drivers/md/dm-stripe.c - linux - Git at Google

 /*
  * Copyright (C) 2001-2003 Sistina Software (UK) Limited.
  *
  * This file is released under the GPL.
  */

 #include "dm.h"
 #include <linux/device-mapper.h>

 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/blkdev.h>
 #include <linux/bio.h>
 #include <linux/dax.h>
 #include <linux/slab.h>
 #include <linux/log2.h>

 #define DM_MSG_PREFIX "striped"
 #define DM_IO_ERROR_THRESHOLD 15

 struct stripe {
 	struct dm_dev *dev;
 	sector_t physical_start;

 	atomic_t error_count;
 };

 struct stripe_c {
 	uint32_t stripes;
 	int stripes_shift;

 	/* The size of this target / num. stripes */
 	sector_t stripe_width;

 	uint32_t chunk_size;
 	int chunk_size_shift;

 	/* Needed for handling events */
 	struct dm_target *ti;

 	/* Work struct used for triggering events*/
 	struct work_struct trigger_event;

 	struct stripe stripe[];
 };

 /*
  * An event is triggered whenever a drive
  * drops out of a stripe volume.
  */
 static void trigger_event(struct work_struct *work)
 {
 	struct stripe_c *sc = container_of(work, struct stripe_c,
 					   trigger_event);
 	dm_table_event(sc->ti->table);
 }

 /*
  * Parse a single <dev> <sector> pair
  */
 static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
 		      unsigned int stripe, char **argv)
 {
 	unsigned long long start;
 	char dummy;
 	int ret;

 	if (sscanf(argv[1], "%llu%c", &start, &dummy) != 1)
 		return -EINVAL;

 	ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
 			    &sc->stripe[stripe].dev);
 	if (ret)
 		return ret;

 	sc->stripe[stripe].physical_start = start;

 	return 0;
 }

 /*
  * Construct a striped mapping.
  * <number of stripes> <chunk size> [<dev_path> <offset>]+
  */
 static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 {
 	struct stripe_c *sc;
 	sector_t width, tmp_len;
 	uint32_t stripes;
 	uint32_t chunk_size;
 	int r;
 	unsigned int i;

 	if (argc < 2) {
 		ti->error = "Not enough arguments";
 		return -EINVAL;
 	}

 	if (kstrtouint(argv[0], 10, &stripes) || !stripes) {
 		ti->error = "Invalid stripe count";
 		return -EINVAL;
 	}

 	if (kstrtouint(argv[1], 10, &chunk_size) || !chunk_size) {
 		ti->error = "Invalid chunk_size";
 		return -EINVAL;
 	}

 	width = ti->len;
 	if (sector_div(width, stripes)) {
 		ti->error = "Target length not divisible by number of stripes";
 		return -EINVAL;
 	}

 	tmp_len = width;
 	if (sector_div(tmp_len, chunk_size)) {
 		ti->error = "Target length not divisible by chunk size";
 		return -EINVAL;
 	}

 	/*
 	 * Do we have enough arguments for that many stripes ?
 	 */
 	if (argc != (2 + 2 * stripes)) {
 		ti->error = "Not enough destinations specified";
 		return -EINVAL;
 	}

 	sc = kmalloc(struct_size(sc, stripe, stripes), GFP_KERNEL);
 	if (!sc) {
 		ti->error = "Memory allocation for striped context failed";
 		return -ENOMEM;
 	}

 	INIT_WORK(&sc->trigger_event, trigger_event);

 	/* Set pointer to dm target; used in trigger_event */
 	sc->ti = ti;
 	sc->stripes = stripes;
 	sc->stripe_width = width;

 	if (stripes & (stripes - 1))
 		sc->stripes_shift = -1;
 	else
 		sc->stripes_shift = __ffs(stripes);

 	r = dm_set_target_max_io_len(ti, chunk_size);
 	if (r) {
 		kfree(sc);
 		return r;
 	}

 	ti->num_flush_bios = stripes;
 	ti->num_discard_bios = stripes;
 	ti->num_secure_erase_bios = stripes;
 	ti->num_write_zeroes_bios = stripes;

 	sc->chunk_size = chunk_size;
 	if (chunk_size & (chunk_size - 1))
 		sc->chunk_size_shift = -1;
 	else
 		sc->chunk_size_shift = __ffs(chunk_size);

