[linux-block.git] / drivers / md / dm-ebs-target.c

/*
 * Copyright (C) 2020 Red Hat GmbH
 *
 * This file is released under the GPL.
 *
 * Device-mapper target to emulate smaller logical block
 * size on backing devices exposing (natively) larger ones.
 *
 * E.g. 512 byte sector emulation on 4K native disks.
 */

#include "dm.h"
#include <linux/module.h>
#include <linux/workqueue.h>
#include <linux/dm-bufio.h>

#define DM_MSG_PREFIX "ebs"

static void ebs_dtr(struct dm_target *ti);

/* Emulated block size context. */
struct ebs_c {
	struct dm_dev *dev;		/* Underlying device to emulate block size on. */
	struct dm_bufio_client *bufio;	/* Use dm-bufio for read and read-modify-write processing. */
	struct workqueue_struct *wq;	/* Workqueue for ^ processing of bios. */
	struct work_struct ws;		/* Work item used for ^. */
	struct bio_list bios_in;	/* Worker bios input list. */
	spinlock_t lock;		/* Guard bios input list above. */
	sector_t start;			/* <start> table line argument, see ebs_ctr below. */
	unsigned int e_bs;		/* Emulated block size in sectors exposed to upper layer. */
	unsigned int u_bs;		/* Underlying block size in sectors retrieved from/set on lower layer device. */
	unsigned char block_shift;	/* bitshift sectors -> blocks used in dm-bufio API. */
	bool u_bs_set:1;		/* Flag to indicate underlying block size is set on table line. */
};

static inline sector_t __sector_to_block(struct ebs_c *ec, sector_t sector)
{
	return sector >> ec->block_shift;
}

static inline sector_t __block_mod(sector_t sector, unsigned int bs)
{
	return sector & (bs - 1);
}

/* Return number of blocks for a bio, accounting for misalignment of start and end sectors. */
static inline unsigned int __nr_blocks(struct ebs_c *ec, struct bio *bio)
{
	sector_t end_sector = __block_mod(bio->bi_iter.bi_sector, ec->u_bs) + bio_sectors(bio);

	return __sector_to_block(ec, end_sector) + (__block_mod(end_sector, ec->u_bs) ? 1 : 0);
}

static inline bool __ebs_check_bs(unsigned int bs)
{
	return bs && is_power_of_2(bs);
}

/*
 * READ/WRITE:
 *
 * copy blocks between bufio blocks and bio vector's (partial/overlapping) pages.
 */
static int __ebs_rw_bvec(struct ebs_c *ec, int rw, struct bio_vec *bv, struct bvec_iter *iter)
{
	int r = 0;
	unsigned char *ba, *pa;
	unsigned int cur_len;
	unsigned int bv_len = bv->bv_len;
	unsigned int buf_off = to_bytes(__block_mod(iter->bi_sector, ec->u_bs));
	sector_t block = __sector_to_block(ec, iter->bi_sector);
	struct dm_buffer *b;

	if (unlikely(!bv->bv_page || !bv_len))
		return -EIO;

	pa = bvec_virt(bv);

	/* Handle overlapping page <-> blocks */
	while (bv_len) {
		cur_len = min(dm_bufio_get_block_size(ec->bufio) - buf_off, bv_len);

		/* Avoid reading for writes in case bio vector's page overwrites block completely. */
		if (rw == READ || buf_off || bv_len < dm_bufio_get_block_size(ec->bufio))
			ba = dm_bufio_read(ec->bufio, block, &b);
		else
			ba = dm_bufio_new(ec->bufio, block, &b);

		if (IS_ERR(ba)) {
			/*
			 * Carry on with next buffer, if any, to issue all possible
			 * data but return error.
			 */
			r = PTR_ERR(ba);
		} else {
			/* Copy data to/from bio to buffer if read/new was successful above. */
			ba += buf_off;
			if (rw == READ) {
				memcpy(pa, ba, cur_len);
				flush_dcache_page(bv->bv_page);
			} else {
				flush_dcache_page(bv->bv_page);
				memcpy(ba, pa, cur_len);
				dm_bufio_mark_partial_buffer_dirty(b, buf_off, buf_off + cur_len);
			}

			dm_bufio_release(b);
		}

		pa += cur_len;
		bv_len -= cur_len;
		buf_off = 0;
		block++;
	}

	return r;
}

/* READ/WRITE: iterate bio vector's copying between (partial) pages and bufio blocks. */
static int __ebs_rw_bio(struct ebs_c *ec, int rw, struct bio *bio)
{
	int r = 0, rr;
	struct bio_vec bv;
	struct bvec_iter iter;

