/*

   * Copyright (C) 2001-2002 Sistina Software (UK) Limited.

   * Copyright (C) 2006-2008 Red Hat GmbH

   *
   * This file is released under the GPL.
   */

  #include "dm-exception-store.h"

  #include <linux/ctype.h>

  #include <linux/mm.h>
  #include <linux/pagemap.h>
  #include <linux/vmalloc.h>

  #include <linux/module.h>

  #include <linux/slab.h>

  #define DM_MSG_PREFIX "snapshot exception stores"

  static LIST_HEAD(_exception_store_types);
  static DEFINE_SPINLOCK(_lock);
  
  static struct dm_exception_store_type *__find_exception_store_type(const char *name)
  {
  	struct dm_exception_store_type *type;
  
  	list_for_each_entry(type, &_exception_store_types, list)
  		if (!strcmp(name, type->name))
  			return type;
  
  	return NULL;
  }
  
  static struct dm_exception_store_type *_get_exception_store_type(const char *name)
  {
  	struct dm_exception_store_type *type;
  
  	spin_lock(&_lock);
  
  	type = __find_exception_store_type(name);
  
  	if (type && !try_module_get(type->module))
  		type = NULL;
  
  	spin_unlock(&_lock);
  
  	return type;
  }
  
  /*
   * get_type
   * @type_name
   *
   * Attempt to retrieve the dm_exception_store_type by name.  If not already
   * available, attempt to load the appropriate module.
   *
   * Exstore modules are named "dm-exstore-" followed by the 'type_name'.
   * Modules may contain multiple types.
   * This function will first try the module "dm-exstore-<type_name>",
   * then truncate 'type_name' on the last '-' and try again.
   *
   * For example, if type_name was "clustered-shared", it would search
   * 'dm-exstore-clustered-shared' then 'dm-exstore-clustered'.
   *
   * 'dm-exception-store-<type_name>' is too long of a name in my
   * opinion, which is why I've chosen to have the files
   * containing exception store implementations be 'dm-exstore-<type_name>'.
   * If you want your module to be autoloaded, you will follow this
   * naming convention.
   *
   * Returns: dm_exception_store_type* on success, NULL on failure
   */
  static struct dm_exception_store_type *get_type(const char *type_name)
  {
  	char *p, *type_name_dup;
  	struct dm_exception_store_type *type;
  
  	type = _get_exception_store_type(type_name);
  	if (type)
  		return type;
  
  	type_name_dup = kstrdup(type_name, GFP_KERNEL);
  	if (!type_name_dup) {
  		DMERR("No memory left to attempt load for \"%s\"", type_name);
  		return NULL;
  	}
  
  	while (request_module("dm-exstore-%s", type_name_dup) ||
  	       !(type = _get_exception_store_type(type_name))) {
  		p = strrchr(type_name_dup, '-');
  		if (!p)
  			break;
  		p[0] = '\0';
  	}
  
  	if (!type)
  		DMWARN("Module for exstore type \"%s\" not found.", type_name);
  
  	kfree(type_name_dup);
  
  	return type;
  }
  
  static void put_type(struct dm_exception_store_type *type)
  {
  	spin_lock(&_lock);
  	module_put(type->module);
  	spin_unlock(&_lock);
  }
  
  int dm_exception_store_type_register(struct dm_exception_store_type *type)
  {
  	int r = 0;
  
  	spin_lock(&_lock);
  	if (!__find_exception_store_type(type->name))
  		list_add(&type->list, &_exception_store_types);
  	else
  		r = -EEXIST;
  	spin_unlock(&_lock);
  
  	return r;
  }
  EXPORT_SYMBOL(dm_exception_store_type_register);
  
  int dm_exception_store_type_unregister(struct dm_exception_store_type *type)
  {
  	spin_lock(&_lock);
  
  	if (!__find_exception_store_type(type->name)) {
  		spin_unlock(&_lock);
  		return -EINVAL;
  	}
  
  	list_del(&type->list);
  
  	spin_unlock(&_lock);
  
  	return 0;
  }
  EXPORT_SYMBOL(dm_exception_store_type_unregister);

  static int set_chunk_size(struct dm_exception_store *store,
  			  const char *chunk_size_arg, char **error)
  {

  	unsigned chunk_size;

  	if (kstrtouint(chunk_size_arg, 10, &chunk_size)) {

  		*error = "Invalid chunk size";
  		return -EINVAL;
  	}

  	if (!chunk_size) {

  		store->chunk_size = store->chunk_mask = store->chunk_shift = 0;
  		return 0;
  	}

  	return dm_exception_store_set_chunk_size(store, chunk_size, error);