 	/*
 	 * Get the stripe destinations.
 	 */
 	for (i = 0; i < stripes; i++) {
 		argv += 2;

 		r = get_stripe(ti, sc, i, argv);
 		if (r < 0) {
 			ti->error = "Couldn't parse stripe destination";
 			while (i--)
 				dm_put_device(ti, sc->stripe[i].dev);
 			kfree(sc);
 			return r;
 		}
 		atomic_set(&(sc->stripe[i].error_count), 0);
 	}

 	ti->private = sc;

 	return 0;
 }

 static void stripe_dtr(struct dm_target *ti)
 {
 	unsigned int i;
 	struct stripe_c *sc = (struct stripe_c *) ti->private;

 	for (i = 0; i < sc->stripes; i++)
 		dm_put_device(ti, sc->stripe[i].dev);

 	flush_work(&sc->trigger_event);
 	kfree(sc);
 }

 static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
 			      uint32_t *stripe, sector_t *result)
 {
 	sector_t chunk = dm_target_offset(sc->ti, sector);
 	sector_t chunk_offset;

 	if (sc->chunk_size_shift < 0)
 		chunk_offset = sector_div(chunk, sc->chunk_size);
 	else {
 		chunk_offset = chunk & (sc->chunk_size - 1);
 		chunk >>= sc->chunk_size_shift;
 	}

 	if (sc->stripes_shift < 0)
 		*stripe = sector_div(chunk, sc->stripes);
 	else {
 		*stripe = chunk & (sc->stripes - 1);
 		chunk >>= sc->stripes_shift;
 	}

 	if (sc->chunk_size_shift < 0)
 		chunk *= sc->chunk_size;
 	else
 		chunk <<= sc->chunk_size_shift;

 	*result = chunk + chunk_offset;
 }

 static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
 				    uint32_t target_stripe, sector_t *result)
 {
 	uint32_t stripe;

 	stripe_map_sector(sc, sector, &stripe, result);
 	if (stripe == target_stripe)
 		return;

 	/* round down */
 	sector = *result;
 	if (sc->chunk_size_shift < 0)
 		*result -= sector_div(sector, sc->chunk_size);
 	else
 		*result = sector & ~(sector_t)(sc->chunk_size - 1);

 	if (target_stripe < stripe)
 		*result += sc->chunk_size;		/* next chunk */
 }

 static int stripe_map_range(struct stripe_c *sc, struct bio *bio,
 			    uint32_t target_stripe)
 {
 	sector_t begin, end;

 	stripe_map_range_sector(sc, bio->bi_iter.bi_sector,
 				target_stripe, &begin);
 	stripe_map_range_sector(sc, bio_end_sector(bio),
 				target_stripe, &end);
 	if (begin < end) {
 		bio_set_dev(bio, sc->stripe[target_stripe].dev->bdev);
 		bio->bi_iter.bi_sector = begin +
 			sc->stripe[target_stripe].physical_start;
 		bio->bi_iter.bi_size = to_bytes(end - begin);
 		return DM_MAPIO_REMAPPED;
 	} else {
 		/* The range doesn't map to the target stripe */
 		bio_endio(bio);
 		return DM_MAPIO_SUBMITTED;
 	}
 }

 static int stripe_map(struct dm_target *ti, struct bio *bio)
 {
 	struct stripe_c *sc = ti->private;
 	uint32_t stripe;
 	unsigned int target_bio_nr;