	bio_for_each_bvec(bv, bio, iter) {
		rr = __ebs_rw_bvec(ec, rw, &bv, &iter);
		if (rr)
			r = rr;
	}

	return r;
}

/*
 * Discard bio's blocks, i.e. pass discards down.
 *
 * Avoid discarding partial blocks at beginning and end;
 * return 0 in case no blocks can be discarded as a result.
 */
static int __ebs_discard_bio(struct ebs_c *ec, struct bio *bio)
{
	sector_t block, blocks, sector = bio->bi_iter.bi_sector;

	block = __sector_to_block(ec, sector);
	blocks = __nr_blocks(ec, bio);

	/*
	 * Partial first underlying block (__nr_blocks() may have
	 * resulted in one block).
	 */
	if (__block_mod(sector, ec->u_bs)) {
		block++;
		blocks--;
	}

	/* Partial last underlying block if any. */
	if (blocks && __block_mod(bio_end_sector(bio), ec->u_bs))
		blocks--;

	return blocks ? dm_bufio_issue_discard(ec->bufio, block, blocks) : 0;
}

/* Release blocks them from the bufio cache. */
static void __ebs_forget_bio(struct ebs_c *ec, struct bio *bio)
{
	sector_t blocks, sector = bio->bi_iter.bi_sector;

	blocks = __nr_blocks(ec, bio);

	dm_bufio_forget_buffers(ec->bufio, __sector_to_block(ec, sector), blocks);
}

/* Worker function to process incoming bios. */
static void __ebs_process_bios(struct work_struct *ws)
{
	int r;
	bool write = false;
	sector_t block1, block2;
	struct ebs_c *ec = container_of(ws, struct ebs_c, ws);
	struct bio *bio;
	struct bio_list bios;

	bio_list_init(&bios);

	spin_lock_irq(&ec->lock);
	bios = ec->bios_in;
	bio_list_init(&ec->bios_in);
	spin_unlock_irq(&ec->lock);

	/* Prefetch all read and any mis-aligned write buffers */
	bio_list_for_each(bio, &bios) {
		block1 = __sector_to_block(ec, bio->bi_iter.bi_sector);
		if (bio_op(bio) == REQ_OP_READ)
			dm_bufio_prefetch(ec->bufio, block1, __nr_blocks(ec, bio));
		else if (bio_op(bio) == REQ_OP_WRITE && !(bio->bi_opf & REQ_PREFLUSH)) {
			block2 = __sector_to_block(ec, bio_end_sector(bio));
			if (__block_mod(bio->bi_iter.bi_sector, ec->u_bs))
				dm_bufio_prefetch(ec->bufio, block1, 1);
			if (__block_mod(bio_end_sector(bio), ec->u_bs) && block2 != block1)
				dm_bufio_prefetch(ec->bufio, block2, 1);
		}
	}

	bio_list_for_each(bio, &bios) {
		r = -EIO;
		if (bio_op(bio) == REQ_OP_READ)
			r = __ebs_rw_bio(ec, READ, bio);
		else if (bio_op(bio) == REQ_OP_WRITE) {
			write = true;
			r = __ebs_rw_bio(ec, WRITE, bio);
		} else if (bio_op(bio) == REQ_OP_DISCARD) {
			__ebs_forget_bio(ec, bio);
			r = __ebs_discard_bio(ec, bio);
		}

		if (r < 0)
			bio->bi_status = errno_to_blk_status(r);
	}

	/*
	 * We write dirty buffers after processing I/O on them
	 * but before we endio thus addressing REQ_FUA/REQ_SYNC.
	 */
	r = write ? dm_bufio_write_dirty_buffers(ec->bufio) : 0;

	while ((bio = bio_list_pop(&bios))) {
		/* Any other request is endioed. */
		if (unlikely(r && bio_op(bio) == REQ_OP_WRITE))
			bio_io_error(bio);
		else
			bio_endio(bio);
	}
}

