text: /*
   * 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 trigger_event;
  
  	struct stripe stripe[0];
  };
  
  /*
   * 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);
  }
  
  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;
  	char dummy;
  
  	if (sscanf(argv[1], "%llu%c", &start, &dummy) != 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->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) - 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_work_sync(&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 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 (bio->bi_rw & REQ_FLUSH) {
  		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)
  				schedule_work(&sc->trigger_event);
  		}
  
  	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 int stripe_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
  			struct bio_vec *biovec, int max_size)
  {
  	struct stripe_c *sc = ti->private;
  	sector_t bvm_sector = bvm->bi_sector;
  	uint32_t stripe;
  	struct request_queue *q;
  
  	stripe_map_sector(sc, bvm_sector, &stripe, &bvm_sector);
  
  	q = bdev_get_queue(sc->stripe[stripe].dev->bdev);
  	if (!q->merge_bvec_fn)
  		return max_size;
  
  	bvm->bi_bdev = sc->stripe[stripe].dev->bdev;
  	bvm->bi_sector = sc->stripe[stripe].physical_start + bvm_sector;
  
  	return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
  }
  
  static struct target_type stripe_target = {
  	.name   = "striped",
  	.version = {1, 4, 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,
  	.merge  = stripe_merge,
  };
  
  int __init dm_stripe_init(void)
  {
  	int r;
  
  	r = dm_register_target(&stripe_target);
  	if (r < 0) {
  		DMWARN("target registration failed");
  		return r;
  	}
  
  	return r;
  }
  
  void dm_stripe_exit(void)
  {
  	dm_unregister_target(&stripe_target);
  }
  