 	if (bio->bi_opf & REQ_PREFLUSH) {
 		target_bio_nr = dm_bio_get_target_bio_nr(bio);
 		BUG_ON(target_bio_nr >= sc->stripes);
 		bio_set_dev(bio, sc->stripe[target_bio_nr].dev->bdev);
 		return DM_MAPIO_REMAPPED;
 	}
 	if (unlikely(bio_op(bio) == REQ_OP_DISCARD) ||
 	    unlikely(bio_op(bio) == REQ_OP_SECURE_ERASE) ||
 	    unlikely(bio_op(bio) == REQ_OP_WRITE_ZEROES)) {
 		target_bio_nr = dm_bio_get_target_bio_nr(bio);
 		BUG_ON(target_bio_nr >= sc->stripes);
 		return stripe_map_range(sc, bio, target_bio_nr);
 	}

 	stripe_map_sector(sc, bio->bi_iter.bi_sector,
 			  &stripe, &bio->bi_iter.bi_sector);

 	bio->bi_iter.bi_sector += sc->stripe[stripe].physical_start;
 	bio_set_dev(bio, sc->stripe[stripe].dev->bdev);

 	return DM_MAPIO_REMAPPED;
 }

 #if IS_ENABLED(CONFIG_FS_DAX)
 static struct dax_device *stripe_dax_pgoff(struct dm_target *ti, pgoff_t *pgoff)
 {
 	struct stripe_c *sc = ti->private;
 	struct block_device *bdev;
 	sector_t dev_sector;
 	uint32_t stripe;

 	stripe_map_sector(sc, *pgoff * PAGE_SECTORS, &stripe, &dev_sector);
 	dev_sector += sc->stripe[stripe].physical_start;
 	bdev = sc->stripe[stripe].dev->bdev;

 	*pgoff = (get_start_sect(bdev) + dev_sector) >> PAGE_SECTORS_SHIFT;
 	return sc->stripe[stripe].dev->dax_dev;
 }

 static long stripe_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
 		long nr_pages, enum dax_access_mode mode, void **kaddr,
 		pfn_t *pfn)
 {
 	struct dax_device *dax_dev = stripe_dax_pgoff(ti, &pgoff);

 	return dax_direct_access(dax_dev, pgoff, nr_pages, mode, kaddr, pfn);
 }

 static int stripe_dax_zero_page_range(struct dm_target *ti, pgoff_t pgoff,
 				      size_t nr_pages)
 {
 	struct dax_device *dax_dev = stripe_dax_pgoff(ti, &pgoff);

 	return dax_zero_page_range(dax_dev, pgoff, nr_pages);
 }

 static size_t stripe_dax_recovery_write(struct dm_target *ti, pgoff_t pgoff,
 		void *addr, size_t bytes, struct iov_iter *i)
 {
 	struct dax_device *dax_dev = stripe_dax_pgoff(ti, &pgoff);

 	return dax_recovery_write(dax_dev, pgoff, addr, bytes, i);
 }

 #else
 #define stripe_dax_direct_access NULL
 #define stripe_dax_zero_page_range NULL
 #define stripe_dax_recovery_write NULL
 #endif

 /*
  * Stripe status:
  *
  * INFO
  * #stripes [stripe_name <stripe_name>] [group word count]
  * [error count 'A|D' <error count 'A|D'>]
  *
  * TABLE
  * #stripes [stripe chunk size]
  * [stripe_name physical_start <stripe_name physical_start>]
  *
  */

 static void stripe_status(struct dm_target *ti, status_type_t type,
 			  unsigned int status_flags, char *result, unsigned int maxlen)
 {
 	struct stripe_c *sc = (struct stripe_c *) ti->private;
 	unsigned int sz = 0;
 	unsigned int i;

 	switch (type) {
 	case STATUSTYPE_INFO:
 		DMEMIT("%d ", sc->stripes);
 		for (i = 0; i < sc->stripes; i++)  {
 			DMEMIT("%s ", sc->stripe[i].dev->name);
 		}
 		DMEMIT("1 ");
 		for (i = 0; i < sc->stripes; i++) {
 			DMEMIT("%c", atomic_read(&(sc->stripe[i].error_count)) ?
 			       'D' : 'A');
 		}
 		break;