/*
 * Construct an emulated block size mapping: <dev_path> <offset> <ebs> [<ubs>]
 *
 * <dev_path>: path of the underlying device
 * <offset>: offset in 512 bytes sectors into <dev_path>
 * <ebs>: emulated block size in units of 512 bytes exposed to the upper layer
 * [<ubs>]: underlying block size in units of 512 bytes imposed on the lower layer;
 * 	    optional, if not supplied, retrieve logical block size from underlying device
 */
static int ebs_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
	int r;
	unsigned short tmp1;
	unsigned long long tmp;
	char dummy;
	struct ebs_c *ec;

	if (argc < 3 || argc > 4) {
		ti->error = "Invalid argument count";
		return -EINVAL;
	}

	ec = ti->private = kzalloc(sizeof(*ec), GFP_KERNEL);
	if (!ec) {
		ti->error = "Cannot allocate ebs context";
		return -ENOMEM;
	}

	r = -EINVAL;
	if (sscanf(argv[1], "%llu%c", &tmp, &dummy) != 1 ||
	    tmp != (sector_t)tmp ||
	    (sector_t)tmp >= ti->len) {
		ti->error = "Invalid device offset sector";
		goto bad;
	}
	ec->start = tmp;

	if (sscanf(argv[2], "%hu%c", &tmp1, &dummy) != 1 ||
	    !__ebs_check_bs(tmp1) ||
	    to_bytes(tmp1) > PAGE_SIZE) {
		ti->error = "Invalid emulated block size";
		goto bad;
	}
	ec->e_bs = tmp1;

	if (argc > 3) {
		if (sscanf(argv[3], "%hu%c", &tmp1, &dummy) != 1 || !__ebs_check_bs(tmp1)) {
			ti->error = "Invalid underlying block size";
			goto bad;
		}
		ec->u_bs = tmp1;
		ec->u_bs_set = true;
	} else
		ec->u_bs_set = false;

	r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &ec->dev);
	if (r) {
		ti->error = "Device lookup failed";
		ec->dev = NULL;
		goto bad;
	}

	r = -EINVAL;
	if (!ec->u_bs_set) {
		ec->u_bs = to_sector(bdev_logical_block_size(ec->dev->bdev));
		if (!__ebs_check_bs(ec->u_bs)) {
			ti->error = "Invalid retrieved underlying block size";
			goto bad;
		}
	}

	if (!ec->u_bs_set && ec->e_bs == ec->u_bs)
		DMINFO("Emulation superfluous: emulated equal to underlying block size");

	if (__block_mod(ec->start, ec->u_bs)) {
		ti->error = "Device offset must be multiple of underlying block size";
		goto bad;
	}

	ec->bufio = dm_bufio_client_create(ec->dev->bdev, to_bytes(ec->u_bs), 1, 0, NULL, NULL);
	if (IS_ERR(ec->bufio)) {
		ti->error = "Cannot create dm bufio client";
		r = PTR_ERR(ec->bufio);
		ec->bufio = NULL;
		goto bad;
	}

	ec->wq = alloc_ordered_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM);
	if (!ec->wq) {
		ti->error = "Cannot create dm-" DM_MSG_PREFIX " workqueue";
		r = -ENOMEM;
		goto bad;
	}

	ec->block_shift = __ffs(ec->u_bs);
	INIT_WORK(&ec->ws, &__ebs_process_bios);
	bio_list_init(&ec->bios_in);
	spin_lock_init(&ec->lock);

	ti->num_flush_bios = 1;
	ti->num_discard_bios = 1;
	ti->num_secure_erase_bios = 0;
	ti->num_write_same_bios = 0;
	ti->num_write_zeroes_bios = 0;
	return 0;
bad:
	ebs_dtr(ti);
	return r;
}

static void ebs_dtr(struct dm_target *ti)
{
	struct ebs_c *ec = ti->private;

	if (ec->wq)
		destroy_workqueue(ec->wq);
	if (ec->bufio)
		dm_bufio_client_destroy(ec->bufio);
	if (ec->dev)
		dm_put_device(ti, ec->dev);
	kfree(ec);
}

static int ebs_map(struct dm_target *ti, struct bio *bio)
{
	struct ebs_c *ec = ti->private;

	bio_set_dev(bio, ec->dev->bdev);
	bio->bi_iter.bi_sector = ec->start + dm_target_offset(ti, bio->bi_iter.bi_sector);

	if (unlikely(bio_op(bio) == REQ_OP_FLUSH))
		return DM_MAPIO_REMAPPED;
	/*
	 * Only queue for bufio processing in case of partial or overlapping buffers
	 * -or-
	 * emulation with ebs == ubs aiming for tests of dm-bufio overhead.
	 */
	if (likely(__block_mod(bio->bi_iter.bi_sector, ec->u_bs) ||
		   __block_mod(bio_end_sector(bio), ec->u_bs) ||
		   ec->e_bs == ec->u_bs)) {
		spin_lock_irq(&ec->lock);
		bio_list_add(&ec->bios_in, bio);
		spin_unlock_irq(&ec->lock);

