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

  #include <linux/device-mapper.h>

  
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/blkdev.h>
  #include <linux/bio.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;
  	sector_t stripes_mask;

  
  	/* The size of this target / num. stripes */
  	sector_t stripe_width;
  
  	/* stripe chunk size */
  	uint32_t chunk_shift;
  	sector_t chunk_mask;

  	/* Needed for handling events */
  	struct dm_target *ti;
  
  	/* Work struct used for triggering events*/
  	struct work_struct kstriped_ws;

  	struct stripe stripe[0];
  };

  static struct workqueue_struct *kstriped;
  
  /*
   * 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, kstriped_ws);
  
  	dm_table_event(sc->ti->table);
  
  }

  static inline struct stripe_c *alloc_context(unsigned int stripes)
  {
  	size_t len;

  	if (dm_array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
  			     stripes))

  		return NULL;
  
  	len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);
  
  	return kmalloc(len, GFP_KERNEL);
  }
  
  /*
   * 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;

  	if (sscanf(argv[1], "%llu", &start) != 1)

  		return -EINVAL;

  	if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),

  			  &sc->stripe[stripe].dev))
  		return -ENXIO;
  
  	sc->stripe[stripe].physical_start = start;

  	return 0;
  }
  
  /*
   * Construct a striped mapping.
   * <number of stripes> <chunk size (2^^n)> [<dev_path> <offset>]+
   */
  static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
  {
  	struct stripe_c *sc;
  	sector_t width;
  	uint32_t stripes;
  	uint32_t chunk_size;
  	char *end;
  	int r;
  	unsigned int i;
  
  	if (argc < 2) {

  		ti->error = "Not enough arguments";

  		return -EINVAL;
  	}
  
  	stripes = simple_strtoul(argv[0], &end, 10);

  	if (!stripes || *end) {

  		ti->error = "Invalid stripe count";

  		return -EINVAL;
  	}
  
  	chunk_size = simple_strtoul(argv[1], &end, 10);
  	if (*end) {

  		ti->error = "Invalid chunk_size";

  		return -EINVAL;
  	}
  
  	/*
  	 * chunk_size is a power of two
  	 */

  	if (!is_power_of_2(chunk_size) ||

  	    (chunk_size < (PAGE_SIZE >> SECTOR_SHIFT))) {

  		ti->error = "Invalid chunk size";

  		return -EINVAL;
  	}

  	if (ti->len & (chunk_size - 1)) {

  		ti->error = "Target length not divisible by "

  		    "chunk size";
  		return -EINVAL;
  	}

  	width = ti->len;
  	if (sector_div(width, stripes)) {

  		ti->error = "Target length not divisible by "

  		    "number of stripes";
  		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 = alloc_context(stripes);
  	if (!sc) {

  		ti->error = "Memory allocation for striped context "

  		    "failed";
  		return -ENOMEM;
  	}

  	INIT_WORK(&sc->kstriped_ws, 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) - 1;
  		sc->stripes_mask = ((sector_t) stripes) - 1;
  	}

  	ti->split_io = chunk_size;

  	ti->num_flush_requests = stripes;

  	ti->num_discard_requests = stripes;

  	sc->chunk_shift = ffs(chunk_size) - 1;

  	sc->chunk_mask = ((sector_t) chunk_size) - 1;

  
  	/*
  	 * 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_workqueue(kstriped);

  	kfree(sc);
  }

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

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

  	*result = (chunk << sc->chunk_shift) | (offset & sc->chunk_mask);
  }

  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;
  	*result &= ~sc->chunk_mask;			/* round down */
  	if (target_stripe < stripe)
  		*result += sc->chunk_mask + 1;		/* next chunk */
  }
  
  static int stripe_map_discard(struct stripe_c *sc, struct bio *bio,
  			      uint32_t target_stripe)
  {
  	sector_t begin, end;
  