 	case STATUSTYPE_TABLE:
 		DMEMIT("%d %llu", sc->stripes,
 			(unsigned long long)sc->chunk_size);
 		for (i = 0; i < sc->stripes; i++)
 			DMEMIT(" %s %llu", sc->stripe[i].dev->name,
 			    (unsigned long long)sc->stripe[i].physical_start);
 		break;

 	case STATUSTYPE_IMA:
 		DMEMIT_TARGET_NAME_VERSION(ti->type);
 		DMEMIT(",stripes=%d,chunk_size=%llu", sc->stripes,
 		       (unsigned long long)sc->chunk_size);

 		for (i = 0; i < sc->stripes; i++) {
 			DMEMIT(",stripe_%d_device_name=%s", i, sc->stripe[i].dev->name);
 			DMEMIT(",stripe_%d_physical_start=%llu", i,
 			       (unsigned long long)sc->stripe[i].physical_start);
 			DMEMIT(",stripe_%d_status=%c", i,
 			       atomic_read(&(sc->stripe[i].error_count)) ? 'D' : 'A');
 		}
 		DMEMIT(";");
 		break;
 	}
 }

 static int stripe_end_io(struct dm_target *ti, struct bio *bio,
 		blk_status_t *error)
 {
 	unsigned int i;
 	char major_minor[16];
 	struct stripe_c *sc = ti->private;

 	if (!*error)
 		return DM_ENDIO_DONE; /* I/O complete */

 	if (bio->bi_opf & REQ_RAHEAD)
 		return DM_ENDIO_DONE;

 	if (*error == BLK_STS_NOTSUPP)
 		return DM_ENDIO_DONE;

 	memset(major_minor, 0, sizeof(major_minor));
 	sprintf(major_minor, "%d:%d", MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)));

 	/*
 	 * Test to see which stripe drive triggered the event
 	 * and increment error count for all stripes on that device.
 	 * If the error count for a given device exceeds the threshold
 	 * value we will no longer trigger any further events.
 	 */
 	for (i = 0; i < sc->stripes; i++)
 		if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
 			atomic_inc(&(sc->stripe[i].error_count));
 			if (atomic_read(&(sc->stripe[i].error_count)) <
 			    DM_IO_ERROR_THRESHOLD)
 				schedule_work(&sc->trigger_event);
 		}

 	return DM_ENDIO_DONE;
 }

 static int stripe_iterate_devices(struct dm_target *ti,
 				  iterate_devices_callout_fn fn, void *data)
 {
 	struct stripe_c *sc = ti->private;
 	int ret = 0;
 	unsigned int i = 0;

 	do {
 		ret = fn(ti, sc->stripe[i].dev,
 			 sc->stripe[i].physical_start,
 			 sc->stripe_width, data);
 	} while (!ret && ++i < sc->stripes);

 	return ret;
 }

 static void stripe_io_hints(struct dm_target *ti,
 			    struct queue_limits *limits)
 {
 	struct stripe_c *sc = ti->private;
 	unsigned int chunk_size = sc->chunk_size << SECTOR_SHIFT;

 	blk_limits_io_min(limits, chunk_size);
 	blk_limits_io_opt(limits, chunk_size * sc->stripes);
 }

 static struct target_type stripe_target = {
 	.name   = "striped",
 	.version = {1, 6, 0},
 	.features = DM_TARGET_PASSES_INTEGRITY | DM_TARGET_NOWAIT,
 	.module = THIS_MODULE,
 	.ctr    = stripe_ctr,
 	.dtr    = stripe_dtr,
 	.map    = stripe_map,
 	.end_io = stripe_end_io,
 	.status = stripe_status,
 	.iterate_devices = stripe_iterate_devices,
 	.io_hints = stripe_io_hints,
 	.direct_access = stripe_dax_direct_access,
 	.dax_zero_page_range = stripe_dax_zero_page_range,
 	.dax_recovery_write = stripe_dax_recovery_write,
 };

 int __init dm_stripe_init(void)
 {
 	int r;

 	r = dm_register_target(&stripe_target);
 	if (r < 0)
 		DMWARN("target registration failed");

 	return r;
 }

 void dm_stripe_exit(void)
 {
 	dm_unregister_target(&stripe_target);
 }
	/*
	* Copyright (C) 2001-2003 Sistina Software (UK) Limited.
	*
	* This file is released under the GPL.
	*/