		queue_work(ec->wq, &ec->ws);

		return DM_MAPIO_SUBMITTED;
	}

	/* Forget any buffer content relative to this direct backing device I/O. */
	__ebs_forget_bio(ec, bio);

	return DM_MAPIO_REMAPPED;
}

static void ebs_status(struct dm_target *ti, status_type_t type,
		       unsigned status_flags, char *result, unsigned maxlen)
{
	struct ebs_c *ec = ti->private;

	switch (type) {
	case STATUSTYPE_INFO:
		*result = '\0';
		break;
	case STATUSTYPE_TABLE:
		snprintf(result, maxlen, ec->u_bs_set ? "%s %llu %u %u" : "%s %llu %u",
			 ec->dev->name, (unsigned long long) ec->start, ec->e_bs, ec->u_bs);
		break;
	case STATUSTYPE_IMA:
		*result = '\0';
		break;
	}
}

static int ebs_prepare_ioctl(struct dm_target *ti, struct block_device **bdev)
{
	struct ebs_c *ec = ti->private;
	struct dm_dev *dev = ec->dev;

	/*
	 * Only pass ioctls through if the device sizes match exactly.
	 */
	*bdev = dev->bdev;
	return !!(ec->start || ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT);
}

static void ebs_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
	struct ebs_c *ec = ti->private;

	limits->logical_block_size = to_bytes(ec->e_bs);
	limits->physical_block_size = to_bytes(ec->u_bs);
	limits->alignment_offset = limits->physical_block_size;
	blk_limits_io_min(limits, limits->logical_block_size);
}

static int ebs_iterate_devices(struct dm_target *ti,
				  iterate_devices_callout_fn fn, void *data)
{
	struct ebs_c *ec = ti->private;

	return fn(ti, ec->dev, ec->start, ti->len, data);
}

static struct target_type ebs_target = {
	.name		 = "ebs",
	.version	 = {1, 0, 1},
	.features	 = DM_TARGET_PASSES_INTEGRITY,
	.module		 = THIS_MODULE,
	.ctr		 = ebs_ctr,
	.dtr		 = ebs_dtr,
	.map		 = ebs_map,
	.status		 = ebs_status,
	.io_hints	 = ebs_io_hints,
	.prepare_ioctl	 = ebs_prepare_ioctl,
	.iterate_devices = ebs_iterate_devices,
};

static int __init dm_ebs_init(void)
{
	int r = dm_register_target(&ebs_target);

	if (r < 0)
		DMERR("register failed %d", r);

	return r;
}

static void dm_ebs_exit(void)
{
	dm_unregister_target(&ebs_target);
}

module_init(dm_ebs_init);
module_exit(dm_ebs_exit);

