned long len;
	288	unsigned offset;
	289	unsigned num_bvecs;
	290	sector_t remaining = where->count;
	291	struct request_queue *q = bdev_get_queue(where->bdev);
	292	unsigned short logical_block_size = queue_logical_block_size(q);
	293	sector_t num_sectors;
	294	unsigned int uninitialized_var(special_cmd_max_sectors);
	295
	296	/*
	297	* Reject unsupported discard and write same requests.
	298	*/
	299	if (op == REQ_OP_DISCARD)
	300	special_cmd_max_sectors = q->limits.max_discard_sectors;
	301	else if (op == REQ_OP_WRITE_SAME)
	302	special_cmd_max_sectors = q->limits.max_write_same_sectors;
	303	if ((op == REQ_OP_DISCARD \|\| op == REQ_OP_WRITE_SAME) &&
	304	special_cmd_max_sectors == 0) {
	305	dec_count(io, region, -EOPNOTSUPP);
	306	return;
	307	}
	308
	309	/*
	310	* where->count may be zero if op holds a flush and we need to
	311	* send a zero-sized flush.
	312	*/
	313	do {
	314	/*
	315	* Allocate a suitably sized-bio.
	316	*/
	317	if ((op == REQ_OP_DISCARD) \|\| (op == REQ_OP_WRITE_SAME))
	318	num_bvecs = 1;
	319	else
	320	num_bvecs = min_t(int, BIO_MAX_PAGES,
	321	dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));
	322
	323	bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
	324	bio->bi_iter.bi_sector = where->sector + (where->count - remaining);
	325	bio->bi_bdev = where->bdev;
	326	bio->bi_end_io = endio;
	327	bio_set_op_attrs(bio, op, op_flags);
	328	store_io_and_region_in_bio(bio, io, region);
	329
	330	if (op == REQ_OP_DISCARD) {
	331	num_sectors = min_t(sector_t, special_cmd_max_sectors, remaining);
	332	bio->bi_iter.bi_size = num_sectors << SECTOR_SHIFT;
	333	remaining -= num_sectors;
	334	} else if (op == REQ_OP_WRITE_SAME) {
	335	/*
	336	* WRITE SAME only uses a single page.
	337	*/
	338	dp->get_page(dp, &page, &len, &offset);
	339	bio_add_page(bio, page, logical_block_size, offset);
	340	num_sectors = min_t(sector_t, special_cmd_max_sectors, remaining);
	341	bio->bi_iter.bi_size = num_sectors << SECTOR_SHIFT;
	342
	343	offset = 0;
	344	remaining -= num_sectors;
	345	dp->next_page(dp);
	346	} else while (remaining) {
	347	/*
	348	* Try and add as many pages as possible.
	349	*/
	350	dp->get_page(dp, &page, &len, &offset);
	351	len = min(len, to_bytes(remaining));
	352	if (!bio_add_page(bio, page, len, offset))
	353	break;
	354
	355	offset = 0;
	356	remaining -= to_sector(len);
	357	dp->next_page(dp);
	358	}
	359
	360	atomic_inc(&io->count);
	361	submit_bio(bio);
	362	} while (remaining);
	363	}
	364
	365	static void dispatch_io(int op, int op_flags, unsigned int num_regions,
	366	struct dm_io_region where, struct dpages dp,
	367	struct io *io, int sync)
	368	{
	369	int i;
	370	struct dpages old_pages = *dp;
	371
	372	BUG_ON(num_regions > DM_IO_MAX_REGIONS);
	373
	374	if (sync)
	375	op_flags \|= REQ_SYNC;
	376
	377	/*
	378	* For multiple regions we need to be careful to rewind
	379	* the dp object for each call to do_region.
	380	*/
	381	for (i = 0; i < num_regions; i++) {
	382	*dp = old_pages;
	383	if (where[i].count \|\| (op_flags & REQ_PREFLUSH))
	384	do_region(op, op_flags, i, where + i, dp, io);
	385	}
	386
	387	/*
	388	* Drop the extra reference that we were holding to avoid
	389	* the io being completed too early.