	#include "dm.h"
	#include <linux/device-mapper.h>

	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/blkdev.h>
	#include <linux/bio.h>
	#include <linux/dax.h>
	#include <linux/slab.h>
	#include <linux/log2.h>

	#define DM_MSG_PREFIX "striped"
	#define DM_IO_ERROR_THRESHOLD 15

	struct stripe {
	struct dm_dev *dev;
	sector_t physical_start;

	atomic_t error_count;
	};

	struct stripe_c {
	uint32_t stripes;
	int stripes_shift;

	/* The size of this target / num. stripes */
	sector_t stripe_width;

	uint32_t chunk_size;
	int chunk_size_shift;

	/* Needed for handling events */
	struct dm_target *ti;

	/* Work struct used for triggering events*/
	struct work_struct trigger_event;

	struct stripe stripe[];
	};

	/*
	* An event is triggered whenever a drive
	* drops out of a stripe volume.
	*/
	static void trigger_event(struct work_struct *work)
	{
	struct stripe_c *sc = container_of(work, struct stripe_c,
	trigger_event);
	dm_table_event(sc->ti->table);
	}

	/*
	* Parse a single <dev> <sector> pair
	*/
	static int get_stripe(struct dm_target ti, struct stripe_c sc,
	unsigned int stripe, char **argv)
	{
	unsigned long long start;
	char dummy;
	int ret;

	if (sscanf(argv[1], "%llu%c", &start, &dummy) != 1)
	return -EINVAL;

	ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
	&sc->stripe[stripe].dev);
	if (ret)
	return ret;

	sc->stripe[stripe].physical_start = start;

	return 0;
	}

	/*
	* Construct a striped mapping.
	* <number of stripes> <chunk size> [<dev_path> <offset>]+
	*/
	static int stripe_ctr(struct dm_target ti, unsigned int argc, char *argv)
	{
	struct stripe_c *sc;
	sector_t width, tmp_len;
	uint32_t stripes;
	uint32_t chunk_size;
	int r;
	unsigned int i;

	if (argc < 2) {
	ti->error = "Not enough arguments";
	return -EINVAL;
	}

	if (kstrtouint(argv[0], 10, &stripes) \|\| !stripes) {
	ti->error = "Invalid stripe count";
	return -EINVAL;
	}

	if (kstrtouint(argv[1], 10, &chunk_size) \|\| !chunk_size) {
	ti->error = "Invalid chunk_size";
	return -EINVAL;
	}

	width = ti->len;
	if (sector_div(width, stripes)) {
	ti->error = "Target length not divisible by number of stripes";
	return -EINVAL;
	}

	tmp_len = width;
	if (sector_div(tmp_len, chunk_size)) {
	ti->error = "Target length not divisible by chunk size";
	return -EINVAL;
	}

	/*
	* Do we have enough arguments for that many stripes ?
	*/
	if (argc != (2 + 2 * stripes)) {
	ti->error = "Not enough destinations specified";
	return -EINVAL;
	}

	sc = kmalloc(struct_size(sc, stripe, stripes), GFP_KERNEL);
	if (!sc) {
	ti->error = "Memory allocation for striped context failed";
	return -ENOMEM;
	}

	INIT_WORK(&sc->trigger_event, trigger_event);