MODULE_AUTHOR("Heinz Mauelshagen <dm-devel@redhat.com>");
MODULE_DESCRIPTION(DM_NAME " emulated block size target");
MODULE_LICENSE("GPL");
Commit	Line	Data
d3c7b35c HM	1	/*
	2	* Copyright (C) 2020 Red Hat GmbH
	3	*
	4	* This file is released under the GPL.
	5	*
	6	* Device-mapper target to emulate smaller logical block
	7	* size on backing devices exposing (natively) larger ones.
	8	*
	9	* E.g. 512 byte sector emulation on 4K native disks.
	10	*/
	11
	12	#include "dm.h"
	13	#include <linux/module.h>
	14	#include <linux/workqueue.h>
	15	#include <linux/dm-bufio.h>
	16
	17	#define DM_MSG_PREFIX "ebs"
	18
	19	static void ebs_dtr(struct dm_target *ti);
	20
	21	/* Emulated block size context. */
	22	struct ebs_c {
	23	struct dm_dev dev; / Underlying device to emulate block size on. */
	24	struct dm_bufio_client bufio; / Use dm-bufio for read and read-modify-write processing. */
	25	struct workqueue_struct wq; / Workqueue for ^ processing of bios. */
	26	struct work_struct ws; /* Work item used for ^. */
	27	struct bio_list bios_in; /* Worker bios input list. */
	28	spinlock_t lock; /* Guard bios input list above. */
	29	sector_t start; /* <start> table line argument, see ebs_ctr below. */
	30	unsigned int e_bs; /* Emulated block size in sectors exposed to upper layer. */
1c72e023	31	unsigned int u_bs; /* Underlying block size in sectors retrieved from/set on lower layer device. */
d3c7b35c HM	32	unsigned char block_shift; /* bitshift sectors -> blocks used in dm-bufio API. */
	33	bool u_bs_set:1; /* Flag to indicate underlying block size is set on table line. */
	34	};
	35
	36	static inline sector_t __sector_to_block(struct ebs_c *ec, sector_t sector)
	37	{
	38	return sector >> ec->block_shift;
	39	}
	40
	41	static inline sector_t __block_mod(sector_t sector, unsigned int bs)
	42	{
	43	return sector & (bs - 1);
	44	}
	45
1c72e023	46	/* Return number of blocks for a bio, accounting for misalignment of start and end sectors. */
d3c7b35c HM	47	static inline unsigned int __nr_blocks(struct ebs_c ec, struct bio bio)
	48	{
	49	sector_t end_sector = __block_mod(bio->bi_iter.bi_sector, ec->u_bs) + bio_sectors(bio);
	50
	51	return __sector_to_block(ec, end_sector) + (__block_mod(end_sector, ec->u_bs) ? 1 : 0);
	52	}
	53
	54	static inline bool __ebs_check_bs(unsigned int bs)
	55	{
	56	return bs && is_power_of_2(bs);
	57	}
	58
	59	/*
	60	* READ/WRITE:
	61	*
	62	* copy blocks between bufio blocks and bio vector's (partial/overlapping) pages.
	63	*/
	64	static int __ebs_rw_bvec(struct ebs_c ec, int rw, struct bio_vec bv, struct bvec_iter *iter)
	65	{
	66	int r = 0;
	67	unsigned char ba, pa;
	68	unsigned int cur_len;
	69	unsigned int bv_len = bv->bv_len;
	70	unsigned int buf_off = to_bytes(__block_mod(iter->bi_sector, ec->u_bs));
	71	sector_t block = __sector_to_block(ec, iter->bi_sector);
	72	struct dm_buffer *b;
	73
	74	if (unlikely(!bv->bv_page \|\| !bv_len))
	75	return -EIO;
	76
3a8ba33b	77	pa = bvec_virt(bv);
d3c7b35c HM	78
	79	/* Handle overlapping page <-> blocks */
	80	while (bv_len) {
	81	cur_len = min(dm_bufio_get_block_size(ec->bufio) - buf_off, bv_len);
	82
	83	/* Avoid reading for writes in case bio vector's page overwrites block completely. */
	84	if (rw == READ \|\| buf_off \|\| bv_len < dm_bufio_get_block_size(ec->bufio))
	85	ba = dm_bufio_read(ec->bufio, block, &b);
	86	else
	87	ba = dm_bufio_new(ec->bufio, block, &b);
	88
52252ade	89	if (IS_ERR(ba)) {
d3c7b35c HM	90	/*
	91	* Carry on with next buffer, if any, to issue all possible
	92	* data but return error.
	93	*/
	94	r = PTR_ERR(ba);
	95	} else {
	96	/* Copy data to/from bio to buffer if read/new was successful above. */