	390	*/
	391	dec_count(io, 0, 0);
	392	}
	393
	394	struct sync_io {
	395	unsigned long error_bits;
	396	struct completion wait;
	397	};
	398
	399	static void sync_io_complete(unsigned long error, void *context)
	400	{
	401	struct sync_io *sio = context;
	402
	403	sio->error_bits = error;
	404	complete(&sio->wait);
	405	}
	406
	407	static int sync_io(struct dm_io_client *client, unsigned int num_regions,
	408	struct dm_io_region *where, int op, int op_flags,
	409	struct dpages dp, unsigned long error_bits)
	410	{
	411	struct io *io;
	412	struct sync_io sio;
	413
	414	if (num_regions > 1 && !op_is_write(op)) {
	415	WARN_ON(1);
	416	return -EIO;
	417	}
	418
	419	init_completion(&sio.wait);
	420
	421	io = mempool_alloc(client->pool, GFP_NOIO);
	422	io->error_bits = 0;
	423	atomic_set(&io->count, 1); /* see dispatch_io() */
	424	io->client = client;
	425	io->callback = sync_io_complete;
	426	io->context = &sio;
	427
	428	io->vma_invalidate_address = dp->vma_invalidate_address;
	429	io->vma_invalidate_size = dp->vma_invalidate_size;
	430
	431	dispatch_io(op, op_flags, num_regions, where, dp, io, 1);
	432
	433	wait_for_completion_io(&sio.wait);
	434
	435	if (error_bits)
	436	*error_bits = sio.error_bits;
	437
	438	return sio.error_bits ? -EIO : 0;
	439	}
	440
	441	static int async_io(struct dm_io_client *client, unsigned int num_regions,
	442	struct dm_io_region *where, int op, int op_flags,
	443	struct dpages dp, io_notify_fn fn, void context)
	444	{
	445	struct io *io;
	446
	447	if (num_regions > 1 && !op_is_write(op)) {
	448	WARN_ON(1);
	449	fn(1, context);
	450	return -EIO;
	451	}
	452
	453	io = mempool_alloc(client->pool, GFP_NOIO);
	454	io->error_bits = 0;
	455	atomic_set(&io->count, 1); /* see dispatch_io() */
	456	io->client = client;
	457	io->callback = fn;
	458	io->context = context;
	459
	460	io->vma_invalidate_address = dp->vma_invalidate_address;
	461	io->vma_invalidate_size = dp->vma_invalidate_size;
	462
	463	dispatch_io(op, op_flags, num_regions, where, dp, io, 0);
	464	return 0;
	465	}
	466
	467	static int dp_init(struct dm_io_request io_req, struct dpages dp,
	468	unsigned long size)
	469	{
	470	/* Set up dpages based on memory type */
	471
	472	dp->vma_invalidate_address = NULL;
	473	dp->vma_invalidate_size = 0;
	474
	475	switch (io_req->mem.type) {
	476	case DM_IO_PAGE_LIST:
	477	list_dp_init(dp, io_req->mem.ptr.pl, io_req->mem.offset);
	478	break;
	479
	480	case DM_IO_BIO:
	481	bio_dp_init(dp, io_req->mem.ptr.bio);
	482	break;
	483
	484	case DM_IO_VMA:
	485	flush_kernel_vmap_range(io_req->mem.ptr.vma, size);
	486	if (io_req->bi_op == REQ_OP_READ) {
	487	dp->vma_invalidate_address = io_req->mem.ptr.vma;
	488	dp->vma_invalidate_size = size;
	489	}
	490	vm_dp_init(dp, io_req->mem.ptr.vma);
	491	break;
	492
	493	case DM_IO_KMEM:
	494	km_dp_init(dp, io_req->mem.ptr.addr);
	495	break;
	496
	497	default:
	498	return -EINVAL;
	499	}
	500
	501	return 0;
	502	}
	503
	504	/*
	505	* New collapsed (a)synchronous interface.
	506	*
	507	* If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
	508	* the queue with blk_unplug() some time later or set REQ_SYNC in io_req->bi_rw.
	509	* If you fail to do one of these, the IO will be submitted to the disk after
	510	* q->unplug_delay, which defaults to 3ms in blk-settings.c.
	511	*/
	512	int dm_io(struct dm_io_request *io_req, unsigned num_regions,
	513	struct dm_io_region where, unsigned long sync_error_bits)
	514	{
	515	int r;
	516	struct dpages dp;
	517
	518	r = dp_init(io_req, &dp, (unsigned long)where->count << SECTOR_SHIFT);
	519	if (r)
	520	return r;
	521
	522	if (!io_req->notify.fn)
	523	return sync_io(io_req->client, num_regions, where,
	524	io_req->bi_op, io_req->bi_op_flags, &dp,
	525	sync_error_bits);
	526
	527	return async_io(io_req->client, num_regions, where, io_req->bi_op,
	528	io_req->bi_op_flags, &dp, io_req->notify.fn,
	529	io_req->notify.context);
	530	}
	531	EXPORT_SYMBOL(dm_io);
	532
	533	int __init dm_io_init(void)
	534	{
	535	_dm_io_cache = KMEM_CACHE(io, 0);
	536	if (!_dm_io_cache)
	537	return -ENOMEM;
	538
	539	return 0;
	540	}
	541
	542	void dm_io_exit(void)
	543	{
	544	kmem_cache_destroy(_dm_io_cache);
	545	_dm_io_cache = NULL;
	546	}