	/* Set pointer to dm target; used in trigger_event */
	sc->ti = ti;
	sc->stripes = stripes;
	sc->stripe_width = width;

	if (stripes & (stripes - 1))
	sc->stripes_shift = -1;
	else
	sc->stripes_shift = __ffs(stripes);

	r = dm_set_target_max_io_len(ti, chunk_size);
	if (r) {
	kfree(sc);
	return r;
	}

	ti->num_flush_bios = stripes;
	ti->num_discard_bios = stripes;
	ti->num_secure_erase_bios = stripes;
	ti->num_write_zeroes_bios = stripes;

	sc->chunk_size = chunk_size;
	if (chunk_size & (chunk_size - 1))
	sc->chunk_size_shift = -1;
	else
	sc->chunk_size_shift = __ffs(chunk_size);

	/*
	* Get the stripe destinations.
	*/
	for (i = 0; i < stripes; i++) {
	argv += 2;

	r = get_stripe(ti, sc, i, argv);
	if (r < 0) {
	ti->error = "Couldn't parse stripe destination";
	while (i--)
	dm_put_device(ti, sc->stripe[i].dev);
	kfree(sc);
	return r;
	}
	atomic_set(&(sc->stripe[i].error_count), 0);
	}

	ti->private = sc;

	return 0;
	}

	static void stripe_dtr(struct dm_target *ti)
	{
	unsigned int i;
	struct stripe_c sc = (struct stripe_c ) ti->private;

	for (i = 0; i < sc->stripes; i++)
	dm_put_device(ti, sc->stripe[i].dev);

	flush_work(&sc->trigger_event);
	kfree(sc);
	}

	static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
	uint32_t stripe, sector_t result)
	{
	sector_t chunk = dm_target_offset(sc->ti, sector);
	sector_t chunk_offset;

	if (sc->chunk_size_shift < 0)
	chunk_offset = sector_div(chunk, sc->chunk_size);
	else {
	chunk_offset = chunk & (sc->chunk_size - 1);
	chunk >>= sc->chunk_size_shift;
	}

	if (sc->stripes_shift < 0)
	*stripe = sector_div(chunk, sc->stripes);
	else {
	*stripe = chunk & (sc->stripes - 1);
	chunk >>= sc->stripes_shift;
	}

	if (sc->chunk_size_shift < 0)
	chunk *= sc->chunk_size;
	else
	chunk <<= sc->chunk_size_shift;

	*result = chunk + chunk_offset;
	}

	static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
	uint32_t target_stripe, sector_t *result)
	{
	uint32_t stripe;

	stripe_map_sector(sc, sector, &stripe, result);
	if (stripe == target_stripe)
	return;

	/* round down */
	sector = *result;
	if (sc->chunk_size_shift < 0)
	*result -= sector_div(sector, sc->chunk_size);
	else
	*result = sector & ~(sector_t)(sc->chunk_size - 1);

	if (target_stripe < stripe)
	result += sc->chunk_size; / next chunk */
	}

	static int stripe_map_range(struct stripe_c sc, struct bio bio,
	uint32_t target_stripe)
	{
	sector_t begin, end;

	stripe_map_range_sector(sc, bio->bi_iter.bi_sector,
	target_stripe, &begin);
	stripe_map_range_sector(sc, bio_end_sector(bio),
	target_stripe, &end);
	if (begin < end) {
	bio_set_dev(bio, sc->stripe[target_stripe].dev->bdev);
	bio->bi_iter.bi_sector = begin +
	sc->stripe[target_stripe].physical_start;
	bio->bi_iter.bi_size = to_bytes(end - begin);
	return DM_MAPIO_REMAPPED;
	} else {
	/* The range doesn't map to the target stripe */
	bio_endio(bio);
	return DM_MAPIO_SUBMITTED;
	}
	}

	static int stripe_map(struct dm_target ti, struct bio bio)
	{
	struct stripe_c *sc = ti->private;
	uint32_t stripe;
	unsigned int target_bio_nr;