	97	ba += buf_off;
	98	if (rw == READ) {
	99	memcpy(pa, ba, cur_len);
	100	flush_dcache_page(bv->bv_page);
	101	} else {
	102	flush_dcache_page(bv->bv_page);
	103	memcpy(ba, pa, cur_len);
	104	dm_bufio_mark_partial_buffer_dirty(b, buf_off, buf_off + cur_len);
	105	}
	106
	107	dm_bufio_release(b);
	108	}
	109
	110	pa += cur_len;
	111	bv_len -= cur_len;
	112	buf_off = 0;
	113	block++;
	114	}
	115
	116	return r;
	117	}
	118
	119	/* READ/WRITE: iterate bio vector's copying between (partial) pages and bufio blocks. */
	120	static int __ebs_rw_bio(struct ebs_c ec, int rw, struct bio bio)
	121	{
	122	int r = 0, rr;
	123	struct bio_vec bv;
	124	struct bvec_iter iter;
	125
	126	bio_for_each_bvec(bv, bio, iter) {
	127	rr = __ebs_rw_bvec(ec, rw, &bv, &iter);
	128	if (rr)
	129	r = rr;
	130	}
	131
	132	return r;
	133	}
	134
a5089a95 HM	135	/*
	136	* Discard bio's blocks, i.e. pass discards down.
	137	*
	138	* Avoid discarding partial blocks at beginning and end;
	139	* return 0 in case no blocks can be discarded as a result.
	140	*/
	141	static int __ebs_discard_bio(struct ebs_c ec, struct bio bio)
	142	{
	143	sector_t block, blocks, sector = bio->bi_iter.bi_sector;
	144
	145	block = __sector_to_block(ec, sector);
	146	blocks = __nr_blocks(ec, bio);
	147
	148	/*
	149	* Partial first underlying block (__nr_blocks() may have
	150	* resulted in one block).
	151	*/
	152	if (__block_mod(sector, ec->u_bs)) {
	153	block++;
	154	blocks--;
	155	}
	156
	157	/* Partial last underlying block if any. */
	158	if (blocks && __block_mod(bio_end_sector(bio), ec->u_bs))
	159	blocks--;
	160
	161	return blocks ? dm_bufio_issue_discard(ec->bufio, block, blocks) : 0;
	162	}
	163
	164	/* Release blocks them from the bufio cache. */
	165	static void __ebs_forget_bio(struct ebs_c ec, struct bio bio)
d3c7b35c HM	166	{
	167	sector_t blocks, sector = bio->bi_iter.bi_sector;
	168
	169	blocks = __nr_blocks(ec, bio);
334b4fc1 MP	170
334b4fc1 MP	171	dm_bufio_forget_buffers(ec->bufio, __sector_to_block(ec, sector), blocks);
d3c7b35c HM	172	}
d3c7b35c HM	173
1c72e023	174	/* Worker function to process incoming bios. */
d3c7b35c HM	175	static void __ebs_process_bios(struct work_struct *ws)
	176	{
	177	int r;
	178	bool write = false;
	179	sector_t block1, block2;
	180	struct ebs_c *ec = container_of(ws, struct ebs_c, ws);
	181	struct bio *bio;
	182	struct bio_list bios;
	183
	184	bio_list_init(&bios);
	185
	186	spin_lock_irq(&ec->lock);
	187	bios = ec->bios_in;
	188	bio_list_init(&ec->bios_in);
	189	spin_unlock_irq(&ec->lock);
	190
	191	/* Prefetch all read and any mis-aligned write buffers */
	192	bio_list_for_each(bio, &bios) {
	193	block1 = __sector_to_block(ec, bio->bi_iter.bi_sector);
	194	if (bio_op(bio) == REQ_OP_READ)
	195	dm_bufio_prefetch(ec->bufio, block1, __nr_blocks(ec, bio));
	196	else if (bio_op(bio) == REQ_OP_WRITE && !(bio->bi_opf & REQ_PREFLUSH)) {
	197	block2 = __sector_to_block(ec, bio_end_sector(bio));
	198	if (__block_mod(bio->bi_iter.bi_sector, ec->u_bs))
	199	dm_bufio_prefetch(ec->bufio, block1, 1);
	200	if (__block_mod(bio_end_sector(bio), ec->u_bs) && block2 != block1)
	201	dm_bufio_prefetch(ec->bufio, block2, 1);
	202	}
	203	}
	204
	205	bio_list_for_each(bio, &bios) {
	206	r = -EIO;
	207	if (bio_op(bio) == REQ_OP_READ)
	208	r = __ebs_rw_bio(ec, READ, bio);
	209	else if (bio_op(bio) == REQ_OP_WRITE) {
	210	write = true;
	211	r = __ebs_rw_bio(ec, WRITE, bio);
	212	} else if (bio_op(bio) == REQ_OP_DISCARD) {
a5089a95 HM	213	__ebs_forget_bio(ec, bio);
a5089a95 HM	214	r = __ebs_discard_bio(ec, bio);
d3c7b35c HM	215	}
	216
	217	if (r < 0)
	218	bio->bi_status = errno_to_blk_status(r);
	219	}
	220