  	stripe_map_range_sector(sc, bio->bi_sector, target_stripe, &begin);
  	stripe_map_range_sector(sc, bio->bi_sector + bio_sectors(bio),
  				target_stripe, &end);
  	if (begin < end) {
  		bio->bi_bdev = sc->stripe[target_stripe].dev->bdev;
  		bio->bi_sector = begin + sc->stripe[target_stripe].physical_start;
  		bio->bi_size = to_bytes(end - begin);
  		return DM_MAPIO_REMAPPED;
  	} else {
  		/* The range doesn't map to the target stripe */
  		bio_endio(bio, 0);
  		return DM_MAPIO_SUBMITTED;
  	}
  }

  static int stripe_map(struct dm_target *ti, struct bio *bio,
  		      union map_info *map_context)
  {

  	struct stripe_c *sc = ti->private;

  	uint32_t stripe;

  	unsigned target_request_nr;

  	if (unlikely(bio_empty_barrier(bio))) {

  		target_request_nr = map_context->target_request_nr;
  		BUG_ON(target_request_nr >= sc->stripes);
  		bio->bi_bdev = sc->stripe[target_request_nr].dev->bdev;

  		return DM_MAPIO_REMAPPED;
  	}

  	if (unlikely(bio->bi_rw & REQ_DISCARD)) {
  		target_request_nr = map_context->target_request_nr;
  		BUG_ON(target_request_nr >= sc->stripes);
  		return stripe_map_discard(sc, bio, target_request_nr);
  	}

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

  	bio->bi_sector += sc->stripe[stripe].physical_start;

  	bio->bi_bdev = sc->stripe[stripe].dev->bdev;

  	return DM_MAPIO_REMAPPED;

  }

  /*
   * 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 int stripe_status(struct dm_target *ti,
  			 status_type_t type, char *result, unsigned int maxlen)
  {
  	struct stripe_c *sc = (struct stripe_c *) ti->private;

  	char buffer[sc->stripes + 1];

  	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);
  			buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
  				'D' : 'A';
  		}
  		buffer[i] = '\0';
  		DMEMIT("1 %s", buffer);

  		break;
  
  	case STATUSTYPE_TABLE:

  		DMEMIT("%d %llu", sc->stripes,
  			(unsigned long long)sc->chunk_mask + 1);

  		for (i = 0; i < sc->stripes; i++)

  			DMEMIT(" %s %llu", sc->stripe[i].dev->name,
  			    (unsigned long long)sc->stripe[i].physical_start);

  		break;
  	}
  	return 0;
  }

  static int stripe_end_io(struct dm_target *ti, struct bio *bio,
  			 int error, union map_info *map_context)
  {
  	unsigned i;
  	char major_minor[16];
  	struct stripe_c *sc = ti->private;
  
  	if (!error)
  		return 0; /* I/O complete */

  	if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))

  		return error;
  
  	if (error == -EOPNOTSUPP)
  		return error;
  
  	memset(major_minor, 0, sizeof(major_minor));
  	sprintf(major_minor, "%d:%d",

  		MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
  		MINOR(disk_devt(bio->bi_bdev->bd_disk)));

  
  	/*
  	 * 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)
  				queue_work(kstriped, &sc->kstriped_ws);
  		}
  
  	return error;
  }

  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 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 chunk_size = (sc->chunk_mask + 1) << 9;
  
  	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, 3, 0},

  	.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,

  };
  
  int __init dm_stripe_init(void)
  {
  	int r;
  
  	r = dm_register_target(&stripe_target);

  	if (r < 0) {

  		DMWARN("target registration failed");

  		return r;
  	}

  	kstriped = create_singlethread_workqueue("kstriped");
  	if (!kstriped) {
  		DMERR("failed to create workqueue kstriped");
  		dm_unregister_target(&stripe_target);
  		return -ENOMEM;
  	}

  	return r;
  }
  
  void dm_stripe_exit(void)
  {

  	dm_unregister_target(&stripe_target);

  	destroy_workqueue(kstriped);

  	return;
  }