	if (bio->bi_opf & REQ_PREFLUSH) {
	target_bio_nr = dm_bio_get_target_bio_nr(bio);
	BUG_ON(target_bio_nr >= sc->stripes);
	bio_set_dev(bio, sc->stripe[target_bio_nr].dev->bdev);
	return DM_MAPIO_REMAPPED;
	}
	if (unlikely(bio_op(bio) == REQ_OP_DISCARD) \|\|
	unlikely(bio_op(bio) == REQ_OP_SECURE_ERASE) \|\|
	unlikely(bio_op(bio) == REQ_OP_WRITE_ZEROES)) {
	target_bio_nr = dm_bio_get_target_bio_nr(bio);
	BUG_ON(target_bio_nr >= sc->stripes);
	return stripe_map_range(sc, bio, target_bio_nr);
	}

	stripe_map_sector(sc, bio->bi_iter.bi_sector,
	&stripe, &bio->bi_iter.bi_sector);

	bio->bi_iter.bi_sector += sc->stripe[stripe].physical_start;
	bio_set_dev(bio, sc->stripe[stripe].dev->bdev);

	return DM_MAPIO_REMAPPED;
	}

	#if IS_ENABLED(CONFIG_FS_DAX)
	static struct dax_device stripe_dax_pgoff(struct dm_target ti, pgoff_t *pgoff)
	{
	struct stripe_c *sc = ti->private;
	struct block_device *bdev;
	sector_t dev_sector;
	uint32_t stripe;

	stripe_map_sector(sc, pgoff PAGE_SECTORS, &stripe, &dev_sector);
	dev_sector += sc->stripe[stripe].physical_start;
	bdev = sc->stripe[stripe].dev->bdev;

	*pgoff = (get_start_sect(bdev) + dev_sector) >> PAGE_SECTORS_SHIFT;
	return sc->stripe[stripe].dev->dax_dev;
	}

	static long stripe_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
	long nr_pages, enum dax_access_mode mode, void **kaddr,
	pfn_t *pfn)
	{
	struct dax_device *dax_dev = stripe_dax_pgoff(ti, &pgoff);

	return dax_direct_access(dax_dev, pgoff, nr_pages, mode, kaddr, pfn);
	}

	static int stripe_dax_zero_page_range(struct dm_target *ti, pgoff_t pgoff,
	size_t nr_pages)
	{
	struct dax_device *dax_dev = stripe_dax_pgoff(ti, &pgoff);

	return dax_zero_page_range(dax_dev, pgoff, nr_pages);
	}

	static size_t stripe_dax_recovery_write(struct dm_target *ti, pgoff_t pgoff,
	void addr, size_t bytes, struct iov_iter i)
	{
	struct dax_device *dax_dev = stripe_dax_pgoff(ti, &pgoff);

	return dax_recovery_write(dax_dev, pgoff, addr, bytes, i);
	}

	#else
	#define stripe_dax_direct_access NULL
	#define stripe_dax_zero_page_range NULL
	#define stripe_dax_recovery_write NULL
	#endif

	/*
	* Stripe status:
	*
	* INFO
	* #stripes [stripe_name <stripe_name>] [group word count]
	* [error count 'A\|D' <error count 'A\|D'>]
	*
	* TABLE
	* #stripes [stripe chunk size]
	* [stripe_name physical_start <stripe_name physical_start>]
	*
	*/

	static void stripe_status(struct dm_target *ti, status_type_t type,
	unsigned int status_flags, char *result, unsigned int maxlen)
	{
	struct stripe_c sc = (struct stripe_c ) ti->private;
	unsigned int sz = 0;
	unsigned int i;

	switch (type) {
	case STATUSTYPE_INFO:
	DMEMIT("%d ", sc->stripes);
	for (i = 0; i < sc->stripes; i++) {
	DMEMIT("%s ", sc->stripe[i].dev->name);
	}
	DMEMIT("1 ");
	for (i = 0; i < sc->stripes; i++) {
	DMEMIT("%c", atomic_read(&(sc->stripe[i].error_count)) ?
	'D' : 'A');
	}
	break;