	221	/*
	222	* We write dirty buffers after processing I/O on them
	223	* but before we endio thus addressing REQ_FUA/REQ_SYNC.
	224	*/
	225	r = write ? dm_bufio_write_dirty_buffers(ec->bufio) : 0;
	226
	227	while ((bio = bio_list_pop(&bios))) {
	228	/* Any other request is endioed. */
	229	if (unlikely(r && bio_op(bio) == REQ_OP_WRITE))
	230	bio_io_error(bio);
	231	else
	232	bio_endio(bio);
	233	}
	234	}
	235
	236	/*
	237	* Construct an emulated block size mapping: <dev_path> <offset> <ebs> [<ubs>]
	238	*
	239	* <dev_path>: path of the underlying device
	240	* <offset>: offset in 512 bytes sectors into <dev_path>
	241	* <ebs>: emulated block size in units of 512 bytes exposed to the upper layer
	242	* [<ubs>]: underlying block size in units of 512 bytes imposed on the lower layer;
	243	* optional, if not supplied, retrieve logical block size from underlying device
	244	*/
	245	static int ebs_ctr(struct dm_target ti, unsigned int argc, char *argv)
	246	{
	247	int r;
	248	unsigned short tmp1;
	249	unsigned long long tmp;
	250	char dummy;
	251	struct ebs_c *ec;
	252
	253	if (argc < 3 \|\| argc > 4) {
	254	ti->error = "Invalid argument count";
	255	return -EINVAL;
	256	}
	257
	258	ec = ti->private = kzalloc(sizeof(*ec), GFP_KERNEL);
	259	if (!ec) {
	260	ti->error = "Cannot allocate ebs context";
	261	return -ENOMEM;
	262	}
	263
	264	r = -EINVAL;
	265	if (sscanf(argv[1], "%llu%c", &tmp, &dummy) != 1 \|\|
	266	tmp != (sector_t)tmp \|\|
	267	(sector_t)tmp >= ti->len) {
	268	ti->error = "Invalid device offset sector";
	269	goto bad;
	270	}
	271	ec->start = tmp;
	272
	273	if (sscanf(argv[2], "%hu%c", &tmp1, &dummy) != 1 \|\|
	274	!__ebs_check_bs(tmp1) \|\|
	275	to_bytes(tmp1) > PAGE_SIZE) {
	276	ti->error = "Invalid emulated block size";
	277	goto bad;
	278	}
279	ec->e_bs = tmp1;
280
281	if (argc > 3) {
282	if (sscanf(argv[3], "%hu%c", &tmp1, &dummy) != 1 \|\| !__ebs_check_bs(tmp1)) {
283	ti->error = "Invalid underlying block size";
284	goto bad;
285	}
286	ec->u_bs = tmp1;
287	ec->u_bs_set = true;
288	} else
289	ec->u_bs_set = false;
290
291	r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &ec->dev);
292	if (r) {
293	ti->error = "Device lookup failed";
294	ec->dev = NULL;
295	goto bad;
296	}
297
298	r = -EINVAL;
299	if (!ec->u_bs_set) {
300	ec->u_bs = to_sector(bdev_logical_block_size(ec->dev->bdev));
301	if (!__ebs_check_bs(ec->u_bs)) {
302	ti->error = "Invalid retrieved underlying block size";
303	goto bad;
304	}
305	}
306
307	if (!ec->u_bs_set && ec->e_bs == ec->u_bs)
308	DMINFO("Emulation superfluous: emulated equal to underlying block size");
309
310	if (__block_mod(ec->start, ec->u_bs)) {
311	ti->error = "Device offset must be multiple of underlying block size";
312	goto bad;
313	}
314
315	ec->bufio = dm_bufio_client_create(ec->dev->bdev, to_bytes(ec->u_bs), 1, 0, NULL, NULL);
316	if (IS_ERR(ec->bufio)) {
317	ti->error = "Cannot create dm bufio client";
318	r = PTR_ERR(ec->bufio);
319	ec->bufio = NULL;
320	goto bad;
321	}
322
323	ec->wq = alloc_ordered_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM);
324	if (!ec->wq) {
325	ti->error = "Cannot create dm-" DM_MSG_PREFIX " workqueue";
326	r = -ENOMEM;
327	goto bad;
328	}
329
330	ec->block_shift = __ffs(ec->u_bs);
331	INIT_WORK(&ec->ws, &__ebs_process_bios);
332	bio_list_init(&ec->bios_in);
333	spin_lock_init(&ec->lock);
334
335	ti->num_flush_bios = 1;
336	ti->num_discard_bios = 1;
337	ti->num_secure_erase_bios = 0;
338	ti->num_write_same_bios = 0;
339	ti->num_write_zeroes_bios = 0;
340	return 0;
341	bad:
342	ebs_dtr(ti);
343	return r;
344	}
345
346	static void ebs_dtr(struct dm_target *ti)
347	{