  }
  
  int dm_exception_store_set_chunk_size(struct dm_exception_store *store,

  				      unsigned chunk_size,

  				      char **error)
  {

  	/* Check chunk_size is a power of 2 */

  	if (!is_power_of_2(chunk_size)) {

  		*error = "Chunk size is not a power of 2";
  		return -EINVAL;
  	}
  
  	/* Validate the chunk size against the device block size */

  	if (chunk_size %

  	    (bdev_logical_block_size(dm_snap_cow(store->snap)->bdev) >> 9) ||
  	    chunk_size %
  	    (bdev_logical_block_size(dm_snap_origin(store->snap)->bdev) >> 9)) {

  		*error = "Chunk size is not a multiple of device blocksize";
  		return -EINVAL;
  	}

  	if (chunk_size > INT_MAX >> SECTOR_SHIFT) {

  		*error = "Chunk size is too high";
  		return -EINVAL;
  	}

  	store->chunk_size = chunk_size;
  	store->chunk_mask = chunk_size - 1;

  	store->chunk_shift = __ffs(chunk_size);

  
  	return 0;
  }
  
  int dm_exception_store_create(struct dm_target *ti, int argc, char **argv,

  			      struct dm_snapshot *snap,

  			      unsigned *args_used,

  			      struct dm_exception_store **store)
  {
  	int r = 0;

  	struct dm_exception_store_type *type = NULL;

  	struct dm_exception_store *tmp_store;

  	char persistent;

  	if (argc < 2) {

  		ti->error = "Insufficient exception store arguments";
  		return -EINVAL;
  	}

  	tmp_store = kzalloc(sizeof(*tmp_store), GFP_KERNEL);

  	if (!tmp_store) {
  		ti->error = "Exception store allocation failed";

  		return -ENOMEM;

  	}

  	persistent = toupper(*argv[0]);

  	if (persistent == 'P')
  		type = get_type("P");
  	else if (persistent == 'N')
  		type = get_type("N");
  	else {

  		ti->error = "Exception store type is not P or N";

  		r = -EINVAL;
  		goto bad_type;

  	}

  	if (!type) {
  		ti->error = "Exception store type not recognised";
  		r = -EINVAL;
  		goto bad_type;
  	}

  	tmp_store->type = type;

  	tmp_store->snap = snap;

  	r = set_chunk_size(tmp_store, argv[1], &ti->error);

  	if (r)

  		goto bad;

  	r = type->ctr(tmp_store, (strlen(argv[0]) > 1 ? &argv[0][1] : NULL));

  	if (r) {

  		ti->error = "Exception store type constructor failed";

  		goto bad;

  	}

  	*args_used = 2;

  	*store = tmp_store;
  	return 0;

  bad:

  	put_type(type);
  bad_type:
  	kfree(tmp_store);
  	return r;

  }
  EXPORT_SYMBOL(dm_exception_store_create);
  
  void dm_exception_store_destroy(struct dm_exception_store *store)
  {
  	store->type->dtr(store);
  	put_type(store->type);
  	kfree(store);
  }
  EXPORT_SYMBOL(dm_exception_store_destroy);

  int dm_exception_store_init(void)

  {
  	int r;

  	r = dm_transient_snapshot_init();
  	if (r) {
  		DMERR("Unable to register transient exception store type.");
  		goto transient_fail;

  	}

  	r = dm_persistent_snapshot_init();
  	if (r) {
  		DMERR("Unable to register persistent exception store type");
  		goto persistent_fail;

  	}
  
  	return 0;

  persistent_fail:

  	dm_transient_snapshot_exit();

  transient_fail:
  	return r;

  }

  void dm_exception_store_exit(void)

  {

  	dm_persistent_snapshot_exit();
  	dm_transient_snapshot_exit();

  }