	case STATUSTYPE_TABLE:
	DMEMIT("%d %llu", sc->stripes,
	(unsigned long long)sc->chunk_size);
	for (i = 0; i < sc->stripes; i++)
	DMEMIT(" %s %llu", sc->stripe[i].dev->name,
	(unsigned long long)sc->stripe[i].physical_start);
	break;

	case STATUSTYPE_IMA:
	DMEMIT_TARGET_NAME_VERSION(ti->type);
	DMEMIT(",stripes=%d,chunk_size=%llu", sc->stripes,
	(unsigned long long)sc->chunk_size);

	for (i = 0; i < sc->stripes; i++) {
	DMEMIT(",stripe_%d_device_name=%s", i, sc->stripe[i].dev->name);
	DMEMIT(",stripe_%d_physical_start=%llu", i,
	(unsigned long long)sc->stripe[i].physical_start);
	DMEMIT(",stripe_%d_status=%c", i,
	atomic_read(&(sc->stripe[i].error_count)) ? 'D' : 'A');
	}
	DMEMIT(";");
	break;
	}
	}

	static int stripe_end_io(struct dm_target ti, struct bio bio,
	blk_status_t *error)
	{
	unsigned int i;
	char major_minor[16];
	struct stripe_c *sc = ti->private;

	if (!*error)
	return DM_ENDIO_DONE; /* I/O complete */

	if (bio->bi_opf & REQ_RAHEAD)
	return DM_ENDIO_DONE;

	if (*error == BLK_STS_NOTSUPP)
	return DM_ENDIO_DONE;

	memset(major_minor, 0, sizeof(major_minor));
	sprintf(major_minor, "%d:%d", MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)));

	/*
	* Test to see which stripe drive triggered the event
	* and increment error count for all stripes on that device.
	* If the error count for a given device exceeds the threshold
	* value we will no longer trigger any further events.
	*/
	for (i = 0; i < sc->stripes; i++)
	if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
	atomic_inc(&(sc->stripe[i].error_count));
	if (atomic_read(&(sc->stripe[i].error_count)) <
	DM_IO_ERROR_THRESHOLD)
	schedule_work(&sc->trigger_event);
	}

	return DM_ENDIO_DONE;
	}

	static int stripe_iterate_devices(struct dm_target *ti,
	iterate_devices_callout_fn fn, void *data)
	{
	struct stripe_c *sc = ti->private;
	int ret = 0;
	unsigned int i = 0;

	do {
	ret = fn(ti, sc->stripe[i].dev,
	sc->stripe[i].physical_start,
	sc->stripe_width, data);
	} while (!ret && ++i < sc->stripes);

	return ret;
	}

	static void stripe_io_hints(struct dm_target *ti,
	struct queue_limits *limits)
	{
	struct stripe_c *sc = ti->private;
	unsigned int chunk_size = sc->chunk_size << SECTOR_SHIFT;

	blk_limits_io_min(limits, chunk_size);
	blk_limits_io_opt(limits, chunk_size * sc->stripes);
	}

	static struct target_type stripe_target = {
	.name = "striped",
	.version = {1, 6, 0},
	.features = DM_TARGET_PASSES_INTEGRITY \| DM_TARGET_NOWAIT,
	.module = THIS_MODULE,
	.ctr = stripe_ctr,
	.dtr = stripe_dtr,
	.map = stripe_map,
	.end_io = stripe_end_io,
	.status = stripe_status,
	.iterate_devices = stripe_iterate_devices,
	.io_hints = stripe_io_hints,
	.direct_access = stripe_dax_direct_access,
	.dax_zero_page_range = stripe_dax_zero_page_range,
	.dax_recovery_write = stripe_dax_recovery_write,
	};

	int __init dm_stripe_init(void)
	{
	int r;

	r = dm_register_target(&stripe_target);
	if (r < 0)
	DMWARN("target registration failed");

	return r;
	}

	void dm_stripe_exit(void)
	{
	dm_unregister_target(&stripe_target);
	}