348	struct ebs_c *ec = ti->private;
349
350	if (ec->wq)
351	destroy_workqueue(ec->wq);
352	if (ec->bufio)
353	dm_bufio_client_destroy(ec->bufio);
354	if (ec->dev)
355	dm_put_device(ti, ec->dev);
356	kfree(ec);
357	}
358
359	static int ebs_map(struct dm_target ti, struct bio bio)
360	{
361	struct ebs_c *ec = ti->private;
362
363	bio_set_dev(bio, ec->dev->bdev);
364	bio->bi_iter.bi_sector = ec->start + dm_target_offset(ti, bio->bi_iter.bi_sector);
365
4cb6f226	366	if (unlikely(bio_op(bio) == REQ_OP_FLUSH))
d3c7b35c HM	367	return DM_MAPIO_REMAPPED;
	368	/*
	369	* Only queue for bufio processing in case of partial or overlapping buffers
	370	* -or-
	371	* emulation with ebs == ubs aiming for tests of dm-bufio overhead.
	372	*/
	373	if (likely(__block_mod(bio->bi_iter.bi_sector, ec->u_bs) \|\|
	374	__block_mod(bio_end_sector(bio), ec->u_bs) \|\|
	375	ec->e_bs == ec->u_bs)) {
	376	spin_lock_irq(&ec->lock);
	377	bio_list_add(&ec->bios_in, bio);
	378	spin_unlock_irq(&ec->lock);
	379
	380	queue_work(ec->wq, &ec->ws);
	381
	382	return DM_MAPIO_SUBMITTED;
	383	}
	384
	385	/* Forget any buffer content relative to this direct backing device I/O. */
	386	__ebs_forget_bio(ec, bio);
	387
	388	return DM_MAPIO_REMAPPED;
	389	}
	390
	391	static void ebs_status(struct dm_target *ti, status_type_t type,
	392	unsigned status_flags, char *result, unsigned maxlen)
	393	{
	394	struct ebs_c *ec = ti->private;
	395
	396	switch (type) {
	397	case STATUSTYPE_INFO:
	398	*result = '\0';
	399	break;
	400	case STATUSTYPE_TABLE:
	401	snprintf(result, maxlen, ec->u_bs_set ? "%s %llu %u %u" : "%s %llu %u",
	402	ec->dev->name, (unsigned long long) ec->start, ec->e_bs, ec->u_bs);
	403	break;
8ec45662 TS	404	case STATUSTYPE_IMA:
	405	*result = '\0';
	406	break;
d3c7b35c HM	407	}
	408	}
	409
	410	static int ebs_prepare_ioctl(struct dm_target ti, struct block_device *bdev)
	411	{
	412	struct ebs_c *ec = ti->private;
	413	struct dm_dev *dev = ec->dev;
	414
	415	/*
	416	* Only pass ioctls through if the device sizes match exactly.
	417	*/
	418	*bdev = dev->bdev;
	419	return !!(ec->start \|\| ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT);
	420	}
	421
	422	static void ebs_io_hints(struct dm_target ti, struct queue_limits limits)
	423	{
	424	struct ebs_c *ec = ti->private;
	425
	426	limits->logical_block_size = to_bytes(ec->e_bs);
	427	limits->physical_block_size = to_bytes(ec->u_bs);
	428	limits->alignment_offset = limits->physical_block_size;
	429	blk_limits_io_min(limits, limits->logical_block_size);
	430	}
	431
	432	static int ebs_iterate_devices(struct dm_target *ti,
	433	iterate_devices_callout_fn fn, void *data)
	434	{
	435	struct ebs_c *ec = ti->private;
	436
	437	return fn(ti, ec->dev, ec->start, ti->len, data);
	438	}
	439
	440	static struct target_type ebs_target = {
	441	.name = "ebs",
a5089a95	442	.version = {1, 0, 1},
d3c7b35c HM	443	.features = DM_TARGET_PASSES_INTEGRITY,
	444	.module = THIS_MODULE,
	445	.ctr = ebs_ctr,
	446	.dtr = ebs_dtr,
	447	.map = ebs_map,
	448	.status = ebs_status,
	449	.io_hints = ebs_io_hints,
	450	.prepare_ioctl = ebs_prepare_ioctl,
	451	.iterate_devices = ebs_iterate_devices,
	452	};
	453
	454	static int __init dm_ebs_init(void)
	455	{
	456	int r = dm_register_target(&ebs_target);
	457
	458	if (r < 0)
	459	DMERR("register failed %d", r);
	460
	461	return r;
	462	}
	463
	464	static void dm_ebs_exit(void)
	465	{
	466	dm_unregister_target(&ebs_target);
	467	}
	468
	469	module_init(dm_ebs_init);
	470	module_exit(dm_ebs_exit);
	471
	472	MODULE_AUTHOR("Heinz Mauelshagen <dm-devel@redhat.com>");
	473	MODULE_DESCRIPTION(DM_NAME " emulated block size target");
	474	MODULE_LICENSE("GPL");